The server echo of an optimistic user message carries different part
ids, so the reducer dropped the optimistic part and appended the server
one at the end, and MessageBody keyed user parts by part id. The key
change remounted the text subtree (blank frame, markdown re-parse,
truncation state reset) and the append reordered text against file
parts.
Replace the optimistic part in place and key user parts positionally.
Keeps optimistic prompt state in the session directory
Routes live assistant part updates using upstream event payloads
Adds regressions for startup session switch races
Canonicalize session message/part materialization across load, prefetch, reconnect, and recovery paths so OpenChamber restores session snapshots through one consistent merge flow.
Preserve live assistant streaming text when stale or delayed snapshots arrive, while still replacing optimistic user parts with confirmed server snapshots to avoid duplicated user messages.
Narrow recovery triggers to explicit incomplete snapshot signals instead of broad session-event fallbacks, reducing unnecessary session refetches during active streaming.
Keep turn windowing aligned with parented assistant replies and add regression coverage for materialization gaps, stale snapshot protection, optimistic user replacement, reconnect recovery, and turn grouping.
Bohdan Triapitsyn