For example if you deliver an application, that's what one usually does.

> My understanding is that most people work with files, and execute stuff occasionally while they're editing, then save the files

One works with files, but together with the running Lisp system. I would work with a mix of compiled (fast load) and source files. Let's say you work on a new version of your graphics editor. You start the Lisp image and load the current version into it - mostly from fasl files. Some years ago people would more often have started a dumped image, because it took some time to load the fasl files. Even today, if the program is really large, you might want to use a dumped image of some version of it.

But independent of how you reach there, you start Lisp and then recreate a state of the working image (either from a dumped image or from loading files), where you continue to work from.

The image then will have a the development information, debug information, application state, compiler info, ...

In Smalltalk you would typically load a saved image more often. In Lisp you would recreate the state from a base image and then fast-load the stuff you need.

> And if you fail to run something, your source and your repl become out of sync.

Yes that happens and current Lisp systems actually don't have a goal to keep that in sync. You have to check manually that the source or the compiled system actually loads and runs - means recreate the correct state.

> I've never seen anyone actually doing image-based development in a lisp, despite some lisps supporting it - even in livecoding (music), the standard is to edit a file, then occasionally send parts of the file to a repl.

In the sense of Smalltalk (image + managed source code) there are only few people doing that in Lisp - nowadays. That debate (managed code images vs. a mixed file/image model) was lost in the early 80s with some later attempts to create a manage source model with code in data bases.

In the sense of saving images as pre-loaded code, that's seen and especially for application delivery. The LispWorks IDE I'm using has a lot of stuff pre-loaded (with some on-demand loading) as a single image. If I develop something, it is loaded into it and the application then is a newly dumped image. LispWorks also supports some exotic stuff like regularly saved sessions. It also keeps track which sessions have been saved based on which other sessions.

http://www.lispworks.com/documentation/lw70/IDE-M/html/ide-m...