[cunninghamcard-bit]

Summary

Before: xAI streaming transcription opened its WebSocket in do_stream and returned a connect failure (a refused connection, a failing custom connector) as the Err of do_stream itself.

After: as in @ai-sdk/xai 5.0.12, do_stream still opens the socket before it returns (upstream's ReadableStream start runs while doStream builds the stream), but a connect failure no longer fails do_stream: the returned stream yields it as its only item and ends, which drops the caller's audio stream (upstream cancels it).

Found while porting the upstream xAI tests (case doStream › should cancel the audio stream when the WebSocket constructor throws). Part of the #276 list.

How it works today

XaiTranscriptionModel::do_stream                      aimux-providers/src/xai/transcription.rs:210   // upstream: XaiTranscriptionModel.doStream  xai-transcription-model.ts
└─ stream::do_stream                                  transcription.rs:295
   ├─ Opts::parse, multichannel check, warnings       :296-334
   ├─ ws_connect(&WebSocketRequest::for_transcription(..)).await?
   │                                                  :338   ← connect failure returns Err from do_stream
   │                                                         // upstream: connectToWebSocket runs in the ReadableStream's start (:276-358);
   │                                                         //   a failure goes to finishWithError → cleanup cancels audio → controller.error
   ├─ async_stream::stream! { audio / ws.next() loop } :355
   └─ Ok(TranscriptionStreamResult { stream, .. })    :489
aimux-provider-utils/src/ws.rs:477  ws_connect → connector.connect or tungstenite

What this PR changes

stream::do_stream                                     transcription.rs:295
├─ let connected = ws_connect(..).await               :340   no `?`: the Result is handed to the stream
└─ async_stream::stream! {                            :357
     let mut ws = match connected {                   :358
         Ok(ws) => ws,
         Err(e) => { yield Err(e); return; }          ← the stream's error; ending the stream drops `audio`
     };
     … the existing loop, unchanged
   }

The socket is still opened before do_stream returns, so a stream dropped unread has connected, as upstream's has (its case should strip undefined header values before the WebSocket constructor reads the handshake after cancelling the unread stream).

Tests (tests/xai_transcription_test.rs): a_connect_failure_errors_the_stream points the model at a closed port and expects do_stream to resolve and the stream to hold one error; it fails on master with do_stream resolves; the connect failure arrives on the stream: ApiCall(... "websocket connect failed: ... Connection refused"). The upstream case is ported in the xAI test PR.

Docs: CHANGELOG Fixed.

Type of change

• Bug fix (non-breaking)
• New feature (non-breaking)
• Breaking change
• New provider
• New / updated binding
• Docs / RFC

Checklist

• cargo +1.99 fmt -p aimux-providers -- --check passes
• cargo +1.99 clippy -p aimux-providers --lib --tests -- -D warnings passes
• cargo +1.99 test -p aimux-providers --test xai_transcription_test passes (19)
• scripts/check_provider_boundaries.sh passes
• Updated relevant docs (CHANGELOG)
• Commit messages follow Conventional Commits

Notes for reviewers

Only xAI changes here. ElevenLabs streaming transcription also returns a connect failure from do_stream (elevenlabs.rs:941); it is not touched, since its upstream package is ported separately.

🤖 Generated with Claude Code

https://claude.ai/code/session_01RoxcKU4zBD64Lri3e4Lrq5

[cunninghamcard-bit]

Folded into #311 together with the other xAI fixes, so each vendor has one fix PR. This change is commits 1852ed5d and e6084f08 there. Closing this one; the branch stays as it is.

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