---

name: pattern-debug description: Debug pattern errors systematically user-invocable: false

Debug Pattern

Use Skill("ct") for ct CLI documentation if debugging deployment or charm issues.

Read First

• docs/development/debugging/workflow.md - 5-step debugging process
• docs/development/debugging/README.md - Error reference matrix

Process

1. Check TypeScript errors:

   Copydeno task ct check pattern.tsx --no-run
   

2. Match error to documentation:

   • Read the error message carefully
   • Check docs/development/debugging/README.md for matching errors

3. Check gotchas:

   • docs/development/debugging/gotchas/handler-inside-pattern.md
   • docs/development/debugging/gotchas/filter-map-find-not-a-function.md
   • docs/development/debugging/gotchas/onclick-inside-computed.md

4. Simplify to minimal reproduction:

   • Comment out code until error disappears
   • Add back piece by piece to find root cause

5. Fix and verify:

   • Apply fix
   • Run tests to confirm

Common Issues

Handler defined inside pattern body:

• Move handler() to module scope
• Only bind it inside pattern: onClick={myHandler({ state })}

Type errors with Writable/Default:

• Check if field needs write access → use Writable<>
• Check if field could be undefined → use Default<T, value>

Action not triggering:

• Ensure Output type includes action as Stream
• Use .send() not .get() to trigger

Done When

• Root cause identified
• Error fixed
• Tests pass again