Three review passes each found the same class of defect: a route nobody had
checked, rather than logic that was subtly wrong. One of them — `PUT
/sessions/{id}/peers/{id}/config`, which let any caller set a scope to
`observe_others=false` and silently stop all fan-out into it — predated this work
entirely, because the guardrail set was assembled guardrail-by-guardrail instead
of derived from the route list. Sampling review cannot close that kind of gap;
enumeration can.
Derives every route through which a peer name can reach the system and requires
each to be classified as GUARDED or EXEMPT-with-a-reason, so a newly added
peer-touching route fails the suite until someone classifies it. Detection is the
union of path shape and a walk of the dependant tree (including sub-dependency
`Form(...)` params and nested request-body models), because neither signal alone
suffices: parameter names miss `POST /sessions/{id}/peers`, whose peer names are
dict keys, and path shape misses `messages/upload`, whose `peer_id` arrives as a
form field behind a parser dependency.
Both invariants are then asserted behaviorally, by calling the routes rather than
inspecting annotations — the guards deliberately live in crud, which is what makes
`messages/upload` guarded for free via `crud.create_messages`:
- a real scope is refused on all 11 guarded routes, and the rejection must name
the scope, so an unrelated 422 (a malformed body) cannot pass the assertion;
- an *unflagged* peer merely occupying the reserved namespace is unaffected. That
half regressed once already when `update_peer` used a name-based check.
Mutation-tested all three failure modes: disabling the `set_peer_config` guard
fails the guarded test naming that route; regressing `update_peer` to name-based
fails the squatter test; adding an unclassified peer route fails the enumeration.
Covers the HTTP surface only. Peer names also reach the system through the
deriver, dreamer, and queue, which have no route table to enumerate — noted in
the module docstring rather than implied to be covered.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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