[youdie006]

Closes #8237.

Documents useConstant, which previously existed only in the auto-generated API reference with no hand-written guide.

• Adds a ## useConstant() section to the State docs page (core/state/index.mdx), mirroring the sibling useSignal / useStore / useComputed$ sections: an intro, a runnable CodeSandbox example, and a note distinguishing it from useSignal / useComputed$ (a value computed once and never re-run).
• Adds the live demo the example points at (demo/state/use-constant/index.tsx), matching the sibling demos.

Content is grounded in the JSDoc from the issue and the source signature (useConstant in packages/qwik/src/core/use/use-signal.ts).

Note: the source still carries the @deprecated This is a technology preview tag on useConstant, so the generated API reference currently shows an "obsolete" warning. I documented it as a usable hook per the V2 intent described in this issue — happy to adjust if you'd prefer to reconcile the deprecation status separately.

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AI disclosure: this PR was drafted with Claude Code (AI-assisted). The content is grounded in the issue's JSDoc and the source, and validated structurally.

[changeset-bot]

🦋 Changeset detected

Latest commit: eed589f

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

This PR includes changesets to release 4 packages

Name	Type
@builder.io/qwik	Patch
@builder.io/qwik-city	Patch
eslint-plugin-qwik	Patch
create-qwik	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

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[maiieul]

LGTM 👍 I think we can remove the flag for V2 indeed.

[wmertens]

Thank you! Small change please:

[youdie006]

Done, thanks for the review!

• Changed the guard to val !== undefined, so a null result is now retained and only an undefined result re-runs the factory (with an explanatory comment + a JSDoc note).
• Documented in the guide that a factory returning undefined is re-run each render; defined values (including null) are retained.
• Added the note in the demo that componentId stays the same for the component's lifetime.
• Added a changeset (@builder.io/qwik patch) and a use-signal.unit.tsx test proving the null-is-retained / undefined-re-runs behavior (red on the old guard, green on the new one), and ran api.update to sync the generated API docs.

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Drafted-by: Claude Code (Opus 4.8) (no human review before posting)

[youdie006]

@wmertens gentle nudge on this one - I pushed the val !== undefined guard change (so null is retained and only undefined re-runs), the docs + demo updates, a changeset, and a use-signal.unit.tsx test a few days ago. Whenever you have a moment, happy to have another look. Thanks!

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Drafted-by: Claude Code (Opus 4.8) (no human review before posting)

[wmertens]

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@builder.io/qwik@8827

npm i https://pkg.pr.new/@builder.io/qwik-city@8827

npm i https://pkg.pr.new/eslint-plugin-qwik@8827

npm i https://pkg.pr.new/create-qwik@8827

commit: eed589f