| name | think-first |
| description | Apply mental models before major decisions. Enforces structured thinking before implementation. |
| use_when | User faces a significant decision, architectural choice, prioritization question, or trade-off that requires structured thinking. |
Think First
Stop and think before implementing. Apply mental models to significant decisions.
Why This Matters
Rushing into implementation causes regret:
- "We should have thought about that first"
- "Why didn't we consider the alternative?"
- "This is harder to change now"
With structured thinking:
- Assumptions surface before they bite
- Trade-offs are explicit
- Better decisions, fewer reversals
Quick Start
When you detect a decision moment:
- Stop — Don't proceed to implementation
- Identify — What type of decision is this?
- Select — Which mental model fits?
- Apply — Run the model
- Proceed — Continue with analysis informing the decision
Decision Detection
Decision moments include:
- Architectural choices ("should we use X or Y?")
- Prioritization ("what to build first?")
- Trade-offs ("speed vs quality")
- Direction changes ("should we pivot?")
- Resource allocation ("where to focus?")
Test: Is this a significant choice with trade-offs that will be hard to reverse?
If YES → Apply a mental model before proceeding.
Mental Models
Model 1: First Principles
Use when: Building something new, challenging assumptions, or stuck in conventional thinking.
Process:
- State the problem or belief being examined
- List all current assumptions (even "obvious" ones)
- Challenge each: "Is this actually true? Why do we believe this?"
- Identify base truths that cannot be reduced further
- Rebuild solution from only these fundamentals
Output format:
## First Principles Analysis: [Topic]
**Current Assumptions:**
- Assumption 1: [Challenged: true/false/uncertain]
- Assumption 2: [Challenged: true/false/uncertain]
**Fundamental Truths:**
- Truth 1: [Why irreducible]
- Truth 2: [Why irreducible]
**Rebuilt Understanding:**
Starting from fundamentals...
**New Possibilities:**
Without legacy assumptions, these options emerge...
Model 2: Inversion
Use when: Planning a project, avoiding failure, or stress-testing a plan.
Process:
- State the goal
- Ask: "What would guarantee failure?"
- List every way this could fail spectacularly
- Invert each failure into a preventive action
- Build the plan around avoiding failure modes
Output format:
## Inversion Analysis: [Goal]
**Goal:** [What we're trying to achieve]
**Guaranteed Failure Modes:**
1. [Failure 1] - How to avoid: [Prevention]
2. [Failure 2] - How to avoid: [Prevention]
3. [Failure 3] - How to avoid: [Prevention]
**Inverted Plan:**
To succeed, we must NOT do these things...
**Safeguards:**
Built-in protections against each failure mode...
Model 3: Opportunity Cost
Use when: Choosing between options, allocating time, or deciding what to build.
Process:
- List the options being considered
- For each option, identify what you're giving up by choosing it
- Quantify where possible (time, money, opportunities)
- Compare not just what you gain, but what you sacrifice
- Choose the option with acceptable trade-offs
Output format:
## Opportunity Cost Analysis: [Decision]
| Option | What You Gain | What You Sacrifice |
|--------|---------------|-------------------|
| Option A | [Benefits] | [Costs/foregone alternatives] |
| Option B | [Benefits] | [Costs/foregone alternatives] |
**Hidden Costs:**
- [Cost not immediately obvious]
**The Real Question:**
Not "is A good?" but "is A better than everything else I could do with this time/resource?"
**Recommendation:**
[Option] because [trade-off reasoning]
Model 4: Pareto (80/20)
Use when: Prioritizing work, finding leverage, or cutting scope.
Process:
- List all possible actions/features/tasks
- Estimate impact of each (even rough)
- Estimate effort of each
- Calculate leverage: impact/effort
- Identify the 20% that drives 80% of value
- Focus there first
Output format:
## Pareto Analysis: [Domain]
| Item | Impact (1-10) | Effort (1-10) | Leverage |
|------|---------------|---------------|----------|
| Item A | 9 | 3 | 3.0 |
| Item B | 5 | 7 | 0.7 |
**High Leverage (Do First):**
1. [Item] - [Why high leverage]
2. [Item] - [Why high leverage]
**Low Leverage (Defer/Cut):**
- [Items that seem important but aren't]
**The 20% Focus:**
These few things drive most of the value...
Model 5: 5 Whys
Use when: Diagnosing problems, understanding failures, or finding root causes.
Process:
- State the problem
- Ask "Why did this happen?"
- Take the answer and ask "Why?" again
- Repeat until you reach a root cause (usually 5 levels)
- Address the root, not the symptoms
Output format:
## 5 Whys Analysis: [Problem]
**Problem:** [Statement of what went wrong]
1. Why? → [First-level cause]
2. Why? → [Second-level cause]
3. Why? → [Third-level cause]
4. Why? → [Fourth-level cause]
5. Why? → [Root cause]
**Root Cause:** [The fundamental issue]
**Fix at Root:**
[How to address the root cause, not symptoms]
**Symptom fixes (temporary):**
[What addresses symptoms if root fix takes time]
Model Selection Guide
| Decision Type | Best Models |
|---|
| "What should we build?" | First Principles, Inversion |
| "How should we prioritize?" | Pareto, Opportunity Cost |
| "Is this the right direction?" | Inversion, Opportunity Cost |
| "What went wrong?" | 5 Whys |
| "Which option is best?" | Opportunity Cost, Pareto |
Integration
Add to any project's CLAUDE.md:
## Decision Protocol
Before implementing significant decisions, apply think-first:
- Architectural choices
- Prioritization decisions
- Trade-off analysis
Ensures structured thinking before implementation.
Success Criteria
