[smallacc551collabagents]

Group sends re-fetched every member's identity on every send (/keys/identity per member for the device re-query, plus the revocation check), and safety() ran a per-member verifier.refresh loop.

What changed (crypto + minimal frontend glue)

• groups.ts: per-session cache of the GroupInfo and of the membership version whose member devices were verified. send() reuses the cached group and calls shareGroupKey({ requery: false }) unless one of these happens: the membership version changed, a 409 membership_changed (cache dropped, refetch + rotate), a member has a pendingChange (re-checked every send until accepted), or a to-device message arrives from a device other than the verified one. There's also an explicit markIdentitiesChanged(). refreshMembers(id, { force }) defaults to force.
• backend-bridge.ts: fetchIdentities() makes one POST /keys/identity/batch {usernames} (Backend). On 404 it falls back to deduped Promise.all GETs and remembers that per client, so the client works before and after the deploy. keys.query uses it.
• revocation.ts: prime(userIds) batch-refreshes stale entries. assertTrusted still compares against the exact device and records pendingChange (fails closed).
• olm-adapter.ts: honours requery:false and calls gate.prime once per share.
• frontend live.ts: the per-member verifier.refresh loop in safety() is gone. It now calls refreshMembers(id, { force }) with the existing 60s throttle.

Security: a replaced device still goes to pendingChange and gets no room keys until acceptMemberIdentity (test: identity-cache.test.ts, "identity gate keeps its security").

Call counts (fake backend, group of 4, 5 sends, revocation maxAge 0 so every send re-confirms):

	identity calls / 5 sends
before (main)	30 GET /keys/identity
after, no batch route (404)	15 GET (1 per member per send, deduped)
after, batch route live	5 POST batch, 0 GET
In production the revocation cache is 5 min, so a send within that window makes 0 identity calls.

Tests: 91/91 pass (4 new). tsc and eslint are clean.