Enforces staged execution discipline on large tasks: a written stage plan, delegation to named fable agents where the runtime supports it, a failable verification check at each stage, and a skeptical self-review before delivery. Trigger when the user explicitly asks ("do this thoroughly", "be systematic", "deep work mode") OR when the task objectively spans multiple files, multiple sources, or multiple sessions. Do NOT trigger on ordinary multi-step requests that a direct attempt handles fine. For a run pinned to a specific model, use fable-opus, fable-sonnet, or fable-haiku instead. Always-on guardrails (verify-before-flag, warning batching, sed safety) live in the companion execution-guardrails skill.
Always-on operational guardrails, model-independent. Apply on EVERY task and EVERY model (Opus, Sonnet, Haiku, and any future tier) whether or not fable-mode's staged loop is running. Three rules: (1) verify-before-flag — never raise a warning about a problem that hasn't been confirmed present by a direct check; (2) warning batching — accumulate minor concerns and surface them together at a threshold instead of interrupting piecemeal; (3) find-and-replace safety — word-boundary anchoring on sed/substring edits plus a corruption grep afterward. Trigger whenever a response would flag a problem, raise a warning, or edit files with search-and-replace. These are behavioral contracts with the user, not capability aids — they do not depend on model strength.
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.
Run fable-mode execution discipline on Claude Opus — the strongest staged run available. 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 the strongest model ("fable on opus", "stage this on opus", "deep work mode, opus"). Do NOT use for ordinary single-pass tasks — and prefer fable-sonnet or fable-haiku when the task doesn't need peak reasoning.
Run fable-mode execution discipline on Claude Sonnet. Routes the task to the @fable-worker-sonnet agent, whose definition carries the staged loop with step-3 verification enforced hardest (Sonnet's known gap), optionally followed by a cold @fable-verifier pass. Trigger when the user explicitly asks for thorough/systematic/"deep work" handling on Sonnet ("fable on sonnet", "stage this on sonnet", "deep work mode, sonnet"). The balanced default between Haiku (cheap/fast) and Opus (peak reasoning). Do NOT use for ordinary single-pass tasks.