Merge PR #86: feat: weather, PV forecast and IMGW warnings

# Conflicts:
#	backend/README.md
#	backend/src/main/java/home/backend/Backend.java
#	backend/src/main/java/home/backend/adapters/http/ApiServer.java
#	backend/src/main/java/home/backend/adapters/influx/InfluxHistoryRepository.java
#	backend/src/test/java/home/backend/adapters/http/ApiServerTest.java
#	frontend/README.md

.claude/skills/close-milestone/SKILL.md

@@ -0,0 +1,19 @@
+---
+name: close-milestone
+description: Close the current milestone in docs/roadmap.md, remove its working notes and start the next one. Use when every item of the current milestone is done.
+---
+
+# Close milestone
+
+1. Read `docs/roadmap.md`. Every item of "Current" is checked and its "Done when" holds.
+   Anything you cannot verify yourself (e.g. "a week on the Pi") you ask the user about.
+   Stop and report if something is open.
+2. Branch `docs/close-<milestone>` (e.g. `docs/close-m1`).
+3. Under "Done", add one line: `- M<n> <name> · <tag or commit>: <what it delivered>`.
+   Remove the "Current" checklist and any placeholder line.
+4. Remove the milestone's working notes: fixed defects (D…), consumed feasibility checks,
+   notes that served only this milestone. Verified knowledge moves first: controller facts
+   to `docs/frisko/`, scope or architecture to `docs/spec.md`, decisions to a new ADR.
+5. Make the next row of "Next" the new "Current": a checklist of PR-sized items in build
+   order, keeping its "Done when". Ask the user when the split is not obvious.
+6. `scripts/check.sh` (roadmap ≤ 80 lines), then `/ship`.

.claude/skills/ship/SKILL.md

@@ -0,0 +1,31 @@
+---
+name: ship
+description: Take the current topic branch to master through a Gitea PR with green CI, then optionally release it and update the Pi. Use when a change is ready to merge or release.
+---
+
+# Ship
+
+Repo rules: `CONTRIBUTING.md`. Gitea: https://git.mariuszpacek.pl/mariusz.pacek/home-pump
+(no API token here; reads need none).
+
+1. On a topic branch (`feat/`, `fix/`, `docs/`, `chore/`, `refactor/`), clean tree, commits
+   in Conventional Commits. Run `scripts/check.sh`.
+2. `git push -u origin <branch>`; CI runs on every pushed branch.
+3. Open the PR by push (Gitea AGit), title in Conventional Commits, description says why:
+   `git push origin HEAD:refs/for/master -o topic=<branch> -o title="…" -o description="…"`.
+   The description is one line (push options cannot hold newlines). After later fixes push
+   both the branch and `refs/for/master` with the same topic, so CI and the PR both update.
+   If that is refused, give the user the compare link `…/compare/master...<branch>`.
+4. Wait for CI on the head commit, polling every 30 s:
+   `curl -s …/api/v1/repos/mariusz.pacek/home-pump/commits/<sha>/status` → `state`.
+   On `failure`, read the run under `…/actions`, fix, push again. Never merge red.
+5. Merge only if the user asked for it in this task:
+   `git switch master && git pull --ff-only && git merge --no-ff <branch> -m "Merge PR #N: <title>"`,
+   then `git push origin master` and delete the branch locally and on origin. Confirm CI is
+   green on master. Gitea does not close an AGit PR merged by hand: ask the user to close it.
+6. Release and update only with the user's explicit approval for this one:
+   `scripts/release.sh vMAJOR.MINOR.PATCH` (patch for fixes, minor for features) tags master;
+   wait until the Release run under `…/actions` is green (it publishes the images). Then on the
+   Pi (`ssh <host>`, an alias while D7 is open): `cd /home/pi/home-pump && ./update.sh <version>`,
+   watch `journalctl -t home-pump-gateway -f` and Grafana for one polling cycle (300 s) and
+   report what you saw. Backend and frontend reach Kraków through Arcane (homelab-compose).

.drone.yml

@@ -1,18 +0,0 @@
-kind: pipeline
-type: docker
-name: default
-
-steps:
-- name: test
-  image: maven:3-jdk-11
-  commands:
-  - mvn install -DskipTests=true -Dmaven.javadoc.skip=true -B -V
-  - mvn test -B
-- name: docker
-  image: plugins/docker
-  settings:
-    repo: registry.mariuszpacek.pl/home-pump
-    tags: latest
-  when:
-    branch:
-      - master

.gitea/workflows/ci.yml

@@ -4,29 +4,27 @@ on:
   push:
     branches:
       - "**"
-  pull_request:
-    branches:
-      - "**"
 
 jobs:
-  backend:
-    name: Backend tests (Maven / Java 21)
+  check:
+    name: Check (gateway, backend, frontend)
     runs-on: ubuntu-latest
 
     steps:
       - name: Checkout
         uses: actions/checkout@v4
-
-      - name: Show runner info
-        run: |
-          echo "Runner name: ${{ runner.name }}"
-          echo "Runner labels: ${{ toJSON(runner.labels) }}"
-
-      - name: Set up Java 21 + Maven
+      - name: Set up Java 21
         uses: actions/setup-java@v5
         with:
           distribution: temurin
-          java-version: "21"
-          cache: maven
-      - name: Run Maven tests (parallel)
-        run: mvn -B -T 1C test
+          java-version: '21'
+      - name: Set up Maven
+        uses: stCarolas/setup-maven@v5
+        with:
+          maven-version: 3.9.6
+      - name: Set up Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: '24'
+      - name: Check
+        run: scripts/check.sh

.gitea/workflows/release.yml

@@ -0,0 +1,59 @@
+# A pushed tag vMAJOR.MINOR.PATCH (scripts/release.sh) publishes the three images under that name
+# and as latest. The Pi pulls the gateway with gateway/update.sh; Kraków runs backend and frontend.
+name: Release
+
+on:
+  push:
+    tags:
+      - "v*.*.*"
+
+env:
+  REGISTRY: git.mariuszpacek.pl
+  IMAGES: git.mariuszpacek.pl/mariusz.pacek/home-pump
+
+jobs:
+  images:
+    name: Images
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      # As in homelab-upgrade: the job talks to VM103's daemon through the mounted socket.
+      - name: Docker CLI
+        run: command -v docker >/dev/null || (apt-get update -qq && apt-get install -y -qq docker.io >/dev/null); docker version --format '{{.Client.Version}} -> {{.Server.Version}}'
+      - name: Set up Buildx
+        uses: docker/setup-buildx-action@v3
+      - name: Log in to the Gitea registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ gitea.repository_owner }}
+          # The owner's token with package write access (the secret homelab-upgrade uses too).
+          password: ${{ secrets.REGISTRY_TOKEN }}
+      # The Pi is arm64. Each Dockerfile builds on the runner's platform and only copies into the
+      # final stage, so the arm64 image needs no emulation.
+      - name: Gateway
+        uses: docker/build-push-action@v6
+        with:
+          context: gateway
+          build-args: VERSION=${{ gitea.ref_name }}
+          platforms: linux/arm64,linux/amd64
+          push: true
+          tags: ${{ env.IMAGES }}-gateway:${{ gitea.ref_name }},${{ env.IMAGES }}-gateway:latest
+      - name: Backend
+        uses: docker/build-push-action@v6
+        with:
+          context: backend
+          build-args: VERSION=${{ gitea.ref_name }}
+          platforms: linux/amd64
+          push: true
+          tags: ${{ env.IMAGES }}-backend:${{ gitea.ref_name }},${{ env.IMAGES }}-backend:latest
+      - name: Frontend
+        uses: docker/build-push-action@v6
+        with:
+          context: frontend
+          build-args: VERSION=${{ gitea.ref_name }}
+          platforms: linux/amd64
+          push: true
+          tags: ${{ env.IMAGES }}-frontend:${{ gitea.ref_name }},${{ env.IMAGES }}-frontend:latest

.githooks/pre-push

@@ -0,0 +1,3 @@
+#!/usr/bin/env bash
+# Enabled once per clone: git config core.hooksPath .githooks
+exec "$(git rev-parse --show-toplevel)/scripts/check.sh"

.github/copilot-instructions.md

@@ -1,81 +0,0 @@
-# Copilot instructions for `home-pump`
-
-## Build and test commands
-
-### Backend (repo root)
-
-- `mvn clean package` builds the Spring Boot jar at `target/home-pump-1.0.0.jar`.
-- `mvn test` runs the current backend test suite. CI (`.drone.yml`) uses plain `mvn test`.
-- `mvn -Dtest=ControlLoopUseCaseTests test` runs a single unit test class.
-- `mvn -Dtest=ControlLoopUseCaseTests#shouldApplyCwuPriorityBeforeSendingCommands test` runs a single JUnit test method.
-- `mvn -Dtest=ControlApiContractIntegrationTests test` runs one tagged integration test class.
-- `java -jar target/home-pump-1.0.0.jar` starts the packaged backend.
-
-### Frontend (`frontend/`)
-
-- `npm install`
-- `npm run dev`
-- `npm run build`
-- `npm run build:ssr`
-
-## High-level architecture
-
-- The backend is a Spring Boot application (`HomePumpApplication`) with most runtime behavior driven by `ScheduledTasks`. The scheduler runs five separate loops: the control loop, live telemetry polling, legacy Influx publishing, schedule application, and health-based shutdown/restart.
-
-- Configuration is split across two sources and both matter:
-  - `src/main/resources/application.yml` contains Spring-managed control settings, schedule/poll intervals, SQLite path, heating-circuit strategy definitions, and optional Modbus command register overrides.
-  - `src/main/resources/registryMapping.json` is loaded from the classpath by `JsonFileBasedConfiguration` and carries device address/port, retry settings, `useMock`, live polling window, Influx connection info, and the register metadata used by the Modbus layer. `registryMapping.example.json` is only a sample; the loader looks for `registryMapping.json`.
-
-- The backend is organized as a ports-and-adapters style application, but it still contains legacy integration packages:
-  - `domain`: control models, temperature strategies, and rules like CWU priority, anti-freeze, disinfection, and pump runtime protection.
-  - `application`: use cases and output ports. `ControlLoopUseCase` decides commands from live readings; `ManualControlUseCase` owns operator-controlled state such as AUTO/MANUAL, ECO/COMFORT, SUMMER/WINTER, per-circuit override mode, and the weekly schedule.
-  - `infrastructure`: REST controllers, Modbus/Influx adapters, Frisko services, scheduler wiring, and SQLite persistence.
-  - `configuration`, `modbus`, `influxdb`, and `health` still contain important lower-level classes used by the Spring wiring.
-
-- `ManualControlUseCase` is the source of truth for mutable control state. It persists state through `SqliteControlStateStore` to `data/control-state.db`, including operating mode, season/program mode, circuit overrides, control policy settings, and the program schedule.
-
-- The Modbus side has two distinct responsibilities:
-  - `ModbusDeviceAdapter` is the bridge used by the control loop for current readings and write commands.
-  - `ModbusPollingService` builds the rolling telemetry/history used by `/api/telemetry` and contributes the Modbus component state to `/health`.
-
-- Frisko support is driven by `frisko/mr208_m3p.csv`. `FriskoRegisterCatalogService` categorizes symbols from that CSV, and `FriskoRuntimeService` exposes runtime read/write, controller time sync, alarms, schedules, and thresholds through `/api/v1/frisko/*`.
-
-- There are currently two Influx write paths:
-  - `ControlLoopUseCase` publishes through `MetricsPublisher`, which is wired to `InfluxMetricsAdapter`.
-  - `ScheduledTasks.sendLegacyInfluxMetrics()` still runs `InfluxMetricModbusSender`.
-  Any Influx-related change needs to account for both paths.
-
-- The frontend is a Vite + React + TypeScript dashboard under `frontend/`. `App.tsx` composes feature panels for health, control, telemetry, Frisko analysis/runtime, thresholds, schedule editing, and the schematic view. API access lives in `services/*`, React Query polling/mutations live in `hooks/*`, and `lib/http.ts` centralizes Axios setup plus normalized API errors.
-
-- Workspace-level browser automation is configured through `.vscode/mcp.json` with the Playwright MCP server. Prefer that path for UI verification when you need to inspect the dashboard behavior end-to-end.
-
-## Key conventions
-
-- Treat circuit IDs as uppercase domain identifiers (`CO1`, `CO2`, `CO3`, `CWU`). The backend normalizes them to uppercase in multiple places (`ManualControlUseCase`, `InMemoryHeatingCircuitRepository`), and frontend services/UI use the same IDs.
-
-- Heating-circuit behavior is declarative in `application.yml` under `app.heating.circuits`. `InMemoryHeatingCircuitRepository` turns each definition into a `HeatingCircuit` with either a weather-compensated or constant strategy, and wraps it in `ClampedTemperatureStrategy` when both min/max temperatures are provided.
-
-- Real hardware writes are disabled by default. `ModbusDeviceAdapter.applyCommands()` only writes when `app.modbus.commands.write-enabled=true`. If you change control flows or manual actions, remember the UI can still update persisted logical state even when physical writes are skipped.
-
-- Command-register mapping is symbol-driven, not just hard-coded register-driven. `FriskoCircuitRegisterMappingService` builds default mappings from the Frisko CSV, preferring `WY_*` symbols and falling back to `TEST_*`, with `application.yml` only overriding specific circuit registers when needed.
-
-- Telemetry and device-state extraction are also symbol/description driven. `ModbusDeviceAdapter` and `ModbusPollingService` search registry descriptions using Frisko symbols first and older human-readable descriptions as fallbacks. When adding a new signal, update the matching candidates and the related tests instead of relying on a single label spelling.
-
-- `SystemReadings` may contain `NaN` internally for missing numeric values. API-facing controllers such as `SystemController` sanitize those values to `null` before returning JSON. Keep that distinction when extending the model or frontend types.
-
-- Local backend development can avoid a real device by setting top-level `useMock: true` in `registryMapping.json`. `AppConfig` swaps the Modbus repository to `MockRepository` in that mode.
-
-- The REST API is intentionally split by bounded context:
-  - legacy monitoring endpoints: `/health`, `/api/telemetry`
-  - control endpoints: `/api/v1/control/*`
-  - current system snapshot endpoints: `/api/v1/system/*`
-  - Frisko analysis/runtime endpoints: `/api/v1/frisko/*`
-  Frontend service modules mirror these base paths; follow that pattern instead of calling Axios directly from panels.
-
-- Frontend polling and error handling live in hooks, not components. Typical pattern: `services/*` perform the request, `hooks/*` wrap them with React Query and toast handling, and panels stay mostly presentational.
-
-- The telemetry UI can show mock data even when the backend telemetry endpoint is unavailable. `frontend/src/services/telemetryService.ts` falls back to `mocks/telemetryMock.ts` after a failed `/api/telemetry` request, so do not treat rendered charts as proof that live telemetry is healthy.
-
-- Integration tests are tagged with `@Tag("integration")`, but the current repo and CI still run plain `mvn test`. Do not assume tagged tests are separated into a dedicated Maven lifecycle unless you also wire Surefire/Failsafe to do it.
-
-- Treat Java 21 as the backend build target. The active `maven-compiler-plugin` is set to `release 21`, even though some legacy files in the repo still reference older Java versions.

.gitignore

@@ -18,7 +18,7 @@ target/
 /.idea/
 /.vscode/
 /.java-version
-/dependency-reduced-pom.xml
+dependency-reduced-pom.xml
 /workspace.code-workspace
 /target/
 
@@ -26,7 +26,6 @@ target/
 /node_modules/
 /frontend/node_modules/
 /frontend/dist/
-/frontend/.env*
 /dist/
 
 # Vite
@@ -56,3 +55,6 @@ coverage/
 /apk/
 /old/
 /old_backup/
+
+# Agent worktrees
+/.claude/worktrees/

CLAUDE.md

@@ -0,0 +1,16 @@
+Backend for controlling the heat pump in Krosno (Frisko controller, Modbus TCP) from a phone.
+
+@CONTRIBUTING.md
+
+## For agents
+
+- Start from `docs/roadmap.md`; stay within the current milestone unless asked.
+- Read `docs/spec.md` and a decision in `docs/decisions/` only when the task touches it.
+- Production: `pi@raspberrypi.local`, the gateway in Docker (`gateway/compose.yaml`; until it is
+  installed, the old `home-pump.service`). Read-only inspection is fine; installing, updating,
+  restarting or changing files on the Pi needs explicit approval each time.
+- The Pi also runs `rpi-measurements.service` (house meter and BME280 into Influx); do not break
+  it. It moves into the gateway in M1; never run both against the meter at once. Do not upgrade
+  or reinstall the Pi's OS.
+- Never write to the controller `192.168.0.150` and never to the `Dom_Pompa` database.
+- Ask before force-pushing or rewriting history on Gitea.

CONTRIBUTING.md

@@ -0,0 +1,62 @@
+# Repository rules
+
+What we build: [docs/spec.md](docs/spec.md). Plan: [docs/roadmap.md](docs/roadmap.md).
+Reasons: [docs/decisions/](docs/decisions/).
+
+## Branches and pull requests
+
+- `master` is always deployable and matches what runs on the Pi.
+- Every change goes through a pull request on Gitea; no direct commits to `master`.
+- Branch names: `feat/…`, `fix/…`, `docs/…`, `chore/…`, `refactor/…`.
+- One topic per PR, small enough to review in one sitting. Merge only with green CI.
+- `archive/spring-boot-attempt` is reference only. Never merge it.
+
+## Commits
+
+- English, Conventional Commits: `fix(health): restart without /health polling`.
+- Imperative subject ≤ 72 characters; the body says why when it is not obvious.
+- Each commit builds and passes tests.
+
+## Code
+
+- Three parts, each with its `Dockerfile` and `compose.yaml` (ADR-010): `gateway/` and `backend/`
+  in Java 21 with Maven and no framework (ADR-001), `frontend/` in React and TypeScript (ADR-008).
+- `scripts/check.sh` is the gate: doc limits, secret scan, build and tests. CI runs it, and so
+  does the pre-push hook once enabled with `git config core.hooksPath .githooks`.
+- Readable first: small classes and methods, names from the domain, comments only for the why.
+- No dead code, no unused config, no duplicated logic, no speculative abstractions.
+- Every behaviour change has a test. Modbus is tested against `MockModbusServer` only.
+
+## Safety
+
+- Tests and local runs never use the real controller or the `Dom_Pompa` database.
+- A register is written only if it is on the allowlist (min, max, step) and verified in
+  `docs/frisko/`.
+- Changes to how or when we write to the controller need a test of the failure case.
+
+## Knowledge and docs
+
+Docs are written so an agent needs little context: read only what the task touches.
+
+| File | Limit | Changes |
+|---|---|---|
+| `CLAUDE.md` | 40 lines | rarely |
+| `docs/spec.md` | 120 lines | when scope or architecture changes |
+| `docs/roadmap.md` | 80 lines | every milestone |
+| `docs/decisions/NNN-*.md` | 40 lines | never after acceptance; supersede with a new ADR |
+| `docs/frisko/<topic>.md` | 120 lines | when knowledge is verified |
+| `<package>/CLAUDE.md` | 30 lines | rules of that layer |
+| `research/<source>/` | none | raw vendor material, kept as found; read only on demand |
+
+- Limits are checked by `scripts/check.sh`.
+- No status, audit or log documents: the state is git history and the roadmap.
+- Closing a milestone compresses it to one line in the roadmap and removes its working notes.
+- English everywhere; the UI is Polish.
+
+## Configuration, secrets, releases
+
+- No secrets in git. Production config lives on the Pi and next to the Kraków stacks, outside
+  the images.
+- Release only from `master` with `scripts/release.sh vMAJOR.MINOR.PATCH`: it tags master and
+  CI publishes the three images. On the Pi `./update.sh <version>` goes back if it is unhealthy.
+- After an update, watch the journal and Grafana for at least one polling cycle.

Dockerfile

@@ -1,4 +0,0 @@
-FROM amazoncorretto:11.0.17
-COPY target/test*.jar app/home-pump.jar
-
-CMD ["java", "-jar", "app/home-pump.jar"]

README.md

@@ -1,200 +1,25 @@
-# Home Pump Monitor
+# home-pump
 
-A Java application that reads data from a heat pump via Modbus TCP and sends metrics to InfluxDB.
+Heat pump (Frisko RX910-SE21) and home energy for the house in Krosno, from a phone.
 
-## Features
+- What we build: [docs/spec.md](docs/spec.md)
+- Plan and current milestone: [docs/roadmap.md](docs/roadmap.md)
+- Rules for changes: [CONTRIBUTING.md](CONTRIBUTING.md)
+- Controller knowledge: [docs/frisko/](docs/frisko/rx910-se21.md)
 
-- Reads Modbus holding registers from a heat pump
-- Configurable send interval to InfluxDB (default: 5 minutes)
-- Automatic buffering when InfluxDB is unavailable (up to 50,000 data points)
-- Health check endpoint for monitoring application status
-- Automatic restart on Modbus connection failures
-- Graceful shutdown with InfluxDB buffer flush
-- Systemd service with automatic recovery
-- Configurable via JSON file
+| Part | Runs | Readme |
+|---|---|---|
+| `gateway/` | Pi in Krosno, Docker: devices to InfluxDB, `/commands` | [gateway/README.md](gateway/README.md) |
+| `backend/` | Kraków, Docker: phone API | [backend/README.md](backend/README.md) |
+| `frontend/` | Kraków, Docker: web UI with nginx | [frontend/README.md](frontend/README.md) |
 
-## Quick Start
-
-### Local Development
-```bash
-mvn clean package
-java -jar target/home-pump-1.0.0.jar
-```
-
-### Production Deployment (Raspberry Pi / Ubuntu)
-See [DEPLOYMENT.md](DEPLOYMENT.md) for complete installation and configuration guide.
+Each part has its `Dockerfile` and `compose.yaml` (ADR-010).
 
 ```bash
-# Build
-mvn clean package
-
-# Install as systemd service
-sudo scripts/install-service.sh
-
-# Check status
-systemctl status home-pump.service
-curl http://localhost:8080/health
-```
-
-## Configuration
-
-Edit `src/main/resources/registryMapping.json` to configure:
-
-- Modbus TCP connection (address, port)
-- InfluxDB connection (address, username, password)
-- Send interval (influxSendIntervalSeconds, default: 300)
-- Connection timeouts and retry settings
-- List of registers to read with descriptions
-
-Additional mapping fields (optional):
-
-- `useMock` (Boolean, top-level): When `true`, the application runs with a local `MockRepository` instead of attempting to connect to a Modbus device. Useful for local development when a device is not available (default: false).
-
-- `unitId` (Integer): Modbus slave/unit id for the register (default: 1)
-- `scale` (Double): Multiply raw device value by this to obtain display value (default: 0.1)
-- `dataType` (String): Data type used for the locator (e.g. `TWO_BYTE_INT_SIGNED`). Supported values: `TWO_BYTE_INT_SIGNED`, `TWO_BYTE_INT_UNSIGNED`, `FOUR_BYTE_INT_SIGNED`, `FOUR_BYTE_INT_UNSIGNED`, `FOUR_BYTE_FLOAT` (the latter reads two adjacent registers and interprets as IEEE754 float). For devices with non-standard word order, the following swapped variants are supported: `FOUR_BYTE_INT_SWAPPED`, `FOUR_BYTE_INT_UNSIGNED_SWAPPED`, `FOUR_BYTE_FLOAT_SWAPPED` (word order low/high).
-- # Example Configuration
-```json
-{
-  "address": "192.168.0.150",
-  "port": 502,
-  "useMock": false,
-  "influxSendIntervalSeconds": 300,
-  "timeoutMs": 5000,
-  "maxRetries": 2,
-  "retryBackoffMs": 1000,
-  "influx_db": {
-    "address": "https://influxdb.example.com",
-    "username": "",
-    "password": ""
-  },
-  "registry_mapping": [
-    {
-      "registry": 4065,
-      "desc": "External temperature",
-      "unitId": 1,
-      "scale": 0.1,
-      "dataType": "TWO_BYTE_INT_SIGNED"
-    }
-  ]
-}
-```
-
-## Monitoring & Health Check
-
-The application exposes a health check endpoint on port 8080:
-
-```bash
-curl http://localhost:8080/health
-```
-
-**Healthy response (HTTP 200):**
-```json
-{
-  "status": "UP",
-  "lastSuccessfulRead": "2026-02-06T19:30:45Z",
-  "message": "Last successful read 15 seconds ago"
-}
-```
-
-**Unhealthy response (HTTP 503):**
-```json
-{
-  "status": "DOWN",
-  "lastSuccessfulRead": "2026-02-06T19:20:45Z",
-  "message": "No successful read for 620 seconds. Last error: Connection timeout"
-}
-```
-
-### Important Notes
-
-- **InfluxDB failures do NOT trigger unhealthy status** - data is buffered in memory
-- Only Modbus read failures trigger unhealthy status and potential restart
-- Health check considers the application unhealthy if no successful Modbus read within 2× send interval
-- Automatic monitoring script restarts the service on health check failures
-
-## Production Deployment
-
-For production use on Raspberry Pi or Ubuntu server:
-
-1. **Install as systemd service** - Auto-start on boot with resource limits
-2. **Enable health monitoring** - Cron job checks health every 2 minutes
-3. **Automatic recovery** - Restarts service on Modbus failures (max 3 attempts per 10 minutes)
-4. **Graceful shutdown** - Flushes buffered data to InfluxDB before exit
-
-See [DEPLOYMENT.md](DEPLOYMENT.md) for detailed instructions.
-
-## Data Buffering
-
-When InfluxDB is unavailable, data is automatically buffered:
-
-- **Buffer size**: 50,000 data points in memory
-- **Batch size**: 50 points per flush
-- **Flush interval**: 180 seconds (3 minutes)
-- **No data loss**: Buffer persists during InfluxDB outages
-- **Automatic retry**: Built-in retry mechanism in InfluxDB Java client
-
-## Troubleshooting
-
-### Check application logs
-```bash
-journalctl -u home-pump.service -f
-```
-
-### Test health endpoint
-```bash
-./scripts/test-health.sh
-```
-
-### View monitor logs
-```bash
-tail -f /var/log/home-pump-monitor.log
-```
-
-### Common Issues
-
-1. **Service won't start**: Check JAR file exists and Java 21 is installed
-2. **Health check fails**: Verify Modbus device is accessible
-3. **InfluxDB connection errors**: Check network and credentials (data will be buffered)
-4. **Too many restarts**: Check Modbus device connectivity and network stability clean package
-java -jar target/home-pump-1.0.0.jar
-```
-
-## Requirements
-
-- Java 21
-- Modbus TCP accessible heat pump
-- InfluxDB instance
-
-## Frontend Dashboard (React + TypeScript + MUI)
-
-Nowy frontend znajduje się w folderze `frontend` i zawiera:
-
-- Vite + React + TypeScript
-- Material UI w ciemnym stylu
-- Recharts do wykresów operacyjnych
-- Architektura isomorphic-ready (`entry-client.tsx` i `entry-server.tsx`)
-- Reużywalne komponenty i warstwa usług gotowa pod rozbudowę API
-
-### Uruchomienie frontendu
-
-```bash
-cd frontend
-npm install
-npm run dev
-```
-
-### Build produkcyjny
-
-```bash
-cd frontend
-npm run build
-```
-
-### Build SSR (isomorphic)
-
-```bash
-cd frontend
-npm run build:ssr
+scripts/check.sh                       # docs, secret scan, build and tests of all three parts
+git config core.hooksPath .githooks    # once per clone: check before every push
+scripts/release.sh vMAJOR.MINOR.PATCH  # tag master; CI publishes the three images in Gitea
 ```
 
+After a release: on the Pi `./update.sh <version>` (gateway/README.md); in Kraków Arcane runs the
+backend and frontend images.

backend/.dockerignore

@@ -0,0 +1 @@
+target

backend/Dockerfile

@@ -0,0 +1,22 @@
+# Built on the build machine's own platform; the image only holds the jar and a JRE.
+FROM --platform=$BUILDPLATFORM maven:3.9-eclipse-temurin-21 AS build
+WORKDIR /src
+COPY pom.xml .
+RUN mvn -B -q dependency:go-offline
+COPY src src
+# Tests run in scripts/check.sh; some read contract files from gateway/, outside this context.
+RUN mvn -B -q package -Dmaven.test.skip=true
+
+FROM eclipse-temurin:21-jre-alpine
+# The release tag, shown in /api/health; the release workflow passes it.
+ARG VERSION=dev
+ENV VERSION=$VERSION
+USER 10001:10001
+WORKDIR /app
+COPY --from=build /src/target/home-pump-backend-1.0.0.jar app.jar
+EXPOSE 8080
+# /api/health answers 200 even while the gateway is unreachable (it reports that in the body),
+# so this only tells whether the backend itself serves requests. busybox wget ships with alpine.
+HEALTHCHECK --interval=30s --timeout=3s --start-period=10s \
+    CMD wget -q -O /dev/null "http://127.0.0.1:${PORT:-8080}/api/health" || exit 1
+ENTRYPOINT ["java", "-jar", "app.jar"]

backend/README.md

@@ -0,0 +1,86 @@
+# Backend
+
+The phone API in Kraków (ADR-008): live state from the gateway, history from InfluxDB, setpoint
+changes passed to the gateway. JSON under `/api/` only; the web UI is the frontend's (ADR-010).
+The records in `home.backend.domain` and the examples in `src/test/resources/api/` are the contract.
+`GET /api/energy/details` lists the Deye, Fronius and house meter values in labelled groups (a stale device has none); the label, unit and place of every field are the catalog in `EnergyDetailsService`: a new field is one line there.
+`GET /api/pi-sensor` is the BME280 sensor on the Raspberry Pi (the living room), example `src/test/resources/api/pi-sensor.json`:
+`time`, `stale`, `temperature` (°C), `humidity` (%), `pressure` (hPa). When it is stale (device down, no reading or older than 10 min)
+the three values are null (`pi-sensor-stale.json`).
+
+`GET /api/stats?range=7d|30d` (example `src/test/resources/api/stats.json`; 400 otherwise, 502 when InfluxDB is down) is the heat pump per local
+day (Europe/Warsaw, today included) from the raw `heat_pump` polls: `days[]` with `date`, `compressorHours`, `compressorStarts`, `cwuHours`, `coHours`,
+`heaterHours`, `avgOutdoorTemp`, `minCwuTemp`, `maxCwuTemp` (all null on a day without polls) and `totals` over the range. A poll holds its outputs
+until the next one, at most 600 s, so gaps add no hours; a start is a poll above 0 after a poll at 0, so the 300 s polling misses short cycles.
+
+`GET /api/battery` is the Deye battery, example `src/test/resources/api/battery.json`: live `socPct`, `powerW` (+ discharge / − charge), `voltageV`,
+`currentA`, `temperatureC`, `today` and `total` energy (`chargeKwh`, `dischargeKwh`), null when the Deye is stale (older than 10 min or down).
+The settings come from the gateway's slower `deye_settings` reading and are stale after 30 min (`battery-settings-stale.json`):
+`mode` (`touEnabled` with a Polish sentence), `schedule` (six slots, each from its start to the next one, the last wraps past midnight),
+`limits`, and `capacityKwh` = capacity in Ah x a nominal 51.2 V, since the inverter reports Ah only. When stale they are null (`schedule` empty).
+
+`/api/battery` also has `reserve` (`pct`, `floorPct`: the backup reserve of the app and the lowest the user may set) and `editable`:
+true when the gateway answers its `/battery/reserve`, i.e. it has battery commands on and `GATEWAY_TOKEN` is right; else `reserve` is null
+and `editable` false. `POST /api/battery/schedule` (examples `battery-schedule-request.json`, `battery-failed.json`) takes
+`{"enabled"?, "slots": [{"slot": 1-6, "from"?: "HH:MM", "socPct"?, "gridCharge"?}]}` and `POST /api/battery/reserve` takes `{"pct": 60}`.
+Same Origin, header and JSON rules as the other writes; `Remote-User` goes on as the requester. The gateway's verdict comes back as
+`{status, message, read}`: 200 applied, 422 rejected, 409 settings unknown or changed meanwhile, 429 too soon, 502 failed (`read` is what the
+inverter holds), 400 bad body, 503 gateway unreachable or without battery commands (ADR-013).
+
+`GET /api/audit?range=7d` (`24h`, `7d` default, `30d`; 400 otherwise, 502 when InfluxDB fails) is the change history, example
+`src/test/resources/api/audit.json`: the gateway's audit rows of the heat pump (`Dom_Pompa.setpoint_audit`) and the battery
+(`electricity.deye_settings_audit`), read only, as `entries` newest first: `time`, `source` (`heat_pump`, `battery`), `what` (Polish label;
+the Deye registers are named in `DeyeSettingLabels`), `oldValue`/`newValue` (whole numbers, null when not recorded), `unit` (`°C`, `%`,
+`HHMM`, `0/1`), `who` (`Remote-User` of the request; a restore is "automatycznie (przywrócenie)") and `status` (the gateway's: APPLIED, FAILED, REJECTED, CONFLICT, INVALID).
+
+`GET /api/weather` (example `src/test/resources/api/weather.json`) is the forecast of Open-Meteo for the house and the IMGW warnings that name
+Krosno (TERYT 1862 or the powiat 1807): `today`, `tomorrow`, `dayAfter` (`date`, `weatherCode` WMO, Polish `description`, `tMax`, `tMin`,
+`precipitationMm`, `sunshineHours`, `pvForecastKwh`), `now.temperature`, `warnings` (`event`, `level` 1-3, `from`, `to`, `text`; the ones that
+ended are dropped). `pvFactor` is kWh per MJ/m^2: the Deye plus Fronius energy of the past 14 complete days (from InfluxDB, daily maximum of
+`pv_today_kwh` and `energy_day_wh`) over the forecast radiation of the same days, so no tilt or azimuth is needed; `pvForecastKwh` is the factor
+times the day's radiation, and both are null with fewer than 5 days that have both values. The forecast is kept 30 min and the warnings 10 min;
+when a refresh fails the older answer is served with `stale` true. 503 only when there never was a forecast. The sources are public and need no key.
+
+Settings are environment variables (`.env` next to `compose.yaml`); the backend refuses to start
+without the two URLs.
+Setpoint changes go only to the gateway; the user name from Traefik's `Remote-User` header (else `phone`) is sent as `X-Requested-By`.
+
+| Variable | Default | Meaning |
+|---|---|---|
+| `GATEWAY_URL` | required | the gateway on the Pi, e.g. `http://10.0.0.2:8080` |
+| `INFLUX_URL` | required | InfluxDB 1.x, e.g. `https://influxdb.example` |
+| `PORT` | `8080` | listening port |
+| `GATEWAY_TIMEOUT` | `5` | seconds |
+| `INFLUX_TIMEOUT` | `10` | seconds |
+| `GATEWAY_TOKEN` | unset | shared token for the gateway's `/commands`; without it the backend runs but `/api/setpoints` and `/api/presets/{id}` answer 503 |
+| `WEATHER_LAT`, `WEATHER_LON` | `49.684`, `21.770` | where the house is (Krosno, ul. Szczepańcowa), for the forecast |
+| `WEATHER_TERYT` | `1862,1807` | comma-separated TERYT powiat codes whose IMGW warnings count |
+| `PRESETS_FILE` | built-in | JSON file replacing the presets: `[{"id", "name", "changes": [{"setpoint", "value", "hours"}]}]`, `hours` null means until changed; a bad file stops the start. A preset may also have `"until": "chosen"` (then no `hours`): the user picks the end, see below |
+
+```bash
+mvn -f backend/pom.xml clean package
+GATEWAY_URL=http://10.0.0.2:8080 INFLUX_URL=https://influxdb.example \
+  java -jar backend/target/home-pump-backend-1.0.0.jar        # API at http://localhost:8080/api/
+docker compose -f backend/compose.yaml up --build              # with backend/.env; network home-pump
+```
+
+`POST /api/presets/{id}` takes no body for an ordinary preset. A preset with `"until": "chosen"` (the built-in "Wyjazd")
+needs `{"until": "2026-11-02T18:00:00+01:00"}` (ISO-8601 with offset, example `src/test/resources/api/preset-away-request.json`):
+400 when it is missing, invalid, or sent to a preset that has none. Any preset also takes optional `"values"`
+(example `preset-away-values-request.json`): a whole number per setpoint of that preset, replacing the preset's value;
+the others keep it. 400 for a setpoint the preset does not change or a value outside the gateway's min, max and step
+(from `/commands`), checked before anything is sent; a held value that is not below the current one is 422. The gateway holds those changes until then without
+renewals (ADR-012) and rejects an end that is past or over 30 days away, or a change that does not lower the value (422).
+
+`POST /api/setpoints/{name}/restore` (same Origin, header and JSON rules as the other writes; send `{}`) ends the
+pending change of that setpoint now and answers with the gateway's verdict, example
+`src/test/resources/api/setpoint-restored.json`: 200 restored, 404 nothing pending, 409 the value was changed
+meanwhile (left alone, the restore is dropped), 429 too soon after the last write, 502 failed (the restore stays
+pending), 503 gateway unreachable.
+
+Publish no host port in production: only the frontend, behind Traefik, may reach the backend. It
+trusts `Remote-User` and has no login of its own, so a direct port would bypass Traefik's access
+rules (ADR-009).
+
+`/api/health` also carries `backendVersion` (the `VERSION` the image was built with, `dev` locally) and
+`gatewayVersion` (from the gateway's `/health`; null when it is unreachable or too old to report it).

