`appLayout` was passing `busy={ui.busy && !progress.streaming}` into
ToolTrail, so the moment `message.delta` fired and streaming began,
the panel internally saw `busy=false`. With the prior fix in place
(hasThinking = !!cot || reasoningActive || busy), that flipped
hasThinking to false and the Thinking expander vanished mid-turn —
reappearing only after message.complete when the finalized row
rendered with its own internal expander.
The `!progress.streaming` override was a defensive guard against the
panel implying "still thinking" once the response text was streaming.
But that's already handled inside ToolTrail — `streaming` prop on the
Thinking component uses `busy && reasoningStreaming`, and
reasoningStreaming is already falsey once recordMessageDelta calls
endReasoningPhase.
Pass plain `busy={ui.busy}`. Panel stays up start-to-finish; handoff
to the finalized-message row is continuous.
Brooklyn Nicholson
26f3a05c9c