♻️ Refactoring

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Optimize oversized CLAUDE.md files using progressive disclosure. Analyzes content tiers, detects encryption constraints, creates sub-documents, and rewrites the main file with a Sub-Documentation Table. Triggers: optimize CLAUDE.md, reduce CLAUDE.md size, CLAUDE.md too long, apply progressive disclosure to CLAUDE.md

Build and extend brownfield features in an existing codebase. Use when a request requires understanding module dependencies, researching the latest official docs for current tech stacks/APIs/external dependencies, and implementing tested changes in a mature project. For multi-module changes, produce a PRD and obtain explicit user approval before coding.

Analyze, plan, review, and optimize any codebase across 4 modes: Discovery (understand architecture and risks), Review (validate changes and detect breaking changes), Optimization (find bottlenecks and vulnerabilities), Implementation Planning (generate step-by-step guidance). Works with React, Django, Rails, Go, Rust, and 30+ frameworks. Use when analyzing codebase structure, assessing feature safety, finding security issues, planning implementations, or discovering performance problems.

Use when writing ANY implementation code, fixing bugs, or modifying existing code. Delegates research to a fast subagent that distills WebSearch results into compact RAG-efficient summaries. Main context never sees raw output.

Analyze Rails application upgrade path. Checks current version, finds latest release, fetches upgrade notes and diffs, then performs selective upgrade preserving local customizations.