Bun: 'error: Cannot find package "x" from "/path/file.ts"' or imports resolving differently when running a Node project with bun instead of node

Cause: Bun implements the Node.js module resolution algorithm: for a bare import it looks upward for a node_modules directory that contains the package and reads its package.json (exports first, then main/module). The error therefore usually means one of: dependencies were never installed with Bun or at all, the package is not listed in the project you are running from, the import is not allowed by the package's exports map, or Bun's auto-install (used only when no node_modules exists anywhere above the importing file) is off or cannot pick a version. Fix (best first): 1. Run bun install in the project root so node_modules exists, then retry. bun install reads package.json and writes the text lockfile bun.lock. If you have only package-lock.json, yarn.lock or pnpm-lock.yaml, bun install can migrate it (yarn and pnpm are documented; commit the new bun.lock). 2. Check the layout. Bun's default linker is hoisted for single-package projects and isolated (pnpm-like, packages under node_modules/.bun) for new workspaces. Code that imports a package that is not declared in its own package.json (phantom dependency) can fail with the isolated linker; declare the dependency, or use bun install --linker hoisted. 3. Respect package exports. Once a package defines exports, only the listed subpaths are importable; import the documented entry instead of a deep file path. Bun also honors the "bun" condition and can be given extra conditions with --conditions. 4. For aliases, define tsconfig/jsconfig "paths" or package.json "imports" (keys beginning with #); Bun reads both. NODE_PATH adds extra lookup directories. 5. If auto-install is expected but not happening, remember it only runs when no node_modules is found in the file's directory or any parent; a broken bunfig.toml or unreadable package.json disables it, and Bun then tells you to run bun install. Prefer an explicit install to relying on it. 6. Dependencies' postinstall scripts do not run under Bun unless the package is listed in trustedDependencies, which can leave native packages unbuilt; add only packages you trust. 7. Some Node built-ins are only partially implemented in Bun (for example parts of crypto, tls, module, worker_threads), so a missing function there is a compatibility gap, not a resolution failure. Verify: run bun install, then bun run <entry>; a clean run with no Cannot find package error. For CI, bun ci (a frozen install) confirms bun.lock matches package.json. Sources: https://bun.sh/docs/runtime/modules https://bun.sh/docs/runtime/auto-install https://bun.sh/docs/cli/install https://bun.sh/docs/runtime/nodejs-apis