diff --git a/server/routers/auth.py b/server/routers/auth.py
index ccae963..3ecdcef 100644
--- a/server/routers/auth.py
+++ b/server/routers/auth.py
@@ -245,11 +245,23 @@ async def register(
             )
 
     # --- Invite code validation ---
+    is_test_account = False
     if has_invite:
         if not _admin_service:
             raise HTTPException(status_code=503, detail="Admin service not initialized")
         if not await _admin_service.validate_invite_code(request_body.invite_code):
             raise HTTPException(status_code=400, detail="Invalid or expired invite code")
+        # Check if this invite flags new accounts as test accounts
+        invite_details = await _admin_service.get_invite_code_details(request_body.invite_code)
+        if invite_details and invite_details.get("marks_as_test"):
+            is_test_account = True
+            logger.info(
+                "test_seed_account_registering",
+                extra={
+                    "username": request_body.username,
+                    "invite_code": request_body.invite_code,
+                },
+            )
     else:
         # No invite code — check if open signups are allowed
         if config.INVITE_ONLY and config.DAILY_OPEN_SIGNUPS == 0:
@@ -277,6 +289,7 @@ async def register(
         username=request_body.username,
         password=request_body.password,
         email=request_body.email,
+        is_test_account=is_test_account,
     )
 
     if not result.success:
diff --git a/server/services/auth_service.py b/server/services/auth_service.py
index 6f7b2ac..794b1ba 100644
--- a/server/services/auth_service.py
+++ b/server/services/auth_service.py
@@ -101,6 +101,7 @@ class AuthService:
         password: str,
         email: Optional[str] = None,
         guest_id: Optional[str] = None,
+        is_test_account: bool = False,
     ) -> RegistrationResult:
         """
         Register a new user account.
@@ -110,6 +111,7 @@ class AuthService:
             password: Plain text password.
             email: Optional email address.
             guest_id: Guest session ID if converting.
+            is_test_account: Mark this user as a soak-harness test account.
 
         Returns:
             RegistrationResult with user or error.
@@ -151,6 +153,7 @@ class AuthService:
             guest_id=guest_id,
             verification_token=verification_token,
             verification_expires=verification_expires,
+            is_test_account=is_test_account,
         )
 
         if not user: