Recommend optimal Claude model (haiku/sonnet/opus) for a task. Use when user asks "which model", "pick model", "model for", or before starting costly/complex tasks. Covers tech and non-tech tasks.
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tessl review fix ./skills/agentic-harness/pick-model/SKILL.mdClassify user's task → recommend optimal model with reasoning.
$ARGUMENTS| Model | When to Use |
|---|---|
| 🟢 Haiku | Simple transforms, formatting, regex, typo fix, status query, template fill, data extraction, factual lookup (no reasoning), file conversion |
| 🟡 Sonnet | Single-file coding, bug fix, code review, moderate debugging, test writing, PR review, standard refactoring, technical docs, API integration (known patterns) |
| 🔴 Opus | Multi-file refactor (3+ files), architecture/design decisions, complex debugging (multi-system), framework migration, security audit, novel algorithm design, system design with trade-offs |
| Model | When to Use |
|---|---|
| 🟢 Haiku | Summarization (<2K words), data extraction, status reports, simple translations, template filling, meeting notes formatting |
| 🟡 Sonnet | Content creation (blog, email, docs), research summaries, competitive analysis, standard business writing, persuasive proposals, marketing copy, customer communications |
| 🔴 Opus | Strategic planning, business model design, M&A analysis, organizational design, change management plans, competitive strategy, market entry decisions, crisis response, stakeholder management (competing interests), long-form reports (>2K words), executive presentations with nuance |
| Model | When to Use |
|---|---|
| 🟢 Haiku | Basic formatting, simple data viz suggestions, straightforward categorization |
| 🟡 Sonnet | Creative writing, brainstorming (single framework), persona development, user research synthesis, A/B test analysis, survey analysis |
| 🔴 Opus | Multi-framework brainstorming (SCAMPER + Starbursting + trade-off analysis), cross-session pattern detection, bias identification, retrospective analysis, ethical reasoning, strategic foresight, scenario planning |
| Model | When to Use |
|---|---|
| 🟢 Haiku | Simple conversions (PDF, EPUB), format checks, simple utilities, minimal reasoning |
| 🟡 Sonnet | Standard workflows, context management, serialization, most skills/commands (DEFAULT) |
| 🔴 Opus | Strategic analysis (brainstorm, retrospectives), multi-framework reasoning, high-stakes decisions, pattern detection across sessions |
Upgrade one tier if task has ANY of these signals:
Cap at Opus. If multiple escalators apply, still cap at Opus (don't "double upgrade").
When uncertain between two models:
Quality vs Cost trade-offs:
Speed considerations:
[emoji] **[Model]** — [1-line reason]
💰 Cost: [lowest/medium/highest] | ⚡ Speed: [fastest/medium/slowest]
💡 [Optional: "Consider [other model] if [condition]"]Example output:
🔴 **Opus** — Multi-stakeholder strategic decision with trade-offs
💰 Cost: highest | ⚡ Speed: slowest
💡 Consider Sonnet if this is exploratory (draft) rather than final recommendation| Task | Recommendation | Rationale |
|---|---|---|
| "fix typo in README" | 🟢 Haiku | Trivial single edit, no reasoning |
| "convert PDF to markdown" | 🟢 Haiku | Simple conversion, no decisions |
| "debug flaky integration test" | 🟡 Sonnet | Single-system debugging, moderate reasoning |
| "refactor auth across 15 files" | 🔴 Opus | Multi-file (3+ escalator) + architectural decisions |
| "design database schema for e-commerce" | 🔴 Opus | Architectural decision with trade-offs, long-term impact |
| "plan microservices migration strategy" | 🔴 Opus | Complex architectural planning + strategic impact escalator |
| Task | Recommendation | Rationale |
|---|---|---|
| "summarize this meeting transcript" | 🟢 Haiku | Simple text transformation, <2K words |
| "extract action items from notes" | 🟢 Haiku | Data extraction, no reasoning |
| "write blog post about AI trends" | 🟡 Sonnet | Creative writing, moderate reasoning |
| "draft sales proposal for enterprise client" | 🟡 Sonnet | Persuasive writing, moderate reasoning |
| "analyze competitor pricing strategy" | 🟡 Sonnet | Research/analysis, single framework |
| "plan market entry strategy for Europe" | 🔴 Opus | Strategic impact + cross-functional + ambiguity escalators |
| "design organizational restructuring plan" | 🔴 Opus | Political sensitivity + multiple stakeholders + strategic impact |
| "M&A due diligence analysis" | 🔴 Opus | Strategic stakes + cross-functional synthesis required |
