agent-routing

# Agent Routing — model, effort, and cascade selection ## The rule that decides everything **Cost is output tokens × output price.** Prices span ~5× across tiers. Token counts span up to **7× within a single tier** depending on task shape. The shape therefore decides more than the tier does, and *routing on the per-token discount gets the answer backwards*. Measured 2026-08-17, 14 spec-dense Python modules graded by hidden tests, all tiers at equal quality where noted: | arm | tok/task | pass | $/task | vs opus | |---|---|---|---|---| | haiku-solo | 20,051 | 14/14 | $0.1007 | **1.30×** | | haiku + concision | 13,342 | 12/14 | $0.0672 | 1.01× | | opus-solo | 3,001 | 14/14 | $0.0774 | 1.00× | | sonnet-base | 4,687 | 14/14 | $0.0478 | 0.62× | | sonnet + concision | 2,951 | 13/14 | $0.0305 | 0.42× | | **sonnet cascade** (below) | — | **14/14** | **$0.0315** | **0.41×** | Haiku is 5× cheaper per token and cost **30% more per solved task** than Opus, because it emitted 6.7× the tokens. Prices: Haiku 4.5 $1/$5, Sonnet 5 $2/$10, Opus 5 $5/$25 per MTok. ## Two questions before spawning 1. **Is the output short or long?** Short = a schema instance, a label, an answer, a small patch. Long = a module, a document, a plan, a review. 2. **Is it mechanically checkable, or does it need judgment?** | | short output | long output | |---|---|---| | **checkable** | `haiku` @ `low` + verifier | `sonnet` @ `medium` + concision + verifier | | **judgment** | `sonnet` @ `medium` | `sonnet`/...