[LukasParke]

Description

OpenRouter returns a fourth reasoning detail type, reasoning.server_tool_call. It records a completed OpenRouter server-tool call (e.g. openrouter:fusion, openrouter:tool_search) so the call can be rehydrated on a later turn. The SDK's reasoning detail union only knew summary, encrypted and text, so the unknown-type fallback silently dropped these entries at parse time. They never reached providerMetadata and were never sent back, which breaks server-tool continuity across turns.

Backend shape (OpenRouterTeam/openrouter-web)

• packages/llm-interfaces/schemas/response/reasoning-schemas/index.ts: ReasoningDetailType.ServerToolCall = 'reasoning.server_tool_call' with tool_name: string, tool_call_id?: string | null, arguments: string, result: string, plus the common id/format/index fields. It is part of ReasoningDetailUnionSchema.
• packages/llm-interfaces/reasonings/duplicate-tracker.ts: dedupes it by tool_call_id, falling back to ${tool_name}:${arguments}.
• Returned to clients: packages/router/skins/openai-chat-completions/from-internal-stream/handlers.ts (buildRoundTripReasoningDetail / handleGenerationServerToolCall) emits it in delta.reasoning_details as a discrete, non-mergeable entry. It is built by packages/router/plugins/server-tools/server-tool-reasoning-detail.ts.
• Accepted on input: packages/router/plugins/normalize-request/reconstruct-server-tool-messages-openai.ts rehydrates echoed reasoning.server_tool_call details into assistant tool_calls and tool messages.
• Docs: the public OpenAPI spec (/openapi.json) includes ReasoningDetailServerToolCall. The reasoning-tokens guide doesn't mention it yet.

Changes

• src/schemas/reasoning-details.ts: added ReasoningDetailType.ServerToolCall and ReasoningDetailServerToolCallSchema to the union. The response, stream delta and providerOptions schemas all build on it, so all three now accept the type.
• src/utils/reasoning-details-duplicate-tracker.ts: uses the same canonical key as the backend.
• src/chat/index.ts: handles the new type in the exhaustive switches. It produces no visible reasoning part or delta, and streaming pushes it as a discrete entry, never merged with text or summary.
• The converter needed no change. It forwards non-text details unchanged once they parse.

Tests (all fail on origin/main, pass here)

• src/chat/server-tool-call-reasoning.test.ts: parse (doGenerate), stream accumulation (doStream finish metadata keeps text merged and the server tool call separate), and a streamText two-turn round trip that checks the second request's reasoning_details.
• src/utils/reasoning-details-duplicate-tracker.test.ts: dedup by tool_call_id and by tool_name:arguments.

Overlap with #593

#593 changes src/schemas/format.ts. This PR doesn't touch that file. format stays optional on the new schema, which matches the backend (server-tool details are emitted without a format).

Checklist

• I have run pnpm stylecheck and pnpm typecheck
• I have run pnpm test and all tests pass
• I have added tests for my changes (if applicable)
• I have updated documentation (if applicable)

Changeset

• I have run pnpm changeset to create a changeset file

🤖 Generated with Claude Code

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.