| "crisis communication plan for data breach" | 🔴 Opus | Political sensitivity + stakes + multiple stakeholders |
| Task | Recommendation | Rationale |
|---|---|---|
| "translate paragraph to French" | 🟢 Haiku | Simple language transform, no reasoning |
| "brainstorm product names (single session)" | 🟡 Sonnet | Creative generation, moderate reasoning |
| "brainstorm with SCAMPER + trade-off analysis" | 🔴 Opus | Multi-framework escalator (SCAMPER + weighted scoring) |
| "retrospect: analyze collaboration patterns" | 🔴 Opus | Pattern detection + bias identification escalators |
| "identify blindspots in strategy" | 🔴 Opus | Bias identification + ethical reasoning escalators |
| "plan 3-day conference with speakers" | 🔴 Opus | Complex scheduling + multiple stakeholders + constraints |
| Task | Recommendation | Rationale |
|---|---|---|
| "command: convert EPUB to markdown" | 🟢 Haiku | Simple workflow, minimal reasoning |
| "command: save session context" | 🟡 Sonnet | Context management, serialization logic |
| "command: brainstorm with research + SCAMPER" | 🔴 Opus | Multi-framework escalator + strategic analysis |
| "command: retrospect domain learnings" | 🔴 Opus | Pattern detection across sessions + bias identification |
| "skill: format code with prettier" | 🟢 Haiku | Simple deterministic task |
| "skill: standard workflow implementation" | 🟡 Sonnet | Standard workflow, moderate reasoning |
| "agent: explore codebase architecture" | 🔴 Opus | Complex exploration + architectural synthesis |
NEVER default to the most powerful model for every task — Oversized models inflate costs without quality gain on simple tasks. Why: A haiku/flash-class model handles classification and routing at 10x lower cost.
NEVER pick a model based on benchmark leaderboards alone — Benchmark tasks often differ from production workloads. Why: Real task performance depends on prompt structure, context length, and domain specificity.
NEVER hardcode model names in agent workflows — Providers rename and deprecate models frequently. Why: Hardcoded names break silently on deprecation; use model tier aliases (fast/balanced/reasoning).
# BAD - pinned to a specific model id; breaks silently when the vendor retires it
routing:
summarizer: claude-3-haiku-20240307
reviewer: claude-3-opus-20240229
# GOOD - tier alias resolved to a current model id at runtime
routing:
summarizer: fast # resolves to whichever model is the current fast tier
reviewer: reasoning # resolves to whichever model is the current reasoning tierNEVER skip escalator checks for ambiguous tasks — Underestimating complexity leads to poor output requiring costly reruns. Why: A single missed escalator (e.g. multi-stakeholder, security risk) can push a task from Sonnet to Opus quality requirements.
# BAD - classifies on task label alone, ignores escalator signals
Task: "refactor the auth module"
-> Sonnet (looks like "single-file coding")
# GOOD - checks escalators before committing to a tier
Task: "refactor the auth module"
Escalators checked: touches 3+ files (Scope) + handles credentials (Stakes)
-> Opus (two escalators fired; Sonnet would under-resource this)NEVER conflate speed preference with model tier — Choosing Haiku solely for latency on a reasoning-heavy task produces wrong answers. Why: Speed and capability are separate dimensions; use the decision matrix first, then consider latency constraints.
Selecting a model for a code review task:
# Task: review 200-line TypeScript file for bugs
# Tier: balanced (Sonnet-class) — reasoning needed but not frontier
# Escalators: none (single file, no production risk flagged)
# Output: model alias + rationale
# -> Recommendation: Sonnet — single-file code review, moderate reasoning requiredRouting a summarization request:
# Task: summarize 5 meeting notes into bullet points
# Tier: fast (Haiku-class) — no complex reasoning needed
# Escalators: none (<2K words, no stakeholder trade-offs)
# -> Recommendation: Haiku — simple text transformation, no judgment requiredClassifying a strategic planning task:
# Task: design a market entry strategy for a new region
# Tier: reasoning (Opus-class)
# Escalators: strategic impact + cross-functional synthesis + ambiguity
# -> Recommendation: Opus — multiple escalators detected (strategic impact, ambiguity, cross-functional)a1083f4
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last in sync Aug 28, 2026
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