Legacy Codebase AI Migration Planner
PROAnalyze legacy codebases and create step-by-step migration plans to modern frameworks with risk assessment, dependency mapping, and testing strategies.
Example Usage
Create a migration plan for our legacy application:
Current state:
- Frontend: jQuery 3.x with Handlebars templates, 180 files
- Backend: Express.js 4.x with Sequelize ORM, 95 route handlers
- Database: MySQL 5.7 with 45 tables
- Tests: Mocha/Chai, ~40% coverage
- CI/CD: Jenkins pipelines
- Team: 6 developers (2 senior, 3 mid, 1 junior)
- Pain points: Slow page loads, difficult to hire, no TypeScript, no component reuse
Target state:
- Frontend: Next.js 15 with React Server Components
- Backend: Keep Express but add TypeScript, upgrade to Express 5
- Database: Migrate to PostgreSQL 16, add Prisma ORM
- Tests: Vitest + Playwright, target 80% coverage
- CI/CD: GitHub Actions
Constraints:
- Cannot have more than 2 days of downtime
- Must maintain backward compatibility during migration
- Budget: 6 months with current team
- Some features are business-critical and cannot break
Generate: Full migration plan with phases, risk assessment, timeline, team training needs, and rollback strategies.
Skill Prompt
This skill works best when copied from findskill.ai — it includes variables and formatting that may not transfer correctly elsewhere.
How to Use This Skill
1
Copy the skill using the button above
2
Paste into your AI assistant (Claude, ChatGPT, etc.)
3
Fill in your inputs below (optional) and copy to include with your prompt
4
Send and start chatting with your AI
Suggested Customization
| Description | Default | Your Value |
|---|---|---|
| Current framework/language to migrate from; auto-detects from package files, configs, and code patterns | auto-detect | |
| Target framework to migrate to; suggests modern equivalents if not specified | modern equivalent | |
| Migration approach: big-bang (all at once), incremental (feature by feature), strangler-fig (wrap and replace), or parallel-run | incremental | |
| Risk tolerance level: conservative (extensive testing, slow rollout), moderate (balanced), aggressive (fast migration, acceptable risk) | moderate |
- Copy the skill above and paste it into Claude Code or your preferred AI assistant
- Describe your legacy system: frameworks, file counts, dependencies, team size, and pain points
- Specify your target stack and any constraints (budget, timeline, downtime tolerance)
- Review the generated migration plan and adjust phases, timelines, or strategies
- Execute phase by phase, using the exit criteria to gate progression
What You’ll Get
- Complete codebase analysis with technical debt scoring
- Migration strategy recommendation (strangler fig, incremental, big bang, or parallel run)
- Risk assessment matrix with probability, impact, and mitigation strategies
- Phased migration plan with clear milestones and exit criteria per phase
- Team skill gap analysis with training recommendations
- Timeline estimates with optimistic, realistic, and pessimistic projections
- Data migration plan with validation checkpoints
- Rollback procedures for every migration phase
- Common migration patterns for your specific tech stack transition
Tips for Best Results
- Share your package.json, requirements.txt, or equivalent dependency files for accurate analysis
- Provide current test coverage numbers so the skill can recommend pre-migration testing targets
- Be honest about team experience with the target framework for realistic timeline estimates
- Identify your business-critical features upfront so they get special migration attention
- Run this skill at the start of your planning phase, not after migration has begun
Research Sources
This skill was built using research from these authoritative sources:
- PlayCode: Best AI Coding Assistants for Legacy Code Comparison of AI tools for understanding and migrating legacy codebases, including automated refactoring capabilities
- Martin Fowler: Strangler Fig Application Pattern Foundational pattern for incremental migration by gradually replacing legacy components with new implementations
- Augment Code: AI-Powered Legacy Code Understanding How AI agents analyze and understand large legacy codebases for migration planning and technical debt assessment
- ThoughtWorks Technology Radar: Migration Techniques Industry-standard assessment of migration techniques, patterns, and tools including incremental adoption strategies
- Shakudo: AI Coding Tools for Enterprise Migration Enterprise-focused analysis of AI-assisted migration tooling with case studies on large-scale codebase modernization
- AWS Prescriptive Guidance: Migration Strategies The 7 R's migration framework (Rehost, Replatform, Repurchase, Refactor, Retire, Retain, Relocate) with decision criteria