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name: system-context-extractor description: Extracts architectural, business, and operational context from existing systems. Use to build mental models of unfamiliar codebases. triggers: [onboarding, migration-preparation, audit-start] outputs: [system-context-map, dependency-graph]

System Context Extractor

Purpose

Builds a comprehensive understanding of a system's structure and environment. This skill separates "the signal from the noise" in a legacy codebase, allowing for safer modifications.

When to use this skill

• When first encountering a legacy or inherited codebase
• Before starting a multi-module migration
• When auditing a system for security or performance

Extraction Steps

1. Identify System Boundaries: Where does the system interact with the outside world? (APIs, DBs, 3rd party services).
2. Separate Concerns: Identify which folders/files handle Business Logic vs. Infrastructure (Logging, ORM) vs. Tooling (CI/CD).
3. Identify Critical Components: Which modules, if broken, would cause a total system failure?
4. Record Unknowns: Explicitly list files or patterns that are not yet understood.

Decision Tree

Copyflowchart TD
    A[Start Context Scan] --> B{Documented?}
    B -->|Yes| C[Verify Docs vs Code]
    B -->|No| D[Analyze Project Structure]
    D --> E{Entry Points Found?}
    E -->|No| F[Scan for Routes/Controllers]
    E -->|Yes| G[Map Component Dependencies]
    F --> G
    G --> H[Create System Map]

Review Checklist

1. Hierarchy: Is the relationship between parent and child components clear?
2. Ownership: Is it clear which service "owns" which data?
3. Communication: Are the protocols (REST, gRPC, Pub/Sub) documented?
4. Tech Stack: Are all languages, frameworks, and versions identified?

How to provide feedback

• Be specific: "The context map misses the background worker that processes the 'order-queue'."
• Explain why: "Without identifying this worker, we might break asynchronous order processing during migration."
• Suggest alternatives: "Recommend scanning for BullMQ or RabbitMQ listener signatures."

Do not propose improvements. Observation only.