Bottom routing

Bottom fishing (also called Bottom routing): we are not a “best model” picker. We are a cheapest model that can still do the job picker (Tier‑0 / Tier‑1 by default), so spend falls through routing rather than a thin markup-only margin. Default model string from Id and most clients: bottom.

Policy

1. If you set a concrete model id → pin (no fishing).
2. Else start in Tier‑0 (DeepSeek / Flash‑Lite / Haiku-class).
3. Escalate to Tier‑1 only on failure or a hard hint (huge prompt, effort=high).
4. Mid / Frontier only after lower tiers fail — or you pin them.
5. Prefer retry-next-cheapest over jumping to Opus.

Stay-rate

Target: ≥85% of unpinned traffic stays on Tier‑0 / Tier‑1 (bottom_stay_rate). Agents apply the same policy per step so loops do not silently burn frontier tokens.

From Id

• Default: --model bottom (or omit)
• Pin: --model anthropic/… or /model … in the REPL
• Escalate hint: --effort high
• Inspect catalog: Id models · /models

Pricing interplay

Inference is metered at 1.5× provider cost against prepaid balance. Bottom fishing keeps most turns on cheap tiers; pinning frontier is always available when you need it. See Billing and Pricing.

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