Persistent Build Cache Issue: Vercel Incorrectly Detects Package Manager Change from yarn to pnpm

[Paul-Sizon]

Summary

I have fully migrated our Next.js project from Yarn to pnpm. However, every new deployment on Vercel fails to use the build cache, stating: Skipping build cache since Package Manager changed from "pnpm" to "yarn". This happens despite ensuring pnpm is configured everywhere and attempting multiple cache-clearing strategies, leading to significantly slower build times.

Project Configuration

• Framework: Next.js
• Repository: GitHub
• Previous Package Manager: Yarn
• Current Package Manager: pnpm
• Lock File: pnpm-lock.yaml (present in repo root)
• Yarn Lock File: Removed completely

Vercel Settings Attempted

• ✅ Set Install Command to: pnpm install
• ✅ Set Build Command: pnpm build
• ✅ Cleared build cache multiple times via dashboard
• ✅ Used "Skip Build Cache" option during deployment
• ✅ Verified no yarn.lock files remain in repository

Additional Steps Tried

• Added temporary environment variables for cache busting
• Manually cleared Vercel build cache from dashboard
• Confirmed pnpm-lock.yaml is committed and up to date
• Verified Vercel correctly detects and uses pnpm (as shown in logs)
• Made dummy commits to force fresh deployments

Expected Behavior

Build cache should be preserved between deployments using the same package manager (pnpm).

Actual Behavior

Every deployment shows "Skipping build cache since Package Manager changed from 'pnpm' to 'yarn'" despite pnpm being used consistently, resulting in full rebuilds and longer deployment times.

Impact

Significantly slower build times due to cache invalidation on every deployment.

Additional information

Build logs:

Running build in Washington, D.C., USA (East) – iad1
Build machine configuration: 4 cores, 8 GB
Cloning github.com/[my_project]
Cloning completed: 3.335s
Skipping build cache since Package Manager changed from "pnpm" to "yarn"
Running "vercel build"
Vercel CLI 42.2.0
Detected pnpm-lock.yaml 9 which may be generated by pnpm@9.x or pnpm@10.x
Using pnpm@9.x based on project creation date
To use pnpm@10.x, manually opt in using corepack (https://vercel.com/docs/deployments/configure-a-build#corepack)
Running "install" command: pnpm install...
Lockfile is up to date, resolution step is skipped
Progress: resolved 1, reused 0, downloaded 0, added 0
Packages: +1697
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Progress: resolved 1697, reused 0, downloaded 68, added 59
Progress: resolved 1697, reused 0, downloaded 148, added 131
....

Example

No response

[Paul-Sizon]

my bad, I had yarn in package that was outside of next package, after removing it, the error went away