Muscle-Mem, a behavior cache for AI agents
Hi HN! Erik here from Pig.dev, and today I'd like to share a new project we've just open sourced: Muscle Mem is an SDK that records your agent's tool-calling patterns as it solves tasks, and will deterministically replay those learned trajectories whenever the task is encountered again, falling back to agent mode if edge cases are detected. Like a JIT compiler, for behaviors. At Pig, we built computer-use agents for automating legacy Windows applications (healthcare, lending, manufacturing, etc). A recurring theme we ran into was that businesses already had RPA (pure-software scripts), and…
Muscle-Mem, a behavior cache for AI agents launched on May 14, 2025 with 226 votes, #136 of 7,905 launches that month and more than 95% of that year's launches. The site was still online in September 2026, 1 year on.
In plain words
Muscle-Mem is an open-source SDK that records how AI agents solve tasks by capturing their tool-calling patterns, then replays these learned behaviors deterministically when the same task appears again. If edge cases are detected, it automatically switches back to agent mode. Built for developers automating business processes and legacy applications, it combines the efficiency of traditional automation scripts with the flexibility of AI agents to handle unexpected situations.
written from the facts on this page · September 2026
From the sources
A cache for AI agents to learn and replay complex behaviors. - pig-dot-dev/muscle-mem
It is a Python SDK that records your agent's tool-calling patterns as it solves tasks, and will deterministically replay those learned trajectories whenever the task is encountered again, falling back to agent mode if edge cases are detected. The goal of muscle-mem is to get LLMs out of the hotpath for repetitive tasks, increasing speed, reducing variability, and eliminating token costs for the many cases that could have just been a script . You implement your agent however you want, and then plug it into muscle-mem 's engine. To add safe tool reuse to your agent, the critical question is cache validation. Ask yourself: For each tool we give to our agent, what features in the environment…from github.com
In the maker’s words, at launch
Hi HN! Erik here from Pig.dev, and today I'd like to share a new project we've just open sourced: Muscle Mem is an SDK that records your agent's tool-calling patterns as it solves tasks, and will deterministically replay those learned trajectories whenever the task is encountered again, falling back to agent mode if…
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