Fix vllm_plugin import crash when vLLM's AudioMediaIO location changes

[Ammar Hashmi (ammar-iitm)]

Summary

• Fixes vllm asr problem #222: deploying VibeVoice-ASR via vLLM crashes at plugin import time on some vLLM versions with:

  File "/app/vllm_plugin/model.py", line 76, in <module>
      _OriginalAudioMediaIO = _vllm_audio_module.AudioMediaIO
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  AttributeError: module 'vllm.multimodal.audio' has no attribute 'AudioMediaIO'
  

• Root cause: vllm_plugin/model.py locates vLLM's AudioMediaIO under one of two module paths depending on vLLM version (it moved between releases), falling back to the old path on ImportError. But in the reporter's environment, the old-path module (vllm.multimodal.audio) still exists — it just no longer defines AudioMediaIO — so the attribute access raises AttributeError, not ImportError, which the except ImportError: clause doesn't catch. This crashes the whole plugin at import time, blocking any deployment on that vLLM build.
• Elsewhere in this exact same file (a few lines down, the "utils module" patch), the code already correctly catches (ImportError, AttributeError) for the same class of problem — this PR brings the first fallback in line with that established pattern, and additionally degrades gracefully (skip the optional FFmpeg-decoding override, log a warning) rather than crashing outright if AudioMediaIO can't be found in either known location.

Change

• vllm_plugin/model.py: catch (ImportError, AttributeError) when resolving AudioMediaIO's original location. If it can't be found anywhere, print a [VibeVoice] WARN: message and skip the FFmpeg-decoding patch instead of crashing — vLLM's built-in audio decoding still works, so the plugin still loads.
• No change to behavior when AudioMediaIO is found (new or old location) — same subclass, same module patching as before.

Test plan

• python3 -m py_compile vllm_plugin/model.py
• Standalone reproduction using a fake vllm module tree (no real vLLM install needed), covering 4 scenarios:
  • The exact issue vllm asr problem #222 scenario (new location missing, old location module present but lacking AudioMediaIO) — previously crashed, now degrades gracefully with a warning.
  • A fully-incompatible future vLLM (neither location has AudioMediaIO) — same graceful degradation.
  • New-location vLLM (modern) — patch still applies: confirmed _PatchedAudioMediaIO is a subclass of the real AudioMediaIO, the module attribute is replaced, and load_bytes/load_base64/load_file behave as before.
  • Old-location vLLM (legacy) — same confirmation.
• Not verified: an actual vllm serve run against the specific vLLM build from the report (would need that exact vLLM version installed) — would appreciate confirmation from the reporter or a maintainer.

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https://claude.ai/code/session_016fM2LafALmBK16KnFWjsp7