Claude Code on Google Cloud's Agent Platform changedgoogle-vertex-ai
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### When a model is disabled mid-session
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266266Model aliases such as `opus` don't act as pins, and neither does a model ID Claude Code doesn't recognize.
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268When these checks find a model your project can't invoke, Claude Code remembers the refusal on this machine for up to a day, and launches during that time skip the remembered model without asking Agent Platform again. Claude Code checks a remembered refusal of a current default model again at launch once ten minutes have passed since the last check, so a default your administrator re-enables comes back. To turn the memory off, set [`CLAUDE_CODE_SKIP_MODEL_ACCESS_MEMORY=1`](/docs/en/env-vars).
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270### When a model is disabled mid-session
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272If your project loses access to the model your session is running on, for example because an administrator disables it in [Model Garden](https://console.cloud.google.com/vertex-ai/model-garden), Claude Code switches the session to another model instead of failing each request, and shows `Switched to <fallback> because <model> is not available`. It tries the same models as the startup fallback: earlier versions of the same tier first and, for an Opus session with no Opus version available, the default Sonnet model.
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274The switch applies only to a tier you haven't pinned, the same condition as the startup fallback. A session on a specific version you picked keeps its model and, without a fallback model chain, the request fails instead. In [auto mode](/docs/en/permission-modes#enable-auto-mode-on-bedrock-agent-platform-or-foundry), Claude Code switches only to a model auto mode supports on Agent Platform. If none of those models is available either, the request fails.
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276A [fallback model chain](/docs/en/model-config#fallback-model-chains) you configure replaces the tier switch: on these refusals Claude Code switches to your configured fallback instead. To have refused requests fail rather than switch, set [`CLAUDE_CODE_DISABLE_MODEL_ACCESS_FALLBACK=1`](/docs/en/env-vars). A fallback chain you configured still switches on these refusals; remove the chain as well if you want every refused request to fail.
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268278## IAM configuration
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270280Assign the `roles/aiplatform.user` role, which includes the required permissions:
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