ID-JAG Deep Dive

Introduction Lately, while following discussions about AI agent architectures and integration patterns, I keep seeing the keyword "ID-JAG" pop up. When an LLM agent calls an external SaaS API on behalf of a user, the biggest wall it hits is the authorization flow. Traditional OAuth requires "redirecting the user to a browser to get consent," but this fundamentally doesn't work for AI agents. Agents don't have a browser UI, and you can't expect an autonomous process to wait for a manual consent click. How do you achieve secure cross-domain API access without user interaction (no-consent)? ID-JAG (Identity Assertion JWT Authorization Grant) is the IETF's new approach to this problem. The core idea is simple: "Extend the trust relationship already established through SSO with an IdP (Identity Provider) to API integration as well." Background: The Relationship Between OAuth 2.0 and SSO To understand ID-JAG, you first need to understand the relationship between OAuth 2.0 and SSO (Single Sig