The story of overfermented very simple sourdough

The holidays are playing all kinds of tricks with my baking schedule and thinking, so here is another salvaged near-flop.

My girlfriend's brother has been staying with us over the holidays, and when he was leaving yesterday I wanted to gift him a loaf of bread to take with him. But of course I didn't manage to plan it properly, and only could set up the very simple sourdough dough the night before, and spend minimal amount of hands-on time on it yesterday during the day.

I mixed a dough with 25% spelt, 10% extra strong whole wheat and 5% rye (rest BF), and 73% hydration, plus probably a few more percent from wetting hands during kneading (slap&folds): https://fgbc.dk/15p9. So I developed the gluten to a good degree, and left to ferment overnight (11 hours). Potentially important point is that I used 100% hydration rye starter from the fridge, not a stiff starter as in the recipe (since that's what I had). And more importantly, I used my "proofer", and I think I still need to play with the setup, since it appears the heating pad was on all night - and the dough overfermented! Especially at the bottom of the mixing bowl, where the heat is coming from, it was much more sticky than usual, and a lot of it was stuck to the bowl when I inverted it to remove the dough. And I got a very big rise, and I even had a feeling maybe it had peaked and started falling by morning. I'd never had dough overproof significantly in bulk like this, so it was a goo learning experience.

I tried shaping it, and while it was not a complete disaster at first, the gluten membrane on the outside was tearing very easily, and I couldn't make a tight boule or batard. So I decided to follow the common advice, to just dump the dough into loaf pans. I managed to shape one of them into batard-y roll, but the other one was impossible to work with, and just went into the pan as an unshaped mass of dough. I sprinkled sesame seeds on top, even if the bread is not great they are guaranteed to come out delicious. I then tried to proof it for a bit, but didn't see a significant rise. But by then it was time to go out for a walk to meet a friend, so I couldn't bake it and put them in the fridge, where they stayed a few hours, and I don't think it rose more than half a centimeter overall. I then scored it and baked it from cold (again, pressed for time I didn't even preheat the oven fully), and was pleasantly surprised by pretty good oven spring.

I lost track which one was shaped relatively well, and which was a complete mess when went into the pan, but they looked very similar in the end (I thought having a "skin" on the surface was beneficial for the crust, but it doesn't appear so!). I kept one of the loafs, and tasted it this morning.

Probably unsurprisingly, this is the most sour bread I've ever made! I still like it, but would prefer less acidity.