Bun "node:X is not yet implemented in Bun" in CI

Bun explicitly reports that a Node built-in module or a specific function is "not yet implemented in Bun". The feature is on Bun's roadmap but unavailable now, so the call fails at runtime.

What this error means

A step throws an error containing "is not yet implemented in Bun. Track the status..." when code touches an unsupported node: module or API.

error: node:cluster is not yet implemented in Bun. Track the status &
thumbs up the issue: https://github.com/oven-sh/bun/issues/2492

Common causes

The code imports an unimplemented node: module

A node: built-in (or a specific export from one) that Bun has not implemented is imported, so Bun throws with a tracking link.

A dependency pulls in the unsupported module

A transitive dependency imports the unimplemented module even if your own code does not touch it directly.

How to fix it

Avoid the unimplemented module

1. Read the error to see exactly which node: module is unsupported.
2. Replace it with a Bun-supported or Web API alternative in your code.
3. Pin a dependency version that does not require the module.

# confirm which node: module the dependency needs
bun run ./scripts/task.ts

Run the affected job on Node

Where the unimplemented module is required, run that job on Node until Bun implements it.

- uses: actions/setup-node@v4
  with:
    node-version: '20'
- run: node ./scripts/task.js

How to prevent it

• Check Bun Node-compatibility status for modules you import.
• Prefer Web/Bun APIs over unimplemented node: built-ins.
• Keep jobs needing unsupported modules on Node runners.

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