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python/samples/getting_started/purview_agent/README.md

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+## Purview Policy Enforcement Sample (Python)
+
+This getting-started sample shows how to attach Microsoft Purview policy evaluation to an Agent Framework `ChatAgent` using the **middleware** approach.
+
+**What this sample demonstrates:**
+1. Configure an Azure OpenAI chat client
+2. Add Purview policy enforcement middleware (`PurviewPolicyMiddleware`)
+3. Add Purview policy enforcement at the chat client level (`PurviewChatPolicyMiddleware`)
+4. Implement a custom cache provider for advanced caching scenarios
+5. Run conversations and observe prompt / response blocking behavior
+
+**Note:** Caching is **automatic** and enabled by default with sensible defaults (30-minute TTL, 200MB max size).
+
+---
+## 1. Setup
+### Required Environment Variables
+
+| Variable | Required | Purpose |
+|----------|----------|---------|
+| `AZURE_OPENAI_ENDPOINT` | Yes | Azure OpenAI endpoint (https://<name>.openai.azure.com) |
+| `AZURE_OPENAI_DEPLOYMENT_NAME` | Optional | Model deployment name (defaults inside SDK if omitted) |
+| `PURVIEW_CLIENT_APP_ID` | Yes* | Client (application) ID used for Purview authentication |
+| `PURVIEW_USE_CERT_AUTH` | Optional (`true`/`false`) | Switch between certificate and interactive auth |
+| `PURVIEW_TENANT_ID` | Yes (when cert auth on) | Tenant ID for certificate authentication |
+| `PURVIEW_CERT_PATH` | Yes (when cert auth on) | Path to your .pfx certificate |
+| `PURVIEW_CERT_PASSWORD` | Optional | Password for encrypted certs |
+
+### 2. Auth Modes Supported
+
+#### A. Interactive Browser Authentication (default)
+Opens a browser on first run to sign in.
+
+```powershell
+$env:AZURE_OPENAI_ENDPOINT = "https://your-openai-instance.openai.azure.com"
+$env:PURVIEW_CLIENT_APP_ID = "00000000-0000-0000-0000-000000000000"
+```
+
+#### B. Certificate Authentication
+For headless / CI scenarios.
+
+```powershell
+$env:PURVIEW_USE_CERT_AUTH = "true"
+$env:PURVIEW_TENANT_ID = "<tenant-guid>"
+$env:PURVIEW_CERT_PATH = "C:\path\to\cert.pfx"
+$env:PURVIEW_CERT_PASSWORD = "optional-password"
+```
+
+Certificate steps (summary): create / register entra app, generate certificate, upload public key, export .pfx with private key, grant required Graph / Purview permissions.
+
+---
+
+## 3. Run the Sample
+
+From repo root:
+
+```powershell
+cd python/samples/getting_started/purview_agent
+python sample_purview_agent.py
+```
+
+If interactive auth is used, a browser window will appear the first time.
+
+---
+
+## 4. How It Works
+
+The sample demonstrates three different scenarios:
+
+### A. Agent Middleware (`run_with_agent_middleware`)
+1. Builds an Azure OpenAI chat client (using the environment endpoint / deployment)
+2. Chooses credential mode (certificate vs interactive)
+3. Creates `PurviewPolicyMiddleware` with `PurviewSettings`
+4. Injects middleware into the agent at construction
+5. Sends two user messages sequentially
+6. Prints results (or policy block messages)
+7. Uses default caching automatically
+
+### B. Chat Client Middleware (`run_with_chat_middleware`)
+1. Creates a chat client with `PurviewChatPolicyMiddleware` attached directly
+2. Policy evaluation happens at the chat client level rather than agent level
+3. Demonstrates an alternative integration point for Purview policies
+4. Uses default caching automatically
+
+### C. Custom Cache Provider (`run_with_custom_cache_provider`)
+1. Implements the `CacheProvider` protocol with a custom class (`SimpleDictCacheProvider`)
+2. Shows how to add custom logging and metrics to cache operations
+3. The custom provider must implement three async methods:
+   - `async def get(self, key: str) -> Any | None`
+   - `async def set(self, key: str, value: Any, ttl_seconds: int | None = None) -> None`
+   - `async def remove(self, key: str) -> None`
+
+**Policy Behavior:**
+Prompt blocks set a system-level message: `Prompt blocked by policy` and terminate the run early. Response blocks rewrite the output to `Response blocked by policy`.
+
+---
+
+## 5. Code Snippets
+
+### Agent Middleware Injection
+
+```python
+agent = ChatAgent(
+	chat_client=chat_client,
+	instructions="You are good at telling jokes.",
+	name="Joker",
+	middleware=[
+		PurviewPolicyMiddleware(credential, PurviewSettings(app_name="Sample App"))
+	],
+)
+```
+
+### Custom Cache Provider Implementation
+
+This is only needed if you want to integrate with external caching systems.
+
+```python
+class SimpleDictCacheProvider:
+    """Custom cache provider that implements the CacheProvider protocol."""
+
+    def __init__(self) -> None:
+        self._cache: dict[str, Any] = {}
+
+    async def get(self, key: str) -> Any | None:
+        """Get a value from the cache."""
+        return self._cache.get(key)
+
+    async def set(self, key: str, value: Any, ttl_seconds: int | None = None) -> None:
+        """Set a value in the cache."""
+        self._cache[key] = value
+
+    async def remove(self, key: str) -> None:
+        """Remove a value from the cache."""
+        self._cache.pop(key, None)
+
+# Use the custom cache provider
+custom_cache = SimpleDictCacheProvider()
+middleware = PurviewPolicyMiddleware(
+    credential,
+    PurviewSettings(app_name="Sample App"),
+    cache_provider=custom_cache,
+)
+```
+
+---