diff --git a/src/app/api/system/version/route.ts b/src/app/api/system/version/route.ts
index 6032f70159..6e2f1e2f36 100644
--- a/src/app/api/system/version/route.ts
+++ b/src/app/api/system/version/route.ts
@@ -5,6 +5,7 @@
  * Security: Requires admin authentication (same as other management routes).
  * Safety: Update only runs if a newer version is available on npm.
  */
+import { createHash } from "node:crypto";
 import { NextRequest, NextResponse } from "next/server";
 import { execFile } from "child_process";
 import { promisify } from "util";
@@ -17,7 +18,11 @@ import {
   PROJECT_ROOT,
 } from "@/lib/system/autoUpdate";
 import { NEWS_JSON_URL, parseActiveNewsPayload } from "@/shared/utils/releaseNotes";
-import { isNewer, resolveLatestVersion } from "@/lib/system/versionCheck";
+import {
+  clearLatestVersionCache,
+  isNewer,
+  resolveLatestVersionCached,
+} from "@/lib/system/versionCheck";
 import { resolveGlobalOmniroutePath } from "@/lib/system/globalPackagePath";
 // #5542 — On Windows npm is `npm.cmd`; Node ≥24 refuses to execFile a `.cmd` without
 // a shell (nodejs/node#52554 → "spawn npm ENOENT"). buildNpmExecOptions enables the
@@ -56,21 +61,34 @@ export async function GET(req: NextRequest) {
   const config = getAutoUpdateConfig();
 
   const [latest, news, validation] = await Promise.all([
-    resolveLatestVersion(),
+    resolveLatestVersionCached({
+      bypassCache: /(?:^|,)\s*(?:no-cache|no-store)\b/i.test(
+        req.headers.get("Cache-Control") ?? ""
+      ),
+      storeResult: !/(?:^|,)\s*no-store\b/i.test(req.headers.get("Cache-Control") ?? ""),
+    }),
     getNews(),
     validateAutoUpdateRuntime(config),
   ]);
 
-  const updateAvailable = isNewer(latest, current);
-
-  return NextResponse.json({
+  const body = {
     current,
     latest: latest ?? "unavailable",
-    updateAvailable,
+    updateAvailable: isNewer(latest, current),
     channel: config.mode,
     autoUpdateSupported: validation.supported,
     autoUpdateError: validation.reason,
     news,
+  };
+  const serialized = JSON.stringify(body);
+  const etag = `"${createHash("sha256").update(serialized).digest("base64url")}"`;
+  const headers = { "Cache-Control": "private, no-cache, must-revalidate", ETag: etag };
+  const validators = req.headers.get("If-None-Match")?.split(",").map((value) => value.trim());
+  if (validators?.some((value) => value === etag || value === `W/${etag}`)) {
+    return new NextResponse(null, { status: 304, headers });
+  }
+  return new NextResponse(serialized, {
+    headers: { ...headers, "Content-Type": "application/json" },
   });
 }
 
@@ -80,7 +98,7 @@ export async function POST(req: NextRequest) {
   }
 
   const current = getCurrentVersion();
-  const latest = await resolveLatestVersion();
+  const latest = await resolveLatestVersionCached({ bypassCache: true });
 
   if (!latest) {
     return NextResponse.json(
@@ -128,6 +146,7 @@ export async function POST(req: NextRequest) {
       );
     }
 
+    clearLatestVersionCache();
     return NextResponse.json({
       success: true,
       message: `Update to v${latest} started. Docker rebuild is running in the background.`,
@@ -339,6 +358,7 @@ export async function POST(req: NextRequest) {
             });
           }
 
