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Prerequisites

Before configuring Claude Code with Google Cloud’s Agent Platform, formerly Vertex AI, ensure you have:
  • A Google Cloud Platform (GCP) account with billing enabled
  • A GCP project with Google Cloud’s Agent Platform API enabled
  • Access to desired Claude models (for example, Claude Sonnet 4.6)
  • Google Cloud SDK (gcloud) installed and configured
  • Quota allocated in desired GCP region
To sign in with your own Google Cloud’s Agent Platform credentials, follow Sign in with Google Cloud’s Agent Platform below. To deploy Claude Code across a team, use the manual setup steps and pin your model versions before rolling out.

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Sign in with Agent Platform

If you have Google Cloud credentials and want to start using Claude Code through Google Cloud’s Agent Platform, the login wizard walks you through it. You complete the GCP-side prerequisites once per project; the wizard handles the Claude Code side.
1

Enable Claude models in your GCP project

Enable Google Cloud’s Agent Platform API for your project, then request access to the Claude models you want in the Google Cloud’s Agent Platform Model Garden. See IAM configuration for the permissions your account needs.
2

Start Claude Code and choose Google Cloud's Agent Platform

Run claude. At the login prompt, select 3rd-party platform, then Google Vertex AI, the label the login prompt still uses for Google Cloud’s Agent Platform. If you’re already signed in, run /login to open the same menu.
3

Follow the wizard prompts

Choose how you authenticate to Google Cloud: Application Default Credentials from gcloud, a service account key file, or credentials already in your environment. The wizard detects your project and region, verifies which Claude models your project can invoke, and lets you pin them. It saves the result to the env block of your user settings file, so you don’t need to export environment variables yourself.
After you’ve signed in, run /setup-vertex any time to reopen the wizard and change your credentials, project, region, or model pins. The model pin step starts from your currently pinned models. The wizard writes to ~/.claude/settings.json, or to $CLAUDE_CONFIG_DIR/settings.json when CLAUDE_CONFIG_DIR is set.

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Region configuration

Claude Code supports Google Cloud’s Agent Platform global, multi-region, and regional endpoints. Set CLOUD_ML_REGION to global, a multi-region location such as eu or us, or a specific region such as us-east5. Claude Code selects the correct Google Cloud’s Agent Platform hostname for each form, including the aiplatform.eu.rep.googleapis.com and aiplatform.us.rep.googleapis.com hosts for multi-region locations.
Google Cloud’s Agent Platform may not support the Claude Code default models on every endpoint type. Model availability varies across specific regions, multi-region locations, and global endpoints. You may need to switch to a supported location or specify a supported model.

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Set up manually

To configure Google Cloud’s Agent Platform through environment variables instead of the wizard, for example in CI or a scripted enterprise rollout, follow the steps below.

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1. Enable Agent Platform API

Enable Google Cloud’s Agent Platform API in your GCP project. Replace YOUR-PROJECT-ID with your GCP project ID here and in the configuration step below:

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2. Request model access

Request access to Claude models in Google Cloud’s Agent Platform:
  1. Navigate to the Google Cloud’s Agent Platform Model Garden
  2. Search for “Claude” models
  3. Request access to desired Claude models (for example, Claude Sonnet 4.6)
  4. Wait for approval (may take 24-48 hours)

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3. Configure GCP credentials

Claude Code uses standard Google Cloud authentication. For more information, see Google Cloud authentication documentation. Claude Code v2.1.121 or later supports X.509 certificate-based Workload Identity Federation through the same Application Default Credentials chain. Set GOOGLE_APPLICATION_CREDENTIALS to the path of your credential configuration file.
Claude Code uses ANTHROPIC_VERTEX_PROJECT_ID as the project ID for Google Cloud’s Agent Platform requests. The GCLOUD_PROJECT and GOOGLE_CLOUD_PROJECT environment variables and the credential file referenced by GOOGLE_APPLICATION_CREDENTIALS take precedence over it. If none of these are set, the project ID is resolved from your gcloud configuration or the attached service account.

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Advanced credential configuration

Claude Code supports automatic credential refresh for GCP through the gcpAuthRefresh setting. Add it to your Claude Code settings file, for example ~/.claude/settings.json. When Claude Code detects that your GCP credentials are expired or cannot be loaded, it runs the configured command to obtain new credentials before retrying the request.
The command’s output is displayed to the user, but interactive input isn’t supported. This works well for browser-based authentication flows where the CLI shows a URL and you complete authentication in the browser. The refresh command times out after three minutes if authentication does not complete. If you set gcpAuthRefresh in project settings such as .claude/settings.json, the command runs only after you accept the workspace trust prompt.

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4. Configure Claude Code

Set the following environment variables:
Most model versions have a corresponding VERTEX_REGION_CLAUDE_* variable. See the Environment variables reference for the full list. Check Google Cloud’s Agent Platform Model Garden to determine which models support global endpoints versus regional only. Prompt caching is enabled automatically. To disable it, set DISABLE_PROMPT_CACHING=1. To request a 1-hour cache TTL instead of the 5-minute default, set ENABLE_PROMPT_CACHING_1H=1; cache writes with a 1-hour TTL are billed at a higher rate. For heightened rate limits, contact Google Cloud support. When using Google Cloud’s Agent Platform, the /logout command is unavailable since authentication is handled through Google Cloud credentials. Claude Code disables MCP tool search by default on Google Cloud’s Agent Platform, so MCP tool definitions load upfront. Google Cloud’s Agent Platform supports tool search for Claude Sonnet 4.5 and later and Claude Opus 4.5 and later. Set ENABLE_TOOL_SEARCH=true to enable it on those models. Earlier models on Google Cloud’s Agent Platform do not accept the required beta header, and requests fail if you enable tool search with them.

