Module Federation (Vite) — shared singleton module evaluated twice

Setup

pnpm install

Run

pnpm --filter remote dev   # http://localhost:5173
pnpm --filter host dev     # http://localhost:5174

Reproduce

Open http://localhost:5174 in a browser with devtools console open.

Configuration

host declares shared-lib as an eager singleton:

shared: {
  'shared-lib': {
    eager: true,
    singleton: true
  }
}

remote declares shared-lib as a (lazy) singleton:

shared: {
  'shared-lib': {
    singleton: true
  }
}

Both host and remote resolve shared-lib to the same 1.0.0 version (a pnpm workspace package).

Expected

[shared-lib] evaluated printed once.

Actual

[shared-lib] evaluated printed twice, from two different URLs:

[shared-lib] evaluated  (http://localhost:5174/@fs/.../packages/shared-lib/index.js:1)
[shared-lib] evaluated  (http://localhost:5173/@fs/.../packages/shared-lib/index.js:1)

Full console output when loading http://localhost:5174:

[vite] connecting...
[vite] connected.
[shared-lib] evaluated                 (localhost:5174)
[vite] connecting...
[vite] connected.
[shared-lib] evaluated                 (localhost:5173)
[remote] importing shared-lib
[remote] evaluated
[host] importing shared-lib
[host] evaluated
[host] remote loaded

No shared-module version-mismatch warning is logged by the federation runtime.

Note on eager

The same double-evaluation occurs regardless of whether remote sets eager: true for shared-lib or not. This repo uses the more conventional pattern (host eager, remote lazy) shown above. A version with eager: true on both host and remote produces the identical result.