Definition
Plain language
The working copy of a codebase sitting on disk, as pulled out of version control.
As stated in the literature
The materialized working tree for a particular commit, branch, or submodule reference; also the verb for switching the working tree to that reference.
Also called: checkouts, check out
Why it matters: The checkout is the concrete set of files an agent or tool can read and modify, so what sits in that folder defines the blast radius of anything running there.
For example, after cloning a project, the folder of files you can actually open and edit on your laptop is the checkout of whichever branch you happen to be on.
Heard on the show
“Lean is a formal proof language — think of it like a programming language where the programs are mathematical arguments and the compiler refuses to run anything that doesn't logically check out.”Episode 067 — An AI Just Solved a 1996 Erdős Problem—and the Simplest Agent Won