# Working in this repository

## `_corpus/heldout/` — do not read, do not run anything against it

**This is the one instruction in this file that cannot be recovered from if you get it wrong.**

`_corpus/heldout/` holds a frozen set of real published papers whose entire purpose is to be
material **no detector was written knowing about**. Its protocol
(`reverse_engineer/HELDOUT.md`) states the spend rule directly:

| set | role | spent by |
|---|---|---|
| challenge-card fixtures | train | authored with the detector |
| the current corpus | validation | **acting on a fire** |
| a fresh frozen corpus | test — one unbiased number | **reading it** |

Reading is not a neutral act here. A fire rate measured on these papers asserts *"no detector was
written knowing this paper"*; reading one in order to author or justify a change is exactly how a
detector comes to know it. The protocol's own instruction is **"Never open them again except to
label a fire."**

So, when working anywhere in this repository:

- **Do not open** `_corpus/heldout/*.md`.
- **Do not run** a detector, a grep, or a scan across `_corpus/`.
- **Do not cite** a number derived from it as evidence for changing a detector.
- If a task seems to require it, stop and ask. It almost certainly does not.

`_corpus/` is gitignored, so `git status` will never show a change there and a clone will not carry
it. Neither fact protects it: **anything scanning the working tree sees it.** That is not
hypothetical — on 2026-07-31 an audit was launched against "the repository", three of its agents
reached `_corpus/heldout/`, and one ran a detector across the corpus and opened two of the papers.
The finding it produced was quarantined and not acted on, and the corpus in place was already spent,
so nothing measurable was lost. The next corpus is the one that reading destroys, and this file
exists because the fence was in a prompt instead of in the repository.

## Everything else

`CONTRIBUTING.md` is the entry point: how to run the gate mirror before pushing, the worktree
discipline, and what a change is expected to ship with.