Turborepo cache miss on consecutive builds when .next folder exists, even with identical hash

[PSriVignesH]

Summary

Hi everyone! 👋
I'm experiencing a strange caching issue with Turborepo and need help understanding if this is expected behavior or a bug.
## The Problem
Cache miss on consecutive builds when `.next` folder exists. Cache only works after manually deleting `.next`, even though the hash is identical.
## Environment
- **turbo:** 2.6.3
- **next:** 16.0.1
- **pnpm:** 9.14.2
- **Node:** 22.19.0
- **OS:** Windows 11
## How to Reproduce
```bash
# Step 1: Clean everything
rm -rf apps/*/.next apps/*/.turbo .turbo
# Step 2: First build
pnpm build
# Result: cache miss ✅ (expected)
# Step 3: Build again immediately (no changes)
pnpm build
# Expected: cache hit
# Actual: cache miss ❌
# Step 4: Delete .next folders
rm -rf apps/*/.next
# Step 5: Build again
pnpm build
# Result: cache hit ✅ (3.7s - FULL TURBO)
# Step 6: Build again immediately
pnpm build
# Expected: cache hit
# Actual: cache miss ❌ (38s)

The Strange Part

Same hash, different results:
After deleting .next:

web#build > cache hit, replaying logs 1a6444a677c8bb2c
Time: 3.714s >>> FULL TURBO

Immediate next build:

web#build > cache miss, executing 1a6444a677c8bb2c
Time: 38.036s

Hash 1a6444a677c8bb2c is identical both times! 🤔

My Configuration

turbo.json

{
  "$schema": "https://turbo.build/schema.json",
  "ui": "tui",
  "tasks": {
    "//#biome-lint": {
      "inputs": [
        "apps/**/*.{ts,tsx,js,jsx}",
        "packages/**/*.{ts,tsx,js,jsx}",
        "biome.json",
        "packages/biome-config/biome.json"
      ],
      "outputs": []
    },
    "//#biome-format": {
      "cache": false,
      "outputs": []
    },
    "//#biome-check": {
      "cache": false,
      "outputs": []
    },
    "type-check": {
      "dependsOn": ["^type-check"],
      "inputs": ["**/*.ts", "**/*.tsx", "tsconfig.json", "tsconfig.*.json"],
      "outputs": []
    },
    "build": {
      "dependsOn": ["^build"],
      "inputs": [
        "$TURBO_DEFAULT$",
        "!Dockerfile*",
        "!*.dockerfile",
        "!.dockerignore",
        "!.next/**"
      ],
      "outputs": [
        ".next/**",
        "!.next/cache/**",
        "!.next/trace/**",
        "!.next/analyze/**",
        "!.next/*.log",
        "!.next/BUILD_ID",
        "!.next/standalone/**/.env*",
        "!.next/standalone/**/node_modules/.cache/**"
      ]
    },
    "dev": {
      "cache": false,
      "persistent": true
    }
  }
}

next.config.ts (same for both apps)

import type { NextConfig } from 'next'
import { dirname, join } from 'node:path'
import { fileURLToPath } from 'node:url'
const Filename = fileURLToPath(import.meta.url)
const Dirname = dirname(Filename)
const nextConfig: NextConfig = {
  output: 'standalone',
  outputFileTracingRoot: join(Dirname, '../../'),
  transpilePackages: ['@repo/ui'],
  reactStrictMode: true,
  compress: true,
}
export default nextConfig

Project Structure

turborepo/
├── apps/
│   ├── web/
│   │   └── next.config.ts
│   └── docs/
│       └── next.config.ts
├── packages/
│   └── ui/
├── turbo.json
└── package.json

What I’ve Tried

Attempt	Result
Added !.next/** to inputs	Still cache miss
Excluded .next/cache/** from outputs	Still cache miss
Excluded multiple .next subfolders	Still cache miss
Restarted turbo daemon	Still cache miss
Cleared all caches	Still cache miss
Deleted .next before build	✅ Cache works!

Current Workaround

{
  "scripts": {
    "build": "rimraf apps/*/.next && turbo run build"
  }
}

This works but defeats the purpose of caching.

Questions

1. Is this expected behavior when output folder already exists?
2. Is the output: 'standalone' config affecting cache behavior?
3. Are my output exclusions causing issues?
4. Is outputFileTracingRoot interfering with Turborepo caching?
5. Anyone else experiencing this on Windows?
6. Any proper fix besides deleting .next every time?

Impact

• Every build takes 38s instead of 3.7s (10x slower)
• Local development caching completely broken
• CI/Docker works fine (fresh environment each time)
  Thanks for any help! 🙏

## Current vs Expected Behavior
### Expected Behavior
When running `pnpm build` consecutively without any code changes:
- First build: cache miss (expected - no cache exists)
- Second build: **cache hit** (should restore from cache)
- Third build: **cache hit** (should restore from cache)
Build time with cache hit: ~3.7s (FULL TURBO)
### Current Behavior
When running `pnpm build` consecutively without any code changes:
- First build: cache miss ✅
- Second build: **cache miss** ❌ (rebuilds everything)
- Third build: **cache miss** ❌ (rebuilds everything)
Build time: ~38s every time
### The Workaround That Works
If I delete `.next` folder before building:
- `rm -rf apps/*/.next`
- `pnpm build` → **cache hit** ✅ (3.7s)
But immediately running `pnpm build` again → **cache miss** ❌
### Summary
| Scenario | Expected | Actual |
|----------|----------|--------|
| `.next` doesn't exist | cache hit | ✅ cache hit |
| `.next` exists | cache hit | ❌ cache miss |
The cache only works when the output folder doesn't exist, even though the hash is identical.

## Steps to Reproduce
**Repository:** https://github.com/PSriVignesH/turborepo-remote-cache
```bash
# 1. Clone
git clone https://github.com/PSriVignesH/turborepo-remote-cache
cd turborepo-remote-cache
pnpm install
# 2. Login to Vercel Remote Cache
npx turbo login
# 3. Link to Remote Cache
npx turbo link
# 4. First build
pnpm build
# Result: cache will be hit✅ 
# 5. Second build (no changes)
pnpm build
# Result: cache HIT for both ✅
# 7. Make a small change to apps/web/app/page.tsx (add a comment or space)
# 8. Build again
pnpm build
# Expected: cache miss for web, cache HIT for docs
# Actual: cache miss for web ✅, cache miss for docs ❌ (BUG!)
# 9. Build again (no changes)
pnpm build
# Expected: cache hit for both
# Actual: cache miss for both ❌ (BUG!)
# 10. Delete .next folders
rm -rf apps/*/.next
# 11. Build again
pnpm build
# Result: cache HIT for both ✅ (works!)
# 12. Build again (with .next existing)
pnpm build
# Expected: cache hit for both
# Actual: cache miss for both ❌ (BUG!)