+        clearLatestVersionCache();
         send({
           step: "complete",
           status: "done",
diff --git a/src/lib/system/versionCheck.ts b/src/lib/system/versionCheck.ts
index a89eddb53a..3e0dfd83d9 100644
--- a/src/lib/system/versionCheck.ts
+++ b/src/lib/system/versionCheck.ts
@@ -36,6 +36,16 @@ const GITHUB_RELEASES_LATEST_URL =
   "https://api.github.com/repos/diegosouzapw/OmniRoute/releases/latest";
 
 const LOOKUP_TIMEOUT_MS = 10_000;
+const MAX_VERSION_RESPONSE_BYTES = 16 * 1024;
+const LATEST_VERSION_CACHE_TTL_MS = 10 * 60_000;
+const MAX_LATEST_VERSION_CACHE_TTL_MS = 10 * 60_000;
+
+type LatestVersionCacheEntry = { value: string; expiresAt: number };
+
+let latestVersionCache: LatestVersionCacheEntry | null = null;
+let latestVersionLookup: Promise<string | null> | null = null;
+let latestVersionRefresh: Promise<string | null> | null = null;
+let latestVersionCacheGeneration = 0;
 
 // The pure semver helpers live in `./versionCompare` (dependency-free) so
 // client-reachable modules can import them without pulling this file's
@@ -64,6 +74,40 @@ export async function getLatestVersionFromNpmCli(): Promise<string | null> {
  * Latest published version via the npm registry HTTP API. Needs only network access — no
  * `npm` binary — so it works in Docker / desktop / locked-down installs.
  */
+async function readBoundedJson(response: Response): Promise<unknown> {
+  const declaredLength = Number(response.headers.get("Content-Length"));
+  if (Number.isFinite(declaredLength) && declaredLength > MAX_VERSION_RESPONSE_BYTES) {
+    await response.body?.cancel();
+    throw new Error("Version metadata response is too large");
+  }
+
+  if (!response.body) return response.json();
+  const reader = response.body.getReader();
+  const chunks: Uint8Array[] = [];
+  let totalBytes = 0;
+  try {
+    while (true) {
+      const { done, value } = await reader.read();
+      if (done) break;
+      totalBytes += value.byteLength;
+      if (totalBytes > MAX_VERSION_RESPONSE_BYTES) {
+        await reader.cancel();
+        throw new Error("Version metadata response is too large");
+      }
+      chunks.push(value);
+    }
+  } finally {
+    reader.releaseLock();
+  }
+  const body = new Uint8Array(totalBytes);
+  let offset = 0;
+  for (const chunk of chunks) {
+    body.set(chunk, offset);
+    offset += chunk.byteLength;
+  }
+  return JSON.parse(new TextDecoder().decode(body));
+}
+
 export async function getLatestVersionFromRegistry(
   fetchImpl: typeof fetch = fetch
 ): Promise<string | null> {
@@ -72,7 +116,7 @@ export async function getLatestVersionFromRegistry(
       signal: AbortSignal.timeout(LOOKUP_TIMEOUT_MS),
     });
     if (!res.ok) return null;
-    const data = (await res.json()) as { version?: unknown };
+    const data = (await readBoundedJson(res)) as { version?: unknown };
     return typeof data?.version === "string" && data.version ? data.version : null;
   } catch {
     return null;
@@ -99,7 +143,7 @@ export async function getLatestVersionFromGitHub(
       },
     });
     if (!res.ok) return null;
-    const data = (await res.json()) as { tag_name?: unknown };
+    const data = (await readBoundedJson(res)) as { tag_name?: unknown };
     return typeof data?.tag_name === "string" && data.tag_name ? data.tag_name : null;
   } catch {
     return null;
@@ -112,6 +156,51 @@ export async function getLatestVersionFromGitHub(
  * warning — instead of silently degrading to "no update available" — when ALL sources fail.
