before-after

Capture and compare system states before and after implementation.

53|1|Updated Dec 18, 2025
One-click install
npx skills add https://github.com/cosmix/loom --skill before-after
Or copy as Structured Prompt for Agent
Please help me install this Agent Skill.
Skill: before-after
Source: https://github.com/cosmix/loom/tree/main/skills/before-after
Command: npx skills add https://github.com/cosmix/loom --skill before-after

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

This Skill helps you definitively prove that your code changes have the intended effect by capturing system state before and after implementation, preventing regressions and ensuring new features work as expected.

Core Features & Use Cases

  • Delta-Proof Verification: Establishes that a stage actually changed system behavior, not just that the final state is valid.
  • New Feature Validation: Proves a feature didn't exist before and now works correctly.
  • Bug Fix Confirmation: Demonstrates that a bug existed and is now resolved.
  • Behavior Change Tracking: Verifies that old behavior is replaced by new behavior.
  • Use Case: When adding a new API endpoint, use this skill to prove it returned a 404 error before your stage and now returns valid data after.

Quick Start

Use the before-after skill to verify that the new loom check command now works after implementation.

Frequently Asked Questions about before-after

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

FAQPage Schema
How do I prove my code changes actually altered system behavior?

To prove code changes altered system behavior, capture the system state before and after implementation to establish delta-proof verification. This framework compares states to ensure a stage demonstrably changed behavior, rather than just validating the final state.

How do I verify a bug fix and confirm the bug existed before my changes?

To verify a bug fix, capture the system state before implementation to demonstrate the bug existed, then compare it against the post-implementation state to confirm the issue is resolved. This delta-proof approach tracks the behavior change from broken to fixed.

What is the best way to validate that a new feature didn't exist before?

The best way to validate a new feature is to capture and compare system states before and after implementation. This proves the feature was absent initially and functions correctly now, using shell commands, code integration points, or file existence checks for verification.

Can I verify new API endpoints by checking system state before and after implementation?

Yes, you can verify new API endpoints by capturing the system state before and after implementation. For example, establish delta-proof verification by proving the endpoint returned a 404 error before your stage and now returns valid data after implementation.

What methods can I use to capture and compare system states for feature validation?

For feature validation, you can capture and compare system states using shell commands, code integration points, and file existence checks. These methods establish delta-proof verification by tracking behavioral changes across implementation stages.

Why should I use delta-proof verification instead of just testing the final code state?

You should use delta-proof verification because it establishes that a stage actually changed system behavior, not just that the final state is valid. This prevents regressions and ensures new features work as expected by capturing the before and after states.