backend/compose.yaml

@@ -0,0 +1,16 @@
+# The backend in Kraków: the API only (ADR-010), reached by the frontend on the network home-pump
+# and published on no host port (ADR-009). Settings in .env next to this file (README).
+name: home-pump-backend
+services:
+  backend:
+    image: git.mariuszpacek.pl/mariusz.pacek/home-pump-backend:${VERSION:-latest}
+    build: .
+    restart: unless-stopped
+    env_file: .env
+    environment:
+      TZ: Europe/Warsaw
+    networks: [home-pump]
+
+networks:
+  home-pump:
+    name: home-pump

backend/pom.xml

@@ -0,0 +1,84 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.home</groupId>
+    <artifactId>home-pump-backend</artifactId>
+    <version>1.0.0</version>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <maven.compiler.release>21</maven.compiler.release>
+        <jackson.version>2.20.1</jackson.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+            <version>${jackson.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.datatype</groupId>
+            <artifactId>jackson-datatype-jsr310</artifactId>
+            <version>${jackson.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-simple</artifactId>
+            <version>1.7.32</version>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>5.10.0</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-junit-jupiter</artifactId>
+            <version>5.8.0</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.13.0</version>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>3.1.2</version>
+                <configuration>
+                    <redirectTestOutputToFile>true</redirectTestOutputToFile>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-shade-plugin</artifactId>
+                <version>3.4.1</version>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>shade</goal>
+                        </goals>
+                        <configuration>
+                            <createDependencyReducedPom>false</createDependencyReducedPom>
+                            <transformers>
+                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
+                                    <mainClass>home.backend.Main</mainClass>
+                                </transformer>
+                            </transformers>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>

backend/src/main/java/home/backend/Backend.java

@@ -0,0 +1,79 @@
+package home.backend;
+
+import home.backend.adapters.config.PresetFile;
+import home.backend.adapters.gateway.GatewayHttpClient;
+import home.backend.adapters.gateway.GatewayHttpCommands;
+import home.backend.adapters.http.ApiServer;
+import home.backend.adapters.influx.InfluxAuditRepository;
+import home.backend.adapters.influx.InfluxHistoryRepository;
+import home.backend.adapters.influx.InfluxPvEnergy;
+import home.backend.adapters.influx.InfluxSettings;
+import home.backend.adapters.weather.ImgwClient;
+import home.backend.adapters.weather.OpenMeteoClient;
+import home.backend.adapters.weather.WeatherSettings;
+import home.backend.application.AuditService;
+import home.backend.application.BatteryService;
+import home.backend.application.EnergyDetailsService;
+import home.backend.application.EnergyService;
+import home.backend.application.HealthService;
+import home.backend.application.HeatPumpService;
+import home.backend.application.HistoryService;
+import home.backend.application.StatsService;
+import home.backend.application.LeaseRenewer;
+import home.backend.application.PiSensorService;
+import home.backend.application.SetpointService;
+import home.backend.application.WeatherService;
+
+import java.io.IOException;
+import java.net.URI;
+import java.time.Clock;
+import java.time.Duration;
+import java.util.Objects;
+
+/** Wires the adapters and services together; the only place that knows all of them. */
+final class Backend {
+
+    private static final Duration WEATHER_TIMEOUT = Duration.ofSeconds(10);
+
+    private Backend() {
+    }
+
+    /**
+     * Binds the port but does not start serving.
+     *
+     * @throws IllegalArgumentException when PRESETS_FILE is unusable
+     */
+    static ApiServer assemble(Settings settings, Clock clock) throws IOException {
+        var gateway = new GatewayHttpClient(settings.gatewayUrl(), settings.gatewayTimeout());
+        var influxSettings = new InfluxSettings(settings.influxUrl(), settings.influxTimeout());
+        var influx = new InfluxHistoryRepository(influxSettings);
+        var commands = commands(settings);
+        var setpoints = new SetpointService(commands, PresetFile.load(settings.presetsFile()));
+        return new ApiServer(settings.port(),
+                new HeatPumpService(gateway, clock),
+                new EnergyService(gateway, clock),
+                new EnergyDetailsService(gateway, clock),
+                new HealthService(gateway, clock, Objects.requireNonNullElse(System.getenv("VERSION"), "dev")),
+                new HistoryService(influx, clock), setpoints, new PiSensorService(gateway, clock),
+                new BatteryService(gateway, commands, clock),
+                new AuditService(new InfluxAuditRepository(influxSettings), clock), new StatsService(influx, clock),
+                weather(influxSettings, clock));
+    }
+
+    private static WeatherService weather(InfluxSettings influx, Clock clock) {
+        var place = WeatherSettings.fromEnvironment(System.getenv());
+        return new WeatherService(
+                new OpenMeteoClient(URI.create("https://api.open-meteo.com"), place, WEATHER_TIMEOUT),
+                new ImgwClient(URI.create("https://danepubliczne.imgw.pl"), place, WEATHER_TIMEOUT),
+                new InfluxPvEnergy(influx), clock);
+    }
+
+    /** Keeps the gateway from restoring our setpoint changes while we are up (ADR-011). */
+    static LeaseRenewer leaseRenewer(Settings settings) {
+        return new LeaseRenewer(commands(settings));
+    }
+
+    private static GatewayHttpCommands commands(Settings settings) {
+        return new GatewayHttpCommands(settings.gatewayUrl(), settings.gatewayToken(), settings.gatewayTimeout());
+    }
+}

backend/src/main/java/home/backend/Main.java

@@ -0,0 +1,35 @@
+package home.backend;
+
+import home.backend.adapters.http.ApiServer;
+
+import java.io.IOException;
+import java.time.Clock;
+
+public final class Main {
+
+    private Main() {
+    }
+
+    public static void main(String[] args) throws IOException {
+        Settings settings;
+        ApiServer server;
+        try {
+            settings = Settings.fromEnvironment(System.getenv());
+            server = Backend.assemble(settings, Clock.systemUTC());
+        } catch (IllegalArgumentException e) {
+            System.err.println("home-pump-backend: " + e.getMessage());
+            System.exit(2);
+            return;
+        }
+        Runtime.getRuntime().addShutdownHook(new Thread(server::stop));
+        if (settings.gatewayToken() == null) {
+            System.err.println("home-pump-backend: GATEWAY_TOKEN is not set, setpoint changes are disabled");
+        } else {
+            var renewer = Backend.leaseRenewer(settings);
+            Runtime.getRuntime().addShutdownHook(new Thread(renewer::close));
+            renewer.start();
+        }
+        server.start();
+        System.out.println("home-pump-backend listening on port " + server.port());
+    }
+}

backend/src/main/java/home/backend/Settings.java

@@ -0,0 +1,65 @@
+package home.backend;
+
+import java.net.URI;
+import java.nio.file.Path;
+import java.time.Duration;
+import java.util.Map;
+import java.util.Optional;
+
+/** Twelve-factor settings: everything comes from environment variables. */
+public record Settings(URI gatewayUrl, URI influxUrl, int port, Duration gatewayTimeout, Duration influxTimeout,
+        String gatewayToken, Path presetsFile) {
+
+    public static Settings fromEnvironment(Map<String, String> env) {
+        return new Settings(
+                url(env, "GATEWAY_URL"),
+                url(env, "INFLUX_URL"),
+                (int) number(env, "PORT", 8080, 0, 65535),
+                Duration.ofSeconds(number(env, "GATEWAY_TIMEOUT", 5, 1, 300)),
+                Duration.ofSeconds(number(env, "INFLUX_TIMEOUT", 10, 1, 300)),
+                optional(env, "GATEWAY_TOKEN"),
+                Optional.ofNullable(optional(env, "PRESETS_FILE")).map(Path::of).orElse(null));
+    }
+
+    /** Null when unset or blank. */
+    private static String optional(Map<String, String> env, String name) {
+        String value = env.get(name);
+        return value == null || value.isBlank() ? null : value.strip();
+    }
+
+    private static URI url(Map<String, String> env, String name) {
+        String value = env.get(name);
+        if (value == null || value.isBlank()) {
+            throw new IllegalArgumentException(name + " is required, e.g. " + name + "=http://host:8080");
+        }
+        URI uri = URI.create(value.strip());
+        if (uri.getHost() == null || !("http".equals(uri.getScheme()) || "https".equals(uri.getScheme()))) {
+            throw new IllegalArgumentException(name + " must be an http(s) URL with a host, got: " + value);
+        }
+        // The clients append their own paths to this base; a path here would be silently dropped or doubled.
+        boolean hasPath = !uri.getRawPath().isEmpty() && !uri.getRawPath().equals("/");
+        if (hasPath || uri.getRawQuery() != null || uri.getRawFragment() != null) {
+            throw new IllegalArgumentException(name + " must be only scheme, host and port, without a path, got: "
+                    + value);
+        }
+        return uri;
+    }
+
+    /** Timeouts are whole seconds. */
+    private static long number(Map<String, String> env, String name, long fallback, long min, long max) {
+        String value = env.get(name);
+        if (value == null || value.isBlank()) {
+            return fallback;
+        }
+        try {
+            long number = Long.parseLong(value.strip());
+            if (number >= min && number <= max) {
+                return number;
+            }
+        } catch (NumberFormatException e) {
+            // reported below with the same message
+        }
+        throw new IllegalArgumentException(name + " must be a whole number from " + min + " to " + max
+                + ", got: " + value);
+    }
+}

backend/src/main/java/home/backend/adapters/config/PresetFile.java

@@ -0,0 +1,41 @@
+package home.backend.adapters.config;
+
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import home.backend.domain.Preset;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.HashSet;
+import java.util.List;
+
+/** Reads the presets (F3) from the optional PRESETS_FILE, else the built-in list. */
+public final class PresetFile {
+
+    private static final ObjectMapper JSON = new ObjectMapper();
+    private static final TypeReference<List<Preset>> PRESETS = new TypeReference<>() {
+    };
+
+    private PresetFile() {
+    }
+
+    /** @param file null for the built-in defaults; IllegalArgumentException when it is unusable */
+    public static List<Preset> load(Path file) {
+        String source = file == null ? "built-in presets" : "PRESETS_FILE " + file;
+        try (InputStream in = file == null ? defaults() : Files.newInputStream(file)) {
+            List<Preset> presets = JSON.readValue(in, PRESETS);
+            if (new HashSet<>(presets.stream().map(Preset::id).toList()).size() != presets.size()) {
+                throw new IllegalArgumentException("preset ids must be unique");
+            }
+            return presets;
+        } catch (IOException | IllegalArgumentException e) {
+            throw new IllegalArgumentException(source + " is not usable: " + e.getMessage(), e);
+        }
+    }
+
+    private static InputStream defaults() {
+        return PresetFile.class.getResourceAsStream("/presets-default.json");
+    }
+}

backend/src/main/java/home/backend/adapters/gateway/GatewayHttpClient.java

@@ -0,0 +1,88 @@
+package home.backend.adapters.gateway;
+
+import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+import home.backend.application.GatewayClient;
+import home.backend.domain.GatewaySnapshot;
+import home.backend.domain.GatewaySnapshot.DeviceSnapshot;
+import home.backend.domain.GatewaySnapshot.Measurement;
+
+import java.io.IOException;
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+/** Reads the gateway's {@code /health} and {@code /snapshot} over HTTP. */
+public class GatewayHttpClient implements GatewayClient {
+
+    private record Health(String version, List<DeviceHealth> devices) {
+    }
+
+    private record DeviceHealth(String name, String status, Instant lastSuccess, String lastError) {
+    }
+
+    private record DeviceReadings(String name, List<Reading> readings) {
+    }
+
+    private record Reading(String database, String measurement, Map<String, Double> fields, Instant time) {
+    }
+
+    // Unknown properties are ignored so the gateway can add fields without breaking us.
+    private static final ObjectMapper JSON = new ObjectMapper()
+            .registerModule(new JavaTimeModule())
+            .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
+
+    private final URI baseUri;
+    private final Duration timeout;
+    private final HttpClient http;
+
+    public GatewayHttpClient(URI baseUri, Duration timeout) {
+        this.baseUri = baseUri;
+        this.timeout = timeout;
+        this.http = HttpClient.newBuilder().connectTimeout(timeout).build();
+    }
+
+    @Override
+    public GatewaySnapshot snapshot() throws IOException {
+        var health = JSON.readValue(get("/health", true), Health.class);
+        var readings = JSON.readValue(get("/snapshot", false), DeviceReadings[].class);
+        Map<String, List<Measurement>> measurements = Arrays.stream(readings)
+                .collect(Collectors.toMap(DeviceReadings::name, GatewayHttpClient::measurements));
+        var devices = health.devices().stream()
+                .map(device -> new DeviceSnapshot(device.name(), device.status().equals("UP"),
+                        device.lastSuccess(), device.lastError(),
+                        measurements.getOrDefault(device.name(), List.of())))
+                .toList();
+        return new GatewaySnapshot(health.version(), devices);
+    }
+
+    private static List<Measurement> measurements(DeviceReadings device) {
+        return device.readings().stream()
+                .map(r -> new Measurement(r.database(), r.measurement(), r.fields(), r.time()))
+                .toList();
+    }
+
+    /** A gateway with a device down answers /health with 503 and a valid body. */
+    private byte[] get(String path, boolean downIsValid) throws IOException {
+        var request = HttpRequest.newBuilder(baseUri.resolve(path)).timeout(timeout).GET().build();
+        try {
+            var response = http.send(request, HttpResponse.BodyHandlers.ofByteArray());
+            int status = response.statusCode();
+            if (status != 200 && !(downIsValid && status == 503)) {
+                throw new IOException("gateway " + path + " answered " + status);
+            }
+            return response.body();
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+            throw new IOException("interrupted while calling gateway " + path, e);
+        }
+    }
+}

backend/src/main/java/home/backend/adapters/gateway/GatewayHttpCommands.java

@@ -0,0 +1,164 @@
+package home.backend.adapters.gateway;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+import home.backend.application.GatewayBattery;
+import home.backend.application.GatewayCommands;
+import home.backend.domain.BatteryChange;
+import home.backend.domain.BatteryResult;
+import home.backend.domain.BatteryView.Reserve;
+import home.backend.domain.Command;
+import home.backend.domain.CommandResult;
+import home.backend.domain.RestoreResult;
+import home.backend.domain.SetpointState;
+
+import java.io.IOException;
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.List;
+import java.util.Set;
+
+/** Sends commands to the gateway's {@code /commands} and {@code /battery} with the shared token (S6). */
+public class GatewayHttpCommands implements GatewayCommands, GatewayBattery {
+
+    /** The gateway answers a verdict with 200 (applied), 422 (rejected) or 502 (failed). */
+    private static final Set<Integer> VERDICTS = Set.of(200, 422, 502);
+
+    /** Restore now: 200 restored, 404 nothing pending, 409 changed meanwhile, 429 too soon, 502 failed. */
+    private static final Set<Integer> RESTORE_VERDICTS = Set.of(200, 404, 409, 429, 502);
+
+    /** Battery change: 200 applied, 422 rejected, 409 stale or changed meanwhile, 429 too soon, 502 failed. */
+    private static final Set<Integer> BATTERY_VERDICTS = Set.of(200, 422, 409, 429, 502);
+
+    @JsonInclude(JsonInclude.Include.NON_NULL)
+    private record ScheduleRequest(Boolean enabled, List<SlotRequest> slots) {
+    }
+
+    @JsonInclude(JsonInclude.Include.NON_NULL)
+    private record SlotRequest(int slot, Integer start, Integer soc, Boolean gridCharge) {
+    }
+
+    private record ReserveRequest(int pct) {
+    }
+
+    @JsonInclude(JsonInclude.Include.NON_NULL)
+    private record Request(String setpoint, int value, Long minutes, Instant until) {
+    }
+
+    private record RestoreRequest(String setpoint) {
+    }
+
+    private record Renewal(int renewed) {
+    }
+
+    private static final ObjectMapper JSON = new ObjectMapper()
+            .registerModule(new JavaTimeModule())
+            .disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
+            .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
+
+    private final URI endpoint;
+    private final URI renewEndpoint;
+    private final URI restoreEndpoint;
+    private final URI reserveEndpoint;
+    private final URI scheduleEndpoint;
+    private final String token;
+    private final Duration timeout;
+    private final HttpClient http;
+
+    /** @param token null when not configured: every call then fails without touching the network */
+    public GatewayHttpCommands(URI baseUri, String token, Duration timeout) {
+        this.endpoint = baseUri.resolve("/commands");
+        this.renewEndpoint = baseUri.resolve("/commands/renew");
+        this.restoreEndpoint = baseUri.resolve("/commands/restore");
+        this.reserveEndpoint = baseUri.resolve("/battery/reserve");
+        this.scheduleEndpoint = baseUri.resolve("/battery/schedule");
+        this.token = token;
+        this.timeout = timeout;
+        this.http = HttpClient.newBuilder().connectTimeout(timeout).build();
+    }
+
+    @Override
+    public CommandResult apply(Command command) throws IOException {
+        Long minutes = command.duration() == null ? null : command.duration().toMinutes();
+        byte[] body = JSON.writeValueAsBytes(new Request(command.setpoint(), command.value(), minutes, command.heldUntil()));
+        HttpRequest.Builder request = request().header("Content-Type", "application/json")
+                .header("X-Requested-By", command.requestedBy())
+                .POST(HttpRequest.BodyPublishers.ofByteArray(body));
+        return JSON.readValue(send(request, VERDICTS), CommandResult.class);
+    }
+
+    @Override
+    public RestoreResult restore(String setpoint, String requestedBy) throws IOException {
+        byte[] body = JSON.writeValueAsBytes(new RestoreRequest(setpoint));
+        var request = request(restoreEndpoint).header("Content-Type", "application/json")
+                .header("X-Requested-By", requestedBy).POST(HttpRequest.BodyPublishers.ofByteArray(body));
+        return JSON.readValue(send(request, RESTORE_VERDICTS), RestoreResult.class);
+    }
+
+    @Override
+    public SetpointState setpoints() throws IOException {
+        return JSON.readValue(send(request().GET(), Set.of(200)), SetpointState.class);
+    }
+
+    @Override
+    public int renewLeases() throws IOException {
+        var request = request(renewEndpoint).POST(HttpRequest.BodyPublishers.noBody());
+        return JSON.readValue(send(request, Set.of(200)), Renewal.class).renewed();
+    }
+
+    @Override
+    public Reserve reserve() throws IOException {
+        return JSON.readValue(send(request(reserveEndpoint).GET(), Set.of(200)), Reserve.class);
+    }
+
+    @Override
+    public BatteryResult changeSchedule(BatteryChange change, String requestedBy) throws IOException {
+        var slots = change.slots().stream().map(slot -> new SlotRequest(slot.slot(),
+                slot.from() == null ? null : slot.from().getHour() * 100 + slot.from().getMinute(),
+                slot.socPct(), slot.gridCharge())).toList();
+        return battery(scheduleEndpoint, new ScheduleRequest(change.enabled(), slots), requestedBy);
+    }
+
+    @Override
+    public BatteryResult changeReserve(int pct, String requestedBy) throws IOException {
+        return battery(reserveEndpoint, new ReserveRequest(pct), requestedBy);
+    }
+
+    private BatteryResult battery(URI uri, Object body, String requestedBy) throws IOException {
+        var request = request(uri).header("Content-Type", "application/json").header("X-Requested-By", requestedBy)
+                .POST(HttpRequest.BodyPublishers.ofByteArray(JSON.writeValueAsBytes(body)));
+        return JSON.readValue(send(request, BATTERY_VERDICTS), BatteryResult.class);
+    }
+
+    private HttpRequest.Builder request() throws IOException {
+        return request(endpoint);
+    }
+
+    private HttpRequest.Builder request(URI uri) throws IOException {
+        if (token == null) {
+            throw new IOException("GATEWAY_TOKEN is not set, commands are disabled");
+        }
+        return HttpRequest.newBuilder(uri).timeout(timeout).header("Authorization", "Bearer " + token);
+    }
+
+    private byte[] send(HttpRequest.Builder request, Set<Integer> accepted) throws IOException {
+        try {
+            var built = request.build();
+            var response = http.send(built, HttpResponse.BodyHandlers.ofByteArray());
+            if (!accepted.contains(response.statusCode())) {
+                throw new IOException("gateway " + built.uri().getPath() + " answered " + response.statusCode());
+            }
+            return response.body();
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+            throw new IOException("interrupted while calling the gateway", e);
+        }
+    }
+}

backend/src/main/java/home/backend/adapters/http/ApiServer.java

@@ -0,0 +1,426 @@
+package home.backend.adapters.http;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.MapperFeature;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+import com.sun.net.httpserver.HttpExchange;
+import com.sun.net.httpserver.HttpHandler;
+import com.sun.net.httpserver.HttpServer;
+import home.backend.application.AuditService;
+import home.backend.application.BatteryService;
+import home.backend.application.EnergyDetailsService;
+import home.backend.application.EnergyService;
+import home.backend.application.HealthService;
+import home.backend.application.HeatPumpService;
+import home.backend.application.HistoryService;
+import home.backend.application.StatsService;
+import home.backend.application.PiSensorService;
+import home.backend.application.SetpointService;
+import home.backend.application.WeatherService;
+import home.backend.domain.BatteryChange;
+import home.backend.domain.BatteryResult;
+import home.backend.domain.CommandResult.Status;
+import home.backend.domain.PresetResult;
+import home.backend.domain.RestoreResult;
+
+import java.io.IOException;
+import java.time.OffsetDateTime;
+import java.time.format.DateTimeParseException;
+import java.net.InetSocketAddress;
+import java.net.URLDecoder;
+import java.nio.charset.StandardCharsets;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.regex.Pattern;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+/** The phone-facing JSON API under {@code /api/} and the static web UI. */
+public class ApiServer {
+
+    private static final ObjectMapper JSON = new ObjectMapper()
+            .registerModule(new JavaTimeModule())
+            .disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
+            // 45.5 or "45" must not silently become 45 in a request that writes to a heat pump.
+            .disable(DeserializationFeature.ACCEPT_FLOAT_AS_INT)
+            .disable(MapperFeature.ALLOW_COERCION_OF_SCALARS);
+
+    private record ReserveRequest(Integer pct) {
+    }
+
+    private record SetpointRequest(String setpoint, Integer value, Double hours) {
+    }
+
+    /** {@code values}: the user's own value per setpoint of the preset, by setpoint name. */
+    private record PresetRequest(String until, Map<String, Integer> values) {
+
+        PresetRequest {
+            if (values == null) {
+                values = Map.of();
+            } else if (values.containsValue(null)) {
+                throw new IllegalArgumentException("a value must be a number");
+            }
+        }
+    }
+
+    private static final String UNREACHABLE = "gateway unreachable";
+    private static final String UNAVAILABLE = "battery changes are not available: gateway unreachable or not enabled";
+    private static final String WRITE_MARKER = "home-pump";
+    private static final String PRESETS_PATH = "/api/presets/";
+    private static final String SETPOINTS_PATH = "/api/setpoints/";
+    private static final Pattern RESTORE_PATH = Pattern.compile("/api/setpoints/([a-z_]{1,32})/restore");
+    /** The user name Traefik's auth forwards; anything odd falls back to the default. */
+    private static final String USER_HEADER = "Remote-User";
+    private static final String DEFAULT_USER = "phone";
+    private static final Pattern USER_NAME = Pattern.compile("[\\w.@+-]{1,64}");
+
+    private static final SecurityHeaders SECURITY_HEADERS = new SecurityHeaders();
+
+    /** A setpoint request is a few dozen bytes; anything near this is not from our UI. */
+    private static final int MAX_BODY_BYTES = 4096;
+    private static final int STOP_GRACE_SECONDS = 5;
+
+    private final HttpServer server;
+    private final ExecutorService executor = Executors.newVirtualThreadPerTaskExecutor();
+
+    /** Binds the port now; 0 picks a free one. */
+    public ApiServer(int port, HeatPumpService heatPump, EnergyService energy,
+            EnergyDetailsService energyDetails, HealthService health,
+            HistoryService history, SetpointService setpoints, PiSensorService piSensor,
+            BatteryService battery, AuditService audit, StatsService stats, WeatherService weather)
+            throws IOException {
+        server = HttpServer.create(new InetSocketAddress(port), 0);
+        server.setExecutor(executor);
+        // Everything outside the API, with the security headers too: the web UI is the frontend's (ADR-010).
+        context("/", exchange -> {
+            try (exchange) {
+                exchange.sendResponseHeaders(404, -1);
+            }
+        });
+        api("/api/heat-pump", query -> heatPump.current());
+        api("/api/energy", query -> energy.current());
+        api("/api/energy/details", query -> energyDetails.current());
+        api("/api/battery", query -> battery.current());
+        route("/api/battery/schedule", exchange -> handle(exchange, Map.of(
+                "POST", () -> guarded(exchange, body -> postSchedule(exchange, body, battery)))));
+        route("/api/battery/reserve", exchange -> handle(exchange, Map.of(
+                "POST", () -> guarded(exchange, body -> postReserve(exchange, body, battery)))));
+        api("/api/pi-sensor", query -> piSensor.current());
+        api("/api/weather", query -> weather.current());
+        api("/api/health", query -> health.current());
+        route("/api/history", exchange -> handleHistory(exchange, history));
+        route("/api/audit", exchange -> handleAudit(exchange, audit));
+        route("/api/stats", exchange -> handleStats(exchange, stats));
+        route("/api/setpoints", exchange -> handle(exchange, Map.of(
+                "GET", () -> getSetpoints(exchange, setpoints),
+                "POST", () -> guarded(exchange, body -> postSetpoint(exchange, body, setpoints)))));
+        context(SETPOINTS_PATH, exchange -> {
+            var restore = RESTORE_PATH.matcher(exchange.getRequestURI().getPath());
+            if (restore.matches()) {
+                handle(exchange, Map.of("POST", () -> guarded(exchange,
+                        body -> postRestore(exchange, restore.group(1), setpoints))));
+            } else {
+                try (exchange) {
+                    exchange.sendResponseHeaders(404, -1);
+                }
+            }
+        });
+        context(PRESETS_PATH, exchange -> handle(exchange, Map.of(
+                "POST", () -> guarded(exchange, body -> postPreset(exchange, body, setpoints)))));
+    }
+
+    /** The JDK matches a context by prefix, so /api/heat-pumpX would reach /api/heat-pump. */
+    private void route(String path, HttpHandler handler) {
+        context(path, exchange -> {
+            if (path.equals(exchange.getRequestURI().getPath())) {
+                handler.handle(exchange);
+            } else {
+                try (exchange) {
+                    exchange.sendResponseHeaders(404, -1);
+                }
+            }
+        });
+    }
+
+    private void context(String path, HttpHandler handler) {
+        server.createContext(path, handler).getFilters().add(SECURITY_HEADERS);
+    }
+
+    public void start() {
+        server.start();
+    }
+
+    public void stop() {
+        server.stop(STOP_GRACE_SECONDS);
+        executor.shutdown();
+    }
+
+    public int port() {
+        return server.getAddress().getPort();
+    }
+
+    private interface Gateway {
+        Object get(Map<String, String> query) throws IOException;
+    }
+
+    /** Gateway trouble on a live-state endpoint is the gateway being unreachable: 503. */
+    private void api(String path, Gateway gateway) {
+        route(path, exchange -> handle(exchange, Map.of("GET", () -> {
+            try {
+                send(exchange, 200, gateway.get(Map.of()));
+            } catch (IOException e) {
+                send(exchange, 503, error(UNREACHABLE));
+            }
+        })));
+    }
+
+    /**
+     * A page on another site can make the browser send a simple POST with the user's cookies. It cannot
+     * add a custom header, set a JSON content type or fake the Origin, so a write needs all three.
+     */
+    private static void guarded(HttpExchange exchange, Write write) throws IOException {
+        var headers = exchange.getRequestHeaders();
+        String origin = headers.getFirst("Origin");
+        if (origin != null && !origin.endsWith("//" + headers.getFirst("Host"))) {
+            send(exchange, 403, error("cross-site request"));
+        } else if (!WRITE_MARKER.equals(headers.getFirst("X-Requested-With"))) {
+            send(exchange, 403, error("missing X-Requested-With: " + WRITE_MARKER));
+        } else if (!isJson(headers.getFirst("Content-Type"))) {
+            send(exchange, 415, error("expected Content-Type: application/json"));
+        } else {
+            byte[] body = exchange.getRequestBody().readNBytes(MAX_BODY_BYTES + 1);
+            if (body.length > MAX_BODY_BYTES) {
+                send(exchange, 413, error("request body over " + MAX_BODY_BYTES + " bytes"));
+            } else {
+                write.run(body);
+            }
+        }
+    }
+
+    private static boolean isJson(String contentType) {
+        return contentType != null && contentType.split(";")[0].trim().equalsIgnoreCase("application/json");
+    }
+
+    private static void getSetpoints(HttpExchange exchange, SetpointService setpoints) throws IOException {
+        try {
+            send(exchange, 200, setpoints.current());
+        } catch (IOException e) {
+            send(exchange, 503, error(UNREACHABLE));
+        }
+    }
+
+    private static void postSetpoint(HttpExchange exchange, byte[] body, SetpointService setpoints)
+            throws IOException {
+        try {
+            var request = JSON.readValue(body, SetpointRequest.class);
+            if (request == null || request.setpoint() == null || request.value() == null) {
+                throw new IllegalArgumentException("setpoint and value are required");
+            }
+            var result = setpoints.apply(request.setpoint(), request.value(), request.hours(), user(exchange));
+            send(exchange, httpStatus(result.status()), result);
+        } catch (JsonProcessingException | IllegalArgumentException e) {
+            send(exchange, 400, error("expected {\"setpoint\", \"value\", \"hours\"?}"));
+        } catch (IOException e) {
+            send(exchange, 503, error(UNREACHABLE));
+        }
+    }
+
+    private static void postSchedule(HttpExchange exchange, byte[] body, BatteryService battery) throws IOException {
+        try {
+            var change = JSON.readValue(body, BatteryChange.class);
+            if (change == null) {
+                throw new IllegalArgumentException("a change is required");
+            }
+            var result = battery.changeSchedule(change, user(exchange));
+            send(exchange, batteryHttpStatus(result.status()), result);
+        } catch (JsonProcessingException | IllegalArgumentException e) {
+            send(exchange, 400, error("expected {\"enabled\"?, \"slots\": [{\"slot\", \"from\"?: \"HH:MM\", "
+                    + "\"socPct\"?, \"gridCharge\"?}]}"));
+        } catch (IOException e) {
+            send(exchange, 503, error(UNAVAILABLE));
+        }
+    }
+
+    private static void postReserve(HttpExchange exchange, byte[] body, BatteryService battery) throws IOException {
+        try {
+            var request = JSON.readValue(body, ReserveRequest.class);
+            if (request == null || request.pct() == null) {
+                throw new IllegalArgumentException("pct is required");
+            }
+            var result = battery.changeReserve(request.pct(), user(exchange));
+            send(exchange, batteryHttpStatus(result.status()), result);
+        } catch (JsonProcessingException | IllegalArgumentException e) {
+            send(exchange, 400, error("expected {\"pct\"}"));
+        } catch (IOException e) {
+            send(exchange, 503, error(UNAVAILABLE));
+        }
+    }
+
+    private static void postRestore(HttpExchange exchange, String setpoint, SetpointService setpoints)
+            throws IOException {
+        try {
+            var result = setpoints.restore(setpoint, user(exchange));
+            send(exchange, restoreHttpStatus(result.outcome()), result);
+        } catch (IOException e) {
+            send(exchange, 503, error(UNREACHABLE));
+        }
+    }
+
+    private static void postPreset(HttpExchange exchange, byte[] body, SetpointService setpoints)
+            throws IOException {
+        String id = exchange.getRequestURI().getPath().substring(PRESETS_PATH.length());
+        try {
+            var request = body.length == 0 ? new PresetRequest(null, null) : JSON.readValue(body, PresetRequest.class);
+            var until = request.until() == null ? null : OffsetDateTime.parse(request.until()).toInstant();
+            var result = setpoints.applyPreset(id, until, request.values(), user(exchange));
+            if (result.isPresent()) {
+                send(exchange, presetHttpStatus(result.get().status()), result.get());
+            } else {
+                send(exchange, 404, error("no such preset"));
+            }
+        } catch (JsonProcessingException | DateTimeParseException | IllegalArgumentException e) {
+            send(exchange, 400, error("expected {\"until\": \"2026-11-02T18:00:00+01:00\"} for a preset that needs "
+                    + "an end time, else no body; optional \"values\": {\"cwu_comfort\": 12} within the limits "
+                    + "for setpoints of the preset"));
+        } catch (IOException e) {
+            send(exchange, 503, error(UNREACHABLE));
+        }
+    }
+
+    private static int httpStatus(Status status) {
+        return switch (status) {
+            case APPLIED -> 200;
+            case REJECTED -> 422;
+            case FAILED -> 502;
+        };
+    }
+
+    private static int batteryHttpStatus(BatteryResult.Status status) {
+        return switch (status) {
+            case APPLIED -> 200;
+            case REJECTED -> 422;
+            case STALE -> 409;
+            case TOO_SOON -> 429;
+            case FAILED -> 502;
+        };
+    }
+
+    private static int restoreHttpStatus(RestoreResult.Outcome outcome) {
+        return switch (outcome) {
+            case RESTORED -> 200;
+            case NOT_PENDING -> 404;
+            case CONFLICT -> 409;
+            case TOO_SOON -> 429;
+            case FAILED -> 502;
+        };
+    }
+
+    private static int presetHttpStatus(PresetResult.Status status) {
+        return switch (status) {
+            case APPLIED -> 200;
+            case REJECTED -> 422;
+            case FAILED, PARTIAL -> 502;
+        };
+    }
+
+    private static String user(HttpExchange exchange) {
+        String name = exchange.getRequestHeaders().getFirst(USER_HEADER);
+        return name != null && USER_NAME.matcher(name).matches() ? name : DEFAULT_USER;
+    }
+
+    private void handleHistory(HttpExchange exchange, HistoryService history) throws IOException {
+        handle(exchange, Map.of("GET", () -> {
+            Map<String, String> query = parseQuery(exchange.getRequestURI().getRawQuery());
+            try {
+                send(exchange, 200, history.history(query.get("series"), query.get("range")));
+            } catch (IllegalArgumentException e) {
+                send(exchange, 400, error(e.getMessage()));
+            } catch (IOException e) {
+                send(exchange, 502, error("history unavailable"));
+            }
+        }));
+    }
+
+    private void handleAudit(HttpExchange exchange, AuditService audit) throws IOException {
+        handle(exchange, Map.of("GET", () -> {
+            Map<String, String> query = parseQuery(exchange.getRequestURI().getRawQuery());
+            try {
+                send(exchange, 200, audit.audit(query.get("range")));
+            } catch (IllegalArgumentException e) {
+                send(exchange, 400, error(e.getMessage()));
+            } catch (IOException e) {
+                send(exchange, 502, error("audit unavailable"));
+            }
+        }));
+    }
+
+    private void handleStats(HttpExchange exchange, StatsService stats) throws IOException {
+        handle(exchange, Map.of("GET", () -> {
+            try {
+                send(exchange, 200, stats.stats(parseQuery(exchange.getRequestURI().getRawQuery()).get("range")));
+            } catch (IllegalArgumentException e) {
+                send(exchange, 400, error(e.getMessage()));
+            } catch (IOException e) {
+                send(exchange, 502, error("stats unavailable"));
+            }
+        }));
+    }
+
+    private interface Action {
+        void run() throws IOException;
+    }
+
+    private interface Write {
+        void run(byte[] body) throws IOException;
+    }
+
+    private static void handle(HttpExchange exchange, Map<String, Action> byMethod) throws IOException {
+        try (exchange) {
+            Action action = byMethod.get(exchange.getRequestMethod());
+            if (action == null) {
+                exchange.sendResponseHeaders(405, -1);
+                return;
+            }
+            try {
+                action.run();
+            } catch (RuntimeException e) {
+                // A gateway payload the client could not map (duplicate device, missing status): answer, do not drop.
+                System.err.println("home-pump-backend: " + exchange.getRequestURI().getPath() + ": " + e);
+                if (exchange.getResponseCode() == -1) {
+                    send(exchange, 502, error("bad gateway response"));
+                }
+            }
+        }
+    }
+
+    private static void send(HttpExchange exchange, int status, Object body) throws IOException {
+        byte[] bytes = JSON.writeValueAsBytes(body);
+        exchange.getResponseHeaders().set("Content-Type", "application/json");
+        exchange.getResponseHeaders().set("Cache-Control", "no-store");
+        exchange.sendResponseHeaders(status, bytes.length);
+        exchange.getResponseBody().write(bytes);
+    }
+
+    private static Map<String, String> error(String message) {
+        return Map.of("error", message);
+    }
+
+    private static Map<String, String> parseQuery(String raw) {
+        Map<String, String> query = new HashMap<>();
+        if (raw == null) {
+            return query;
+        }
+        for (String pair : raw.split("&")) {
+            String[] kv = pair.split("=", 2);
+            query.put(decode(kv[0]), kv.length == 2 ? decode(kv[1]) : "");
+        }
+        return query;
+    }
+
+    private static String decode(String s) {
+        return URLDecoder.decode(s, StandardCharsets.UTF_8);
+    }
+}

