Direct Sign-In boundary

Direct Sign-In upgrades an existing signed-out Session. The personal agent may explain why authorization is needed, but the host—not the model—constructs the OAuth request, stores one-use state, and opens the company's page in a trusted browser.

What the example proves

• State and the verifier come from cryptographically secure randomness.
• Only the S256 challenge crosses to the authorization endpoint.
• The full authorization URL is a secret because it contains state and user intent; it is revealed only to the browser handoff capability.
• The state store must expire entries and support atomic consumption later.
• The company owns the sign-in UI, so the personal agent never receives the user's password.

This example deliberately ends at the browser boundary. Continue with the complete Direct Sign-In lifecycle for callback validation and token exchange.

Run the Pydantic AI example or the Agent Runtimes example.