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By default, Cowork on 3P authenticates to Google Cloud’s Vertex AI with a credentials file that you distribute to every device (inferenceVertexCredentialsFile). As an alternative, you can configure an interactive Google sign-in. Each user authenticates once with their own Google Workspace account, and the app stores an encrypted refresh token on the device. Use Google sign-in when you want:
  • Per-user attribution in Cloud Audit Logs instead of a single shared service account
  • IAM controlled at the user or group level rather than at the key
  • To avoid distributing and rotating long-lived service-account key files
The sign-in experience uses a Google OAuth client that you create in your own Google Cloud project. Anthropic does not provide or operate an OAuth client for this flow.
Requires Claude Desktop 1.4.0 or later.

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How it works

When inferenceVertexOAuthClientId and inferenceVertexOAuthClientSecret are both set and inferenceVertexCredentialsFile is not, the app shows a Sign in with Google page the first time a user opens the Cowork tab. Clicking the button opens the system browser for a standard Google consent flow, and the app listens on a loopback address for the redirect. On success, the app stores the user’s Google refresh token encrypted with the operating system’s secure storage (Keychain on macOS, DPAPI on Windows) and relaunches into Cowork. At the start of each Cowork session, the app writes an authorized_user Application Default Credentials file (the same format produced by gcloud auth application-default login) into the session sandbox and points GOOGLE_APPLICATION_CREDENTIALS at it. The Google Cloud client library inside the sandbox handles access-token minting and refresh automatically. If the stored refresh token is revoked or expires, or if you deploy a new OAuth client ID, the app clears the stored token and shows the sign-in page again.

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Prerequisites

  • A Google Cloud project with the Vertex AI API enabled, containing the Claude models you intend to serve
  • Admin access to that project to create an OAuth client and grant IAM roles
  • A Google Workspace organization (recommended) so the OAuth consent screen can be set to Internal

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Set up Google sign-in

1

Configure the OAuth consent screen

In the Google Cloud Console for your Vertex project, open APIs & Services → OAuth consent screen.If your project belongs to a Google Workspace organization, select the Internal user type. Internal apps are limited to users in your Workspace and do not require Google verification, regardless of which scopes they request.If the project is not in a Workspace organization, you must use the External user type. Because this flow requests the https://www.googleapis.com/auth/cloud-platform scope, Google classifies the app as using a sensitive scope, and publishing it beyond test users requires Google’s OAuth verification process. For that reason, Internal is strongly recommended for enterprise deployments.
2

Create a Desktop OAuth client

In APIs & Services → Credentials, choose Create credentials → OAuth client ID, and select Desktop app as the application type.Record the generated Client ID (ending in .apps.googleusercontent.com) and Client secret. For installed applications, Google does not treat the client secret as confidential; the flow is protected by PKCE and by the loopback redirect, so it is safe to distribute the secret in a managed configuration profile.You do not need to add redirect URIs. Desktop-app clients permit loopback (http://127.0.0.1:<port>) redirects automatically.
3

Grant users access to Vertex AI

Each signed-in user calls Vertex AI as themselves, so each user’s Google identity needs permission to invoke the model.On the Vertex project, grant the Vertex AI User role (roles/aiplatform.user) to the Google Workspace group that contains your Cowork users, or to individual users. If your organization uses a narrower custom role, it must include at minimum the aiplatform.endpoints.predict permission.
4

Deploy the managed configuration

Add the OAuth client to your Cowork on 3P profile alongside the existing Vertex keys. Leave inferenceVertexCredentialsFile unset; if both are present, the static credentials file takes precedence and the sign-in page is never shown.
<key>inferenceProvider</key>
<string>vertex</string>
<key>inferenceVertexProjectId</key>
<string>your-gcp-project</string>
<key>inferenceVertexRegion</key>
<string>us-east5</string>
<key>inferenceVertexOAuthClientId</key>
<string>1234567890-abc123.apps.googleusercontent.com</string>
<key>inferenceVertexOAuthClientSecret</key>
<string>GOCSPX-xxxxxxxxxxxxxxxxxxxx</string>
<key>inferenceModels</key>
<string>["claude-sonnet-4@20250514"]</string>
The easiest path is to enter these values in the in-app configuration window (Developer → Configure third-party inference) on an evaluation device, then export. See Installation and setup.
5

Allow network egress

The sign-in flow and subsequent token refreshes reach accounts.google.com and oauth2.googleapis.com from the user’s device. These hosts are already included in the standard Vertex AI egress requirements, so if you allowed egress based on the Egress Requirements section of the configuration window, no additional firewall changes are needed.

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User experience

On first launch after the configuration is applied, the Cowork tab shows a Sign in with Google page instead of the task composer. The user clicks the button, approves access in their default browser, and the app relaunches into Cowork automatically. The browser flow runs on the host, outside the Cowork sandbox, so it can use the user’s existing Google session and any security keys or passkeys configured on the device. Users stay signed in across app restarts. To sign out, a user can revoke access for your OAuth client from their Google Account’s third-party connections page; the app detects the revoked token at the next session start and shows the sign-in page again.

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Configuration keys

SettingTypeDescription
Vertex OAuth client ID
inferenceVertexOAuthClientId		stringClient ID of the Desktop-app OAuth client in your GCP project. Must be set together with the client secret.
Vertex OAuth client secret
inferenceVertexOAuthClientSecret		stringClient secret for the OAuth client above. Not treated as confidential for installed apps; PKCE protects the flow.
Vertex OAuth scopes
inferenceVertexOAuthScopes		stringSpace-separated OAuth scopes requested during sign-in. Defaults to openid email https://www.googleapis.com/auth/cloud-platform. Override only if your organization’s access policies restrict the default scope.
See Using Cowork on 3P with Google Cloud’s Vertex AI for the full list of Vertex keys.

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Notes and limitations

  • Precedence. If inferenceVertexCredentialsFile is set, it is used and Google sign-in is disabled. Remove that key to switch an existing deployment to per-user sign-in.
  • Both keys required. If only one of inferenceVertexOAuthClientId or inferenceVertexOAuthClientSecret is set, the app logs a warning and falls back to standard Application Default Credentials discovery.
  • Credential helper not applicable. inferenceCredentialHelper is not invoked when inferenceProvider is vertex, because Vertex authentication is file-based rather than token-based. Use Google sign-in or a credentials file instead.
  • Client rotation. If you replace the OAuth client in Google Cloud and push the new client ID via MDM, existing users are automatically signed out and prompted to sign in again on next launch.