Chat-hardening plan Phase 2 — only current authenticated room members can
create chat UI work, impersonation via the wire name is structurally closed,
and no member can monopolize the event channel:
- core: new ChatRoster (bounded id -> sanitized-name map, shared) replaces the
event task's bare HashSet; upserted on PeerJoined/PeerUpdated, removed on
graceful PeerLeft AND terminal grace-expiry eviction (both timer paths).
Non-roster chat is dropped before attachment handling; the rendered author
label is the roster-bound name — the sender-claimed wire name is never read.
- gossip: ChatIngressGate after verify_gossip, before any sanitize work or
event send: early known-author gate (live + mid-reconnect peers), exact-
replay suppression keyed on the deterministic Ed25519 signature (1024-entry
cap + freshness-window TTL, zero new deps vs the plan's BLAKE3 option), then
per-author (8 burst, 1/s) and room-wide (32 burst, 8/s) token buckets.
Replays are detected before tokens are consumed; a room-bucket reject
refunds the author token; rejection logging is squelched per author.
- The inner Chat.ts is now ignored entirely; RoomEvent carries the signed
envelope timestamp.
550 lib tests (+18), reconnect_eviction +1 (grace keeps chat authority,
terminal eviction revokes it), clippy --all-targets -D warnings clean.
Tests-green-only: the plan's two-machine field-test section remains open.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
