`clasp deploy` fails with "Request is missing required authentication credential" despite valid custom OAuth credentials (v3.1.3) and working `clasp push`

[irrelevantat]

I am unable to deploy an existing Google Apps Script project using clasp deploy. While clasp push works perfectly, deploy consistently fails with an authentication error.

Error:

Request is missing required authentication credential. Expected OAuth 2 access token, login cookie or other valid authentication credential. See https://developers.google.com/identity/sign-in/web/devconsole-project.

This project uses a standalone script that was previously working for over a year. Recently, deployment started failing. I have attempted to perform a "hard reset" of authentication by creating a new Google Cloud Project, new OAuth Client ID (Desktop), and using a fresh creds.json, but the issue persists.

Environment:

• Clasp Version: 3.1.3
• Script Type: Standalone
• Deployment Config: Web App (access: ANYONE_ANONYMOUS, executeAs: USER_DEPLOYING)

Configuration

appsscript.json:

{
  "timeZone": "Europe/Berlin",
  "dependencies": {
    "enabledAdvancedServices": [
      {
        "userSymbol": "Drive",
        "version": "v2",
        "serviceId": "drive"
      }
    ]
  },
  "exceptionLogging": "STACKDRIVER",
  "runtimeVersion": "V8",
  "webapp": {
    "executeAs": "USER_DEPLOYING",
    "access": "ANYONE_ANONYMOUS"
  }
}