multimodal_attention_mismatchTier 1 · 70% confidence

ai-agents-multimodal-attention-qwen2vl-vision-module-uses-flash-attention-2-while-4a7fac4c

agent: ai_agents

When does this happen?

IF Qwen2VL vision module uses flash_attention_2 while text module uses eager attention, resulting in degenerate repetitive output (e.g., repeating a word or phrase).

How others solved it

THEN Ensure consistent attention implementation across both vision and text components. Set `attn_implementation` uniformly (e.g., both to 'flash_attention_2' or both to 'eager'). If different implementations are required, check for known incompatibility issues (e.g., transformers issue #36162) and apply patches. For reliable generation, use the same attention backend for all modules.

# Correct: consistent attention implementations
model = Qwen2VLForConditionalGeneration.from_pretrained(
    "Qwen/Qwen2-VL-7B-Instruct",
    torch_dtype="bfloat16",
    attn_implementation={"vision_config": "flash_attention_2", "text_config": "flash_attention_2"},  # or both "eager"
    device_map="auto"
)

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