Troubleshooting oddly soft sourdough miche

Hi everyone,

I have a question about a loaf of sourdough that turned out softer and more delicate than I know what to do with, and I actually want to figure out how to give it a bit more strength.

I've been baking sourdough breads using a starter I picked up from a local bakery (I know, crazy that they gave me some) for about 6 or 7 years ago, and mostly using the Tartine method. Honestly, I've had about 80% success with the Tartine recipe and method. I find the moment I deviate from the basic recipe, even using one of their included variations, things can go wonky very quickly. Mostly I've been annoyed that even at a high hydration, the dough often feels tight and hard to stretch & fold.

Anyway, long story short I decided to try a new riff on the classic this week. I used the recipe from The Weekend Bakery's version of a Tartine loaf yesterday, the only change being I forgot to pick up some whole wheat flour so I used 100% fresh white bread flour instead. The dough was lovely and supple, and my starter was on fire yesterday. It almost rose right out of my banneton!

The question/problem I'm troubleshooting is that the bread, while beautify and tasty, is quite possibly the softest and most tender bread I have ever made. This makes cutting it without crushing it very difficult. I'd actually like to take the hydration up for more open crumb too, but the softness of this loaf makes me nervous to try.

Some details:

Poolish:

50g bread flour

45g water

10g sourdough culture

Bread:

100% of poolish

390g bread flour (original recipe called for 350g bread, 40g wheat)

260g water

6.5g sea salt

Method:

30 minutes autolyse. Add salt. Another 30 min autolyse. Stretch and fold every 30 minutes for 3.5 hours. Shape and rise in bannetton for about 3 hours. Baked in a preheated ceramic bread baker, lid on, at 450F for 30 minutes, baked with lid off for about 18 minutes with lid off at 450F.

Thanks!