Skill Refactorer for Claude Fable 5 / 5.1
Skills and prompts written for earlier Claude models often encode capability compensation: step-by-step hand-holding, exhaustive enumeration of edge cases, and rigid micro-workflows that existed because older models needed them. Fable 5 and 5.1 follow instructions strictly enough that this old scaffolding becomes a straitjacket — the model obeys the obsolete recipe instead of using its own (now better) judgment. The result is output that is worse than no skill at all. Fable 5 prompts generally carry over to 5.1 unchanged, but 5.1 narrates less and formats less by default, so lines written to suppress either now cut into what the reader needs.
Your job: separate what the instruction protects from how it micromanages, keep the former, delete the latter.
Workflow
- Inventory. List every imperative instruction in the target skill/prompt as a separate line item.
- Classify each item into exactly one bucket:
- Guardrail — protects against a real, current risk (data loss, secrets, destructive commands, compliance). KEEP.
- Preference — a genuine style/format choice the owner still wants (tone, language, naming conventions). KEEP, but compress to one sentence if it sprawls.
- Compensation — exists only because an older model would otherwise fail (forced step sequences, "always re-read the file before editing", verbose output templates, repeated "do not forget" reminders, enumerations of failure modes the model no longer exhibits). DELETE or replace with a single statement of intent.
- Rewrite. For every deleted compensation, ask: "what outcome was this trying to guarantee?" If the outcome still matters, state the outcome once, not the procedure. Example:
- Before: "Step 1: open the file. Step 2: locate the function. Step 3: copy it to a scratch buffer. Step 4: edit the copy. Step 5: diff against the original. Step 6: ..."
- After: "Edits must be verifiable: keep a way to diff your change against the original before finalizing."
- Tighten the description field. Triggering logic stays in frontmatter
description; the body should assume the skill already fired.
- Length check. A refactored skill is typically 30–60% shorter. If it isn't, re-run step 2 — you kept compensations.
- A/B test. Run one representative task with the old skill and one with the refactored skill. Compare outputs with the user before declaring victory. Afterward the model can keep the skill current from what it learns in-task, under these same rules: propose the edit, never drop a guardrail silently.
Red flags that mark a line as compensation
- Numbered procedures where the order doesn't actually matter
- The same warning repeated in different words
- Output templates that fix structure the user never asked for
- "Think step by step", "be careful", "double-check" without a concrete check
- Instructions to narrate or explain internal reasoning in the response (on Fable 5 and 5.1 this can trigger refusals — remove these entirely)
- Anti-formatting rules aimed at older, bullet-happy models ("no lists", "never bold"). 5.1 already formats sparingly, so these suppress structure the content needs — delete, or replace with a rule saying when a list or heading is appropriate
- "Hold all findings for the final response" and similar narration suppressors. 5.1 already writes fewer updates between tool calls; remove these before adding anything about progress reporting
What NOT to touch
- Domain facts, file paths, API contracts, schemas — these are knowledge, not scaffolding.
- Safety and permission boundaries. When in doubt whether something is a guardrail or a compensation, ask the user; never silently drop a guardrail.
1---2name: skill-refactorer3description: Audit and rewrite existing agent skills, system prompts, and CLAUDE.md files for Claude Fable 5 / 5.1. Use whenever the user mentions migrating, upgrading, porting, or "fixing" a skill or prompt for Fable 5 or 5.1, complains that a previously good skill now produces worse output, or asks why the model ignores or over-follows old instructions. Also trigger when reviewing any skill written before June 2026, or any skill written for Fable 5 that now runs on Fable 5.1.4---56# Skill Refactorer for Claude Fable 5 / 5.178Skills and prompts written for earlier Claude models often encode *capability compensation*: step-by-step hand-holding, exhaustive enumeration of edge cases, and rigid micro-workflows that existed because older models needed them. Fable 5 and 5.1 follow instructions strictly enough that this old scaffolding becomes a straitjacket — the model obeys the obsolete recipe instead of using its own (now better) judgment. The result is output that is *worse* than no skill at all. Fable 5 prompts generally carry over to 5.1 unchanged, but 5.1 narrates less and formats less by default, so lines written to suppress either now cut into what the reader needs.910Your job: separate what the instruction *protects* from how it *micromanages*, keep the former, delete the latter.1112## Workflow13141. **Inventory.** List every imperative instruction in the target skill/prompt as a separate line item.152. **Classify each item** into exactly one bucket:16 - **Guardrail** — protects against a real, current risk (data loss, secrets, destructive commands, compliance). KEEP.17 - **Preference** — a genuine style/format choice the owner still wants (tone, language, naming conventions). KEEP, but compress to one sentence if it sprawls.18 - **Compensation** — exists only because an older model would otherwise fail (forced step sequences, "always re-read the file before editing", verbose output templates, repeated "do not forget" reminders, enumerations of failure modes the model no longer exhibits). DELETE or replace with a single statement of intent.193. **Rewrite.** For every deleted compensation, ask: "what outcome was this trying to guarantee?" If the outcome still matters, state the outcome once, not the procedure. Example:20 - Before: "Step 1: open the file. Step 2: locate the function. Step 3: copy it to a scratch buffer. Step 4: edit the copy. Step 5: diff against the original. Step 6: ..."21 - After: "Edits must be verifiable: keep a way to diff your change against the original before finalizing."224. **Tighten the description field.** Triggering logic stays in frontmatter `description`; the body should assume the skill already fired.235. **Length check.** A refactored skill is typically 30–60% shorter. If it isn't, re-run step 2 — you kept compensations.246. **A/B test.** Run one representative task with the old skill and one with the refactored skill. Compare outputs with the user before declaring victory. Afterward the model can keep the skill current from what it learns in-task, under these same rules: propose the edit, never drop a guardrail silently.2526## Red flags that mark a line as compensation2728- Numbered procedures where the order doesn't actually matter29- The same warning repeated in different words30- Output templates that fix structure the user never asked for31- "Think step by step", "be careful", "double-check" without a concrete check32- Instructions to narrate or explain internal reasoning in the response (on Fable 5 and 5.1 this can trigger refusals — remove these entirely)33- Anti-formatting rules aimed at older, bullet-happy models ("no lists", "never bold"). 5.1 already formats sparingly, so these suppress structure the content needs — delete, or replace with a rule saying when a list or heading is appropriate34- "Hold all findings for the final response" and similar narration suppressors. 5.1 already writes fewer updates between tool calls; remove these before adding anything about progress reporting3536## What NOT to touch3738- Domain facts, file paths, API contracts, schemas — these are knowledge, not scaffolding.39- Safety and permission boundaries. When in doubt whether something is a guardrail or a compensation, ask the user; never silently drop a guardrail.
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