backend/src/main/java/home/backend/adapters/http/SecurityHeaders.java

@@ -0,0 +1,28 @@
+package home.backend.adapters.http;
+
+import com.sun.net.httpserver.Filter;
+import com.sun.net.httpserver.HttpExchange;
+
+import java.io.IOException;
+
+/** Sets the browser hardening headers on every response, whatever handler answers. */
+final class SecurityHeaders extends Filter {
+
+    private static final String POLICY = "default-src 'none'; script-src 'self'; style-src 'self'; "
+            + "img-src 'self' data:; font-src 'self'; connect-src 'self'; base-uri 'none'; "
+            + "form-action 'self'; frame-ancestors 'none'";
+
+    @Override
+    public void doFilter(HttpExchange exchange, Chain chain) throws IOException {
+        var headers = exchange.getResponseHeaders();
+        headers.set("Content-Security-Policy", POLICY);
+        headers.set("X-Content-Type-Options", "nosniff");
+        headers.set("Referrer-Policy", "no-referrer");
+        chain.doFilter(exchange);
+    }
+
+    @Override
+    public String description() {
+        return "security headers";
+    }
+}

backend/src/main/java/home/backend/adapters/influx/InfluxAuditRepository.java

@@ -0,0 +1,88 @@
+package home.backend.adapters.influx;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import home.backend.application.AuditRepository;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/** The gateway's audit measurements (S3) read from InfluxDB; never written. */
+public final class InfluxAuditRepository implements AuditRepository {
+
+    private static final ObjectMapper JSON = new ObjectMapper();
+
+    private final InfluxClient influx;
+
+    public InfluxAuditRepository(InfluxSettings settings) {
+        this.influx = new InfluxClient(settings);
+    }
+
+    @Override
+    public List<Row> heatPump(Instant from, Instant to) throws IOException {
+        return rows("Dom_Pompa", "setpoint_audit", "setpoint", from, to);
+    }
+
+    @Override
+    public List<Row> battery(Instant from, Instant to) throws IOException {
+        return rows("electricity", "deye_settings_audit", "register", from, to);
+    }
+
+    private List<Row> rows(String database, String measurement, String targetTag, Instant from, Instant to)
+            throws IOException {
+        String query = "SELECT * FROM \"" + measurement + "\" WHERE time >= " + from.toEpochMilli()
+                + "ms AND time < " + to.toEpochMilli() + "ms ORDER BY time DESC";
+        var rows = new ArrayList<Row>();
+        for (JsonNode result : results(influx.query(database, query))) {
+            for (JsonNode series : result.path("series")) {
+                for (JsonNode values : series.path("values")) {
+                    rows.add(row(series.path("columns"), values, targetTag));
+                }
+            }
+        }
+        return rows;
+    }
+
+    private static JsonNode results(String body) throws IOException {
+        JsonNode root;
+        try {
+            root = JSON.readTree(body);
+        } catch (JsonProcessingException e) {
+            throw new IOException("InfluxDB returned invalid JSON: " + e.getOriginalMessage(), e);
+        }
+        failOnError(root);
+        for (JsonNode result : root.path("results")) {
+            failOnError(result);
+        }
+        return root.path("results");
+    }
+
+    private static void failOnError(JsonNode node) throws IOException {
+        if (node.hasNonNull("error")) {
+            throw new IOException("InfluxDB query failed: " + node.get("error").asText());
+        }
+    }
+
+    private static Row row(JsonNode columns, JsonNode values, String targetTag) {
+        Map<String, JsonNode> byName = new HashMap<>();
+        for (int i = 0; i < columns.size(); i++) {
+            byName.put(columns.get(i).asText(), values.get(i));
+        }
+        return new Row(Instant.ofEpochMilli(byName.get("time").asLong()), text(byName.get(targetTag)),
+                text(byName.get("requested_by")), text(byName.get("status")),
+                number(byName.get("old_value")), number(byName.get("new_value")));
+    }
+
+    private static String text(JsonNode node) {
+        return node == null || node.isNull() ? "" : node.asText();
+    }
+
+    private static Double number(JsonNode node) {
+        return node == null || !node.isNumber() ? null : node.asDouble();
+    }
+}

backend/src/main/java/home/backend/adapters/influx/InfluxClient.java

@@ -0,0 +1,47 @@
+package home.backend.adapters.influx;
+
+import java.io.IOException;
+import java.net.URI;
+import java.net.URLEncoder;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.nio.charset.StandardCharsets;
+
+/** Read-only queries to InfluxDB 1.x over its HTTP {@code /query} endpoint; times come back in epoch ms. */
+final class InfluxClient {
+
+    private final InfluxSettings settings;
+    private final HttpClient http;
+
+    InfluxClient(InfluxSettings settings) {
+        this.settings = settings;
+        this.http = HttpClient.newBuilder().connectTimeout(settings.requestTimeout()).build();
+    }
+
+    String query(String database, String query) throws IOException {
+        HttpRequest request = HttpRequest.newBuilder(queryUri(database, query))
+                .timeout(settings.requestTimeout())
+                .GET()
+                .build();
+        try {
+            HttpResponse<String> response = http.send(request, HttpResponse.BodyHandlers.ofString());
+            if (response.statusCode() != 200) {
+                throw new IOException("InfluxDB answered HTTP " + response.statusCode());
+            }
+            return response.body();
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+            throw new IOException("InfluxDB request interrupted", e);
+        }
+    }
+
+    private URI queryUri(String database, String query) {
+        String base = settings.baseUri().toString().replaceAll("/+$", "");
+        return URI.create(base + "/query?db=" + encode(database) + "&epoch=ms&q=" + encode(query));
+    }
+
+    private static String encode(String value) {
+        return URLEncoder.encode(value, StandardCharsets.UTF_8);
+    }
+}

backend/src/main/java/home/backend/adapters/influx/InfluxHistoryRepository.java

@@ -0,0 +1,69 @@
+package home.backend.adapters.influx;
+
+import home.backend.application.HeatPumpSamples;
+import home.backend.application.HistoryRepository;
+import home.backend.domain.HeatPumpSample;
+import home.backend.domain.HistoryView.Point;
+import home.backend.domain.Series;
+
+import java.io.IOException;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Executors;
+
+/** History from InfluxDB 1.x over its HTTP {@code /query} endpoint (ADR-005, ADR-008). */
+public final class InfluxHistoryRepository implements HistoryRepository, HeatPumpSamples {
+
+    private final InfluxClient influx;
+
+    public InfluxHistoryRepository(InfluxSettings settings) {
+        this.influx = new InfluxClient(settings);
+    }
+
+    @Override
+    public List<Point> history(Series series, Instant from, Instant to, int maxPoints) throws IOException {
+        if (maxPoints < 1 || !from.isBefore(to)) {
+            throw new IllegalArgumentException("need maxPoints >= 1 and from < to");
+        }
+        long stepMinutes = stepMinutes(from, to, maxPoints);
+        Map<Long, Double> summed = new TreeMap<>();
+        try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
+            var parts = SeriesSources.of(series).stream()
+                    .map(source -> executor.submit(() -> part(source, from, to, stepMinutes)))
+                    .toList();
+            // Summed in source order, so the result does not depend on which answer comes first.
+            for (var part : parts) {
+                // A part without data is absent, not zero, so a bucket is kept if any part has it.
+                part.get().forEach((t, v) -> summed.merge(t, v, Double::sum));
+            }
+        } catch (ExecutionException e) {
+            throw e.getCause() instanceof IOException io ? io : new IOException(e.getCause());
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+            throw new IOException("InfluxDB request interrupted", e);
+        }
+        return summed.entrySet().stream()
+                .map(e -> new Point(Instant.ofEpochMilli(e.getKey()), e.getValue()))
+                .toList();
+    }
+
+    @Override
+    public List<HeatPumpSample> samples(Instant from, Instant to) throws IOException {
+        String query = InfluxSamples.query(from.toEpochMilli(), to.toEpochMilli());
+        return InfluxSamples.parse(influx.query(SeriesSources.LEGACY, query));
+    }
+
+    private Map<Long, Double> part(Source source, Instant from, Instant to, long stepMinutes) throws IOException {
+        String query = source.query(from.toEpochMilli(), to.toEpochMilli(), stepMinutes);
+        return InfluxResponse.parse(influx.query(source.database(), query));
+    }
+
+    private static long stepMinutes(Instant from, Instant to, int maxPoints) {
+        long stepMillis = Math.ceilDiv(Duration.between(from, to).toMillis(), maxPoints);
+        return Math.max(1, Math.ceilDiv(stepMillis, Duration.ofMinutes(1).toMillis()));
+    }
+}

backend/src/main/java/home/backend/adapters/influx/InfluxPvEnergy.java

@@ -0,0 +1,51 @@
+package home.backend.adapters.influx;
+
+import home.backend.application.PvEnergyRepository;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.time.LocalDate;
+import java.time.ZoneId;
+import java.util.Map;
+import java.util.TreeMap;
+
+/** Daily PV energy: the Deye's and the Fronius's own day counters, each read as the day's maximum. */
+public final class InfluxPvEnergy implements PvEnergyRepository {
+
+    private static final ZoneId ZONE = ZoneId.of("Europe/Warsaw");
+    private static final String DATABASE = "electricity";
+
+    private final InfluxClient influx;
+
+    public InfluxPvEnergy(InfluxSettings settings) {
+        this.influx = new InfluxClient(settings);
+    }
+
+    @Override
+    public Map<LocalDate, Double> dailyKwh(LocalDate from, LocalDate to) throws IOException {
+        Map<LocalDate, Double> deye = dailyMax("deye", "pv_today_kwh", from, to);
+        Map<LocalDate, Double> fronius = dailyMax("fronius", "energy_day_wh", from, to);
+        Map<LocalDate, Double> total = new TreeMap<>();
+        deye.forEach((day, kwh) -> {
+            Double wh = fronius.get(day);
+            if (wh != null) {
+                total.put(day, kwh + wh / 1000);
+            }
+        });
+        return total;
+    }
+
+    private Map<LocalDate, Double> dailyMax(String measurement, String field, LocalDate from, LocalDate to)
+            throws IOException {
+        String query = "SELECT max(\"" + field + "\") FROM \"" + measurement + "\" WHERE time >= "
+                + millis(from) + "ms AND time < " + millis(to) + "ms GROUP BY time(1d) fill(none) tz('Europe/Warsaw')";
+        Map<LocalDate, Double> days = new TreeMap<>();
+        InfluxResponse.parse(influx.query(DATABASE, query)).forEach((start, max) ->
+                days.put(Instant.ofEpochMilli(start).atZone(ZONE).toLocalDate(), max));
+        return days;
+    }
+
+    private static long millis(LocalDate day) {
+        return day.atStartOfDay(ZONE).toInstant().toEpochMilli();
+    }
+}

backend/src/main/java/home/backend/adapters/influx/InfluxResponse.java

@@ -0,0 +1,50 @@
+package home.backend.adapters.influx;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.TreeMap;
+
+/** The {@code time, mean} rows of an InfluxDB 1.x query response. */
+final class InfluxResponse {
+
+    private static final ObjectMapper JSON = new ObjectMapper();
+
+    private InfluxResponse() {
+    }
+
+    /** Mean per bucket start in epoch milliseconds, ascending; empty when there is no data. */
+    static Map<Long, Double> parse(String body) throws IOException {
+        JsonNode root = read(body);
+        failOnError(root);
+        Map<Long, Double> means = new TreeMap<>();
+        for (JsonNode result : root.path("results")) {
+            failOnError(result);
+            for (JsonNode series : result.path("series")) {
+                for (JsonNode row : series.path("values")) {
+                    if (row.size() >= 2 && row.get(1).isNumber()) {
+                        means.put(row.get(0).asLong(), row.get(1).asDouble());
+                    }
+                }
+            }
+        }
+        return means;
+    }
+
+    private static JsonNode read(String body) throws IOException {
+        try {
+            return JSON.readTree(body);
+        } catch (JsonProcessingException e) {
+            throw new IOException("InfluxDB returned invalid JSON: " + e.getOriginalMessage(), e);
+        }
+    }
+
+    private static void failOnError(JsonNode node) throws IOException {
+        if (node.hasNonNull("error")) {
+            throw new IOException("InfluxDB query failed: " + node.get("error").asText());
+        }
+    }
+}

backend/src/main/java/home/backend/adapters/influx/InfluxSamples.java

@@ -0,0 +1,58 @@
+package home.backend.adapters.influx;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import home.backend.domain.HeatPumpSample;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.List;
+
+/** The raw {@code heat_pump} rows of an InfluxDB 1.x query. */
+final class InfluxSamples {
+
+    private static final ObjectMapper JSON = new ObjectMapper();
+
+    private InfluxSamples() {
+    }
+
+    static String query(long fromMs, long toMs) {
+        return "SELECT output_compressor, output_cwu, output_co, output_heater, outdoor_temp, cwu_temp"
+                + " FROM \"heat_pump\" WHERE time >= " + fromMs + "ms AND time < " + toMs + "ms";
+    }
+
+    /** The rows of {@link #query}, as returned (ascending); empty when there is no data. */
+    static List<HeatPumpSample> parse(String body) throws IOException {
+        JsonNode root;
+        try {
+            root = JSON.readTree(body);
+        } catch (JsonProcessingException e) {
+            throw new IOException("InfluxDB returned invalid JSON: " + e.getOriginalMessage(), e);
+        }
+        failOnError(root);
+        List<HeatPumpSample> samples = new ArrayList<>();
+        for (JsonNode result : root.path("results")) {
+            failOnError(result);
+            for (JsonNode series : result.path("series")) {
+                for (JsonNode row : series.path("values")) {
+                    samples.add(new HeatPumpSample(Instant.ofEpochMilli(row.get(0).asLong()),
+                            number(row, 1), number(row, 2), number(row, 3), number(row, 4),
+                            number(row, 5), number(row, 6)));
+                }
+            }
+        }
+        return samples;
+    }
+
+    private static Double number(JsonNode row, int column) {
+        return row.get(column).isNumber() ? row.get(column).asDouble() : null;
+    }
+
+    private static void failOnError(JsonNode node) throws IOException {
+        if (node.hasNonNull("error")) {
+            throw new IOException("InfluxDB query failed: " + node.get("error").asText());
+        }
+    }
+}

backend/src/main/java/home/backend/adapters/influx/InfluxSettings.java

@@ -0,0 +1,7 @@
+package home.backend.adapters.influx;
+
+import java.net.URI;
+import java.time.Duration;
+
+public record InfluxSettings(URI baseUri, Duration requestTimeout) {
+}

backend/src/main/java/home/backend/adapters/influx/SeriesSources.java

@@ -0,0 +1,44 @@
+package home.backend.adapters.influx;
+
+import home.backend.domain.Series;
+
+import java.util.List;
+import java.util.Map;
+
+/** Where each series lives in InfluxDB. A fixed table: no query is built from user input. */
+final class SeriesSources {
+
+    static final String LEGACY = "Dom_Pompa";
+    private static final String ELECTRICITY = "electricity";
+
+    private static final Map<Series, List<Source>> SOURCES = Map.ofEntries(
+            Map.entry(Series.OUTDOOR_TEMP, List.of(pompa("External temperature"))),
+            Map.entry(Series.INDOOR_TEMP, List.of(pompa("Temp wew"))),
+            Map.entry(Series.CO_BUFFER_TEMP, List.of(pompa("Temp co"))),
+            Map.entry(Series.CWU_TEMP, List.of(pompa("Temp cwu"))),
+            Map.entry(Series.GROUND_IN_TEMP, List.of(pompa("Temp in"))),
+            Map.entry(Series.GROUND_OUT_TEMP, List.of(pompa("Temp out"))),
+            Map.entry(Series.PUMP_OUTLET_TEMP, List.of(pompa("Temp pc out"))),
+            Map.entry(Series.GRID_POWER, List.of(electricity("PRAD2", "total_power_active"))),
+            Map.entry(Series.PV_POWER, List.of(
+                    electricity("deye", "pv1_power_w"),
+                    electricity("deye", "pv2_power_w"),
+                    electricity("fronius", "pv_power_w"))),
+            Map.entry(Series.LOAD_POWER, List.of(electricity("deye", "load_power_w"))),
+            Map.entry(Series.BATTERY_SOC, List.of(electricity("deye", "battery_soc_pct"))));
+
+    private SeriesSources() {
+    }
+
+    static List<Source> of(Series series) {
+        return SOURCES.get(series);
+    }
+
+    private static Source pompa(String field) {
+        return new Source(LEGACY, "POMPA", field);
+    }
+
+    private static Source electricity(String measurement, String field) {
+        return new Source(ELECTRICITY, measurement, field);
+    }
+}

backend/src/main/java/home/backend/adapters/influx/Source.java

@@ -0,0 +1,15 @@
+package home.backend.adapters.influx;
+
+/** One field of one measurement; the parts of a series are summed. */
+record Source(String database, String measurement, String field) {
+
+    String query(long fromMs, long toMs, long stepMinutes) {
+        return "SELECT mean(" + quote(field) + ") FROM " + quote(measurement)
+                + " WHERE time >= " + fromMs + "ms AND time < " + toMs + "ms"
+                + " GROUP BY time(" + stepMinutes + "m) fill(none)";
+    }
+
+    private static String quote(String identifier) {
+        return '"' + identifier.replace("\\", "\\\\").replace("\"", "\\\"") + '"';
+    }
+}

backend/src/main/java/home/backend/adapters/weather/HttpJson.java

@@ -0,0 +1,42 @@
+package home.backend.adapters.weather;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import java.io.IOException;
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.time.Duration;
+
+/** GET of a public JSON document, with a timeout on connecting and on the whole request. */
+final class HttpJson {
+
+    private static final ObjectMapper JSON = new ObjectMapper();
+
+    private final HttpClient http;
+    private final Duration timeout;
+
+    HttpJson(Duration timeout) {
+        this.http = HttpClient.newBuilder().connectTimeout(timeout).build();
+        this.timeout = timeout;
+    }
+
+    JsonNode get(URI uri) throws IOException {
+        HttpRequest request = HttpRequest.newBuilder(uri).timeout(timeout).GET().build();
+        try {
+            HttpResponse<String> response = http.send(request, HttpResponse.BodyHandlers.ofString());
+            if (response.statusCode() != 200) {
+                throw new IOException(uri.getHost() + " answered HTTP " + response.statusCode());
+            }
+            return JSON.readTree(response.body());
+        } catch (JsonProcessingException e) {
+            throw new IOException(uri.getHost() + " returned invalid JSON: " + e.getOriginalMessage(), e);
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+            throw new IOException("request to " + uri.getHost() + " interrupted", e);
+        }
+    }
+}

backend/src/main/java/home/backend/adapters/weather/ImgwClient.java

@@ -0,0 +1,76 @@
+package home.backend.adapters.weather;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import home.backend.application.WarningSource;
+import home.backend.domain.WeatherView.Warning;
+
+import java.io.IOException;
+import java.net.URI;
+import java.time.DateTimeException;
+import java.time.Duration;
+import java.time.LocalDateTime;
+import java.time.OffsetDateTime;
+import java.time.ZoneId;
+import java.time.format.DateTimeFormatter;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+
+/**
+ * IMGW's public list of meteorological warnings, kept to those naming one of our TERYT areas. A warning
+ * that is malformed (no degree or times) is left out rather than failing the others.
+ */
+public final class ImgwClient implements WarningSource {
+
+    private static final ZoneId POLAND = ZoneId.of("Europe/Warsaw");
+    private static final DateTimeFormatter TIME = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
+
+    private final HttpJson http;
+    private final URI uri;
+    private final List<String> teryt;
+
+    public ImgwClient(URI baseUri, WeatherSettings place, Duration timeout) {
+        this.http = new HttpJson(timeout);
+        this.uri = URI.create(baseUri.toString().replaceAll("/+$", "") + "/api/data/warningsmeteo");
+        this.teryt = place.teryt();
+    }
+
+    @Override
+    public List<Warning> warnings() throws IOException {
+        JsonNode root = http.get(uri);
+        if (!root.isArray()) {
+            throw new IOException("IMGW returned no list of warnings");
+        }
+        List<Warning> ours = new ArrayList<>();
+        for (JsonNode item : root) {
+            if (covers(item.path("teryt"))) {
+                warning(item).ifPresent(ours::add);
+            }
+        }
+        return ours;
+    }
+
+    private boolean covers(JsonNode codes) {
+        for (JsonNode code : codes) {
+            if (teryt.contains(code.asText())) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private static Optional<Warning> warning(JsonNode item) {
+        try {
+            return Optional.of(new Warning(item.path("nazwa_zdarzenia").asText(),
+                    Integer.parseInt(item.path("stopien").asText()),
+                    time(item.path("obowiazuje_od")), time(item.path("obowiazuje_do")),
+                    item.path("tresc").asText()));
+        } catch (NumberFormatException | DateTimeException e) {
+            return Optional.empty();
+        }
+    }
+
+    private static OffsetDateTime time(JsonNode text) {
+        return LocalDateTime.parse(text.asText(), TIME).atZone(POLAND).toOffsetDateTime();
+    }
+}

backend/src/main/java/home/backend/adapters/weather/OpenMeteoClient.java

@@ -0,0 +1,68 @@
+package home.backend.adapters.weather;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import home.backend.application.ForecastSource;
+import home.backend.domain.Forecast;
+import home.backend.domain.Forecast.DailyForecast;
+
+import java.io.IOException;
+import java.net.URI;
+import java.time.DateTimeException;
+import java.time.Duration;
+import java.time.LocalDate;
+import java.util.Map;
+import java.util.TreeMap;
+
+/** Open-Meteo (free, no key): daily values for the past 14 days and the next 3, and the temperature now. */
+public final class OpenMeteoClient implements ForecastSource {
+
+    private static final String DAILY = "weather_code,temperature_2m_max,temperature_2m_min,precipitation_sum,"
+            + "shortwave_radiation_sum,sunshine_duration";
+
+    private final HttpJson http;
+    private final URI uri;
+
+    public OpenMeteoClient(URI baseUri, WeatherSettings place, Duration timeout) {
+        this.http = new HttpJson(timeout);
+        this.uri = URI.create(baseUri.toString().replaceAll("/+$", "") + "/v1/forecast?latitude="
+                + place.latitude() + "&longitude=" + place.longitude() + "&daily=" + DAILY
+                + "&current=temperature_2m&timezone=Europe%2FWarsaw&past_days=14&forecast_days=3");
+    }
+
+    @Override
+    public Forecast forecast() throws IOException {
+        JsonNode root = http.get(uri);
+        JsonNode daily = root.path("daily");
+        JsonNode dates = daily.path("time");
+        if (!dates.isArray() || dates.isEmpty()) {
+            throw new IOException("Open-Meteo returned no daily forecast");
+        }
+        Map<LocalDate, DailyForecast> days = new TreeMap<>();
+        for (int i = 0; i < dates.size(); i++) {
+            days.put(date(dates.get(i).asText()), new DailyForecast(
+                    integer(daily, "weather_code", i), number(daily, "temperature_2m_max", i),
+                    number(daily, "temperature_2m_min", i), number(daily, "precipitation_sum", i),
+                    number(daily, "shortwave_radiation_sum", i), number(daily, "sunshine_duration", i)));
+        }
+        JsonNode now = root.path("current").path("temperature_2m");
+        return new Forecast(now.isNumber() ? now.asDouble() : null, days);
+    }
+
+    private static LocalDate date(String text) throws IOException {
+        try {
+            return LocalDate.parse(text);
+        } catch (DateTimeException e) {
+            throw new IOException("Open-Meteo returned a bad date: " + text, e);
+        }
+    }
+
+    private static Double number(JsonNode daily, String name, int i) {
+        JsonNode value = daily.path(name).path(i);
+        return value.isNumber() ? value.asDouble() : null;
+    }
+
+    private static Integer integer(JsonNode daily, String name, int i) {
+        JsonNode value = daily.path(name).path(i);
+        return value.isNumber() ? value.asInt() : null;
+    }
+}

backend/src/main/java/home/backend/adapters/weather/WeatherSettings.java

@@ -0,0 +1,35 @@
+package home.backend.adapters.weather;
+
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Where the house is and which IMGW areas (TERYT powiat codes) count as ours. Krosno is a city with
+ * powiat rights, 1862; 1807 is the surrounding powiat krośnieński, which warnings may name instead.
+ */
+public record WeatherSettings(double latitude, double longitude, List<String> teryt) {
+
+    public static WeatherSettings fromEnvironment(Map<String, String> env) {
+        return new WeatherSettings(
+                coordinate(env, "WEATHER_LAT", 49.684, 90),
+                coordinate(env, "WEATHER_LON", 21.770, 180),
+                List.of(env.getOrDefault("WEATHER_TERYT", "1862,1807").strip().split("\\s*,\\s*")));
+    }
+
+    private static double coordinate(Map<String, String> env, String name, double fallback, double limit) {
+        String value = env.get(name);
+        if (value == null || value.isBlank()) {
+            return fallback;
+        }
+        try {
+            double number = Double.parseDouble(value.strip());
+            if (Math.abs(number) <= limit) {
+                return number;
+            }
+        } catch (NumberFormatException e) {
+            // reported below with the same message
+        }
+        throw new IllegalArgumentException(name + " must be a number from -" + limit + " to " + limit
+                + ", got: " + value);
+    }
+}

backend/src/main/java/home/backend/application/AuditRepository.java

@@ -0,0 +1,17 @@
+package home.backend.application;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.List;
+
+/** The gateway's audit rows in InfluxDB (S3), read only. */
+public interface AuditRepository {
+
+    /** One audited write as recorded; {@code target} is the setpoint name or the Deye register. */
+    record Row(Instant time, String target, String requestedBy, String status, Double oldValue, Double newValue) {
+    }
+
+    List<Row> heatPump(Instant from, Instant to) throws IOException;
+
+    List<Row> battery(Instant from, Instant to) throws IOException;
+}

backend/src/main/java/home/backend/application/AuditService.java

@@ -0,0 +1,70 @@
+package home.backend.application;
+
+import home.backend.application.AuditRepository.Row;
+import home.backend.domain.AuditEntry;
+import home.backend.domain.AuditView;
+
+import java.io.IOException;
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.Comparator;
+import java.util.Map;
+import java.util.stream.Stream;
+
+/** S3: who changed what and when, from the gateway's audit rows of the heat pump and of the battery. */
+public class AuditService {
+
+    private static final String DEFAULT_RANGE = "7d";
+    private static final Map<String, Duration> RANGES =
+            Map.of("24h", Duration.ofHours(24), "7d", Duration.ofDays(7), "30d", Duration.ofDays(30));
+    private static final Map<String, String> SETPOINTS = Map.of(
+            "cwu_economy", "CWU eko", "cwu_comfort", "CWU komfort",
+            "co_economy", "CO eko", "co_comfort", "CO komfort");
+    private static final String RESTORE_USER = "restore";
+    private static final String RESTORE_LABEL = "automatycznie (przywrócenie)";
+
+    private final AuditRepository repository;
+    private final Clock clock;
+
+    public AuditService(AuditRepository repository, Clock clock) {
+        this.repository = repository;
+        this.clock = clock;
+    }
+
+    /**
+     * @param range {@code 24h}, {@code 7d} or {@code 30d}; null means 7d
+     * @throws IllegalArgumentException for an unknown range
+     */
+    public AuditView audit(String range) throws IOException {
+        Duration length = RANGES.get(range == null ? DEFAULT_RANGE : range);
+        if (length == null) {
+            throw new IllegalArgumentException("unknown range: " + range);
+        }
+        Instant to = clock.instant();
+        Instant from = to.minus(length);
+        var heatPump = repository.heatPump(from, to).stream().map(AuditService::heatPumpEntry);
+        var battery = repository.battery(from, to).stream().map(AuditService::batteryEntry);
+        return new AuditView(Stream.concat(heatPump, battery)
+                .sorted(Comparator.comparing(AuditEntry::time).reversed())
+                .toList());
+    }
+
+    private static AuditEntry heatPumpEntry(Row row) {
+        return entry(AuditEntry.HEAT_PUMP, row, SETPOINTS.getOrDefault(row.target(), row.target()), "°C");
+    }
+
+    private static AuditEntry batteryEntry(Row row) {
+        var label = DeyeSettingLabels.of(row.target());
+        return entry(AuditEntry.BATTERY, row, label.what(), label.unit());
+    }
+
+    private static AuditEntry entry(String source, Row row, String what, String unit) {
+        return new AuditEntry(row.time(), source, what, whole(row.oldValue()), whole(row.newValue()), unit,
+                RESTORE_USER.equals(row.requestedBy()) ? RESTORE_LABEL : row.requestedBy(), row.status());
+    }
+
+    private static Integer whole(Double value) {
+        return value == null ? null : (int) Math.round(value);
+    }
+}

