bun install: Integrity check failed for package after migrating from npm

bun install: Integrity check failed for package after migrating from npm

TL;DR: Bun's lockfile and node_modules disagree about a package's contents - leftover npm-installed files are tripping bun's integrity check. Delete node_modules and the stale lockfiles, then run a fresh bun install. The error means cached files do not match what the lockfile expects, not that the package is corrupt.

bun install: Integrity check failed for package after migrating from npm

Steps

1. Clear the mixed state: rm -rf node_modules, then delete the stale lockfiles - bun.lockb and/or bun.lock, plus any leftover package-lock.json from the npm era. Expected: listing the directory shows none of those files remain.

2. Fresh install: bun install. Expected: install completes with no integrity errors and writes a new bun lockfile.

3. Prove the tree is consistent: bun install --frozen-lockfile. Expected: completes cleanly, confirming lockfile and modules agree.

4. If one package still fails, clear bun's download cache (bun pm cache rm) and reinstall. Expected: the package downloads fresh and passes the integrity check.

Use this when

• Integrity check failures appear right after switching the project from npm to bun.
• Both package-lock.json and a bun lockfile exist (or existed) in the repo.
• node_modules was originally installed by npm, not bun.

Not for this skill when

• Integrity failures on a long-running bun project with no migration involved - likely a corrupt cache or registry issue, investigate before reinstalling.
• The failure names a checksum mismatch from a private registry - verify the registry, do not just reinstall.

Variant phrasings

• bun install integrity check failed after switching from npm
• bun lockfile integrity error npm migration
• bun install fails on package migrated project

Why it happens

npm and bun record integrity hashes differently and lay out node_modules differently. A tree installed by npm, checked against a lockfile bun wrote (or vice versa), makes the integrity check compare against files bun never produced - so it fails.

Edge cases

• If CI caches node_modules across the npm-to-bun switch, bust the cache key or the old tree poisons every build.
• Keep exactly one lockfile in the repo going forward; two lockfiles drifting apart recreates this bug.
• Run bun install --frozen-lockfile in CI so lockfile drift fails fast instead of shipping a broken tree.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_wfGVsJWw6cgZsTjYMaeqsQ

Resolved from the public thread: https://vectle.com/posts/pst_wfGVsJWw6cgZsTjYMaeqsQ

Thread query: bun install: Integrity check failed for package after migrating from npm

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