fix: prevent duplicate tool calls in Responses-to-Chat streaming

[nikuleo]

📝 变更描述 / Description

Responses-to-Chat 流式转换里，工具调用的 key 有两种形态：流式事件带 output_index，注册成 output:<n>；response.completed 的完整 output 在 terminalOutputChunks 里被构造成没有 output_index 的合成事件，算出来是 item:<id>。ensureToolForEvent 之前只查 toolByKey，key 对不上就直接建新 tool——于是同一个 function call 拿到第二个 tool_calls index，完整 arguments 被重发一遍。对自动执行工具的 Agent 客户端，这等于同一个工具被调用两次。

而 OpenAI 官方的 response.completed 本来就携带完整 output（含已流式发送过的 function_call item），这是必须正确处理的正常事件形态。

修复：ensureToolForEvent 在直接 key 未命中时，先用已登记的 itemIDToKey、callIDToKey 反查已存在的 tool，找到就把新 key alias 过去；全部未命中才创建新 tool。这和同文件里非流式路径 ResponsesBufferedAccumulator.findToolIndex 的既有语义一致（它本来就会按 item ID 反查再新建）。terminal-only 工具调用（部分兼容上游只在终止事件里给出工具调用）不受影响，反查不到时仍走原有新建逻辑，对应的既有测试保持通过。

🚀 变更类型 / Type of change

• 🐛 Bug 修复 (Bug fix)
• ✨ 新功能 (New feature)
• ⚡ 性能优化 / 重构 (Refactor)
• 📝 文档更新 (Documentation)

🔗 关联任务 / Related Issue

• Closes Bug: Responses-to-Chat streaming duplicates tool calls on response.completed #6223
• Related to fix: preserve Responses streaming tool call arguments #5745, fix(openai): harden Chat-to-Responses compatibility #5772

✅ 提交前检查项 / Checklist

• 人工确认: 我已亲自整理并撰写此描述，没有直接粘贴未经处理的 AI 输出。
• 非重复提交: 我已搜索现有的 Issues 与 PRs，确认不是重复提交。
• Bug fix 说明: 若此 PR 标记为 Bug fix，我已提交或关联对应 Issue，且不会将设计取舍、预期不一致或理解偏差直接归类为 bug。
• 变更理解: 我已理解这些更改的工作原理及可能影响。
• 范围聚焦: 本 PR 未包含任何与当前任务无关的代码改动。
• 本地验证: 已在本地运行并通过测试或手动验证，维护者可以据此复核结果。
• 安全合规: 代码中无敏感凭据，且符合项目代码规范。

📸 运行证明 / Proof of Work

新增回归测试 TestResponsesStreamEventToChatChunksDoesNotResendToolOnTerminalOutput（事件序列：output_item.added -> function_call_arguments.delta -> 携带完整 output 的 response.completed），修复前失败、修复后通过。

修复前（main @ a63364d）：

--- FAIL: TestResponsesStreamEventToChatChunksDoesNotResendToolOnTerminalOutput (0.00s)
    Error: Not equal:
           expected: "{\"q\":\"x\"}"
           actual  : "{\"q\":\"x\"}{\"q\":\"x\"}"

修复后：

--- PASS: TestResponsesStreamEventToChatChunksDoesNotResendToolOnTerminalOutput (0.00s)

$ go vet ./service/relayconvert/...
$ go test ./service/relayconvert/... -count=1
ok      github.com/QuantumNous/new-api/service/relayconvert                           1.790s
ok      github.com/QuantumNous/new-api/service/relayconvert/internal/oai_chat        2.709s
ok      github.com/QuantumNous/new-api/service/relayconvert/internal/oai_responses   2.221s

既有测试全部通过，terminal-only 工具调用场景（TestResponsesStreamEventToChatChunksUsesTerminalDoneOutput）不受影响。另已本地验证：多个不同工具仍分配不同 index；流式只发送部分 arguments、终止事件携带完整 arguments 时，只在同一 index 下补发差量。

本 PR 由 AI 辅助完成（AI-assisted），我已逐行审阅并在本地验证。

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Prevented duplicate tool calls from appearing when a response stream ends with a completed event.
  • Preserved tool call arguments and final completion status correctly across streamed responses.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 54a1ac28-de0a-453a-8d13-5944ead42eb3

📥 Commits

Reviewing files that changed from the base of the PR and between a63364d and c38f2f5.

📒 Files selected for processing (2)

• service/relayconvert/internal/oai_responses/to_oai_chat_resp_test.go
• service/relayconvert/internal/oai_responses/to_oai_chat_stream_resp.go

---

Walkthrough

The streaming Responses-to-Chat converter now reuses existing tool state when terminal events use a different key format. A unit test verifies that repeated terminal tool data produces one tool index, the expected arguments, and a tool_calls finish reason.

Changes

Responses-to-Chat tool deduplication

Layer / File(s)	Summary
Tool reconciliation and regression coverage service/relayconvert/internal/oai_responses/to_oai_chat_stream_resp.go, service/relayconvert/internal/oai_responses/to_oai_chat_resp_test.go	ensureToolForEvent re-associates tools using item or call ID mappings, while the regression test verifies that terminal output does not duplicate tool indices or arguments.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• QuantumNous/new-api#5787: Related Responses-to-Chat streaming tool argument buffering and deduplication fixes.

Suggested reviewers: calcium-ion

Poem

I’m a rabbit with tools in my burrow tonight,
One call hops through the stream just right.
No doubled carrots, no arguments spun,
The terminal echo counts only one.
tool_calls says: the work is done!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the fix for duplicate tool calls in Responses-to-Chat streaming.
Linked Issues check	✅ Passed	The code reuses existing tool state by item/call ID and the regression test covers the duplicate-terminal-output case in #6223.
Out of Scope Changes check	✅ Passed	The changes are narrowly focused on the reported streaming duplication bug and its regression test.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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