  * Thunks are injectable for tests.
  */
+export function clearLatestVersionCache(): void {
+  latestVersionCache = null;
+  latestVersionCacheGeneration += 1;
+}
+
+/** Coalesce and briefly cache successful latest-version lookups. */
+export async function resolveLatestVersionCached(opts?: {
+  lookup?: () => Promise<string | null>;
+  bypassCache?: boolean;
+  storeResult?: boolean;
+  now?: () => number;
+  ttlMs?: number;
+}): Promise<string | null> {
+  const now = opts?.now ?? Date.now;
+  if (!opts?.bypassCache && latestVersionCache?.expiresAt > now()) {
+    return latestVersionCache.value;
+  }
+
+  const inFlight = opts?.bypassCache ? latestVersionRefresh : latestVersionLookup;
+  if (inFlight) return inFlight;
+  if (opts?.bypassCache) clearLatestVersionCache();
+
+  const generation = latestVersionCacheGeneration;
+  const lookup = opts?.lookup ?? resolveLatestVersion;
+  const ttlMs = Math.min(
+    Math.max(opts?.ttlMs ?? LATEST_VERSION_CACHE_TTL_MS, 0),
+    MAX_LATEST_VERSION_CACHE_TTL_MS
+  );
+  const pending = lookup().then((value) => {
+    if (value && opts?.storeResult !== false && latestVersionCacheGeneration === generation) {
+      latestVersionCache = { value, expiresAt: now() + ttlMs };
+    }
+    return value;
+  });
+  if (opts?.bypassCache) latestVersionRefresh = pending;
+  else latestVersionLookup = pending;
+
+  try {
+    return await pending;
+  } finally {
+    if (latestVersionLookup === pending) latestVersionLookup = null;
+    if (latestVersionRefresh === pending) latestVersionRefresh = null;
+  }
+}
+
 export async function resolveLatestVersion(opts?: {
   npmCli?: () => Promise<string | null>;
   registry?: () => Promise<string | null>;
diff --git a/tests/unit/system-version-cache-8278.test.ts b/tests/unit/system-version-cache-8278.test.ts
new file mode 100644
index 0000000000..72a79e5900
--- /dev/null
+++ b/tests/unit/system-version-cache-8278.test.ts
@@ -0,0 +1,114 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import {
+  clearLatestVersionCache,
+  resolveLatestVersionCached,
+} from "@/lib/system/versionCheck";
+
+function deferred<T>() {
+  let resolve!: (value: T) => void;
+  let reject!: (reason?: unknown) => void;
+  const promise = new Promise<T>((resolvePromise, rejectPromise) => {
+    resolve = resolvePromise;
+    reject = rejectPromise;
+  });
+  return { promise, resolve, reject };
+}
+
+test.beforeEach(() => clearLatestVersionCache());
+
+test("coalesces concurrent latest-version resolution into one lookup", async () => {
+  let calls = 0;
+  const pending = deferred<string | null>();
+  const lookup = () => {
+    calls += 1;
+    return pending.promise;
+  };
+
+  const requests = Array.from({ length: 10 }, () => resolveLatestVersionCached({ lookup }));
+  assert.equal(calls, 1);
+  pending.resolve("3.8.50");
+  assert.deepEqual(await Promise.all(requests), Array(10).fill("3.8.50"));
+});
+
+test("reuses a successful result only inside the bounded TTL", async () => {
+  let now = 1_000;
+  let calls = 0;
+  const lookup = async () => `3.8.${++calls + 49}`;
+
+  assert.equal(await resolveLatestVersionCached({ lookup, now: () => now, ttlMs: 500 }), "3.8.50");
+  now = 1_499;
+  assert.equal(await resolveLatestVersionCached({ lookup, now: () => now, ttlMs: 500 }), "3.8.50");
+  now = 1_500;
+  assert.equal(await resolveLatestVersionCached({ lookup, now: () => now, ttlMs: 500 }), "3.8.51");
+  assert.equal(calls, 2);
+});
+
+test("explicit refresh bypasses an ordinary in-flight lookup and coalesces with refreshes", async () => {
