fix(ai): preserve providerMetadata through client-side UIMessage pipeline

[houmark]

Summary

PR #401 added providerMetadata to ToolCall and ToolCallStartEvent and wired it through the server-side ToolCallManager. However, the client-side pipeline (StreamProcessor → UIMessage → ModelMessage) drops providerMetadata entirely, breaking Gemini 3+ thinking models on multi-turn tool calls.

This PR completes the round-trip by carrying providerMetadata through every step of the client-side pipeline.

Fixes #403 (follow-up to #216, #401)

Changes (5 files, 26 lines added)

File	Change
types.ts	Add optional providerMetadata to ToolCallPart interface
stream/types.ts	Add optional providerMetadata to InternalToolCallState
stream/message-updaters.ts	Accept and carry forward providerMetadata in updateToolCallPart()
stream/processor.ts	Pass chunk.providerMetadata into InternalToolCallState and updateToolCallPart() in handleToolCallStartEvent(); include it in getCompletedToolCalls()
messages.ts	Include providerMetadata on toolCalls in buildAssistantMessages() (UIMessage → ModelMessage); preserve it in modelMessageToUIMessage() (ModelMessage → UIMessage)

How it works

The data flow is now:

Gemini API response
  → GeminiTextAdapter.processStreamChunks() captures thoughtSignature
  → TOOL_CALL_START event with providerMetadata: { thoughtSignature }
  → StreamProcessor.handleToolCallStartEvent() stores on InternalToolCallState + ToolCallPart
  → UIMessage.parts[].providerMetadata preserved
  → uiMessageToModelMessages() → buildAssistantMessages() includes providerMetadata on toolCalls
  → ModelMessage.toolCalls[].providerMetadata
  → GeminiTextAdapter.formatMessages() reads toolCall.providerMetadata?.thoughtSignature
  → functionCall part includes thoughtSignature
  → Gemini API accepts ✅

Test plan

• Existing test from PR fix(ai-gemini): preserve thoughtSignature and fix tool call IDs for Gemini 3+ thinking models #401 (preserves thoughtSignature in functionCall parts when sending history back to Gemini) continues to pass (server-side path)
• TODO: Add test for the client-side path: process TOOL_CALL_START with providerMetadata through StreamProcessor, convert to ModelMessages via toModelMessages(), verify providerMetadata is present on toolCalls

Summary by CodeRabbit

• New Features
  • Tool calls now support optional provider-specific metadata that is preserved throughout their complete lifecycle during streaming and message processing.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 7b8f7417-fa49-4b77-9e5f-d33e6484cfcc

📥 Commits

Reviewing files that changed from the base of the PR and between a8a4465 and 60ea7ab.

📒 Files selected for processing (5)

• packages/typescript/ai/src/activities/chat/messages.ts
• packages/typescript/ai/src/activities/chat/stream/message-updaters.ts
• packages/typescript/ai/src/activities/chat/stream/processor.ts
• packages/typescript/ai/src/activities/chat/stream/types.ts
• packages/typescript/ai/src/types.ts

---

📝 Walkthrough

Walkthrough

This PR threads providerMetadata through the client-side UIMessage processing pipeline. The metadata is now preserved when StreamProcessor converts streamed tool-call chunks into UIMessage parts, and when UIMessages are converted back to ModelMessages for server submission. This ensures provider-specific metadata (e.g., Gemini's thoughtSignature) survives multi-turn conversations.

Changes

Cohort / File(s)	Summary
Type Definitions packages/typescript/ai/src/types.ts, packages/typescript/ai/src/activities/chat/stream/types.ts	Added optional providerMetadata?: Record<string, unknown> field to ToolCallPart and InternalToolCallState interfaces to carry provider-specific metadata through the tool-call lifecycle.
Stream Processing packages/typescript/ai/src/activities/chat/stream/processor.ts, packages/typescript/ai/src/activities/chat/stream/message-updaters.ts	Propagated providerMetadata from streamed tool-call chunks into internal state on creation and into UIMessage parts; updateToolCallPart() now accepts and preserves metadata with fallback to existing part's metadata.
Message Conversion packages/typescript/ai/src/activities/chat/messages.ts	Conditionally attached providerMetadata when converting assistant tool-call UI parts to ModelMessage tool calls and back, ensuring metadata survives round-trip conversions.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 Through streams and messages we hop,
providerMetadata won't drop!
From chunk to part to message bright,
Thoughtsignatures take flight.
Each turn preserves what came before,
The rabbit's pipeline evermore! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: preserving providerMetadata through the client-side UIMessage pipeline, which is the primary objective of the PR.
Description check	✅ Passed	The PR description is comprehensive and well-structured, covering summary, changes, data flow, and test plan. However, the linked template checklist items (Contributing guide, testing with pnpm, and changeset generation) are not mentioned.
Linked Issues check	✅ Passed	The PR directly addresses all five root causes identified in issue #403: adds providerMetadata to ToolCallPart and InternalToolCallState types [#403], updates updateToolCallPart() to accept and forward metadata [#403], passes chunk.providerMetadata in handleToolCallStartEvent() [#403], and includes providerMetadata in buildAssistantMessages() and modelMessageToUIMessage() [#403].
Out of Scope Changes check	✅ Passed	All five modified files directly address the root causes of issue #403 and fit the scope of preserving providerMetadata through the client-side UIMessage pipeline. No unrelated changes are present.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}