feat(js-sdk): add proxy transport and custom signaling

[stukennedy]

This allows a user to choose to use a proxy of the Websocket client
e.g. with https://github.com/stukennedy/anam-ws-proxy

Use-case for this is a man-in-the-middle approach, where a 3rd-party server handles their own orchestration layer -> LLM inference and then stream talks directly in the Anam Websocket, cutting out the need to send responses back to the client and for the client to send the talk stream to Anam.
The client also doesn't need to negotiate the session at all, just gets a signalling websocket from the server which negotiates the WebRTC session.

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Summary by cubic

Add proxy transport mode to the JS SDK, enabling server-side session negotiation and custom signaling over a proxied WebSocket. This lets a backend orchestrate inference and stream directly to Anam while the client only connects to your proxy.

• New Features
  • Proxy transport: transport.mode='proxy' with baseUrl, optional startSessionPath and agentWsPathTemplate, getUserId, and headers in AnamPublicClientOptions.
  • ExternalSessionClient: starts sessions via your server and returns engine/signaling details.
  • AnamClient: uses ExternalSessionClient in proxy mode and passes an absolute WebSocket URL to SignallingClient.
  • SignallingClient: supports absoluteWsUrl; adds sendCustom(actionType, payload) and sendBinary(...).
  • SignalMessage: actionType widened to string for custom actions.
  • Types/TS: baseUrl now optional in SignallingURLOptions; DOM lib and skipLibCheck enabled; minimal buffer shim for browser builds. Direct mode remains the default.

^{Written for commit c439054. Summary will update on new commits.}

[cubic-dev-ai]

1 issue found across 8 files

Prompt for AI agents (all 1 issues)

Understand the root cause of the following 1 issues and fix them.


<file name="src/types/signalling/SignallingClientOptions.ts">

<violation number="1" location="src/types/signalling/SignallingClientOptions.ts:2">
Making baseUrl optional removes compile-time enforcement; invalid configs are now caught only at runtime. Consider a discriminated union where either absoluteWsUrl is provided or baseUrl is required.</violation>
</file>

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