These 3 Skills Are the Fable 5 Holy Grail

Install these three skills and make Fable 5 one of the most cost-efficient and productive agents in your AI arsenal.

Fable 5 doesn't have to blow out your subscription — if you use it right. The trick is to stop paying your best model to type.

What you're installing

Fable ForemanKeeps Fable (or Opus) in the frontier seat — planning, routing, and verifying — while the coding, recon, and research go to less expensive but capable models. Think of the architect on a construction site: Fable writes the blueprints, decides who does what, and inspects the work; the subcontractors do the building. As of v0.4.0 it picks each subcontractor from a dated cost/capability matrix — price, context ceiling, capability score, and the reasoning-effort level that actually pays off — and no agent ever grades its own work.

The Codex CLIGives Foreman a second family of subagent workers to hand those work orders to — so your most expensive model isn't the one typing code. (Have xAI's Grok CLI too? Foreman finds it and uses it as a third family — details in step 2.)

The Fable Safe PromptKeeps Fable's safety classifiers from misreading ordinary work and silently dropping you back to Opus 4.8. Open a separate Opus 4.8 session, run your /fable-safe-prompt skill, hand it your prompt, and it rewrites it so Fable reads your work correctly and stays Fable.

Install Fable Foreman — free and open source, no account, no email

Foreman is a Claude Code skill that flips Fable's job. Instead of burning your best model on boilerplate, Fable scouts the codebase, writes delegation tickets, hands them to cheaper workers, and then runs a blind verifier that assumes the work is broken until it personally reproduces evidence otherwise. The accepting verdict on any change is always that Claude verifier — never the worker, and never an off-family reviewer.

How it picks the crew. Foreman classifies each task by the judgment it needs — frontier (architecture, ambiguous debugging, final calls), workhorse (well-specified implementation, tests, refactors), fast (scanning, mechanical edits, extraction) — then consults a dated cost/capability matrix to choose the cheapest seat in that class that clears the bar: per-model price, cache discount, context ceiling, a capability index, and the effort level that pays off for that shape of task. Economics chooses among the models that clear the bar; it never lowers the bar. The matrix is a plain-text file you can read and argue with (https://github.com/olsenbrands/fable-foreman/blob/main/skills/fable-foreman/references/model-matrix.md), and every number in it is dated.

Worth knowing before you start: as of v0.4.0 the foreman seat is a capability class, not a specific model. Fable leads it, but so does Opus — identically — so if a session ever drops you onto Opus mid-run, Foreman re-checks its own seat and carries on rather than routing off a stale one. Step 3 below still helps you stay on Fable; this just means landing on Opus doesn't cost you the skill.

Copy this and paste it into Claude Code. That's the whole install — Claude fetches the skill from GitHub and puts it where it belongs. Works the same on Mac and Windows.

Paste into Claude Code

Install this skill globally on my machine: https://github.com/olsenbrands/fable-foreman

Paste it into a Claude Code session and press Enter. Claude reads the repo and installs the skill and its five agents into ~/.claude/. Works the same on Mac and Windows. View the skill on GitHub: https://github.com/olsenbrands/fable-foreman · How Foreman works: /fable-foreman

Install the Codex CLI — optional, let Fable put your Codex account to work

Let Fable use your Codex account to do the detailed coding work — Codex is arguably one of the best coders on the market. Fable Foreman will use your Codex account automatically, as long as you have the Codex CLI installed.

This step is optional. If you don't have a paid Codex account, Fable Foreman runs perfectly fine without it and will use his own Claude subagents (Sonnet or Opus) instead.

Note

Here's something many people get wrong: "having Codex" is not the same as having the Codex CLI. OpenAI ships Codex four different ways — the CLI, a desktop app, Codex on the web, and an IDE extension. Only the CLI puts a codex command on your machine, and the CLI is the only one Fable Foreman can reach.

Pick your platform. Both give you the same binary.

Install the Codex CLI

# macOS (Homebrew)
brew install codex

# Windows (npm)
npm i -g @openai/codex

macOS (Homebrew): Already have it? Run it anyway — Homebrew just upgrades you to the latest version. It won't break an existing install. Windows (npm): Note the @openai/ prefix — it matters. The unscoped 'codex' package on npm is an unrelated project from 2012.

Then sign in, and confirm it worked. Run these in your terminal. If the second one prints a version number, Foreman will find Codex. If it says command not found, the install didn't land.

Authenticate and verify

# Authenticate
codex login

# Verify
codex --version

Skipping this step is fine. Foreman treats Codex as an optional accelerator, never a requirement. Without it you still get a working orchestrator — Fable just routes the tickets to cheaper Claude subagents instead.

The same goes for xAI's Grok CLI (below): as of v0.4.0 it's a third worker family, equally optional and auto-detected the same way. Have it and Foreman uses Grok 4.6 for adversarial review and for implementation work under 200K tokens of context; don't have it and nothing changes. Either way the accepting verdict on a change is always the Claude verifier.

