Problem

On long conversations (often citation-heavy answers, which tend to be longer), the chat message area grew past the viewport and pushed the ChatInput below the fold — users couldn't see or reach the input box.

Root cause

Classic flexbox min-h-0 trap. The flex chain from the fixed-height root (h-dvh overflow-hidden) down to the scroll container (flex-1 overflow-y-auto) had several intermediate flex items — <main>, <section>, and the messages div — with no min-h-0. A flex item's default min-height: auto refuses to shrink below its content's intrinsic size, so instead of the inner overflow-y-auto engaging, the whole column expanded and shoved the input off-screen.

Fix

• min-h-0 on <main> and <section> in chat-shell.tsx
• min-h-0 on the messages scroll container in both app/chat/page.tsx and app/chat/[chatId]/page.tsx
• shrink-0 on the ChatInput form so it's always pinned and never compressed

5-line change, no behavioral change beyond the scroll fix. Also fixes the CitationRail's own scroll (its aside already had overflow-y-auto but the un-constrained <main> defeated it).

Test plan

• npm run build
• Open a chat, send enough messages (or one long citation-heavy answer) to exceed the viewport — message area scrolls, input stays pinned at the bottom and visible
• Right-side Sources rail scrolls independently when it has many citations
• Mobile width: input still visible and pinned

🤖 Generated with Claude Code

Summary by cubic

Fixes the chat input being pushed off-screen in long conversations by correcting the flex layout. The message area now scrolls as intended, and the Sources rail scrolls independently.

• Bug Fixes
  • Added min-h-0 to <main> and <section> in components/chat-shell.tsx.
  • Added min-h-0 to the message containers in app/chat/page.tsx and app/chat/[chatId]/page.tsx.
  • Added shrink-0 to the ChatInput form to keep it pinned.

^{Written for commit d56dcba. Summary will update on new commits.}