Scan a Gemini Vertex agent

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What this example tests

• All 10 ASI categories against a Vertex reasoning engine.
• GCP ADC auth via the [gcp] extra (google-auth).
• The server_session pattern — AgentGuardian reuses the swarm session as Vertex’s session_id so conversation state carries between turns.

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Prerequisites

• AgentGuardian with the GCP extra installed: pip install 'agent-guardian[gcp]'.
• A Vertex AI reasoning engine deployed in your GCP project. See the Vertex AI Agent Engine overview.
• gcloud auth application-default login already run (or a service-account JSON exported via GOOGLE_APPLICATION_CREDENTIALS).
• The project id, location, and reasoning-engine id.

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Run target

export GCP_PROJECT=...
export GCP_LOCATION=us-central1
export VERTEX_REASONING_ENGINE_ID=...

version: 1
target:
  name: gemini-vertex-demo
  environment: staging
  transport:
    kind: vertex_agent
    project: ${env:GCP_PROJECT}
    location: ${env:GCP_LOCATION}
    reasoning_engine_id: ${env:VERTEX_REASONING_ENGINE_ID}
  auth:
    kind: gcp_adc
  response:
    output_path: $.output
roe:
  data_egress:
    allow_external: false

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Run AgentGuardian

agent-guardian scan \
  --contract examples/gemini_agent/agentguardian.yaml \
  --model stub \
  --mode fast \
  --output md \
  --output-path scan.md

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Expected output

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Common errors

• ImportError: google-auth is required for GCP ADC. Install the GCP extra: pip install 'agent-guardian[gcp]'.
• DefaultCredentialsError. ADC is not configured. Run gcloud auth application-default login or set GOOGLE_APPLICATION_CREDENTIALS to a service-account JSON.
• PermissionDenied on :query. The caller principal is missing aiplatform.reasoningEngines.query on the engine. Grant the Vertex AI User role.
• NotFound: reasoning engine .... Project, location, or engine id is wrong. Use gcloud ai reasoning-engines list --region <LOCATION> to confirm.

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Next step

• For an AWS-deployed target, read Scan a Bedrock agent.
• For an in-process Gemini-backed demo (no Vertex deployment required), the LangGraph fixtures under examples/langgraph/ call Gemini via the AI Studio OpenAI shim — see Scan a LangGraph agent.