* fix(streaming): stop re-wrapping a bridged stream's MidStreamFallbackError
A chat completion served over the Responses API already gets its mid-stream
error wrapped by the Responses iterator. The chat stream wrapper wrapped it a
second time, and the router unwraps one layer, so the client saw the inner
sentinel (message prefixed litellm.MidStreamFallbackError, type null) instead
of the provider's RateLimitError. The chat wrapper now re-raises an already
wrapped error untouched.
* test(streaming): type the bridged stream regression test's locals
* fix(streaming): rebuild a bridged mid-stream error with the outer wrapper's bookkeeping
* test(integration): cover the bridged stream error typing on every surface
Checked-in audit cells for the Responses bridge: chat completions through the OpenAI SDK and httpx, /v1/messages through httpx and the Anthropic SDK, native /v1/responses, the litellm and Router SDK stream paths, and a chaos file with a mixed burst, a worker SIGKILL and a proxy SIGTERM against an owned two-worker proxy. Every cell scripts the provider through a wire server and asserts the caller's body, the upstream's received requests and the spend row by id.
* test(integration): read bridged chat content through one helper
* test(integration): build the bridged fallback config without mutating the loaded yaml
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Co-authored-by: mateo-berri <277851410+mateo-berri@users.noreply.github.com>
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