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Run npx skillmds@latest add qwikdev/qwik in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

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This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

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qwikdev (@qwikdev) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Qwik by qwikdev — Agent Skill

Name: Qwik
Author: qwikdev

Qwik

Workflow and pitfall checklist for Qwik core development (packages/qwik). Use when the user mentions Qwik, packages/qwik, Signal/AsyncSignalImpl, reactive-primitives, serialization/hydration (serialize/inflate), or cursor queue; it enforces running unit tests immediately after any implementation change, following signal/async-signal patterns, and running build/E2E/API validations before finishing.

qwikdev a4fead2 2 files · 28.9 KB Updated Sep 17, 2026

File contents

Qwik Core Development Guide (Skill)

Scope

Only for the Qwik core package: packages/qwik (especially src/core/**, reactive-primitives/**).

Mandatory workflow (must do)

0. Run tests immediately after any implementation change

After changing any implementation file, immediately run the relevant unit tests (don’t wait for CI, don’t wait to be asked):

pnpm vitest run <test-file-path>

Typical example (signals):

pnpm vitest run packages/qwik/src/core/reactive-primitives/impl/signal.unit.tsx

If tests fail, fix and re-run until they pass. Only then proceed with anything else (docs/refactors/cleanup).

Implementation essentials (high-signal rules)

Constructor parameter plumbing: when adding params to signal/async-signal constructors, keep parent calls and parameter order stable; extract options in factories (e.g. signal-api.ts) before passing into constructors.
AsyncSignal promise branches: .then() and .catch() must be symmetric (same side-effects / scheduling). Errors should not “stop” polling.
invalidate cleanup order: clear timeouts/resources first, then clear cached data and call super.invalidate() to avoid leaks and test interference.
SSR vs browser: guard browser APIs (setTimeout, etc.) with isBrowser; still persist configuration on the instance for hydration.
Subscriber checks: async signals may have separate subscribers for .value, .loading, and .error; any “has subscribers” logic must consider all three sets.
Serialization/hydration alignment: when adding new serializable fields, array positions in serialize.ts and inflate.ts must match exactly.

Testing conventions (high-signal rules)

Prefer $() for QRLs; avoid manually constructing QRLs (e.g. inlinedQrl()).
In $() tests that need mutable state, use object refs (e.g. { count: 0 }). Don’t capture and mutate outer-scope primitives (can trigger “Assignment to constant variable”).
First computation may “throw a promise” to trigger suspense behavior; in tests, use helpers like retryOnPromise() / withContainer() around first reads/creation.

Required validations before finishing

When the task is complete / ready to ship (especially core changes), run as appropriate:

pnpm build --qwik --qwikrouter --dev
pnpm run test.e2e.chromium
pnpm api.update

Detailed reference

For deeper patterns, examples, pitfall tables, and full checklists, read [AGENTS.md](AGENTS.md) in the same folder.

---name: qwikdescription: Workflow and pitfall checklist for Qwik core development (packages/qwik). Use when the user mentions Qwik, packages/qwik, Signal/AsyncSignalImpl, reactive-primitives, serialization/hydration (serialize/inflate), or cursor queue; it enforces running unit tests immediately after any implementation change, following signal/async-signal patterns, and running build/E2E/API validations before finishing.---# Qwik Core Development Guide (Skill)## Scope- Only for the Qwik core package: `packages/qwik` (especially `src/core/**`, `reactive-primitives/**`).## Mandatory workflow (must do)### 0. Run tests immediately after any implementation change- After changing any implementation file, **immediately** run the relevant unit tests (don’t wait for CI, don’t wait to be asked):```bashpnpm vitest run <test-file-path>```- Typical example (signals):```bashpnpm vitest run packages/qwik/src/core/reactive-primitives/impl/signal.unit.tsx```- If tests fail, fix and re-run until they pass. Only then proceed with anything else (docs/refactors/cleanup).## Implementation essentials (high-signal rules)- **Constructor parameter plumbing**: when adding params to signal/async-signal constructors, keep parent calls and parameter order stable; extract options in factories (e.g. `signal-api.ts`) before passing into constructors.- **AsyncSignal promise branches**: `.then()` and `.catch()` must be symmetric (same side-effects / scheduling). Errors should not “stop” polling.- **invalidate cleanup order**: clear timeouts/resources first, then clear cached data and call `super.invalidate()` to avoid leaks and test interference.- **SSR vs browser**: guard browser APIs (`setTimeout`, etc.) with `isBrowser`; still persist configuration on the instance for hydration.- **Subscriber checks**: async signals may have separate subscribers for `.value`, `.loading`, and `.error`; any “has subscribers” logic must consider all three sets.- **Serialization/hydration alignment**: when adding new serializable fields, array positions in `serialize.ts` and `inflate.ts` must match exactly.## Testing conventions (high-signal rules)- Prefer `$()` for QRLs; avoid manually constructing QRLs (e.g. `inlinedQrl()`).- In `$()` tests that need mutable state, use object refs (e.g. `{ count: 0 }`). Don’t capture and mutate outer-scope primitives (can trigger “Assignment to constant variable”).- First computation may “throw a promise” to trigger suspense behavior; in tests, use helpers like `retryOnPromise()` / `withContainer()` around first reads/creation.## Required validations before finishingWhen the task is complete / ready to ship (especially core changes), run as appropriate:```bashpnpm build --qwik --qwikrouter --devpnpm run test.e2e.chromiumpnpm api.update```## Detailed reference- For deeper patterns, examples, pitfall tables, and full checklists, read `[AGENTS.md](AGENTS.md)` in the same folder.

Frequently asked questions