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5. Pin model versions

Pin specific model versions when deploying to multiple users. Without pinning, model aliases such as sonnet and opus resolve to Claude Code’s built-in default for Google Cloud’s Agent Platform, which can lag the newest release and may not yet be enabled in your project. Claude Code falls back to an earlier or lower-tier model at startup when the default is unavailable, but pinning lets you control when your users move to a new model.
Set these environment variables to specific Google Cloud’s Agent Platform model IDs. Without ANTHROPIC_DEFAULT_OPUS_MODEL, the opus alias on Google Cloud’s Agent Platform resolves to Opus 4.8, and without ANTHROPIC_DEFAULT_SONNET_MODEL, the sonnet alias resolves to Sonnet 4.5. This example pins each alias to a specific version:
For current and legacy model IDs, see Models overview. See Model configuration for the full list of environment variables. Claude Code uses these default models when no pinning variables are set: Background tasks such as session title generation use the small/fast model, normally a Haiku-class model. On Google Cloud’s Agent Platform, Claude Code uses the default Sonnet model for background tasks because Haiku may not be enabled in every project or region. Two selections change which model carries them:
  • When you select a primary model with --model, ANTHROPIC_MODEL, or the model setting, background tasks use that model. Setting ANTHROPIC_DEFAULT_OPUS_MODEL without ANTHROPIC_DEFAULT_SONNET_MODEL counts as a selection too, because the built-in Sonnet model may not be enabled in a project that steers its own Opus.
  • To use Haiku for background tasks, set ANTHROPIC_DEFAULT_HAIKU_MODEL to a model ID that is available in your project.
Opus models have a higher per-token price than Sonnet models, so a deployment that doesn’t pin a primary model is billed at the Opus rate once it updates to v2.1.207 or later. To keep Sonnet 4.5 as the primary model, set ANTHROPIC_MODEL to its full model ID. A deployment that steers the default with ANTHROPIC_DEFAULT_SONNET_MODEL and doesn’t set ANTHROPIC_DEFAULT_OPUS_MODEL keeps its steered Sonnet model as the default.
Before v2.1.207, the primary model on Google Cloud’s Agent Platform defaulted to Sonnet 4.5, the opus alias resolved to Opus 4.6, and background tasks always used the primary model. To customize models further:

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6. Verify your configuration

Start Claude Code and run /status to confirm the setup. The API provider line shows Google Vertex AI, and the GCP project, Default region, and Model lines show your project ID, region, and resolved model. If the provider line is missing, the environment variables aren’t reaching the process. Confirm they are exported in the shell where you launched claude, or set them in the env block of your settings file.

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Startup model checks

When Claude Code starts with Google Cloud’s Agent Platform configured, it verifies that the models it intends to use are accessible in your project. If you have pinned a model version that is older than the current Claude Code default, and your project can invoke the newer version, Claude Code prompts you to update the pin. Accepting writes the new model ID to your user settings file and restarts Claude Code. Declining is remembered until the next default version change. If you have not pinned a model and the current default is unavailable in your project, Claude Code falls back for the current session and shows a notice. It tries earlier versions of the default model first and, when the default is an Opus model and no Opus version is available, falls back to the default Sonnet model. The fallback is not persisted. Enable the newer model in Model Garden or pin a version to make the choice permanent. When you start the session on a specific Sonnet or Opus version, with --model, ANTHROPIC_MODEL, or the model setting, that version acts as the session’s pinned default for the matching sonnet or opus alias. Claude Code skips the availability check for the built-in default your model replaces and starts on the model you configured, with no fallback notice. Model aliases such as opus don’t act as pins, and neither does a model ID Claude Code doesn’t recognize.
Before v2.1.211, Claude Code checked the default model’s availability even when a session model was explicitly configured, and could show a fallback notice for a default the session didn’t use.

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IAM configuration

Assign the required IAM permissions: The roles/aiplatform.user role includes the required permissions:
  • aiplatform.endpoints.predict - Required for model invocation and token counting
For more restrictive permissions, create a custom role with only the permissions above. For details, see Google Cloud’s Agent Platform IAM documentation.
Create a dedicated GCP project for Claude Code to simplify cost tracking and access control.

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1M token context window

Claude Sonnet 5, Opus 4.6 and later, and Sonnet 4.6 support the 1M token context window on Google Cloud’s Agent Platform. Sonnet 5 always runs with the 1M window, with no [1m] variant to select. For the other models, Claude Code automatically enables the extended context window when you select a 1M model variant. The setup wizard offers a 1M context option when it pins models. To enable it for a manually pinned model instead, append [1m] to the model ID. See Pin models for third-party deployments for details.

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Troubleshooting

If you encounter “Could not load the default credentials” errors:
  • Run gcloud auth application-default login to set up Application Default Credentials
  • Set GOOGLE_APPLICATION_CREDENTIALS to a service account key file path
  • See Configure GCP credentials for all options
If you encounter quota issues:
  • Check current quotas or request quota increase through Cloud Console
If you encounter “model not found” 404 errors:
  • Confirm model is Enabled in Model Garden
  • Verify the model is available in the location you specified. Some models are offered only on global or multi-region locations such as eu and us, not in specific regions
  • If using CLOUD_ML_REGION=global, check that your models support global endpoints in Model Garden under “Supported features”. For models that don’t support global endpoints, either:
    • Specify a supported model via ANTHROPIC_MODEL or ANTHROPIC_DEFAULT_HAIKU_MODEL, or
    • Set a region or multi-region location using VERTEX_REGION_<MODEL_NAME> environment variables
If you encounter 429 errors:
  • For regional endpoints, ensure the primary model and small/fast model are supported in your selected region
  • Consider switching to CLOUD_ML_REGION=global for better availability

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Additional resources