mathews-tom/skill-distiller

Skill Distiller

Transform skills authored for high-capability models (Opus) into deterministic workflows that execute reliably on lower-cost models (Sonnet, Haiku). The core insight from EvoSkills: skills encode reusable task structure, not model-specific artifacts. A skill evolved on Opus transfers with +35-45pp gains to other models — but only when the instructions are sufficiently deterministic that lower-capability models can follow them without improvising.

Reference Files

| File | Contents | Load When | | -------------------------------------- | -------------------------------------------------- | ------------------------------------ | | references/distillation-patterns.md | Pattern catalog for converting reasoning to rules | Always |

Prerequisites

• The source skill must exist and pass package-evaluator at >= 70%
• Access to both the source model (Opus) and target model (Haiku/Sonnet) for validation
• The surrogate-verifier skill for cross-model assertion checking

Workflow

Phase 1: Complexity Analysis

Score each section of the source SKILL.md for reasoning difficulty:

| Complexity Signal | Score | Distillation Action | | ------------------------------------- | ----- | -------------------------------------------- | | Decision tree with 3+ branches | HIGH | Convert to explicit if/then lookup table | | "Use judgment" or "consider context" | HIGH | Replace with concrete heuristic rules | | Multi-step inference chain | HIGH | Break into numbered atomic steps | | Reference to domain expertise | MED | Add explicit reference file with knowledge | | Clear enumerated steps | LOW | Keep as-is | | Concrete examples with expected output| LOW | Keep as-is |

Produce a complexity map: section name -> complexity score -> planned action.

Phase 2: Trace Collection

Execute the source skill with Opus on 5 representative tasks:

1. Select tasks from evals/cases.yaml (positive cases) or generate new ones
2. For each task, capture the full execution trace:
   • Tool calls made (which tools, in what order)
   • Intermediate reasoning visible in output
   • Final output structure and content
   • Time taken and token usage
3. Store traces as structured data for pattern extraction

Phase 3: Pattern Extraction

From the collected traces, extract deterministic patterns:

1. Decision paths — For each HIGH-complexity section, find the actual decisions Opus made across the 5 tasks. If Opus chose the same path in 4/5 cases, that path becomes the default rule
2. Lookup tables — Where Opus applied domain knowledge, build explicit lookup tables (e.g., "if input contains SQL, use these patterns; if input contains Python, use those")
3. Concrete examples — Extract representative input/output pairs from traces to serve as few-shot examples in the distilled skill
4. Tool sequences — Identify the common tool invocation pattern and make it explicit ("Step 1: Read the file. Step 2: Grep for pattern X. Step 3: Write output.")

Phase 4: Distilled Rewrite

Rewrite the SKILL.md applying all distillation actions from Phase 1:

| Source Pattern | Distilled Replacement | | -------------------------------------- | ------------------------------------------------------------ | | "Analyze the code and determine..." | "Check for these 5 specific patterns: [list]" | | "Use appropriate formatting" | "Output as a markdown table with columns: [A, B, C]" | | "Consider the context to decide..." | "If [condition A]: do X. If [condition B]: do Y. Default: Z" | | "Apply best practices for..." | Reference file with explicit best practices enumerated | | Multi-paragraph reasoning instruction | Numbered step list with single-sentence steps |

Rules for the rewrite:

• Every instruction must be actionable by a model with no domain expertise
• No step should require inference — each step's input and output must be explicit
• Replace all "consider", "analyze", "determine" verbs with "check", "count", "list", "output"
• Add concrete examples for any step that could be ambiguous
• Keep the SKILL.md under 500 lines (distillation should reduce, not expand)

Phase 5: Target Model Validation

Run the distilled skill on the target model (Haiku or Sonnet):

1. Execute the same 5 tasks from Phase 2 with the distilled skill loaded
2. Use the surrogate-verifier to generate assertions for each task output
3. Compare pass rates:

| Metric | Source (Opus + original) | Target (Haiku + distilled) | Delta | | ------------------------------- | ------------------------ | -------------------------- | ----- | | Assertions passed | N/M | N/M | ± | | Weighted score | X.XX | X.XX | ± | | Output completeness | % | % | ± | | Format compliance | % | % | ± |

4. If target model score < 80% of source model score, iterate:
   • Identify which assertions the target model fails
   • Add more explicit instructions for those specific failure points
   • Re-run validation (max 3 iterations)

Phase 6: Cross-Model Report

Produce the final comparison:

# Skill Distillation Report: <skill-name>

## Complexity Reduction
- Sections distilled: N/M (HIGH → LOW)
- Instruction word count: original X → distilled Y (Z% reduction)
- Decision points replaced with lookup tables: N

## Cross-Model Performance
| Model   | Assertions Passed | Weighted Score | Format Compliance |
|---------|-------------------|----------------|-------------------|
| Opus    | 7/7               | 1.00           | 100%              |
| Sonnet  | 6/7               | 0.92           | 100%              |
| Haiku   | 5/7               | 0.85           | 85%               |

## Changes Made
1. [Section] "Analyze complexity" → explicit 5-item checklist
2. [Section] "Apply formatting" → fixed markdown table template
...

## Recommendation
[SHIP | ITERATE | MANUAL_REVIEW_NEEDED]

Error Handling

| Error | Resolution | | ----------------------------------- | ------------------------------------------------------------- | | Source skill scores below 70% | Refuse distillation; recommend evolution via test-engineer | | No execution traces available | Generate synthetic tasks and collect traces before proceeding | | Target model fails all assertions | Skill may be too complex for target model; report with detail | | Distilled skill longer than source | Review distillation; patterns may need consolidation |

Limitations

• Cannot distill skills that rely on open-ended adaptive reasoning at many decision points or multi-turn reasoning
• Visual/interactive skills (HTML generation, browser automation) may not distill well
• Distillation optimizes for determinism, not creativity — skills requiring open-ended generation (writing, brainstorming) are poor candidates
• Trace collection requires actual model execution, incurring API costs