Fable Mode — Opus (v3, agent-routed)
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 skip. (Change prompted by field report: prose-level
"you may spawn workers" almost always ran inline on the main thread.)
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
- Confirm the fable agents are installed (
fable-orchestrator,
fable-worker-sonnet, fable-worker-haiku, fable-verifier appear in the
available agent types). If they are not, fall back to the inline method:
spawn a general-purpose Opus agent and pass it the Core Loop, domain
patterns, and operational rules verbatim from the fable-mode skill,
which is installed alongside this one. Do NOT try to read
agents/fable-orchestrator.md — agent files exist only on surfaces that
load an agents/ directory (Claude Code), never on skill-only surfaces
(Cowork), which is exactly where this fallback fires.
- Spawn @fable-orchestrator via the Task tool (
subagent_type: "fable-orchestrator"). Brief it with: the user's task, the output
directory, relevant session context, and any user-set limits (warning
threshold, worker cap, deadline).
- Do not restate the Core Loop or operational rules in the briefing — the
orchestrator's agent definition carries them. Brief the task, not the
method.
- When it returns, relay the result, every stage it marked unverified, and its
recommendations (surfaced scope it did not build). If it reports the task
beyond Opus's capability, offer a fable-fable rerun (Fable 5.1) rather than
retrying Opus.
- Mandatory delivery gate: before presenting the result to the user, invoke
the double-check skill on the finished deliverable. Pass it the
orchestrator's closing
FINAL-COLD-CHECK: line verbatim — yes means
fable-verifier already checked the finished deliverable and double-check
runs the seam check only; intermediates-only, no, or a missing line
means the full panel runs. Do not skip the gate; the user relies on it
instead of re-checking the work themselves.
Known limitation
Write-removal closes the front door, not the side door: the orchestrator keeps
Bash for running verification commands, and Bash can technically create files.
Its definition forbids that use; if audits show it writing through Bash, the
next tightening is removing Bash and routing even check-execution through
workers (cost: one extra hop per check).
1---2name: fable-opus3description: 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 orchestrator reports the task exceeds Opus's ceiling. Do NOT use for ordinary single-pass tasks — and prefer fable-sonnet or fable-haiku when the task doesn't need peak reasoning.4---56# Fable Mode — Opus (v3, agent-routed)78v3 change: delegation is enforced structurally, not requested in prose. The9orchestrator is a real agent definition (`agents/fable-orchestrator.md`) with no10Write/Edit tool — it cannot do the work inline, so "spawn a worker" stops being11a suggestion the model can skip. (Change prompted by field report: prose-level12"you may spawn workers" almost always ran inline on the main thread.)1314If a task has one obvious correct approach and fits in a single pass, skip this15loop and do it directly.1617## How to run it18191. Confirm the fable agents are installed (`fable-orchestrator`,20 `fable-worker-sonnet`, `fable-worker-haiku`, `fable-verifier` appear in the21 available agent types). If they are not, fall back to the inline method:22 spawn a general-purpose Opus agent and pass it the Core Loop, domain23 patterns, and operational rules verbatim from the **fable-mode** skill,24 which is installed alongside this one. Do NOT try to read25 `agents/fable-orchestrator.md` — agent files exist only on surfaces that26 load an `agents/` directory (Claude Code), never on skill-only surfaces27 (Cowork), which is exactly where this fallback fires.282. Spawn **@fable-orchestrator** via the Task tool (`subagent_type:29 "fable-orchestrator"`). Brief it with: the user's task, the output30 directory, relevant session context, and any user-set limits (warning31 threshold, worker cap, deadline).323. Do not restate the Core Loop or operational rules in the briefing — the33 orchestrator's agent definition carries them. Brief the task, not the34 method.354. When it returns, relay the result, every stage it marked unverified, and its36 recommendations (surfaced scope it did not build). If it reports the task37 beyond Opus's capability, offer a fable-fable rerun (Fable 5.1) rather than38 retrying Opus.395. **Mandatory delivery gate:** before presenting the result to the user, invoke40 the **double-check** skill on the finished deliverable. Pass it the41 orchestrator's closing `FINAL-COLD-CHECK:` line verbatim — `yes` means42 fable-verifier already checked the finished deliverable and double-check43 runs the seam check only; `intermediates-only`, `no`, or a missing line44 means the full panel runs. Do not skip the gate; the user relies on it45 instead of re-checking the work themselves.4647## Known limitation4849Write-removal closes the front door, not the side door: the orchestrator keeps50Bash for running verification commands, and Bash can technically create files.51Its definition forbids that use; if audits show it writing through Bash, the52next tightening is removing Bash and routing even check-execution through53workers (cost: one extra hop per check).
mrtooher