One Login to Rule Them All: Cross-App Access for MCP#
AI Engineer Europe 2026 digest Program Adjacent pick 8–10 April 2026
Garrett Galow
- Why: Agent-to-service authentication is heading for a credential-management mess — a dozen OAuth consent screens and token lifecycles per agent. Cross-App Access is the standards-level fix, and agent identity beyond MCP is an emerging infrastructure topic.
- What: Cross-App Access leveraging three-way trust between MCP client, MCP server, and the organization's IdP: the IdP brokers a token exchange from the user's initial SSO login, so one sign-in yields access tokens across every MCP server. Includes an end-to-end demo of the Identity Assertion Authorization Grant flow.
- How: OAuth token exchange brokered by the IdP (the Identity Assertion Authorization Grant), extending SSO across the MCP tool ecosystem.
- Where applicable: A standards-level (OAuth/OIDC ecosystem) pattern, broadly applicable wherever agents consume APIs; no affiliation given in the program.