# Vercel Forcing pnpm Despite npm Configuration in Monorepo
## Current versus Expected behavior
**Current Behavior:**
- Vercel executes `pnpm install` during deployment
- Build logs show: `> Detected Turbo. Adjusting default settings…` followed by `Running “install” command: pnpm install`
- This causes `ERR_PNPM_META_FETCH_FAIL` and `ERR_INVALID_THIS` errors
- All deployments fail with: `Error: Command “pnpm install” exited with 1`
**Expected Behavior:**
- Vercel should execute `npm install --legacy-peer-deps` as specified in configuration
- Build should proceed without pnpm-related errors
## Code, configuration, and steps that reproduce this issue
### Repository Structure
```
monorepo/
├── vercel.json (root)
├── package.json (root - has workspaces)
├── apps/
│ └── web/
│ ├── vercel.json
│ ├── package.json
│ └── .npmrc
└── packages/
```
### Configuration Files
**Root `vercel.json`:**
```json
{
“version”: 2,
“installCommand”: “”,
“buildCommand”: “cd apps/web && npm install --legacy-peer-deps && npm run build”,
“framework”: “nextjs”,
“outputDirectory”: “apps/web/.next”
}
```
**`apps/web/vercel.json`:**
```json
{
“version”: 2,
“installCommand”: “”,
“buildCommand”: “npm install --legacy-peer-deps && npm run build”,
“framework”: “nextjs”
}
```
**Root `package.json` (relevant parts):**
```json
{
“packageManager”: “npm@10.9.2”,
“workspaces”: [
“apps/*”,
“packages/*”
]
}
```
**`apps/web/package.json` (relevant parts):**
```json
{
“packageManager”: “npm@10.9.2”
}
```
**`.npmrc` (root and apps/web):**
```
legacy-peer-deps=true
registry=https://registry.npmjs.org/
```
### Vercel Dashboard Settings
- **Root Directory:** `apps/web`
- **Install Command:** (empty - to use vercel.json)
- **Build Command:** (empty - to use vercel.json)
- **Framework Preset:** Next.js
### Steps to Reproduce
1. Deploy a monorepo with workspaces configuration
2. Set Root Directory to `apps/web` in Vercel Dashboard
3. Configure `installCommand: “”` in vercel.json
4. Configure `buildCommand` with `npm install --legacy-peer-deps`
5. Trigger deployment
6. Observe build logs showing `pnpm install` being executed instead
### Build Logs (Error)
```
Running “vercel build”
> Detected Turbo. Adjusting default settings…
Running “install” command: `pnpm install`…
ERR_PNPM_META_FETCH_FAIL GET https://registry.npmjs.org/@types%2Fnode: Value of “this” must be of type URLSearchParams
WARN GET https://registry.npmjs.org/… error (ERR_INVALID_THIS). Will retry in 10 seconds. 2 retries left.
Error: Command “pnpm install” exited with 1
```
## Project information
- **Framework:** Next.js 15.5.7
- **Node Version:** 20.x
- **Package Manager:** npm 10.9.2 (preferred)
- **Monorepo:** Yes (using npm workspaces)
- **Root Directory:** `apps/web`
- **Vercel Plan:** Hobby
### What We’ve Already Tried (All Failed)
1. 
Added explicit `installCommand: “npm install --legacy-peer-deps”` in both vercel.json files
2. Set `installCommand: “”` (empty string) to skip automatic install
3. Removed `installCommand` completely and embedded npm install in `buildCommand`
4. Added `ENABLE_EXPERIMENTAL_COREPACK=1` environment variable
5. Removed all pnpm lockfiles (`pnpm-lock.yaml`, `pnpm-workspace.yaml`)
6. Added `“packageManager”: “npm@10.9.2”` in both package.json files
7. Verified NO `builds` property exists in vercel.json
8. Created `.npmrc` with `legacy-peer-deps=true`
9. Temporarily removed Turbo (renamed `turbo.json` and removed `turbo` package from dependencies)
### Critical Finding
Even after removing Turbo completely (both `turbo.json` file and `turbo` package), build logs still show:
```
> Detected Turbo. Adjusting default settings…
```
This suggests Turbo/monorepo detection happens at a deeper level, possibly based on:
- Monorepo structure (workspaces in package.json)
- Vercel’s zero-configuration build process running before custom commands
### Questions
1. **How does Vercel detect Turbo/monorepo if neither turbo.json nor turbo package exists?**
- Is detection based on monorepo structure (workspaces) alone?
2. **Why does Turbo detection override `installCommand: “”`?**
- According to docs, empty string should skip automatic install
- But Vercel still executes `pnpm install`
3. **What is the exact priority order for package manager detection?**
- Turbo detection > installCommand > buildCommand?
- Dashboard settings > vercel.json?
4. **Is there a way to completely disable automatic package manager detection in monorepos?**
- We need to force npm regardless of any detection
5. **Is this a known issue with Vercel’s monorepo/Turbo integration?**
Any help or workarounds would be greatly appreciated! We’re completely blocked on deployments.