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Meta · Coding harness

Muse Code: Meta's beta terminal agent with persistent background workers

Muse Code is a macOS/Linux terminal agent built around persistent async workers, event-log replay, and a model co-trained for the harness.

Meta

Released August 5, 2026

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What changed

  • Background agents remain active across a session instead of being recreated for every task.
  • A local append-only event log is designed to make long-running work restart-safe.
  • The beta includes plan, grill, and goal workflows for breaking down difficult repository tasks.

Best fit

  • Terminal-native engineers
  • Long-running multi-step tasks
  • Teams testing multi-agent workflows

What to be careful about

  • The beta requires a Meta account and works on macOS and Linux.
  • Parallelism and model quality need independent testing on real repositories.
Dataset snapshot: Muse Code is also represented in the checked comparison dataset. Prices and benchmark figures carry their own field dates.