fix(agent): handle partial room timestamps without crashing

docs/api/streaming-chat.md

@@ -326,6 +326,14 @@ with `metadata.kind: "tool_call"`, matching Sybil's tool renderer. REST pages an
 socket messages are upserts keyed by stable `id`. Save each returned cursor after
 applying its entire frame, even when it contains no visible messages.
 
+Both message frames and queued activity use the required message envelope and
+historical timestamp compatibility rules in [REST room history](./rest.md#get-v1agentmessages).
+Protected tool redaction preserves `createdAt`, a safe string `content`, and
+available lifecycle metadata; it does not remove the row's identity or replay
+metadata. Partial tool results may omit `args`/`startedAt`; merge them without
+losing a known creation time or downgrading a completed tool on replay. Validate
+and normalize all rows before applying a frame or advancing its cursor.
+
 Clients may send `{ "type": "ping" }` (receiving `{ "type": "pong" }`) or
 `{ "type": "subscribe", "after": "44" }` to change the replay cursor. Transport
 ping/pong heartbeats detect dead connections. Other writes belong on REST.