Give each parallel attempt its own checkout and session

02 / BUILD

Three-step implementation

1. 01

   Frame the contract

   Write down the caller, data classification, success condition, timeout, cancellation, and ownership. Use it when several attempts at one task must proceed without overwriting each other, or when a long run needs follow-up instructions without a restart.

2. 02

   Build one narrow path

   Implement one end-to-end path with request correlation, typed state, and reversible failure handling. Codex CLI 0.163.0 separates where work happens from which session owns it: --worktree creates a managed Git worktree, codex exec fork copies a saved session into a new one, and codex queue sends a message to an existing session.

3. 03

   Prove the outcome

   Turn acceptance into a repeatable fixture, contract test, or browser test. Evidence is one worktree path and session identifier per attempt, every queued message landing on the intended thread, and a primary checkout that still holds no uncommitted agent edits.