---
title: Bun Runtime Migration
category: product
entity_type: skill
price: $15
canonical: https://forgehouse.ai/skills/bun-runtime-migration/
lang: en
hreflang_alt: https://forgehouse.ai/tr/skiller/bun-runtime-migration/
last_updated: 2026-06-20
---

# Bun Runtime Migration

> Migrate a Node.js project to Bun

Move backend scripts, CI test runners and dev tooling from Node.js to the Bun runtime, without breaking production. The skill brings a disciplined, incremental migration: a compatibility matrix triage, native-addon audit, lockfile migration strategy and a CI/CD switch, so you capture Bun's faster installs, ~10x faster test runs and lower startup latency only where it's safe, with a rollback plan at every step.

## Use cases
- Lowering cron-job startup latency on backend servers
- Cutting CI minutes by moving from jest to bun test
- Speeding up dependency installs (from ~90s toward ~25s)
- Auditing native addons (sharp, bcrypt, sqlite3) for Bun compatibility
- Planning a package-lock.json to bun.lockb lockfile migration
- Benchmarking npm vs bun install/test/build with hyperfine

## Benefits
- Capture faster installs, tests and startup only where it's proven safe
- Avoid production breakage with a 4-stage incremental migration path
- Keep a rollback ready at every stage (parallel lockfile and node_modules)
- Make a measured KABUL/ERTELE/RED decision instead of chasing a trend

## What’s included
- bunfig.toml, package.json scripts and lockfile comparison reference
- GitHub Actions workflow with setup-bun, cache and Node fallback job
- Pre-flight migration script (native addon detect + dry-run gate)
- hyperfine benchmark script for install/test/build/startup comparison
- Compatibility matrix triage: blocker / workaround / wontfix categories
- Migration decision brief template with risk and rollback sections

## Who it’s for
Backend and platform engineers evaluating Bun for cron jobs, CI test runners and internal tooling who need the speed gains without risking production stability.

## How it runs
Moving to Bun is a gated engineering decision with rollback at every stage, never a trend jump. The sequence runs from scope checks and dependency triage to two weeks of parallel lockfiles before CI flips.
1. Scope gate first: only backend scripts, CI test runners and dev tooling qualify; Vercel Next.js production builds, n8n core and Expo metro bundling stay on Node and npm, no exceptions.
2. Runs the pre-flight script: Bun version check, module type, native addon scan (sharp, bcrypt, sqlite3, canvas with known verdicts per platform), lockfile backup, then bun install --dry-run; any incompatible package stops the migration cold.
3. Triages every dependency into blocker, workaround or wontfix: blockers get alternatives (bun:sqlite instead of sqlite3, bcryptjs instead of bcrypt) or the migration is deferred with the reason recorded.
4. Migrates in four incremental stages, each with rollback ready: bun install, then bun run dev, then bun test (resolving jest-to-bun mock API differences), and only after all three pass, the CI workflow switch.
5. Runs lockfiles in parallel for two weeks: package-lock.json and bun.lockb both committed, divergence checked with bun pm ls against npm ls, and the npm lockfile retires only at zero divergence.
6. Flips CI with oven-sh/setup-bun@v2: cache keyed on the bun.lockb hash, --frozen-lockfile mandatory to catch drift, bunx tsc --noEmit as a separate type-check step, and hyperfine benchmarks document the actual install, test and startup gains.

## FAQ
### Do my existing Node scripts run on Bun, or is this a rewrite?
For the scripts, CI runners, and dev tooling this targets, most run as-is since Bun aims for Node compatibility. The migration is about swapping the runtime and catching the edges, not rewriting your logic.

### Bun is fast, but is it safe to put in front of production?
That's why the scope here is deliberately cron jobs, CI test runners, and internal tooling, the low-blast-radius surfaces. It moves the fast wins first 'without breaking production,' rather than betting your live server on a runtime swap.

### Can I migrate my whole production app server to Bun with this?
No, and that's the honest limit. Bun isn't a full drop-in where you lean on native Node addons or less-common Node APIs, so this stays at the edges and leaves the production runtime decision out of scope.

## Price
$15, one-time, no subscription. VAT included.

Related guide: [AI code review and developer workflow](https://forgehouse.ai/guides/ai-code-review/)