A missed compositionend (focus jump, input-source switch, programmatic DOM
swap mid-preedit) left composingRef stuck true, and the stuck flag silently
swallowed every Enter in handleEditorKeyDown and every Send-button submit via
the form onSubmit guard — no error, no RPC, until the composer remounted. For
CJK IME users (where even ASCII typing runs through composition) this read as
"Enter has no effect; messages cannot be sent", degrading composer instance
by composer instance.
Recover in two places, both grounded in invariants Chromium guarantees:
- keydown: every keydown during a genuine composition carries
isComposing=true, so when the native flag says we're not composing, clear
the stale ref before the guard reads it.
- blur: a composition never survives focus loss, so clear the flag
unconditionally — this is what unblocks the Send button path, which has no
native composition flag to consult.
The genuine-IME protection (#37483 class) is untouched: Enter with
isComposing=true is still swallowed.
Fixes#44135
AIalliAI
39e7607794