nextjs - 💡(How to fix) Fix deploymentId: "" breaks Turbopack hydration in next dev [1 comments, 2 participants]

Link to the code that reproduces this issue

https://github.com/bragagia/next-deploymentid-empty-string-repro

This is a minimal public App Router repro for the issue.

The same app works if:

• deploymentId is removed
• or deploymentId is undefined
• or dev is run with next dev --webpack

To Reproduce

1. Clone the repro repo:

git clone https://github.com/bragagia/next-deploymentid-empty-string-repro.git
cd next-deploymentid-empty-string-repro
npm install

1. Run the Turbopack dev server:

npm run dev

1. Open http://localhost:3000.
2. Click the Count: 0 button.

Current vs. Expected behavior

Current behavior:

• The page renders server-side, but client interactivity never hydrates.
• Clicking the client button does nothing.
• In a more complex app, sidebar toggles, dropdowns, and other client interactions were inert.
• When a component triggered a server action on mount, I also saw: Internal Next.js error: Router action dispatched before initialization.

Expected behavior:

• deploymentId: "" should either behave like "unset" or at least not break hydration.
• Client components should hydrate normally under Turbopack dev.

Provide environment information

Operating System:
  Darwin arm64
  macOS 26.3

Node.js version:
  v22.22.2

npm version:
  10.9.7

Next.js version:
  16.1.6

React version:
  19.2.3

react-dom version:
  19.2.3

Which area(s) are affected? (Select all that apply)

Turbopack App Router Dev server Configuration

Additional context

I verified the repro locally before publishing it:

• npm run dev leaves the button inert under Turbopack dev
• npm run dev:webpack increments the same button normally

The breaking condition was specifically that deploymentId resolved to the empty string.

For example, this broke hydration:

deploymentId: process.env.GITHUB_SHA ?? ""

This did not break hydration:

deploymentId:
  process.env.GITHUB_SHA && process.env.GITHUB_SHA !== ""
    ? process.env.GITHUB_SHA
    : undefined

In the same project, next dev --webpack worked normally, so this appears Turbopack-specific.