fix(ai-persistence): ignore empty TEXT_MESSAGE_START message ids so they are not stored

[kolaworld]

🎯 Changes

• Ignore empty TEXT_MESSAGE_START messageId values in persistence so they are not stored as the in-progress stream id.
• That leaves streamingMessageId unset, so a later TOOL_CALL_START can still apply parentMessageId.
• Regression: empty start id + parentMessageId: 'stream-assistant' + mid-stream crash with snapshotStreaming still persists id: 'stream-assistant'.

✅ Checklist

• I have followed the steps in the Contributing guide.
• I have tested this code locally with pnpm run test:pr.

🚀 Release Impact

• This change affects published code, and I have generated a changeset.
• This change is docs/CI/dev-only (no release).

Summary by CodeRabbit

• Bug Fixes

  • Fixed streaming persistence so empty text message IDs no longer overwrite the parent assistant message ID.
  • Preserved the correct assistant message association for tool calls and partial responses, including when a stream fails mid-response.

• Tests

  • Added regression coverage for persistence during interrupted streaming responses.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: fdced981-bede-40ac-964e-a8f95ceacc71

📥 Commits

Reviewing files that changed from the base of the PR and between 9a4124d and 269bbe4.

📒 Files selected for processing (3)

• .changeset/fix-empty-text-message-start-id.md
• packages/ai-persistence/src/middleware.ts
• packages/ai-persistence/tests/with-persistence.test.ts

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📝 Walkthrough

Walkthrough

The persistence middleware now ignores empty TEXT_MESSAGE_START message IDs. A regression test verifies that streaming snapshots retain the existing assistant message ID after tool calls and mid-stream failures. A patch changeset documents the fix.

Changes

Streaming persistence

Layer / File(s)	Summary
Preserve non-empty streaming message IDs packages/ai-persistence/src/middleware.ts, packages/ai-persistence/tests/with-persistence.test.ts, .changeset/fix-empty-text-message-start-id.md	The middleware updates the streaming message ID only when chunk.messageId is non-empty. The regression test covers tool-call linkage, partial assistant output, and mid-stream failure. The changeset documents the patch release.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 269bb

This change prevents empty streaming message IDs from being persisted, preserving subsequent parent-message handling without introducing a current-head merge-blocking risk.

Possibly related PRs

• TanStack/ai#1066: Preserves message IDs in an AI message conversion or persistence path.
• TanStack/ai#1101: Changes assistant stream message ID handling in middleware.ts.
• TanStack/ai#1116: Preserves assistant message IDs during streaming snapshot persistence.

Suggested reviewers: mikemikimike, alemtuzlak

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main persistence fix: ignoring empty TEXT_MESSAGE_START message IDs.
Description check	✅ Passed	The description includes the required changes, checklist, release impact, testing, and changeset information.
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.

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