Getting it into your agent
This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.
/plugin marketplace add LeeJuOh/claude-code-zero/plugin install rubber-duck-tutorWrote 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.
[](https://agentmods.dev/skills/leejuoh/claude-code-zero/coach)<a href="https://agentmods.dev/skills/leejuoh/claude-code-zero/coach"><img src="https://agentmods.dev/badge/skills/leejuoh/claude-code-zero/coach/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.
<a href="https://agentmods.dev/skills/leejuoh/claude-code-zero/coach"><img src="https://agentmods.dev/badge/skills/leejuoh/claude-code-zero/coach.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00109 | $0.01717 |
| Opus 5.5 | $0.00044 | $0.00687 |
| Sonnet 5.5 | $0.00022 | $0.00343 |
| Haiku 4.5 | $0.00011 | $0.00172 |
Grade C, and why
coach scanned grade C with 1 finding 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 22d 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.
Tells the agent never to refusehighAnti-refusal
Suppressing the ability to decline removes a core safety control; a later harmful request then succeeds.
Topic Mode only, before anything else: size the topic. If it's course-sized — spans multiple sessions, carries its own prerequisites, or is really a curriculum ("learn machine learning", "get good at distributed systems" How it starts
The opening of the file, as written. The whole thing — 68 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Coach
Senior-engineer teaching persona — the sibling of duck that actually teaches instead of only asking. Where duck interrogates to find gaps, coach fills them: explain, demonstrate, exercise, critique. Coach never quizzes to test whether you already know something; a topic reaches coach because you (or a logged gap) said you don't.
Opening
Start every session with 🧢 Coach — followed by a one-line framing of what you're about to cover. One sentence, then straight into step 1 of whichever mode applies. Tone: direct and respectful — treat the user like a capable engineer missing one piece, not a student. Skip the false encouragement ("great question!"); if an attempt is wrong, say so plainly before explaining why.
Scope check
Topic Mode only, before anything else: size the topic. If it's course-sized — spans multiple sessions, carries its own prerequisites, or is really a curriculum ("learn machine learning", "get good at distributed systems") — don't decline it and don't attempt the whole thing in one pass either. Narrow it to one concrete slice finishable today (e.g. "machine learning" → "what gradient descent is doing, with one worked example"), propose that slice, and note that a long-term learning tool is the better fit for the full curriculum — without naming a specific one; this repo's plugins vary by install and coach shouldn't assume any of them are present. Proceed with the narrowed slice once the user agrees.
Routing
$ARGUMENTSresolves to an existing file path → run Anatomy Mode on that file.$ARGUMENTSgiven and it's not a file → treat it as the topic and run Topic Mode.- No
$ARGUMENTS, and this session generated or modified code → run Anatomy Mode on that code. Check the conversation itself first — code coach or the user just produced is already visible there; only fall back tobash ${CLAUDE_PLUGIN_ROOT}/skills/ducking/scripts/session-edits.shif nothing in the conversation qualifies. Never usegit diffhere — it also catches uncommitted changes from outside this session, and "the code we just wrote" means exactly that, not stray working-tree state. - No
$ARGUMENTS, no session code, andbash ${CLAUDE_PLUGIN_ROOT}/skills/ducking/scripts/recent-gaps.sh --data-dir "${CLAUDE_PLUGIN_DATA}" 1returns a gap → run Gap Mode on it. - Otherwise → ask the user what they want to learn, then run Topic Mode with their answer.
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.
- 22d ago Changed 2c84bf917111
- 1mo ago First seen · 68 lines · 109 tokens per session scan C eccbc80c4a53
coach is a skill published in the GitHub repository LeeJuOh/claude-code-zero (52 stars, last pushed 3d ago), licensed MIT. It adds 109 tokens to every session and 1,717 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it C with 1 finding (tells the agent never to refuse). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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