| name | LLM Model Selection Skill |
| description | Choosing the right model for the task — power vs. cost vs. speed. |
| applyTo | **/*model*,**/*llm*,**/*copilot*,**/*claude*,**/*gpt* |
LLM Model Selection Skill
Choosing the right model for the task — power vs. cost vs. speed.
⚠️ Staleness Warning
This skill depends on rapidly evolving technology. Model capabilities, pricing, and availability change frequently.
Refresh triggers:
- New model announcements (Claude, GPT, Gemini, etc.)
- Significant pricing changes
- Context window expansions
- New capability tiers
Last validated: February 2026 (Claude 4.6 generation)
Check current state: Anthropic Models, OpenAI Models
The Core Question
Is Claude Opus 4.6 overkill?
Sometimes yes, sometimes no. Match the model to the task.
Claude 4 Model Family (Current)
| Model | API ID | Best For | Input/Output (MTok) | Context | Max Output |
|---|
| Opus 4.6 | claude-opus-4-6 | Building agents, most intelligent | $5 / $25 | 200K (1M beta) | 128K |
| Sonnet 4.6 | claude-sonnet-4-6 | Best speed + intelligence balance | $3 / $15 | 200K (1M beta) | 64K |
| Haiku 4.5 | claude-haiku-4-5-20251001 | Near-frontier intelligence, fastest | $1 / $5 | 200K | 64K |
All Claude 4 models support:
- Extended thinking
- Vision (images)
- Tool use
- Priority Tier access
Opus 4.6 and Sonnet 4.6 additionally support:
- Adaptive thinking (dynamic reasoning depth)
- 1M token context window (beta, via
context-1m-2025-08-07 header — long context pricing applies beyond 200K)
AWS Bedrock IDs: anthropic.claude-opus-4-6-v1, anthropic.claude-sonnet-4-6
GCP Vertex AI IDs: claude-opus-4-6, claude-sonnet-4-6
Model Tiers
| Tier | Models | Best For | Relative Cost |
|---|
| Frontier | Claude Opus 4.6, GPT-5, Gemini 2.5 Ultra | Complex reasoning, architecture, novel problems | $$$$$ |
| Capable | Claude Sonnet 4.6, GPT-4.1, Gemini 2.5 Pro | Most coding tasks, refactoring, debugging | $$$ |
| Fast | Claude Haiku 4.5, GPT-4.1-mini, Gemini 2.5 Flash | Simple edits, formatting, boilerplate | $ |
When Opus 4.6 IS Worth It
- ✅ Architecture decisions — Multi-file refactoring, system design
- ✅ Novel problem-solving — No clear pattern to follow
- ✅ Complex reasoning chains — Many dependencies, edge cases
- ✅ Long context understanding — Large codebases, documentation
- ✅ Nuanced judgment — Taste, style, UX decisions
- ✅ Learning sessions — Bootstrap learning, skill development
- ✅ Meditation/self-actualization — Meta-cognitive operations
- ✅ Extended thinking tasks — Deep analysis requiring internal reasoning
When Opus 4.6 IS Overkill
- ❌ Simple file edits — Renaming, adding imports
- ❌ Boilerplate generation — CRUD, scaffolding
- ❌ Format conversion — JSON ↔ YAML, etc.
