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hidden-contract-investigator

Extract implicit behavioral contracts from legacy code for reuse risk assessment.

5|4|Updated Nov 9, 2025
Search Tags:#legacy code#contract testing#exception handling#contract extraction#reuse risk#implicit behavior
One-click install
npx skills add https://github.com/takusaotome/claude-skills-library --skill hidden-contract-investigator
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: hidden-contract-investigator
Source: https://github.com/takusaotome/claude-skills-library/tree/main/skills/hidden-contract-investigator
Command: npx skills add https://github.com/takusaotome/claude-skills-library --skill hidden-contract-investigator

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) and assets (resource) components.

What problem does it solve?

This Skill prevents costly integration failures by uncovering the implicit behavioral contracts hidden in legacy code, so you can reuse existing functions or modules with clear, evidence-based guardrails.

Core Features & Use Cases

  • Name vs. behavior contract extraction: Identify what the code actually returns, mutates, throws, and assumes, rather than trusting identifiers, comments, or type annotations.
  • Mismatch classification for reuse risk: Systematically compare stated vs. observed contracts and categorize discrepancies (naming, types, state, environment dependency, hidden side effects).
  • Reuse decision support: Produce a reuse feasibility verdict (A–E) and generate wrapper/adapter recommendations plus prerequisites and safety constraints.
  • Verification planning with contract tests: Design minimal contract test ideas that lock down return/side-effect/exception/environment boundaries to stop contract drift.

Quick Start

Use the hidden-contract-investigator skill to analyze a specific legacy function or module for hidden return types, side effects, preconditions, exception behavior, and environment-sensitive differences before you reuse it in a new feature.

Frequently Asked Questions about hidden-contract-investigator

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I extract implicit behavior contracts from legacy code to evaluate reuse risks?▼

Extracting implicit behavior contracts from legacy code involves identifying observed return types, side effects, preconditions, and exception paths, then comparing them against stated contracts to generate a reuse risk register and feasibility verdict.

What is the best way to verify reuse feasibility for a legacy module before integration?▼

Verifying reuse feasibility for a legacy module requires classifying contract mismatches across naming, types, state, and environment dependencies, producing an A–E adoption recommendation with wrapper prerequisites and safety constraints.

Why do legacy functions break when reused in new features despite matching type annotations?▼

Legacy functions break on reuse because hidden side effects, environment-dependent behavior, and unhandled exception paths diverge from stated type annotations, requiring explicit contract extraction to reveal mismatches.

Can I generate contract test ideas to prevent contract drift in existing modules?▼

Yes, you can generate contract test ideas that lock down return, side-effect, exception, and environment boundaries, creating minimal verification tests to prevent contract drift when reusing existing modules.

Does contract testing work for service boundaries and persistence layers in legacy code?▼

Contract testing works for legacy code across function, module, service boundary, and persistence or serialization edges by extracting observed behavior to compare against stated contracts and identifying environment-sensitive differences.

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