114 lines
6.6 KiB
Markdown
114 lines
6.6 KiB
Markdown
# Client architecture
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The [React browser client](../../s2s-frontend) uses the
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[FastAPI backend](../../s2s-client) for HTTP APIs and a speech WebSocket relay.
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`start_ui.sh` serves Vite on the existing public port `8420` and FastAPI on
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loopback port `8421`. Vite forwards backend routes and provides hot reload;
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Uvicorn reloads Python edits. The launcher supervises both processes.
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The speech pipeline and optional Node-RED reasoning service run separately.
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Runtime configuration comes from environment variables and the root `.env`.
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```mermaid
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flowchart LR
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Browser[Browser UI]
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Vite[Vite on public port 8420]
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Server[Client FastAPI server]
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Speech[Realtime speech backend]
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Reasoning[Node-RED or HTTP reasoning provider]
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Tools[ApiPilot backend]
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Browser <-->|Frontend and HMR| Vite
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Vite -->|HTTP configuration and proxies| Server
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Vite <-->|Speech WebSocket relay| Server
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Server <-->|Realtime events and audio| Speech
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Browser <-->|Optional direct connection| Speech
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Server -->|Optional transcript reasoning| Reasoning
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Server -->|Tool discovery and execution| Tools
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```
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## Connection modes
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`SPEECH_TO_SPEECH_URL` pins a direct browser connection. Otherwise,
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`S2S_PROXY_TARGET` exposes the same-origin `/v1/realtime` proxy. Either setting
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disables load-balancer mode. With neither set, `LOAD_BALANCER_URL` enables the
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session/queue proxy, or the user can enter a direct URL in settings. See
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[usage](usage.md) for the configuration matrix.
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The local realtime proxy relays audio and events in both directions. It also
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patches selected `session.update` instructions, handles ApiPilot marker-based
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tool execution, filters internal text, and can suppress speculative/tool-marker
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audio. It is not an unconditional byte-for-byte tunnel.
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## Source map
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| Source | Responsibility |
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| [server.py](../../s2s-client/server.py) | Compatibility entry point for existing `server:app` commands |
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| [main.py](../../s2s-client/s2s_client/main.py) | FastAPI assembly, documentation serving and redirects |
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| [api](../../s2s-client/s2s_client/api) | HTTP route registration, handlers and compatible response validation |
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| [models](../../s2s-client/s2s_client/models) | Pydantic request and response contracts |
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| [core](../../s2s-client/s2s_client/core) | Existing environment parsing, logging, URL helpers and diagnostics |
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| [providers](../../s2s-client/s2s_client/providers) | Caller context and ApiPilot HTTP integrations |
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| [services](../../s2s-client/s2s_client/services) | Context construction, reasoning and tool-context rendering |
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| [realtime](../../s2s-client/s2s_client/realtime) | WebSocket relay, events, markers and audio handling |
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| [start_ui.sh](../../start_ui.sh) | Dependency setup, ports, readiness, reload processes, and shutdown |
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| [vite.config.ts](../../s2s-frontend/vite.config.ts) | Public development endpoint, HMR, allowed hosts, and backend routing |
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| [App.tsx](../../s2s-frontend/src/App.tsx) | React layout, voice controls, dialogs, profile and reports sidebar |
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| [controller.ts](../../s2s-frontend/src/realtime/controller.ts) | Application state, settings, context, queue, tools and external reasoning |
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| [client.ts](../../s2s-frontend/src/realtime/client.ts) | Realtime protocol, session lifecycle, audio and transcript events |
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| [components](../../s2s-frontend/src/components) | Chat, caller profile, settings and voice components |
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| [audio](../../s2s-frontend/src/audio) | TypeScript capture/playback worklets, PCM codec, and visualizer |
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| [legacy-theme.css](../../s2s-frontend/src/styles/legacy-theme.css) | Retained themes and responsive visual styles alongside Tailwind |
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| [flows.json](../../s2s-reasoning-engine/flows.json) | Node-RED reasoning and assistant-response logging |
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## Server routes
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| Route | Purpose |
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|---|---|
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| `GET /api/config` | Connection settings, primary prompt, reasoning/theme/start modes, and feature flags |
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| `WS /v1/realtime` | Local realtime proxy to `S2S_PROXY_TARGET` |
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| `POST /api/reasoning` | Node-RED or OpenAI-compatible HTTP reasoning; disabled in `PROXY` mode |
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| `GET /api/user/phone` | Configured caller profile lookup |
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| `GET /api/user/reports` | Configured scheduled report lookup, subject to report-injection controls |
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| `GET /api/apipilot/tools` | Tool discovery with optional authorization and cache refresh |
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| `POST /api/apipilot/execute` | Validated tool execution returning a `success/data/error` envelope |
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| `POST /api/search` | Serper web search proxy |
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| `/api/session`, `/api/queue/*` | Load-balancer session and waiting-queue proxies |
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The public root serves the React UI. `/__vite_hmr` carries Vite hot updates;
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`/v1/realtime` remains the speech connection. `/docs` remains the FastAPI API
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explorer, while project documentation files are served in the `/docs/`
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subdirectories. Markdown remains
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source text, and directories without `index.html` are not browsable pages.
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FastAPI serves backend and documentation routes only. The frontend source and
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assets live in `s2s-frontend` and are served by Vite.
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The uv project and its Python tools are scoped to `s2s-client/`. Response models
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describe service-owned structure and retain loose upstream values. See
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[development and compatibility](development.md) before tightening a contract.
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## Audio path
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1. The browser captures microphone audio with echo cancellation, noise
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suppression and automatic gain-control settings.
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2. [mic-capture.worklet.ts](../../s2s-frontend/src/audio/mic-capture.worklet.ts) resamples to 16 kHz
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mono PCM16. The browser sends base64 `input_audio_buffer.append` frames.
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3. The backend processes VAD → STT → LLM → TTS and emits realtime events.
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4. Assistant PCM16 audio at the current 16 kHz protocol rate is decoded and sent to
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[audio-playback.worklet.ts](../../s2s-frontend/src/audio/audio-playback.worklet.ts), which buffers,
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resamples and fades playback edges. Input speech can clear playback for barge-in.
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Audio worklets are loaded through `AudioWorklet.addModule`; keep their processor
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registration structure intact when editing them. The speech backend's thread
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and cancellation model is documented in [realtime API](../speech/realtime-api.md).
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## Reasoning and context
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The browser triggers external reasoning on completed user transcripts only in
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`OPENAI` or `NODE_RED` mode. Node-RED `log_only=true` responses leave native speech
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output running; an answer-producing response uses the external-answer path.
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The server can independently forward assistant text to Node-RED for paired
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conversation logs. These HTTP operations supplement the realtime audio path.
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Read [reasoning](reasoning.md), [context injection](context-injection.md), and
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[tool calling](tool-calling.md) for the conditions and limitations of each path.
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