Currently running codex. I run one sandbox per repo. So I create the sandbox in the repo root. Then it's a custom terminal preset:

sbx run --name "yoursandbox" -- --cd "$PWD"

This boots a sbx session in the worktree directory.

For Claude there is no --cd so it's more hacky, but I solved it by creating a sbx kit with entrypoint script that reads a flag (e.g --cwd) from the terminal preset command and then inside the sandbox cd's there and starts claude.