fix(xl-ai): preserve error messages in ClientSideTransport stream by nperez0111 · Pull Request #2862 · TypeCellOS/BlockNote

nperez0111 · 2026-06-18T12:21:23Z

Summary

Fixes the AI SDK's toUIMessageStream() default behavior change that was silently replacing real error messages with a generic "An error occurred." string, and extracts the GitHub issue search instructions from AGENTS.md into a dedicated Claude Code skill.

Rationale

The Vercel AI SDK recently changed toUIMessageStream()'s default onError to return "An error occurred." instead of the actual error message, to prevent leaking server details to clients. Since ClientSideTransport runs entirely client-side, there is no server-to-client boundary and the original error message should be preserved. This was caught by the Fresh Install Tests CI job.

Changes

Pass an explicit onError callback to toUIMessageStream() in ClientSideTransport that surfaces the real error message
Extract GitHub issue search instructions from AGENTS.md into .claude/skills/github-issues/SKILL.md

Impact

Error messages from LLM API calls (e.g. rate limit errors) will now be surfaced to users correctly instead of being replaced with a generic message. No breaking changes.

Testing

Ran the errorHandling.test.ts test that validates 429 error message propagation — passes
Full test suite passes (873 tests in integration, 225 in xl-ai)

Checklist

Code follows the project's coding standards.
Unit tests covering the new feature have been added.
All existing tests pass.
The documentation has been updated to reflect the new feature

Summary by CodeRabbit

Bug Fixes
- Improved error message handling for streaming text operations, ensuring clearer error information when failures occur.

Move the "Issue Context" section out of AGENTS.md (which runs on every conversation) and into .claude/skills/github-issues/ so it can be invoked on demand instead.

The AI SDK changed toUIMessageStream()'s default onError to return a generic "An error occurred." instead of the real message (to prevent leaking server details). Since ClientSideTransport runs entirely client-side, explicitly pass onError to surface the original error.

vercel · 2026-06-18T12:21:29Z

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Project	Deployment	Actions	Updated (UTC)
blocknote	Ready	Preview	Jun 18, 2026 12:22pm
blocknote-website	Building	Preview	Jun 18, 2026 12:22pm

github-actions · 2026-06-18T12:23:21Z

PR Preview Action v1.8.1
🚀 View preview at https://TypeCellOS.github.io/BlockNote/pr-preview/pr-2862/
Built to branch `gh-pages` at 2026-06-18 12:32 UTC. Preview will be ready when the GitHub Pages deployment is complete.

coderabbitai · 2026-06-18T12:25:22Z

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Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 346d4444-56c6-4145-b295-02d17d7a9d38

📥 Commits

Reviewing files that changed from the base of the PR and between 27f156a and d72775a.

📒 Files selected for processing (3)

.claude/skills/github-issues/SKILL.md
AGENTS.md
packages/xl-ai/src/streamTool/vercelAiSdk/clientside/ClientSideTransport.ts

📝 Walkthrough

Walkthrough

Two unrelated changes: the GitHub issue-scanning instructions previously in AGENTS.md are extracted into a new dedicated Claude skill file at .claude/skills/github-issues/SKILL.md, and ClientSideTransport.streamText gains an explicit onError callback that normalizes streamed errors to strings.

Changes

GitHub Issue-Scanning Skill Migration

Layer / File(s)	Summary
GitHub issues skill definition and AGENTS.md cleanup `AGENTS.md`, `.claude/skills/github-issues/SKILL.md`	The "Issue Context" block is removed from `AGENTS.md` and recreated as a standalone skill with front-matter metadata, when-to-use guidance, and an ordered `gh` CLI procedure in the new `SKILL.md`.

ClientSideTransport Error Normalization

Layer / File(s)	Summary
`toUIMessageStream` onError handler `packages/xl-ai/src/streamTool/vercelAiSdk/clientside/ClientSideTransport.ts`	`toUIMessageStream` is now called with an `onError` callback that returns `error.message` for `Error` instances and `String(error)` for all other throwables, replacing the previous default (no explicit error handling).

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~4 minutes

Poem

🐇 Hippity-hop, I moved the rules,
From AGENTS to skills with proper tools.
A new SKILL.md now holds the way
To search for issues without delay!
And errors? Now strings — neat and clear,
A tidy little PR, my dear. ✨

✨ Finishing Touches

📝 Generate docstrings

Create stacked PR
Commit on current branch

🧪 Generate unit tests (beta)

Create PR with unit tests
Commit unit tests in branch feat/extract-github-search-skill

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nperez0111 added 2 commits June 18, 2026 13:28

refactor: extract GitHub issue search from AGENTS.md into a skill

4e1513e

Move the "Issue Context" section out of AGENTS.md (which runs on every conversation) and into .claude/skills/github-issues/ so it can be invoked on demand instead.

vercel Bot deployed to Preview – blocknote June 18, 2026 12:22 View deployment

nperez0111 merged commit ade62f2 into main Jun 18, 2026
13 of 14 checks passed

nperez0111 deleted the feat/extract-github-search-skill branch June 18, 2026 12:23

vercel Bot deployed to Preview – blocknote-website June 18, 2026 12:24 View deployment

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fix(xl-ai): preserve error messages in ClientSideTransport stream#2862

fix(xl-ai): preserve error messages in ClientSideTransport stream#2862
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nperez0111 commented Jun 18, 2026 •

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nperez0111 commented Jun 18, 2026 •

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