diff --git a/tests/api/src/auth/project.rs b/tests/api/src/auth/project.rs
index 006ba7459..d24f7422c 100644
--- a/tests/api/src/auth/project.rs
+++ b/tests/api/src/auth/project.rs
@@ -57,3 +57,85 @@ async fn test_list_user_projects() -> Result<()> {
     assert!(!projects.is_empty());
     Ok(())
 }
+
+
+#[tokio::test]
+async fn test_auth_projects_returns_empty_for_user_without_roles() -> Result<()> {
+    // Regression test for issue #515:
+    // When a user has no role assignments, /auth/projects should return
+    // an empty list, not all projects in the system.
+    
+    let mut admin_client = TestClient::default()?;
+    admin_client.auth_admin().await?;
+
+    // Create a domain for the test user
+    let domain_response = admin_client
+        .client
+        .post(admin_client.base_url.join("v3/domains")?)
+        .json(&serde_json::json!({
+            "domain": {
+                "name": format!("test-domain-{}", uuid::Uuid::new_v4()),
+                "enabled": true
+            }
+        }))
+        .send()
+        .await?;
+    
+    let domain: serde_json::Value = domain_response.json().await?;
+    let domain_id = domain["domain"]["id"].as_str().unwrap();
+
+    // Create a user with no role assignments
+    let user_password = "TestPassword123!";
+    let user_response = admin_client
+        .client
+        .post(admin_client.base_url.join("v3/users")?)
+        .json(&serde_json::json!({
+            "user": {
+                "name": format!("test-user-{}", uuid::Uuid::new_v4()),
+                "domain_id": domain_id,
+                "password": user_password,
+                "enabled": true
+            }
+        }))
+        .send()
+        .await?;
+
+    let user: serde_json::Value = user_response.json().await?;
+    let user_id = user["user"]["id"].as_str().unwrap();
+
+    // Authenticate as the user with no roles
+    let mut user_client = TestClient::default()?;
+    user_client
+        .auth_password(
+            PasswordAuthBuilder::default()
+                .user(
+                    UserBuilder::default()
+                        .id(user_id)
+                        .domain(
+                            DomainBuilder::default()
+                                .id(domain_id)
+                                .build()?
+                        )
+                        .build()?
+                )
+                .password(user_password)
+                .build()?,
+            None, // No scope - unscoped auth
+        )
+        .await?;
+
+    // Call /auth/projects - should return empty list
+    let projects = list_auth_projects(&Arc::new(
+        AsyncOpenStack::new(&CloudConfig::from_env()?).await?
+    ))
+    .await?;
+
+    // The user has no role assignments, so projects list should be empty
+    assert!(
+        projects.is_empty(),
+        "User with no role assignments should see no projects. \
+        This may indicate the bug from issue #515 is present (returning all projects instead of empty list)"
+    );
+
+    Ok(())
+}
\ No newline at end of file
diff --git a/tests/integration/src/assignment/grant/list.rs b/tests/integration/src/assignment/grant/list.rs
index 35fa6bccb..f94c0e015 100644
--- a/tests/integration/src/assignment/grant/list.rs
+++ b/tests/integration/src/assignment/grant/list.rs
@@ -200,3 +200,140 @@ async fn test_list_user_roles() -> Result<()> {
     );
     Ok(())
 }
+
+// Add these two tests at the BOTTOM of:
+// tests/integration/src/assignment/grant/list.rs
+// (paste before the last closing brace if any, or just at the end of the file)
+
+#[traced_test]
+#[tokio::test]
+async fn test_list_role_assignments_by_user_same_role_multiple_scopes() -> Result<()> {
+    // Regression test for issue #513:
+    // Assigning the same role to a user on multiple projects + system was
+    // mixing up assignments due to HashMap by role_id. This test verifies
+    // all assignments are returned correctly when listing by user_id only.
