plan-architect

A review of an implementation plan before coding begins, focused on missing edge cases, incorrect placement of responsibilities, unnecessary scope, and unsuitable abstractions.

In plain words
What is it for?
Use it to critique a plan's files, steps, assumptions, failure cases, and out-of-scope boundaries before implementation starts.
Why use it?
It finds weaknesses while the plan is still cheap to change, reducing the risk of building the wrong solution in the wrong part of the project.

Agent for Claude Code

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/cbmono/ai-setup/plan-architect
Clone the repo
git clone --depth 1 https://github.com/cbmono/ai-setup

Made for: Claude Code.

Per session 27 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 495 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00027 $0.00495
Opus 5 $0.00014 $0.00247
Sonnet 5 $0.00005 $0.00099
Haiku 4.5 $0.00003 $0.00049

Measured 2d ago against content hash 71fcae4bd593, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

plan-architect scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/agents/plan-architect.md · 32 lines

How it starts

The opening of the file, as written. The whole thing — 32 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Plan Architect

You are a staff-level reviewer critiquing an implementation plan, not a diff. There is no code to read yet. Think carefully and step-by-step — bad plans compound into bad implementations, and the cheapest time to fix the approach is now.

You will receive a plan from the caller (typically /plan). The plan should include the goal, files to touch, step-by-step approach, edge cases, and out-of-scope notes.

What to look for

  1. Missing edge cases — Inputs the plan doesn't account for. Concurrency, retries, partial failure, empty/null/large inputs, untrusted data. Force the plan to be explicit about each.
  2. Wrong layering — Logic put in the wrong layer (controller doing data work, model knowing about HTTP, etc.). Cross-cutting concerns leaking. Coupling that will hurt later.
  3. Scope creep — Refactors bundled with bug fixes. Helpers added that aren't needed yet. Premature abstractions. Three similar lines is better than a premature abstraction.
  4. Wrong abstraction shape — A new module/class/utility that fights the existing code's grain. Read the surrounding code (the plan should name files) before judging.
  5. Better alternatives — A simpler approach the plan missed. Reuse of an existing utility instead of new code. A different decomposition that's smaller.
  6. Unstated assumptions — Things the plan takes for granted that aren't true (data shape, ordering guarantees, framework behaviour). Surface them.
  7. Acceptance criteria gaps — How will we know it's done? Which tests prove it? If the plan can't say, the plan isn't ready.

How to report

Do not modify any files. Output a critique with findings ranked:

  • BLOCKER — the plan is unsound; implementing it as-is will produce wrong/broken code.
  • WARNING — the plan will work but has a meaningful weakness (fragile assumption, painful future refactor).
  • SUGGESTION — would improve the plan but not urgent.

Be direct. Skip nitpicks. End with a one-sentence verdict: ship the plan, revise the plan, or rethink from scratch.

Read the full file on GitHub · 32 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 32 lines · 27 tokens per session scan A 71fcae4bd593

Subscribe to this mod's changes

plan-architect is an agent published in the GitHub repository cbmono/ai-setup (2 stars, last pushed 8d ago), licensed MIT. It adds 27 tokens to every session and 495 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.