test(audio): assert dropped transcription streams by error type and cause on SDK 3

Main's transcription streaming tests matched the upstream transport message,
which openai SDK 3 replaces with "Connection error." when a stream read fails.
Assert the LiteLLM APIConnectionError and the dropped connection in its cause
chain instead, which holds on SDK 2 and 3.

tests/unit/litellm_core_utils/audio_utils/test_transcription_streaming.py

@@ -19,6 +19,7 @@ from litellm.litellm_core_utils.audio_utils.transcription_streaming import (
     litellm_exception_mapper,
     wrap_transcription_stream,
 )
+from litellm.llms.custom_httpx.transport_errors import TransportErrorKind, chained_transport_error_kind
 from litellm.types.utils import TranscriptionResponse
 
 _STARTED_AT: Final = datetime.datetime(2026, 10, 28, 12, 0, 0)  # noqa: DTZ001  # callback timestamps use the legacy naive contract
@@ -177,10 +178,12 @@ async def test_a_stream_the_upstream_drops_mid_transcript_raises_a_litellm_error
         model="openai/gpt-transcribe", file=("sample.wav", b"audio"), stream=True, client=upstream
     )
 
-    with pytest.raises(litellm.APIConnectionError, match="peer closed connection"):
+    with pytest.raises(litellm.APIConnectionError) as raised:
         async for _ in stream:
             pass
 
+    assert chained_transport_error_kind(raised.value) is TransportErrorKind.DROPPED_CONNECTION
+
 
 class _FailureHookCounter(CustomLogger):
     def __init__(self) -> None:

tests/unit/proxy/proxy_server/test_routes_audio.py

@@ -1037,7 +1037,7 @@ def test_streamed_transcription_error_mid_stream_ends_with_an_error_event_and_ru
     assert tuple(frame.get("delta") for frame in frames[:2]) == ("hello ", "world")
     assert len(frames) == 3
     assert data_lines[-1] == "[DONE]"
-    assert "upstream connection dropped" in frames[2]["error"]["message"]
+    assert "APIConnectionError" in frames[2]["error"]["message"]
     assert "/srv/app/stt_stream.py" not in frames[2]["error"]["message"]
     assert "stt.internal.corp" not in frames[2]["error"]["message"]
     assert set(frames[2]["error"]) == {"message", "type", "param", "code"}