The current floating action button overlaps the composer on mobile — it covers typed text once the chips row and hints stack up (see V1). Every frame below renders the same mobile context: end of a message, the artifacts strip (now with the shipped fade fix), the Queue/Modes row, and the V1 composer. Pick the affordance that should replace the FAB.
44px solid circle, fixed bottom-24 right-5. Floats over the composer whenever the stack grows past ~96px — chips row, attachment previews, or a second text line push it onto the textarea.
＋ New chat becomes a chip pinned to the right end of the Queue/Modes row. Lives inside the layout flow — it can never overlap anything, and adds zero vertical space.
The mobile-standard "compose" affordance (Messages, Mail): a pencil-square icon button on the right side of the chat header, always visible regardless of scroll or composer state.
Keeps the FAB idea but makes it an extended pill (＋ New chat) anchored above the whole composer stack with a real gap, and auto-hides while the textarea is focused or the keyboard is open.
A smaller 34px rounded square that docks onto the composer box's top-right corner with a canvas-colored keyline — deliberately attached to the composer rather than free-floating over it.
A 26px ＋ button pinned to the right end of the strip row above the composer — the spot the current FAB visually collides with, but inside the layout. When no artifacts exist it sits in the Queue/Modes row instead (same as V2, icon-only).