Cleaning up stale feature flags

This skill guides you through finding feature flags that are no longer serving a purpose and safely removing them.

When to use this skill

• The user asks to clean up, audit, or review their feature flags
• The user wants to find flags that are stale, unused, or fully rolled out
• The user asks "which feature flags can I remove?" or similar
• The user wants to reduce tech debt from old feature flags

What makes a flag stale

A feature flag is considered stale when it's no longer doing useful work. PostHog tracks this with two signals:

1. Usage-based staleness: The flag has last_called_at data, but hasn't been evaluated in 30+ days. This is the strongest signal — the SDKs are no longer checking this flag.
2. Configuration-based staleness: The flag has no usage data (last_called_at is null), is 30+ days old, and is 100% rolled out (boolean at 100% with no property filters, or a multivariate flag with one variant at 100%). A fully rolled out flag with no conditions is equivalent to a hardcoded value — it can be replaced by removing the flag check from code.

Disabled flags (active: false) are not considered stale — they were intentionally turned off and may be kept for reactivation.