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fix(chat-completions): merge a streamed turn's message into its pending tool-call message - #4728
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seratch merged 1 commit intoAug 28, 2026
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…ll message A provider that streams tool-call deltas before the same turn's text yields response outputs ordered [function_call, message]. Replaying that history through Converter.items_to_messages flushed the tool_calls message and opened a second assistant message for the text. Chat Completions rejects an assistant message with tool_calls that is not directly followed by its tool messages, so the next turn failed with 400 and the session was unrecoverable. The same turn converted correctly when not streamed. Merge the message into the pending assistant message instead. A function_call_output always flushes, so tool calls from a previous turn cannot still be pending when a message item arrives: the merge only triggers on the same-turn streamed ordering. Streamed and non-streamed histories now convert identically, and histories already persisted in sessions are healed on replay. Four regression tests; all fail on main.
seratch
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Summary
A provider that streams tool-call deltas before the same turn's text yields response outputs ordered
[function_call, message]. Replaying that history throughConverter.items_to_messagesflushed the pending tool_calls message when the message item arrived and opened a second assistant message for the text. Chat Completions rejects an assistant message withtool_callsthat is not directly followed by its tool messages, so the next turn failed with 400 and the session was unrecoverable. The identical turn converted correctly when not streamed.This PR merges the message into the pending assistant message instead. The merge only triggers on the same-turn streamed ordering: a
function_call_outputalways flushes, so tool calls from a previous turn cannot still be pending when a message item arrives. Streamed and non-streamed histories now convert identically, and histories already persisted in sessions are healed on replay. When legacy thinking blocks were already reconstructed into content parts, the text is appended as a content part rather than discarded.Fixes #4727.
Test plan
tests/models/test_openai_chatcompletions_converter.py: the merged turn, streamed/non-streamed convergence, no merging across turn boundaries, and refusal merging. All four fail onmain..agents/skills/code-change-verification/scripts/run.sh): format, lint, typecheck pass; tests 9217 passed, 28 skipped, with one failure —tests/sandbox/test_run_cwd.py::test_python_skill_uses_absolute_root_from_nested_workdir, which fails identically on a cleanmaincheckout in this environment (local sandbox setup, unrelated to this change).Issue number
Closes #4727
Checks
.agents/skills/code-change-verification/scripts/run.sh/reviewbefore submitting this PR