plan

name	plan
description	Iterative deep planning with critiques and alternatives. Use when facing complex design decisions, architecture choices, or implementation strategies that require thorough analysis. Trigger for any request involving "how should I design", "what's the best approach", "help me plan", "architecture decision", "trade-offs between", or when a user is choosing between multiple technical approaches. Also trigger when a proposed plan needs critique or when the stakes of a wrong decision are high. Prefer this skill over a one-shot answer whenever the problem has meaningful complexity, multiple valid approaches, or non-obvious failure modes.
allowed-tools	Read, Glob, Grep, WebSearch

Replan

Iterative design planning: plan → critique → refine. Repeat until robust.

---

Step 0: Calibrate scope

Before starting, assess complexity:

Signal	Iterations
Small change, low reversibility risk	1–2
New component, moderate coupling	2–3
System-wide change, high coupling, irreversible	3+

State your calibration explicitly: "This looks like a 2-iteration problem because..."

If unclear, ask one scoping question before proceeding.

---

Step 1: Understand & Frame

• Read relevant code, docs, constraints
• State assumptions explicitly
• Frame the core tension — what is this design fundamentally trading off? (e.g., "consistency vs availability", "flexibility vs simplicity", "speed now vs maintainability later")

---

Step 2: Initial Plan

Design your first approach. Include:

• Key decisions made and why
• What this plan optimises for
• What it deliberately sacrifices

---

Step 3: Critique (run every iteration)

For each iteration, work through all four lenses:

🔴 Failure modes

• What breaks first under load or scale?
• What's the hardest scenario to test?
• What assumption, if wrong, invalidates the whole plan?
• What would you regret in 6 months?

🟡 Complexity audit

• What's the most "hand-wavy" part — where did you assume without verifying?
• Where does accidental complexity sneak in (over-engineering, premature abstraction)?
• What requires the most context to understand?

🟠 Coupling & cohesion

• What breaks if requirements change 20%?
• Is this testable in isolation? If not, why not?
• Where are the hidden dependencies?

🔵 Reversibility

• What decisions are hard to undo?
• Is there a cheaper way to validate the risky assumptions first?

---

Step 4: Alternatives

Generate 2–3 alternatives. Each must directly address the critique from Step 3 — not just be stylistically different.

For each option:

Option [X]: [Name]

[1–2 sentence description]

Optimises for: [specific axis — simplicity, reversibility, performance, etc.] Sacrifices: [what it gives up] Kills which risk: [which critique item from Step 3 this resolves] Pros: ... Cons: ... Risks: ...

---

Step 5: Select & develop best alternative

Pick the option that best balances:

1. Resolves the highest-severity critique item
2. Most reversible if wrong
3. Simplest to test

State selection reasoning explicitly. Then develop it fully.

---

Step 6: Iterate

Repeat Steps 3–5 for the planned number of iterations (from Step 0).

After each iteration, pause and ask the user:

• Does this feel right, or is there a constraint I'm missing?
• Is there a decision here you want to make together?

---

Step 7: Final Plan

Synthesise the best features across all iterations. Structure:

1. Decision summary — key choices made and why
2. What this plan assumes — explicit assumptions
3. What would invalidate this plan — top 2–3 failure conditions to watch for
4. Implementation order — what to build/validate first
5. Open questions — things still worth investigating

---

Guidelines

• Kent Beck's Simple Design rules are a useful north star: passes tests → reveals intent → no duplication → fewest elements
• Honesty over confidence: say "I don't know how X works here, I'd need to check" rather than assuming
• For novel libraries or APIs: flag uncertainty and recommend a spike/prototype before committing
• Prefer reversible decisions over optimal-but-irreversible ones under uncertainty