backend/src/main/java/home/backend/application/BatteryService.java

@@ -0,0 +1,109 @@
+package home.backend.application;
+
+import home.backend.application.SnapshotFields.Live;
+import home.backend.domain.BatteryChange;
+import home.backend.domain.BatteryResult;
+import home.backend.domain.BatteryView;
+import home.backend.domain.BatteryView.Energy;
+import home.backend.domain.BatteryView.Limits;
+import home.backend.domain.BatteryView.Mode;
+import home.backend.domain.BatteryView.Reserve;
+import home.backend.domain.BatteryView.Slot;
+import home.backend.domain.GatewaySnapshot;
+
+import java.io.IOException;
+import java.time.Clock;
+import java.time.Duration;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.IntStream;
+
+import static home.backend.application.SnapshotFields.on;
+import static home.backend.application.SnapshotFields.whole;
+
+/** F7: the Deye's battery now, and how it is set up. */
+public class BatteryService {
+
+    /** The settings are read every 10 minutes; three missed reads and they are not current. */
+    private static final Duration SETTINGS_MAX_AGE = Duration.ofMinutes(30);
+    private static final int SLOTS = 6;
+    /** The nominal voltage of a 16-cell lithium pack; the Deye reports capacity in Ah only. */
+    private static final double NOMINAL_VOLTS = 51.2;
+
+    private final GatewayClient gateway;
+    private final GatewayBattery battery;
+    private final Clock clock;
+
+    public BatteryService(GatewayClient gateway, GatewayBattery battery, Clock clock) {
+        this.gateway = gateway;
+        this.battery = battery;
+        this.clock = clock;
+    }
+
+    public BatteryResult changeSchedule(BatteryChange change, String user) throws IOException {
+        return battery.changeSchedule(change, user);
+    }
+
+    public BatteryResult changeReserve(int pct, String user) throws IOException {
+        return battery.changeReserve(pct, user);
+    }
+
+    /** Asked on its own: a gateway without battery commands still serves the live view. */
+    private Reserve reserve() {
+        try {
+            return battery.reserve();
+        } catch (IOException e) {
+            return null;
+        }
+    }
+
+    public BatteryView current() throws IOException {
+        GatewaySnapshot snapshot = gateway.snapshot();
+        Live deye = SnapshotFields.live(snapshot, "deye", "deye", clock.instant());
+        Live settings = SnapshotFields.live(snapshot, "deye-settings", "deye_settings", clock.instant(),
+                SETTINGS_MAX_AGE);
+        Map<String, Double> d = deye.fields();
+        Map<String, Double> s = settings.fields();
+        boolean settingsStale = settings.source().stale();
+        Reserve reserve = reserve();
+        return new BatteryView(deye.source().time(), deye.source().stale(),
+                d.get("battery_soc_pct"), d.get("battery_power_w"), d.get("battery_voltage_v"),
+                d.get("battery_current_a"), d.get("battery_temperature_c"), capacityKwh(s),
+                new Energy(d.get("battery_charge_today_kwh"), d.get("battery_discharge_today_kwh")),
+                new Energy(d.get("battery_charge_total_kwh"), d.get("battery_discharge_total_kwh")),
+                settingsStale ? null : mode(s), settingsStale ? List.of() : schedule(s),
+                settingsStale ? null : limits(s), settings.source().time(), settingsStale, reserve, reserve != null);
+    }
+
+    private static Double capacityKwh(Map<String, Double> settings) {
+        Double ah = settings.get("battery_capacity_ah");
+        return ah == null ? null : Math.round(ah * NOMINAL_VOLTS) / 1000.0;
+    }
+
+    private static Mode mode(Map<String, Double> s) {
+        boolean tou = on(s, "tou_enabled");
+        return new Mode(tou, tou ? "Harmonogram: bateria pracuje według przedziałów"
+                : "Rezerwa na awarię: bateria nie rozładowuje się na co dzień");
+    }
+
+    /** Slot n runs from its start to the start of slot n + 1; the last one wraps to the first. */
+    private static List<Slot> schedule(Map<String, Double> s) {
+        return IntStream.rangeClosed(1, SLOTS).mapToObj(n -> {
+            String prefix = "prog" + n + "_";
+            String next = "prog" + (n % SLOTS + 1) + "_start_hhmm";
+            return new Slot(time(whole(s, prefix + "start_hhmm")), time(whole(s, next)),
+                    whole(s, prefix + "power_w"), whole(s, prefix + "soc_pct"), on(s, prefix + "grid_charge"));
+        }).toList();
+    }
+
+    private static String time(int hhmm) {
+        return "%02d:%02d".formatted(hhmm / 100, hhmm % 100);
+    }
+
+    private static Limits limits(Map<String, Double> s) {
+        return new Limits(whole(s, "max_charge_current_a"), whole(s, "max_discharge_current_a"),
+                whole(s, "shutdown_soc_pct"), whole(s, "low_soc_pct"), whole(s, "restart_soc_pct"),
+                on(s, "grid_charge_enabled"), whole(s, "grid_charge_current_a"),
+                whole(s, "grid_charge_start_soc_pct"));
+    }
+}

backend/src/main/java/home/backend/application/Cached.java

@@ -0,0 +1,47 @@
+package home.backend.application;
+
+import java.io.IOException;
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+
+/** One remote answer kept for a while; when a refresh fails the older answer is served and marked stale. */
+final class Cached<T> {
+
+    interface Fetch<T> {
+        T fetch() throws IOException;
+    }
+
+    record Entry<T>(T value, boolean stale) {
+    }
+
+    private final Duration ttl;
+    private final Clock clock;
+    private final Fetch<T> source;
+    private T value;
+    private Instant fetchedAt;
+
+    Cached(Duration ttl, Clock clock, Fetch<T> source) {
+        this.ttl = ttl;
+        this.clock = clock;
+        this.source = source;
+    }
+
+    /** @throws IOException when the refresh fails and there is nothing older to serve */
+    synchronized Entry<T> get() throws IOException {
+        Instant now = clock.instant();
+        if (value != null && now.isBefore(fetchedAt.plus(ttl))) {
+            return new Entry<>(value, false);
+        }
+        try {
+            value = source.fetch();
+            fetchedAt = now;
+            return new Entry<>(value, false);
+        } catch (IOException e) {
+            if (value == null) {
+                throw e;
+            }
+            return new Entry<>(value, true);
+        }
+    }
+}

backend/src/main/java/home/backend/application/DayTally.java

@@ -0,0 +1,96 @@
+package home.backend.application;
+
+import home.backend.domain.HeatPumpSample;
+import home.backend.domain.StatsView.Day;
+import home.backend.domain.StatsView.Totals;
+
+import java.time.Duration;
+import java.time.LocalDate;
+
+/** What the heat pump did over some span of polls; days are added up into the totals. */
+final class DayTally {
+
+    private double compressorSeconds;
+    private double cwuSeconds;
+    private double coSeconds;
+    private double heaterSeconds;
+    private int starts;
+    private int samples;
+    private double outdoorSum;
+    private int outdoorCount;
+    private Double minCwu;
+    private Double maxCwu;
+
+    void sample(HeatPumpSample s) {
+        samples++;
+        if (s.outdoorTemp() != null) {
+            outdoorSum += s.outdoorTemp();
+            outdoorCount++;
+        }
+        if (s.cwuTemp() != null) {
+            minCwu = lower(minCwu, s.cwuTemp());
+            maxCwu = higher(maxCwu, s.cwuTemp());
+        }
+    }
+
+    /** The outputs of {@code s} held for {@code held}. */
+    void hold(HeatPumpSample s, Duration held) {
+        double seconds = held.toMillis() / 1000.0;
+        compressorSeconds += on(s.compressor()) ? seconds : 0;
+        cwuSeconds += on(s.cwu()) ? seconds : 0;
+        coSeconds += on(s.co()) ? seconds : 0;
+        heaterSeconds += on(s.heater()) ? seconds : 0;
+    }
+
+    void start() {
+        starts++;
+    }
+
+    void add(DayTally other) {
+        compressorSeconds += other.compressorSeconds;
+        cwuSeconds += other.cwuSeconds;
+        coSeconds += other.coSeconds;
+        heaterSeconds += other.heaterSeconds;
+        starts += other.starts;
+        samples += other.samples;
+        outdoorSum += other.outdoorSum;
+        outdoorCount += other.outdoorCount;
+        if (other.minCwu != null) {
+            minCwu = lower(minCwu, other.minCwu);
+            maxCwu = higher(maxCwu, other.maxCwu);
+        }
+    }
+
+    Day day(LocalDate date) {
+        if (samples == 0) {
+            return new Day(date, null, null, null, null, null, null, null, null);
+        }
+        return new Day(date, hours(compressorSeconds), starts, hours(cwuSeconds), hours(coSeconds),
+                hours(heaterSeconds), avgOutdoor(), minCwu, maxCwu);
+    }
+
+    Totals totals() {
+        return new Totals(hours(compressorSeconds), starts, hours(cwuSeconds), hours(coSeconds),
+                hours(heaterSeconds), avgOutdoor(), minCwu, maxCwu);
+    }
+
+    static boolean on(Double output) {
+        return output != null && output > 0;
+    }
+
+    private static Double lower(Double known, double value) {
+        return known == null ? value : Math.min(known, value);
+    }
+
+    private static Double higher(Double known, double value) {
+        return known == null ? value : Math.max(known, value);
+    }
+
+    private Double avgOutdoor() {
+        return outdoorCount == 0 ? null : Math.round(outdoorSum / outdoorCount * 10) / 10.0;
+    }
+
+    private static double hours(double seconds) {
+        return Math.round(seconds / 3600 * 100) / 100.0;
+    }
+}

backend/src/main/java/home/backend/application/DeyeSettingLabels.java

@@ -0,0 +1,48 @@
+package home.backend.application;
+
+import java.util.Optional;
+
+/** Polish name and unit of the Deye program registers and of the app's reserve, as the gateway audits them. */
+final class DeyeSettingLabels {
+
+    record Label(String what, String unit) {
+    }
+
+    private static final int TOU_ENABLE = 146;
+    private static final int FIRST_START = 148;
+    private static final int FIRST_SOC = 166;
+    private static final int FIRST_GRID_CHARGE = 172;
+    private static final int SLOTS = 6;
+
+    private DeyeSettingLabels() {
+    }
+
+    static Label of(String register) {
+        if ("reserve".equals(register)) {
+            return new Label("Rezerwa baterii", "%");
+        }
+        int address;
+        try {
+            address = Integer.parseInt(register);
+        } catch (NumberFormatException e) {
+            return unknown(register);
+        }
+        if (address == TOU_ENABLE) {
+            return new Label("Harmonogram baterii", "0/1");
+        }
+        return slot(address, FIRST_START, "start", "HHMM")
+                .or(() -> slot(address, FIRST_SOC, "poziom", "%"))
+                .or(() -> slot(address, FIRST_GRID_CHARGE, "ładowanie z sieci", "0/1"))
+                .orElseGet(() -> unknown(register));
+    }
+
+    private static Label unknown(String register) {
+        return new Label("Rejestr " + register, "");
+    }
+
+    private static Optional<Label> slot(int address, int first, String what, String unit) {
+        return address >= first && address < first + SLOTS
+                ? Optional.of(new Label("Przedział " + (address - first + 1) + ": " + what, unit))
+                : Optional.empty();
+    }
+}

backend/src/main/java/home/backend/application/EnergyDetailsService.java

@@ -0,0 +1,157 @@
+package home.backend.application;
+
+import home.backend.application.SnapshotFields.Live;
+import home.backend.domain.EnergyDetails;
+import home.backend.domain.EnergyDetails.Device;
+import home.backend.domain.EnergyDetails.Group;
+import home.backend.domain.EnergyDetails.Item;
+import home.backend.domain.GatewaySnapshot;
+
+import java.io.IOException;
+import java.time.Clock;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.IntStream;
+
+/**
+ * F7 details: the Deye, Fronius and house meter fields worth a look, grouped and labelled. The
+ * catalog below is the only place that knows a field's label, unit and place; showing a new field
+ * is one line here.
+ */
+public class EnergyDetailsService {
+
+    /** A gateway field shown as {@code label}; {@code scale} turns the stored unit into {@code unit}. */
+    private record Field(String key, String label, String unit, int digits, double scale) {
+    }
+
+    private record Spec(String id, String name, String measurement, List<GroupSpec> groups) {
+    }
+
+    /** {@code measurement} is null for the device's own one. */
+    private record GroupSpec(String title, String measurement, List<Field> fields) {
+    }
+
+    // Each helper returns the fields it stands for, so a group can mix single fields and phase triples.
+    private static Field[] field(String key, String label, String unit, int digits) {
+        return new Field[] {new Field(key, label, unit, digits, 1)};
+    }
+
+    private static Field[] kwhFromWh(String key, String label, int digits) {
+        return new Field[] {new Field(key, label, "kWh", digits, 0.001)};
+    }
+
+    /** L1 to L3 of one quantity; {@code key} holds %d for the phase number. */
+    private static Field[] phases(String key, String label, String unit, int digits) {
+        return IntStream.rangeClosed(1, 3)
+                .mapToObj(n -> new Field(key.formatted(n), label + " L" + n, unit, digits, 1)).toArray(Field[]::new);
+    }
+
+    private static GroupSpec group(String title, Field[]... parts) {
+        return groupOf(null, title, parts);
+    }
+
+    /** A group whose fields come from another measurement of the same device. */
+    private static GroupSpec groupOf(String measurement, String title, Field[]... parts) {
+        return new GroupSpec(title, measurement, Arrays.stream(parts).flatMap(Arrays::stream).toList());
+    }
+
+    private static final List<Spec> CATALOG = List.of(
+            new Spec("deye", "Falownik Deye", "deye", List.of(
+                    group("Bateria",
+                            field("battery_soc_pct", "Naładowanie", "%", 0),
+                            field("battery_power_w", "Moc", "W", 0),
+                            field("battery_voltage_v", "Napięcie", "V", 1),
+                            field("battery_current_a", "Prąd", "A", 1),
+                            field("battery_temperature_c", "Temperatura", "°C", 1)),
+                    group("Sieć",
+                            field("grid_power_w", "Moc razem", "W", 0),
+                            phases("grid_power_l%d_w", "Moc", "W", 0),
+                            phases("grid_voltage_l%d_v", "Napięcie", "V", 1),
+                            field("grid_frequency_hz", "Częstotliwość", "Hz", 2)),
+                    group("Odbiór domu",
+                            field("load_power_w", "Moc razem", "W", 0),
+                            phases("load_power_l%d_w", "Moc", "W", 0)),
+                    group("Panele PV",
+                            field("pv1_power_w", "PV1 moc", "W", 0),
+                            field("pv1_voltage_v", "PV1 napięcie", "V", 1),
+                            field("pv1_current_a", "PV1 prąd", "A", 1),
+                            field("pv2_power_w", "PV2 moc", "W", 0),
+                            field("pv2_voltage_v", "PV2 napięcie", "V", 1),
+                            field("pv2_current_a", "PV2 prąd", "A", 1)),
+                    group("Dziś",
+                            field("pv_today_kwh", "Produkcja PV", "kWh", 1),
+                            field("load_today_kwh", "Zużycie domu", "kWh", 1),
+                            field("grid_bought_today_kwh", "Pobrano z sieci", "kWh", 1),
+                            field("grid_sold_today_kwh", "Oddano do sieci", "kWh", 1),
+                            field("battery_charge_today_kwh", "Bateria naładowana", "kWh", 1),
+                            field("battery_discharge_today_kwh", "Bateria rozładowana", "kWh", 1)),
+                    group("Od początku",
+                            field("pv_total_kwh", "Produkcja PV", "kWh", 0),
+                            field("load_total_kwh", "Zużycie domu", "kWh", 0),
+                            field("grid_bought_total_kwh", "Pobrano z sieci", "kWh", 0),
+                            field("grid_sold_total_kwh", "Oddano do sieci", "kWh", 0),
+                            field("battery_charge_total_kwh", "Bateria naładowana", "kWh", 0),
+                            field("battery_discharge_total_kwh", "Bateria rozładowana", "kWh", 0)),
+                    group("Falownik",
+                            field("inverter_power_w", "Moc wyjściowa", "W", 0),
+                            field("inverter_temperature_c", "Temperatura", "°C", 1),
+                            field("heatsink_temperature_c", "Radiator", "°C", 1)))),
+            new Spec("fronius", "Falownik Fronius", "fronius", List.of(
+                    group("Teraz", field("pv_power_w", "Moc PV", "W", 0)),
+                    group("Produkcja",
+                            kwhFromWh("energy_day_wh", "Dziś", 1),
+                            kwhFromWh("energy_year_wh", "Ten rok", 0),
+                            kwhFromWh("energy_total_wh", "Od początku", 0)))),
+            new Spec("house-meter", "Licznik domu", "PRAD2", List.of(
+                    group("Moc czynna",
+                            field("total_power_active", "Razem", "W", 0),
+                            phases("p%d_power_active", "Moc", "W", 0)),
+                    group("Napięcie", phases("p%d_voltage", "Napięcie", "V", 1)),
+                    group("Prąd", phases("p%d_current", "Prąd", "A", 2)),
+                    group("Współczynnik mocy", phases("p%d_power_factor", "cos φ", "", 2)),
+                    group("Sieć", field("frequency", "Częstotliwość", "Hz", 2)),
+                    group("Energia od początku",
+                            field("import_energy_active", "Pobrana", "kWh", 0),
+                            field("export_energy_active", "Oddana", "kWh", 0)),
+                    groupOf("house_meter_phases", "Energia na fazę",
+                            phases("l%d_import_energy_active_kwh", "Pobrana", "kWh", 0),
+                            phases("l%d_export_energy_active_kwh", "Oddana", "kWh", 0)))));
+
+    private final GatewayClient gateway;
+    private final Clock clock;
+
+    public EnergyDetailsService(GatewayClient gateway, Clock clock) {
+        this.gateway = gateway;
+        this.clock = clock;
+    }
+
+    public EnergyDetails current() throws IOException {
+        GatewaySnapshot snapshot = gateway.snapshot();
+        return new EnergyDetails(CATALOG.stream().map(spec -> device(spec, snapshot)).toList());
+    }
+
+    private Device device(Spec spec, GatewaySnapshot snapshot) {
+        Live live = SnapshotFields.live(snapshot, spec.id(), spec.measurement(), clock.instant());
+        List<Group> groups = spec.groups().stream()
+                .map(g -> group(g, g.measurement() == null ? live.fields() : fieldsOf(snapshot, spec.id(), g)))
+                .filter(g -> !g.items().isEmpty()).toList();
+        return new Device(spec.id(), spec.name(), live.source().time(), live.source().stale(), groups);
+    }
+
+    private Map<String, Double> fieldsOf(GatewaySnapshot snapshot, String device, GroupSpec group) {
+        return SnapshotFields.live(snapshot, device, group.measurement(), clock.instant()).fields();
+    }
+
+    private static Group group(GroupSpec spec, Map<String, Double> fields) {
+        List<Item> items = spec.fields().stream().filter(f -> fields.containsKey(f.key()))
+                .map(f -> new Item(f.label(), scaled(fields.get(f.key()), f), f.unit(), f.digits())).toList();
+        return new Group(spec.title(), items);
+    }
+
+    /** Rounded to the shown precision, so a conversion leaves no binary noise such as 4.3999999. */
+    private static double scaled(double value, Field f) {
+        double factor = Math.pow(10, f.digits());
+        return Math.round(value * f.scale() * factor) / factor;
+    }
+}

backend/src/main/java/home/backend/application/EnergyService.java

@@ -0,0 +1,57 @@
+package home.backend.application;
+
+import home.backend.application.SnapshotFields.Live;
+import home.backend.domain.EnergyView;
+import home.backend.domain.EnergyView.Source;
+import home.backend.domain.EnergyView.Today;
+import home.backend.domain.GatewaySnapshot;
+
+import java.io.IOException;
+import java.time.Clock;
+import java.time.Instant;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Stream;
+
+/** F7: house electricity from the Deye inverter and the Fronius PV inverter. */
+public class EnergyService {
+
+    private final GatewayClient gateway;
+    private final Clock clock;
+
+    public EnergyService(GatewayClient gateway, Clock clock) {
+        this.gateway = gateway;
+        this.clock = clock;
+    }
+
+    public EnergyView current() throws IOException {
+        GatewaySnapshot snapshot = gateway.snapshot();
+        Live deye = SnapshotFields.live(snapshot, "deye", "deye", clock.instant());
+        Live fronius = SnapshotFields.live(snapshot, "fronius", "fronius", clock.instant());
+        Map<String, Double> d = deye.fields();
+        Map<String, Double> f = fronius.fields();
+
+        Double froniusKwh = f.containsKey("energy_day_wh") ? f.get("energy_day_wh") / 1000 : null;
+        Today today = new Today(round(sum(d.get("pv_today_kwh"), froniusKwh)),
+                d.get("grid_bought_today_kwh"), d.get("grid_sold_today_kwh"), d.get("load_today_kwh"));
+        List<Source> sources = List.of(deye.source(), fronius.source());
+        return new EnergyView(oldest(sources), sources,
+                sum(d.get("pv1_power_w"), d.get("pv2_power_w"), f.get("pv_power_w")),
+                d.get("grid_power_w"), d.get("battery_power_w"), d.get("battery_soc_pct"),
+                d.get("load_power_w"), today);
+    }
+
+    private static Instant oldest(List<Source> sources) {
+        return sources.stream().map(Source::time).flatMap(Stream::ofNullable).min(Instant::compareTo).orElse(null);
+    }
+
+    /** Sum of the values that exist; null when none does. */
+    private static Double sum(Double... values) {
+        return Stream.of(values).filter(v -> v != null).reduce(Double::sum).orElse(null);
+    }
+
+    /** Wh to kWh leaves binary noise such as 34.300000000000004. */
+    private static Double round(Double kwh) {
+        return kwh == null ? null : Math.round(kwh * 1000) / 1000.0;
+    }
+}

backend/src/main/java/home/backend/application/ForecastSource.java

@@ -0,0 +1,11 @@
+package home.backend.application;
+
+import home.backend.domain.Forecast;
+
+import java.io.IOException;
+
+/** The weather forecast service: the past 14 days and the next 3. */
+public interface ForecastSource {
+
+    Forecast forecast() throws IOException;
+}

backend/src/main/java/home/backend/application/GatewayBattery.java

@@ -0,0 +1,19 @@
+package home.backend.application;
+
+import home.backend.domain.BatteryChange;
+import home.backend.domain.BatteryResult;
+import home.backend.domain.BatteryView.Reserve;
+
+import java.io.IOException;
+
+/** Battery settings through the gateway, which checks every change (ADR-013). */
+public interface GatewayBattery {
+
+    /** @throws IOException when the gateway has no battery commands, or cannot be reached */
+    Reserve reserve() throws IOException;
+
+    /** A verdict, even a negative one; IOException only when no verdict could be obtained. */
+    BatteryResult changeSchedule(BatteryChange change, String requestedBy) throws IOException;
+
+    BatteryResult changeReserve(int pct, String requestedBy) throws IOException;
+}

backend/src/main/java/home/backend/application/GatewayClient.java

@@ -0,0 +1,11 @@
+package home.backend.application;
+
+import home.backend.domain.GatewaySnapshot;
+
+import java.io.IOException;
+
+/** The live state, read from the gateway on the Pi through the tunnel. */
+public interface GatewayClient {
+
+    GatewaySnapshot snapshot() throws IOException;
+}

backend/src/main/java/home/backend/application/GatewayCommands.java

@@ -0,0 +1,23 @@
+package home.backend.application;
+
+import home.backend.domain.Command;
+import home.backend.domain.CommandResult;
+import home.backend.domain.RestoreResult;
+import home.backend.domain.SetpointState;
+
+import java.io.IOException;
+
+/** The only way the backend writes anything: through the gateway, which checks every command. */
+public interface GatewayCommands {
+
+    /** A verdict, even a negative one; IOException only when no verdict could be obtained. */
+    CommandResult apply(Command command) throws IOException;
+
+    /** Ends the pending change of a setpoint now; a verdict like {@link #apply}. */
+    RestoreResult restore(String setpoint, String requestedBy) throws IOException;
+
+    SetpointState setpoints() throws IOException;
+
+    /** Keeps the gateway's live restores alive; returns how many it extended. */
+    int renewLeases() throws IOException;
+}

backend/src/main/java/home/backend/application/HealthService.java

@@ -0,0 +1,38 @@
+package home.backend.application;
+
+import home.backend.domain.GatewaySnapshot;
+import home.backend.domain.GatewaySnapshot.DeviceSnapshot;
+import home.backend.domain.HealthView;
+import home.backend.domain.HealthView.DeviceHealth;
+
+import java.io.IOException;
+import java.time.Clock;
+import java.util.List;
+
+/** F5: whether the gateway answers and which device links are up. */
+public class HealthService {
+
+    private final GatewayClient gateway;
+    private final Clock clock;
+    private final String version;
+
+    public HealthService(GatewayClient gateway, Clock clock, String version) {
+        this.gateway = gateway;
+        this.clock = clock;
+        this.version = version;
+    }
+
+    public HealthView current() {
+        try {
+            GatewaySnapshot snapshot = gateway.snapshot();
+            List<DeviceHealth> devices = snapshot.devices().stream().map(HealthService::health).toList();
+            return new HealthView(clock.instant(), true, devices, version, snapshot.version());
+        } catch (IOException e) {
+            return new HealthView(clock.instant(), false, List.of(), version, null);
+        }
+    }
+
+    private static DeviceHealth health(DeviceSnapshot d) {
+        return new DeviceHealth(d.name(), d.up(), d.lastSuccess(), d.lastError());
+    }
+}

backend/src/main/java/home/backend/application/HeatPumpSamples.java

@@ -0,0 +1,13 @@
+package home.backend.application;
+
+import home.backend.domain.HeatPumpSample;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.List;
+
+/** The heat pump polls stored in InfluxDB, oldest first. */
+public interface HeatPumpSamples {
+
+    List<HeatPumpSample> samples(Instant from, Instant to) throws IOException;
+}

backend/src/main/java/home/backend/application/HeatPumpService.java

@@ -0,0 +1,87 @@
+package home.backend.application;
+
+import home.backend.domain.GatewaySnapshot;
+import home.backend.domain.GatewaySnapshot.Measurement;
+import home.backend.domain.HeatPumpView;
+import home.backend.domain.HeatPumpView.Pumps;
+import home.backend.domain.HeatPumpView.Setpoints;
+import home.backend.domain.HeatPumpView.State;
+import home.backend.domain.HeatPumpView.Targets;
+import home.backend.domain.HeatPumpView.Temperatures;
+
+import java.io.IOException;
+import java.time.Clock;
+import java.time.Instant;
+import java.util.Map;
+import java.util.Optional;
+
+import static home.backend.application.SnapshotFields.on;
+import static home.backend.application.SnapshotFields.whole;
+
+/** F1: the heat pump's live state from the gateway's {@code heat_pump} measurement. */
+public class HeatPumpService {
+
+    private static final String DATABASE = "Dom_Pompa";
+    private static final State[] STATES = State.values();
+
+    private final GatewayClient gateway;
+    private final Clock clock;
+
+    public HeatPumpService(GatewayClient gateway, Clock clock) {
+        this.gateway = gateway;
+        this.clock = clock;
+    }
+
+    public HeatPumpView current() throws IOException {
+        GatewaySnapshot snapshot = gateway.snapshot();
+        Optional<Measurement> reading = SnapshotFields.find(snapshot, "heat-pump", "heat_pump")
+                .filter(m -> DATABASE.equals(m.database()));
+        boolean stale = SnapshotFields.stale(SnapshotFields.device(snapshot, "heat-pump"), reading, clock.instant());
+        return view(reading.map(Measurement::time).orElse(null), stale,
+                reading.map(Measurement::fields).orElse(Map.of()));
+    }
+
+    private static HeatPumpView view(Instant time, boolean stale, Map<String, Double> f) {
+        Integer alarmCode = whole(f, "alarm_code");
+        return new HeatPumpView(time, stale, state(f), whole(f, "output_compressor"), on(f, "output_heater"),
+                on(f, "alarm") || on(f, "alarm_code"), alarmCode, alarmText(alarmCode),
+                new Pumps(on(f, "output_co"), on(f, "output_buffer"), on(f, "output_circulation"),
+                        on(f, "output_ground"), on(f, "output_cwu")),
+                new Temperatures(tenths(f, "outdoor_temp"), tenths(f, "indoor_temp"),
+                        tenths(f, "co_buffer_temp"), tenths(f, "cwu_temp"), tenths(f, "ground_in_temp"),
+                        tenths(f, "ground_out_temp"), tenths(f, "pump_outlet_temp"),
+                        tenths(f, "outdoor_avg_temp")),
+                new Targets(tenths(f, "target_room_temp"), tenths(f, "target_co_temp"),
+                        tenths(f, "target_cwu_temp")),
+                new Setpoints(whole(f, "setpoint_co_economy"), whole(f, "setpoint_co_comfort"),
+                        whole(f, "setpoint_cwu_economy"), whole(f, "setpoint_cwu_comfort")));
+    }
+
+    /** Codes of register 4011 as the vendor app names them; unverified on our device. */
+    private static String alarmText(Integer code) {
+        if (code == null || code == 0) {
+            return null;
+        }
+        return switch (code) {
+            case 2 -> "Usterka czujnika temperatury zewnętrznej";
+            case 3 -> "Usterka czujnika temperatury CO";
+            case 4 -> "Usterka czujnika temperatury wewnętrznej";
+            case 5 -> "Usterka czujnika temperatury CWU";
+            case 14 -> "Usterka czujnika temperatury wyjścia pompy";
+            case 15 -> "Usterka czujnika temperatury dolnego źródła";
+            case 1003 -> "Zadziałał presostat (ciśnienie)";
+            default -> "Kod usterki " + code;
+        };
+    }
+
+    /** The controller resolves 0.1 °C; the gateway's 212 * 0.1 is 21.200000000000003. */
+    private static Double tenths(Map<String, Double> fields, String name) {
+        Double value = fields.get(name);
+        return value == null ? null : Math.round(value * 10) / 10.0;
+    }
+
+    private static State state(Map<String, Double> f) {
+        Integer mode = whole(f, "pump_mode");
+        return mode == null || mode < 0 || mode >= STATES.length ? null : STATES[mode];
+    }
+}

backend/src/main/java/home/backend/application/HistoryRepository.java

@@ -0,0 +1,14 @@
+package home.backend.application;
+
+import home.backend.domain.HistoryView.Point;
+import home.backend.domain.Series;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.List;
+
+/** Past values from InfluxDB, averaged into about {@code maxPoints} steps. */
+public interface HistoryRepository {
+
+    List<Point> history(Series series, Instant from, Instant to, int maxPoints) throws IOException;
+}

backend/src/main/java/home/backend/application/HistoryService.java

@@ -0,0 +1,43 @@
+package home.backend.application;
+
+import home.backend.domain.HistoryView;
+import home.backend.domain.Series;
+
+import java.io.IOException;
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.Map;
+
+/** F2: one series over the last 24 hours or 7 days. */
+public class HistoryService {
+
+    static final int MAX_POINTS = 300;
+    private static final String DEFAULT_RANGE = "24h";
+    private static final Map<String, Duration> RANGES =
+            Map.of("24h", Duration.ofHours(24), "7d", Duration.ofDays(7));
+
+    private final HistoryRepository repository;
+    private final Clock clock;
+
+    public HistoryService(HistoryRepository repository, Clock clock) {
+        this.repository = repository;
+        this.clock = clock;
+    }
+
+    /**
+     * @param range {@code 24h} or {@code 7d}; null means 24h
+     * @throws IllegalArgumentException for an unknown series or range
+     */
+    public HistoryView history(String seriesId, String range) throws IOException {
+        Series series = Series.fromId(seriesId)
+                .orElseThrow(() -> new IllegalArgumentException("unknown series: " + seriesId));
+        Duration length = RANGES.get(range == null ? DEFAULT_RANGE : range);
+        if (length == null) {
+            throw new IllegalArgumentException("unknown range: " + range);
+        }
+        Instant to = clock.instant();
+        return new HistoryView(series.id(), series.unit(),
+                repository.history(series, to.minus(length), to, MAX_POINTS));
+    }
+}

backend/src/main/java/home/backend/application/LeaseRenewer.java

@@ -0,0 +1,53 @@
+package home.backend.application;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.time.Duration;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Tells the gateway now and then that we are still here (ADR-011): while it hears us, our setpoint
+ * changes stay; once we or the tunnel are gone for 15 minutes, it restores them on its own.
+ */
+public class LeaseRenewer implements AutoCloseable {
+
+    /** A third of the gateway's lease, so two renewals in a row may fail. */
+    public static final Duration PERIOD = Duration.ofMinutes(5);
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(LeaseRenewer.class);
+
+    private final GatewayCommands gateway;
+    private final ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor(
+            Thread.ofVirtual().name("lease-renewal").factory());
+
+    public LeaseRenewer(GatewayCommands gateway) {
+        this.gateway = gateway;
+    }
+
+    public void start() {
+        start(PERIOD);
+    }
+
+    void start(Duration period) {
+        scheduler.scheduleWithFixedDelay(this::renew, 0, period.toMillis(), TimeUnit.MILLISECONDS);
+    }
+
+    /** A failure is logged and retried next cycle; an exception would end the schedule for good. */
+    void renew() {
+        try {
+            int renewed = gateway.renewLeases();
+            LOGGER.debug("renewed {} lease(s)", renewed);
+        } catch (IOException | RuntimeException e) {
+            LOGGER.warn("could not renew the gateway leases, retrying in {}: {}", PERIOD, e.toString());
+        }
+    }
+
+    @Override
+    public void close() {
+        scheduler.shutdownNow();
+    }
+}

backend/src/main/java/home/backend/application/PiSensorService.java

@@ -0,0 +1,27 @@
+package home.backend.application;
+
+import home.backend.application.SnapshotFields.Live;
+import home.backend.domain.PiSensorView;
+
+import java.io.IOException;
+import java.time.Clock;
+import java.util.Map;
+
+/** The BME280 on the Pi, read by the gateway every 5 minutes. */
+public class PiSensorService {
+
+    private final GatewayClient gateway;
+    private final Clock clock;
+
+    public PiSensorService(GatewayClient gateway, Clock clock) {
+        this.gateway = gateway;
+        this.clock = clock;
+    }
+
+    public PiSensorView current() throws IOException {
+        Live live = SnapshotFields.live(gateway.snapshot(), "bme280", "MEASUREMENT", clock.instant());
+        Map<String, Double> f = live.fields();
+        return new PiSensorView(live.source().time(), live.source().stale(),
+                f.get("temperature"), f.get("humidity"), f.get("pressure"));
+    }
+}

backend/src/main/java/home/backend/application/PvEnergyRepository.java

@@ -0,0 +1,12 @@
+package home.backend.application;
+
+import java.io.IOException;
+import java.time.LocalDate;
+import java.util.Map;
+
+/** What the panels produced, from InfluxDB. */
+public interface PvEnergyRepository {
+
+    /** Deye plus Fronius kWh per local day from {@code from} up to {@code to}; days missing either are absent. */
+    Map<LocalDate, Double> dailyKwh(LocalDate from, LocalDate to) throws IOException;
+}

