Gates

Every build ships the gate that checks its output.

Where they are and what they are called

Gates are not uniform. Some sit at the root of their build and some in its tests/ folder, and the names vary because each is named for what it checks rather than for being a gate. One takes an argument.

docs/gates.md lists every one with its exact path and both commands: run directly, and run as a hook. Use it rather than guessing at a filename.

The two ways to run one

Run directly and a gate exits 0 when it passes and 1 when it fails, which is the Unix convention and what you want at a command line.

python tools/as_hook.py python <the gate>

That is the other way. A hook only blocks a tool call on exit 2. Exit 1 is treated as a non-blocking error and the action proceeds, so a gate wired in directly reports its failure and stops nothing. The wrapper translates the code, which lets one script be correct in both places. Chapter 20 covers this, including the two ways a hook can end up silently absent.

The builds

Chapter	Build	Folder
0	00-reading-code	builds/00-reading-code
2	02-what-an-agent-does	builds/02-what-an-agent-does
4	04-first-session	builds/04-first-session
6	06-prompting-like-a-reviewer	builds/06-prompting-like-a-reviewer
7	07-verification-gates	builds/07-verification-gates
8	08-git-and-environments	builds/08-git-and-environments
9	09-literature-triage	builds/09-literature-triage
10	10-statistics-assumption-checks	builds/10-statistics-assumption-checks
11	11-survival-and-dose-response	builds/11-survival-and-dose-response
12	12-publication-figures	builds/12-publication-figures
13	13-sequence-and-omics	builds/13-sequence-and-omics
14	14-docking-prep	builds/14-docking-prep
15	15-image-and-plate-reader	builds/15-image-and-plate-reader
16	16-lab-data-management	builds/16-lab-data-management
17	17-manuscript-assembly	builds/17-manuscript-assembly
18	18-deposition	builds/18-deposition
19	19-grant-and-thesis-drafting	builds/19-grant-and-thesis-drafting
21	21-error-hunt	builds/21-error-hunt

A gate you have never seen fail is not a gate. Break something on purpose and confirm it fails, for the reason you expected.