fix: Assistant side panel open without blocking calls (no-changelog)

[mike12345567]

Summary

With the addition of the empty state to the builder side panel the opening of the panel had to be blocking. Since we load the messages when the panel opens we needed to know if there were messages to decide whether or not to show the empty state. This did however mean that the opening of the panel was blocking and could lead to some lag, it felt somewhat unpleasant.

To solve this, we now have a call to check if there are any messages currently for a workflow (endpoint POST /sessions/metadata) that occurs when the canvas/workflow loads. This means that we can open the panel immediately as we know whether or not we need to open the empty state already - messages can load in once they are available.

Ticket: https://linear.app/n8n/issue/AI-1525/t2w-add-loading-state-to-builder-side-panel

Review / Merge checklist

• PR title and summary are descriptive. (conventions)
• Docs updated or follow-up ticket created.
• Tests included.
• PR Labeled with release/backport (if the PR is an urgent fix that needs to be backported)

[bundlemon]

BundleMon

Files added (2)

Status	Path	Size	Limits
✅	WASM Dependencies tree-sitter-bash.wasm	+181.26KB	-
✅	WASM Dependencies tree-sitter.wasm	+74.47KB	-

Total files change +255.73KB

Groups added (2)

Status	Path	Size	Limits
✅	**/*.js	+5.76MB	-
✅	**/*.css	+200.63KB	-

Final result: ✅

View report in BundleMon website ➡️

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Current branch size history

[cubic-dev-ai]

1 issue found across 9 files

Prompt for AI agents (all 1 issues)

Understand the root cause of the following 1 issues and fix them.


<file name="packages/frontend/editor-ui/src/api/ai.ts">

<violation number="1" location="packages/frontend/editor-ui/src/api/ai.ts:122">
Rule violated: **Prefer Typeguards over Type casting**

Replace the new `as IDataObject` assertion on the request payload with a type annotation or `satisfies`-based check to comply with the &quot;Prefer Typeguards over Type casting&quot; guideline.</violation>
</file>

_{React with 👍 or 👎 to teach cubic. Mention @cubic-dev-ai to give feedback, ask questions, or re-run the review.}

[codecov]

Codecov Report

❌ Patch coverage is 45.71429% with 38 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../editor-ui/src/features/assistant/builder.store.ts	54.54%	15 Missing ⚠️
packages/frontend/editor-ui/src/api/ai.ts	22.22%	14 Missing ⚠️
...es/cli/src/services/ai-workflow-builder.service.ts	0.00%	5 Missing ⚠️
...pes/src/dto/ai/ai-session-metadata-response.dto.ts	0.00%	3 Missing ⚠️
packages/@n8n/api-types/src/dto/index.ts	0.00%	1 Missing ⚠️

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