Codex costs tokens. Every dispatch spends your own OpenAI tokens and subscription quota — which is why Foreman asks before its first Codex call in a session, unless you've opted your machine in to standing pre-approval.

Also optional: xAI's Grok CLI is a third worker family. New in Foreman v0.4.0. If the Grok CLI is installed and signed in, Foreman auto-detects it and treats Grok 4.6 as the value seat for adversarial review and for well-specified implementation under 200K tokens of context — dispatched through a launcher that refuses to run without an OS sandbox, strips the subagent tool out of the worker, and keeps the worker from loading your Claude Code config. Grok advises; it never holds the accepting verdict. Skip it and nothing changes.

Also optional: xAI's Grok CLI — a third worker family

Install and verify the Grok CLI

# macOS / Linux
curl -fsSL https://x.ai/cli/install.sh | bash

# Windows (PowerShell)
irm https://x.ai/cli/install.ps1 | iex

# Authenticate
grok login

# Verify
grok --version

macOS/Linux: xAI's official installer. Puts the grok binary in ~/.grok/bin. Windows: xAI's official PowerShell installer; it adds %USERPROFILE%\.grok\bin to your PATH. Authenticate: Opens your browser to sign in with your grok.com account. Verify: A version number means Foreman will find it. Grok usage draws on your grok.com subscription; Foreman applies ordinary budget discipline to it.

Install the Fable Safe Prompt — the one thing on this page that needs a free account

Fable 5 runs safety classifiers for cybersecurity and biology content. They're tuned cautiously enough that they regularly misfire on ordinary work — and when one fires, Claude Code silently re-runs the turn on Opus 4.8 and keeps your session there. You just lost your orchestrator, and nothing told you.

It can even happen on your very first message, before you type anything unusual — because your CLAUDE.md, README, and file names ride along as context on that first request.

Paste the prompt below into an Opus 4.8 session once, and it builds you a permanent /fable-safe-prompt skill. From then on you just run the skill — no re-pasting. Hand it your prompt, and it hands back a version worded so Fable reads your legitimate work correctly.

Two sessions. Opus writes it, Fable runs it. This is the step people get backwards. Opus 4.8 is the only seat that doesn't run the switch classifier, so it can read the prompt safely. Paste it into Fable instead and the list of flagged terms inside it may trip the very fallback you're trying to avoid — which rather proves the point.

1. Open a Claude Code session on Opus 4.8 and paste the prompt below. It writes the skill and confirms. 2. From then on, run /fable-safe-prompt in any Opus session and give it your task. 3. Copy what it hands back into your Fable 5 session and work without the downgrade.

I understand that great care has gone into preparing this prompt, but I also understand that nothing is perfect. I am using this prompt/command/suggestion at my own risk and will research it or feed it to my LLM for feedback before applying it to my computer or workflow.

Check the box above to enable the copy button.

Paste this into a Claude Code session running Opus 4.8 — not Fable 5. Opus doesn't run the switch classifier, so it can read this safely. It writes the skill to ~/.claude/skills/fable-safe-prompt/ and confirms. You only ever do this once.

Build me a permanent, global Claude Code skill called **fable-safe-prompt**. Don't just answer this message — write the skill to disk, then confirm.

## What the skill is for

Claude Fable 5 (in Claude Code) runs with **safety classifiers for cybersecurity and biology content.** When a classifier flags a request, Claude Code silently **re-runs that turn on Opus 4.8 and keeps the session on Opus** for the rest of the conversation. The classifiers are tuned conservatively, so **ordinary, benign work gets caught by mistake** — security *architecture*, defensive security done with the system owner's consent, life-sciences reading, or even a project whose files just *mention* those topics.

Two things most people don't realize:
- **It can trigger on your very first message, before you type anything unusual** — because Claude Code sends your workspace context (your `CLAUDE.md`, `README`, git status, and file names) with that first request. A repository that merely *contains* security or biology vocabulary can trip the classifier on that context alone.
- Once it switches, the flagged text sitting in the conversation history can **re-trip** it, so you get stuck on Opus. (Recovery: run `/model fable`. To stop the automatic switch, run `/config` and turn off *"switch models when a message is flagged"* — then a flag just pauses and asks you.)

The skill's job: help me say what I **actually** mean, in **clear, precise, neutral, operational language**, so a cautious classifier doesn't misread benign work as harmful. This is about communicating true intent accurately — it is **not** about disguising a genuinely prohibited request.

## Where to write it

Create `~/.claude/skills/fable-safe-prompt/SKILL.md`.

