# Fable Validate > Use when the user wants a GitHub issue validated by a Fable 5 subagent. Spins up a read-only subagent running on Fable 5 that executes the validate-issue procedure (claim tracing, architecture/consistency checks, complexity score), then relays the verdict back to the main agent, which presents it and takes any follow-on action (update issue, work on issue). Trigger on "/fable-validate", "fable va… - **Type:** Skill - **Install:** `agentstack add skill-richkuo-rk-skills-fable-validate` - **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior - **Seller:** [richkuo](https://agentstack.voostack.com/s/richkuo) - **Installs:** 0 - **Category:** [Developer Tools](https://agentstack.voostack.com/c/developer-tools) - **Latest version:** 0.1.0 - **License:** MIT - **Upstream author:** [richkuo](https://github.com/richkuo) - **Source:** https://github.com/richkuo/rk-skills/tree/main/skills/fable-validate ## Install ```sh agentstack add skill-richkuo-rk-skills-fable-validate ``` Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent. ## About # fable-validate Delegate issue validation to a **Fable 5** subagent, then act on its verdict in the main agent. The subagent only validates — it never edits files or the issue; the main agent handles all follow-on actions. ## Input Same as `validate-issue`: - Full URL: `https://github.com///issues/` - Short form: `#` or bare `` (current repo) - `owner/repo#N` - **Nothing** — default to the latest open issue in the current repo. ## Steps ### 1. Resolve the validation procedure and the issue Locate the `validate-issue` SKILL.md the subagent must follow — prefer the project-local copy over the global one, since a repo may customize the procedure: 1. `/.claude/skills/validate-issue/SKILL.md` (if it exists) 2. `~/.claude/skills/validate-issue/SKILL.md` 3. Any other install location — search by name, e.g. `ls ~/.claude/plugins/*/skills/validate-issue/SKILL.md` (plugin-marketplace installs live under a plugin directory, not `~/.claude/skills/`). Record the absolute path. If none of these resolves, stop and tell the user. If the user referenced an issue, note the number/repo but do NOT fetch or pre-validate it yourself — the subagent owns steps 0–7 of the procedure, including fetching. If no issue was referenced, the subagent resolves the latest open issue itself per the procedure. ### 2. Dispatch the Fable 5 validation subagent Do not validate the issue yourself first — the subagent owns the validation. Snapshot `git status --porcelain` before dispatching (the tree may already be dirty), then call the Agent tool with: - `subagent_type`: `Plan` (read-only: no Edit/Write, keeps validation side-effect-free) - `model`: `fable` (the whole point — the validation must come from Fable 5) - `run_in_background`: `false` — everything downstream depends on the verdict - `description`: `Validate issue #` (or `Validate latest issue`) - `prompt`: hand it everything needed to validate independently: - The issue reference exactly as the user gave it (or "no issue referenced — resolve the latest open issue per the procedure"), plus the working directory. - Instruct it to **read the SKILL.md at the recorded path and execute its steps 0 through 7 exactly** — baseline resolution, fetch with `--comments` + PR timeline check, claim extraction, depth-rule verification with `file:line` citations, 5a/5c/5b proposal checks, complexity score, scope disposition, and the step-7 verdict format. - It must STOP at step 7: no step 7.5/8 actions, no `gh issue edit`, no comments posted, no file edits — including via Bash (it lacks Edit/Write but still has Bash, so state this explicitly). - Return the complete step-7 verdict verbatim as its final message, plus one line stating which baseline (branch/commit) claims were traced against. The subagent's final message comes back as the tool result; it is not shown to the user. If the call returns null or errors (user skip, terminal API failure), retry once; if it fails again, report the failure to the user instead of validating yourself. When the result arrives: - Run `git status --porcelain` and diff against the pre-dispatch snapshot to confirm the subagent made no file changes. If it did, tell the user and ask whether to revert before continuing. - Save the verdict verbatim to a scratchpad file immediately, so it survives context summarization and later steps can quote it exactly. ### 3. Spot-check the verdict Before presenting it, spot-check the verdict's load-bearing findings against the code: the `file:line` citations for any ❌/⚠️ claims resolve to real code saying what the verdict says, and the verdict doesn't contradict repo conventions (CLAUDE.md). Evidence outranks verdicts — a subagent citation that contradicts its own mark means the mark is wrong. Fix small inaccuracies yourself and note them (update the scratchpad copy); if the verdict is structurally wrong (e.g. traced a stale baseline, missed the central claim), do NOT silently re-dispatch — tell the user what's off and let them decide whether to re-run with Fable 5 or proceed. ### 4. Relay the verdict to the user Present the vetted verdict in the validate-issue step-7 format, noting it was produced by Fable 5 and which baseline it traced. Nothing is posted to GitHub at this stage — validation alone never writes to the issue. ### 5. Follow-on actions (main agent) Handle the user's reply per the validate-issue procedure — these are main-agent actions, never re-delegated: - **"update issue"** → apply the suggested title/body edits per validate-issue step 8, including its claim-verification gate and final consistency pass. Footer: since the findings came from the Fable 5 subagent, use `Validated with LLM: Fable 5 | high | Harness: Claude Code | fable-validate` (stack under any existing footer lines per step 8; a repo CLAUDE.md footer format overrides). - **"work on issue"** → hand off to the `work-on-issue` skill per validate-issue step 7.5, surfacing any step-6.5 scope disposition first. - **"split issue" / "decompose"** → file the proposed parts per validate-issue step 6.5, each fully specified. ## Notes - The validation subagent runs on Fable 5 regardless of the main agent's model — `model: fable` on the Agent call forces it. - **If the `fable` model is unavailable in this harness** (the Agent call errors on the model id), fall back to the most capable model available and proceed — the isolation pattern (read-only subagent validates, main agent acts) is what matters. Name the model that actually ran in the footer and report, never "Fable 5". - One subagent, one verdict: don't fan out or re-run for a second opinion unless the user asks. - If the user's reference turns out not to be fetchable (wrong number, no auth), the subagent will report that per the procedure — relay it; never validate against a paraphrase. ## Source & license This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code. - **Author:** [richkuo](https://github.com/richkuo) - **Source:** [richkuo/rk-skills](https://github.com/richkuo/rk-skills) - **License:** MIT Install and usage instructions live in the source repository linked above. ## Pricing - **Free** — Free ## Security capabilities Automated source analysis of v0.1.0 — what this tool can access: - **Network access:** no - **Filesystem access:** no - **Shell / process execution:** no - **Environment & secrets:** no - **Dynamic code execution:** no *"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.* ## Versions - **0.1.0** — security scan: passed — Imported from the upstream source. ## Links - Listing page: https://agentstack.voostack.com/l/skill-richkuo-rk-skills-fable-validate - Seller: https://agentstack.voostack.com/s/richkuo - Browse the marketplace: https://agentstack.voostack.com/browse --- Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.