Lightning Login and Built-in Authenticator (Passkey) Conflict Causing Login Deadlock

This error occurs due to a conflict between Lightning Login and Built-in Authenticator (passkey) being registered simultaneously on the same user account.

How Each Method Works

Why the Conflict Occurs

When both methods are present, Salesforce cannot determine which satisfies the required session security level:

• Lightning Login cannot elevate the session to High Assurance
• The passkey requires High Assurance to proceed

The error message indicates:

1. The current method (Lightning Login) does not meet the required session security level
2. The passkey is registered but unreachable because the session level requirement is not met first

Root Cause
Lightning Login establishes a Standard-level session which cannot satisfy the High Assurance requirement needed for passkey verification — causing a deadlock where neither method alone can complete the login.

Background — Why Lightning Login Gets Enabled 

Lightning Login requires Allow Lightning Login to be enabled in Setup > Session Settings. It is commonly observed that Lightning Login becomes active when a user registers Salesforce Authenticator (v2 or later), as the app supports Lightning Login enrollment — however this is not the only path and may vary per user.