## Definition A **model selection strategy** maps tasks to the right tier in a model fleet — typically Haiku, Sonnet, Opus — instead of defaulting one model for everything. ## The Three-Role Rubric - **Sonnet — the Builder.** Default for *implementation*. Fast enough to keep flow, cheap enough to run all day. The right answer when in doubt. - **Opus — the Architect.** Reserve for *decisions*. Slower and more expensive, dramatically better at cross-file synthesis and "should we even do this" questions. - **Haiku — the Scout.** Built for *exploration and filtering*. Fan-out searches, classifications, hook-driven routing. ## Selection Heuristics | Pick… | When… | | ------ | ------------------------------------------------------------------------ | | Sonnet | Clear spec, 1–5 files, streaming flow matters | | Opus | Cross-file architecture, public API, irreversible call | | Haiku | Large corpus filtering, parallel fan-out, frequent cheap classifications | ## Budget Heuristic — 90/9/1 A working starting point for a feature-shipping week: - ~90% Sonnet (the actual coding). - ~9% Opus (planning, review, gnarly bugs). - ~1% Haiku (scouts, hooks, classification). Opus drifting above ~20% is *over-thinking, under-shipping*; below ~3% is *under-thinking, shipping bugs*. ## Configuration (Claude Code) ```jsonc { "model": "claude-sonnet-4-6", "subagents": { "architect": "claude-opus-4-7", "scout": "claude-haiku-4-5-20251001" } } ``` ## Related - [[Reasoning Budget]] - [[Specialized Agent]] - [[Prompt Caching]]