So happy to have diversified my model providers this past couple of weeks. GPT-5.5 has had no trouble slotting into Opus workloads. Will be fun to try out more of the models as time goes on to build some resiliency into my engineering workflows :).
Anthropic seems to have really killed their advantage by squandering the immense good will they built up by blundering over and over again the last few months with the developer community.
Tonight, for instance, after the incident had recovered, I restarted my work. On my Max account my usage period completely exhausted in 4 minutes of sonnet subagent work. This was long after prime time, and the workload was a fraction what I normally do.
These days I run codex concurrently and have gotten my marketplaces and plugins and MCPs adapted to it - other than the agents which I do lean heavily on - and generally find it a capable replacement. Anthropic needs to take notice and get their house in order.
*But* I don't work with the defaults -- I work with my own prompt framework based off of superpowers.
Given sufficient prompt scaffolding, I've found the models relatively interchangeable -- _I might_ be getting some of this for free by basing my own system off of superpowers which is used across various harnesses -- In other words achieving this kind of portability may be a lot harder than it looks and I'm benefiting from other people's work.
To get an idea of what I'm talking about, you could install https://github.com/obra/superpowers/ into both Codex and Claude Code -- You'll find that the behavior is remarkably similar if you A/B compare them on the same problems. CC occasionally misses things that Codex gets and vice versa.
Overall the output structure and final code is remarkably similar... Which is pretty different than if you just run them with their default system prompts. I'd throw codex out the window with its default outputs.
After reviewing the code, I also found it was annoying to get GPT 5.4 to actually fix the code based on my prompts compared with opus. I had to be far more specific and direct (which is related then to missing edge cases, complete, etc).