diff --git a/api/src/routes/dot-lookup.ts b/api/src/routes/dot-lookup.ts
index a55dda1..7078ad4 100644
--- a/api/src/routes/dot-lookup.ts
+++ b/api/src/routes/dot-lookup.ts
@@ -20,15 +20,19 @@ const FMCSA_BASE = "https://mobile.fmcsa.dot.gov/qc/services/carriers";
 
 async function fmcsaFetch(path: string): Promise<any> {
   if (!FMCSA_API_KEY) return null;
+  const controller = new AbortController();
+  const timer = setTimeout(() => controller.abort(), 5000);
   try {
     const url = `${FMCSA_BASE}/${path}${path.includes("?") ? "&" : "?"}webKey=${FMCSA_API_KEY}`;
     const resp = await fetch(url, {
-      signal: AbortSignal.timeout(5000),
+      signal: controller.signal,
       headers: { "Accept": "application/json" },
     });
+    clearTimeout(timer);
     if (!resp.ok) return null;
     return await resp.json();
   } catch {
+    clearTimeout(timer);
     return null;
   }
 }
@@ -515,7 +519,7 @@ router.get("/api/v1/dot/lookup", async (req, res) => {
             method: "POST",
             headers: { "Content-Type": "application/json" },
             body: JSON.stringify({ entity_name: name, state_code: state }),
-            signal: AbortSignal.timeout(5000),
+            signal: (() => { const c = new AbortController(); setTimeout(() => c.abort(), 5000); return c.signal; })(),
           });
           if (sosResp.ok) {
             sosStatus = (await sosResp.json()) as { found?: boolean; status?: string; error?: string };
@@ -593,6 +597,7 @@ router.get("/api/v1/dot/lookup", async (req, res) => {
     const redCount = checks.filter(c => c.status === "red").length;
     const yellowCount = checks.filter(c => c.status === "yellow").length;
 
+    if (res.headersSent) return; // deadline already responded
     res.json({
       dot_number: rawDot,
       legal_name: name,
@@ -722,7 +727,7 @@ router.post("/api/v1/dot/name-check", async (req, res) => {
             method: "POST",
             headers: { "Content-Type": "application/json" },
             body: JSON.stringify({ entity_name: name, state_code: stateCode }),
-            signal: AbortSignal.timeout(5000),
+            signal: (() => { const c = new AbortController(); setTimeout(() => c.abort(), 5000); return c.signal; })(),
           }).then(r => r.json())
         : Promise.resolve({ skipped: true }),