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Agent skill

Fable Opus

by mrtooher in mrtooher/fable-mode

Run fable-mode execution discipline on Claude Opus — one rung below Fable 5.1 on the escalation ladder.

No licenceAuto-check passedProductivity & Automation

Install Fable Opus

skills CLI
$ npx skills add mrtooher/fable-mode --skill fable-opus -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install mrtooher/fable-mode fable-opus --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/mrtooher/fable-mode.git skills-src && mkdir -p .claude/skills && cp -r skills-src/fable-opus .claude/skills/fable-opus && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
fable-opus
GitHub stars
870
Token cost
~868 tokens
SKILL.md length
391 words
Files
1
Skills in repo
7
Repo updated
First seen
Licence
None found

At a glance

Run fable-mode execution discipline on Claude Opus — one rung below Fable 5.1 on the escalation ladder.

  • Works in 5 steps: Confirm the fable agents are installed… → Spawn @fable-orchestrator via the Task… → Do not restate the Core Loop or… → …
  • The user explicitly asks for thorough/systematic/deep work handling on Opus (fable on opus
  • SKILL.md covers How to run it and Known limitation
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Fable Opus is an agent skill from mrtooher/fable-mode. Run fable-mode execution discipline on Claude Opus — one rung below Fable 5.1 on the escalation ladder. Routes the task to the @fable-orchestrator agent (Opus, Write-less), which stages the work, delegates artifact production to @fable-worker-sonnet / @fable-worker-haiku, and cold-checks deliverables with @fable-verifier. Trigger when the user explicitly asks for thorough/systematic/"deep work" handling on Opus ("fable on opus", "stage this on opus", "deep work mode, opus"). Escalate to fable-fable when the…

Its SKILL.md is about 870 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Productivity & Automation, covering Focus and ADHD support. The repository describes itself as: A Claude skill that activates Fable-style agentic behavior: explicit multi-stage planning, sub-agent delegation, and self-verification.

When your agent uses it

  • The user explicitly asks for thorough/systematic/deep work handling on Opus (fable on opus
  • Stage this on opus
  • Ordinary single-pass tasks — and prefer fable-sonnet
  • Fable-haiku when the task doesnt need peak reasoning

Example prompts

  • “deep work”
  • “fable on opus”
  • “stage this on opus”
  • “/fable-opus”

Workflow steps

5 steps, taken from the first numbered list in SKILL.md.

  1. Confirm the fable agents are installed (fable-orchestrator,
  2. Spawn @fable-orchestrator via the Task tool (`subagent_type
  3. Do not restate the Core Loop or operational rules in the briefing — the
  4. When it returns, relay the result, every stage it marked unverified, and its
  5. Mandatory delivery gate: before presenting the result to the user, invoke

What it can do on your machine

Read from SKILL.md and the folder at commit a368f94. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Fable Opus loads about 868 tokens when it runs. Until then it costs about 176 tokens; SKILL.md has 391 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~176
When it runs · the whole SKILL.md, loaded when a task matches
~868

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

Without a licence we can't republish the file, so here is its outline and opening line. It has 391 words (~868 tokens).

“v3 change: delegation is enforced structurally, not requested in prose. The orchestrator is a real agent definition (agents/fable-orchestrator.md) with no Write/Edit tool — it cannot do the work inline, so "spawn a worker" stops being a suggestion the model can…”

— opening of SKILL.md by mrtooher
name
fable-opus

Read the full SKILL.md on GitHub

Files

Just SKILL.md in fable-opus of mrtooher/fable-mode.

Open the folder on GitHubat commit a368f94

Compare with similar skills

Fable Opus next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Fable Opus compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Fable Opus this skillmrtooher/fable-mode870—~868Automated safety check: PassNone
I Have AdhdTanStack/ai3.2k5 repos~1.8kAutomated safety check: PassMIT
Attention Kindalexgreensh/attention-span1.4k—~2kAutomated safety check: PassAGPL-3.0
Remind Meshaheer-00/claude-adhd104—~1.1kAutomated safety check: PassNone
Daily Focus Boardgithub/awesome-copilot40k—~3kAutomated safety check: PassMIT
Attention Controlaaddrick/attention-control118—~3.6kAutomated safety check: PassMIT

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  • Fable Haiku

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  • Fable Sonnet

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Categories

Questions about Fable Opus

What does Fable Opus do?

Run fable-mode execution discipline on Claude Opus — one rung below Fable 5.1 on the escalation ladder. Fable Opus is an agent skill from mrtooher/fable-mode.1 on the escalation ladder.

When should I use Fable Opus?

Fable Opus fits situations like: the user explicitly asks for thorough/systematic/deep work handling on Opus (fable on opus; stage this on opus; ordinary single-pass tasks — and prefer fable-sonnet; fable-haiku when the task doesnt need peak reasoning.

How do I install Fable Opus in Claude Code?

Run `npx skills add mrtooher/fable-mode --skill fable-opus -a claude-code`. Or copy the skill folder (fable-opus in mrtooher/fable-mode) into .claude/skills/fable-opus in your project. Claude Code loads it when a task matches its description.

How do I install Fable Opus in Codex?

Run `npx skills add mrtooher/fable-mode --skill fable-opus -a codex`. Or copy the skill folder (fable-opus in mrtooher/fable-mode) into .agents/skills/fable-opus in your project. Codex loads it when a task matches its description.

Can I use Fable Opus in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add mrtooher/fable-mode --skill fable-opus -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/fable-opus, .gemini/skills/fable-opus, .github/skills/fable-opus and .opencode/skills/fable-opus in your project.

What does Fable Opus need to run?

SKILL.md names no scripts, command-line tools or credentials: Fable Opus is instructions for the agent only.

Does Fable Opus access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Fable Opus safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Fable Opus use?

No licence was found for Fable Opus or its repository. Without one, default copyright applies: ask the author before reusing or redistributing it.

How many tokens does Fable Opus use?

About 868 tokens (SKILL.md is roughly 3.5k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Fable Opus?

Skills that share tags, products or a category with Fable Opus: I Have Adhd (TanStack/ai, 3.2k stars), Attention Kind (alexgreensh/attention-span, 1.4k stars), Remind Me (shaheer-00/claude-adhd, 104 stars) and Daily Focus Board (github/awesome-copilot, 40k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Fable Opus?

mrtooher (a GitHub user) maintains it in mrtooher/fable-mode, which has 870 GitHub stars. The repository holds 7 skills in this directory. The repository was last updated on September 2, 2026.

Source: mrtooher/fable-mode on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.