custom-router-routing-safety

name	custom-router-routing-safety
description	Use when changing routing, classifier, fallback, guardrail, pinning, or inspect-mode behavior in CustomRouter. Enforces the repo’s routing safety checks and test coverage expectations.

CustomRouter Routing Safety

Use this skill for changes touching:

• packages/core
• apps/web/src/lib/routing
• apps/web/src/features/routing
• request routing, classifier selection, fallback ordering, guardrails, or thread pins

Checklist

1. Preserve external API behavior.

   • /api/v1/chat/completions
   • /api/v1/responses
   • /api/v1/completions
   • /api/v1/router/inspect

2. Check all routing modes.

   • passthrough explicit model
   • routed request with classifier
   • classifier failure with fallback
   • classifier failure without fallback
   • dry-run inspect path

3. Check gateway and credential paths.

   • missing gateway
   • undecryptable gateway key
   • dedicated classifier key/base URL mismatch
   • classifier resolved through gateway ownership

4. Check thread behavior.

   • new thread
   • continuation pin reuse
   • force-route bypass
   • invalid pin after catalog changes

5. Check degraded behavior.

   • primary upstream failure
   • fallback selected after failure
   • guardrail-disabled models still leave one attempt

Validation

• Run:
  • npm run test -w @custom-router/core
  • npm run test -w @custom-router/web
  • npm run typecheck
• Prefer adding focused tests beside the extracted routing modules before changing broad end-to-end tests.