Scopes a provider so that all lookups are prefixed with the given path segments.

When to use

Use to namespace config under a prefix like "app" or "database", or reuse the same provider shape for multiple sub-configs.

Details

Accepts a single string or a full Path array. For providers composed with orElse, the prefix is applied to each operand. Supports both data-last and data-first calling conventions.

Gotchas

Ordering matters when composing with mapInput or constantCase. Later provider transformations run after earlier ones: a later nested becomes the outer prefix, and a later mapInput sees the whole path produced by previous transformations.

Example (Nesting under a prefix)

import { ConfigProvider } from "effect"

const provider = ConfigProvider.fromEnv({
  env: { APP_HOST: "localhost", APP_PORT: "3000" }
})

// Lookups for ["HOST"] now resolve to ["APP", "HOST"]
const scoped = ConfigProvider.nested(provider, "APP")