# PEP integration sequence

`approval_engine.pep` implements the fail-closed ordering from
`GH-DEC-2026-003` without becoming a PDP:

1. fetch a fresh approval claim;
2. pass that claim to the consumer's authorization decision function;
3. require ALLOW, decision id, and the exact canonical request digest;
4. CAS-consume the approval;
5. only after confirmed consumption invoke the protected callback.

Claim or consume unavailability, invalid/consumed claims, DENY, digest mismatch,
and consume conflicts all prevent the callback. A same-digest retry receives
the engine's idempotent success. If the callback fails after consume, the
approval stays spent; there is no unconsume.

The module rereads the mounted bearer-token file on each HTTP request. Conflict,
unavailability, unauthorized, missing, DENY, and digest-mismatch paths all
prevent the callback. Same-digest consume retries are idempotent; a later full
sequence against a spent approval fails at the claim. The consume response is
rejected if it carries decision-shaped keys (`effect` / `allow` / `deny`).

The live HTTP harness in `tests/test_pep.py` drives this sequence against the
real WSGI surface without performing a protected action. secrets-engine owns
the production OpenBao PEP (`src/secrets_engine/approval_consume.py`); that
handler is implemented and proven in-repo for 409 / unreachable / missing
binding. Live closure still needs this service deployed and a durable consume
binding served (`SECRETS-WP-0007-T04` / `SECRETS-WP-0008-T02`).