backend/src/main/java/home/backend/application/SetpointService.java

@@ -0,0 +1,152 @@
+package home.backend.application;
+
+import home.backend.domain.Command;
+import home.backend.domain.CommandResult;
+import home.backend.domain.Preset;
+import home.backend.domain.Preset.Change;
+import home.backend.domain.PresetResult;
+import home.backend.domain.PresetResult.ChangeResult;
+import home.backend.domain.PresetResult.ChangeStatus;
+import home.backend.domain.RestoreResult;
+import home.backend.domain.Setpoint;
+import home.backend.domain.SetpointState;
+import home.backend.domain.SetpointsView;
+
+import java.io.IOException;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+/** F3: change setpoints directly or through a preset; the gateway enforces the limits (S1). */
+public class SetpointService {
+
+    private final GatewayCommands gateway;
+    private final List<Preset> presets;
+
+    public SetpointService(GatewayCommands gateway, List<Preset> presets) {
+        this.gateway = gateway;
+        this.presets = List.copyOf(presets);
+    }
+
+    public SetpointsView current() throws IOException {
+        SetpointState state = gateway.setpoints();
+        return new SetpointsView(state.setpoints(), state.restores(), presets);
+    }
+
+    /** @param hours how long to keep the value, null until changed back */
+    public CommandResult apply(String setpoint, int value, Double hours, String user) throws IOException {
+        return gateway.apply(new Command(setpoint, value, duration(hours), user));
+    }
+
+    /** Puts the value from before the pending change back now, instead of waiting for its end. */
+    public RestoreResult restore(String setpoint, String user) throws IOException {
+        return gateway.restore(setpoint, user);
+    }
+
+    /**
+     * Empty if there is no such preset. A preset that does not fit the gateway's limits writes nothing.
+     * IOException only when no change was attempted; once writing starts, trouble is reported per change.
+     *
+     * @param until the end the user chose; required by a held preset, not allowed for any other
+     * @param values the user's own value for some of the preset's setpoints (any preset); the rest keep the
+     *               preset's value
+     * @throws IllegalArgumentException when {@code until} does not match what the preset needs, or a value is
+     *                                  for a setpoint the preset does not change or outside the gateway's limits
+     */
+    public Optional<PresetResult> applyPreset(String id, Instant until, Map<String, Integer> values, String user)
+            throws IOException {
+        Optional<Preset> preset = presets.stream().filter(p -> p.id().equals(id)).findFirst();
+        if (preset.isEmpty()) {
+            return Optional.empty();
+        }
+        if (preset.get().isHeld() != (until != null)) {
+            throw new IllegalArgumentException(preset.get().isHeld() ? "preset " + id + " needs an end time"
+                    : "preset " + id + " has no end time to choose");
+        }
+        List<Change> changes = withValues(preset.get().changes(), values);
+        List<Setpoint> limits = gateway.setpoints().setpoints();
+        requireWithinLimits(values, limits);
+        List<ChangeResult> checked = changes.stream().map(c -> check(c, preset.get().isHeld(), limits)).toList();
+        if (checked.stream().anyMatch(r -> r.status() == ChangeStatus.REJECTED)) {
+            return Optional.of(PresetResult.of(checked));
+        }
+        return Optional.of(PresetResult.of(run(changes, until, user)));
+    }
+
+    private static List<Change> withValues(List<Change> changes, Map<String, Integer> values) {
+        Set<String> own = changes.stream().map(Change::setpoint).collect(Collectors.toSet());
+        if (!own.containsAll(values.keySet())) {
+            throw new IllegalArgumentException("values may only be for the setpoints the preset changes: " + own);
+        }
+        return changes.stream().map(c -> new Change(c.setpoint(), values.getOrDefault(c.setpoint(), c.value()),
+                c.hours())).toList();
+    }
+
+    private static void requireWithinLimits(Map<String, Integer> values, List<Setpoint> limits) {
+        for (Setpoint limit : limits) {
+            Integer value = values.get(limit.name());
+            if (value != null && !limit.allows(value)) {
+                throw new IllegalArgumentException(limit.name() + " must be " + limit.min() + "–" + limit.max()
+                        + " in steps of " + limit.step());
+            }
+        }
+    }
+
+    private List<ChangeResult> run(List<Change> changes, Instant until, String user) {
+        List<ChangeResult> results = new ArrayList<>();
+        for (Change change : changes) {
+            boolean stopped = !results.isEmpty() && results.getLast().status() != ChangeStatus.APPLIED;
+            results.add(stopped ? ChangeResult.notAttempted() : attempt(change, until, user));
+        }
+        return results;
+    }
+
+    private ChangeResult attempt(Change change, Instant until, String user) {
+        try {
+            var command = until == null ? new Command(change.setpoint(), change.value(), duration(change.hours()), user)
+                    : new Command(change.setpoint(), change.value(), null, until, user);
+            return ChangeResult.of(gateway.apply(command));
+        } catch (IOException e) {
+            return new ChangeResult(ChangeStatus.UNKNOWN, "no answer from the gateway", null);
+        }
+    }
+
+    /** REJECTED with the reason, or NOT_ATTEMPTED (nothing is sent if any change is rejected). */
+    private static ChangeResult check(Change change, boolean held, List<Setpoint> limits) {
+        String problem = problem(change, held, limits);
+        return problem == null ? ChangeResult.notAttempted() : new ChangeResult(ChangeStatus.REJECTED, problem, null);
+    }
+
+    private static String problem(Change change, boolean held, List<Setpoint> limits) {
+        Optional<Setpoint> known = limits.stream().filter(s -> s.name().equals(change.setpoint())).findFirst();
+        if (known.isEmpty()) {
+            return "preset sets " + change.setpoint() + ", which the gateway does not know";
+        }
+        if (!known.get().allows(change.value())) {
+            return "preset sets " + change.setpoint() + " to " + change.value() + ", outside the gateway's limits "
+                    + known.get().min() + "–" + known.get().max() + " step " + known.get().step();
+        }
+        // The gateway refuses a held raise too; asking first keeps a preset from stopping half way.
+        if (held && known.get().value() != null && change.value() >= known.get().value()) {
+            return "preset sets " + change.setpoint() + " to " + change.value() + ", which is not below the current "
+                    + known.get().value();
+        }
+        return null;
+    }
+
+    private static Duration duration(Double hours) {
+        if (hours == null) {
+            return null;
+        }
+        long minutes = Math.round(hours * 60);
+        if (minutes < 1 || minutes > Command.MAX_HOURS * 60L) {
+            throw new IllegalArgumentException("hours must be from one minute to " + Command.MAX_HOURS + " hours");
+        }
+        return Duration.ofMinutes(minutes);
+    }
+}

backend/src/main/java/home/backend/application/SnapshotFields.java

@@ -0,0 +1,71 @@
+package home.backend.application;
+
+import home.backend.domain.EnergyView.Source;
+import home.backend.domain.GatewaySnapshot;
+import home.backend.domain.GatewaySnapshot.DeviceSnapshot;
+import home.backend.domain.GatewaySnapshot.Measurement;
+
+import java.time.Duration;
+import java.time.Instant;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+/** Looks up one measurement of one device in a snapshot and reads typed fields. */
+final class SnapshotFields {
+
+    private SnapshotFields() {
+    }
+
+    /** Twice the 300 s the UI treats as one polling cycle; older than that a reading is not live. */
+    private static final Duration MAX_AGE = Duration.ofSeconds(600);
+
+    static Optional<DeviceSnapshot> device(GatewaySnapshot snapshot, String name) {
+        return snapshot.devices().stream().filter(d -> d.name().equals(name)).findFirst();
+    }
+
+    /** A reading is stale when the device link is down, it is missing, or it is older than twice a cycle. */
+    static boolean stale(Optional<DeviceSnapshot> device, Optional<Measurement> reading, Instant now) {
+        return stale(device, reading, now, MAX_AGE);
+    }
+
+    static boolean stale(Optional<DeviceSnapshot> device, Optional<Measurement> reading, Instant now,
+            Duration maxAge) {
+        return device.isEmpty() || !device.get().up() || reading.isEmpty()
+                || Duration.between(reading.get().time(), now).compareTo(maxAge) > 0;
+    }
+
+    /** One device's fields; empty when it is stale, so nothing old is shown as current. */
+    record Live(Source source, Map<String, Double> fields) {
+    }
+
+    static Live live(GatewaySnapshot snapshot, String device, String measurement, Instant now) {
+        return live(snapshot, device, measurement, now, MAX_AGE);
+    }
+
+    static Live live(GatewaySnapshot snapshot, String device, String measurement, Instant now, Duration maxAge) {
+        Optional<Measurement> reading = find(snapshot, device, measurement);
+        boolean stale = stale(device(snapshot, device), reading, now, maxAge);
+        Source source = new Source(device, reading.map(Measurement::time).orElse(null), stale);
+        return new Live(source, stale ? Map.of() : reading.get().fields());
+    }
+
+    static Optional<Measurement> find(GatewaySnapshot snapshot, String device, String measurement) {
+        return snapshot.devices().stream()
+                .filter(d -> d.name().equals(device))
+                .map(DeviceSnapshot::measurements)
+                .flatMap(List::stream)
+                .filter(m -> m.measurement().equals(measurement))
+                .findFirst();
+    }
+
+    static Integer whole(Map<String, Double> fields, String name) {
+        Double value = fields.get(name);
+        return value == null ? null : (int) Math.round(value);
+    }
+
+    static boolean on(Map<String, Double> fields, String name) {
+        Double value = fields.get(name);
+        return value != null && value != 0;
+    }
+}

backend/src/main/java/home/backend/application/StatsService.java

@@ -0,0 +1,89 @@
+package home.backend.application;
+
+import home.backend.domain.HeatPumpSample;
+import home.backend.domain.StatsView;
+import home.backend.domain.StatsView.Day;
+
+import java.io.IOException;
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.time.LocalDate;
+import java.time.ZoneId;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+
+/**
+ * F2: the heat pump's work per local day over the last 7 or 30 days. A poll is taken to hold its
+ * outputs until the next poll, but at most {@link #MAX_HOLD}, so a gap in the data adds no hours.
+ */
+public class StatsService {
+
+    static final ZoneId ZONE = ZoneId.of("Europe/Warsaw");
+    static final Duration MAX_HOLD = Duration.ofSeconds(600);
+    private static final Map<String, Integer> RANGE_DAYS = Map.of("7d", 7, "30d", 30);
+
+    private final HeatPumpSamples repository;
+    private final Clock clock;
+
+    public StatsService(HeatPumpSamples repository, Clock clock) {
+        this.repository = repository;
+        this.clock = clock;
+    }
+
+    /**
+     * @param range {@code 7d} or {@code 30d}
+     * @throws IllegalArgumentException for an unknown range
+     */
+    public StatsView stats(String range) throws IOException {
+        Integer length = range == null ? null : RANGE_DAYS.get(range);
+        if (length == null) {
+            throw new IllegalArgumentException("unknown range: " + range);
+        }
+        Instant now = clock.instant();
+        LocalDate first = now.atZone(ZONE).toLocalDate().minusDays(length - 1);
+        Map<LocalDate, DayTally> tallies = new TreeMap<>();
+        for (int i = 0; i < length; i++) {
+            tallies.put(first.plusDays(i), new DayTally());
+        }
+        tally(repository.samples(first.atStartOfDay(ZONE).toInstant(), now), now, tallies);
+
+        DayTally all = new DayTally();
+        List<Day> days = new ArrayList<>();
+        tallies.forEach((date, tally) -> {
+            days.add(tally.day(date));
+            all.add(tally);
+        });
+        return new StatsView(range, days, all.totals());
+    }
+
+    private static void tally(List<HeatPumpSample> samples, Instant now, Map<LocalDate, DayTally> tallies) {
+        HeatPumpSample previous = null;
+        for (int i = 0; i < samples.size(); i++) {
+            HeatPumpSample s = samples.get(i);
+            DayTally day = tallies.get(s.t().atZone(ZONE).toLocalDate());
+            day.sample(s);
+            if (previous != null && previous.compressor() != null && previous.compressor() == 0
+                    && DayTally.on(s.compressor())) {
+                day.start();
+            }
+            previous = s;
+            hold(s, i + 1 < samples.size() ? samples.get(i + 1).t() : now, tallies);
+        }
+    }
+
+    /** Adds the time {@code s} was in force to the days it falls in; a stretch over midnight is split. */
+    private static void hold(HeatPumpSample s, Instant next, Map<LocalDate, DayTally> tallies) {
+        Instant end = Duration.between(s.t(), next).compareTo(MAX_HOLD) > 0 ? s.t().plus(MAX_HOLD) : next;
+        Instant at = s.t();
+        while (at.isBefore(end)) {
+            LocalDate date = at.atZone(ZONE).toLocalDate();
+            Instant midnight = date.plusDays(1).atStartOfDay(ZONE).toInstant();
+            Instant stop = midnight.isBefore(end) ? midnight : end;
+            tallies.get(date).hold(s, Duration.between(at, stop));
+            at = stop;
+        }
+    }
+}

backend/src/main/java/home/backend/application/WarningSource.java

@@ -0,0 +1,12 @@
+package home.backend.application;
+
+import home.backend.domain.WeatherView.Warning;
+
+import java.io.IOException;
+import java.util.List;
+
+/** Weather warnings that cover the house, whether in force now or announced. */
+public interface WarningSource {
+
+    List<Warning> warnings() throws IOException;
+}

backend/src/main/java/home/backend/application/WeatherService.java

@@ -0,0 +1,98 @@
+package home.backend.application;
+
+import home.backend.application.Cached.Entry;
+import home.backend.domain.Forecast;
+import home.backend.domain.Forecast.DailyForecast;
+import home.backend.domain.PvCalibration;
+import home.backend.domain.WeatherCodes;
+import home.backend.domain.WeatherView;
+import home.backend.domain.WeatherView.Day;
+import home.backend.domain.WeatherView.Now;
+import home.backend.domain.WeatherView.Warning;
+
+import java.io.IOException;
+import java.time.Clock;
+import java.time.Duration;
+import java.time.LocalDate;
+import java.time.ZoneId;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/** Forecast, PV estimate and warnings, each kept for a while so the phones do not load the sources. */
+public class WeatherService {
+
+    private static final ZoneId ZONE = ZoneId.of("Europe/Warsaw");
+    private static final int CALIBRATION_DAYS = 14;
+
+    private record Calibrated(Forecast forecast, Double factor) {
+    }
+
+    private final Clock clock;
+    private final PvEnergyRepository pv;
+    private final Cached<Calibrated> forecast;
+    private final Cached<List<Warning>> warnings;
+
+    public WeatherService(ForecastSource forecastSource, WarningSource warningSource, PvEnergyRepository pv,
+            Clock clock) {
+        this.clock = clock;
+        this.pv = pv;
+        this.forecast = new Cached<>(Duration.ofMinutes(30), clock, () -> calibrated(forecastSource.forecast()));
+        this.warnings = new Cached<>(Duration.ofMinutes(10), clock, warningSource::warnings);
+    }
+
+    /** @throws IOException when there is no forecast at all; warnings alone may be missing. */
+    public WeatherView current() throws IOException {
+        Entry<Calibrated> weather = forecast.get();
+        Entry<List<Warning>> warned = warnings();
+        LocalDate today = LocalDate.now(clock.withZone(ZONE));
+        Calibrated w = weather.value();
+        return new WeatherView(clock.instant(),
+                day(w, today), day(w, today.plusDays(1)), day(w, today.plusDays(2)),
+                new Now(w.forecast().temperature()), inForce(warned.value()), w.factor(),
+                weather.stale() || warned.stale());
+    }
+
+    private Entry<List<Warning>> warnings() {
+        try {
+            return warnings.get();
+        } catch (IOException e) {
+            return new Entry<>(List.of(), true);
+        }
+    }
+
+    private List<Warning> inForce(List<Warning> all) {
+        return all.stream().filter(w -> w.to().toInstant().isAfter(clock.instant())).toList();
+    }
+
+    private Calibrated calibrated(Forecast fetched) {
+        LocalDate today = LocalDate.now(clock.withZone(ZONE));
+        Map<LocalDate, Double> radiation = new HashMap<>();
+        fetched.days().forEach((date, day) -> {
+            if (day.radiationMj() != null) {
+                radiation.put(date, day.radiationMj());
+            }
+        });
+        try {
+            var measured = pv.dailyKwh(today.minusDays(CALIBRATION_DAYS), today);
+            return new Calibrated(fetched, PvCalibration.factor(measured, radiation));
+        } catch (IOException e) {
+            return new Calibrated(fetched, null);
+        }
+    }
+
+    private static Day day(Calibrated w, LocalDate date) throws IOException {
+        DailyForecast d = w.forecast().days().get(date);
+        if (d == null) {
+            throw new IOException("forecast has no " + date);
+        }
+        Double kwh = w.factor() == null || d.radiationMj() == null ? null : round(w.factor() * d.radiationMj());
+        Double sunshine = d.sunshineSeconds() == null ? null : round(d.sunshineSeconds() / 3600);
+        return new Day(date, d.weatherCode(), WeatherCodes.describe(d.weatherCode()), d.tMax(), d.tMin(),
+                d.precipitationMm(), sunshine, kwh);
+    }
+
+    private static double round(double value) {
+        return Math.round(value * 10) / 10.0;
+    }
+}

backend/src/main/java/home/backend/domain/AuditEntry.java

@@ -0,0 +1,14 @@
+package home.backend.domain;
+
+import java.time.Instant;
+
+/**
+ * One audited write. {@code unit} is "°C", "%", "HHMM" (a clock time written as 1830) or "0/1" (off/on);
+ * the values are null when the gateway did not record them.
+ */
+public record AuditEntry(Instant time, String source, String what, Integer oldValue, Integer newValue,
+        String unit, String who, String status) {
+
+    public static final String HEAT_PUMP = "heat_pump";
+    public static final String BATTERY = "battery";
+}

backend/src/main/java/home/backend/domain/AuditView.java

@@ -0,0 +1,7 @@
+package home.backend.domain;
+
+import java.util.List;
+
+/** The audited writes of the heat pump and the battery, newest first. */
+public record AuditView(List<AuditEntry> entries) {
+}

backend/src/main/java/home/backend/domain/BatteryChange.java

@@ -0,0 +1,19 @@
+package home.backend.domain;
+
+import java.time.LocalTime;
+import java.util.List;
+
+/**
+ * A change of the Time of Use switch and of single program slots (1 to 6); a null field stays as it is.
+ * The gateway checks every rule (ADR-013).
+ */
+public record BatteryChange(Boolean enabled, List<Slot> slots) {
+
+    public BatteryChange {
+        slots = slots == null ? List.of() : List.copyOf(slots);
+    }
+
+    /** {@code from} is the slot's start, to the minute. */
+    public record Slot(int slot, LocalTime from, Integer socPct, Boolean gridCharge) {
+    }
+}

backend/src/main/java/home/backend/domain/BatteryResult.java

@@ -0,0 +1,13 @@
+package home.backend.domain;
+
+import java.util.Map;
+
+/**
+ * The gateway's verdict on a battery change, passed on unchanged. REJECTED: refused by the rules, nothing
+ * written. STALE: the inverter's settings are unknown or changed meanwhile, nothing written. TOO_SOON: S4.
+ * FAILED: a write or its read-back went wrong; {@code read} has the registers as read back.
+ */
+public record BatteryResult(Status status, String message, Map<Integer, Integer> read) {
+
+    public enum Status { APPLIED, REJECTED, STALE, TOO_SOON, FAILED }
+}

backend/src/main/java/home/backend/domain/BatteryView.java

@@ -0,0 +1,39 @@
+package home.backend.domain;
+
+import java.time.Instant;
+import java.util.List;
+
+/**
+ * The Deye's battery (F7), read-only. Power in W, + discharge / − charge. The live values
+ * ({@code time}, {@code stale}) come from the Deye's readings and are null when stale; the settings
+ * ({@code settingsTime}, {@code settingsStale}: mode, schedule, limits, capacity) come from their own,
+ * slower reading and are null (empty schedule) when stale. The capacity assumes the nominal 51.2 V.
+ * {@code reserve} is the app's backup reserve (ADR-013) and {@code editable} says the gateway accepts
+ * changes; they are null and false when it does not.
+ */
+public record BatteryView(Instant time, boolean stale, Double socPct, Double powerW, Double voltageV,
+        Double currentA, Double temperatureC, Double capacityKwh, Energy today, Energy total, Mode mode,
+        List<Slot> schedule, Limits limits, Instant settingsTime, boolean settingsStale, Reserve reserve,
+        boolean editable) {
+
+    /** The share of the battery kept for a power cut, and the lowest the user may set. */
+    public record Reserve(int pct, int floorPct) {
+    }
+
+    /** Battery energy in kWh. */
+    public record Energy(Double chargeKwh, Double dischargeKwh) {
+    }
+
+    /** Time of use on means the battery follows the schedule; off means backup only. */
+    public record Mode(boolean touEnabled, String description) {
+    }
+
+    /** A program slot, {@code from} and {@code to} as HH:MM; it runs until the next slot starts. */
+    public record Slot(String from, String to, int powerW, int socPct, boolean gridCharge) {
+    }
+
+    public record Limits(Integer maxChargeA, Integer maxDischargeA, Integer shutdownSocPct,
+            Integer lowSocPct, Integer restartSocPct, boolean gridChargeEnabled, Integer gridChargeCurrentA,
+            Integer gridChargeStartSocPct) {
+    }
+}

backend/src/main/java/home/backend/domain/Command.java

@@ -0,0 +1,19 @@
+package home.backend.domain;
+
+import java.time.Duration;
+import java.time.Instant;
+
+/**
+ * Set a setpoint. With a duration the gateway restores the old value afterwards; with
+ * {@code heldUntil} it holds a lowering value until then without renewals (ADR-012); else it stays
+ * while the backend renews the lease (ADR-011).
+ */
+public record Command(String setpoint, int value, Duration duration, Instant heldUntil, String requestedBy) {
+
+    public Command(String setpoint, int value, Duration duration, String requestedBy) {
+        this(setpoint, value, duration, null, requestedBy);
+    }
+
+    /** The gateway refuses longer boosts too; we refuse first, so the phone gets a clear 400. */
+    public static final int MAX_HOURS = 72;
+}

backend/src/main/java/home/backend/domain/CommandResult.java

@@ -0,0 +1,10 @@
+package home.backend.domain;
+
+import java.time.Instant;
+
+/** The gateway's verdict on a command, passed on to the phone unchanged. */
+public record CommandResult(Status status, String message, Instant restoreAt) {
+
+    /** REJECTED: refused before any write. FAILED: the write or its read-back failed. */
+    public enum Status { APPLIED, REJECTED, FAILED }
+}

backend/src/main/java/home/backend/domain/EnergyDetails.java

@@ -0,0 +1,22 @@
+package home.backend.domain;
+
+import java.time.Instant;
+import java.util.List;
+
+/**
+ * Every value the energy devices report, grouped for a details panel (F7). A device without a
+ * fresh reading has {@code stale} true and no groups; a field the device did not report is absent.
+ */
+public record EnergyDetails(List<Device> devices) {
+
+    /** One device; {@code id} is the gateway's device name. */
+    public record Device(String id, String name, Instant time, boolean stale, List<Group> groups) {
+    }
+
+    public record Group(String title, List<Item> items) {
+    }
+
+    /** A value in {@code unit}, to be shown with {@code digits} decimals. */
+    public record Item(String label, double value, String unit, int digits) {
+    }
+}

backend/src/main/java/home/backend/domain/EnergyView.java

@@ -0,0 +1,21 @@
+package home.backend.domain;
+
+import java.time.Instant;
+import java.util.List;
+
+/**
+ * The house's electricity now (F7). Powers in W; grid + import / − export, battery + discharge /
+ * − charge. Values that come only from a stale source are null. {@code time} is the oldest source
+ * time (null when none was read); {@code sources} lists Deye and Fronius with their own time and freshness.
+ */
+public record EnergyView(Instant time, List<Source> sources, Double pvPowerW, Double gridPowerW,
+        Double batteryPowerW, Double batterySocPct, Double loadPowerW, Today today) {
+
+    /** One inverter; time is null and stale true when the gateway has no reading of it. */
+    public record Source(String name, Instant time, boolean stale) {
+    }
+
+    /** Day totals in kWh since local midnight; PV adds Deye and Fronius. */
+    public record Today(Double pvKwh, Double gridBoughtKwh, Double gridSoldKwh, Double loadKwh) {
+    }
+}

backend/src/main/java/home/backend/domain/Forecast.java

@@ -0,0 +1,13 @@
+package home.backend.domain;
+
+import java.time.LocalDate;
+import java.util.Map;
+
+/** What the forecast service says: the temperature now and a record per calendar day, past days included. */
+public record Forecast(Double temperature, Map<LocalDate, DailyForecast> days) {
+
+    /** Radiation in MJ/m² per day, sunshine in seconds; any value may be missing. */
+    public record DailyForecast(Integer weatherCode, Double tMax, Double tMin, Double precipitationMm,
+            Double radiationMj, Double sunshineSeconds) {
+    }
+}

backend/src/main/java/home/backend/domain/GatewaySnapshot.java

@@ -0,0 +1,18 @@
+package home.backend.domain;
+
+import java.time.Instant;
+import java.util.List;
+import java.util.Map;
+
+/** The gateway's latest state of every device, as the backend sees it.
+ * The version is the gateway's release tag, null for a gateway that does not report it yet. */
+public record GatewaySnapshot(String version, List<DeviceSnapshot> devices) {
+
+    public record DeviceSnapshot(String name, boolean up, Instant lastSuccess, String lastError,
+            List<Measurement> measurements) {
+    }
+
+    /** One reading the gateway wrote to InfluxDB, e.g. heat_pump or deye. */
+    public record Measurement(String database, String measurement, Map<String, Double> fields, Instant time) {
+    }
+}

backend/src/main/java/home/backend/domain/HealthView.java

@@ -0,0 +1,13 @@
+package home.backend.domain;
+
+import java.time.Instant;
+import java.util.List;
+
+/** Health of the chain phone → backend → gateway → devices (F5), with the deployed versions.
+ * The gateway's version is null when it is unreachable or too old to report it. */
+public record HealthView(Instant time, boolean gatewayReachable, List<DeviceHealth> devices,
+        String backendVersion, String gatewayVersion) {
+
+    public record DeviceHealth(String name, boolean up, Instant lastSuccess, String lastError) {
+    }
+}

backend/src/main/java/home/backend/domain/HeatPumpSample.java

@@ -0,0 +1,8 @@
+package home.backend.domain;
+
+import java.time.Instant;
+
+/** One poll of the heat pump from InfluxDB; a field the poll did not carry is null. */
+public record HeatPumpSample(Instant t, Double compressor, Double cwu, Double co, Double heater,
+        Double outdoorTemp, Double cwuTemp) {
+}

backend/src/main/java/home/backend/domain/HeatPumpView.java

@@ -0,0 +1,30 @@
+package home.backend.domain;
+
+import java.time.Instant;
+
+/**
+ * What the heat pump does now (F1). Without a reading from the gateway {@code time} and the values are
+ * null; {@code stale} is true when the device is down or the reading is older than 2 × 300 s.
+ */
+public record HeatPumpView(Instant time, boolean stale, State state, Integer compressorPercent, boolean heaterOn,
+        boolean alarm, Integer alarmCode, String alarmText, Pumps pumps, Temperatures temperatures,
+        Targets targets, Setpoints setpoints) {
+
+    /** From register 4227: 0 stop, 1 CO, 2 CWU, 3 both. */
+    public enum State { IDLE, HEATING_CO, HEATING_CWU, HEATING_BOTH }
+
+    public record Pumps(boolean co, boolean buffer, boolean circulation, boolean ground, boolean cwu) {
+    }
+
+    public record Temperatures(Double outdoor, Double indoor, Double coBuffer, Double cwu,
+            Double groundIn, Double groundOut, Double pumpOutlet, Double outdoorAvg) {
+    }
+
+    /** Targets the controller works to right now (economy or comfort period). */
+    public record Targets(Double room, Double co, Double cwu) {
+    }
+
+    /** The four setpoints F3 will change; whole °C. */
+    public record Setpoints(Integer coEconomy, Integer coComfort, Integer cwuEconomy, Integer cwuComfort) {
+    }
+}

backend/src/main/java/home/backend/domain/HistoryView.java

@@ -0,0 +1,11 @@
+package home.backend.domain;
+
+import java.time.Instant;
+import java.util.List;
+
+/** One series over a time range, already averaged into chart-sized steps. */
+public record HistoryView(String series, String unit, List<Point> points) {
+
+    public record Point(Instant t, double v) {
+    }
+}

backend/src/main/java/home/backend/domain/PiSensorView.java

@@ -0,0 +1,11 @@
+package home.backend.domain;
+
+import java.time.Instant;
+
+/**
+ * The BME280 sensor on the Raspberry Pi: °C, % and hPa. When it is stale (device down, no reading
+ * or older than 2 × 300 s) the values are null and {@code stale} is true; {@code time} is null
+ * without any reading.
+ */
+public record PiSensorView(Instant time, boolean stale, Double temperature, Double humidity, Double pressure) {
+}

backend/src/main/java/home/backend/domain/Preset.java

@@ -0,0 +1,50 @@
+package home.backend.domain;
+
+import com.fasterxml.jackson.annotation.JsonIgnore;
+import com.fasterxml.jackson.annotation.JsonInclude;
+
+import java.util.List;
+
+/**
+ * A named one-tap bundle of setpoint changes (F3), e.g. boost or away. {@code until} is null, or
+ * {@link #CHOSEN}: the user picks the end on a calendar and the gateway holds the changes until
+ * then without renewals (ADR-012).
+ */
+public record Preset(String id, String name, @JsonInclude(JsonInclude.Include.NON_NULL) String until,
+        List<Change> changes) {
+
+    public static final String CHOSEN = "chosen";
+
+    /** {@code hours} null means "until changed back". */
+    public record Change(String setpoint, int value, Double hours) {
+
+        public Change {
+            if (setpoint == null || setpoint.isBlank()) {
+                throw new IllegalArgumentException("a preset change needs a setpoint");
+            }
+            if (hours != null && (hours <= 0 || hours > Command.MAX_HOURS)) {
+                throw new IllegalArgumentException("preset hours must be above 0 and at most " + Command.MAX_HOURS);
+            }
+        }
+    }
+
+    @JsonIgnore
+    public boolean isHeld() {
+        return CHOSEN.equals(until);
+    }
+
+    public Preset {
+        if (id == null || id.isBlank() || name == null || name.isBlank()) {
+            throw new IllegalArgumentException("a preset needs an id and a name");
+        }
+        if (changes == null || changes.isEmpty()) {
+            throw new IllegalArgumentException("preset " + id + " has no changes");
+        }
+        if (until != null && !until.equals(CHOSEN)) {
+            throw new IllegalArgumentException("preset " + id + ": until can only be \"" + CHOSEN + "\"");
+        }
+        if (CHOSEN.equals(until) && changes.stream().anyMatch(change -> change.hours() != null)) {
+            throw new IllegalArgumentException("preset " + id + " is held until a chosen time, so no hours");
+        }
+    }
+}

backend/src/main/java/home/backend/domain/PresetResult.java

@@ -0,0 +1,44 @@
+package home.backend.domain;
+
+import java.time.Instant;
+import java.util.List;
+
+/**
+ * What happened to each change of a preset, one entry per change in preset order. Changes run in
+ * order and stop at the first that is not applied; the rest are NOT_ATTEMPTED.
+ *
+ * <p>{@code status}: APPLIED when every change was; PARTIAL when some were and some were not;
+ * otherwise FAILED if any change failed or went unanswered (the pump may have changed), else
+ * REJECTED (nothing was written).
+ */
+public record PresetResult(Status status, List<ChangeResult> results) {
+
+    public enum Status { APPLIED, REJECTED, FAILED, PARTIAL }
+
+    /** UNKNOWN: the gateway did not answer, so the change may or may not have reached the pump. */
+    public enum ChangeStatus { APPLIED, REJECTED, FAILED, NOT_ATTEMPTED, UNKNOWN }
+
+    public record ChangeResult(ChangeStatus status, String message, Instant restoreAt) {
+
+        public static ChangeResult of(CommandResult verdict) {
+            return new ChangeResult(ChangeStatus.valueOf(verdict.status().name()), verdict.message(),
+                    verdict.restoreAt());
+        }
+
+        public static ChangeResult notAttempted() {
+            return new ChangeResult(ChangeStatus.NOT_ATTEMPTED, null, null);
+        }
+    }
+
+    public static PresetResult of(List<ChangeResult> results) {
+        boolean applied = results.stream().anyMatch(r -> r.status() == ChangeStatus.APPLIED);
+        boolean all = results.stream().allMatch(r -> r.status() == ChangeStatus.APPLIED);
+        boolean maybeWritten = results.stream()
+                .anyMatch(r -> r.status() == ChangeStatus.FAILED || r.status() == ChangeStatus.UNKNOWN);
+        Status status = all ? Status.APPLIED
+                : applied ? Status.PARTIAL
+                : maybeWritten ? Status.FAILED
+                : Status.REJECTED;
+        return new PresetResult(status, results);
+    }
+}

backend/src/main/java/home/backend/domain/PvCalibration.java

@@ -0,0 +1,32 @@
+package home.backend.domain;
+
+import java.time.LocalDate;
+import java.util.Map;
+
+/**
+ * The PV output per unit of radiation, found from past days instead of the panels' tilt and azimuth:
+ * measured kWh over forecast MJ/m², summed over the days that have both.
+ */
+public final class PvCalibration {
+
+    static final int MIN_DAYS = 5;
+
+    private PvCalibration() {
+    }
+
+    /** Null with fewer than {@value MIN_DAYS} days having both values or no radiation at all. */
+    public static Double factor(Map<LocalDate, Double> measuredKwh, Map<LocalDate, Double> radiationMj) {
+        double kwh = 0;
+        double mj = 0;
+        int days = 0;
+        for (var day : measuredKwh.entrySet()) {
+            Double radiation = radiationMj.get(day.getKey());
+            if (radiation != null) {
+                kwh += day.getValue();
+                mj += radiation;
+                days++;
+            }
+        }
+        return days < MIN_DAYS || mj <= 0 ? null : kwh / mj;
+    }
+}

backend/src/main/java/home/backend/domain/Restore.java

@@ -0,0 +1,10 @@
+package home.backend.domain;
+
+import java.time.Instant;
+
+/**
+ * A change the gateway will undo at {@code due} (null: until changed), unless someone changed the
+ * register meanwhile. It also undoes it when we stop renewing the lease (ADR-011).
+ */
+public record Restore(String setpoint, int register, int originalValue, int appliedValue, Instant due) {
+}

backend/src/main/java/home/backend/domain/RestoreResult.java

@@ -0,0 +1,11 @@
+package home.backend.domain;
+
+/** The gateway's answer to "restore now", passed on to the phone unchanged. */
+public record RestoreResult(Outcome outcome, String message) {
+
+    /**
+     * NOT_PENDING: nothing to restore. CONFLICT: the register was changed meanwhile, so it was left alone.
+     * TOO_SOON: the gateway's rate limit. FAILED: the restore stays pending and is retried.
+     */
+    public enum Outcome { RESTORED, NOT_PENDING, CONFLICT, TOO_SOON, FAILED }
+}

backend/src/main/java/home/backend/domain/Series.java

@@ -0,0 +1,39 @@
+package home.backend.domain;
+
+import java.util.Arrays;
+import java.util.Optional;
+
+/** The history series the UI may ask for (F2); an allowlist, so no query is built from input. */
+public enum Series {
+    OUTDOOR_TEMP("outdoor_temp", "°C"),
+    INDOOR_TEMP("indoor_temp", "°C"),
+    CO_BUFFER_TEMP("co_buffer_temp", "°C"),
+    CWU_TEMP("cwu_temp", "°C"),
+    GROUND_IN_TEMP("ground_in_temp", "°C"),
+    GROUND_OUT_TEMP("ground_out_temp", "°C"),
+    PUMP_OUTLET_TEMP("pump_outlet_temp", "°C"),
+    GRID_POWER("grid_power", "W"),
+    PV_POWER("pv_power", "W"),
+    LOAD_POWER("load_power", "W"),
+    BATTERY_SOC("battery_soc", "%");
+
+    private final String id;
+    private final String unit;
+
+    Series(String id, String unit) {
+        this.id = id;
+        this.unit = unit;
+    }
+
+    public String id() {
+        return id;
+    }
+
+    public String unit() {
+        return unit;
+    }
+
+    public static Optional<Series> fromId(String id) {
+        return Arrays.stream(values()).filter(series -> series.id.equals(id)).findFirst();
+    }
+}

