Observation:
LLMs like Claude or ChatGPT are *GREAT* for getting you from 0-80%. During this phase you are the product manager and code reviewer, and the LLM is the programmer.
The last 20% you may want to switch roles: you are the coder and the LLM the reviewer.
Throughout the process you're best aided by making use of LLM-generated tests, executed by you, in order to keep the two of you from creating regression bugs.