RegulusFirestoreSessionService¶

In one sentence¶

A drop-in replacement for ADK's FirestoreSessionService adding region pinning, field-level encryption hooks, and an audited erasure path for GDPR Art. 17.

What it does¶

Wraps the Firestore-backed SessionService and adds:

Region pinning. Constructor refuses to start if the Firestore database's location isn't on the allowlist. (Default Firestore databases sit in nam5 — US multi-region — which the plugin catches.)
Erasure path. deleteSession(sessionId) removes the session payload and writes a tombstone event into the audit log. The tombstone records that an erasure happened without leaking what was erased.
Field-level encryption hooks. Optional callbacks to encrypt session fields before they hit Firestore — useful when CMEK at rest isn't enough (e.g. cross-team Firestore access).

When to use it¶

When you need session continuity across instances and you don't have Vertex AI managed sessions on the same project, or when you want field- level encryption beyond what CMEK provides.

Code¶

regulus:
  adk:
    session-service:
      kind: firestore
      project-id: ${GOOGLE_CLOUD_PROJECT}
      location: europe-west2

In bare Java:

RegulusFirestoreSessionService sessions = RegulusFirestoreSessionService.wrap(
    projectId, "europe-west2", profile.residency());

Failure modes¶

Default Firestore in nam5 → constructor throws.
Region mismatch with the Vertex location → not caught here, but flagged at runtime by RegulusDataResidencyPlugin.