Signals exist in multiple libraries with what are really minor variations on the theme.

> before the Promises/A design came out.

That's why the current proposal asks for input about design.

IIRC, promises also had multiple iterations on the design. There were calls to make them more monadic, less monadic, cancelable, non-cancelable etc.

And the original proposal looks nothing like the eventual API: https://groups.google.com/g/commonjs/c/6T9z75fohDk [1]

And new things are still being added to them (like Promise.withResolvers etc.)

[1] There's a great long presentation on the history of promises here: https://samsaccone.com/posts/history-of-promises.html