fix: preserve anthropic assistant ids in tool-first streams

[shaked-frame]

Summary

• add parentMessageId to Anthropic TOOL_CALL_START chunks so tool-first streams bind to the eventual assistant message id immediately
• add an Anthropic adapter regression covering tool-first streams and asserting the tool call chunk references the same assistant message id as TEXT_MESSAGE_START
• add a stream processor regression showing tool-first flows with parentMessageId preserve a single assistant message instead of creating a temporary local id

fixes #477

Verification

• pnpm exec vitest run packages/typescript/ai/tests/stream-processor.test.ts
• pnpm test:lib -- --runInBand in packages/typescript/ai
  • the new stream-processor regression passed
  • the package command still hits existing workspace resolution issues (@tanstack/ai-event-client, examples/ts-svelte-chat/.svelte-kit/tsconfig.json)
• pnpm test:lib -- --runInBand in packages/typescript/ai-anthropic
  • blocked by an existing @tanstack/ai package-entry resolution issue before the adapter test file runs

Summary by CodeRabbit

Release Notes

• Bug Fixes
  • Fixed an issue where streaming tool calls would create temporary message IDs that changed mid-stream. Tool calls are now properly bound to their parent assistant messages, ensuring stable message IDs throughout streaming across all supported providers.

[coderabbitai]

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📝 Walkthrough

Walkthrough

This PR adds a changeset file documenting a fix for AG-UI stream handling. Tool call start events now include parentMessageId to bind them to the stable assistant message id, preventing temporary message creation and mid-stream id changes when tool calls arrive before text across all provider adapters.

Changes

Stream Stability Fix Release Notes

Layer / File(s)	Summary
Stream stability fix changelog .changeset/tool-first-parent-message-id.md	Changeset documenting the fix where TOOL_CALL_START events now carry parentMessageId tied to the per-stream assistant message id, preventing StreamProcessor from creating temporary messages that would later cause mid-stream id changes. The fix spans all adapters: Anthropic, OpenAI (Responses and Chat Completions), OpenRouter, Gemini (including experimental text-interactions), and Ollama.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Suggested reviewers

• tombeckenham
• AlemTuzlak

Poem

A bunny's stream now flows so true,
Tool calls bind to parent, tried and new,
No id remounts in mid-stream glow—
Stability fixed from head to toe! 🐰✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Description check	❓ Inconclusive	The description covers key aspects but lacks evidence of PR checklist completion and changeset generation verification, which the template requires.	Clarify whether the Contributing guide steps were followed and confirm changeset was created as required by the template checklist.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main fix: preserving Anthropic assistant IDs in tool-first streams, which is the primary objective of this changeset.
Linked Issues check	✅ Passed	The PR successfully addresses issue #477 by implementing parentMessageId on TOOL_CALL_START chunks, stabilizing assistant message IDs through tool-first streams as required.
Out of Scope Changes check	✅ Passed	All changes focus on fixing the tool-first stream ID stability issue in issue #477; the changeset entry documents the fix without introducing unrelated modifications.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[shaked-frame]

rebased and pushed after resolving conflicts

[tombeckenham]

Thanks for this. I fixed it in the rest of the adpaters as well.

[nx-cloud]

View your CI Pipeline Execution ↗ for commit b79fc03

Command	Status	Duration	Result
nx run-many --targets=build --exclude=examples/...	✅ Succeeded	1s	View ↗

---

☁️ Nx Cloud last updated this comment at 2026-06-10 07:34:57 UTC

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commit: b79fc03