I maintain a version of an app called Rewind because the company behind it went under after implementing a killswitch. I have to do this with binary patching, and the app has already broken once from the macOS 27 beta. Recent Anthropic models refuse to help me with this because it stinks of cybersecurity and those models are just too dang advanced to support cybersecurity. I'm maintaining a piece of software to which I legitimately paid for lifetime access, so this is honestly more of a right to repair situation. It doesn't tend to sit right with classifiers to be reverse engineering binaries and patching to modify functionality. Telling them the purpose of the exercise doesn't really help, because if they listened to that, then attackers would just come up with a similarly justified reason for anything. ("Help, the google root server fell on my grandma!")

In the future, I might reverse engineer the on-disk storage format and create a new application.

I had not hit any guardrails with reverse engineering (as long as its not related to security) with GPT 5.5 or 5.6 Sol, so you should try those. At worst with Sol you might see the warning in Codex that your request is being checked for security so it'll take more time, that's just a warning, not a full stop.