Issue: SAML 2.0 with Google Workspace – “Invalid authentication provider” on callback

[trplgit-tech]

When using Wiki.js (self-hosted via Docker) with Google Workspace (Custom SAML App), the IdP-initiated SAML flow reaches Wiki.js successfully, but Wiki.js fails at the ACS callback with:

Oops, something went wrong…
Invalid authentication provider.

Google authentication succeeds and the SAML response is posted to Wiki.js, but Wiki.js does not bind the response to the configured SAML strategy.

Environment-
Wiki.js version: 3.x (Docker)
Deployment: Self-hosted, Linux, Docker
Authentication strategy: SAML 2.0
Identity Provider: Google Workspace (Custom SAML App)
HTTPS: Enabled
Browser: Chrome / Edge
OS: Linux server (Docker host)