Takeaways
Which model to use for generating architecture.
The simpler the decision you need to make, the more readily you can just take a proposal from Fable or GPT-5.5. And now that Fable is unavailable outside the US, the choice between Opus and GPT is far from obvious. As a quick default I'd lean toward GPT.
Anthropic wants to enforce them via language of the contracts and take a hands off approach. OpenAI has a contract that is paired with humans in the room (FDEs) that can pull the plug.
The simpler the decision you need to make, the more readily you can just take a proposal from Fable or GPT-5.5. And now that Fable is unavailable outside the US, the choice between Opus and GPT is far from obvious. As a quick default I'd lean toward GPT.