Two real bugs found in an adversarial review of the core real-time path:
1. Queued message vanishes (high impact): the message.updated handler dropped
EVERY temp- optimistic message when any real message arrived, so sending a
second message while the first was still processing made the second
disappear from the chat until its own event landed ('did my message send?').
Extracted the merge into a tested pure helper (mergeIncomingMessage) that
resolves only the oldest pending temp of the same role.
2. selectSession race: rapidly switching sessions on a flaky network could let
a slow fetch for a previous session overwrite currentSession/messages of the
newer selection. Added a monotonic sequence token; a stale result is
discarded.
Also reviewed but intentionally NOT changed: the SSE-reconnect-on-connection-
switch path (already handled via the [client] effect cleanup + reconnect) and
abortSession leaving 'sending' set on failure (deliberate — the run may still
be live; per its own comment).
Claude-Session: https://claude.ai/code/session_01T12AhSnQVrSxNnvwfCx2z6
Co-authored-by: engineer <engineer@macbookpro.lan>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
