GuideIntermediate
Refactoring & Legacy Code with Claude Code
Master working with existing codebases using Claude Code. Learn to onboard 5-10x faster, explore codebases with the Explore subagent, coordinate multi-file refactoring, migrate frameworks, and manage context for large projects. The skills that cover 80% of a professional developer's real work.
- 43
- lessons
- 8
- modules
- English · Spanish
- available in
- Free
- access
Outcomes
What you'll be able to do
- Onboard to unknown codebases 5-10x faster using systematic Claude Code exploration
- Use the Explore subagent for read-only codebase investigation and semantic search
- Generate architecture diagrams, dependency maps, and flow analysis with Claude Code
- Execute coordinated multi-file refactoring with automated cross-file reference updates
- Plan and execute framework migrations (Flask→FastAPI) using strangler fig pattern
- Manage context for large projects: chunking strategies, CLAUDE.md, 1M token optimization
- Identify and eliminate tech debt with incremental refactoring assisted by AI
- Migrate a real legacy project end-to-end with documentation and regression tests
Before you start
What you need to bring
It's for you if...
- Developers joining existing teams who need to understand large codebases quickly
- Teams with accumulated tech debt looking for efficient modernization strategies
- Professionals working with large projects (50K-500K+ lines) who need context management skills
- Developers migrating frameworks or languages who want AI-assisted step-by-step execution
- Anyone who spends most of their time maintaining, understanding, or improving existing code
Requirements and materials
- Completed guides #1-6 of the Claude Code Agentic Development Path (or equivalent Claude Code experience)
- Completed guide #7 Testing with Claude Code (tests as safety net for refactoring)
- Intermediate Python (functions, classes, modules, imports, error handling)
- Git proficiency (branches, merging, pull requests, conflict resolution)
- No prior refactoring methodology experience required (taught from scratch)
Content
The syllabus, module by module
Open any of them to see its lessons.
- Module 1: Onboarding with AI — 5-10x Faster
- The Cost of Manual Onboarding and Why AI Transforms It
- Systematic Exploration — What to Ask and In What Order
- Building the Mental Model — Architecture, Layers, Entry Points
- Documenting Findings with Claude Code
- Module Project: Onboarding to an Open-Source Codebase
Common questions
What people usually ask
No limit. It's a free guide: come in whenever you like, as often as you like.
No. Modules run from easier to harder, but you can jump to the one you need. Progress is saved per lesson.
Whatever is needed is listed under “What you need to bring”, above. If nothing is listed there, you can start from zero.
In the WhatsApp group, and every two weeks there's a live with an instructor where questions get worked through.
Start whenever you like
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