Screenshots and clips of cmux

cmux shot writes a png or a jpeg of a cmux window. cmux record writes an mp4 or a gif of one. Both capture only cmux's own windows, both go through the same permission-free path, and both work in a release build and inside CI. No Screen Recording permission is involved and none is ever requested.

cmux shot --label settings-sheet                  # png of the frontmost window
cmux shot --jpg --max-width 1200 --out ~/before.jpg
cmux record start --gif --max-seconds 8 --label sidebar-drag
cmux record note "dragging the workspace"         # caption, drawn into the clip
cmux record stop

shot prints <width>x<height> <bytes> <path>. record prints <id> <state> <frames> <path>. Both take --json for the whole response.

Which one

Take a screenshot when the thing is still: a sheet, a menu, a layout, a label, a color. Record when the thing is a change over time: a drag, an animation, a reorder, two views settling in an order, a spinner that should stop. A screenshot of a drag shows nothing, and a clip of a static sheet is a large file a reviewer has to click to play.

Working from a clip to a still

--region x,y,w,h is the same rectangle in both commands, in window points from the window's top left. So a detail noticed in a clip can be shot with the same four numbers:

cmux record start --region 0,0,420,900 --max-seconds 6   # watch the sidebar
cmux shot --region 0,0,420,900 --label sidebar-final     # keep the end state

Notes for an agent recording its own cmux