backend/src/main/java/home/backend/domain/Setpoint.java

@@ -0,0 +1,9 @@
+package home.backend.domain;
+
+/** One of the four writable setpoints as the gateway reports it; {@code value} is null until it has been read. */
+public record Setpoint(String name, int register, int min, int max, int step, Integer value) {
+
+    public boolean allows(int candidate) {
+        return candidate >= min && candidate <= max && (candidate - min) % step == 0;
+    }
+}

backend/src/main/java/home/backend/domain/SetpointState.java

@@ -0,0 +1,7 @@
+package home.backend.domain;
+
+import java.util.List;
+
+/** What the gateway knows about the setpoints: their limits, values and the pending restores. */
+public record SetpointState(List<Setpoint> setpoints, List<Restore> restores) {
+}

backend/src/main/java/home/backend/domain/SetpointsView.java

@@ -0,0 +1,7 @@
+package home.backend.domain;
+
+import java.util.List;
+
+/** The setpoints screen: gateway state plus the presets from the backend config. */
+public record SetpointsView(List<Setpoint> setpoints, List<Restore> restores, List<Preset> presets) {
+}

backend/src/main/java/home/backend/domain/StatsView.java

@@ -0,0 +1,19 @@
+package home.backend.domain;
+
+import java.time.LocalDate;
+import java.util.List;
+
+/**
+ * Heat pump work per local day (F2). Hours are approximated from the polls, starts are counted
+ * between polls, so short cycles are missed. A day without polls has null values.
+ */
+public record StatsView(String range, List<Day> days, Totals totals) {
+
+    public record Day(LocalDate date, Double compressorHours, Integer compressorStarts, Double cwuHours,
+            Double coHours, Double heaterHours, Double avgOutdoorTemp, Double minCwuTemp, Double maxCwuTemp) {
+    }
+
+    public record Totals(double compressorHours, int compressorStarts, double cwuHours, double coHours,
+            double heaterHours, Double avgOutdoorTemp, Double minCwuTemp, Double maxCwuTemp) {
+    }
+}

backend/src/main/java/home/backend/domain/WeatherCodes.java

@@ -0,0 +1,37 @@
+package home.backend.domain;
+
+/** WMO weather interpretation codes as Polish text. */
+public final class WeatherCodes {
+
+    private WeatherCodes() {
+    }
+
+    public static String describe(Integer code) {
+        if (code == null) {
+            return "Brak danych";
+        }
+        return switch (code) {
+            case 0 -> "Bezchmurnie";
+            case 1 -> "Przeważnie słonecznie";
+            case 2 -> "Częściowe zachmurzenie";
+            case 3 -> "Pochmurno";
+            case 45, 48 -> "Mgła";
+            case 51, 53, 55 -> "Mżawka";
+            case 56, 57 -> "Marznąca mżawka";
+            case 61 -> "Słaby deszcz";
+            case 63 -> "Deszcz";
+            case 65 -> "Silny deszcz";
+            case 66, 67 -> "Marznący deszcz";
+            case 71 -> "Słaby śnieg";
+            case 73 -> "Śnieg";
+            case 75 -> "Intensywny śnieg";
+            case 77 -> "Ziarna śnieżne";
+            case 80, 81 -> "Przelotny deszcz";
+            case 82 -> "Ulewa";
+            case 85, 86 -> "Przelotny śnieg";
+            case 95 -> "Burza";
+            case 96, 99 -> "Burza z gradem";
+            default -> "Brak danych";
+        };
+    }
+}

backend/src/main/java/home/backend/domain/WeatherView.java

@@ -0,0 +1,27 @@
+package home.backend.domain;
+
+import java.time.Instant;
+import java.time.LocalDate;
+import java.time.OffsetDateTime;
+import java.util.List;
+
+/**
+ * Weather at the house: three days, the temperature now and the IMGW warnings in force or announced.
+ * {@code pvFactor} (kWh per MJ/m² of forecast radiation) and every {@code pvForecastKwh} are null while
+ * there are too few measured days to calibrate. {@code stale} means part of it is an older answer
+ * because a source could not be reached.
+ */
+public record WeatherView(Instant time, Day today, Day tomorrow, Day dayAfter, Now now,
+        List<Warning> warnings, Double pvFactor, boolean stale) {
+
+    public record Day(LocalDate date, Integer weatherCode, String description, Double tMax, Double tMin,
+            Double precipitationMm, Double sunshineHours, Double pvForecastKwh) {
+    }
+
+    public record Now(Double temperature) {
+    }
+
+    /** {@code level} is IMGW's degree 1 to 3. */
+    public record Warning(String event, int level, OffsetDateTime from, OffsetDateTime to, String text) {
+    }
+}

backend/src/main/resources/presets-default.json

@@ -0,0 +1,16 @@
+[
+  {
+    "id": "cwu-now",
+    "name": "Ciepła woda teraz",
+    "changes": [ { "setpoint": "cwu_economy", "value": 45, "hours": 2 } ]
+  },
+  {
+    "id": "away",
+    "name": "Wyjazd",
+    "until": "chosen",
+    "changes": [
+      { "setpoint": "cwu_comfort", "value": 10, "hours": null },
+      { "setpoint": "co_comfort", "value": 15, "hours": null }
+    ]
+  }
+]

backend/src/test/java/home/backend/BackendTest.java

@@ -0,0 +1,312 @@
+package home.backend;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.sun.net.httpserver.HttpExchange;
+import com.sun.net.httpserver.HttpServer;
+import home.backend.adapters.http.ApiServer;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.time.ZoneOffset;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeSet;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/** The assembled backend against a stub gateway and a stub InfluxDB, both on localhost. */
+class BackendTest {
+
+    private static final ObjectMapper JSON = new ObjectMapper();
+
+    /** Just after the readings in the snapshot fixture, so they count as fresh. */
+    private static final Clock CLOCK = Clock.fixed(Instant.parse("2026-10-23T22:27:00Z"), ZoneOffset.UTC);
+
+    private final HttpClient client = HttpClient.newHttpClient();
+    private HttpServer gateway;
+    private HttpServer influx;
+    private ApiServer backend;
+
+    @BeforeEach
+    void start() throws IOException {
+        gateway = stub(Map.of(
+                "/health", "src/test/resources/gateway/health-all-up.json",
+                "/snapshot", "src/test/resources/gateway/snapshot-all-up.json"));
+        gateway.createContext("/commands", this::commands);
+        influx = stub(Map.of("/query", "src/test/resources/influx/influx-query-cwu-6h.json"));
+        var settings = new Settings(url(gateway), url(influx), 0, Duration.ofSeconds(2), Duration.ofSeconds(2),
+                "s3cret-token", null);
+        backend = Backend.assemble(settings, CLOCK);
+        backend.start();
+    }
+
+    private record Command(String authorization, String requestedBy, String body) {
+    }
+
+    private final List<Command> commandsSeen = new ArrayList<>();
+
+    /** The gateway's /commands, answering with the gateway's own contract examples. */
+    private void commands(HttpExchange exchange) throws IOException {
+        boolean post = exchange.getRequestMethod().equals("POST");
+        if (post) {
+            commandsSeen.add(new Command(exchange.getRequestHeaders().getFirst("Authorization"),
+                    exchange.getRequestHeaders().getFirst("X-Requested-By"),
+                    new String(exchange.getRequestBody().readAllBytes(), StandardCharsets.UTF_8)));
+        }
+        byte[] body = Files.readAllBytes(Path.of("../gateway/src/test/resources/commands/"
+                + (post ? "response-applied.json" : "setpoints.json")));
+        exchange.sendResponseHeaders(200, body.length);
+        exchange.getResponseBody().write(body);
+        exchange.close();
+    }
+
+    private HttpResponse<String> post(String path, String body) throws Exception {
+        var request = HttpRequest.newBuilder(URI.create("http://127.0.0.1:" + backend.port() + path))
+                .header("Remote-User", "anna").header("Content-Type", "application/json")
+                .header("X-Requested-With", "home-pump")
+                .POST(HttpRequest.BodyPublishers.ofString(body)).build();
+        return client.send(request, HttpResponse.BodyHandlers.ofString(StandardCharsets.UTF_8));
+    }
+
+    @AfterEach
+    void stop() {
+        backend.stop();
+        gateway.stop(0);
+        influx.stop(0);
+    }
+
+    private static HttpServer stub(Map<String, String> bodies) throws IOException {
+        HttpServer server = HttpServer.create(new InetSocketAddress(InetAddress.getLoopbackAddress(), 0), 0);
+        bodies.forEach((path, file) -> server.createContext(path, exchange -> {
+            byte[] body = Files.readAllBytes(Path.of(file));
+            exchange.getResponseHeaders().set("Content-Type", "application/json");
+            exchange.sendResponseHeaders(200, body.length);
+            exchange.getResponseBody().write(body);
+            exchange.close();
+        }));
+        server.start();
+        return server;
+    }
+
+    private static URI url(HttpServer server) {
+        return URI.create("http://127.0.0.1:" + server.getAddress().getPort());
+    }
+
+    private HttpResponse<String> get(String path) throws Exception {
+        var request = HttpRequest.newBuilder(URI.create("http://127.0.0.1:" + backend.port() + path)).build();
+        return client.send(request, HttpResponse.BodyHandlers.ofString(StandardCharsets.UTF_8));
+    }
+
+    /** The names of every field, nested ones as a.b; array elements are not descended into. */
+    private static TreeSet<String> fieldNames(JsonNode node, String prefix, TreeSet<String> names) {
+        node.fieldNames().forEachRemaining(name -> {
+            names.add(prefix + name);
+            fieldNames(node.get(name), prefix + name + ".", names);
+        });
+        return names;
+    }
+
+    private void assertServesApiShapeOf(String path, String example) throws Exception {
+        HttpResponse<String> response = get(path);
+
+        assertEquals(200, response.statusCode(), path);
+        assertEquals("application/json", response.headers().firstValue("Content-Type").orElseThrow());
+        JsonNode expected = JSON.readTree(Files.readString(Path.of("src/test/resources/api/" + example + ".json")));
+        assertEquals(fieldNames(expected, "", new TreeSet<>()),
+                fieldNames(JSON.readTree(response.body()), "", new TreeSet<>()), path);
+    }
+
+    /** The body equals the documented example, value by value. */
+    private void assertServesExactly(String path, String example) throws Exception {
+        HttpResponse<String> response = get(path);
+
+        assertEquals(200, response.statusCode(), path);
+        assertEquals(JSON.readTree(Files.readString(Path.of("src/test/resources/api/" + example + ".json"))),
+                JSON.readTree(response.body()), path);
+    }
+
+    @Test
+    void servesHeatPumpFromTheGatewayReadings() throws Exception {
+        assertServesExactly("/api/heat-pump", "heat-pump");
+    }
+
+    @Test
+    void servesPiSensorFromTheGatewayReadings() throws Exception {
+        assertServesExactly("/api/pi-sensor", "pi-sensor");
+    }
+
+    @Test
+    void servesEnergyFromTheGatewayReadings() throws Exception {
+        assertServesExactly("/api/energy", "energy");
+    }
+
+    @Test
+    void servesHealthOfEveryGatewayDevice() throws Exception {
+        assertServesApiShapeOf("/api/health", "health");
+        JsonNode health = JSON.readTree(get("/api/health").body());
+
+        assertTrue(health.get("gatewayReachable").asBoolean());
+        List<String> names = new ArrayList<>();
+        health.get("devices").forEach(device -> {
+            names.add(device.get("name").asText());
+            assertTrue(device.get("up").asBoolean(), names.getLast());
+        });
+        assertEquals(List.of("bme280", "deye", "fronius", "heat-pump", "house-meter"), names);
+    }
+
+    @Test
+    void servesHistoryFromInflux() throws Exception {
+        assertServesApiShapeOf("/api/history?series=cwu_temp&range=24h", "history");
+        JsonNode points = JSON.readTree(get("/api/history?series=cwu_temp&range=24h").body()).get("points");
+        assertFalse(points.isEmpty());
+    }
+
+    @Test
+    void servesSetpointsWithTheBuiltInPresets() throws Exception {
+        JsonNode view = JSON.readTree(get("/api/setpoints").body());
+
+        assertEquals(JSON.readTree(Files.readString(Path.of("src/test/resources/api/setpoints.json"))), view);
+    }
+
+    @Test
+    void boostGoesToTheGatewayWithTokenAndUser() throws Exception {
+        var response = post("/api/setpoints",
+                Files.readString(Path.of("src/test/resources/api/setpoints-request.json")));
+
+        assertEquals(200, response.statusCode());
+        assertEquals(JSON.readTree(Files.readString(Path.of("src/test/resources/api/setpoints-applied.json"))),
+                JSON.readTree(response.body()));
+        assertEquals(1, commandsSeen.size());
+        assertEquals("Bearer s3cret-token", commandsSeen.getFirst().authorization());
+        assertEquals("anna", commandsSeen.getFirst().requestedBy());
+        assertEquals(JSON.readTree(Files.readString(Path.of("../gateway/src/test/resources/commands/request-boost.json"))),
+                JSON.readTree(commandsSeen.getFirst().body()));
+    }
+
+    @Test
+    void presetsComeFromPresetsFile(@TempDir Path dir) throws Exception {
+        Path file = Files.writeString(dir.resolve("presets.json"),
+                "[{\"id\":\"bath\",\"name\":\"Kąpiel\",\"changes\":[{\"setpoint\":\"cwu_economy\",\"value\":48,\"hours\":1}]}]");
+        var custom = Backend.assemble(new Settings(url(gateway), url(influx), 0, Duration.ofSeconds(2),
+                Duration.ofSeconds(2), "s3cret-token", file), CLOCK);
+        custom.start();
+        try {
+            var request = HttpRequest.newBuilder(URI.create("http://127.0.0.1:" + custom.port() + "/api/presets/bath"))
+                    .header("Content-Type", "application/json").header("X-Requested-With", "home-pump")
+                    .POST(HttpRequest.BodyPublishers.noBody()).build();
+            var response = client.send(request, HttpResponse.BodyHandlers.ofString());
+
+            assertEquals(200, response.statusCode());
+            assertEquals("phone", commandsSeen.getFirst().requestedBy());
+            assertEquals(JSON.readTree("{\"setpoint\":\"cwu_economy\",\"value\":48,\"minutes\":60}"),
+                    JSON.readTree(commandsSeen.getFirst().body()));
+        } finally {
+            custom.stop();
+        }
+    }
+
+    @Test
+    void withoutTokenSetpointsAreUnavailableButLiveStateStays() throws Exception {
+        var noToken = Backend.assemble(new Settings(url(gateway), url(influx), 0, Duration.ofSeconds(2),
+                Duration.ofSeconds(2), null, null), CLOCK);
+        noToken.start();
+        try {
+            var base = "http://127.0.0.1:" + noToken.port();
+            assertEquals(503, client.send(HttpRequest.newBuilder(URI.create(base + "/api/setpoints")).build(),
+                    HttpResponse.BodyHandlers.ofString()).statusCode());
+            assertEquals(200, client.send(HttpRequest.newBuilder(URI.create(base + "/api/heat-pump")).build(),
+                    HttpResponse.BodyHandlers.ofString()).statusCode());
+            assertTrue(commandsSeen.isEmpty());
+        } finally {
+            noToken.stop();
+        }
+    }
+
+    @Test
+    void settingsNeedBothUrls() {
+        var e = assertThrows(IllegalArgumentException.class,
+                () -> Settings.fromEnvironment(Map.of("INFLUX_URL", "https://influx.example")));
+        assertTrue(e.getMessage().contains("GATEWAY_URL"));
+        e = assertThrows(IllegalArgumentException.class,
+                () -> Settings.fromEnvironment(Map.of("GATEWAY_URL", "http://gw:8080")));
+        assertTrue(e.getMessage().contains("INFLUX_URL"));
+    }
+
+    @Test
+    void urlsMayEndWithASingleSlash() {
+        var settings = Settings.fromEnvironment(
+                Map.of("GATEWAY_URL", "http://gw:8080/", "INFLUX_URL", "https://influx.example/"));
+
+        assertEquals(URI.create("http://gw:8080/"), settings.gatewayUrl());
+    }
+
+    @Test
+    void settingsHaveDefaults() {
+        var settings = Settings.fromEnvironment(
+                Map.of("GATEWAY_URL", "http://gw:8080", "INFLUX_URL", "https://influx.example"));
+
+        assertEquals(8080, settings.port());
+        assertEquals(Duration.ofSeconds(5), settings.gatewayTimeout());
+        assertEquals(Duration.ofSeconds(10), settings.influxTimeout());
+    }
+
+    @Test
+    void tokenAndPresetsFileAreOptional() {
+        var urls = Map.of("GATEWAY_URL", "http://gw:8080", "INFLUX_URL", "https://influx.example");
+        var none = Settings.fromEnvironment(urls);
+        var env = new HashMap<>(urls);
+        env.put("GATEWAY_TOKEN", " s3cret-token ");
+        env.put("PRESETS_FILE", "/etc/home-pump/presets.json");
+        var set = Settings.fromEnvironment(env);
+        env.put("GATEWAY_TOKEN", " ");
+        env.put("PRESETS_FILE", "");
+
+        assertEquals(null, none.gatewayToken());
+        assertEquals(null, none.presetsFile());
+        assertEquals("s3cret-token", set.gatewayToken());
+        assertEquals(Path.of("/etc/home-pump/presets.json"), set.presetsFile());
+        assertEquals(null, Settings.fromEnvironment(env).gatewayToken());
+    }
+
+    @Test
+    void settingsRejectBadValues() {
+        var urls = Map.of("GATEWAY_URL", "http://gw:8080", "INFLUX_URL", "https://influx.example");
+        for (Map<String, String> bad : List.of(
+                Map.of("GATEWAY_URL", "gw:8080", "INFLUX_URL", "https://influx.example"),
+                Map.of("GATEWAY_URL", "ftp://gw", "INFLUX_URL", "https://influx.example"),
+                Map.of("GATEWAY_URL", "http://gw:8080/api", "INFLUX_URL", "https://influx.example"),
+                Map.of("GATEWAY_URL", "http://gw:8080", "INFLUX_URL", "https://influx.example/influx/"),
+                Map.of("GATEWAY_URL", "http://gw:8080?x=1", "INFLUX_URL", "https://influx.example"))) {
+            assertThrows(IllegalArgumentException.class, () -> Settings.fromEnvironment(bad));
+        }
+        for (String name : List.of("PORT", "GATEWAY_TIMEOUT", "INFLUX_TIMEOUT")) {
+            for (String value : List.of("abc", "-1", "0x10", "99999999")) {
+                var env = new HashMap<>(urls);
+                env.put(name, value);
+                var e = assertThrows(IllegalArgumentException.class, () -> Settings.fromEnvironment(env), name + value);
+                assertTrue(e.getMessage().contains(name));
+            }
+        }
+    }
+}

backend/src/test/java/home/backend/adapters/config/PresetFileTest.java

@@ -0,0 +1,68 @@
+package home.backend.adapters.config;
+
+import home.backend.domain.Preset;
+import home.backend.domain.Preset.Change;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class PresetFileTest {
+
+    @TempDir
+    Path dir;
+
+    private Path file(String json) throws IOException {
+        return Files.writeString(dir.resolve("presets.json"), json);
+    }
+
+    @Test
+    void defaultsAreBoostAndAway() {
+        var presets = PresetFile.load(null);
+
+        assertEquals(List.of(
+                new Preset("cwu-now", "Ciepła woda teraz", null, List.of(new Change("cwu_economy", 45, 2.0))),
+                new Preset("away", "Wyjazd", "chosen", List.of(new Change("cwu_comfort", 10, null),
+                        new Change("co_comfort", 15, null)))), presets);
+    }
+
+    @Test
+    void fileReplacesTheDefaults() throws Exception {
+        var presets = PresetFile.load(file("""
+                [{"id": "bath", "name": "Kąpiel", "changes": [{"setpoint": "cwu_economy", "value": 48, "hours": 1.5}]}]
+                """));
+
+        assertEquals(List.of(new Preset("bath", "Kąpiel", null, List.of(new Change("cwu_economy", 48, 1.5)))), presets);
+    }
+
+    @Test
+    void unusableFilesAreRefusedWithTheirName() throws Exception {
+        for (String json : List.of(
+                "not json",
+                "{}",
+                "[{\"id\": \"a\", \"name\": \"A\", \"changes\": []}]",
+                "[{\"id\": \"\", \"name\": \"A\", \"changes\": [{\"setpoint\": \"co_comfort\", \"value\": 15}]}]",
+                "[{\"id\": \"a\", \"name\": \"A\", \"changes\": [{\"setpoint\": \"co_comfort\", \"value\": 15, \"hours\": 0}]}]",
+                "[{\"id\": \"a\", \"name\": \"A\", \"changes\": [{\"setpoint\": \"co_comfort\", \"value\": 15, \"hours\": 73}]}]",
+                "[{\"id\": \"a\", \"name\": \"A\", \"until\": \"tomorrow\", \"changes\": [{\"setpoint\": \"co_comfort\", \"value\": 15}]}]",
+                "[{\"id\": \"a\", \"name\": \"A\", \"until\": \"chosen\", \"changes\": [{\"setpoint\": \"co_comfort\", \"value\": 15, \"hours\": 2}]}]",
+                "[{\"id\": \"a\", \"name\": \"A\", \"changes\": [{\"setpoint\": \"co_comfort\", \"value\": 15}]},"
+                        + "{\"id\": \"a\", \"name\": \"B\", \"changes\": [{\"setpoint\": \"co_comfort\", \"value\": 16}]}]")) {
+            Path file = file(json);
+            var e = assertThrows(IllegalArgumentException.class, () -> PresetFile.load(file), json);
+            assertTrue(e.getMessage().contains("PRESETS_FILE"), e.getMessage());
+        }
+    }
+
+    @Test
+    void missingFileIsRefused() {
+        assertThrows(IllegalArgumentException.class, () -> PresetFile.load(dir.resolve("absent.json")));
+    }
+}

backend/src/test/java/home/backend/adapters/gateway/GatewayHttpClientTest.java

@@ -0,0 +1,187 @@
+package home.backend.adapters.gateway;
+
+import com.sun.net.httpserver.HttpServer;
+import home.backend.domain.GatewaySnapshot.DeviceSnapshot;
+import home.backend.domain.GatewaySnapshot.Measurement;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.net.URI;
+import java.net.http.HttpTimeoutException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class GatewayHttpClientTest {
+
+    private HttpServer server;
+    private GatewayHttpClient client;
+
+    @BeforeEach
+    void startServer() throws IOException {
+        server = HttpServer.create(new InetSocketAddress("127.0.0.1", 0), 0);
+        server.start();
+        client = new GatewayHttpClient(URI.create("http://127.0.0.1:" + server.getAddress().getPort()),
+                Duration.ofMillis(500));
+    }
+
+    @AfterEach
+    void stopServer() {
+        server.stop(0);
+    }
+
+    private void serve(String path, int status, String body) {
+        server.createContext(path, exchange -> {
+            byte[] bytes = body.getBytes(StandardCharsets.UTF_8);
+            exchange.sendResponseHeaders(status, bytes.length);
+            exchange.getResponseBody().write(bytes);
+            exchange.close();
+        });
+    }
+
+    private void serveFiles(int healthStatus, String healthFile, String snapshotFile) throws IOException {
+        serve("/health", healthStatus, resource(healthFile));
+        serve("/snapshot", 200, resource(snapshotFile));
+    }
+
+    private static String resource(String name) throws IOException {
+        return Files.readString(Path.of("src/test/resources/gateway", name));
+    }
+
+    private static DeviceSnapshot device(List<DeviceSnapshot> devices, String name) {
+        return devices.stream().filter(d -> d.name().equals(name)).findFirst().orElseThrow();
+    }
+
+    @Test
+    void mapsEveryDeviceWithItsMeasurements() throws Exception {
+        serveFiles(200, "health-all-up.json", "snapshot-all-up.json");
+
+        var devices = client.snapshot().devices();
+
+        assertEquals(List.of("bme280", "deye", "fronius", "heat-pump", "house-meter"),
+                devices.stream().map(DeviceSnapshot::name).toList());
+        assertTrue(devices.stream().allMatch(DeviceSnapshot::up));
+        DeviceSnapshot pump = device(devices, "heat-pump");
+        assertEquals(Instant.parse("2026-10-23T22:26:00Z"), pump.lastSuccess());
+        assertNull(pump.lastError());
+        assertEquals(List.of("POMPA", "heat_pump"), pump.measurements().stream().map(Measurement::measurement).toList());
+        var measurement = pump.measurements().get(1);
+        assertEquals("Dom_Pompa", measurement.database());
+        assertEquals(4.3, measurement.fields().get("outdoor_temp"), 1e-9);
+        assertEquals(45.0, measurement.fields().get("setpoint_cwu_comfort"), 1e-9);
+        assertEquals(Instant.parse("2026-10-23T22:26:00Z"), measurement.time());
+        assertEquals(645.0, device(devices, "deye").measurements().get(0).fields().get("grid_power_w"));
+    }
+
+    @Test
+    void readsTheGatewayVersion() throws Exception {
+        serveFiles(200, "health-all-up.json", "snapshot-all-up.json");
+
+        assertEquals("v1.2.1", client.snapshot().version());
+    }
+
+    @Test
+    void anOldGatewayWithoutVersionHasNullVersion() throws Exception {
+        serveFiles(503, "health-one-down.json", "snapshot-one-down.json");
+
+        assertNull(client.snapshot().version());
+    }
+
+    @Test
+    void aDownDeviceAnswering503IsStillASnapshot() throws Exception {
+        serveFiles(503, "health-one-down.json", "snapshot-one-down.json");
+
+        var devices = client.snapshot().devices();
+
+        assertTrue(device(devices, "heat-pump").up());
+        DeviceSnapshot deye = device(devices, "deye");
+        assertFalse(deye.up());
+        assertEquals("Connect timed out", deye.lastError());
+        assertEquals(Instant.parse("2026-10-23T22:20:00Z"), deye.lastSuccess());
+        // The last good reading stays available, with its own time.
+        var last = deye.measurements().get(0);
+        assertEquals(570.0, last.fields().get("load_power_w"));
+        assertEquals(Instant.parse("2026-10-23T22:20:00Z"), last.time());
+    }
+
+    @Test
+    void aDeviceThatNeverSucceededHasNoLastSuccessAndNoMeasurements() throws Exception {
+        serveFiles(503, "health-never-succeeded.json", "snapshot-never-succeeded.json");
+
+        var devices = client.snapshot().devices();
+
+        var pump = device(devices, "heat-pump");
+        assertFalse(pump.up());
+        assertNull(pump.lastSuccess());
+        assertEquals("Connection refused", pump.lastError());
+        assertTrue(pump.measurements().isEmpty());
+        assertTrue(device(devices, "deye").up());
+    }
+
+    @Test
+    void ignoresPropertiesItDoesNotKnow() throws Exception {
+        serve("/health", 200, """
+                {"status":"UP","version":"2","devices":[{"name":"x","status":"UP","lastSuccess":null,"lastError":null,"extra":1}]}""");
+        serve("/snapshot", 200, """
+                [{"name":"x","new":true,"readings":[{"database":"d","measurement":"m","tags":{},
+                "fields":{"a":1.0},"time":"2026-10-24T10:00:00Z","unit":"C"}]}]""");
+
+        assertEquals(1, client.snapshot().devices().get(0).measurements().size());
+    }
+
+    @Test
+    void failsWhenSnapshotAnswers503() throws Exception {
+        serve("/health", 200, resource("health-all-up.json"));
+        serve("/snapshot", 503, "[]");
+
+        assertThrows(IOException.class, client::snapshot);
+    }
+
+    @Test
+    void failsOnServerError() {
+        serve("/health", 500, "{\"error\":\"boom\"}");
+
+        assertThrows(IOException.class, client::snapshot);
+    }
+
+    @Test
+    void failsOnBadJson() {
+        serve("/health", 200, "<html>not json</html>");
+
+        assertThrows(IOException.class, client::snapshot);
+    }
+
+    @Test
+    void failsWhenTheGatewayIsSlowerThanTheTimeout() {
+        server.createContext("/health", exchange -> {
+            try {
+                Thread.sleep(2000);
+            } catch (InterruptedException ignored) {
+                // the client gave up; nothing to answer
+            }
+            exchange.close();
+        });
+
+        assertThrows(HttpTimeoutException.class, client::snapshot);
+    }
+
+    @Test
+    void failsWhenTheGatewayIsUnreachable() {
+        server.stop(0);
+
+        assertThrows(IOException.class, client::snapshot);
+    }
+}

