fix(auth): restore permission boundary safeguards

backend/test/routes-sessions.test.ts

@@ -10,6 +10,8 @@ import { SseHub } from "../src/sse/sse-hub.js";
 import { MaintenanceBarrier } from "../src/runtime/maintenance-gate.js";
 import { PiProcessManager } from "../src/pi/pi-process-manager.js";
 import { validateDeclarativePiConfig } from "../src/pi/managed-config.js";
+import Fastify from "fastify";
+import { sessionRoutes } from "../src/routes/sessions.js";
 
 const FAKE = path.resolve("../harness/tests/fake_pi/fake_pi_rpc.mjs");
 const SCRIPT = path.resolve("../harness/tests/fake_pi/scripts/f1_disambiguation.json");
@@ -99,6 +101,29 @@ test("upstream requests without a principal fail before a Pi runtime can be crea
   expect(created).toBe(false);
 });
 
+test("GET /sessions with a query still requires session.use", async () => {
+  const app = Fastify();
+  app.addHook("preHandler", async (request) => {
+    request.principal = { issuer: "oidc", subject: "no-role", roles: [], permissions: [], isAdmin: false };
+  });
+  sessionRoutes(app, {
+    mgr: { get: () => undefined } as any,
+    tht: { sessionList: async () => [] } as any,
+    hub: {} as any,
+    getSettings: async () => ({}),
+    readiness: {} as any,
+    listModels: async () => [],
+    workspaceRegistry: { list: async () => [] } as any,
+    workspaceRuntimeSupport: () => true,
+    maintenanceBarrier: new MaintenanceBarrier(),
+  });
+
+  const response = await app.inject({ method: "GET", url: "/sessions?scope=mine" });
+
+  expect(response.statusCode).toBe(403);
+  expect(response.json()).toEqual({ code: "auth_forbidden", error: "This operation is not permitted" });
+});
+
 test("maintenance rejects new and resumed session admission without interrupting running sessions", async () => {
   const maintenanceBarrier = new MaintenanceBarrier();
   await maintenanceBarrier.activate();