+    let (state, _) = get_state().await?;
+
+    let domain = create_domain!(state)?;
+    let project_1 = create_project!(state, domain.id.clone())?;
+    let project_2 = create_project!(state, domain.id.clone())?;
+    let user = create_user!(state, domain.id.clone())?;
+    let role = create_role!(state)?;
+
+    // Assign the SAME role to the user on two different projects AND system
+    for assignment in [
+        AssignmentCreate::user_project(&user.id, &project_1.id, &role.id, false),
+        AssignmentCreate::user_project(&user.id, &project_2.id, &role.id, false),
+        AssignmentCreate::user_system(&user.id, "all", &role.id, false),
+    ] {
+        state
+            .provider
+            .get_assignment_provider()
+            .create_grant(&state, assignment)
+            .await?;
+    }
+
+    // List assignments filtering by user_id ONLY (no target filter)
+    let assignments = state
+        .provider
+        .get_assignment_provider()
+        .list_role_assignments(
+            &state,
+            &RoleAssignmentListParametersBuilder::default()
+                .user_id(user.id.clone())
+                .build()?,
+        )
+        .await?;
+
+    // Should return exactly 3 assignments - one per scope
+    // (Before the fix, HashMap deduplicated by role_id and returned only 1)
+    assert_eq!(
+        assignments.len(),
+        3,
+        "Expected 3 role assignments (same role on project_1 + project_2 + system), got {}. \
+        This may indicate the HashMap bug from issue #513 is present.",
+        assignments.len()
+    );
+
+    // Verify both project targets are present
+    let target_ids: BTreeSet<String> = assignments.iter().map(|a| a.target_id.clone()).collect();
+    assert!(
+        target_ids.contains(&project_1.id),
+        "Assignment on project_1 should be present"
+    );
+    assert!(
+        target_ids.contains(&project_2.id),
+        "Assignment on project_2 should be present"
+    );
+
+    Ok(())
+}
+
+#[traced_test]
+#[tokio::test]
+async fn test_list_role_assignments_by_role_id_same_role_multiple_scopes() -> Result<()> {
+    // Regression test for issue #513:
+    // Listing by role_id should return all assignments for that role
+    // across different targets (project_1, project_2, system).
+    let (state, _) = get_state().await?;
+
+    let domain = create_domain!(state)?;
+    let project_1 = create_project!(state, domain.id.clone())?;
+    let project_2 = create_project!(state, domain.id.clone())?;
+    let user = create_user!(state, domain.id.clone())?;
+    let role = create_role!(state)?;
+
+    // Assign the SAME role on two projects and system
+    for assignment in [
+        AssignmentCreate::user_project(&user.id, &project_1.id, &role.id, false),
+        AssignmentCreate::user_project(&user.id, &project_2.id, &role.id, false),
+        AssignmentCreate::user_system(&user.id, "all", &role.id, false),
+    ] {
+        state
+            .provider
+            .get_assignment_provider()
+            .create_grant(&state, assignment)
+            .await?;
+    }
+
+    // List assignments filtering by role_id ONLY
+    let assignments = state
+        .provider
+        .get_assignment_provider()
+        .list_role_assignments(
+            &state,
+            &RoleAssignmentListParametersBuilder::default()
+                .role_id(role.id.clone())
+                .build()?,
+        )
+        .await?;
+
+    // Filter to only our test user's assignments
+    let user_assignments: Vec<_> = assignments
+        .iter()
+        .filter(|a| a.actor_id == user.id)
+        .collect();
+
+    // Should have all 3 assignments for this user+role combination
+    assert_eq!(
+        user_assignments.len(),
+        3,
+        "Expected 3 assignments when filtering by role_id, got {}. \
+        This may indicate the HashMap bug from issue #513 is present.",
+        user_assignments.len()
+    );
+
+    // Verify the correct targets are present
+    let target_ids: BTreeSet<String> =
+        user_assignments.iter().map(|a| a.target_id.clone()).collect();
+    assert!(
+        target_ids.contains(&project_1.id),
+        "Assignment on project_1 should be present when filtering by role_id"
+    );
+    assert!(
+        target_ids.contains(&project_2.id),
+        "Assignment on project_2 should be present when filtering by role_id"
+    );
+
+    Ok(())
+}
\ No newline at end of file