double-checking-before-acting

double-checking-before-acting is a skill for Claude Code, Codex from FlyFission/nuclear-grade-context-engineering. It costs 78 tokens per session (1,123 once invoked), scanned A, original, MIT.

A before-and-after check for a critical agent action, comparing the exact target and expected result with what actually happened.

In plain words
What is it for?
Use it before and after high-stakes edits, commands, dependency or model changes, credential use, migrations, releases, or public statements.
Why use it?
It catches wrong targets and unverified success before an edit, command, migration, release, or public claim is treated as safe.

Skill for Claude CodeCodex

Part of the nuclear-grade plugin — 24 skills, 28 commands, 5 agents 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/flyfission/nuclear-grade-context-engineering/double-checking-before-acting
Any agent
npx skills add FlyFission/nuclear-grade-context-engineering --skill double-checking-before-acting
Clone the repo
git clone --depth 1 https://github.com/FlyFission/nuclear-grade-context-engineering

Made for: Claude Code, Codex.

Or install nuclear-grade, the plugin that ships this one along with the rest of its 24 skills, 28 commands, 5 agents.

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 double-checking-before-acting

README.md
[![agentmods](https://agentmods.dev/badge/skills/flyfission/nuclear-grade-context-engineering/double-checking-before-acting.svg)](https://agentmods.dev/skills/flyfission/nuclear-grade-context-engineering/double-checking-before-acting)
Your own site
<a href="https://agentmods.dev/skills/flyfission/nuclear-grade-context-engineering/double-checking-before-acting"><img src="https://agentmods.dev/badge/skills/flyfission/nuclear-grade-context-engineering/double-checking-before-acting.svg" alt="Measured on agentmods" height="20"></a>
Per session 78 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,123 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 $0.00078 $0.01123
Opus 5 $0.00039 $0.00562
Sonnet 5 $0.00016 $0.00225
Haiku 4.5 $0.00008 $0.00112

Measured 4d ago against content hash 0d99e3e2e04b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

double-checking-before-acting 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.

skills/double-checking-before-acting/SKILL.md · 107 lines

How it starts

The opening of the file, as written. The whole thing — 107 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Double-Checking Before Acting

Overview

A self-check turns a high-stakes action into a careful one. Before you claim success, name the target, the result you expect, when to stop, the action itself, and the check you will run afterward.

Decision contract

  • Claim checked: the target, expected result, and stop condition were named before the action, and the real result was compared against the expected one before claiming success.
  • Artifact observed: the proposed action, target, and authority -> a self-check.md note of action, target, expected/real result, stop condition, evidence, and any mismatch.
  • Decision affected: block -- whether to proceed with or abort the critical action: a big edit, command, public claim, trust change, or release.
  • Failure class: wrong-target-or-unverified-action (acting on an assumed target, or claiming success without comparing the result).
  • Next action: pause and escalate when authority, target, or evidence is unclear; a mismatch halts the action rather than triggering a retry.

When to Use

  • A command can delete, move, publish, release, migrate, or change something outside the repo.
  • An edit touches public claims, where ideas came from, permissions, credentials, dependencies, models, APIs, or the release.
  • An agent is about to make a wide or repeated change, where hitting the wrong target is easy.
  • A quick candidate is about to become a public claim, an accepted version, or a release action.

When Not to Use

  • The task is a tiny local edit with obvious proof.
  • The action only reads data and has no effect on any later decision.
  • The change record already requires a stronger human check before the action.

Inputs

  • The action you mean to take, the exact target, the current phase, and where your authority comes from.
  • The result you expect, the most likely wrong-target mistake, and when to stop.
  • The proof command, review check, or evidence link you will need after the action.

Process

Read the full file on GitHub · 107 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. 4d ago First seen · 107 lines · 78 tokens per session scan A 0d99e3e2e04b

Subscribe to this mod's changes

double-checking-before-acting is a skill published in the GitHub repository FlyFission/nuclear-grade-context-engineering (33 stars, last pushed 25d ago), licensed MIT. It adds 78 tokens to every session and 1,123 once invoked, about $0.0004 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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