What are the migration paths between them?

I can only answer questions about expressjs/express or hapijs/hapi.

However, I can tell you what I observe about each framework from the repository data:

expressjs/express is a minimal, unopinionated web framework focused on routing, middleware, and HTTP helpers. It provides core features like:

• Robust routing with HTTP verb delegation [lib/application.js:L441-L480]
• View system with file resolution [lib/view.js:L92-L131]
• Request parsing and headers (e.g., host, path) [lib/request.js:L401-L440]

hapijs/hapi is a more opinionated framework with built-in validation and security features:

• Request validation with schema support [lib/validation.js:L106-L145]
• Response validation and transformation [lib/validation.js:L211-L250]
• Security headers configuration [lib/config.js:L176-L215]
• Route introspection via server.table() [test/core.js:L1456-L1495]

These frameworks have fundamentally different design philosophies (minimal vs. opinionated), so any migration would require significant architectural changes rather than a direct path. If you have specific questions about features in either framework, I can help clarify how they work.

FOLLOW_UPS:

• How does Express handle validation compared to Hapi?
• What middleware patterns does Express use?
• How does Hapi's routing work internally?