Databricks Apps Cookie Authentication

Problem Solved

Databricks Apps that require browser-based OAuth cannot be accessed with service principals or PATs when the app is configured for "User Authorization" only. The app always redirects to OAuth login regardless of Bearer tokens sent.

Solution: Cookie-Based Authentication

After a user completes browser OAuth login, Databricks Apps set a session cookie __Host-databricksapps that can be captured and reused for API access.

How It Works

1. User logs into the Databricks App via browser
2. Browser receives __Host-databricksapps cookie after successful OAuth
3. Cookie is captured from browser DevTools (Application > Cookies)
4. Cookie is passed as header in MCP client requests

Cookie Format

__Host-databricksapps=<encrypted_session_data>|<timestamp>|<signature>

The timestamp indicates expiry - cookies typically expire after a session timeout.

Code Example

from mcp.client.session import ClientSession
from mcp.client.streamable_http import streamablehttp_client
from datetime import timedelta

async def connect_with_cookie(url: str, cookie_value: str):
    http_context = streamablehttp_client(
        url,
        headers={'Cookie': f'__Host-databricksapps={cookie_value}'}
    )
    read, write, _ = await http_context.__aenter__()

    session = ClientSession(read, write, read_timeout_seconds=timedelta(seconds=60))
    await session.__aenter__()
    await session.initialize()

    tools = await session.list_tools()
    return tools

When to Use This

• Databricks Apps with "User Authorization" enabled but no service principal access
• Apps that redirect to OAuth regardless of Bearer tokens
• Testing/development scenarios where HITL OAuth isn't implemented yet

Limitations

1. Session Expiry: Cookies expire, requiring periodic browser re-login
2. User-Specific: Cookie is tied to the user who logged in
3. Security: Cookie contains sensitive session data - handle securely

Relevant Files

• penguiflow/tools/node.py - ToolNode implementation
• penguiflow/tools/config.py - AuthType enum
• test_generation/reporting-agent/src/reporting_agent/external_tools.py - Example usage

Related Auth Types