fix: keep streaming message ids consistent with memory by emitting `m…

[omeraplak]

…essageId`

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://voltagent.dev/docs/community/contributing/#commit-convention

Bugs / Features

• Related issue(s) linked
• Tests for the changes have been added
• Docs have been added / updated
• Changesets have been added https://voltagent.dev/docs/community/contributing/#creating-a-changeset

What is the current behavior?

What is the new behavior?

fixes (issue)

• [FEAT] In the streaming generation mode, the id in the output data VoltAgentTextStreamPart should be consistent with the message_id in the voltagent_memory_messages table #1021

Notes for reviewers

---

Summary by cubic

Ensures streaming message IDs stay consistent with memory by emitting messageId on start/start-step parts and using it for UI stream mapping. Fixes #1021 to prevent mismatched messages during live updates.

• Bug Fixes
  • Core agent adds response messageId to start/start-step stream parts (text-part ids unchanged).
  • AG UI tracks current messageId and applies it to text-delta events for correct message mapping.
  • Workflow stream includes messageId in metadata; types, docs, and tests updated.

^{Written for commit 259d207. Summary will update on new commits.}

Summary by CodeRabbit

• Bug Fixes

  • Enhanced message ID propagation in streaming responses; messageId now properly emitted on start/step chunks to enable improved UI stream mapping while maintaining text element IDs intact.

• Documentation

  • Updated API documentation and type definitions to reflect new messageId field support in streaming types.

[changeset-bot]

🦋 Changeset detected

Latest commit: 259d207

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@voltagent/ag-ui	Patch
@voltagent/core	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR introduces messageId propagation through the streaming response pipeline. It adds an optional messageId field to stream parts, creates a helper to inject messageId into start/start-step chunks, applies this in the agent's streamText path, and updates the UI adapter to use this ID for text-delta mapping while preserving text-part IDs.

Changes

Cohort / File(s)	Summary
Streaming type and metadata infrastructure packages/core/src/agent/subagent/types.ts, packages/core/src/workflow/stream.ts	Adds optional messageId field to VoltAgentTextStreamPart type and propagates messageId from stream parts into metadata alongside existing fields.
Agent streaming logic packages/core/src/agent/agent.ts	Introduces applyResponseMessageIdToStream helper that wraps streams to inject responseMessageId into start/start-step parts and applies this transformation in the streamText path.
UI adapter packages/ag-ui/src/voltagent-agent.ts	Updates to track currentMessageId from start/start-step chunks and derive messageId for text-delta parts using part.messageId ?? fallbackMessageId.
Tests and changelog .changeset/quiet-rockets-work.md, packages/core/src/agent/agent.spec.ts	Adds changeset documenting patch bumps for @voltagent/ag-ui and @voltagent/core and updates stream test to yield initial start event with messageId validation.
Documentation website/docs/agents/message-types.md, website/docs/api/streaming.md	Documents optional messageId field in VoltAgentTextStreamPart type and updates streaming comment to include start event type.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• fix: validate UI/response messages and keep streaming response messag… #1016: Modifies streaming response messageId wiring in agent stream code with similar messageId propagation patterns.

Poem

🐰 Hops through the stream with pride,
A messageId along for the ride,
From start to text, the ID flows true,
Mapping UI chunks, old and new! 🎯

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main change: ensuring streaming message IDs are consistent by emitting messageId, which aligns with the changeset and code modifications across multiple packages.
Description check	✅ Passed	The description includes all required sections from the template with substantive content: checklist completion, related issue linkage, test and documentation updates, changeset creation, and a detailed technical summary of the fix.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/message-id-streaming

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[cubic-dev-ai]

No issues found across 8 files