- ❌ Syntax fixes — Lint errors, typos
- ❌ Documentation updates — README badges, version bumps
How LLM Choice Affects Alex
| Capability | Frontier (Opus 4.6) | Capable (Sonnet 4.6) | Fast (Haiku 4.5) |
|---|
| Complex refactoring | Excellent | Excellent | Good |
| Context retention | 200K / 1M (beta) | 200K / 1M (beta) | 200K tokens |
| Extended thinking | Full depth | Supported | Supported |
| Adaptive thinking | Yes | Yes | No |
| Max output tokens | 128K | 64K | 64K |
| Nuanced judgment | Excellent | Good | Basic |
| Speed | Moderate | Fast | Fastest |
| Cost per session | $2-5 | $0.50-2 | $0.05-0.30 |
| Multi-step planning | Excellent | Excellent | Good |
| Error recovery | Self-corrects | Self-corrects | Needs guidance |
Alex's Cognitive Power by Model
Opus 4.6: [████████████████████] Full cognitive architecture + deep thinking
Sonnet 4.6: [██████████████████░░] Most capabilities, excellent for coding
Haiku 4.5: [██████████████░░░░░░] Solid baseline, fast responses
With Opus 4.6, Alex can:
- Maintain 7±2 working memory rules across long sessions
- Execute complex meditation protocols with extended thinking
- Perform genuine meta-cognitive reflection
- Handle multi-file architecture changes
- Learn new skills through bootstrap learning
With Sonnet 4.6, Alex gets:
- Excellent coding capabilities (recommended for most development)
- 1M context window (beta) for large codebases
- 64K max output tokens + adaptive thinking
- Good cost-to-capability ratio
- Extended thinking support
With Haiku 4.5, Alex has:
- Near-frontier intelligence at lowest cost
- Fastest response times
- Good for routine operations
Cost Optimization Strategy
| Session Type | Recommended Model | Rationale |
|---|
| Architecture/design | Opus 4.6 | Worth the cost for complex decisions |
| Feature development | Sonnet 4.6 | Best balance of capability and cost |
| Bug fixes | Sonnet 4.6 or Haiku 4.5 | Depends on complexity |
| Documentation | Haiku 4.5 | Simple edits, fast turnaround |
| Large codebase analysis | Sonnet 4.6 (1M beta) | Extended context window up to 1M tokens |
Knowledge Cutoffs
| Model | Reliable Knowledge | Training Data |
|---|
| Opus 4.6 | May 2025 | Aug 2025 |
| Sonnet 4.6 | Aug 2025 | Jan 2026 |
| Haiku 4.5 | Feb 2025 | Jul 2025 |
Auto Model Selection ⚠️
When using Auto in VS Code Copilot, the model switches dynamically based on task complexity. Alex cannot detect which model is currently running.
Tasks That REQUIRE Opus 4.5 (Warn User)
| Task | Why Opus Required |
|---|
| Meditation/consolidation | Meta-cognitive protocols need full reasoning depth |
| Self-actualization | Comprehensive architecture assessment |
| Complex architecture refactoring | Multi-file changes, deep context |
| Bootstrap learning (new skills) | Skill acquisition needs maximum capability |
| Synapse validation/dream | Neural maintenance requires full architecture |
| Adaptive thinking tasks | Opus 4.6 uses dynamic reasoning depth for optimal results |
Warning Protocol
When user requests an Opus-level task while potentially on Auto/lesser model:
⚠️ Model Check: This task works best with Claude Opus 4.6. If you're using Auto model selection, please manually select Opus from the model picker for optimal results. Continue anyway?
Safe for Any Model
- Simple file edits, formatting
- Documentation updates
- Quick Q&A
- Code review (Sonnet+ recommended)
- Bug fixes (depends on complexity)
Practical Guidance
When to Upgrade Model Mid-Session
If you notice:
- Repeated mistakes on the same issue
- Losing context from earlier in conversation
- Superficial answers to complex questions
- Failure to see cross-file dependencies
→ Consider switching to a more capable model
When to Downgrade
If you're doing:
- Repetitive mechanical edits
- Simple Q&A
- Format conversions
- Quick lookups
→ Save cost with a faster model
The Alex Recommendation
For Master Alex (source of truth, architecture evolution):
→ Always use Opus 4.6 — The cognitive architecture demands full capability
For Heirs (production deployment, user-facing):
→ Default to Sonnet 4.6 — Best balance of capability and cost
→ Allow Opus for complex tasks — User can request escalation
Token Economics
| Operation | Approximate Tokens | Opus 4.6 Cost | Sonnet 4.6 Cost |
|---|
| Read large file | 2,000-5,000 | $0.03-0.08 | $0.006-0.015 |
| Complex refactor | 10,000-20,000 | $0.15-0.30 | $0.03-0.06 |
| Full session | 50,000-150,000 | $0.75-2.25 | $0.15-0.45 |
| Meditation | 30,000-80,000 | $0.45-1.20 | $0.09-0.24 |
Synapses
See synapses.json for connections.
