Dev Feature Flag | Skills Pool
Dev Feature Flag Implement a feature flag system with percentage rollout, user targeting, and cleanup process. Triggers: 'feature flag', 'feature toggle', 'flag system', 'gradual rollout', 'canary release', 'dark launch'.
knofler 0 Sterne 04.04.2026 Feature Flag System Playbook
When to Use
Rolling out a new feature gradually to reduce risk
A/B testing different implementations
Enabling features per environment (staging vs production)
Giving specific users early access to unreleased features
Need to quickly disable a feature without redeployment
Prerequisites
Storage backend decided: environment variables (simple), config file, database, or external service
Feature flag naming convention agreed (e.g., ENABLE_NEW_DASHBOARD)
Application has middleware or initialization where flags can be loaded
Playbook
1. Define Flag Storage
Create src/lib/featureFlags.ts as the central flag module
Schnellinstallation
Dev Feature Flag npx skillvault add knofler/knofler-api-job-hunter-ai-skills-dev-feature-flag-skill-md
Sterne 0
Aktualisiert 04.04.2026
Beruf Simple (env-based)
FF_
FF_NEW_DASHBOARD=true
Config-based : JSON file at config/feature-flags.json with flag definitions
DB-based : MongoDB collection featureFlags with flag documents
Flag schema: { name, enabled, rolloutPercentage, targetUsers, targetRoles, description, createdAt, expiresAt }
2. Implement Evaluation Logic
isEnabled(flagName, context?) — the core function:
Check if flag exists; return false for unknown flags (fail closed)
If enabled is false, return false immediately
If targetUsers array is set and user ID matches, return true
If targetRoles array is set and user role matches, return true
If rolloutPercentage is set: hash userId + flagName, mod 100, compare to percentage
Default: return the enabled boolean value
Hashing ensures consistent evaluation — same user always gets the same result
3. Create Middleware/Hook
Backend : Express middleware that loads flags and attaches to req.flags
Cache flag values for the duration of the request
Refresh flag cache every 60 seconds (not on every request)
Frontend : React hook useFeatureFlag(flagName) that:
Fetches flags from API endpoint GET /api/v1/feature-flags
Caches in React context, refreshes on window focus
Returns { enabled: boolean, loading: boolean }
4. Add Management Endpoint
GET /api/v1/feature-flags — list all flags (admin only)PUT /api/v1/feature-flags/:name — update flag settings (admin only)POST /api/v1/feature-flags — create new flag (admin only)Log all flag changes with who changed what and when
5. Implement Flag Usage Pattern
6. Define Cleanup Process
Set expiresAt on every flag (recommended: 90 days max)
Weekly review: flags past expiry should be removed
Cleanup steps: remove flag check, remove old code path, delete flag from storage
Track active flags in a table in state/STATE.md
Output
src/lib/featureFlags.ts — flag evaluation moduleFlag storage setup (env/config/DB)
Backend middleware and/or frontend React hook
Admin management endpoints
Flag cleanup documentation
Review Checklist 02
When to Use
Debugging
Node Connect Diagnose OpenClaw node connection and pairing failures for Android, iOS, and macOS companion apps. Use when QR/setup code/manual connect fails, local Wi-Fi works but VPS/tailnet does not, or errors mention pairing required, unauthorized, bootstrap token invalid or expired, gateway.bind, gateway.remote.url, Tailscale, or plugins.entries.device-pair.config.publicUrl.