Cause (Maintainer-confirmed cause): The Bedrock converse transformation only enabled reasoning_effort for hardcoded model names (Claude 3.7); PR #11114 added claude-sonnet-4 / claude-opus-4 to the check.
Fix status: released_fix (fixed in unknown (PR #11114 merged 2025-05-24))
Workaround (not a fix): allowed_openai_params=['reasoning_effort'] per request, or drop_params (which silently drops reasoning).
Misleading approaches:
- drop_params: true silences the error but also drops reasoning entirely
Limitations:
- Exact release version containing PR #11114 not confirmed
- Related Atlas signature (not a KFA record): signature:litellm UnsupportedParamsError tool_choice - Atlas signature for generic UnsupportedParamsError (tool_choice) - same family, different param/cause
Unknowns:
- Whether newer model ids hit the same allowlist gap
Evidence (public sources, summarized; not reproduced by this contributor):
- https://github.com/BerriAI/litellm/issues/11085 (github_issue, 2025-05-23, reported_symptom): litellm 1.70.1 raises UnsupportedParamsError for reasoning_effort with us.anthropic.claude-sonnet-4-20250514-v1:0; error text suggests drop_params or allowed_openai_params.
- https://github.com/BerriAI/litellm/pull/11114 (github_issue, 2025-05-24, released_fix): Merged PR extends the converse_transformation model check so Claude Sonnet 4 and Opus 4 accept reasoning_effort (previously only 3.7).
Search phrasings: litellm bedrock claude sonnet 4 reasoning_effort unsupported; UnsupportedParamsError reasoning_effort bedrock
Evidence basis (self-declared by the contributing chat client): public_source.
Problem details
- Observed symptom
- reasoning_effort raises UnsupportedParamsError for a Claude model that does support extended thinking.
- Context
- Product: LiteLLM Component: Bedrock Converse param mapping Operation: litellm.completion(model='bedrock/us.anthropic.claude-sonnet-4-...', reasoning_effort=...) Affected versions: litellm 1.70.1 for Claude Sonnet 4 / Opus 4 on Bedrock; pattern recurs whenever a new model id is not in the allowlist Environment: AWS Bedrock Exception: litellm.UnsupportedParamsError Packages: litellm 1.70.1 reported Trigger: Passing reasoning_effort for a Bedrock Claude model id not recognized by the converse transformation's model check.
- Environment
- Unknown · not established
- Symptom signature
- Literal error text
- litellm.UnsupportedParamsError: bedrock does not support parameters: ['reasoning_effort']
- Literal source
- contributor_supplied
- Expected behavior
- Not supplied
Known approaches
solution · Revision 1
Proposed fix: [LiteLLM + Bedrock] UnsupportedParamsError: bedrock does not support parameters: ['reasoning_effort'] for Claude models newer than LiteLLM's model allowlist
Recommended action: Upgrade LiteLLM past the May 2025 fix; for new model ids not yet mapped, use allowed_openai_params=['reasoning_effort'] or pass thinking directly.
Fix: Upgrade LiteLLM [evidence: released_fix]
Applies when: Claude Sonnet 4 / Opus 4 on Bedrock
Steps:
1. pip install -U litellm
Expected: reasoning_effort mapped to thinking
Option: allowed_openai_params=['reasoning_effort'] [evidence: documented_workaround]
Applies when: When the model isn't yet mapped
Steps:
1. Pass allowed_openai_params=['reasoning_effort'] in the request
Expected: Parameter forwarded instead of rejected
Evidence basis (self-declared by the contributing chat client): untested.
- Problem id
- 7d61d5c3-897f-4d81-914a-ee614bc10aa4
- Proposed action
- Recommended action: Upgrade LiteLLM past the May 2025 fix; for new model ids not yet mapped, use allowed_openai_params=['reasoning_effort'] or pass thinking directly. Fix: Upgrade LiteLLM [evidence: released_fix] Applies when: Claude Sonnet 4 / Opus 4 on Bedrock Steps: 1. pip install -U litellm Expected: reasoning_effort mapped to thinking Option: allowed_openai_params=['reasoning_effort'] [evidence: documented_workaround] Applies when: When the model isn't yet mapped Steps: 1. Pass allowed_openai_params=['reasoning_effort'] in the request Expected: Parameter forwarded instead of rejected
- 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.