# Double Check

Automatic final verification pass on completed deliverables.

- Repository: https://github.com/mrtooher/fable-mode (882 stars)
- Category: AI and agents
- License: see repository
- Last updated: 2026-10-24
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add mrtooher/fable-mode --skill double-check -g -a claude-code -y`
Codex: `npx skills add mrtooher/fable-mode --skill double-check -g -a codex -y`
Cursor: `npx skills add mrtooher/fable-mode --skill double-check -g -a cursor -y`
Gemini CLI: `npx skills add mrtooher/fable-mode --skill double-check -g -a gemini-cli -y`

## Description

Automatic final verification pass on completed deliverables. Runs at the end of every fable-mode run, those skills invoke it before delivery. Also triggers when the user says \"double check this\". Uses a panel of fresh checker agents when spawning is authorized (otherwise a cold self-check) to verify the finished output, not to redo the task. Any FAIL gets fixed and re-checked before delivery.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Double Check

Family version: v6 (2026-10-10).

Automatic verification pass on a *finished* deliverable. The user should never have to
re-check work themselves, this skill is that re-check.

This skill is both the **gate** (when verification runs, on what, and what happens to a
FAIL) and the **mechanism** (how to brief a cold verifier so it checks the world instead
of your argument). Both live here, there is no companion skill to load.

## What it is and is not

- It verifies **outputs**, it does not re-run the task. A full second run produces a
  second divergent version and a comparison problem; attacking the finished artifact
  catches the same errors at a fraction of the cost.
- It runs **after** the work is complete and **before** it is delivered.
- It never runs on its own output. One double-check per deliverable. Fixes triggered by
  a FAIL get their specific failed check re-run, not a whole new panel. No recursion.

## When it runs

1. **Automatically** at the end of any fable-mode run (fable-mode, fable-opus,
   fable-sonnet). Those skills call this one as their final delivery gate. Exception: if
   a fable run already executed a cold verification of the final deliverable, do not
   duplicate it, run only the seam check (section "Check the synthesis seam") and skip
   the rest. Do not infer this from the narrative: the run closes its report with a
   `FINAL-COLD-CHECK:` line. `yes` → seam check only. `intermediates-only`, `no`, or no
   line at all → run the full checks (panel or self-check mode, per below). Absence of
   the line is never evidence that the check happened.
2. **On request**: "double check this", "verify this", "make sure this is right".

The rest: https://github.com/mrtooher/fable-mode/blob/HEAD/double-check/SKILL.md