# Gateway Architecture (target state)

Last updated: 2025-12-09

## Overview
- A single long-lived **Gateway** process owns all messaging surfaces (WhatsApp via Baileys, Telegram when enabled) and the control/event plane.
- All clients (macOS app, CLI, web UI, automations) connect to the Gateway over one transport: **WebSocket on 127.0.0.1:18789** (tunnel or VPN for remote).
- One Gateway per host; it is the only place that is allowed to open a WhatsApp session. All sends/agent runs go through it.

## Components and flows
- **Gateway (daemon)**  
  - Maintains Baileys/Telegram connections.  
  - Exposes a typed WS API (req/resp + server push events).  
  - Validates every inbound frame against JSON Schema; rejects anything before a mandatory `hello`.
- **Clients (mac app / CLI / web admin)**  
  - One WS connection per client.  
  - Send requests (`health`, `status`, `send`, `agent`, `system-presence`, toggles) and subscribe to events (`tick`, `agent`, `presence`, `shutdown`).
- **Agent runner (Tau/Pi process)**  
  - Spawned by the Gateway on demand for `agent` calls; streams events back over the same WS connection.
- **WebChat**  
  - Serves static assets locally.  
  - Holds a single WS connection to the Gateway for control/data; all sends/agent runs go through the Gateway WS.  
  - Remote use goes through the same SSH/Tailscale tunnel as other clients.

## Connection lifecycle (single client)
```
Client                    Gateway
  |                          |
  |------- hello ----------->|
  |<------ hello-ok ---------|   (or hello-error + close)
  |   (hello-ok carries snapshot: presence + health) 
  |                          |
  |<------ event:presence ---|   (deltas)
  |<------ event:tick -------|   (keepalive/no-op)
  |                          |
  |------- req:agent ------->|
  |<------ res:agent --------|   (ack: {runId,status:"accepted"})
  |<------ event:agent ------|   (streaming)
  |<------ res:agent --------|   (final: {runId,status,summary})
  |                          |
```
## Wire protocol (summary)
- Transport: WebSocket, text frames with JSON payloads.
- First frame must be `hello {type:"hello", minProtocol, maxProtocol, client:{name,version,platform,mode,instanceId}, caps, auth?, locale?, userAgent? }`.
- Server replies `hello-ok {type:"hello-ok", protocol:<chosen>, server:{version,commit,host,connId}, features:{methods,events}, snapshot:{presence:[...], health:{...}, stateVersion:{presence,health}, uptimeMs}, policy:{maxPayload,maxBufferedBytes,tickIntervalMs} }`
  or `hello-error {type:"hello-error", reason, expectedProtocol, minClient }` then closes.
- After handshake:  
  - Requests: `{type:"req", id, method, params}` → `{type:"res", id, ok, payload|error}`  
  - Events: `{type:"event", event:"agent"|"presence"|"tick"|"shutdown", payload, seq?, stateVersion?}`
- If `CLAWDIS_GATEWAY_TOKEN` (or `--token`) is set, `hello.auth.token` must match; otherwise the socket closes with policy violation.
- Presence payload is structured, not free text: `{host, ip, version, mode, lastInputSeconds?, ts, reason?, tags?[], instanceId? }`.
- Agent runs are acked `{runId,status:"accepted"}` then complete with a final res `{runId,status,summary}`; streamed output arrives as `event:"agent"`.
- Protocol versions are bumped on breaking changes; clients must match `minClient`; Gateway chooses within client’s min/max.
- Idempotency keys are required for side-effecting methods (`send`, `agent`) to safely retry; server keeps a short-lived dedupe cache.
- Policy in `hello-ok` communicates payload/queue limits and tick interval.

## Type system and codegen
- Source of truth: TypeBox (or ArkType) definitions in `protocol/` on the server.
- Build step emits JSON Schema.  
- Clients:
  - TypeScript: uses the same TypeBox types directly.
  - Swift: generated `Codable` models via quicktype from the JSON Schema.
- Validation: AJV on the server for every inbound frame; optional client-side validation for defensive programming.

## Invariants
- Exactly one Gateway controls a single Baileys session per host. No fallbacks to ad-hoc direct Baileys sends.
- Handshake is mandatory; any non-JSON or non-hello first frame is a hard close.
- All methods and events are versioned; new fields are additive; breaking changes increment `protocol`.
- No event replay: on seq gaps, clients must refresh (`health` + `system-presence`) and continue; presence is bounded via TTL/max entries.

## Remote access
- Preferred: Tailscale or VPN; alternate: SSH tunnel `ssh -N -L 18789:127.0.0.1:18789 user@host`.
- Same protocol over the tunnel; same handshake. If a shared token is configured, clients must send it in `hello.auth.token` even over the tunnel.

## Operations snapshot
- Start: `clawdis gateway` (foreground, logs to stdout).  
  Supervise with launchd/systemd for restarts.  
- Health: request `health` over WS; also surfaced in `hello-ok.health`.  
- Metrics/logging: keep outside this spec; gateway should expose Prometheus text or structured logs separately.

## Migration notes
- This architecture supersedes the legacy stdin RPC and the ad-hoc TCP control port. New clients should speak only the WS protocol. Legacy compatibility is intentionally dropped.