diff --git a/apps/dashboard/public/_headers b/apps/dashboard/public/_headers
index ada78f5..184f722 100644
--- a/apps/dashboard/public/_headers
+++ b/apps/dashboard/public/_headers
@@ -1,4 +1,5 @@
 /*
+  Strict-Transport-Security: max-age=63072000; includeSubDomains
   X-Content-Type-Options: nosniff
   Referrer-Policy: strict-origin-when-cross-origin
   Permissions-Policy: camera=(), microphone=(), geolocation=(), payment=()
diff --git a/apps/dashboard/worker/index.ts b/apps/dashboard/worker/index.ts
index 86c3af9..5309fbc 100644
--- a/apps/dashboard/worker/index.ts
+++ b/apps/dashboard/worker/index.ts
@@ -14,6 +14,7 @@ export { LiveRoom };
 
 const MAX_BODY_BYTES = 512 * 1024;
 const MAX_FUTURE_RECORD_SKEW_MS = 60_000;
+const STRICT_TRANSPORT_SECURITY = "max-age=63072000; includeSubDomains";
 const JSON_HEADERS = {
   "content-type": "application/json; charset=utf-8",
   "cache-control": "no-store",
@@ -22,14 +23,35 @@ const JSON_HEADERS = {
 };
 
 export default {
-  fetch(request: Request, env: Env, ctx: ExecutionContextLike): Promise<Response> {
-    return handleRequest(request, env, ctx);
+  async fetch(request: Request, env: Env, ctx: ExecutionContextLike): Promise<Response> {
+    const url = new URL(request.url);
+    if (url.protocol !== "https:") {
+      url.protocol = "https:";
+      return new Response(null, {
+        status: 308,
+        headers: { location: url.toString(), "cache-control": "no-store" }
+      });
+    }
+    return withStrictTransportSecurity(await handleRequest(request, env, ctx));
   },
   scheduled(controller: ScheduledControllerLike, env: Env, ctx: ExecutionContextLike): void {
     ctx.waitUntil(runScheduled(controller, env));
   }
 };
 
+function withStrictTransportSecurity(response: Response): Response {
+  const headers = new Headers(response.headers);
+  headers.set("strict-transport-security", STRICT_TRANSPORT_SECURITY);
+  if (response.status === 101 && response.webSocket) {
+    return new Response(null, { status: 101, headers, webSocket: response.webSocket });
+  }
+  return new Response(response.body, {
+    status: response.status,
+    statusText: response.statusText,
+    headers
+  });
+}
+
 export async function handleRequest(request: Request, env: Env, _ctx?: ExecutionContextLike): Promise<Response> {
   const url = new URL(request.url);
   if (!url.pathname.startsWith("/api/")) return new Response("Not found", { status: 404 });
diff --git a/apps/dashboard/worker/index.worker.test.ts b/apps/dashboard/worker/index.worker.test.ts
index d5f94ff..0f04556 100644
--- a/apps/dashboard/worker/index.worker.test.ts
+++ b/apps/dashboard/worker/index.worker.test.ts
@@ -121,6 +121,20 @@ async function expectQuiet(socket: WebSocket, durationMs = 400): Promise<void> {
 }
 
 describe("Worker API", () => {
+  it("redirects insecure API requests before handling and emits HSTS over HTTPS", async () => {
+    const insecure = await SELF.fetch("http://snapmeter.test/api/v1/metadata?probe=transport", {
+      redirect: "manual"
+    });
+    expect(insecure.status).toBe(308);
+    expect(insecure.headers.get("location")).toBe("https://snapmeter.test/api/v1/metadata?probe=transport");
+    expect(insecure.headers.get("cache-control")).toBe("no-store");
+    expect(insecure.headers.get("strict-transport-security")).toBeNull();
+
+    const secure = await SELF.fetch("https://snapmeter.test/api/v1/metadata");
+    expect(secure.status).toBe(200);
+    expect(secure.headers.get("strict-transport-security")).toBe("max-age=63072000; includeSubDomains");
+  });
+
   it("reports pinned source metadata and disconnected status honestly", async () => {
     const metadata = await SELF.fetch("https://snapmeter.test/api/v1/metadata");
     expect(metadata.status).toBe(200);
@@ -139,6 +153,16 @@ describe("Worker API", () => {
     expect(response.status).toBe(403);
   });
 
+  it("emits HSTS on successful WebSocket upgrades", async () => {
+    const response = await SELF.fetch("https://snapmeter.test/api/v1/live", {
+      headers: { Upgrade: "websocket" }
+    });
+    expect(response.status).toBe(101);
+    expect(response.headers.get("strict-transport-security")).toBe("max-age=63072000; includeSubDomains");
+    response.webSocket?.accept();
+    response.webSocket?.close(1000, "done");
+  });
+
   it("authenticates an empty doctor probe without storing it", async () => {
     const payload = batch();
     const response = await SELF.fetch(await signedRequest(payload, { "x-snapmeter-doctor": "1" }));