plan-challenger

plan-challenger is an agent for coding agents from FlorianBruniaux/claude-code-ultimate-guide. It costs 48 tokens per session (1,535 once invoked), scanned A, original, CC-BY-SA-4.0.

A read-only agent that challenges an implementation plan by systematically looking for weaknesses in five areas and testing whether suspected problems are real. It does not change code.

In plain words
What is it for?
Use it before committing to a major implementation plan when you want an adversarial review of its reasoning and likely failure points.
Why use it?
It helps expose missing assumptions, risks, and false concerns before a significant coding effort begins. This gives the team a chance to correct the plan while changes are still inexpensive.

Agent

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/florianbruniaux/claude-code-ultimate-guide/plan-challenger
Clone the repo
git clone --depth 1 https://github.com/FlorianBruniaux/claude-code-ultimate-guide

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for plan-challenger

README.md
[![agentmods](https://agentmods.dev/badge/agents/florianbruniaux/claude-code-ultimate-guide/plan-challenger.svg)](https://agentmods.dev/agents/florianbruniaux/claude-code-ultimate-guide/plan-challenger)
Your own site
<a href="https://agentmods.dev/agents/florianbruniaux/claude-code-ultimate-guide/plan-challenger"><img src="https://agentmods.dev/badge/agents/florianbruniaux/claude-code-ultimate-guide/plan-challenger.svg" alt="Measured on agentmods" height="20"></a>
Per session 48 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,535 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin unknown 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 $0.00048 $0.01535
Opus 5 $0.00024 $0.00767
Sonnet 5 $0.00010 $0.00307
Haiku 4.5 $0.00005 $0.00153

Measured 4d ago against content hash 8eb805cbcd08, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

plan-challenger 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 4d 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.

examples/agents/plan-challenger.md · 150 lines

The source is not reproduced here

Licensed CC-BY-SA-4.0

The repository is licensed CC-BY-SA-4.0, which this catalogue does not treat as permission to reproduce the file. Read it at the source.

Read it on GitHub

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. 4d ago First seen · 150 lines · 48 tokens per session scan A 8eb805cbcd08

Subscribe to this mod's changes

plan-challenger is an agent published in the GitHub repository FlorianBruniaux/claude-code-ultimate-guide (5,883 stars, last pushed today), licensed CC-BY-SA-4.0. It adds 48 tokens to every session and 1,535 once invoked, about $0.0002 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 2026-08-30.

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