fix: handle GPT-5.x models not supporting the stop API parameter#5144
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fix: handle GPT-5.x models not supporting the stop API parameter#5144lucasgomide wants to merge 1 commit intomainfrom
stop API parameter#5144lucasgomide wants to merge 1 commit intomainfrom
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stop API parameter
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GPT-5.x models reject the `stop` parameter at the API level with "Unsupported parameter: 'stop' is not supported with this model". This breaks CrewAI executions when routing through LiteLLM (e.g. via
OpenAI-compatible gateways like Asimov), because the LiteLLM fallback path always includes `stop` in the API request params.
The native OpenAI provider was unaffected because it never sends `stop` to the API — it applies stop words client-side via `_apply_stop_words()`. However, when the request goes through LiteLLM (custom endpoints, proxy gateways),
`stop` is sent as an API parameter and GPT-5.x rejects it.
Additionally, the existing retry logic that catches this error only matched the OpenAI API error format ("Unsupported parameter") but missed
LiteLLM's own pre-validation error format ("does not support parameters"), so the self-healing retry never triggered for LiteLLM-routed calls.
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| with patch("litellm.completion", side_effect=mock_completion): | ||
| with caplog.at_level(logging.INFO): | ||
| result = llm.call("What is the capital of France?") |
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Note
Medium Risk
Changes request parameter construction and retry logic for LiteLLM/OpenAI calls; incorrect model detection could alter stop-word behavior or truncation for some models.
Overview
Prevents GPT‑5 family models from receiving the unsupported
stopAPI parameter by gating it behindsupports_stop_words()in both the LiteLLM fallback (LLM._prepare_completion_params) and native OpenAI provider (OpenAICompletion.supports_stop_words).Improves the “retry without
stop” detection to also match LiteLLM’sUnsupportedParamsErrormessage format, and adds unit/integration coverage (including a VCR cassette) to ensure GPT‑5 calls succeed while still applying stop words client-side.Written by Cursor Bugbot for commit 5ed8633. This will update automatically on new commits. Configure here.