[kitlangton]

Exploration for Kit's "why is this composer so big?" note. Draft: the default layout is unchanged (layout defaults to "today", and nothing in the app passes another value). The variants live behind a layout prop on Composer/ComposerEditor so they can be compared in Storybook: OpenCode/Composer/Flow → Layouts (layout × scenario × width) and Layout In Session (with the "7 subagents" chip).

Today, measured (CSS px, 720px composer)

• 104px at rest. The editor is min-h-[60px] with pt-4 pb-2 and a 20px line, so 16px of its height has no job. The text line ends at y=36 and the controls start at y=68, a 32px gap. The form also has min-h-[96px].
• Control row: 44px tall with 28px controls, 8px from the edges. + at x=8, model text at x=51, variant text about 22px after the model chevron. Those gaps are the ghost buttons' 11px padding plus ms-1/gap-1.
• For reference on Kit's screen: ChatGPT is 82pt with model and effort in one chip ("GPT-6 Astra Medium"). Claude is a 36pt single-row box, with its "Opus 5.5 Medium" chip outside it.

Layouts

Layout	Empty height	What changes
today	104	Shipped
tight	88 (−16)	Drops the 60/96px minimums. Text→controls goes from 32px to 16px, the same as the 16px top inset. No rule changes.
joined	88 (−16)	tight, with the variant inside the model chip ("Anthropic / Claude Opus 5.5 High ⌄"). The model dialog already changes the variant with ←/→.
slim	76 (−28)	joined with a 12px text inset and 24px controls 8px from the edges. The + glyph sits on the text's 12px spine.
inline	44 (−60)	One row at rest (+ · input · chip · send). It becomes joined once the draft wraps or has context, and stays two rows until it is cleared.

Verification

• bun typecheck (packages/app)
• One headless capture run of every layout and state (Storybook on pro, via hivemind)
• Default path: the only changes are a data-layout="today" attribute, two data-slots and a CSS variable whose default is the old 16px value