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Reset terminal state leaves the alternate screen while the program is still running #347
Description
What happens
Reset terminal state (Ctrl+Shift+R, or the command palette) calls resetTerminalModes. When the pane is on the alternate buffer, terminalResetSequence(true) starts with ESC[?1049l, which switches xterm back to the normal buffer.
That is right for the case the command was written for (#175): the program that entered the alternate screen has died, and the pane is stuck in its modes. But the wmux:reset-terminal handler in useTerminal.ts runs whenever the PTY is present, including while the program is still running. A running fullscreen program (Claude Code, opencode, vim) never re-sends ESC[?1049h, because from its side nothing happened. The result is the same as #345:
- the program's next frames are drawn into the normal buffer and its scrollback
- a full-screen clear from the program wipes the shell's own lines
- when the program exits, its
ESC[?1049lhas no alternate screen to leave and only restores the cursor, so the shell prompt is printed over the stale frame
The resetTerminalModes doc comment expects a live program to put back the modes it wants ("reset while vim is up and vim repaints"). That holds for modes a program re-asserts on every redraw. It doesn't hold for the alternate screen.
Steps to reproduce
I found this by reading the code and haven't reproduced it in the app. Expected reproduction:
- In a terminal pane, run:
cls; "MAIN-1"; "MAIN-2"; [Console]::Write("`e[?1049h`e[H"); 1..5|%{"ALT-BEFORE-$_"}; Start-Sleep 15; 1..5|%{"ALT-AFTER-$_"}; Start-Sleep 3; [Console]::Write("`e[?1049l"); "EXITED"
- While it sleeps, press
Ctrl+Shift+Rin that pane. - Expected bug:
ALT-AFTER-1..5land on the normal screen, and on exitEXITEDand the prompt are printed at the top over the old content.
Possible fixes
- Leave the alternate buffer only when the program is gone: keep
ESC[?1049lon the process-exit path and drop it from the manual reset. A pane whose program is still running stays on the screen that program is drawing. - Or decide per pane with the shell state wmux already tracks (OSC 133). Leave the alternate buffer when the shell is back at its prompt, and keep it while a command is running.
wmux version
2.39.0
Anything else
Related: #175 (where the reset was added) and #345 (same end state, reached through a remount).
Activity
amirlehmam commentedon Oct 24, 2026
Shipped in v2.40.0. Thanks for the detailed report!
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