Then for execution: Use plan mode. Let it always write a plan first, check it, correct it and only then allow it to implement it.

Try to break big tasks down in small substeps. As small as possible. Let it implement changes iteratively. Let it do a lot of local git commits. Both Codex and Claude Code use this as documentation as well.

Basically, treat it like a junior developer working under you.

Make sure appropriate tests are written for every code change.