# Complete Copy-Paste Ready
```markdown
## Project Information
**Repository:** https://github.com/PSriVignesH/turborepo-remote-cache
### Framework & Versions
| Package | Version |
|---------|---------|
| turbo | 2.6.3 |
| next | 16.0.1 |
| pnpm | 9.x |
| node | 22.19.0 |
### Environment
| Setting | Value |
|---------|-------|
| OS | Windows 11 (Git Bash/MINGW64) |
| Remote Cache | Vercel (enabled via `turbo login` & `turbo link`) |
| Build Mode | Standalone (`output: 'standalone'`) |
### Project Structure

turborepo-remote-cache/
├── apps/
│ ├── web/ # Next.js 16.0.1
│ │ ├── next.config.ts
│ │ └── app/page.tsx
│ └── docs/ # Next.js 16.0.1
│ ├── next.config.ts
│ └── app/page.tsx
├── packages/
│ └── ui/ # Shared components
├── turbo.json
├── package.json
└── pnpm-workspace.yaml

### Key Configuration
**next.config.ts (both apps):**
```typescript
const nextConfig: NextConfig = {
  output: 'standalone',
  outputFileTracingRoot: join(Dirname, '../../'),
  transpilePackages: ['@repo/ui'],
}

turbo.json build task:

{
  "build": {
    "dependsOn": ["^build"],
    "inputs": ["$TURBO_DEFAULT$", "!.next/**"],
    "outputs": [".next/**", "!.next/cache/**"]
  }
}

Remote Cache Settings

• Logged in via npx turbo login
• Linked via npx turbo link
• Using Vercel Remote Cache

Additional information

No response

Example

https://github.com/PSriVignesH/turborepo-remote-cache

[tt-a1i]

This is a known issue with Next.js standalone output and Turborepo. The problem is that Next.js modifies files during the build process, and these modifications cause Turborepo to detect changes in the outputs.

Root cause:
With output: "standalone", Next.js writes additional metadata/timestamps to files in .next/. When Turborepo restores from cache, it compares the restored outputs to what's already there. Since Next.js modified files since the last build, Turborepo sees "dirty" outputs and treats it as a miss.

Potential fixes:

1. Use outputFileTracing exclusions

// next.config.ts
const nextConfig = {
  output: "standalone",
  experimental: {
    outputFileTracingExcludes: {
      "*": ["./cache/**"],
    },
  },
};

2. More aggressive output exclusions

"outputs": [
  ".next/standalone/**",
  ".next/static/**",
  "!.next/cache/**",
  "!.next/trace",
  "!.next/package.json",
  "!.next/build-manifest.json"
]

3. Consider using outputFileTracingRoot relative to each app
The root-level outputFileTracingRoot might be causing path-related cache mismatches.

4. Check for timestamps in outputs

# After build, check what files changed
find apps/web/.next -mmin -1 -type f

The files that show up after a build are likely what's invalidating your cache.

5. Alternative: Don't cache standalone output
Since standalone is mainly for deployment, you might only need to cache the actual build artifacts and regenerate standalone on deploy.

[anthonyshew]

Original issue where discussed: #11216