Addresses three review findings against 48047a6a.
1. `PeerSpec` let API callers create invalid and reserved-prefix peers.
Widening `get_or_create_peers` to accept a pattern-free schema fixed the
lookup 500s but also removed validation from the *insert* path, and
request-controlled names reach it via message authors, session peer maps, and
the chat observer path — none of which carry a charset pattern of their own.
Confirmed: `POST /sessions/{id}/messages` with `peer_id: "scope.x"` returned
201 and minted an unflagged squatter, after which `POST /scopes {id: x}` was
permanently 409-blocked — namespace denial of service by any caller able to
post a message. `peer_id: "not a valid name!@#"` was likewise created.
Fixed by validating only names about to be INSERTed
(`_validate_new_peer_names`), so already-existing names — legacy dotted
names, scope peers — still resolve without a spurious 422. That keeps the
Dreamer fix intact, since it reads through `get_peer`.
2. Existing reserved-prefix squatters could not be updated. The name-based guard
on `PUT /peers/{peer_id}` refused every `scope.` name, contradicting the
invariant that an unflagged squatter stays a normal peer. Now flag-based, so
behavior is three-way: a real scope is refused, an existing unflagged peer
updates, and a missing reserved-prefix name is refused by (1) rather than
minted.
3. Scope checks raced with get-or-create and the membership upsert. The
route-level guards run before peers are resolved, so a scope created
concurrently in that window would be attached by the generic path with a
default `SessionPeerConfig()`, clobbering its observer membership config.
Adds `_reject_resolved_scope_peers`, which runs on the resolved rows in the
same transaction as the upsert — no window, no extra query. The early checks
stay for better error messages.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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