kienbui1995 Cost-Aware Model Routing
Overview
Not every task needs the most expensive model. Route tasks to the right model based on complexity, saving cost without sacrificing quality.
The Routing Table
| Model | Agent | Cost | Best For |
|---|---|---|---|
| Opus | architect | $$$$$ | Complex architecture, novel design, ambiguous requirements |
| Sonnet | debugger, ui-designer, (default) | $$ | Implementation, debugging, most coding tasks |
| Haiku | reviewer | $ | Code review, verification, simple lookups, formatting |
Cost ratios (approximate):
- Opus : Sonnet : Haiku ≈ 25 : 5 : 1
- A Haiku review costs ~1/60th of an Opus review
Decision Framework
WHEN receiving a task:
1. Can Haiku handle this? (review, verify, format, lookup)
→ YES: Use reviewer agent or --model haiku
2. Is this standard implementation/debugging?
→ YES: Use default Sonnet (or debugger/ui-designer agent)
3. Does this require deep reasoning about novel problems?
→ YES: Use architect agent (Opus)
Task → Model Mapping
Use Haiku (reviewer agent) for:
- Code review after implementation
- Verification checks (tests pass? linter clean?)
- Simple refactoring (rename, reformat)
- Documentation review
- Checking git status/diff
- Quick lookups in codebase
Use Sonnet (default) for:
- Feature implementation
- Bug fixing and debugging
- Writing tests
- Database migrations
- API development
- UI component building
- Most day-to-day coding
Use Opus (architect agent) for:
- System architecture design
- Complex brainstorming with many trade-offs
- Ambiguous requirements that need deep analysis
- Cross-system integration planning
- Performance optimization strategy
- Security architecture review
Anti-Patterns
| Pattern | Problem | Fix |
|---|---|---|
| Using Opus for everything | 25x cost for same result | Default to Sonnet |
| Using Opus for code review | Overkill, slow | Use Haiku reviewer |
| Using Haiku for implementation | Too many mistakes | Use Sonnet |
| Not using agents at all | Missing cost savings | Dispatch to right agent |
CLI Shortcuts
# Quick review with Haiku
claude -p "review the last commit" --model haiku
# Debug with Sonnet (default)
claude -p "fix the failing test in auth.py"
# Architecture with Opus
claude -p "design the caching layer" --model opus
# Budget cap
claude --max-budget-usd 0.50 -p "implement the login form"
Measuring Impact
Track your usage in Claude Code settings or Vertex AI console:
- Before: ~98% Opus = high cost
- After: ~10% Opus, ~70% Sonnet, ~20% Haiku = ~75% cost reduction