Fable Haiku

Run fable-mode execution discipline on Claude Haiku. Routes the task to the @fable-worker-haiku agent, whose definition carries the staged loop with tightened verification (no bare "unverified" allowed) and an escalate-don't-improvise rule.

by mrtooher

Source

Install

Copy install prompt for AI

Natural-language prompt you can paste into any Claude conversation. Claude Code installs it to ~/.claude/skills/fable-mode-haiku/; claude.ai and Claude Desktop adopt it for the current chat and tell you how to save it permanently.

Copy install command

curl -fsSL https://spellbook.build/i/fable-mode-haiku | bash

Drops the file into ~/.claude/skills/fable-mode-haiku/SKILL.md. The script is plain shell — inspect it by dropping the | bash.

Download skill folder

Download .zip

A fable-mode-haiku/ folder with SKILL.md (and any supporting files) — unzip into ~/.claude/skills/.

Benchmarks

This skill isn't in a benchmarked category yet. Set metadata.type in the frontmatter to activate scorecards.

Skill content

---
name: fable-haiku
description: >
  Run fable-mode execution discipline on Claude Haiku. Routes the task to the
  @fable-worker-haiku agent, whose definition carries the staged loop with
  tightened verification (no bare "unverified" allowed) and an
  escalate-don't-improvise rule. Trigger when the user explicitly asks for
  thorough/systematic handling run cheaply or fast ("fable on haiku", "deep work
  mode but cheap", "stage this on haiku"). For bulk mechanical work. Do NOT use
  for tasks needing synthesis — benchmark note: at n=1 the skill's effect on
  Haiku swung both directions (+25 / −17); route quality-critical work to
  fable-sonnet instead.
---

# Fable Mode — Haiku (v3, agent-routed)

v3 change: the worker is a real agent definition (`agents/fable-worker-haiku.md`)
invoked by name. Its system prompt carries the loop, the tightened verification
rule, and the operational rules; this skill only routes.

If a task has one obvious correct approach and fits in a single pass, skip this
loop and do it directly.

## How to run it

1. Confirm `fable-worker-haiku` appears in the available agent types. If not,
   fall back to inline: spawn a general-purpose Haiku agent and pass it the
   rules verbatim from `agents/fable-worker-haiku.md`.
2. Spawn **@fable-worker-haiku** via the Task tool (`subagent_type:
   "fable-worker-haiku"`). Brief it with: the task, the exact output path(s),
   and the pass condition — name the check explicitly; Haiku gets no benefit of
   the doubt on verification.
3. Haiku is cheap: for independent sub-parts, fan out one worker per part and
   merge. Set a ceiling on concurrent workers.
4. Follow with **@fable-verifier** (a second Haiku is cheap; fresh eyes can't
   inherit the worker's blind spots) for anything that will be delivered
   without human review.
5. If a worker escalates ("needs synthesis"), re-route that part to
   fable-worker-sonnet rather than retrying Haiku with a louder prompt.

fable-mode mrtooher fable mode haiku