# 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. Its unit
harness uses a dry-run callback and demonstrates the ordering, but live closure
requires the secrets-engine-owned handler to prove that no OpenBao request is
made in every failure case.