3.1 KiB
Agent Note: Intent draft echoes in the same tick
Status: implemented Archived: 2026-07-26
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Problem
The hero composer ("Let's start building") is a controlled textarea whose value is the frontend Session Intent's retained prompt, read from the sessions list snapshot (EmptyState binds intent.prompt via useSessions). Typing routed through SessionManager.updateIntent → Session.updatePendingPrompt, which flushes the Session's own notifier synchronously — but the list snapshot the composer actually renders from only heard about the change through the intent watch subscription in startIntent, which calls markDirty(), a microtask-deferred flush.
A deferred echo violates the controlled-input contract documented on the Notifier (see the web client architecture note): React compares the DOM value against the still-stale snapshot during the same tick as onChange and rolls the textarea back. With plain typing this shows as caret jumps; with an IME it corrupts input — every composition update gets rolled back and re-applied against a stale value, so typing Pinyin "nihao" commits fragments like "nnini hni hani hao你好". The resident composer (ConversationRoot) was not affected: its draft lives in the chat store (sync flush) or comes from updateSessionPrompt, which reads the Session snapshot directly rather than the list projection.
Decision
SessionManager.updateIntent calls this.notifier.notifyNow() after updatePendingPrompt, flushing the list snapshot in the same tick as the change event. This matches the Notifier's channel rule: a direct echo of a user gesture whose controlled input renders from this snapshot uses notifyNow; the intent watch keeps markDirty for every other (async) intent transition.
Alternatives considered
Change the intent watch callback in startIntent to notifyNow. Wrong channel for that seam: the watch also fires on frame-driven Session changes (publication, send phases), and the architecture note bans notifyNow for frame-driven sources because it collapses batching.
Have EmptyState read the prompt from the Session snapshot instead of the list. Restructures the slot contract (EmptyState is deliberately bound to the standard useSessions feed and has no session scope yet — the frontend Session is page-local) for no gain over flushing the projection it already reads.
Suppress the rollback in InputBar with local uncontrolled state. Hides the symptom, forfeits the single-source-of-truth draft (the retained prompt must survive workspace retargeting and send/retry), and leaves every other list-snapshot-controlled input exposed.
Consequences
Typing in the hero composer, IME composition included, echoes synchronously. updateIntent on a no-intent state stays a no-op with no notification. The web workspace-flow snapshot's composer helper now asserts the same-tick echo instead of waiting for it, so a regression to a deferred echo fails the keyless snapshot gate; a runtime unit test pins the same contract at the manager seam.