TypeScript "moduleResolution bundler" Errors - Fix Module Config in CI

By Kaveh Alemi·Latchkey

moduleResolution: "bundler" tells tsc to resolve modules the way a bundler does (honoring exports, no mandatory extensions). It must be paired with a compatible module setting; mismatches raise TS5095, and switching from Node resolution can surface subpath-import errors.

What this error means

tsc fails with TS5095: Option 'bundler' can only be used when 'module' is set to 'preserve' or to 'es2015' or later, or previously-resolving subpath imports now error after switching moduleResolution to bundler.

error TS5095: Option 'bundler' can only be used when 'module' is set to
'preserve' or to 'es2015' or later.
# or, after switching:
src/x.ts:2:23 - error TS2307: Cannot find module 'pkg/sub' or its
corresponding type declarations.

Common causes

module not compatible with bundler resolution

moduleResolution: "bundler" requires module to be esnext/preserve/es2015+. A module: "commonjs" (or node16) paired with it triggers TS5095.

Resolution semantics changed from Node

bundler resolves exports maps and omitted extensions differently than node/node16. A subpath that resolved under one can fail under the other if the package's exports does not declare it.

How to fix it

Pair bundler with a compatible module setting

Set module to esnext/preserve when using moduleResolution: "bundler".

// tsconfig.json
{
  "compilerOptions": {
    "module": "esnext",
    "moduleResolution": "bundler"
  }
}

Fix subpath imports the exports map allows

1. If a subpath import now fails, check the package's exports for that path.
2. Import a path the exports map actually exposes, or use the package's documented entry.
3. Keep tsc resolution aligned with how your bundler resolves at build time.

How to prevent it

• Match module to moduleResolution (bundler needs esnext/preserve).
• Use bundler resolution only when a bundler does the loading.
• Import only subpaths a package's exports map declares.

Frequently asked questions

Related guides

References

• Node.js documentation
• npm CLI documentation
• GitHub Actions documentation