fix(openai): support vLLM >=0.19.1 delta.reasoning field for streaming reasoning content#2191
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fix(openai): support vLLM >=0.19.1 delta.reasoning field for streaming reasoning content#2191Zelys-DFKH wants to merge 2 commits intostrands-agents:mainfrom
Zelys-DFKH wants to merge 2 commits intostrands-agents:mainfrom
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…g reasoning content vLLM 0.19.1 renamed the streaming reasoning field from delta.reasoning_content to delta.reasoning. The SDK only checked reasoning_content, silently dropping reasoning output from vLLM backends on the new field name. Check both field names (reasoning_content first for backward compat with DeepSeek/older vLLM, then reasoning), so reasoning content is forwarded regardless of which field the backend populates. Fixes strands-agents#2182 Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
…llback When both delta.reasoning_content and delta.reasoning are present, reasoning_content takes priority (backward compat). Assert this explicitly. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Description
vLLM 0.19.1 renamed the streaming reasoning field from
delta.reasoning_contenttodelta.reasoning. The SDK only checkedreasoning_content, so reasoning output wassilently dropped for users on newer vLLM backends.
OpenAIModel._stream()now checks both field names:reasoning_contentfirst (backwardcompat with DeepSeek and older vLLM), then
reasoning. Whichever is set gets forwarded.The existing OpenAI mock deltas also needed
reasoning=Noneset explicitly.unittest.mock.Mockauto-creates any accessed attribute as a truthy value, so withoutit the fallback would have fired on all the old tests. Three new tests cover the
delta.reasoningpath, the priority behavior when both fields are present, and theexisting
delta.reasoning_contentpath via the updated mocks.Related Issues
#2182
Documentation PR
No documentation changes needed.
Type of Change
Bug fix
Testing
hatch run preparepassed: 2647 passed, 4 skipped.hatch run prepareChecklist
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