AI API receipt · BerriAI/litellm

Parallel tool-call arguments dropped when streaming /v1/messages

BerriAI/litellm#45348 · upstream bug as reported in the issue (not re-run)

✓ Badgr rejects this response

Two parallel tool calls streamed; the second one's arguments never arrived.

Outcome contract verdict: tool call arguments are empty. The attempt is recorded as failed (invalid_outcome) instead of a verified success, so it is not billed as a good answer and can fall back to another route.

What the upstream returned (replayed)

The output the bug produces, taken from the issue’s reproduction and fed to Badgr’s validators. Not a live provider call.

data: {"choices": [{"index": 0, "delta": {"tool_calls": [{"index": 0, "function": {"arguments": "{\"x\": \"1\"}", "name": "a"}}]}, "finish_reason": null}]}
data: {"choices": [{"index": 0, "delta": {"tool_calls": [{"index": 1, "function": {"arguments": "", "name": "b"}}]}, "finish_reason": null}]}
data: {"choices": [{"index": 0, "delta": {}, "finish_reason": "tool_calls"}]}
data: [DONE]

Badgr receipt

Written by Badgr’s receipt ledger and read back from GET /v1/receipts/replay-litellm-45348-parallel-tool-args-dropped.

{
  "request_id": "replay-litellm-45348-parallel-tool-args-dropped",
  "status": "failed",
  "endpoint": "/v1/chat/completions",
  "stream": true,
  "failure_stage": "stream_contract",
  "error_code": "invalid_outcome",
  "error_message": "Stream did not complete a valid response: tool call arguments are empty",
  "retryable": true,
  "provider_mode": "replay",
  "routing_decision": "replayed_upstream_output",
  "created_at": "2026-10-09T02:14:36Z"
}

Recorded 2026-10-09 in Badgr’s local development environment. Replay cases and verdicts are pinned by backend/test_ai_api_replay_cases.py.

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