[pm]

I'm assuming this is a technical co-founder in the stricter sense, rather than an early-employee CTO. If the case were the latter, I'd most likely be inheriting a dumpster fire built by an agency or a jilted technical co-founder, neither of which is a good position to be in.

If that's the case, then the onus is on the founder as much as me to prove their worthiness. I've inherited too many dumpster fires in my career to implicitly trust the word of non-technical co-founders.