understand-codelisted

# Understand Code **Mode:** READ-ONLY throughout. No edits during this skill. ## Step 1: Scope Discovery Use Glob and Grep to locate relevant files: ``` Glob: src/**/*<keyword>* Grep: "<keyword>" in src/ ``` Collect: - Entry point (controller, command, route handler, event listener) - Domain / business logic files - Adapter files (repository, HTTP client, external service) - Test files (unit + integration) ## Step 2: Code Tracing Read files in dependency order: 1. Entry point — what triggers this code path? 2. Application layer — what orchestration happens? 3. Domain — what business rules apply? 4. Adapters — how does the system persist or call out? Limit: Read at most 8 files. If scope is larger, narrow the argument. ## Step 3: Contract Mapping For each function in the call chain, note: - Pre-conditions (what must be true before the call) - Post-conditions (what is guaranteed after) - Error paths (what can go wrong) ## Step 4: Summary Report ```markdown ## Code Understanding: <argument> **Entry Point:** <file:line — method/endpoint/event> **Call Chain:** <Layer1> → <Layer2> → <Layer3> **Key Data Flow:** 1. <input> received at <layer> 2. <transformation or validation> 3. <persistence/response> **Domain Rules:** - <rule 1> **Test Coverage:** - Unit: <files or "none found"> - Integration: <files or "none found"> **Gaps / Risks (observe only — do not fix here):** - <gap 1> **Next Step:** - <if debugging>: hypothesis to test first - <if modi