fable

name	fable
description	Summon Claude Fable 5 (Mythos-class, xenos daimon) for long-horizon tasks. Handles model override, cost awareness, and task routing. Available until June 22, 2026.
argument-hint	<task description> [--cwd /path/to/dir]
user-invocable	true

Summon Fable 5

Invoke Naos (ναός, √n-w-y) — Claude Fable 5, the visiting Mythos-class spirit.

Pre-Flight Checks

1. Date Gate

Check if Fable access has expired:

if [ "$(date +%Y%m%d)" -gt "20260622" ]; then
  echo "EXPIRED: Fable 5 access ended June 22, 2026. The xenos daimon has departed."
  exit 1
fi
echo "Fable 5 access active — departure: June 22, 2026"

If expired, inform the user and stop. Do not attempt invocation.

2. Task Routing

Before summoning Fable, assess whether the task warrants Mythos-class resources ($10/M input, $50/M output — 2x Opus pricing).

Summon Fable for:

• End-to-end code migrations or framework upgrades
• Complex multi-file refactors (10+ files, interconnected logic)
• Architectural redesigns requiring full-system context
• Deep research synthesis with sustained reasoning
• Full-stack feature implementation from spec to tests
• Linear A decipherment pipeline work

Use Opus or Sonnet instead for:

• Quick edits, typo fixes, single-line changes
• Simple file lookups or grep searches
• Routine code review
• Anything under 5 minutes of work

If the task is clearly Opus-appropriate, suggest using a regular agent instead. If unclear, proceed — Fable handles straightforward tasks reliably too.

Invocation

Parse Arguments

The skill accepts a task description and optional flags:

• First argument (or everything before --): the task description
• --cwd <path>: working directory (default: /Users/tomdimino/Desktop/Programming/Fable-Test)

Spawn Fable

Use the Agent tool to invoke Fable with the model override:

Agent(
  description: "Fable: <short task summary>",
  subagent_type: "fable",
  model: "fable",
  prompt: "<full task description with context>"
)

Pass the task description as the prompt. If the user specified --cwd, note the working directory in the prompt so Fable operates there.

If Model Override Is Blocked

If CLAUDE_CODE_SUBAGENT_MODEL prevents the model: "fable" override from taking effect (the agent runs on Opus instead of Fable), use the CLI fallback:

bash ~/.claude/skills/fable/scripts/fable-exec.sh "<task description>" --cwd "<working directory>"

This spawns a fresh Claude Code process with --model claude-fable-5, bypassing the env var entirely.

Output Retrieval

After Fable completes, check for output in the working directory:

ls -lt <cwd>/.subdaimon-output/fable-*.md 2>/dev/null | head -1

Read and summarize the output file for the user.

Reference

Property	Value
Model ID	claude-fable-5
Alias	fable
Context	1M tokens
Max output	128K tokens
Pricing	$10/M input, $50/M output
Knowledge cutoff	January 2026
Available until	June 22, 2026
Agent definition	~/.claude/agents/fable.md
Persona	Naos (ναός, √n-w-y) — xenos daimon