devils-advocate

devils-advocate is a skill for Claude Code, Codex from melodic-software/claude-code-plugins. It costs 164 tokens per session (4,218 once invoked), scanned A, original, MIT.

An adversarial review of a plan or proposal that looks for unsupported assumptions and failure scenarios.

In plain words
What is it for?
It checks assumptions, dependencies, extensibility, drift detection, and graceful failure, and can also reassess an existing tool or approach.
Why use it?
It finds evidence-backed problems before implementation turns them into bugs, rework, or operational surprises.

Skill for Claude CodeCodex

Part of the planning plugin — 10 skills shipped together

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 skills/melodic-software/claude-code-plugins/devils-advocate
Any agent
npx skills add melodic-software/claude-code-plugins --skill devils-advocate
Clone the repo
git clone --depth 1 https://github.com/melodic-software/claude-code-plugins

Made for: Claude Code, Codex.

Or install planning, the plugin that ships this one along with the rest of its 10 skills.

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 devils-advocate

README.md
[![agentmods](https://agentmods.dev/badge/skills/melodic-software/claude-code-plugins/devils-advocate.svg)](https://agentmods.dev/skills/melodic-software/claude-code-plugins/devils-advocate)
Your own site
<a href="https://agentmods.dev/skills/melodic-software/claude-code-plugins/devils-advocate"><img src="https://agentmods.dev/badge/skills/melodic-software/claude-code-plugins/devils-advocate.svg" alt="Measured on agentmods" height="20"></a>
Per session 164 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,218 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 $0.00164 $0.04218
Opus 5 $0.00082 $0.02109
Sonnet 5 $0.00033 $0.00844
Haiku 4.5 $0.00016 $0.00422

Measured yesterday against content hash 8dcc1eb155c5, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

devils-advocate 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 yesterday.

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.

plugins/planning/skills/devils-advocate/SKILL.md · 228 lines

How it starts

The opening of the file, as written. The whole thing — 228 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Pre-computed context

Current branch: !git branch --show-current 2>/dev/null || echo "unknown" Recent commits: !git log --oneline -5 2>/dev/null || echo "no commits"

Variables

Arguments: $ARGUMENTS

Purpose

Plans fail for predictable reasons: unchecked assumptions, undiscovered bugs in dependencies, missing extensibility, no drift detection, no graceful degradation. This skill systematically finds these problems BEFORE implementation begins.

Not a rubber stamp. Find real issues that would cause rework, not generic warnings. Every finding must be backed by evidence. A specific bug number, doc reference, code path, or logical argument. "This might break" without evidence is not a finding.

The same discipline runs against the status quo. An incumbent tool, library, or approach already in place is a decision too, and "we already use it" is evidence of what is, never proof it still fits. The incumbent mode stress-tests that choice, naming the problem the incumbent actually solves, surveying alternatives, and asking whether a better fit exists now, before a plan commits to keeping or replacing it.

Fresh-context requirement

This stress-test runs from a fresh pair of eyes, and dispatches to a fresh-context sub-agent in two cases:

  • Plan-review mode. If the plan under review was produced in THIS context/session, the producing context shares the assumptions that created the plan's blind spots and drifts toward approving its own work; dispatch the stress-test to a fresh-context sub-agent. When you were invoked on an artifact this context did not author (a file, a plan from another session, a diff), you are already the fresh pair of eyes. Proceed directly.
  • incumbent mode. Always dispatch. The incumbent lives in the current codebase, so any read of it you already hold is a digest; a first-hand exploration is what forms an independent view. The sub-agent invokes /discovery:explore via the Skill tool (if installed, else explores directly) on the incumbent itself (Alternatives Sweep, Step 1).

Read the full file on GitHub · 228 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. yesterday First seen · 228 lines · 164 tokens per session scan A 8dcc1eb155c5

Subscribe to this mod's changes

devils-advocate is a skill published in the GitHub repository melodic-software/claude-code-plugins (15 stars, last pushed today), licensed MIT. It adds 164 tokens to every session and 4,218 once invoked, about $0.0008 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 2026-09-03.

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