backend/src/test/java/home/backend/adapters/gateway/GatewayHttpCommandsTest.java

@@ -0,0 +1,348 @@
+package home.backend.adapters.gateway;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.sun.net.httpserver.HttpExchange;
+import com.sun.net.httpserver.HttpServer;
+import home.backend.domain.BatteryChange;
+import home.backend.domain.BatteryResult;
+import home.backend.domain.BatteryView;
+import home.backend.domain.Command;
+import home.backend.domain.CommandResult.Status;
+import home.backend.domain.RestoreResult.Outcome;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.URI;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.time.Duration;
+import java.time.Instant;
+import java.time.LocalTime;
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/** Against a stub gateway on localhost; the bodies are the gateway's own examples (the contract). */
+class GatewayHttpCommandsTest {
+
+    private static final ObjectMapper JSON = new ObjectMapper();
+    private static final Path CONTRACT = Path.of("../gateway/src/test/resources/commands");
+
+    private record Seen(String method, String path, String authorization, String requestedBy, String body) {
+    }
+
+    private final List<Seen> seen = new ArrayList<>();
+    private HttpServer server;
+
+    @BeforeEach
+    void startServer() throws IOException {
+        server = HttpServer.create(new InetSocketAddress(InetAddress.getLoopbackAddress(), 0), 0);
+        answerCommands();
+        server.start();
+    }
+
+    @AfterEach
+    void stopServer() {
+        server.stop(0);
+    }
+
+    private int status;
+    private String body = "{}";
+
+    private void serve(int status, String body) {
+        this.status = status;
+        this.body = body;
+    }
+
+    private void answerCommands() {
+        for (String path : List.of("/commands", "/battery")) {
+            server.createContext(path, this::answer);
+        }
+    }
+
+    private void answer(HttpExchange exchange) throws IOException {
+        seen.add(new Seen(exchange.getRequestMethod(), exchange.getRequestURI().getPath(),
+                exchange.getRequestHeaders().getFirst("Authorization"),
+                exchange.getRequestHeaders().getFirst("X-Requested-By"),
+                new String(exchange.getRequestBody().readAllBytes(), StandardCharsets.UTF_8)));
+        byte[] bytes = body.getBytes(StandardCharsets.UTF_8);
+        exchange.sendResponseHeaders(status, bytes.length);
+        exchange.getResponseBody().write(bytes);
+        exchange.close();
+    }
+
+    private GatewayHttpCommands commands(String token) {
+        return new GatewayHttpCommands(URI.create("http://127.0.0.1:" + server.getAddress().getPort()), token,
+                Duration.ofMillis(500));
+    }
+
+    private static String contract(String name) throws IOException {
+        return Files.readString(CONTRACT.resolve(name));
+    }
+
+    @Test
+    void sendsTheBoostWithTokenUserAndMinutes() throws Exception {
+        serve(200, contract("response-applied.json"));
+
+        var result = commands("s3cret-token").apply(new Command("cwu_economy", 45, Duration.ofHours(2), "anna"));
+
+        assertEquals(Status.APPLIED, result.status());
+        assertEquals(Instant.parse("2026-10-24T12:00:00Z"), result.restoreAt());
+        assertEquals(1, seen.size());
+        assertEquals("POST", seen.getFirst().method());
+        assertEquals("Bearer s3cret-token", seen.getFirst().authorization());
+        assertEquals("anna", seen.getFirst().requestedBy());
+        assertEquals(contractJson("request-boost.json"), contractJson(seen.getFirst().body()));
+    }
+
+    @Test
+    void aHeldChangeSendsTheEndAsUntil() throws Exception {
+        serve(200, contract("response-applied.json"));
+
+        commands("s3cret-token").apply(new Command("cwu_comfort", 10, null, Instant.parse("2026-11-02T17:00:00Z"), "phone"));
+
+        assertEquals(contractJson("request-held.json"), contractJson(seen.getFirst().body()));
+    }
+
+    @Test
+    void awayHasNoMinutes() throws Exception {
+        serve(200, contract("response-applied.json"));
+
+        commands("s3cret-token").apply(new Command("cwu_comfort", 10, null, "phone"));
+
+        assertEquals(contractJson("request-away.json"), contractJson(seen.getFirst().body()));
+    }
+
+    @Test
+    void rejectionIsAVerdictNotAnError() throws Exception {
+        serve(422, contract("response-rejected.json"));
+
+        var result = commands("s3cret-token").apply(new Command("cwu_economy", 60, null, "phone"));
+
+        assertEquals(Status.REJECTED, result.status());
+        assertEquals("cwu_economy allows 5–48 in steps of 1, not 60", result.message());
+        assertNull(result.restoreAt());
+    }
+
+    @Test
+    void failedWriteIsAVerdict() throws Exception {
+        serve(502, "{\"status\":\"FAILED\",\"message\":\"read back 8, expected 45\",\"restoreAt\":null}");
+
+        assertEquals(Status.FAILED, commands("s3cret-token").apply(new Command("cwu_economy", 45, null, "phone")).status());
+    }
+
+    @Test
+    void readsSetpointsWithRestores() throws Exception {
+        serve(200, contract("setpoints.json"));
+
+        var state = commands("s3cret-token").setpoints();
+
+        assertEquals("GET", seen.getFirst().method());
+        assertEquals("Bearer s3cret-token", seen.getFirst().authorization());
+        assertEquals(4, state.setpoints().size());
+        assertEquals(48, state.setpoints().get(2).max());
+        assertEquals(1, state.restores().size());
+        assertEquals(8, state.restores().getFirst().originalValue());
+    }
+
+    @Test
+    void anUntilChangedRestoreHasNoDue() throws Exception {
+        serve(200, "{\"setpoints\":[],\"restores\":[{\"setpoint\":\"cwu_comfort\",\"register\":4144,"
+                + "\"originalValue\":45,\"appliedValue\":10,\"leaseUntil\":\"2026-10-24T10:15:00Z\"}]}");
+
+        assertNull(commands("s3cret-token").setpoints().restores().getFirst().due());
+    }
+
+    @Test
+    void restorePostsTheSetpointWithTokenAndUser() throws Exception {
+        serve(200, contract("response-restored.json"));
+
+        var result = commands("s3cret-token").restore("cwu_economy", "anna");
+
+        assertEquals(Outcome.RESTORED, result.outcome());
+        assertEquals("POST", seen.getFirst().method());
+        assertEquals("/commands/restore", seen.getFirst().path());
+        assertEquals("Bearer s3cret-token", seen.getFirst().authorization());
+        assertEquals("anna", seen.getFirst().requestedBy());
+        assertEquals(contractJson("request-restore.json"), contractJson(seen.getFirst().body()));
+    }
+
+    @Test
+    void aConflictOnRestoreIsAVerdictNotAnError() throws Exception {
+        serve(409, contract("response-restore-conflict.json"));
+
+        assertEquals(Outcome.CONFLICT, commands("s3cret-token").restore("cwu_economy", "anna").outcome());
+    }
+
+    @Test
+    void everyRestoreStatusOfTheGatewayIsAVerdict() throws Exception {
+        var expected = java.util.Map.of(404, Outcome.NOT_PENDING, 429, Outcome.TOO_SOON, 502, Outcome.FAILED);
+        for (var entry : expected.entrySet()) {
+            serve(entry.getKey(), "{\"outcome\":\"" + entry.getValue() + "\",\"message\":\"x\"}");
+
+            assertEquals(entry.getValue(), commands("s3cret-token").restore("cwu_economy", "anna").outcome());
+        }
+    }
+
+    @Test
+    void restoreFailsWithoutAVerdictOrToken() {
+        serve(503, "{\"error\":\"x\"}");
+        assertThrows(IOException.class, () -> commands("s3cret-token").restore("cwu_economy", "anna"));
+
+        var seenBefore = seen.size();
+        assertThrows(IOException.class, () -> commands(null).restore("cwu_economy", "anna"));
+        assertEquals(seenBefore, seen.size());
+    }
+
+    @Test
+    void renewPostsToRenewWithTheTokenAndReturnsHowManyWereExtended() throws Exception {
+        serve(200, "{\"renewed\":2}");
+
+        assertEquals(2, commands("s3cret-token").renewLeases());
+
+        assertEquals("POST", seen.getFirst().method());
+        assertEquals("/commands/renew", seen.getFirst().path());
+        assertEquals("Bearer s3cret-token", seen.getFirst().authorization());
+    }
+
+    @Test
+    void renewFailsOnAnyOtherStatusOrWithoutToken() {
+        serve(503, "{\"error\":\"x\"}");
+        assertThrows(IOException.class, () -> commands("s3cret-token").renewLeases());
+
+        var seenBefore = seen.size();
+        assertThrows(IOException.class, () -> commands(null).renewLeases());
+        assertEquals(seenBefore, seen.size());
+    }
+
+    @Test
+    void readsTheBatteryReserveWithTheToken() throws Exception {
+        serve(200, contract("battery-reserve.json"));
+
+        var reserve = commands("s3cret-token").reserve();
+
+        assertEquals(new BatteryView.Reserve(50, 30), reserve);
+        assertEquals("GET", seen.getFirst().method());
+        assertEquals("/battery/reserve", seen.getFirst().path());
+        assertEquals("Bearer s3cret-token", seen.getFirst().authorization());
+    }
+
+    @Test
+    void sendsAScheduleChangeAsTheGatewayExpectsIt() throws Exception {
+        serve(200, contract("response-battery-applied.json"));
+        var change = new BatteryChange(true, List.of(new BatteryChange.Slot(2, LocalTime.of(9, 30), 90, true),
+                new BatteryChange.Slot(3, null, 85, null)));
+
+        var result = commands("s3cret-token").changeSchedule(change, "anna");
+
+        assertEquals(BatteryResult.Status.APPLIED, result.status());
+        assertEquals(java.util.Map.of(167, 90, 172, 1), result.read());
+        assertEquals("POST", seen.getFirst().method());
+        assertEquals("/battery/schedule", seen.getFirst().path());
+        assertEquals("Bearer s3cret-token", seen.getFirst().authorization());
+        assertEquals("anna", seen.getFirst().requestedBy());
+        assertEquals(contractJson("request-battery-schedule.json"), contractJson(seen.getFirst().body()));
+    }
+
+    @Test
+    void sendsAReserveChange() throws Exception {
+        serve(200, contract("response-battery-applied.json"));
+
+        commands("s3cret-token").changeReserve(60, "anna");
+
+        assertEquals("/battery/reserve", seen.getFirst().path());
+        assertEquals(contractJson("{\"pct\":60}"), contractJson(seen.getFirst().body()));
+    }
+
+    @Test
+    void everyBatteryStatusOfTheGatewayIsAVerdict() throws Exception {
+        var expected = java.util.Map.of(422, BatteryResult.Status.REJECTED, 409, BatteryResult.Status.STALE,
+                429, BatteryResult.Status.TOO_SOON, 502, BatteryResult.Status.FAILED);
+        for (var entry : expected.entrySet()) {
+            serve(entry.getKey(), "{\"status\":\"" + entry.getValue() + "\",\"message\":\"x\",\"read\":{}}");
+
+            assertEquals(entry.getValue(), commands("s3cret-token").changeReserve(60, "anna").status());
+        }
+    }
+
+    @Test
+    void aFailedBatteryWriteCarriesWhatWasRead() throws Exception {
+        serve(502, contract("response-battery-failed.json"));
+
+        var result = commands("s3cret-token").changeSchedule(new BatteryChange(null, null), "anna");
+
+        assertEquals(BatteryResult.Status.FAILED, result.status());
+        assertEquals(java.util.Map.of(167, 80), result.read());
+    }
+
+    @Test
+    void batteryCallsFailWithoutAVerdictOrToken() {
+        for (int status : List.of(400, 401, 404, 503)) {
+            serve(status, "{\"error\":\"x\"}");
+            assertThrows(IOException.class, () -> commands("s3cret-token").reserve(), "GET " + status);
+            assertThrows(IOException.class, () -> commands("s3cret-token").changeReserve(60, "anna"), "POST " + status);
+        }
+        var seenBefore = seen.size();
+        assertThrows(IOException.class, () -> commands(null).reserve());
+        assertThrows(IOException.class, () -> commands(null).changeReserve(60, "anna"));
+        assertEquals(seenBefore, seen.size());
+    }
+
+    @Test
+    void aSetpointNotReadYetStaysNullInsteadOfZero() throws Exception {
+        serve(200, "{\"setpoints\":[{\"name\":\"co_comfort\",\"register\":4132,\"min\":5,\"max\":25,\"step\":1,"
+                + "\"value\":null}],\"restores\":[]}");
+
+        assertNull(commands("s3cret-token").setpoints().setpoints().getFirst().value());
+    }
+
+    @Test
+    void otherStatusesAreNoVerdict() throws Exception {
+        for (int status : List.of(401, 404, 500, 503)) {
+            serve(status, "{\"error\":\"x\"}");
+            assertThrows(IOException.class, () -> commands("s3cret-token").setpoints(), "GET " + status);
+            assertThrows(IOException.class,
+                    () -> commands("s3cret-token").apply(new Command("cwu_economy", 45, null, "phone")), "POST " + status);
+        }
+    }
+
+    @Test
+    void unreadableAnswerIsNoVerdict() {
+        serve(200, "<html>proxy</html>");
+
+        assertThrows(IOException.class,
+                () -> commands("s3cret-token").apply(new Command("cwu_economy", 45, null, "phone")));
+    }
+
+    @Test
+    void withoutTokenNothingIsSent() {
+        serve(200, "{}");
+        var commands = commands(null);
+
+        assertThrows(IOException.class, () -> commands.setpoints());
+        assertThrows(IOException.class, () -> commands.apply(new Command("cwu_economy", 45, null, "phone")));
+        assertTrue(seen.isEmpty());
+    }
+
+    @Test
+    void unreachableGatewayIsAnIOException() {
+        server.stop(0);
+
+        assertThrows(IOException.class, () -> commands("s3cret-token").setpoints());
+    }
+
+    /** A contract file by name, or JSON text as is, parsed so that formatting does not matter. */
+    private static JsonNode contractJson(String nameOrJson) throws IOException {
+        return JSON.readTree(nameOrJson.endsWith(".json") ? contract(nameOrJson) : nameOrJson);
+    }
+}

backend/src/test/java/home/backend/adapters/http/ApiServerTest.java

@@ -0,0 +1,945 @@
+package home.backend.adapters.http;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import home.backend.application.AuditRepository;
+import home.backend.application.AuditService;
+import home.backend.application.BatteryService;
+import home.backend.application.EnergyDetailsService;
+import home.backend.application.EnergyService;
+import home.backend.adapters.config.PresetFile;
+import home.backend.application.GatewayClient;
+import home.backend.application.GatewayBattery;
+import home.backend.application.GatewayCommands;
+import home.backend.application.SetpointService;
+import home.backend.domain.BatteryChange;
+import home.backend.domain.BatteryResult;
+import home.backend.domain.BatteryView.Reserve;
+import home.backend.domain.Command;
+import home.backend.domain.CommandResult;
+import home.backend.domain.CommandResult.Status;
+import home.backend.domain.RestoreResult;
+import home.backend.domain.RestoreResult.Outcome;
+import home.backend.domain.Restore;
+import home.backend.domain.Setpoint;
+import home.backend.domain.SetpointState;
+import home.backend.application.HealthService;
+import home.backend.application.HeatPumpService;
+import home.backend.application.HistoryRepository;
+import home.backend.application.HeatPumpSamples;
+import home.backend.application.HistoryService;
+import home.backend.application.StatsService;
+import home.backend.application.PiSensorService;
+import home.backend.application.WeatherService;
+import home.backend.domain.Forecast;
+import home.backend.domain.GatewaySnapshot;
+import home.backend.domain.GatewaySnapshot.DeviceSnapshot;
+import home.backend.domain.GatewaySnapshot.Measurement;
+import home.backend.domain.WeatherView.Warning;
+import home.backend.domain.HeatPumpSample;
+import home.backend.domain.HistoryView.Point;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.Socket;
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.nio.charset.StandardCharsets;
+import java.time.Clock;
+import java.time.Instant;
+import java.time.LocalDate;
+import java.time.OffsetDateTime;
+import java.time.ZoneOffset;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class ApiServerTest {
+
+    private static final ObjectMapper JSON = new ObjectMapper();
+    private static final Instant HEALTH_TIME = Instant.parse("2026-10-23T22:14:00Z");
+
+    private final HttpClient client = HttpClient.newHttpClient();
+    private GatewaySnapshot snapshot;
+    private boolean gatewayDown;
+    private boolean historyDown;
+    private boolean auditDown;
+    private HeatPumpSamples samples;
+    private RuntimeException gatewayBug;
+    private final List<Command> sent = new ArrayList<>();
+    private Status verdict;
+    private Outcome restoreOutcome;
+    private final List<String> restored = new ArrayList<>();
+    private boolean commandsDown;
+    private boolean batteryDown;
+    private BatteryResult.Status batteryVerdict;
+    private final List<String> batterySent = new ArrayList<>();
+    private int answersBeforeDrop;
+    private ApiServer server;
+
+    @BeforeEach
+    void start() throws IOException {
+        snapshot = exampleSnapshot();
+        GatewayClient gateway = () -> {
+            if (gatewayDown) {
+                throw new IOException("tunnel down");
+            }
+            if (gatewayBug != null) {
+                throw gatewayBug;
+            }
+            return snapshot;
+        };
+        HistoryRepository history = (series, from, to, max) -> {
+            if (historyDown) {
+                throw new IOException("influx down");
+            }
+            return List.of(new Point(Instant.parse("2026-10-23T10:00:00Z"), 14.1),
+                    new Point(Instant.parse("2026-10-23T11:00:00Z"), 38.5),
+                    new Point(Instant.parse("2026-10-23T12:00:00Z"), 44.2));
+        };
+        samples = (from, to) -> {
+            if (historyDown) {
+                throw new IOException("influx down");
+            }
+            return List.of(
+                    new HeatPumpSample(Instant.parse("2026-10-23T10:00:00Z"), 0.0, 0.0, 0.0, 0.0, 8.0, 44.0),
+                    new HeatPumpSample(Instant.parse("2026-10-23T10:05:00Z"), 100.0, 100.0, 0.0, 0.0, 8.5, 43.0),
+                    new HeatPumpSample(Instant.parse("2026-10-23T10:10:00Z"), 100.0, 0.0, 0.0, 100.0, 9.0, 45.0),
+                    new HeatPumpSample(Instant.parse("2026-10-23T10:15:00Z"), 0.0, 0.0, 0.0, 0.0, 9.0, 46.0));
+        };
+        verdict = Status.APPLIED;
+        restoreOutcome = Outcome.RESTORED;
+        answersBeforeDrop = Integer.MAX_VALUE;
+        GatewayCommands commands = new GatewayCommands() {
+            @Override
+            public CommandResult apply(Command command) throws IOException {
+                if (commandsDown || sent.size() >= answersBeforeDrop) {
+                    throw new IOException("tunnel down");
+                }
+                sent.add(command);
+                return switch (verdict) {
+                    case APPLIED -> new CommandResult(verdict, "cwu_economy 8 → 45, restore at 2026-10-24T12:00:00Z",
+                            command.duration() == null ? null : Instant.parse("2026-10-24T12:00:00Z"));
+                    case REJECTED -> new CommandResult(verdict, "cwu_economy allows 5–48 in steps of 1, not 60", null);
+                    case FAILED -> new CommandResult(verdict, "read back 8, expected 45", null);
+                };
+            }
+
+            @Override
+            public RestoreResult restore(String setpoint, String requestedBy) throws IOException {
+                if (commandsDown) {
+                    throw new IOException("tunnel down");
+                }
+                restored.add(setpoint + " by " + requestedBy);
+                return new RestoreResult(restoreOutcome, "restored to 8");
+            }
+
+            @Override
+            public SetpointState setpoints() throws IOException {
+                if (commandsDown) {
+                    throw new IOException("tunnel down");
+                }
+                return new SetpointState(List.of(new Setpoint("co_economy", 4131, 5, 25, 1, 18),
+                        new Setpoint("co_comfort", 4132, 5, 25, 1, 19),
+                        new Setpoint("cwu_economy", 4143, 5, 48, 1, 8),
+                        new Setpoint("cwu_comfort", 4144, 5, 48, 1, 45)),
+                        List.of(new Restore("cwu_economy", 4143, 8, 45, Instant.parse("2026-10-24T12:00:00Z"))));
+            }
+
+            @Override
+            public int renewLeases() {
+                return 0;
+            }
+        };
+        batteryDown = false;
+        batteryVerdict = BatteryResult.Status.APPLIED;
+        GatewayBattery batteryCommands = new GatewayBattery() {
+            @Override
+            public Reserve reserve() throws IOException {
+                if (batteryDown) {
+                    throw new IOException("gateway /battery/reserve answered 404");
+                }
+                return new Reserve(50, 30);
+            }
+
+            @Override
+            public BatteryResult changeSchedule(BatteryChange change, String requestedBy) throws IOException {
+                return answer("schedule " + change + " by " + requestedBy);
+            }
+
+            @Override
+            public BatteryResult changeReserve(int pct, String requestedBy) throws IOException {
+                return answer("reserve " + pct + " by " + requestedBy);
+            }
+
+            private BatteryResult answer(String what) throws IOException {
+                if (batteryDown) {
+                    throw new IOException("tunnel down");
+                }
+                batterySent.add(what);
+                return switch (batteryVerdict) {
+                    case APPLIED -> new BatteryResult(batteryVerdict, "applied", Map.of(167, 90));
+                    case FAILED -> new BatteryResult(batteryVerdict,
+                            "registers not as written: [167]; not retried", Map.of(167, 80));
+                    default -> new BatteryResult(batteryVerdict, "nope", Map.of());
+                };
+            }
+        };
+        Clock clock = Clock.fixed(HEALTH_TIME, ZoneOffset.UTC);
+        server = new ApiServer(0, new HeatPumpService(gateway, clock), new EnergyService(gateway, clock),
+                new EnergyDetailsService(gateway, clock),
+                new HealthService(gateway, clock, "v1.3.0"), new HistoryService(history, clock),
+                new SetpointService(commands, PresetFile.load(null)), new PiSensorService(gateway, clock),
+                new BatteryService(gateway, batteryCommands, clock),
+                new AuditService(auditRows(), clock), new StatsService(samples, clock),
+                new WeatherService(() -> exampleForecast(), () -> List.of(exampleWarning()),
+                        (from, to) -> exampleMeasuredPv(), clock));
+        server.start();
+    }
+
+    @AfterEach
+    void stop() {
+        server.stop();
+    }
+
+    private AuditRepository auditRows() {
+        return new AuditRepository() {
+            @Override
+            public List<Row> heatPump(Instant from, Instant to) throws IOException {
+                if (auditDown) {
+                    throw new IOException("influx down");
+                }
+                return List.of(
+                        new Row(Instant.parse("2026-10-24T08:00:00Z"), "cwu_economy", "restore", "APPLIED", 45.0, 8.0),
+                        new Row(Instant.parse("2026-10-23T07:00:00Z"), "co_comfort", "mariusz", "REJECTED", null, 22.0));
+            }
+
+            @Override
+            public List<Row> battery(Instant from, Instant to) {
+                return List.of(
+                        new Row(Instant.parse("2026-10-24T09:30:00Z"), "reserve", "mariusz", "APPLIED", 50.0, 60.0),
+                        new Row(Instant.parse("2026-10-23T18:00:00Z"), "174", "mariusz", "FAILED", 0.0, 1.0));
+            }
+        };
+    }
+
+    private static GatewaySnapshot exampleSnapshot() {
+        Map<String, Double> pump = new HashMap<>(Map.of("outdoor_temp", 4.3, "indoor_temp", 21.2,
+                "co_buffer_temp", 16.9, "cwu_temp", 13.6, "ground_in_temp", 16.0, "ground_out_temp", 14.3,
+                "pump_outlet_temp", 19.7, "outdoor_avg_temp", 4.8, "target_room_temp", 18.0));
+        pump.putAll(Map.of("target_co_temp", 31.0, "target_cwu_temp", 8.0, "pump_mode", 0.0,
+                "output_compressor", 0.0, "output_heater", 0.0, "alarm", 0.0,
+                "setpoint_co_economy", 18.0, "setpoint_co_comfort", 19.0, "setpoint_cwu_economy", 8.0));
+        pump.putAll(Map.of("setpoint_cwu_comfort", 45.0, "output_co", 0.0, "output_buffer", 0.0,
+                "output_circulation", 0.0, "output_ground", 0.0, "output_cwu", 0.0));
+        Instant pumpTime = Instant.parse("2026-10-23T22:13:35Z");
+        Instant energyTime = Instant.parse("2026-10-23T22:26:00Z");
+        Map<String, Double> deye = new HashMap<>(Map.of("pv1_power_w", 0.0, "pv2_power_w", 0.0, "pv_today_kwh", 29.9,
+                "grid_power_w", 645.0, "battery_power_w", -24.0, "battery_soc_pct", 99.0,
+                "load_power_w", 570.0, "grid_bought_today_kwh", 16.8, "grid_sold_today_kwh", 22.3,
+                "load_today_kwh", 24.2));
+        deye.putAll(Map.of("battery_voltage_v", 56.49, "battery_current_a", -0.05, "battery_temperature_c", 19.2,
+                "battery_charge_today_kwh", 0.5, "battery_discharge_today_kwh", 0.1,
+                "battery_charge_total_kwh", 453.7, "battery_discharge_total_kwh", 162.1));
+        return new GatewaySnapshot("v1.2.1", List.of(
+                new DeviceSnapshot("heat-pump", true, pumpTime, null,
+                        List.of(new Measurement("Dom_Pompa", "heat_pump", pump, energyTime))),
+                new DeviceSnapshot("deye", true, energyTime, null,
+                        List.of(new Measurement("home", "deye", deye, energyTime))),
+                new DeviceSnapshot("fronius", true, energyTime, null,
+                        List.of(new Measurement("home", "fronius",
+                                Map.of("pv_power_w", 0.0, "energy_day_wh", 4400.0), energyTime))),
+                new DeviceSnapshot("house-meter", true, energyTime, null,
+                        List.of(new Measurement("electricity", "PRAD2", Map.of("p1_voltage", 235.69,
+                                "p1_current", 0.32, "p1_power_active", 55.94, "p1_power_factor", 0.75,
+                                "frequency", 50.01, "import_energy_active", 67514.27), energyTime))),
+                new DeviceSnapshot("deye-settings", true, energyTime, null,
+                        List.of(new Measurement("electricity", "deye_settings", deyeSettings(), energyTime))),
+                new DeviceSnapshot("bme280", true, energyTime, null,
+                        List.of(new Measurement("measurement", "MEASUREMENT",
+                                Map.of("temperature", 20.17, "humidity", 45.82, "pressure", 985.8), energyTime)))));
+    }
+
+    /** The settings read from the inverter on 2026-10-24: time of use off, six 4-hour slots. */
+    private static Map<String, Double> deyeSettings() {
+        Map<String, Double> settings = new HashMap<>(Map.of("battery_capacity_ah", 280.0, "tou_enabled", 0.0,
+                "max_charge_current_a", 80.0, "max_discharge_current_a", 120.0, "shutdown_soc_pct", 20.0,
+                "low_soc_pct", 35.0, "restart_soc_pct", 50.0, "grid_charge_enabled", 1.0,
+                "grid_charge_current_a", 40.0, "grid_charge_start_soc_pct", 30.0));
+        double[] starts = {100, 500, 900, 1300, 1700, 2100};
+        for (int slot = 1; slot <= 6; slot++) {
+            settings.put("prog" + slot + "_start_hhmm", starts[slot - 1]);
+            settings.put("prog" + slot + "_power_w", 10000.0);
+            settings.put("prog" + slot + "_soc_pct", 80.0);
+            settings.put("prog" + slot + "_grid_charge", 0.0);
+        }
+        return settings;
+    }
+
+    private HttpResponse<String> get(String path) throws Exception {
+        HttpRequest request = HttpRequest.newBuilder(URI.create("http://localhost:" + server.port() + path))
+                .build();
+        return client.send(request, HttpResponse.BodyHandlers.ofString());
+    }
+
+    private static String awayRequest() throws IOException {
+        return example("preset-away-request").toString();
+    }
+
+    private static JsonNode example(String name) throws IOException {
+        try (InputStream in = ApiServerTest.class.getResourceAsStream("/api/" + name + ".json")) {
+            return JSON.readTree(in);
+        }
+    }
+
+    private void assertMatchesExample(String path, String example) throws Exception {
+        HttpResponse<String> response = get(path);
+
+        assertEquals(200, response.statusCode());
+        assertEquals("application/json", response.headers().firstValue("Content-Type").orElseThrow());
+        assertEquals("no-store", response.headers().firstValue("Cache-Control").orElseThrow());
+        assertEquals(example(example), JSON.readTree(response.body()));
+    }
+
+    @Test
+    void heatPumpMatchesExample() throws Exception {
+        assertMatchesExample("/api/heat-pump", "heat-pump");
+    }
+
+    @Test
+    void energyMatchesExample() throws Exception {
+        assertMatchesExample("/api/energy", "energy");
+    }
+
+    @Test
+    void energyDetailsMatchExample() throws Exception {
+        assertMatchesExample("/api/energy/details", "energy-details");
+    }
+
+    @Test
+    void healthMatchesExample() throws Exception {
+        snapshot = new GatewaySnapshot("v1.2.1", List.of(snapshot.devices().get(0),
+                new DeviceSnapshot("deye", false, null, "connect timed out", List.of())));
+        assertMatchesExample("/api/health", "health");
+    }
+
+    @Test
+    void heatPumpWithoutReadingMatchesUnreadExample() throws Exception {
+        snapshot = new GatewaySnapshot("v1.2.1", List.of());
+        assertMatchesExample("/api/heat-pump", "heat-pump-unread");
+    }
+
+    @Test
+    void staleDeyeMatchesExample() throws Exception {
+        Instant old = Instant.parse("2026-10-23T21:00:00Z");
+        List<DeviceSnapshot> devices = new ArrayList<>(snapshot.devices());
+        Measurement deye = devices.get(1).measurements().get(0);
+        devices.set(1, new DeviceSnapshot("deye", true, old, null,
+                List.of(new Measurement("home", "deye", deye.fields(), old))));
+        snapshot = new GatewaySnapshot("v1.2.1", devices);
+        assertMatchesExample("/api/energy", "energy-deye-stale");
+    }
+
+    @Test
+    void batteryMatchesExample() throws Exception {
+        assertMatchesExample("/api/battery", "battery");
+    }
+
+    @Test
+    void batteryWithStaleSettingsMatchesExample() throws Exception {
+        Instant old = Instant.parse("2026-10-23T21:00:00Z");
+        List<DeviceSnapshot> devices = new ArrayList<>(snapshot.devices());
+        devices.set(devices.size() - 2, new DeviceSnapshot("deye-settings", true, old, null,
+                List.of(new Measurement("electricity", "deye_settings", deyeSettings(), old))));
+        snapshot = new GatewaySnapshot("v1.2.1", devices);
+        assertMatchesExample("/api/battery", "battery-settings-stale");
+    }
+
+    @Test
+    void batteryWithoutGatewayCommandsIsNotEditable() throws Exception {
+        batteryDown = true;
+
+        var body = JSON.readTree(get("/api/battery").body());
+
+        assertTrue(body.get("reserve").isNull());
+        assertEquals(false, body.get("editable").asBoolean());
+        assertEquals(99.0, body.get("socPct").asDouble());
+    }
+
+    @Test
+    void scheduleChangeGoesToTheGatewayWithTheUserAndAnswersWithTheVerdict() throws Exception {
+        var response = post("/api/battery/schedule", example("battery-schedule-request").toString(),
+                "Remote-User", "anna");
+
+        assertEquals(200, response.statusCode());
+        assertEquals(List.of("schedule " + new BatteryChange(true, List.of(
+                new BatteryChange.Slot(2, java.time.LocalTime.of(9, 30), 90, true),
+                new BatteryChange.Slot(3, null, 85, null))) + " by anna"), batterySent);
+        assertEquals(JSON.readTree("{\"status\":\"APPLIED\",\"message\":\"applied\",\"read\":{\"167\":90}}"),
+                JSON.readTree(response.body()));
+    }
+
+    @Test
+    void reserveChangeGoesToTheGateway() throws Exception {
+        var response = post("/api/battery/reserve", example("battery-reserve-request").toString());
+
+        assertEquals(200, response.statusCode());
+        assertEquals(List.of("reserve 60 by phone"), batterySent);
+    }
+
+    @Test
+    void batteryStatusFollowsTheGatewaysVerdict() throws Exception {
+        var expected = Map.of(BatteryResult.Status.REJECTED, 422, BatteryResult.Status.STALE, 409,
+                BatteryResult.Status.TOO_SOON, 429, BatteryResult.Status.FAILED, 502);
+        for (var entry : expected.entrySet()) {
+            batteryVerdict = entry.getKey();
+
+            assertEquals(entry.getValue(), post("/api/battery/reserve", "{\"pct\":60}").statusCode());
+            assertEquals(entry.getValue(), post("/api/battery/schedule", "{\"enabled\":false}").statusCode());
+        }
+        batteryVerdict = BatteryResult.Status.FAILED;
+        assertEquals(example("battery-failed"),
+                JSON.readTree(post("/api/battery/schedule", "{\"enabled\":false}").body()));
+    }
+
+    @Test
+    void batteryChangeWithTheGatewayDownIs503() throws Exception {
+        batteryDown = true;
+
+        assertEquals(503, post("/api/battery/reserve", "{\"pct\":60}").statusCode());
+        assertEquals(503, post("/api/battery/schedule", "{\"enabled\":false}").statusCode());
+    }
+
+    @Test
+    void badBatteryRequestsAre400AndSendNothing() throws Exception {
+        for (String body : List.of("", "not json", "[]", "{}", "{\"pct\":\"60\"}", "{\"pct\":60.5}", "{\"pct\":null}",
+                "{\"pct\":60,\"x\":1}")) {
+            assertEquals(400, post("/api/battery/reserve", body).statusCode(), body);
+        }
+        for (String body : List.of("", "not json", "[]", "{\"enabled\":\"yes\"}", "{\"slots\":[{\"slot\":1,\"from\":\"9h\"}]}",
+                "{\"slots\":[{\"slot\":1,\"from\":\"25:00\"}]}", "{\"slots\":[{\"slot\":1,\"socPct\":\"9\"}]}",
+                "{\"slots\":[{\"slot\":1,\"soc\":9}]}", "{\"slots\":[{\"slot\":1,\"gridCharge\":1}]}")) {
+            assertEquals(400, post("/api/battery/schedule", body).statusCode(), body);
+        }
+        assertTrue(batterySent.isEmpty());
+    }
+
+    @Test
+    void batteryWritesAreGuardedLikeEveryWrite() throws Exception {
+        for (String path : List.of("/api/battery/reserve", "/api/battery/schedule")) {
+            assertEquals(415, rawPost(path, "{}", "X-Requested-With", "home-pump").statusCode(), path);
+            assertEquals(403, rawPost(path, "{}", "Content-Type", "application/json").statusCode(), path);
+            assertEquals(403, post(path, "{}", "Origin", "https://evil.example").statusCode(), path);
+            assertEquals(405, get(path).statusCode(), path);
+        }
+        assertEquals(404, post("/api/battery/other", "{}").statusCode());
+        assertTrue(batterySent.isEmpty());
+    }
+
+    private static Forecast exampleForecast() {
+        Map<LocalDate, Forecast.DailyForecast> days = new TreeMap<>();
+        for (int i = 0; i < 5; i++) {
+            days.put(LocalDate.parse("2026-10-19").plusDays(i), new Forecast.DailyForecast(3, 12.0, 4.0, 0.0, 10.0, 7200.0));
+        }
+        days.put(LocalDate.parse("2026-10-24"), new Forecast.DailyForecast(3, 10.9, 3.8, 0.0, 9.0, 7151.0));
+        days.put(LocalDate.parse("2026-10-25"), new Forecast.DailyForecast(51, 13.2, 4.0, 0.3, 4.5, 28314.0));
+        days.put(LocalDate.parse("2026-10-26"), new Forecast.DailyForecast(61, 9.6, 4.1, 8.4, 2.1, 0.0));
+        return new Forecast(10.6, days);
+    }
+
+    /** Twice the forecast radiation of the same days, so the factor is 2 kWh per MJ/m². */
+    private static Map<LocalDate, Double> exampleMeasuredPv() {
+        Map<LocalDate, Double> measured = new HashMap<>();
+        for (int i = 0; i < 5; i++) {
+            measured.put(LocalDate.parse("2026-10-19").plusDays(i), 20.0);
+        }
+        return measured;
+    }
+
+    private static Warning exampleWarning() {
+        return new Warning("Silny wiatr", 2, OffsetDateTime.parse("2026-10-25T08:00:00+01:00"),
+                OffsetDateTime.parse("2026-10-25T18:00:00+01:00"),
+                "Prognozuje się wystąpienie silnego wiatru o średniej prędkości do 45 km/h.");
+    }
+
+    @Test
+    void weatherMatchesExample() throws Exception {
+        assertMatchesExample("/api/weather", "weather");
+    }
+
+    @Test
+    void piSensorMatchesExample()throws Exception {
+        assertMatchesExample("/api/pi-sensor", "pi-sensor");
+    }
+
+    @Test
+    void stalePiSensorMatchesExample() throws Exception {
+        Instant old = Instant.parse("2026-10-23T21:00:00Z");
+        List<DeviceSnapshot> devices = new ArrayList<>(snapshot.devices());
+        Measurement bme = devices.getLast().measurements().get(0);
+        devices.set(devices.size() - 1, new DeviceSnapshot("bme280", true, old, null,
+                List.of(new Measurement(bme.database(), bme.measurement(), bme.fields(), old))));
+        snapshot = new GatewaySnapshot("v1.2.1", devices);
+        assertMatchesExample("/api/pi-sensor", "pi-sensor-stale");
+    }
+
+    @Test
+    void historyMatchesExample() throws Exception {
+        assertMatchesExample("/api/history?series=cwu_temp&range=24h", "history");
+    }
+
+    @Test
+    void statsMatchExample() throws Exception {
+        assertMatchesExample("/api/stats?range=7d", "stats");
+    }
+
+    @Test
+    void statsNeedAKnownRange() throws Exception {
+        assertEquals(400, get("/api/stats").statusCode());
+        assertEquals(400, get("/api/stats?range=24h").statusCode());
+        assertEquals(200, get("/api/stats?range=30d").statusCode());
+    }
+
+    @Test
+    void statsAre502WhenInfluxIsDown() throws Exception {
+        historyDown = true;
+
+        assertEquals(502, get("/api/stats?range=7d").statusCode());
+    }
+
+    @Test
+    void historyRangeDefaultsTo24Hours() throws Exception {
+        assertEquals(200, get("/api/history?series=cwu_temp").statusCode());
+    }
+
+    @Test
+    void auditMatchesExample() throws Exception {
+        assertMatchesExample("/api/audit?range=7d", "audit");
+    }
+
+    @Test
+    void auditRangeDefaultsAndIsChecked() throws Exception {
+        assertEquals(200, get("/api/audit").statusCode());
+        assertEquals(400, get("/api/audit?range=90d").statusCode());
+    }
+
+    @Test
+    void auditInfluxFailureIs502() throws Exception {
+        auditDown = true;
+
+        assertEquals(502, get("/api/audit?range=7d").statusCode());
+    }
+
+    @Test
+    void unreachableGatewayIs503WithJsonError() throws Exception {
+        gatewayDown = true;
+
+        for (String path : List.of("/api/heat-pump", "/api/energy", "/api/energy/details")) {
+            HttpResponse<String> response = get(path);
+            assertEquals(503, response.statusCode());
+            assertEquals("gateway unreachable", JSON.readTree(response.body()).get("error").asText());
+        }
+    }
+
+    @Test
+    void healthStaysOkWhenGatewayIsUnreachable() throws Exception {
+        gatewayDown = true;
+
+        HttpResponse<String> response = get("/api/health");
+
+        assertEquals(200, response.statusCode());
+        assertEquals(false, JSON.readTree(response.body()).get("gatewayReachable").asBoolean());
+    }
+
+    @Test
+    void unknownSeriesOrRangeIs400() throws Exception {
+        assertEquals(400, get("/api/history?series=nope").statusCode());
+        assertEquals(400, get("/api/history").statusCode());
+        assertEquals(400, get("/api/history?series=cwu_temp&range=30d").statusCode());
+    }
+
+    @Test
+    void malformedQueryIs400NotADroppedConnection() throws Exception {
+        for (String path : List.of("/api/history?series=%", "/api/history?series=%zz&range=24h")) {
+            assertEquals(400, rawGet(path), path);
+        }
+    }
+
+    @Test
+    void unusableGatewayPayloadIs502() throws Exception {
+        for (RuntimeException bug : List.of(new IllegalStateException("Duplicate key deye"),
+                new NullPointerException("status"))) {
+            gatewayBug = bug;
+            for (String path : List.of("/api/heat-pump", "/api/energy", "/api/health")) {
+                HttpResponse<String> response = get(path);
+                assertEquals(502, response.statusCode(), path);
+                assertEquals("bad gateway response", JSON.readTree(response.body()).get("error").asText());
+            }
+        }
+    }
+
+    @Test
+    void influxFailureIs502() throws Exception {
+        historyDown = true;
+
+        assertEquals(502, get("/api/history?series=cwu_temp&range=7d").statusCode());
+    }
+
+    private static final String[] BROWSER_HEADERS = {"Content-Type", "application/json", "X-Requested-With", "home-pump"};
+
+    /** A POST as the web UI sends it; extra headers come after the defaults. */
+    private HttpResponse<String> post(String path, String body, String... headers) throws Exception {
+        var all = new ArrayList<>(List.of(BROWSER_HEADERS));
+        all.addAll(List.of(headers));
+        return rawPost(path, body, all.toArray(String[]::new));
+    }
+
+    private HttpResponse<String> rawPost(String path, String body, String... headers) throws Exception {
+        HttpRequest.Builder request = HttpRequest.newBuilder(URI.create("http://localhost:" + server.port() + path))
+                .POST(HttpRequest.BodyPublishers.ofString(body));
+        if (headers.length > 0) {
+            request.headers(headers);
+        }
+        return client.send(request.build(), HttpResponse.BodyHandlers.ofString());
+    }
+
+    private static final String BOOST = "{\"setpoint\":\"cwu_economy\",\"value\":45,\"hours\":2}";
+
+    @Test
+    void setpointsMatchExample() throws Exception {
+        assertMatchesExample("/api/setpoints", "setpoints");
+    }
+
+    @Test
+    void appliedBoostMatchesExampleAndRestoresAfterTwoHours() throws Exception {
+        HttpResponse<String> response = post("/api/setpoints", BOOST);
+
+        assertEquals(200, response.statusCode());
+        assertEquals(example("setpoints-applied"), JSON.readTree(response.body()));
+        assertEquals(List.of(new Command("cwu_economy", 45, java.time.Duration.ofHours(2), "phone")), sent);
+    }
+
+    @Test
+    void restoreMatchesExampleAndAsksForTheUsersSetpoint() throws Exception {
+        HttpResponse<String> response = post("/api/setpoints/cwu_economy/restore", "{}", "Remote-User", "anna");
+
+        assertEquals(200, response.statusCode());
+        assertEquals(example("setpoint-restored"), JSON.readTree(response.body()));
+        assertEquals(List.of("cwu_economy by anna"), restored);
+    }
+
+    @Test
+    void restoreStatusFollowsTheGatewaysVerdict() throws Exception {
+        var expected = Map.of(Outcome.NOT_PENDING, 404, Outcome.CONFLICT, 409, Outcome.TOO_SOON, 429,
+                Outcome.FAILED, 502);
+        for (var entry : expected.entrySet()) {
+            restoreOutcome = entry.getKey();
+
+            assertEquals(entry.getValue(), post("/api/setpoints/cwu_economy/restore", "{}").statusCode());
+        }
+    }
+
+    @Test
+    void restoreWithTheGatewayDownIs503() throws Exception {
+        commandsDown = true;
+
+        assertEquals(503, post("/api/setpoints/cwu_economy/restore", "{}").statusCode());
+    }
+
+    @Test
+    void restoreIsGuardedLikeEveryWrite() throws Exception {
+        String path = "/api/setpoints/cwu_economy/restore";
+        assertEquals(415, rawPost(path, "{}", "X-Requested-With", "home-pump").statusCode());
+        assertEquals(403, rawPost(path, "{}", "Content-Type", "application/json").statusCode());
+        assertEquals(403, post(path, "{}", "Origin", "https://evil.example").statusCode());
+        assertEquals(405, get(path).statusCode());
+        assertTrue(restored.isEmpty());
+    }
+
+    @Test
+    void otherPathsUnderSetpointsAre404() throws Exception {
+        for (String path : List.of("/api/setpoints/", "/api/setpoints/cwu_economy",
+                "/api/setpoints/cwu_economy/restore/x", "/api/setpoints/CWU/restore", "/api/setpoints/a-b/restore")) {
+            assertEquals(404, post(path, "{}").statusCode(), path);
+        }
+        assertTrue(restored.isEmpty());
+    }
+
+    @Test
+    void rejectedIs422AndMatchesExample() throws Exception {
+        verdict = Status.REJECTED;
+
+        HttpResponse<String> response = post("/api/setpoints", BOOST);
+
+        assertEquals(422, response.statusCode());
+        assertEquals(example("setpoints-rejected"), JSON.readTree(response.body()));
+    }
+
+    @Test
+    void failedWriteIs502() throws Exception {
+        verdict = Status.FAILED;
+
+        assertEquals(502, post("/api/setpoints", BOOST).statusCode());
+    }
+
+    @Test
+    void forwardedUserIsPassedOnAndOddNamesFallBack() throws Exception {
+        post("/api/setpoints", BOOST, "Remote-User", "anna.k@example.pl");
+        post("/api/setpoints", BOOST, "Remote-User", "anna smith");
+        post("/api/setpoints", BOOST);
+
+        assertEquals(List.of("anna.k@example.pl", "phone", "phone"), sent.stream().map(Command::requestedBy).toList());
+    }
+
+    @Test
+    void badSetpointRequestsAre400AndSendNothing() throws Exception {
+        for (String body : List.of("", "not json", "[]", "{}", "{\"setpoint\":\"cwu_economy\"}",
+                "{\"setpoint\":\"cwu_economy\",\"value\":45.5}",
+                "{\"setpoint\":\"cwu_economy\",\"value\":\"45\"}",
+                "{\"setpoint\":\"cwu_economy\",\"value\":45,\"hours\":0}",
+                "{\"setpoint\":\"cwu_economy\",\"value\":45,\"hours\":-1}",
+                "{\"setpoint\":\"cwu_economy\",\"value\":45,\"hours\":72.5}",
+                "{\"setpoint\":\"cwu_economy\",\"value\":45,\"minutes\":5}")) {
+            assertEquals(400, post("/api/setpoints", body).statusCode(), body);
+        }
+        assertTrue(sent.isEmpty());
+    }
+
+    @Test
+    void presetResultsMatchExample() throws Exception {
+        HttpResponse<String> response = post("/api/presets/away", awayRequest());
+
+        assertEquals(200, response.statusCode());
+        JsonNode body = JSON.readTree(response.body());
+        assertEquals(example("setpoints-preset-applied").get("results").size(), body.get("results").size());
+        assertEquals("APPLIED", body.get("status").asText());
+        assertEquals(List.of("cwu_comfort", "co_comfort"), sent.stream().map(Command::setpoint).toList());
+    }
+
+    @Test
+    void presetCutShortByALostLinkKeepsTheResultsSoFar() throws Exception {
+        answersBeforeDrop = 1;
+
+        HttpResponse<String> response = post("/api/presets/away", awayRequest());
+
+        assertEquals(502, response.statusCode());
+        assertEquals(example("setpoints-preset-partial"), JSON.readTree(response.body()));
+    }
+
+    @Test
+    void awayPresetSendsTheChosenEndHeldInEachChange() throws Exception {
+        post("/api/presets/away", awayRequest());
+
+        var end = java.time.Instant.parse("2026-11-02T17:00:00Z");
+        assertEquals(List.of(new Command("cwu_comfort", 10, null, end, "phone"),
+                new Command("co_comfort", 15, null, end, "phone")), sent);
+    }
+
+    @Test
+    void awayWithOwnValuesSendsThem() throws Exception {
+        var response = post("/api/presets/away", example("preset-away-values-request").toString());
+
+        assertEquals(200, response.statusCode());
+        var end = java.time.Instant.parse("2026-11-02T17:00:00Z");
+        assertEquals(List.of(new Command("cwu_comfort", 12, null, end, "phone"),
+                new Command("co_comfort", 16, null, end, "phone")), sent);
+    }
+
+    @Test
+    void ownValuesForOtherSetpointsOrOutsideTheLimitsAre400AndSendNothing() throws Exception {
+        String until = "\"until\":\"2026-11-02T18:00:00Z\"";
+        for (String values : List.of("{\"cwu_economy\":6}", "{\"co_comfort\":4}", "{\"co_comfort\":26}",
+                "{\"co_comfort\":null}", "{\"co_comfort\":15.5}", "{\"co_comfort\":\"15\"}", "[]")) {
+            assertEquals(400, post("/api/presets/away", "{" + until + ",\"values\":" + values + "}").statusCode(),
+                    values);
+        }
+        assertTrue(sent.isEmpty());
+    }
+
+    @Test
+    void ownValueThatDoesNotLowerAHeldSetpointIs422() throws Exception {
+        var body = "{\"until\":\"2026-11-02T18:00:00Z\",\"values\":{\"co_comfort\":19}}";
+
+        assertEquals(422, post("/api/presets/away", body).statusCode());
+        assertTrue(sent.isEmpty());
+    }
+
+    @Test
+    void badOrMissingEndTimesAre400AndSendNothing() throws Exception {
+        for (String body : List.of("", "{}", "{\"until\":null}", "{\"until\":\"tomorrow\"}", "{\"until\":5}",
+                "{\"until\":\"2026-11-02T18:00:00\"}", "not json", "{\"until\":\"2026-11-02T18:00:00Z\",\"x\":1}")) {
+            assertEquals(400, post("/api/presets/away", body).statusCode(), body);
+        }
+        assertEquals(400, post("/api/presets/cwu-now", awayRequest()).statusCode());
+        assertTrue(sent.isEmpty());
+    }
+
+    @Test
+    void presetWithoutAnEndStillTakesNoBodyOrAnEmptyObject() throws Exception {
+        assertEquals(200, post("/api/presets/cwu-now", "").statusCode());
+        assertEquals(200, post("/api/presets/cwu-now", "{}").statusCode());
+    }
+
+    @Test
+    void unknownPresetIs404() throws Exception {
+        assertEquals(404, post("/api/presets/nope", "").statusCode());
+        assertTrue(sent.isEmpty());
+    }
+
+    @Test
+    void presetOutsideLimitsIs422() throws Exception {
+        verdict = Status.REJECTED;
+
+        assertEquals(422, post("/api/presets/away", awayRequest()).statusCode());
+    }
+
+    @Test
+    void unreachableGatewayOnSetpointsIs503() throws Exception {
+        commandsDown = true;
+
+        assertEquals(503, get("/api/setpoints").statusCode());
+        assertEquals(503, post("/api/setpoints", BOOST).statusCode());
+        assertEquals(503, post("/api/presets/away", awayRequest()).statusCode());
+    }
+
+    @Test
+    void writesWithoutJsonContentTypeAre415() throws Exception {
+        for (String path : List.of("/api/setpoints", "/api/presets/away")) {
+            assertEquals(415, rawPost(path, BOOST, "X-Requested-With", "home-pump").statusCode(), path);
+            assertEquals(415, rawPost(path, BOOST, "X-Requested-With", "home-pump", "Content-Type", "text/plain")
+                    .statusCode(), path);
+        }
+        assertTrue(sent.isEmpty());
+    }
+
+    @Test
+    void jsonContentTypeMayCarryACharset() throws Exception {
+        assertEquals(200, rawPost("/api/setpoints", BOOST, "X-Requested-With", "home-pump",
+                "Content-Type", "application/json; charset=utf-8").statusCode());
+    }
+
+    @Test
+    void writesWithoutTheCustomHeaderAre403() throws Exception {
+        for (String path : List.of("/api/setpoints", "/api/presets/away")) {
+            assertEquals(403, rawPost(path, BOOST, "Content-Type", "application/json").statusCode(), path);
+            assertEquals(403, rawPost(path, BOOST, "Content-Type", "application/json",
+                    "X-Requested-With", "XMLHttpRequest").statusCode(), path);
+        }
+        assertTrue(sent.isEmpty());
+    }
+
+    @Test
+    void writesFromAnotherOriginAre403() throws Exception {
+        for (String path : List.of("/api/setpoints", "/api/presets/away")) {
+            for (String origin : List.of("https://evil.example", "null", "http://localhost:1")) {
+                assertEquals(403, post(path, BOOST, "Origin", origin).statusCode(), origin);
+            }
+        }
+        assertTrue(sent.isEmpty());
+    }
+
+    @Test
+    void writesFromTheSameOriginAreAccepted() throws Exception {
+        assertEquals(200, post("/api/setpoints", BOOST, "Origin", "http://localhost:" + server.port()).statusCode());
+    }
+
+    @Test
+    void setpointMethodsAreChecked() throws Exception {
+        assertEquals(405, post("/api/history", "").statusCode());
+        assertEquals(405, get("/api/presets/away").statusCode());
+        HttpRequest put = HttpRequest.newBuilder(URI.create("http://localhost:" + server.port() + "/api/setpoints"))
+                .PUT(HttpRequest.BodyPublishers.noBody()).build();
+        assertEquals(405, client.send(put, HttpResponse.BodyHandlers.ofString()).statusCode());
+    }
+
+    @Test
+    void apiAcceptsOnlyGet() throws Exception {
+        HttpRequest post = HttpRequest.newBuilder(URI.create("http://localhost:" + server.port() + "/api/health"))
+                .POST(HttpRequest.BodyPublishers.noBody()).build();
+
+        assertEquals(405, client.send(post, HttpResponse.BodyHandlers.ofString()).statusCode());
+    }
+
+    @Test
+    void everyResponseCarriesTheSecurityHeaders() throws Exception {
+        var paths = List.of("/", "/index.html", "/missing.css", "/api/health", "/api/nothing", "/api/history");
+        for (String path : paths) {
+            assertSecurityHeaders(get(path), path);
+        }
+        assertSecurityHeaders(post("/api/health", ""), "405");
+        assertSecurityHeaders(post("/api/setpoints", "{"), "400");
+        assertSecurityHeaders(rawPost("/api/setpoints", BOOST), "403");
+    }
+
+    private static void assertSecurityHeaders(HttpResponse<String> response, String what) {
+        var headers = response.headers();
+        assertEquals("default-src 'none'; script-src 'self'; style-src 'self'; img-src 'self' data:; "
+                + "font-src 'self'; connect-src 'self'; base-uri 'none'; form-action 'self'; frame-ancestors 'none'",
+                headers.firstValue("Content-Security-Policy").orElse(null), what);
+        assertEquals("nosniff", headers.firstValue("X-Content-Type-Options").orElse(null), what);
+        assertEquals("no-referrer", headers.firstValue("Referrer-Policy").orElse(null), what);
+    }
+
+    @Test
+    void unknownApiPathIs404() throws Exception {
+        assertEquals(404, get("/api/nothing").statusCode());
+    }
+
+    @Test
+    void apiRoutesMatchTheExactPathOnly() throws Exception {
+        for (String path : List.of("/api/heat-pumpX", "/api/heat-pump/", "/api/heat-pump/x", "/api/energy2",
+                "/api/healthz", "/api/history2?series=cwu_temp", "/api/setpointsX")) {
+            assertEquals(404, get(path).statusCode(), path);
+        }
+        assertEquals(404, post("/api/setpointsX", BOOST).statusCode());
+        assertEquals(200, get("/api/heat-pump?x=1").statusCode());
+    }
+
+    @Test
+    void stopClosesThePort() {
+        server.stop();
+
+        assertThrows(IOException.class, () -> get("/api/health"));
+    }
+
+    @Test
+    void requestBodiesOver4KbAre413AndSendNothing() throws Exception {
+        String padding = " ".repeat(4096 - BOOST.length());
+        assertEquals(200, post("/api/setpoints", BOOST + padding).statusCode());
+        sent.clear();
+
+        assertEquals(413, post("/api/setpoints", BOOST + padding + " ").statusCode());
+        assertEquals(413, post("/api/presets/away", "x".repeat(5000)).statusCode());
+        assertEquals(0, sent.size());
+    }
+
+    @Test
+    void answersOnlyTheApi() throws Exception {
+        // The web UI is the frontend container's (ADR-010); the backend serves no files.
+        for (String path : List.of("/", "/index.html", "/assets/index.js", "/api", "/api/")) {
+            assertEquals(404, get(path).statusCode(), path);
+        }
+    }
+
+    /** The JDK client normalises dot segments, so send the request line as is. */
+    private int rawGet(String path) throws IOException {
+        try (Socket socket = new Socket("localhost", server.port())) {
+            socket.getOutputStream().write(("GET " + path + " HTTP/1.1\r\nHost: localhost\r\n"
+                    + "Connection: close\r\n\r\n").getBytes(StandardCharsets.US_ASCII));
+            String statusLine = new String(socket.getInputStream().readAllBytes(), StandardCharsets.US_ASCII)
+                    .lines().findFirst().orElseThrow();
+            return Integer.parseInt(statusLine.split(" ")[1]);
+        }
+    }
+}

