[Bug]: 504 Outdated Optimize Dep errors when using shared dependencies in dev mode

[AlonMiz]

Describe the bug

When using @module-federation/vite with shared dependencies in dev mode, Vite throws "504 Outdated Optimize Dep" errors.

Root Cause: The issue is in src/utils/normalizeOptimizeDeps.ts line 17:

// todo: fix this workaround
optimizeDeps.force = true;

The plugin sets optimizeDeps.force = true, which forces Vite to re-optimize dependencies on every server start. When combined with shared dependencies, this causes a race condition where the federation plugin receives a 504 error because the optimized dependency it was loading becomes "outdated".

Current Workaround: Disable shared dependencies in dev mode:

shared: isDev ? {} : { /* shared deps */ }

Version

• @module-federation/vite: 1.9.4
• vite: 7.3.1

Reproduction

https://github.com/user/analog-federation (Nx monorepo with Angular + React remotes)

Steps:

1. Configure shared dependencies in federation config
2. Run vite dev
3. Observe 504 errors in console

Relevant log output

504 Outdated Optimize Dep

Suggested Fix

Instead of always forcing re-optimization, the plugin should use a smarter invalidation strategy:

Option 1: Hash-based invalidation

Only force re-optimization when the federation config actually changes:

// In normalizeOptimizeDeps.ts
import { createHash } from 'crypto';

function getFederationConfigHash(config: FederationConfig): string {
  const configString = JSON.stringify({
    name: config.name,
    remotes: config.remotes,
    exposes: config.exposes,
    shared: config.shared,
  });
  return createHash('md5').update(configString).digest('hex');
}

// Instead of: optimizeDeps.force = true;
// Check if config changed since last run
const federationHash = getFederationConfigHash(federationConfig);
if (hasFederationConfigChanged(federationHash)) {
  optimizeDeps.force = true;
  saveFederationConfigHash(federationHash);
}

Option 2: Use optimizeDeps.entries instead of force

Pre-specify federation modules without forcing full re-optimization:

// Don't force, instead explicitly include federation entries
// optimizeDeps.force = true; // REMOVE THIS

optimizeDeps.entries = [
  ...(optimizeDeps.entries || []),
  '**/remoteEntry.js',
];

// Include shared deps explicitly
if (federationConfig.shared) {
  optimizeDeps.include = [
    ...(optimizeDeps.include || []),
    ...Object.keys(federationConfig.shared),
  ];
}

Validations

• Read the docs.
• Read the common issues list.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• The provided reproduction is a minimal reproducible example of the bug.

[gioboa]

Thanks for your report 👍 options 2 looks more aligned with the Vite standard configuration. would you like to open a PR for this?

[AlonMiz]

Thanks for your report 👍 options 2 looks more aligned with the Vite standard configuration. would you like to open a PR for this?

Sure, ill try that as soon as i can 🙏

[simonihmig]

Can someone please give me the gist of why the force flag was needed, and what would happen if it weren't enabled?

We weren't affected by the 504 errors so far, but seeing very long startup times for vite dev due to basically having a cold start each time, when pre-bundling needs to happen again each time.