Meet Shepherd: An Open-Source Python Substrate That Lets Meta-Agents Fork, Replay, and Revert Any Agent Run

Long agent runs accumulate state that no transcript records — edited files, a live dev server, installed packages, a warm prompt cache. When an agent misreads a traceback at step 10 and rewrites a correct file, patching forward burns tokens and restarting re-pays every call.

Researchers at Northeastern University and Stanford University released Shepherd, an MIT-licensed Python runtime substrate that records every agent-environment interaction as a typed event in a Git-like execution trace.