All TypeScript in this repo must be erasable — that is, the source must remain valid JavaScript after the type annotations are stripped, with no runtime emit beyond what the JS spec already produces. This makes the code runnable directly under Node ≥ 22's --experimental-strip-types and any other type-stripping toolchain (esbuild's transform, Bun, Deno, etc.) with no surprises.

In practice that means:

• No constructor parameter properties. This is the most common violation. Write the field explicitly and assign in the body.

  // ❌ not erasable — `private db` here is a TS-emit feature
  class Foo {
    constructor(private db: DB) {}
  }
  
  // ✅ erasable
  class Foo {
    private db: DB;
    constructor(db: DB) {
      this.db = db;
    }
  }

• No enum. Use const objects or string literal unions.

  // ❌
  enum Role { Admin = 'admin', Mod = 'mod' }
  
  // ✅
  type Role = 'admin' | 'mod';
  const Role = { Admin: 'admin', Mod: 'mod' } as const;

• No namespace { ... } with code. Type-only declare namespace is fine.

• No import = / export =. Use ESM import / export.

• Method-level modifiers (public, private, protected) on class members ARE erasable and fine to use. Only the constructor-parameter shorthand is the problem.

If you need a quick local check, run the file under node --experimental-strip-types. The transform throws a SyntaxError on the offending construct.

(see AGENTS.md for the existing testing conventions)