pick-model

name	pick-model
description	Evaluate whether the CURRENT model+effort fits a task, and recommend a switch only when worth the cache cost. Use when user asks "which model", "pick model", "model for", "what effort", "is haiku enough", "Opus or Sonnet", "should I downgrade/upgrade", or when routing a non-trivial task to a tier before starting costly/complex work. Judges model AND effort level. Does NOT execute the prompt — only judges fit. Covers tech and non-tech tasks.
model	sonnet
effort	low
context	main

Pick Model

Take the user's intended prompt as input. Do NOT execute it. Read the live session state, classify the prompt, emit verdict + delta + strategy: is the current model right, and if not, is switching worth the cache cost.

CLAUDE.md contract: this skill is the single source of truth for the model/effort routing call. CLAUDE.md "Execution defaults" carries no model table — it defers here by capability (auto-discovery on the description). Don't re-derive or duplicate the tier table elsewhere; if routing changes, it changes here.

Two levers, different cost (the core call):

• 🎚️ Effort change, same model → cache SURVIVES (cheap). Recommend freely.
• 🔀 Model switch → cache BREAKS, context re-read uncached (costly). Must beat the switch penalty.

A third lever — parallelism (linear vs fan-out, sub-agents vs Workflow) — is out of scope here. To design a skill/agent's per-step execution topology (and have it call this skill per step), use /pick-workflow.

Recognize-then-route: hit the right tier directly; reserve top-tier (Opus high / Fable) for ambiguous/big/can't-classify. Effort = output-spend, not input. See reference.md for principles, routing detail, escalators, examples.

Workflow

1. Read live state

pick-model-state

Emits model= ctx_tokens= ctx_pct= cache_hit_pct= cost_usd= duration_min= (jq + path resolution live in dstoic/scripts/pick-model-state, on PATH). Bare call — no shell expansion, so it's allowlistable and won't trigger a permission prompt. Don't compute these by hand. Fallback (prints state=missing, or command not found pre-sync): read model + ctx% from the statusline bar or ask user; note ⚠️ estimated state, never guess silently.

2. Classify + pick ideal model + effort

Match prompt to tier. Apply escalators (cap +1 tier). See cheatsheet + routing table in reference.md.

Tier	Model	Effort	Shape
Chore	🟢 Haiku 4.5	none	convert/format/extract/typo/lookup
Plumbing/standard	🟡 Sonnet 5	low–high (default medium)	GTD/commit, single-file code, content, review, agentic tool use, light multi-file
Thinking	🔴 Opus 4.8	high→xhigh (⚠️ defaults high)	strategy, hard 3+ file refactor, architecture, security/audit, PhD-reasoning
Boulder	🟣 Fable 5	adaptive	multi-day, >200K context, sustained ambiguity

Effort sets: Sonnet 5 low|med|high|xhigh|max · Opus low|high|xhigh|max · Haiku none · Fable adaptive-only. ⚠️ Sonnet 5 default = medium (≈ Sonnet 4.6 @ high). Avoid xhigh/max on Sonnet 5: new tokenizer ≈ +30% tokens → can cost MORE than Opus for similar quality. Need that depth → switch to Opus, don't crank Sonnet effort.

3. Quantify switch cost (only if ideal model ≠ current)

awk -v ctx=CTX_TOKENS -v hit=CACHE_HIT_PCT -v rate=NEW_RATE \
  'BEGIN{printf "switch_penalty ~ $%.3f\n", ctx*(rate/1000000)*(1-0.9*hit/100)}'

Rates $/M in: Sonnet 5 = 3 ($2 intro thru 2026-08-31) · Opus 5 · Fable 10. Higher ctx% + cache hit = costlier switch; late-session switch for marginal gain = waste → prefer effort tweak.

4. Emit verdict

🎯 Verdict: [✅ Stay | 🎚️ Change effort | 🔀 Switch | ⬆️ Upgrade | ⬇️ Downgrade]
Current:  [🤖 model] [effort] · 🧠 [ctx%] · ♻️ [cache%]
Ideal:    [model] [effort]
Why: [task shape vs current capability, 1-2 lines]
[if switch] 💾 ~$[penalty] re-cached → [worth it because… | NOT worth it, tweak effort instead]
🧭 Strategy: [e.g. "start Sonnet 5 med, escalate to Opus high only if scope >3 files or security-sensitive"]

Logic: same model+effort ok → ✅ Stay · same model, effort off → 🎚️ tweak (cheap) · diff model, gain > penalty → 🔀/⬆️/⬇️ · diff model but penalty high + gain marginal → stay/tweak, state trade-off · chore/plumbing on Opus → ⬇️.

Anti-patterns

• ❌ Opus high as default — wastes tokens on chores/plumbing.
• ❌ Late high-context switch for marginal gain — re-cache > savings.
• ❌ Effort-as-input cost — it's output spend; on loops higher can be cheaper.
• ❌ Guessing current model — read state file or ask.
• ❌ Loading /claude-api for a model fact — use this skill's table.