Firebase "Failed to load function definition from source" in CI

By Kaveh Alemi·Latchkey

The functions emulator or deploy loader could not import the source module. The compiled entry point is missing, or an import in it fails, so no function definitions can be read.

What this error means

A deploy or emulator start fails with "Error: Failed to load function definition from source: Failed to generate manifest from function source".

Error: Failed to load function definition from source: Failed to generate manifest from function source

Common causes

The compiled entry point is missing

The main field in functions/package.json points at build output that was never produced in CI.

An import in the entry point fails

A missing dependency or a broken relative import stops the module from loading.

How to fix it

Build so the entry point exists

1. Confirm main in functions/package.json matches your build output.
2. Run the build before deploy so that file exists.
3. Deploy after a successful build.

{
  "main": "lib/index.js",
  "scripts": { "build": "tsc" }
}

Verify imports resolve

Install functions dependencies and check relative import paths so the entry module loads cleanly.

How to prevent it

• Keep main pointed at the real build output.
• Build functions before every deploy in CI.
• Install functions dependencies in the functions folder.

Frequently asked questions

Related guides

References

• Terraform documentation
• GitHub Actions documentation