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frontend-debugging

Testing & Quality
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Systematic 10-phase debugging procedure for SvelteKit 2 + Svelte 5 frontend issues. Use when components fail to render, routing breaks, runes throw errors, or Encore client calls fail.

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Source SKILL.md: https://github.com/majiayu000/claude-skill-registry/blob/HEAD/skills/data/frontend-debugging/SKILL.md

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Frontend Debugging Skill

Purpose: Systematic 10-phase debugging procedure for SvelteKit 2 + Svelte 5 frontend issues.

When to Use

  • Component rendering issues
  • Routing problems
  • Svelte 5 runes errors ($state, $derived, $effect)
  • API client failures
  • Build or type errors

10-Phase Debugging Process

Phase 1: Health Check

task frontend:dev
# Check browser console

Phase 2: Type Safety

task frontend:typecheck
task frontend:lint

Phase 3: Encore Client Sync

task founder:workflows:regen-client
# Verify ~encore/clients imports

Phase 4: Svelte 5 Runes

  • Check proper rune usage and declaration
  • $state, $derived, $bindable, $props that you mutate must use let (never const)
  • $bindable requires {value} with oninput instead of bind:value
  • $effect for side effects only (no async return)

Phase 5: Routing

  • Verify +page.svelte structure
  • Check +layout.svelte hierarchy
  • Review load functions

Phase 6: API Calls

  • Always use Encore generated client
  • Never manual fetch() calls
  • Full type safety guaranteed

Phase 7: SSR/CSR Issues

  • Check server vs browser context
  • Verify browser checks when needed

Phase 8: Component Isolation

  • Test component in isolation
  • Check props/slots/events

Phase 9: Build Testing

task frontend:build
# Test production build

Phase 10: Browser DevTools

  • Use Svelte DevTools extension
  • Check component state/props
  • Review network requests

Reference Library

  • references/svelte5-runes-debugging.md – Deep dive on rune errors (const vs let, $bindable, diagnostics workflow)
  • references/common-issues.md – Expanded checklist for routing, SSR hydration, Encore client sync, and fast-fail signals
  • frontend-development_skill – Source of truth for runes, Skeleton UI patterns, and API integration standards
  • e2e-testing_skill – Playwright regression workflow when UI issues require end-to-end verification