Mechs

A mech is a persistent agent that belongs to one workspace. Compute exists only while one of its runs is active; between runs, a mech is its saved checkpoint.

Names

Names contain lowercase letters, numbers, _, and -. They start with a letter or number and are at most 64 characters. A name is unique within its workspace.

Profile and settings

A mech's profile is fixed when it is created: the model and the harness that drives it. The current harness is Codex 0.156.0. Changing the model is rejected; create another mech instead.

Settings can change: instructions and reasoningEffort. Update the defaults with PATCH /v1/mechs/{id}, or override them for one run in the run request. Changing defaults never alters a run that has already been accepted.

GPT-6 Luna accepts none, low, medium, high, xhigh, and max effort. An unspecified effort means medium.

Checkpoints

A checkpoint holds the mech's conversation and its files, up to 16 MiB and 10,000 files. A run that completes saves a new checkpoint before it reports completed. A run that fails or is cancelled keeps the previous checkpoint, so the next run starts from the last good state.

Actions a mech takes outside its sandbox, such as calling another service, are not undone by a failed run.

Limits