What happened?

After PR #464 landed, the session composer can still render visibly wider than the message timeline in certain desktop window widths. The screenshot below was captured against dev HEAD (post-merge of #464) at a moderate window width with the right pane closed: the assistant message column wraps tightly, while the composer shell extends close to the window edge.

This means #464 fixed the regression for the layout state it targeted but left at least one path uncovered. Likely culprits to verify first: behavior with right pane hidden, narrow-but-not-tiny window widths, and any timeline column whose max width is smaller than the composer container's available width.

Area

UI or design system

Impact

Makes a workflow harder, but there is a workaround (resize window)

Steps to reproduce

1. Build dev HEAD via bun run dev:desktop.
2. Open or create any session with at least one assistant reply.
3. Resize the desktop window to a moderate width (around 1200–1400 px) with the right pane hidden.
4. Observe the composer shell vs. the message column.

What did you expect to happen?

Composer shell width should equal the message timeline width across all desktop window sizes, regardless of right pane state.

PawWork version

dev (built from dev HEAD on 2026-05-06, post #464)

OS version

macOS 15.x

Reproducible

Yes, every time at the affected widths.

Diagnostics

Manual smoke during v2026.5.6 release verification. Original fix landed in #464.

Suggested next steps

• Audit composer shell width binding against timeline column width across right-pane-open, right-pane-closed, and split states.
• Add a regression E2E that resizes the window across a few widths and asserts composer rect equals timeline rect width.