When Cheaper AI Models Are Good Enough for Daily Development
When Cheaper AI Models Are Good Enough for Daily Development
Not every coding task needs the most powerful model. Writing a Python wrapper around an API, adding a new endpoint that follows an existing pattern, or updating test fixtures - these are routine tasks where a cheaper, faster model performs just as well as the flagship.
The Daily Coding Reality
Most development work is not architectural. It is:
- Writing CRUD endpoints that follow existing patterns
- Adding fields to data models
- Writing unit tests for straightforward functions
- Updating configuration files
- Wrapping external APIs with typed interfaces
For these tasks, Sonnet-class models are genuinely good enough. They follow patterns, they understand Python and TypeScript conventions, and they execute quickly. The speed advantage matters too - faster responses mean faster iteration cycles.
When You Actually Need Opus
The expensive model earns its cost on tasks that require deep reasoning:
- Architecture decisions - designing a new system, choosing between approaches, planning migrations
- Complex debugging - tracking down race conditions, understanding state management bugs across multiple files
- Novel code - building something that does not follow an existing pattern in your codebase
- Cross-cutting refactors - changes that touch many files and require understanding how they connect
Smart Routing Saves Real Money
The difference is significant. Using Opus for everything can cost 10-20x more than routing simple tasks to Sonnet. For teams running AI agents throughout the day, this adds up fast.
The routing does not need to be complex. A simple heuristic works: if the task involves creating something new or reasoning about system design, use the powerful model. If it involves following an existing pattern or making mechanical changes, use the fast one.
Desktop agents like Fazm can implement this routing automatically - analyzing the task complexity before choosing which model to call. You get Opus-quality thinking when it matters and Sonnet-speed execution when it does not.
Fazm is an open source macOS AI agent. Open source on GitHub.