Effect for TypeScript

Inspect the owning package and existing implementation first. Reuse established project types, helpers, errors, lifecycle behavior, and test utilities. The patterns below are options, not an implementation checklist. Introduce one only when the current task requires it.

Project-specific rules

• Create services and Layers only for real dependencies or resource lifetimes.
• Do not require a class, interface, service tag, and Layer for every capability.
• Reuse existing IDs, errors, validation, database services, and runtime.
• Keep Effect execution explicit at the application boundary.
• Use native resource finalizers; do not surround sufficient library cleanup with custom lifecycle machinery.

Effect v3 and v4 share the same programming model but differ in important API names and shapes. Resolve the project's version before writing or reviewing code.

Resolve the version first