P: 'Save with history'

»But such experience is not required to see that if an application can provide history functionality in the current document, it can save that same history and restore upon reopening.«
Would this at the very least not necessitate a significant change to the psd or rather psb formats as psd’s size limitations would render it pretty close to useless for this?

Ah, the ol' Argument From Authority approach. I'll retract the word "trivial", but I have not been given any contradictory evidence, just blanket statements. I've not argued the file would not be bigger, but define "huge". An order of magnitude larger? For, say, a file with 50 history states? If the history states are matched up in memory before closing, why not exactly replicate them in memory again? If you can output all the steps to a log, why not just replay it? I do not know the method by which a single history state is stored (e.g. using deltas or compression), but if PS can save up to 8000 layers, it would seem feasible to save some fraction of that from the history. My raw photos are roughly 30MB. If I do lots of work on them, they may balloon to 200MB. If saving the history with important files bloats them to 2GB, I'm OK with that. It's obviously a feature lots of people want. Heck, turn it off by default. And if people use it, warn them: "Yer file is gonna get huuuggge!".

No, Photoshop doesn't do it. History saves the state of the entire document, not just a layer.

Now, I actually know the implementation, and the math, and am telling you that the file sizes would be huge. (and many users use all 1000 history states - and would want more if they were stored in a file for later use!)

What's difficult is matching up all the thousands of data structures that make up a document and it's history states and making them work correctly again after reloading.

It is really not that simple - and trying to claim that it is when experienced engineers are telling you that it is not... really doesn't help your case.

PS already does it. Why is a layer different than a history step in this regard? PS could require you to flatten the image or throw away inactive layers to save image size, but it doesn't because that would be dumb. I said "relatively" trivial, given the programming army behind PS. But PS already writes a history step to memory. What's so hard about writing that step to disk, then restoring it upon open? It would not have to restore the entire contents of OS memory, just whatever that document is using. Of course file size would go up, but I suspect by far less than some are suggesting. Most picture files would have several dozen history steps, max. PS allows you to set up to 1000 steps.

What you're asking for is more like saving an OS VM state to disk so that it can be loaded again later. It is possible, but it far from a trivial change and the files would be huge.

A variety, from various web, script, dynamically compiled languages to traditional compiled ones. But such experience is not required to see that if an application can provide history functionality in the current document, it can save that same history and restore upon reopening. It is essentially restoring a memory state, which is done by dozens of applications.

»One can lose hundreds if not thousands of strokes once a file is closed.«
You have set your History to more than a thousand steps?

»Arguments about laborious manual alternatives or RAM or disk space are ridiculous. Programmatically, the change is relatively trivial.«
What programming experience do you have that entitles you to make that assessment?

Exactly. This is an obvious and large deficiency in PS. I want a new WYSIWYG: What You Save Is What You Get. If I save an image with a long history, then close it, I should see that same history when I open it again. Arguments about laborious manual alternatives or RAM or disk space are ridiculous. Programmatically, the change is relatively trivial. If I want to use resources to accomplish it, that should be my choice, and the default. The opened file should take up no more RAM than it did before I saved and closed it, and disk space is cheap.

In retouching - it's impossible to save every brush stroke on a different layer. One can lose hundreds if not thousands of strokes once a file is closed. Yes, you can throw out everything and start over - or work in small sections on individual laters.

But it's really horrible to not be able to go backwards step-by-step on any given file after having closed it. I'd gladly sacrifice memory and or disk space to get true step by step history reproduction from start to finish - as an option - when I required it. It's already there when the file is open - a SAVE option isn't rocket science.