fix: convert OpenAI tool result images for Claude

[Maoyitt]

⚠️ 提交说明 / PR Notice

Important

• 请提供人工撰写的简洁摘要，避免直接粘贴未经整理的 AI 输出。

Note

This change was AI-assisted. The scope, root cause, generated payload, and test results were reviewed during preparation; the PR has been reviewed by the submitter and marked ready for review.

📝 变更描述 / Description

OpenAI Chat Completions 的普通消息在转换到 Claude Messages 时，会将 image_url 解析为 Claude 原生的 image/source。但 role: tool 分支此前直接把 message.Content 写入 tool_result.content，导致工具返回的图片仍以 OpenAI image_url 结构发送给 Claude 兼容上游并触发参数校验错误。

本修改仅转换工具结果内容中的 image_url：沿用现有媒体解析逻辑读取 URL 或 Base64 数据，并输出 Claude image（PDF 输出为 document）内容块。文本、已经是 Claude 格式的图片块及未知内容保持原样。

🚀 变更类型 / Type of change

• 🐛 Bug 修复 (Bug fix) - 请关联对应 Issue，避免将设计取舍、理解偏差或预期不一致直接归类为 bug
• ✨ 新功能 (New feature) - 重大特性建议先通过 Issue 沟通
• ⚡ 性能优化 / 重构 (Refactor)
• 📝 文档更新 (Documentation)

🔗 关联任务 / Related Issue

• Closes OpenAI image_url blocks are not converted inside Claude tool_result content #6260

✅ 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。PR fix: preserve images in Claude tool_result when converting to OpenAI chat completions #4873 处理的是相反的 Claude → OpenAI 转换方向。
• 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

go test ./service/relayconvert/internal/oai_chat
ok  github.com/QuantumNous/new-api/service/relayconvert/internal/oai_chat

go test ./service/relayconvert/...
ok  github.com/QuantumNous/new-api/service/relayconvert
ok  github.com/QuantumNous/new-api/service/relayconvert/internal/oai_chat
ok  github.com/QuantumNous/new-api/service/relayconvert/internal/oai_responses

新增回归测试验证：

• tool_result.content 中的 OpenAI image_url 会序列化为 Claude image/source，最终请求不再包含 image_url。
• 文本、已有 Claude 图片块和未知内容保持不变。

Summary by CodeRabbit

• New Features

  • Improved compatibility when sending OpenAI tool results containing images or PDFs to Claude.
  • Media content is converted into Claude-compatible formats with the correct type and embedded data.
  • Non-media tool content remains unchanged.

• Bug Fixes

  • Conversion errors for invalid media references are now surfaced instead of producing incomplete requests.

[coderabbitai]

Walkthrough

Tool-result content conversion now resolves OpenAI image_url items into Claude image or document media entries, while preserving non-image content. The Claude request converter applies the result in both tool-result message paths and adds resolver-backed tests.

Changes

Tool result media conversion

Layer / File(s)	Summary
Resolve tool-result image content service/relayconvert/internal/oai_chat/to_claude_messages_req.go	Adds conversion of resolvable image_url content into Claude media messages with base64 data and MIME-based media types.
Apply conversion to Claude tool results service/relayconvert/internal/oai_chat/to_claude_messages_req.go, service/relayconvert/internal/oai_chat/to_claude_messages_req_test.go	Uses converted content for merged and newly appended tool results, and tests image conversion plus preservation of non-image content.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant OpenAIRequest
  participant ClaudeConverter
  participant MediaResolver
  participant ClaudeToolResult
  OpenAIRequest->>ClaudeConverter: provide tool-result image_url content
  ClaudeConverter->>MediaResolver: resolve source and MIME type
  MediaResolver-->>ClaudeConverter: return base64 data
  ClaudeConverter->>ClaudeToolResult: set image or document media content

Loading

Possibly related issues

• OpenAI image_url blocks are not converted inside Claude tool_result content #6260 — Addresses the reported image_url conversion gap in Claude tool_result content.

Suggested reviewers: seefs001

Poem

A rabbit found a picture bright,
And wrapped it up for Claude just right.
Base64 carrots, MIME hay,
Non-images stayed along the way.
Tool results now hop in flight!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: converting OpenAI tool result images for Claude.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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