Seventeen bytes of grammar, fourteen of identity.

A queue's correctness starts below the queue. Key grammar, wire discipline, and version agreement are the three places where bus bugs are born and surface later as ghosts — a job row written under a hand-built key, a payload mangled by a line-oriented client, a consumer running last month's bundle against this month's keys. The part's answer is to name every shape exactly once, gate it, and have every later chapter cite this vocabulary rather than redefine it. The trading frame makes the stakes plain: the keys built here will carry orders.

The full committed transcript, verbatim — five gates, F1 through F5:

F1 map ok -- the part's map: emq:{orders}:pending | emq:{orders}:job:ORD0NgWEfAEJfs | {emq}:version | {emq}:locks -- 17 bytes before the payload
F2 gate ok -- the job position is gated: a fourteen-byte decimal and a fourteen-byte slug both raise before any wire is touched; kind policy waits for the enqueue script
F3 fence ok -- the fence holds on a live wire: GET {emq}:version answers echomq:2.0.0 through the fenced connector itself
F4 binary ok -- binary payloads with embedded CRLF and NUL survive 500/500 round trips through job keys in two pipelines
F5 slot ok -- co-location law: pending, active, meta, and the job row of {orders} all answer slot 105; {fills} answers 4165 -- multi-key scripts stay legal on the clustered day (vector 12739 holds)
PASS 5/5

Two design facts live in F1's line. The branded payload is the long part of a job key by construction — seventeen bytes of grammar, fourteen of identity — which is Chapter 1.3's economy carried onto the bus. And the version fence lives under {emq}: precisely because it is the one fact that is about the deployment rather than about any queue. F3's negative path is inherited, not re-run: the appendix's frozen record holds the typed refusal of a bogus version and the re-fence after supervised restart, and the part's evidence policy reads records rather than repeating them.

The obligation F2 defers — kind policy at the enqueue script — is collected by B3.2 · Jobs Are Entities, the next module of the chapter.