CallRelayResult success arm gains undeliverable: string[]. sendCallRelay
parses FederationRelayResponse.undeliverable (when present) and returns
the messageIds so sendFederatedCallStart can reclassify per-peer results.
Old peers that omit the field → empty array → today's behavior.
TDD — three tests cover old-peer, new-peer-with-undeliverable, and 5xx paths.
Code-review catch: the Path-2 accept-rollback previously emitted
dm_call_undeliverable { terminal: true } via sendToFederatedCallUsers,
which broadcasts to every ringedUserIds entry. In a group DM this
would prematurely tear down non-accepting ringees whose own accept /
reject / timeout paths should govern their state. Switch to
sendToUser(acceptorId) so only the acting user gets the terminal
signal. Reorder the clearFederatedCall to happen before the emit so a
concurrent end-handler sees a cleared entry (clearFederatedCall is
idempotent). Spec updated, test extended to assert the scoping with a
two-ringee group-DM fixture.
Jannis Braun