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Using Memlab

Memlab is an E2E testing and analysis framework for finding JavaScript memory leaks.

Important Rule

NEVER read raw .heapsnapshot files directly. They are too large and will exceed context limits. Always use memlab commands to analyze them.

Analyzing Snapshots

You can use the take_memory_snapshot tool provided by the chrome-devtools-mcp extension to generate heap snapshots during an investigation. To find leaks, you generally need 3 snapshots:

  1. Baseline: Before the suspect action.
  2. Target: After the suspect action.
  3. Final: After reverting the suspect action (e.g., closing a modal, navigating away).

Once you have these 3 snapshots saved to disk, you can use memlab to find leaks:

npx memlab find-leaks --baseline <path-to-baseline> --target <path-to-target> --final <path-to-final>

You can also parse a single snapshot to find the largest objects or explore it individually:

npx memlab analyze snapshot --snapshot <path-to-snapshot>

Memlab will output the retainer traces for identified leaks. Use these traces to guide your search in the codebase.