evcc-io/docs/agents/web-ui-api.md

Web UI & REST API

Server Architecture

• Router: gorilla/mux, strict slash
• Middleware: GZIP, CORS (*), ETag caching, request logging, JSON headers, JWT auth
• Timeouts: Read 5s, Write 10s, Idle 120s
• Static assets: embedded in binary (fs.FS)
• Default port: 7070

REST API (base /api/)

Site-level

• POST /buffersoc/{value}, /prioritysoc/{value}, /residualpower/{value} etc.
• GET /tariff/{tariff} — tariff rates
• GET /sessions — charging history
• GET /state — complete system state (supports jq filtering)

Per-loadpoint (/loadpoints/{id}/...)

• POST mode/{value} — off/now/minpv/pv
• POST limitsoc/{value}, limitenergy/{value} — charge limits
• POST mincurrent/{value}, maxcurrent/{value} — current limits
• POST phases/{value} — phase config
• POST priority/{value}, batteryboost/{value}
• POST plan/energy/{value}/{time} — schedule plan
• POST vehicle/{name} — select vehicle
• POST smartcostlimit/{value} — smart cost threshold

Configuration (/config/..., auth required)

• CRUD for devices (chargers, meters, vehicles, tariffs)
• Template browsing and testing
• Site, loadpoint, circuit, HEMS, messaging config
• GET /config/evcc.yaml — YAML export

System (/system/..., auth required)

• Log viewing (/log, /log/areas), cache clear, shutdown

Database (/db/..., auth + second factor required)

• Backup download, restore from file, selective reset
• Second factor: admin password in request body, or API key via Bearer token (bypasses password check)

Handler Pattern

Generic handler[T] with type conversion, setter, getter. Specialized: floatHandler, intHandler, boolHandler, durationHandler.

WebSocket (/ws)

• coder/websocket (RFC 6455)
• Pub/sub via SocketHub
• Buffered channels (1024 per subscriber)
• Welcome message with full state snapshot
• Incremental updates as JSON key-value pairs with dot-notation keys:

  {"loadpoints.1.mode": "solar", "site.gridPower": 1234}
  

• Write timeout: 10s, compression (disabled for Safari)

State Flow

1. WS connects -> receives welcome with full state
2. App emits util.Param on changes
3. Hub broadcasts to subscribers
4. Frontend store.update(msg) merges via dot-notation
5. Components reactively re-render

Authentication

• JWT, 90-day lifetime
• HttpOnly cookie (auth) with SameSite=Strict
• Also accepts Authorization: Bearer <token> header
• Modes: Disabled, Locked (demo), Configured (password)
• Protects /api/config, /api/system, and /api/db

MQTT Integration

• Publishes state changes to configurable broker
• Subscribes to control topics
• Retained messages for state persistence

Key Files

• server/http.go — router setup
• server/http_auth.go — authentication
• server/http_site_handler.go — state + request handlers
• server/http_config_*.go — config endpoints
• server/http_loadpoint_handler.go — per-loadpoint endpoints
• server/socket.go — WebSocket pub/sub
• assets/js/app.ts — Vue app entry
• assets/js/store.ts — reactive state store
• assets/js/api.ts — Axios clients
• assets/js/router.ts — route definitions