Where the person talks back
The chat input shell: an attachments row, an auto-growing textarea, a leading actions slot, and a teal send button. Send is the one primary CTA in the chat set, so it is the one place the action colour appears. While a response streams, send becomes stop and Enter goes inert.
The shell
The shell is the control. The textarea inside is borderless, so the border carries hover and focus for the whole surface. Enter sends, Shift and Enter breaks the line, and whitespace alone never sends. Submitting reports the value but does not clear it; the consumer owns the value and empties it after a successful send.
Send and stop
While a response streams, the send button becomes a stop button and submitting is blocked, so a person can never fire a message into a running answer. Try it: send something and the demo streams for a few seconds.
Idle. Type a message and send it.
Attachments
The attachments row renders whatever the caller passes, DocumentChips by intent. The list is fully controlled, the same philosophy as FileInput: the composer never owns the files, it only shows them.
Growth
The textarea starts at one row and grows with its content up to maxRows, eight by default, then scrolls internally. This one is capped at four rows; add lines to feel the cap.
The full footer
The intended stack: a PromptSuggestions row above the composer, with a leading action for attachments. Tapping a suggestion fills the input; sending clears it.
Nothing sent yet.