# Migrating from Bun (/docs/guides/migrating-from-bun)



`lpm migrate` converts a Bun project to LPM in one command. It detects `bun.lock` or `bun.lockb`, parses the lockfile, writes `lpm.lock` plus `lpm.lockb` when the graph fits the binary format, optionally configures `.npmrc`, runs `lpm install`, and verifies `build` + `test` when those scripts exist.

This guide covers the Bun-specific parts. For the full flag reference, see [`lpm migrate`](/docs/packages/migrate).

## Prerequisites [#prerequisites]

* LPM installed - see [Installation](/docs/installation).
* A `package.json` plus `bun.lock` or `bun.lockb` in the project root.
* A clean or committed working tree.

`bun.lock` is the direct path. When `bun.lockb` is selected, LPM first looks for a sibling `bun.lock`; if it exists, LPM parses that text lockfile instead. If no sibling text lockfile exists, LPM runs `bun bun.lockb` and parses the emitted JSON. If the `bun` binary is unavailable, migration exits with a clear error.

## 1. Preview [#1-preview]

```bash
lpm migrate --dry-run
```

Dry-run detects Bun, parses the selected lockfile, converts the graph in memory, and writes nothing. It reports package counts, workspace counts, and any conversion problems before touching disk.

If the project contains multiple lockfiles, LPM chooses the most recently modified one. On timestamp ties, the priority order is `bun.lockb`, `bun.lock`, `pnpm-lock.yaml`, `yarn.lock`, then `package-lock.json`.

## 2. Run The Migration [#2-run-the-migration]

```bash
lpm migrate
```

What runs:

1. Confirm `package.json` exists and refuse to overwrite an existing `lpm.lock` unless `--force` is set.
2. Parse Bun package entries, exact versions, tarball URLs, integrity strings, dependency edges, and dev/optional metadata.
3. Write `lpm.lock` and, when supported, `lpm.lockb`.
4. Back up the Bun lockfile, `.npmrc` when touched, `.gitattributes`, and any pre-existing LPM lockfiles.
5. Add LPM registry routing to `.npmrc` unless `--no-npmrc` is set.
6. Run `lpm install` against the converted lockfile unless `--no-install` is set.
7. Run `build` + `test` scripts unless `--skip-verify` is set.

The flow is non-interactive. `-y` is accepted but reserved for a future interactive mode; it does not imply `--force`.

## 3. Verify [#3-verify]

```bash
lpm install --offline
lpm test
lpm lint
```

`lpm install --offline` confirms the new lockfile and the warmed store can replay without network access. If your Bun project used scripts that shell out through `bun`, keep Bun installed wherever those scripts run; migration changes the package manager, not your project scripts.

## 4. Commit [#4-commit]

```bash
git add lpm.lock .npmrc package.json
test ! -f lpm.lockb || git add lpm.lockb
git rm bun.lock bun.lockb bun.lock.backup bun.lockb.backup .npmrc.backup
git commit -m "Migrate to LPM"
```

Only remove files that exist in your repo. Do not commit `.backup` files unless you intentionally keep migration rollback artifacts in the repository.

## Bun-Specific Notes [#bun-specific-notes]

* `bun.lock` JSON is parsed directly.
* `bun.lockb` needs either a sibling `bun.lock` or the `bun` binary available during migration.
* Bun lockfile metadata carries dev and optional package flags, so the converted lockfile preserves those package classifications.
* The install step rebuilds `node_modules`. Single-package projects default to LPM's hoisted v2 layout; workspaces and peer-conflict installs use isolated layout unless you override the linker.
* Dependency lifecycle scripts remain denied by default. After migration, run [`lpm rebuild`](/docs/packages/rebuild) and [`lpm approve-scripts`](/docs/packages/approve-scripts) for packages that need install-time builds.

## Rollback [#rollback]

```bash
lpm migrate --rollback
```

Restores backups from the previous migration run and removes LPM files created by that run. Safe to run repeatedly.

## See also [#see-also]

* [`lpm migrate`](/docs/packages/migrate) - full flag reference
* [Migrating from npm](/docs/guides/migrating-from-npm) - package-lock migration
* [Migrating from pnpm](/docs/guides/migrating-from-pnpm) - pnpm-specific translations
* [Migrating from Yarn](/docs/guides/migrating-from-yarn) - Yarn lockfile migration
* [Lockfile](/docs/packages/lockfile) - what gets committed and why