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fix: report prompt_tokens correctly for LLM models in SimpleEngine #236

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Merged
waybarrios merged 2 commits into from
Mar 31, 2026
Merged

fix: report prompt_tokens correctly for LLM models in SimpleEngine #236

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38479fe
fix: report prompt_tokens correctly for LLM models in SimpleEngine
sjswerdloff Mar 30, 2026
54b4d65
cleanup: remove redundant fallback tokenization and defensive hasattr…
waybarrios Mar 31, 2026
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13 changes: 12 additions & 1 deletion vllm_mlx/engine/simple.py
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Original file line number Diff line number Diff line change
Expand Up @@ -369,7 +369,7 @@ async def stream_generate(
):
prompt_tokens = (
chunk.prompt_tokens
if hasattr(chunk, "prompt_tokens")
if hasattr(chunk, "prompt_tokens") and chunk.prompt_tokens
else prompt_tokens
)
completion_tokens += 1
Expand Down Expand Up @@ -472,9 +472,20 @@ async def chat(
**kwargs,
)
text = clean_output_text(output.text)
# Count prompt tokens from the full templated prompt
tokenizer = self._model.tokenizer
template_kwargs = {
"tokenize": True,
"add_generation_prompt": True,
}
if template_tools:
template_kwargs["tools"] = template_tools
prompt_ids = tokenizer.apply_chat_template(messages, **template_kwargs)
prompt_token_count = len(prompt_ids)
return GenerationOutput(
text=text,
tokens=output.tokens,
prompt_tokens=prompt_token_count,
completion_tokens=len(output.tokens),
finish_reason=output.finish_reason,
)
Expand Down
5 changes: 5 additions & 0 deletions vllm_mlx/models/llm.py
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,7 @@ class StreamingOutput:
token: int
finished: bool = False
finish_reason: str | None = None
prompt_tokens: int = 0


class MLXLanguageModel:
Expand Down Expand Up @@ -203,6 +204,9 @@ def stream_generate(
# Create sampler with parameters
sampler = self._create_sampler(temperature, top_p)

# Count prompt tokens once upfront
num_prompt_tokens = len(self.tokenizer.encode(prompt))

token_count = 0
accumulated_text = ""

Expand Down Expand Up @@ -241,6 +245,7 @@ def stream_generate(
token=response.token if hasattr(response, "token") else 0,
finished=finished,
finish_reason=finish_reason,
prompt_tokens=num_prompt_tokens,
)

if finished:
Expand Down
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