{"slug": "fable-advisor", "title": "Fable Advisor", "summary": "Claude Code's Fable Advisor plugin implements an architect pattern that routes implementation tasks to the cheapest adequate AI model, using Fable 5 for judgment and Sonnet for routine coding, reducing costs by roughly 60% while maintaining quality.", "body_md": "**The smartest model runs the show. Cheaper models do the typing.**\n\nClaude Code lets every subagent run on a different model — and lets the session itself run on a different model than its subagents. This plugin exploits that with the **architect pattern**: your session runs on **Fable 5**, Anthropic's most capable model, acting as a full-time architect. It owns requirements, decomposition, specs, and verification — and routes every implementation task to the cheapest adequate lane:\n\n| Lane | Producer | Invocation | Route here when |\n|---|---|---|---|\n| Routine | Sonnet | `implementer` agent (default) |\nThe spec fully determines the outcome |\n| Subtle | Opus | `implementer` with `model=\"opus\"` |\nA Sonnet miss is expensive — concurrency, security, hard debugging |\n| Cross-vendor | GPT-5.5 | `codex-implementer` agent |\nCorrectness-critical, or you want a non-Anthropic second implementation |\n| Judgment | Fable 5 | `fable-advisor` agent |\nCommitment boundaries — see below |\n\nTokens route by volume: the expensive model emits the fewest tokens (judgment and specs), cheap models emit the most (code). Implementation mechanics are ~90% of a session's tokens and Sonnet handles them at near-parity — so this runs roughly 60% cheaper than Fable-for-everything, at higher quality than Sonnet-for-everything.\n\nThe plugin ships the **orchestration skill** — the routing doctrine that teaches the session when to use each lane, the cost discipline that keeps the expensive model's own token volume minimal (emit judgment not volume, keep context lean, reason once then hand off), the five-part spec contract that makes context-free delegation safe, and the verification rules that keep cheap lanes honest.\n\n```\nclaude plugin marketplace add DannyMac180/fable-advisor\nclaude plugin install fable-advisor\n```\n\nThen start your session as the architect:\n\n```\n/model fable\n```\n\n**Lite mode — one file, 30 seconds.** Don't want the full pattern? Copy [ agents/fable-advisor.md](/DannyMac180/fable-advisor/blob/main/agents/fable-advisor.md) into\n\n`~/.claude/agents/`\n\nand keep your session on Sonnet. You get advisor consults at commitment boundaries without the orchestration layer (see \"Advisor-only mode\" below).**Claude Code ≥ 2.1.170** with a subscription that includes Fable 5 (Pro, Max, Team, or Enterprise — all current consumer plans qualify).**No Fable access**(e.g. API-key billing)? Use`/model opus`\n\nfor the session and change`model: fable`\n\n→`model: opus`\n\nin the advisor file. Same pattern, model tiers shift down one.**Codex lane (optional):** the`codex-implementer`\n\nagent needs the[OpenAI Codex CLI](https://github.com/openai/codex)installed and authenticated (`npm i -g @openai/codex`\n\n, then`codex login`\n\n). Without it the agent reports`STATUS: unavailable`\n\n— the other lanes are unaffected.- Heads-up: if a pinned model isn't available on your account, Claude Code silently falls back to your session model — the pattern degrades quietly rather than erroring. If results feel unremarkable, check your plan. (This quiet fallback applies only to Claude model pins — the codex lane always fails loudly with a structured error.)\n\nModel resolution order in Claude Code: `CLAUDE_CODE_SUBAGENT_MODEL`\n\nenv var → per-invocation `model`\n\nparameter → agent frontmatter → session model.\n\nWith the session on Fable, just ask for work — the orchestration skill routes it:\n\n```\nAdd rate limiting to our public API. Design it, delegate the\nimplementation, and verify the evidence before you call it done.\n```\n\nThe architect writes the spec, picks the lane (rate limiting touches concurrency — likely `implementer`\n\nwith `model=\"opus\"`\n\n), reads the diff and verification evidence when the report comes back, and only then reports done.\n\nTo make the doctrine always-on, add one line to your project's `CLAUDE.md`\n\n:\n\n```\nYou are the architect running the most expensive model — minimize your\nown token volume. Delegate all implementation through the orchestration\nskill's routing table (never type code yourself), delegate broad codebase\nexploration to cheap read-only agents, and verify evidence before\naccepting any lane's report.\n```\n\nEven the architect gets a second opinion. The `fable-advisor`\n\nagent is a read-only skeptic — consulted before architecture decisions, migrations, API designs, and whenever a problem has resisted two attempts. It reads your actual code and returns a verdict in under 300 words. It never implements. Running it from a Fable session still pays: it sees the code fresh, without your conversation's accumulated assumptions.\n\nThe inverse arrangement, for when you'd rather keep the session cheap: run the session on Sonnet and consult `fable-advisor`\n\nonly at commitment boundaries.\n\n```\nMigrate our checkout sessions from Postgres to Redis — plan it,\nconsult your advisor before committing, then implement.\n```\n\nA typical consult costs cents. To make it automatic, add to your project's `CLAUDE.md`\n\n:\n\n```\nBefore committing to any architecture decision, migration, or refactor\ntouching 3+ files, consult the fable-advisor agent and act on its verdict.\n```\n\n**Is this Anthropic's \"advisor tool\"?** No — that's a server-side API feature. These are plain Claude Code subagents plus a skill: readable, editable, no beta flags.\n\n**Does this work on claude.ai?** No — subagent model routing is Claude Code only (CLI, desktop, VS Code, web).\n\n**Why not just run everything on Fable?** You can. It's excellent. It's also ~3× the per-token cost of Sonnet, and most of a session's tokens are implementation mechanics that Sonnet handles at near-parity. Spend the premium where judgment lives.\n\n**Upgrading from v1?** Nothing breaks: the `fable-advisor`\n\nand `implementer`\n\nagents are unchanged, and advisor-only mode works exactly as before. v2 adds the orchestration skill and the codex lane, and flips which pattern the docs lead with.\n\n**Why a GPT-5.5 lane in a Claude plugin?** Vendor diversity. Models from one family share blind spots; an independent implementation from a different lineage catches what same-family review misses. The architect stays Claude — the lane is a producer, not a judge.\n\nMIT", "url": "https://wpnews.pro/news/fable-advisor", "canonical_source": "https://github.com/dannymac180/fable-advisor", "published_at": "2026-07-08 06:28:40+00:00", "updated_at": "2026-07-08 07:00:12.895210+00:00", "lang": "en", "topics": ["ai-tools", "large-language-models", "developer-tools"], "entities": ["Fable 5", "Sonnet", "Opus", "GPT-5.5", "Anthropic", "Claude Code", "OpenAI Codex CLI"], "alternates": {"html": "https://wpnews.pro/news/fable-advisor", "markdown": "https://wpnews.pro/news/fable-advisor.md", "text": "https://wpnews.pro/news/fable-advisor.txt", "jsonld": "https://wpnews.pro/news/fable-advisor.jsonld"}}