What I do nowadays, for large changes, is have Fable create a HTML explainer for what we're gonna do with code snippets, which is not that fat from plan mode only much more convenient for me and modern models have no issue using that HTML artifact as the source of truth, and then before I get into execution - I interactively build an end to end test that also includes pieces of the plan.

When a test case fails, the relevant part of the plan is surfaced in the error. I find this helps Claude stay on track for longer - I've been able to do 12h most times and even up to 48h unattended (11h of API time) with good results.

Then whenever I do check in, I ask it to update the HTML with current state in an append only fashion (sort of like it's writing a blog), and then based on that, we iterate on the end to end test (I think of it as a "test harness") - update the test cases and error messages.

I've been able to build some truly large projects this way, both greenfield and up to spec (for example, a video game I've always wanted to play), and brownfield while staying within the conventions and design of the codebase, and with very little attention required on my part.