VHS tapes

castwright reads VHS .tape files next to *.terminal.yaml: castwright build, validate and dev take them, and the Vite plugin compiles import demo from './demo.tape'. An existing tape becomes a web demo, an SVG or a GIF without a headless browser.

castwright build demo.tape --format svg --allow-exec

The promise is a documented subset, not VHS compatibility. Everything below is either translated, ignored on purpose, or rejected with a message that points at the line.

Commands run for real — with --allow-exec

A tape drives a real shell: Type "ls" + Enter means “run ls”. With --allow-exec (allowExec: true in the Vite plugin) each typed line that ends in Enter becomes an exec step: it is typed, run with /bin/sh -c in a pseudo-terminal, and its output is recorded with the timing it had. Env sets environment variables for the commands after it.

Without --allow-exec the typing is shown and nothing answers; the build warns once that the output is missing.

Each command runs in its own shell, so state does not carry from one visible command to the next. Commands typed between Hide and Show are the exception: they run silently before every visible command, so a hidden cd or export still applies. Keep them cheap — they run once per command.

A line edited with keys other than Backspace (arrows, Tab) is typed but not run. Ctrl+C on a typed line drops it, as the shell does. Programs that wait for keys — TUIs, pagers, prompts — cannot be driven: each command gets no input and must finish on its own within 60 seconds.

--record does not apply to a tape: it writes the output into a .terminal.yaml, and a tape has nowhere to keep it.

Commands

Command	Becomes
Type "…", Type@<speed> "…"	typing; a typed line + Enter is a command (see above)
Enter, Backspace, Tab, Escape, Space, Up, Down, Left, Right	the key; a count repeats it (Backspace 3)
Ctrl+C, Ctrl+D, Ctrl+L	the key
Sleep <time>	a pause — 500ms, 2s, a bare number is seconds
Hide, Show	nothing is shown in between
Env NAME "value"	environment for the commands after it
Copy "…", Paste	Paste types what was copied
Wait, Require	ignored — a command is already waited for; a missing program fails its step
Output, Screenshot	ignored with a warning — the format is --format
Source	error — copy the other tape’s commands in

Other keys (Delete, Home, End, PageUp, PageDown, Insert, ScrollUp, ScrollDown, other Ctrl+/Alt+/Shift+ combinations) are skipped with a warning. Anything else is an error.

Settings

Setting	Becomes
Width, Height, FontSize, Padding, LineHeight	the grid size, approximated from pixels
Columns, Rows	the grid size, exactly
TypingSpeed	the typing speed
Theme	the matching theme by name ("Catppuccin Mocha" → catppuccin-mocha); others fall back to default with a warning, JSON themes too
CursorBlink	whether the cursor blinks
Shell	warns when it is not sh-compatible, since commands run with /bin/sh
PlaybackSpeed	ignored with a warning
FontFamily, LetterSpacing, Framerate, Margin, MarginFill, WindowBar, WindowBarSize, BorderRadius, LoopOffset, WaitTimeout, WaitPattern	ignored — they only style VHS’s video

A tape that sets nothing gets VHS’s defaults: 1200 × 600 px at font size 22, which is 81 × 18 cells, typing at 50 ms per character, and VHS’s > prompt.