fix(codex): filter unsupported DeepSeek V4 custom tools

[yuaiccc]

Summary

DeepSeek V4's Responses compatibility endpoint accepts the host's apply_patch custom tool but rejects every other Codex custom tool (notably exec), causing 400 errors. This adds a narrow sanitization transform that:

• Removes unsupported custom tool dialects (string form and object form) while keeping apply_patch
• Leaves ordinary function/MCP tool declarations untouched
• Resets tool_choice to auto when it references a removed custom tool
• Clears tools/tool_choice/parallel_tool_calls when all tools are filtered

Tests

Added removes unsupported DeepSeek V4 custom tools but retains apply_patch regression test covering exec string, exec custom object, apply_patch string/object, and function tools.

• pnpm --filter desktop typecheck
• pnpm test:unit:related (codexProxyHost tests)

Risk

Low: transform is gated on deepseek/deepseek-v4-pro and deepseek/deepseek-v4-flash model IDs only.

[greptile-apps]

Greptile Summary

Adds a DeepSeek V4-specific request transform that removes unsupported custom tools while preserving apply_patch and ordinary function tools.

• Resets tool selection when it references a filtered custom tool.
• Removes tool-related fields when filtering leaves no tools.
• Adds regression coverage and registers the transform before the existing provider compatibility transforms.

Confidence Score: 5/5

The PR appears safe to merge with no actionable correctness or security issues identified.

The transform is narrowly gated to the two DeepSeek V4 model IDs, preserves supported and ordinary function tools, repairs dangling tool selection, and is covered by a focused regression test.

Important Files Changed

Filename	Overview
apps/desktop/src/main/maker-host/codex-proxy-host.ts	Adds and registers the narrowly model-gated DeepSeek V4 custom-tool sanitizer; no actionable defect was established.
apps/desktop/src/main/maker-host/tests/codexProxyHost.test.ts	Updates transform-chain expectations and verifies filtering of string/object custom tools while retaining apply_patch and function tools.

_{Reviews (1): Last reviewed commit: "Merge remote-tracking branch 'origin/mai..." | Re-trigger Greptile}

[MagicLizi]

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