# What changed in @nestjs/config

> 13 changes in @nestjs/config 12 from its official release notes, upgrade guides and advisories: 9 breaking, 2 new APIs and options. Each one cited. Sources checked 2026-10-19. HTML: https://unstale.sh/npm/@nestjs/config/

To see which of these apply to a repository, run `npx @unstale/cli init` in it.

## @nestjs/config 12

### Breaking changes

- The explicit type parameter is constrained to the value at the given path, so types inconsistent with the config shape fail to compile. (12.0.0) — [release notes](https://github.com/nestjs/config/releases/tag/12.0.0)
- The explicit type parameter is constrained to the value at the given path, so types inconsistent with the config shape fail to compile. (12.0.0) — [release notes](https://github.com/nestjs/config/releases/tag/12.0.0)
- The lodash runtime dependency is removed and replaced by es-toolkit; this matters if you relied on lodash being installed transitively. (12.0.0) — [release notes](https://github.com/nestjs/config/releases/tag/12.0.0)
- The peer dependency range is now ^11.0.0 || ^12.0.0; Nest 10 is no longer supported. (12.0.0) — [release notes](https://github.com/nestjs/config/releases/tag/12.0.0)
- The package is published as pure ESM with an exports map; CommonJS apps can continue using require on Node 20.19+ or 22.12+. (12.0.0) — [release notes](https://github.com/nestjs/config/releases/tag/12.0.0)
- Deep imports into build internals are no longer resolvable; import from the package root instead. (12.0.0) — [release notes](https://github.com/nestjs/config/releases/tag/12.0.0)
- Validation issues are formatted as path: message, with issues separated by newlines, rather than using the schema library's format. (12.0.0) — [release notes](https://github.com/nestjs/config/releases/tag/12.0.0)
- Library-specific validation settings now belong under libraryOptions in the Standard Schema Options object. (12.0.0) — [release notes](https://github.com/nestjs/config/releases/tag/12.0.0)
- Accepts schemas implementing Standard Schema, including Zod, Valibot, ArkType, and Joi 18+; schemas not implementing the spec are compile-time errors. (12.0.0) — [release notes](https://github.com/nestjs/config/releases/tag/12.0.0)

### New APIs and options

- When true, values from .env files take precedence over existing process.env variables; the default remains false. (12.0.0) — [release notes](https://github.com/nestjs/config/releases/tag/12.0.0)
- Accepts a function that parses a Buffer into an object, allowing .env files in formats such as YAML, TOML, or JSON; it is used at bootstrap and during variable re-interpolation. (12.0.0) — [release notes](https://github.com/nestjs/config/releases/tag/12.0.0)

### Fixes and other changes

- Prevents prefix corruption and escapes propertyPath during environment interpolation updates. (12.0.1) — [release notes](https://github.com/nestjs/config/releases/tag/12.0.1)
- Variables omitted by object schemas are merged back into the validated result, keeping unrelated variables reachable through process.env and ConfigService. (12.0.0) — [release notes](https://github.com/nestjs/config/releases/tag/12.0.0)