diff --git a/src/backend/sync/server/routes.ts b/src/backend/sync/server/routes.ts
index 5e5177efe..5e7caff85 100644
--- a/src/backend/sync/server/routes.ts
+++ b/src/backend/sync/server/routes.ts
@@ -87,12 +87,17 @@ router.get("/v2/info", async (_req: Request, res: Response) => {
  *         description: The desktop session token and the account it belongs to.
  *       401:
  *         description: Not signed in.
+ *       403:
+ *         description: API keys cannot link a desktop.
  */
 router.post(
   "/v2/link",
   authenticateJWT,
   async (req: Request, res: Response) => {
     const userId = userOf(req);
+    if ((req as AuthenticatedRequest).apiKeyId) {
+      return res.status(403).json({ error: "API keys cannot link a desktop" });
+    }
     try {
       const user = await createCurrentUserRepository().findById(userId);
       if (!user) return res.status(401).json({ error: "User not found" });
diff --git a/src/backend/tests/utils/auth-manager-token.test.ts b/src/backend/tests/utils/auth-manager-token.test.ts
index 9b946963d..d0c2e7d1c 100644
--- a/src/backend/tests/utils/auth-manager-token.test.ts
+++ b/src/backend/tests/utils/auth-manager-token.test.ts
@@ -19,7 +19,10 @@ vi.mock("../../database/db/index.js", () => ({
 vi.mock("../../database/repositories/factory.js", () => ({
   createCurrentSettingsRepository: () => ({ get: async () => null }),
   createCurrentSessionRepository: () => ({
-    findById: async (id: string) => ({ id }),
+    findById: async (id: string) =>
+      id === "expired"
+        ? { id, expiresAt: new Date(Date.now() - 1000).toISOString() }
+        : { id },
   }),
   createCurrentUserRepository: () => ({}),
   createCurrentApiKeyRepository: () => ({}),
@@ -151,6 +154,15 @@ describe("AuthManager token handling", () => {
     expect(await authManager.verifyJWTToken(token)).toBeNull();
   });
 
+  it("rejects a token whose session has expired", async () => {
+    const token = jwt.sign(
+      { userId: "user-1", sessionId: "expired" },
+      jwtSecret,
+      { expiresIn: "1h" },
+    );
+    expect(await authManager.verifyJWTToken(token)).toBeNull();
+  });
+
   it("still accepts the sessionless pending second-factor token", async () => {
     const token = jwt.sign({ userId: "user-1", pendingTOTP: true }, jwtSecret, {
       expiresIn: "10m",
diff --git a/src/backend/tests/utils/safe-outbound-fetch.test.ts b/src/backend/tests/utils/safe-outbound-fetch.test.ts
index 131d48987..5f3f3a524 100644
--- a/src/backend/tests/utils/safe-outbound-fetch.test.ts
+++ b/src/backend/tests/utils/safe-outbound-fetch.test.ts
@@ -22,6 +22,7 @@ describe("isBlockedAddress", () => {
     expect(isBlockedAddress("192.168.1.1")).toBe(true);
     expect(isBlockedAddress("127.0.0.1")).toBe(true);
     expect(isBlockedAddress("169.254.1.1")).toBe(true);
+    expect(isBlockedAddress("192.0.0.170")).toBe(true);
     expect(isBlockedAddress("100.64.0.1")).toBe(true);
   });
 
diff --git a/src/backend/utils/auth-manager.ts b/src/backend/utils/auth-manager.ts
index 25e065c1e..5e3ade3fa 100644
--- a/src/backend/utils/auth-manager.ts
+++ b/src/backend/utils/auth-manager.ts
@@ -414,6 +414,10 @@ class AuthManager {
             return null;
           }
 
+          if (new Date(sessionRecord.expiresAt).getTime() < Date.now()) {
+            return null;
+          }
+
           await this.migrateDataKeyFromPayload(payload);
         } catch (dbError) {
           databaseLogger.error(
diff --git a/src/backend/utils/safe-outbound-fetch.ts b/src/backend/utils/safe-outbound-fetch.ts
index f328c35a7..1d657b2b4 100644
--- a/src/backend/utils/safe-outbound-fetch.ts
+++ b/src/backend/utils/safe-outbound-fetch.ts
@@ -40,6 +40,7 @@ const blockedIpv4Ranges = [
   ["127.0.0.0", 8],
   ["169.254.0.0", 16], // link-local
   ["172.16.0.0", 12],
+  ["192.0.0.0", 24], // IETF protocol assignments
   ["192.168.0.0", 16],
   ["198.18.0.0", 15], // benchmarking
   ["224.0.0.0", 4], // multicast
@@ -70,7 +71,7 @@ export function isBlockedAddress(address: string): boolean {
 }
 
 // Extracted so the blocklist decision can be tested directly against a
-// fake DNS resolver, instead of only through a real fetch()/Agent call —
+// fake DNS resolver, instead of only through a real fetch()/Agent call,
 // the actual bug here lived entirely in this callback, several layers
 // below where undici's own "fetch failed" wrapping would otherwise hide it.
 export function createDnsLookupHook(