PostHog Feature Flags

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Why

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Setup

1. Add tooling-feature-flags-posthog to apps/backend/package.json (already present in the template).
2. Run make deps-install.
3. Configure production:

featureFlags: {
  client: FeatureFlagClientType.POSTHOG,
  cacheMs: 30_000,
  apiKey: process.env.POSTHOG_API_KEY,
  exposedFlags: ['new-dashboard'],
  settings: {
    host: 'https://us.i.posthog.com',
  },
},

4. Set POSTHOG_API_KEY (and optional POSTHOG_HOST) in the deployment environment.

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Evaluation context

• userId → distinct id (falls back to anonymous)
• organizationId, environment, and attributes → person properties

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Gotchas

• Multivariate flag values are exposed through getVariant() with enabled: true.
• Boolean false flags remain in the normalized cache with enabled: false.
• Shared cache TTL is controlled by cacheMs; request caching is always on for HTTP traffic.

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What’s next?

• Feature flags overview
• Local provider
• LaunchDarkly provider