Mixed
I find that Codex 5.5 is pretty good at surgical fixes, but does not go out of its way to explore and figure out what those surgical fixes might break
enraged_camel on Hacker News
In the thread “Previewing GPT‑5.6 Sol: a next-generation model”, replying to this comment
Helped: Surgical fixes on isolated parts of the system.
Got in the way: Lack of exploration to identify potential regressions.
… I'm working in a 600k+ LoC codebase that has complex domain-specific logic and lots of moving parts. I find that Codex 5.5 is pretty good at surgical fixes, but does not go out of its way to explore and figure out what those surgical fixes might break. So I only use it to work on parts of the system that are pretty isolated from everything else so that risk of regression is small.