A Narrow Glass Is Not a New Layout
You open an existing Mac session as a spectator on a phone. The Mac has a hundred-and-twenty columns you laid out for four Anvil seats, or an editor, or htop at a width the TUI expected. The phone has a narrow portrait grid. If observation resizes the host PTY to the phone's columns, the Mac layout is no longer owned. TUIs reflow. Editors wrap. Four seats become unreadable on the glass you were actually working at. A spectator who resizes is not a spectator. They are a layout thief with a smaller screen.
The rule is brutal and short: looking never resizes. Observation fits or pans the grid. Fit means the existing cells are scaled or letterboxed so they remain the same cells. Pan means you slide across a grid that is larger than the glass. Neither sends a new size to the child. The PTY's rows and columns stay whatever the last surface that actually typed, pressed My size, or (on the Mac) changed its own layout asked for.
Fit and Pan Are Projection, Not Protocol
Those are drawing choices on the phone. They do not travel as "please become 40x12." The wire may say "here is the current grid size, here are the bytes." It may not say, from someone who is only looking, "make the grid this." If a watching gesture can emit a resize, looking has become typing. Track 6 says who does set the size: the grid follows the surface that typed last. This lesson is the floor under that rule: attaching, watching and rotating never move it.
Rotation on a phone is the sharp test. Portrait to landscape looks like a resize request. For a spectator, it is a fit-or-pan request. The glass changed. The child did not ask to change, and the Mac operator did not ask either. Treating rotation as SIGWINCH is how a pocket glance reflows a TUI the typist is in the middle of. The destination track will say durable mobile work needs checkpoints because rotation also wrecks parser state if you were the one typing. Different tense, same geometry: the child's size is not a function of whoever is looking.
The Mac Draws Someone Else's Grid Too
When the phone types, the grid follows the phone, and the Mac window draws that grid until the Mac types again. The Mac does not snap the session back just because a pane reattached or the app reopened: a Mac pane that joins a session another surface is typing in leaves its size out of the attach entirely. What does claim the grid on the Mac is a real layout change — resizing the window, changing a split — which counts as deliberately as a keystroke. Watching never does.
Copy still works for anyone who is only watching. You can select text, you can read the journal. You cannot send a terminal reply, you cannot grow the grid, you cannot terminate. Those refusals are one family. Resize is the one people forget because it does not look like typing. It is typing, to a TUI. Name it that way in review.