Blog · the spec, written for readers

How an environment is created, and how each framework runs on it.

Every post ends with what ships today and what the post commits us to build. If the product disagrees with a post, the product is wrong or the post gets a dated edit.

00Creating an environment on denvConnect GitHub and a target. Describe the environment as a compose file. denv deploys it in phases, snapshots it, and lets you fork, replay, roll back, and hand it to any framework.2026-10-1001Harbor on denvRun any Harbor dataset with denv as the environment backend, import Harbor tasks as denv projects, and export denv environments as Harbor task directories.2026-10-1002Inspect on denvUse denv as an Inspect sandbox with sandbox="denv". Samples get a forked environment instead of a fresh container, and the eval log records what the environment was.2026-10-1003OpenEnv on denvRun OpenEnv environment images on denv with DenvProvider, fork them mid-episode, and export a denv version as an OpenEnv environment so every trainer that speaks OpenEnv can use it.2026-10-1004verifiers (Prime Intellect) on denvTrain with prime-rl against denv environments two ways — through verifiers' Harbor taskset with denv as the Harbor backend, or with a denv sandbox inside a verifiers environment.2026-10-1005HUD on denvRun HUD environments on denv as a runtime, give HUD's MCP-driven agents a forkable world, and move HUD datasets between HUD and Harbor without leaving denv.2026-10-1006Karotte on denvKarotte's five protections, now with versions, snapshots, forks and multi-service worlds. Run Karotte environments inside denv and import them as denv projects.2026-10-1007Training against denv environmentsSkyRL, verl, rLLM, prime-rl, TRL and Tinker already read Harbor and OpenEnv. denv builds and runs the environment; the trainer reaches it through those two formats, and rollouts fork instead of rebuild.2026-10-10