Terminal-Universe reconstructs executable environments from agent trajectories instead of generating them.

Terminal agents have produced trajectories at scale while realistic executable environments stay scarce, and environments are what post-training needs, since each can be re-queried into many verifiable tasks while a trajectory is one frozen demonstration. The insight: a trajectory's tool-execution history exposes the structure and contents of the environment it ran in, so replaying recorded file operations restores each file to its pre-modification state, yielding a partial workspace a completion agent fills in. It scales along breadth, mining directional dependency relations between environments for cross-workspace queries, and depth, extending single-turn queries into longer interactions. Top paper on Hugging Face Daily Papers at 115 upvotes. arXiv 2609.04148