backend/src/test/java/home/backend/adapters/influx/InfluxAuditRepositoryTest.java

@@ -0,0 +1,105 @@
+package home.backend.adapters.influx;
+
+import com.sun.net.httpserver.HttpServer;
+import home.backend.application.AuditRepository.Row;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.URI;
+import java.net.URLDecoder;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class InfluxAuditRepositoryTest {
+
+    private static final Instant FROM = Instant.parse("2026-10-17T12:00:00Z");
+    private static final Instant TO = Instant.parse("2026-10-24T12:00:00Z");
+
+    private HttpServer server;
+    private final List<String> queries = Collections.synchronizedList(new ArrayList<>());
+    private String body;
+
+    @BeforeEach
+    void startServer() throws IOException {
+        server = HttpServer.create(new InetSocketAddress(InetAddress.getLoopbackAddress(), 0), 0);
+        server.createContext("/query", exchange -> {
+            queries.add(URLDecoder.decode(exchange.getRequestURI().getRawQuery(), StandardCharsets.UTF_8));
+            byte[] bytes = body.getBytes(StandardCharsets.UTF_8);
+            exchange.sendResponseHeaders(200, bytes.length);
+            exchange.getResponseBody().write(bytes);
+            exchange.close();
+        });
+        server.start();
+    }
+
+    @AfterEach
+    void stopServer() {
+        server.stop(0);
+    }
+
+    @Test
+    void readsHeatPumpRowsFromTheLegacyDatabase() throws IOException {
+        body = fixture("influx-audit-setpoints.json");
+
+        List<Row> rows = repository().heatPump(FROM, TO);
+
+        assertEquals(2, rows.size());
+        assertEquals(new Row(Instant.ofEpochMilli(1761292800000L), "cwu_economy", "restore", "APPLIED", 45.0, 8.0),
+                rows.get(0));
+        assertNull(rows.get(1).oldValue());
+        assertEquals("co_comfort", rows.get(1).target());
+        assertTrue(queries.getFirst().startsWith("db=Dom_Pompa&epoch=ms&q=SELECT * FROM \"setpoint_audit\" "
+                + "WHERE time >= " + FROM.toEpochMilli() + "ms AND time < " + TO.toEpochMilli() + "ms"),
+                queries.getFirst());
+    }
+
+    @Test
+    void readsBatteryRowsByRegisterTag() throws IOException {
+        body = fixture("influx-audit-battery.json");
+
+        List<Row> rows = repository().battery(FROM, TO);
+
+        assertEquals(List.of("reserve", "174"), rows.stream().map(Row::target).toList());
+        assertEquals(60.0, rows.getFirst().newValue());
+        assertTrue(queries.getFirst().startsWith("db=electricity&"), queries.getFirst());
+        assertTrue(queries.getFirst().contains("\"deye_settings_audit\""), queries.getFirst());
+    }
+
+    @Test
+    void noRowsIsAnEmptyList() throws IOException {
+        body = fixture("influx-query-empty.json");
+
+        assertTrue(repository().battery(FROM, TO).isEmpty());
+    }
+
+    @Test
+    void anInfluxErrorIsAnIOException() throws IOException {
+        body = fixture("influx-query-error.json");
+
+        assertThrows(IOException.class, () -> repository().heatPump(FROM, TO));
+    }
+
+    private InfluxAuditRepository repository() {
+        URI base = URI.create("http://127.0.0.1:" + server.getAddress().getPort());
+        return new InfluxAuditRepository(new InfluxSettings(base, Duration.ofSeconds(5)));
+    }
+
+    private static String fixture(String name) throws IOException {
+        return Files.readString(Path.of("src/test/resources/influx", name));
+    }
+}

backend/src/test/java/home/backend/adapters/influx/InfluxHistoryRepositoryTest.java

@@ -0,0 +1,274 @@
+package home.backend.adapters.influx;
+
+import com.sun.net.httpserver.HttpServer;
+import home.backend.domain.HeatPumpSample;
+import home.backend.domain.HistoryView.Point;
+import home.backend.domain.Series;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.URI;
+import java.net.URLDecoder;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class InfluxHistoryRepositoryTest {
+
+    private static final Instant FROM = Instant.parse("2026-10-24T00:00:00Z");
+    private static final Instant TO = Instant.parse("2026-10-24T06:00:00Z");
+    private static final Duration TIMEOUT = Duration.ofSeconds(5);
+
+    private HttpServer server;
+    private final List<Map<String, String>> requests = Collections.synchronizedList(new ArrayList<>());
+    private volatile CountDownLatch rendezvous = new CountDownLatch(0);
+    private final AtomicInteger metTogether = new AtomicInteger();
+    private final Map<String, String> bodyByField = new HashMap<>();
+    private int status = 200;
+    private String failingField = "";
+    private String defaultBody = "{\"results\":[{\"statement_id\":0}]}";
+
+    @BeforeEach
+    void startServer() throws IOException {
+        server = HttpServer.create(new InetSocketAddress(InetAddress.getLoopbackAddress(), 0), 0);
+        // Concurrent handlers: the repository asks for the parts of a series at the same time.
+        server.setExecutor(Executors.newCachedThreadPool());
+        server.createContext("/query", exchange -> {
+            Map<String, String> params = params(exchange.getRequestURI().getRawQuery());
+            requests.add(params);
+            rendezvous.countDown();
+            try {
+                if (rendezvous.await(5, TimeUnit.SECONDS)) {
+                    metTogether.incrementAndGet();
+                }
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+            }
+            String body = bodyByField.entrySet().stream()
+                    .filter(e -> params.get("q").contains("\"" + e.getKey() + "\""))
+                    .map(Map.Entry::getValue).findFirst().orElse(defaultBody);
+            byte[] bytes = body.getBytes(StandardCharsets.UTF_8);
+            boolean fails = !failingField.isEmpty() && params.get("q").contains("\"" + failingField + "\"");
+            exchange.sendResponseHeaders(fails ? 500 : status, bytes.length);
+            exchange.getResponseBody().write(bytes);
+            exchange.close();
+        });
+        server.start();
+    }
+
+    @AfterEach
+    void stopServer() {
+        server.stop(0);
+    }
+
+    @Test
+    void asksTheLegacyDatabaseForATemperatureWithQuotedFieldName() throws IOException {
+        defaultBody = fixture("influx-query-cwu-6h.json");
+
+        List<Point> points = repository(TIMEOUT).history(Series.CWU_TEMP, FROM, TO, 360);
+
+        assertEquals(1, requests.size());
+        assertEquals("Dom_Pompa", requests.get(0).get("db"));
+        assertEquals("ms", requests.get(0).get("epoch"));
+        assertEquals("SELECT mean(\"Temp cwu\") FROM \"POMPA\" WHERE time >= 1792800000000ms"
+                + " AND time < 1792821600000ms GROUP BY time(1m) fill(none)", requests.get(0).get("q"));
+        assertEquals(7, points.size());
+        assertEquals(new Point(Instant.ofEpochMilli(1792771200000L), 43.76666666666667), points.get(0));
+    }
+
+    @Test
+    void asksTheElectricityDatabaseForGridPower() throws IOException {
+        repository(TIMEOUT).history(Series.GRID_POWER, FROM, TO, 72);
+
+        assertEquals("electricity", requests.get(0).get("db"));
+        assertEquals("SELECT mean(\"total_power_active\") FROM \"PRAD2\" WHERE time >= 1792800000000ms"
+                + " AND time < 1792821600000ms GROUP BY time(5m) fill(none)", requests.get(0).get("q"));
+    }
+
+    @Test
+    void roundsTheStepUpToWholeMinutes() throws IOException {
+        repository(TIMEOUT).history(Series.LOAD_POWER, FROM, TO, 100);
+
+        assertTrue(requests.get(0).get("q").contains("GROUP BY time(4m)"), requests.get(0).get("q"));
+    }
+
+    @Test
+    void sumsPvPowerAcrossMeasurementsAndKeepsBucketsWithOnePart() throws IOException {
+        bodyByField.put("pv1_power_w", series(1000, 100.0, 2000, 200.0));
+        bodyByField.put("pv2_power_w", series(1000, 50.0));
+        bodyByField.put("pv_power_w", series(2000, 5.0, 3000, 7.0));
+
+        List<Point> points = repository(TIMEOUT).history(Series.PV_POWER, FROM, TO, 72);
+
+        assertEquals(3, requests.size());
+        assertEquals(List.of(
+                new Point(Instant.ofEpochMilli(1000), 150.0),
+                new Point(Instant.ofEpochMilli(2000), 205.0),
+                new Point(Instant.ofEpochMilli(3000), 7.0)), points);
+    }
+
+    @Test
+    void asksForTheThreePvPartsAtTheSameTime() throws IOException {
+        rendezvous = new CountDownLatch(3);
+
+        repository(TIMEOUT).history(Series.PV_POWER, FROM, TO, 72);
+
+        // A handler passes the latch only when all three requests are in flight together.
+        assertEquals(3, metTogether.get());
+    }
+
+    @Test
+    void oneFailingPartFailsTheWholeSeries() {
+        failingField = "pv2_power_w";
+
+        assertThrows(IOException.class, () -> repository(TIMEOUT).history(Series.PV_POWER, FROM, TO, 72));
+    }
+
+    @Test
+    void sortsPointsByTime() throws IOException {
+        defaultBody = series(3000, 3.0, 1000, 1.0, 2000, 2.0);
+
+        List<Point> points = repository(TIMEOUT).history(Series.BATTERY_SOC, FROM, TO, 72);
+
+        assertEquals(List.of(1000L, 2000L, 3000L), points.stream().map(p -> p.t().toEpochMilli()).toList());
+    }
+
+    @Test
+    void noDataGivesAnEmptyList() throws IOException {
+        defaultBody = fixture("influx-query-empty.json");
+
+        assertEquals(List.of(), repository(TIMEOUT).history(Series.PV_POWER, FROM, TO, 72));
+    }
+
+    @Test
+    void topLevelErrorIsAnIOException() throws IOException {
+        defaultBody = fixture("influx-query-error.json");
+
+        IOException e = assertThrows(IOException.class,
+                () -> repository(TIMEOUT).history(Series.CWU_TEMP, FROM, TO, 72));
+        assertTrue(e.getMessage().contains("error parsing query"), e.getMessage());
+    }
+
+    @Test
+    void perResultErrorIsAnIOException() {
+        defaultBody = "{\"results\":[{\"statement_id\":0,\"error\":\"database not found: electricity\"}]}";
+
+        IOException e = assertThrows(IOException.class,
+                () -> repository(TIMEOUT).history(Series.GRID_POWER, FROM, TO, 72));
+        assertTrue(e.getMessage().contains("database not found"), e.getMessage());
+    }
+
+    @Test
+    void httpErrorIsAnIOException() {
+        status = 503;
+
+        IOException e = assertThrows(IOException.class,
+                () -> repository(TIMEOUT).history(Series.CWU_TEMP, FROM, TO, 72));
+        assertTrue(e.getMessage().contains("503"), e.getMessage());
+    }
+
+    @Test
+    void badJsonIsAnIOException() {
+        defaultBody = "<html>not json";
+
+        assertThrows(IOException.class, () -> repository(TIMEOUT).history(Series.CWU_TEMP, FROM, TO, 72));
+    }
+
+    @Test
+    void slowServerTimesOut() {
+        server.removeContext("/query");
+        server.createContext("/query", exchange -> {
+            try {
+                Thread.sleep(1000);
+            } catch (InterruptedException ignored) {
+                Thread.currentThread().interrupt();
+            }
+            exchange.close();
+        });
+
+        assertThrows(IOException.class,
+                () -> repository(Duration.ofMillis(200)).history(Series.CWU_TEMP, FROM, TO, 72));
+    }
+
+    @Test
+    void readsRawHeatPumpPollsFromTheLegacyDatabase() throws IOException {
+        defaultBody = fixture("influx-query-heat-pump.json");
+
+        List<HeatPumpSample> samples = repository(TIMEOUT).samples(FROM, TO);
+
+        assertEquals("Dom_Pompa", requests.get(0).get("db"));
+        assertEquals("SELECT output_compressor, output_cwu, output_co, output_heater, outdoor_temp, cwu_temp"
+                + " FROM \"heat_pump\" WHERE time >= 1792800000000ms AND time < 1792821600000ms",
+                requests.get(0).get("q"));
+        assertEquals(3, samples.size());
+        assertEquals(new HeatPumpSample(Instant.ofEpochMilli(1792771500000L), 100.0, 100.0, 0.0, 0.0, 8.5, 43.9),
+                samples.get(1));
+        assertEquals(new HeatPumpSample(Instant.ofEpochMilli(1792771800000L), 50.0, 0.0, 100.0, 100.0, null, null),
+                samples.get(2));
+    }
+
+    @Test
+    void noHeatPumpPollsIsAnEmptyList() throws IOException {
+        assertTrue(repository(TIMEOUT).samples(FROM, TO).isEmpty());
+    }
+
+    @Test
+    void heatPumpQueryErrorIsAnIoException() throws IOException {
+        defaultBody = fixture("influx-query-error.json");
+
+        assertThrows(IOException.class, () -> repository(TIMEOUT).samples(FROM, TO));
+    }
+
+    @Test
+    void rejectsAnEmptyRange() {
+        assertThrows(IllegalArgumentException.class,
+                () -> repository(TIMEOUT).history(Series.CWU_TEMP, FROM, FROM, 72));
+    }
+
+    private InfluxHistoryRepository repository(Duration timeout) {
+        URI base = URI.create("http://127.0.0.1:" + server.getAddress().getPort());
+        return new InfluxHistoryRepository(new InfluxSettings(base, timeout));
+    }
+
+    private static String series(Object... timeAndValue) {
+        StringBuilder rows = new StringBuilder();
+        for (int i = 0; i < timeAndValue.length; i += 2) {
+            rows.append(i == 0 ? "" : ",").append('[').append(timeAndValue[i]).append(',')
+                    .append(timeAndValue[i + 1]).append(']');
+        }
+        return "{\"results\":[{\"statement_id\":0,\"series\":[{\"name\":\"m\",\"columns\":[\"time\",\"mean\"],"
+                + "\"values\":[" + rows + "]}]}]}";
+    }
+
+    private static String fixture(String name) throws IOException {
+        return Files.readString(Path.of("src/test/resources/influx", name));
+    }
+
+    private static Map<String, String> params(String rawQuery) {
+        Map<String, String> params = new HashMap<>();
+        for (String pair : rawQuery.split("&")) {
+            String[] kv = pair.split("=", 2);
+            params.put(kv[0], URLDecoder.decode(kv[1], StandardCharsets.UTF_8));
+        }
+        return params;
+    }
+}

backend/src/test/java/home/backend/adapters/influx/InfluxPvEnergyTest.java

@@ -0,0 +1,89 @@
+package home.backend.adapters.influx;
+
+import com.sun.net.httpserver.HttpServer;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.URI;
+import java.net.URLDecoder;
+import java.nio.charset.StandardCharsets;
+import java.time.Duration;
+import java.time.LocalDate;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class InfluxPvEnergyTest {
+
+    private static final LocalDate FROM = LocalDate.parse("2026-10-19");
+    private static final LocalDate TO = LocalDate.parse("2026-10-24");
+
+    private HttpServer server;
+    private InfluxPvEnergy pv;
+    private final List<String> queries = new ArrayList<>();
+    private int status = 200;
+    /** Day buckets start at Warsaw midnight: 2026-10-19 is 2026-10-18T22:00Z. */
+    private String deye = rows("1792360800000", 22.5, "1792447200000", 8.0);
+    private String fronius = rows("1792360800000", 4400.0, "1792533600000", 100.0);
+
+    @BeforeEach
+    void start() throws IOException {
+        server = HttpServer.create(new InetSocketAddress(InetAddress.getLoopbackAddress(), 0), 0);
+        server.createContext("/query", exchange -> {
+            String query = URLDecoder.decode(exchange.getRequestURI().getRawQuery(), StandardCharsets.UTF_8);
+            queries.add(query);
+            byte[] bytes = (query.contains("\"deye\"") ? deye : fronius).getBytes(StandardCharsets.UTF_8);
+            exchange.sendResponseHeaders(status, bytes.length);
+            exchange.getResponseBody().write(bytes);
+            exchange.close();
+        });
+        server.start();
+        var settings = new InfluxSettings(URI.create("http://127.0.0.1:" + server.getAddress().getPort()),
+                Duration.ofSeconds(2));
+        pv = new InfluxPvEnergy(settings);
+    }
+
+    @AfterEach
+    void stop() {
+        server.stop(0);
+    }
+
+    private static String rows(String t1, double v1, String t2, double v2) {
+        return "{\"results\":[{\"statement_id\":0,\"series\":[{\"name\":\"m\",\"columns\":[\"time\",\"max\"],"
+                + "\"values\":[[" + t1 + "," + v1 + "],[" + t2 + "," + v2 + "]]}]}]}";
+    }
+
+    @Test
+    void addsTheDeyeAndFroniusDayCountersPerLocalDay() throws IOException {
+        Map<LocalDate, Double> days = pv.dailyKwh(FROM, TO);
+
+        assertEquals(Map.of(FROM, 22.5 + 4.4), days);
+    }
+
+    @Test
+    void asksForTheDailyMaximumOfEachCounterInWarsawDays() throws IOException {
+        pv.dailyKwh(FROM, TO);
+
+        assertEquals(2, queries.size());
+        String deyeQuery = queries.stream().filter(q -> q.contains("\"deye\"")).findFirst().orElseThrow();
+        assertTrue(deyeQuery.contains("db=electricity"), deyeQuery);
+        assertTrue(deyeQuery.contains("SELECT max(\"pv_today_kwh\") FROM \"deye\" WHERE time >= 1792360800000ms"
+                + " AND time < 1792792800000ms GROUP BY time(1d) fill(none) tz('Europe/Warsaw')"), deyeQuery);
+        assertTrue(queries.stream().anyMatch(q -> q.contains("max(\"energy_day_wh\") FROM \"fronius\"")), queries.toString());
+    }
+
+    @Test
+    void failureIsAnIoError() {
+        status = 500;
+
+        assertThrows(IOException.class, () -> pv.dailyKwh(FROM, TO));
+    }
+}