plat 030

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PLAT-030 — main coding-agent terminal is not a durable scrollable transcript

Coordination	Value
Assigned agent	Codex
Ticket state	implemented
Last synchronized	2026-08-05

• Priority: P0
• Owner: Terminal Center live-attach geometry lifecycle
• Evidence: the Social Media main terminal connected at 117×43, then a vertical layout change reconnected it at 117×38. The Claude tmux remained healthy and continued receiving automatic completion notifications, but its native history_size was 0. The reconnect reset xterm and seeded only the current tmux screen, so all browser-accumulated history disappeared and the pane appeared frozen/unscrollable.
• Root cause: there were two independent limitations.
  1. Every grid change used the destructive width-change path. A row-only layout change therefore reset xterm even though line wrapping had not changed.
  2. Claude's live tmux pane is currently in the alternate screen (alternate_on=1, history_size=0). The raw pane is a fixed-screen TUI, not an append-only conversation transcript. Even after eliminating the resize reset, it cannot provide historical scrolling by itself.
• Implementation:
  1. Grid changes are classified as none, rows-only, or columns. A row-only change fits xterm and sends {type:"resize", cols, rows} over the existing socket. Column changes retain the suspend → close → fit → reconnect → authoritative-seed path.
  2. Main coding-agent terminals now default to their structured event transcript, which is durable and scrollable and receives the same automatic notifications. The header retains a Raw control for exact TUI inspection. Child terminals still default to raw output.
• Verification: focused frontend tests pin 117×43 → 117×38 as row-only and prove only column changes require reconnection. TypeScript compilation passes. Real tmux tests also prove target-session closure and external-width changes still close their viewers correctly.
• Acceptance: main-agent history remains readable and scrollable as new automatic notifications arrive. Vertically resizing the Terminal Center or showing/hiding UI chrome does not interrupt the live stream. A true width change may re-seed raw output because preserving old hard-wrapped rows would corrupt the display. Users can still select Raw when they need to operate the full-screen CLI, without treating that buffer as durable history.