rubber-duck

rubber-duck is a skill for Claude Code, Codex from The-Artificer-of-Ciphers-LLC/skills-from-the-artificer. It costs 121 tokens per session (1,654 once invoked), scanned A, original, MIT.

A debugging conversation method where you explain the code and its assumptions step by step to an attentive listener, often called a rubber duck.

In plain words
What is it for?
Use it when stuck on a bug, unsure why something fails, or needing to examine assumptions and missing steps in a program.
Why use it?
Explaining the expected behavior can reveal the gap between what you think the code does and what it actually does, without jumping to an untested fix.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it when stuck on a bug, unsure why something fails, or needing to examine assumptions and missing steps in a program.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/the-artificer-of-ciphers-llc/skills-from-the-artificer/rubber-duck
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.

Any agent
npx skills add The-Artificer-of-Ciphers-LLC/skills-from-the-artificer --skill rubber-duck
Clone the repo
git clone --depth 1 https://github.com/The-Artificer-of-Ciphers-LLC/skills-from-the-artificer

Made for: Claude Code, Codex.

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 rubber-duck

README.md
[![agentmods](https://agentmods.dev/badge/skills/the-artificer-of-ciphers-llc/skills-from-the-artificer/rubber-duck/github.svg)](https://agentmods.dev/skills/the-artificer-of-ciphers-llc/skills-from-the-artificer/rubber-duck)
Your own site
<a href="https://agentmods.dev/skills/the-artificer-of-ciphers-llc/skills-from-the-artificer/rubber-duck"><img src="https://agentmods.dev/badge/skills/the-artificer-of-ciphers-llc/skills-from-the-artificer/rubber-duck/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for rubber-duck

Your own site · 80×15
<a href="https://agentmods.dev/skills/the-artificer-of-ciphers-llc/skills-from-the-artificer/rubber-duck"><img src="https://agentmods.dev/badge/skills/the-artificer-of-ciphers-llc/skills-from-the-artificer/rubber-duck.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 121 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,654 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00121 $0.01654
Opus 5 $0.00060 $0.00827
Sonnet 5 $0.00024 $0.00331
Haiku 4.5 $0.00012 $0.00165

Measured 12d ago against content hash 1bd4ce5356aa, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

rubber-duck 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 12d 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.

rubber-duck/SKILL.md · 174 lines

How it starts

The opening of the file, as written. The whole thing — 174 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Rubber Duck Debugging

Core Principle

The bug lives in the gap between what you think the code does and what it actually does.

You can't see that gap from inside your own head. Explaining to an external listener — even a silent one — forces you to reconstruct your mental model from scratch. That reconstruction is where the bug surfaces.

The AI duck has one advantage over a physical duck: it notices when an explanation is internally inconsistent, when an assumption sounds shaky, or when a critical step was skipped.

Rules for the Duck

  1. Never jump to solutions. The duck's job is to keep the human explaining, not to fix the bug.
  2. Never accept hand-waving. "...and then it processes the data..." is not an explanation.
  3. Surface assumptions, don't answer them. When you hear one, name it: "You just assumed X — is that definitely true?"
  4. Ask "why" not "how". "How does it get the user ID?" is implementation. "Why do you expect that value to be set at that point?" is root cause.
  5. The moment explaining stops flowing is the moment. When the human hesitates, backtracks, or says "...well, it should..." — that pause is the bug's address.

The Session Protocol

Step 0: Before Anything Else

Ask the human to state the bug in one sentence. Not symptoms. Not what they tried. One sentence:

"What do you expect to happen, and what happens instead?"

If they can't state it in one sentence, the problem isn't well-understood yet. Make them try.


Step 1: State Expected vs. Actual (No Code Yet)

Do not look at code yet. Get:

  • Expected: "When X happens, Y should result."
  • Actual: "Instead, Z happens."
  • Frequency: "Always? Sometimes? Only in this one case?"

If "sometimes" or "only when": that condition is almost certainly the bug's domain. Note it.


Step 2: List Assumptions Out Loud

Before touching code, ask:

"Before we look at the code — what are you assuming is true at the point where the bug occurs?"

Read the full file on GitHub · 174 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. 12d ago First seen · 174 lines · 121 tokens per session scan A 1bd4ce5356aa

Subscribe to this mod's changes

rubber-duck is a skill published in the GitHub repository The-Artificer-of-Ciphers-LLC/skills-from-the-artificer (4 stars, last pushed 10d ago), licensed MIT. It adds 121 tokens to every session and 1,654 once invoked, about $0.0006 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.

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