Babel configs on "<CWD>/src/foo.js" (ascending priority):
config <CWD>/babel.config.json
{
  "sourceType": "script"
}

config <CWD>/babel.config.json .overrides[0]
{
  "test": "src/foo.js",
  "sourceType": "module"
}

config <CWD>/.babelrc
{}

programmatic options from @babel/cli
{
  "presets": [
    "<ROOTDIR>//packages//babel-preset-react"
  ],
  "plugins": [
    "<ROOTDIR>//packages//babel-plugin-transform-arrow-functions",
    "<ROOTDIR>//packages//babel-plugin-transform-strict-mode",
    "<ROOTDIR>//packages//babel-plugin-transform-modules-commonjs"
  ],
  "sourceFileName": "../src/foo.js",
  "caller": {
    "name": "@babel/cli"
  },
  "filename": "src//foo.js"
}
Successfully compiled 1 file with Babel (123ms).
