Addresses a fourth review pass against 62681e4d. The headline finding is that the
previous commit's enumeration test had the wrong *model*, not a missing entry.
1. Manual conclusions could create knowledge about a scope. `POST /conclusions`
validated only that observer_id and observed_id exist, so a scope as
`observed_id` persisted a conclusion about a peer carrying observe_me=false and
created an (observer, scope) collection for it. Confirmed: 201, and it read
back. `POST /schedule_dream` had the same hole via `observed`.
The fix is positional, because the invariant is:
A scope may be an OBSERVER. A scope may never be OBSERVED.
A scope as `observer_id` is how scoped conclusions are stored and must keep
working (verified still 201); as `observed_id` it is now refused. Same split
applied to schedule_dream `observed`, the peer-card `target` (which also covers
a scope's self-card, since target-omitted collapses observed to peer_id), and
session-context `peer_target`.
2. Chat target and both representation roles kept check-to-use races. Only the
chat path-level observer was re-checked on its resolved row; the target was
checked by name and then resolved without inspecting scope identity. Both are
now checked at the dialectic preflight, where observer and observed are already
resolved — an absent name has already failed by then, and an existing squatter
cannot retroactively become a scope.
3. Generic membership removal was still racy. The adjacent SELECT narrowed the
window but could not close it under READ COMMITTED. The UPDATE now carries its
own correlated NOT EXISTS against scope_peer_clause(), so Postgres evaluates
the exclusion as part of the statement and a scope committed after the advisory
check still cannot be detached.
4. New-name validation ran after the name reached Postgres. A NUL byte passed the
request schemas and PeerSpec, then raised psycopg.DataError inside the lookup —
a 500. Values that cannot correspond to a stored row by construction (NUL
bytes, over-length names) are now refused before the query.
(Over-length names already returned 422; only the wasted query was real there.)
The enumeration test is rekeyed from (method, path) to (method, path, position).
A binary per-route verdict cannot express finding 1 at all: `POST /conclusions` is
one route with two positions and opposite verdicts. Detection widens to observer /
observed / target / peer_target / peer_perspective, which surfaced four routes the
previous version never saw — conclusions, schedule_dream, queue/status, and
session context.
Also registers `src.routers.workspaces.tracked_db` in the conftest patch list; the
new guard there would otherwise have run against the real configured database
instead of the per-test one.
Mutation-tested: disabling the conclusions observed-guard fails the positional
test naming that position; adding an unclassified `observed_id` param fails
enumeration.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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