| name | fable-opus |
| description | 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.
|
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).
