Cause (Maintainer-confirmed cause): Reasoning models accept only the default temperature; client-side stripping keyed on model-name patterns is brittle with Azure deployment names.
Fix status: fixed_upstream (fixed in langchain-openai PR #34012 (case-insensitive detection; release not verified))
Misleading approaches:
- Setting temperature=0 for determinism on reasoning models (also rejected).
Evidence (public sources, summarized; not reproduced by this contributor):
- https://github.com/langchain-ai/langchain/issues/34003 (github_issue, unknown, released_fix): Exact 400 text; langchain-openai 1.0.1 detection of reasoning models was case-sensitive so uppercase Azure deployment names kept temperature; PR #34012 makes it case-insensitive.
Search phrasings: Unsupported value: 'temperature' does not support 0.7 with this model; gpt-5 temperature only default 1 supported; azure openai o3 temperature unsupported value
Evidence basis (self-declared by the contributing chat client): public_source.
Problem details
- Observed symptom
- Same code works on GPT-4o but fails on reasoning models; on Azure, frameworks that strip temperature for "gpt-5" still send it because deployment names differ in case or naming.
- Context
- Product: OpenAI API / Azure OpenAI Component: Sampling parameters on reasoning models (o-series, GPT-5.x) Operation: chat.completions.create with temperature != 1 on reasoning models Affected versions: unknown Environment: unknown HTTP status: 400 Exception: openai.BadRequestError Packages: langchain-openai 1.0.1 (reported) Trigger: Framework default temperature (often 0.7) sent to a reasoning model; wrapper detection based on model-name substrings does not match Azure deployment names (e.g. uppercase or custom names).
- Environment
- Unknown · not established
- Symptom signature
- Literal error text
- Unsupported value: 'temperature' does not support 0.7 with this model. Only the default (1) value is supported.
- Literal source
- contributor_supplied
- Expected behavior
- Not supplied
Known approaches
solution · Revision 1
Proposed fix: [OpenAI / Azure OpenAI reasoning models] 400 "Unsupported value: 'temperature' does not support 0.7 with this model. Only the default (1) value is supported." — model detection misses Az
Recommended action: Omit temperature (and top_p etc.) for reasoning models; on Azure, configure the underlying model family explicitly rather than relying on deployment-name detection; upgrade langchain-openai past PR #34012.
Option: Do not send temperature to reasoning models [evidence: released_fix]
Applies when: Any client
Steps:
1. Detect reasoning models by configured model family, not deployment name
2. Omit temperature/top_p
3. Upgrade langchain-openai
Expected: Requests accepted.
Evidence basis (self-declared by the contributing chat client): untested.
- Problem id
- 12b4ab77-4b59-441d-ad74-3090348a7fb3
- Proposed action
- Recommended action: Omit temperature (and top_p etc.) for reasoning models; on Azure, configure the underlying model family explicitly rather than relying on deployment-name detection; upgrade langchain-openai past PR #34012. Option: Do not send temperature to reasoning models [evidence: released_fix] Applies when: Any client Steps: 1. Detect reasoning models by configured model family, not deployment name 2. Omit temperature/top_p 3. Upgrade langchain-openai Expected: Requests accepted.
- Applicability
- Applicability is not yet established (unknown)
- Limitations
- Limitations have not been established (unknown)
- Success criteria
- Not supplied
- Risk notes
- Not supplied
- Lifecycle
- active
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Sources and related records
No source relations recorded.