Mark Zuckerberg's post on X, curated on eChai

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Mark Zuckerberg co-founded Facebook, now Meta, and is its chief executive. Muse Code is Meta's coding agent, worked from the terminal and built on Muse Spark 1.2, a coding model trained alongside the agent rather than wrapped around a general one. It keeps a repository of thousands of files in a 1M-token context window, splits a large job across sub-agents that each work in their own git worktree so parallel edits do not collide, and prints every sub-agent, tool call, steer and cancel to an event log. Muse Code is not new today: it opened in early beta on 5 August 2026, priced from $5 a month with $15 and $50 tiers above it, and a cheaper contributor tier in some countries in return for Meta training on your prompts and completions. What this post adds is that the beta is over.

Mark Zuckerberg 1 Sep 2026