Stale flag cleanup

Over time, feature flags accumulate in codebases. Flags that were fully rolled out, linked to completed experiments, or simply forgotten can clutter your code and make it harder to reason about. The VS Code extension uses AST-based scanning (via tree-sitter) to find stale flag references across your project and help you remove them safely.

Running a scan

Open the command palette and run PostHog: Scan for Stale Flags. The extension scans all JavaScript and TypeScript files in your workspace, building a tree of every feature flag reference it finds.

Results appear in the stale flags tree view in the sidebar, grouped by staleness reason.

Configuration

Two settings control how the scan behaves:

• posthog.staleFlagAgeDays (default: 30) — The minimum number of days a flag must have been fully rolled out before it's considered stale. Lower this if you want to catch flags sooner.
• posthog.staleFlagExcludePatterns — Glob patterns for files or directories to skip during scanning (e.g., ["**/test/**", "**/migrations/**"]). The extension already excludes node_modules and common build output directories.

Staleness categories

The scan classifies each flag into one of four categories:

Fully rolled out

The flag is set to 100% rollout for all users. The code path gated by this flag is always taken, so the flag check can be removed and the code kept.

Inactive

The flag has not been evaluated in the time period defined by posthog.staleFlagAgeDays. This suggests it's no longer being used in production.

Experiment complete

The flag is linked to an experiment that has concluded. The experiment results are in, and the flag check can be replaced with the winning variant's code path.

Not in PostHog

The flag key exists in your code but doesn't exist in your PostHog project. This could mean the flag was deleted from PostHog, was created in a different project, or is a typo.

Navigating stale flags

Click on any flag in the stale flags tree view to jump to its location in your codebase. If a flag is referenced in multiple files, the tree view shows each reference as a child node you can click individually.

Cleaning up a flag

To remove a single flag check:

1. Click the flag in the tree view (or place your cursor on the flag call in code)
2. Run PostHog: Clean Up Stale Flag from the command palette or context menu
3. The extension uses AST-based refactoring to:
   • Remove the isFeatureEnabled() or getFeatureFlag() check
   • Keep the code from the correct branch (the "enabled" path for fully rolled out flags, or the winning variant path for completed experiments)
   • Clean up any unused else branches or variable declarations

This is safer than a manual find-and-replace because the extension understands the code structure and preserves the correct code paths.

Batch cleanup

To clean up multiple stale flags at once:

1. Select multiple flags in the stale flags tree view
2. Run the cleanup action
3. Review the proposed changes before applying

This is useful when you have a large number of stale flags to remove after a cleanup sprint.