GPT 5.4 vs Opus 4.6: Simplicity vs Over-Architecture
GPT 5.4 vs Opus 4.6: Simplicity vs Over-Architecture
After months of using both models for desktop agent development, a clear pattern has emerged. Opus picks the simplest approach that solves the problem. GPT builds elaborate architectures for problems that need three lines of code.
The Architecture Gap
Ask both models to add a feature flag system. Opus will suggest a dictionary and a config file. GPT will design a feature flag service with a database backend, admin UI, gradual rollout percentages, and A/B testing integration. Both technically work. One ships today, the other ships next month.
This is not about capability - GPT can absolutely write simple code when directed to. The difference is in default behavior. Left to its own judgment, GPT gravitates toward comprehensive solutions. Opus gravitates toward minimal ones.
Why Simplicity Wins for Agents
Desktop agents need to be debuggable. When something goes wrong at 2am, you need to trace through the code and find the issue. A simple approach has fewer places where bugs can hide. An over-architected solution has abstraction layers, dependency injection, event buses - all of which are potential failure points.
The best code for an agent is code you can read top to bottom and understand in five minutes. Opus tends to produce that kind of code by default.
Where GPT Shines
GPT's tendency to build comprehensive solutions is actually valuable for planning and system design. When you need to think through all the edge cases of a complex system, GPT's inclination to consider everything is a feature, not a bug.
The trick is knowing which model to use when. Architecture planning with GPT, implementation with Opus. Let each model play to its strengths.
Fazm is an open source macOS AI agent. Open source on GitHub.