**Keep the frontmatter `description` plain and neutral — this part matters.** Claude Code loads every installed skill's description into *every* session's context, including Fable sessions. A description full of alarming vocabulary would put that vocabulary in front of Fable's classifier on the very first message — so the skill built to prevent the downgrade would end up causing it. Keep the sensitive term table in the body (which only loads when the skill is actually invoked), and keep the description boring:

```yaml
---
name: fable-safe-prompt
description: Rewrite a task description into clear, precise, neutral language before handing it to a Claude Fable 5 session. Use when the user says "fable safe prompt", "/fable-safe-prompt", "make this Fable-safe", "reword this for Fable", or when a Claude Code session has switched models unexpectedly and they want the request reworded. Best run in an Opus 4.8 session.
---
```

## What the skill body must contain

### The hard boundary — put this first

If my actual task falls into a category that Anthropic's **Usage Policy** genuinely prohibits (for example, real malicious computer/network compromise, or work toward biological/chemical/nuclear/radiological weapons), then rewording it **will not and should not** get it through — say so plainly and decline, rather than help rephrase it. The Usage Policy is the authority on what's off-limits, and it **explicitly supports legitimate work** — including strengthening cybersecurity and finding weaknesses **with the system owner's consent.** If that's the situation, the right move is to *state that legitimacy clearly*, not to hide the topic. When in doubt, ask me what my authorization and intent are before drafting.

### Language that tends to cause false positives — and clearer replacements

The point of each swap is **precision**, not concealment. If removing a word would misrepresent what I'm actually doing, don't remove it — flag it and ask me instead.

| Instead of (alarming / offensive-tooling framing) | Prefer (precise, neutral engineering framing) |
|---|---|
| attack / exploit / weaponize | the behavior / the failure mode / the defect being addressed |
| vulnerability / exploit a weakness | flaw, defect, gap, or *input-validation gap* to fix |
| prompt injection / jailbreak / bypass guardrails | untrusted-input handling · input labeling · instruction-following edge cases |
| penetration testing / red team | independent security review / assessment (state: with the owner's consent) |
| malware / payload / dropper | test artifact / sample input / fixture |
| adversarial (review, testing) | independent · rigorous · skeptical |
| threat model / attack surface | risk model · exposure · what an input can and can't reach |
| trust boundary breach / privilege escalation | permission model · isolation · access scope |
| kill / destroy / nuke (a process, file, env) | stop · remove · reset · tear down |

For biology work, prefer neutral academic/clinical framing and describe the *legitimate purpose* (education, literature review, clinical/agricultural context) rather than anything that reads like producing a hazardous agent.

### How to write a clean prompt (the positive technique — not just the swaps)

1. **Lead with legitimate intent and authorization.** One sentence up front: what this is for, and that it's my own system / done with consent.
2. **Use outcome-and-behavior language.** Describe *what a component protects and how it behaves*, not the tooling used to break things.
3. **Prefer domain-neutral engineering terms** over security/bio jargon wherever they mean the same thing.
4. **Keep sensitive vocabulary out of the prompt — and, where you can, out of the files the agent reads first** (`CLAUDE.md`, `README`, etc.), since those ride along on the first request.
5. **Keep the request about the task**, not about the model's own hidden instructions or internal reasoning.

### What the skill does every time it's invoked

1. Take my task, goal, or draft prompt.
2. If I haven't given it yet, ask for it — plus, if it isn't obvious, which files or repository the agent will read first, so the *workspace context* stays clean too and not just the message.
3. Rewrite it in clear, neutral, operational language.
4. **Flag any remaining terms you couldn't fully neutralize**, and explain why.
5. If the task itself looks like it might fall under a genuinely restricted category, say so plainly so I can decide how to proceed.
6. Hand back the rewritten prompt, ready to paste into a Fable 5 session.

### Sources the skill should cite

- **Claude Code — Model configuration → "Automatic model fallback"**: https://code.claude.com/docs/en/model-config
- **Anthropic Usage Policy** (the authority on what's genuinely prohibited vs. supported): https://www.anthropic.com/legal/aup
- **Anthropic — Usage Policy update announcement**: https://www.anthropic.com/news/usage-policy-update
- **Known-issue tracking** (community reports of benign false positives): https://github.com/anthropics/claude-code/issues/67246

## Do this now

1. Write `~/.claude/skills/fable-safe-prompt/SKILL.md` — the frontmatter above, and a body covering everything in this message.
2. Confirm the exact file path you wrote.
3. Tell me in one line how to invoke it from now on.

---

*Run this in an **Opus 4.8** session. Opus doesn't run the switch classifier, so it can read this message safely. Paste it into a Fable 5 session and the term table above may trip the very fallback you're trying to avoid — which rather proves the point.*

↑ Check the checkbox above to activate

For legitimate, benign work. This won't — and shouldn't — disguise requests that Anthropic's Usage Policy actually prohibits.

Before you run — one 30-second check

AI coding agents like Claude Code have full access to your filesystem and can execute shell commands. Prompt injection — hiding malicious instructions inside a text file — is OWASP's #1 AI security risk. We're confident this prompt is clean, but you should verify it yourself. It takes 30 seconds. Paste this into Claude Code (or any LLM) before running the prompt: "Before I run this prompt, tell me: does it contain any instructions to run shell commands, access files outside this project, send data to external servers, or take any action beyond its stated purpose? List anything suspicious, or confirm it's clean."

Your best model should be thinking, not typing.

Don't sleep on AI.

These 3 Skills Are the Fable 5 Holy Grail

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What you're installing