Azure Foundry's OpenAI-compatible Responses surface rejects the post-tool
follow-up payload with HTTP 400 `invalid_payload` when a replayed encrypted
`reasoning` item is sent alongside `function_call` / `function_call_output`.
The initial function-call request and ordinary multi-turn continuity are both
accepted, so the failure only appears after the first tool executes.
Detect the Foundry endpoint in `ResponsesApiTransport.build_kwargs` and drop
only the encrypted reasoning replay on that follow-up turn, leaving
function_call / function_call_output continuity intact.
Salvage of #59981, rebuilt on current main. Same root cause and fix direction
as the original, which was correct; this version resolves three defects:
- No `chat_completion_helpers.py` change. main already forwards `provider`
and `base_url` to the Responses transport, so the original's re-added
arguments produced `SyntaxError: keyword argument repeated: provider` on
merge. Dropping the hunk removed the syntax error and the conflict.
- Host matching uses `utils.base_url_host_matches`, not a substring test.
`".services.ai.azure.com" in base_url` also matches URLs carrying the
domain in a path or query segment, which would silently disable reasoning
replay on an unrelated provider.
- The post-tool predicate tests the trailing messages, not the whole history.
Scanning for any tool call plus any tool result made it sticky: one tool
call early in a conversation suppressed reasoning on every later turn.
- Tool calls pair on `call_id` as well as `id`. Responses histories carry the
function call id in `call_id` while `id` holds the response item id
(`fc_...`). Identity is resolved via the converter's own
`_split_responses_tool_id`, covering composite `"call_x|fc_y"` ids and bare
`fc_` ids on both sides of the pairing.
Tests: 27 cases across the transport and the live `build_api_kwargs` bridge,
including six parametrized tool-call id shapes, non-Foundry host lookalikes,
the sticky-history guard, parallel tool results, and an unpaired tool result.
Each guard was confirmed to catch its defect by reverting the fix.
Verified with `scripts/run_tests.sh tests/agent/ tests/run_agent/`:
532 files, 5602 tests passed, 0 failed.
Not verified against a live Azure Foundry endpoint — no credentials. The
original HTTP 400 reproduction and post-fix Foundry Project / Azure Container
Apps harness runs are @AshuJoshi's, from #59981. This change is verified at
the payload-construction layer only.
Closes#59981.
Co-authored-by: Ashu Joshi <AshuJoshi@users.noreply.github.com>
Ben Barclay
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