+  let calls = 0;
+  const ordinary = deferred<string | null>();
+  const refresh = deferred<string | null>();
+  const lookup = () => {
+    calls += 1;
+    return calls === 1 ? ordinary.promise : refresh.promise;
+  };
+
+  const stale = resolveLatestVersionCached({ lookup });
+  const firstRefresh = resolveLatestVersionCached({ lookup, bypassCache: true });
+  const secondRefresh = resolveLatestVersionCached({ lookup, bypassCache: true });
+  assert.equal(calls, 2);
+
+  ordinary.resolve("3.8.49");
+  refresh.resolve("3.8.50");
+  assert.equal(await stale, "3.8.49");
+  assert.deepEqual(await Promise.all([firstRefresh, secondRefresh]), ["3.8.50", "3.8.50"]);
+  assert.equal(await resolveLatestVersionCached({ lookup }), "3.8.50");
+  assert.equal(calls, 2);
+});
+
+test("no-store refresh does not populate the process cache", async () => {
+  let calls = 0;
+  const lookup = async () => `3.8.${++calls + 49}`;
+
+  assert.equal(
+    await resolveLatestVersionCached({ lookup, bypassCache: true, storeResult: false }),
+    "3.8.50"
+  );
+  assert.equal(await resolveLatestVersionCached({ lookup }), "3.8.51");
+  assert.equal(calls, 2);
+});
+
+test("cache invalidation prevents an older in-flight result from repopulating the cache", async () => {
+  let calls = 0;
+  const pending = deferred<string | null>();
+  const first = resolveLatestVersionCached({
+    lookup: () => {
+      calls += 1;
+      return pending.promise;
+    },
+  });
+
+  clearLatestVersionCache();
+  pending.resolve("3.8.50");
+  assert.equal(await first, "3.8.50");
+  assert.equal(
+    await resolveLatestVersionCached({ lookup: async () => `3.8.${++calls + 49}` }),
+    "3.8.51"
+  );
+});
+
+test("failed and unavailable lookups are not cached and leave no stale singleflight", async () => {
+  let calls = 0;
+  const lookup = async () => {
+    calls += 1;
+    if (calls === 1) throw new Error("lookup failed");
+    if (calls === 2) return null;
+    return "3.8.50";
+  };
+
+  await assert.rejects(resolveLatestVersionCached({ lookup }), /lookup failed/);
+  assert.equal(await resolveLatestVersionCached({ lookup }), null);
+  assert.equal(await resolveLatestVersionCached({ lookup }), "3.8.50");
+  assert.equal(await resolveLatestVersionCached({ lookup }), "3.8.50");
+  assert.equal(calls, 3);
+});
diff --git a/tests/unit/system-version-check-4100.test.ts b/tests/unit/system-version-check-4100.test.ts
index b903302180..9f25b2806a 100644
--- a/tests/unit/system-version-check-4100.test.ts
+++ b/tests/unit/system-version-check-4100.test.ts
@@ -17,6 +17,7 @@ import {
   isNewer,
   resolveLatestVersion,
   getLatestVersionFromGitHub,
+  getLatestVersionFromRegistry,
 } from "@/lib/system/versionCheck";
 
 test("normalizeVersion strips v-prefix, pre-release/build, returns numeric tuple", () => {
@@ -120,3 +121,37 @@ test("getLatestVersionFromGitHub returns null on a non-OK response", async () =>
     new Response("rate limited", { status: 403 })) as unknown as typeof fetch;
   assert.equal(await getLatestVersionFromGitHub(fakeFetch), null);
 });
+
+test("HTTP version sources reject oversized bodies without parsing them", async () => {
+  let registryCancelled = false;
+  let githubCancelled = false;
+  const oversizedResponse = (onCancel: () => void) =>
+    new Response(
+      new ReadableStream({
+        start(controller) {
+          controller.enqueue(new Uint8Array(32 * 1024));
+        },
+        cancel() {
+          onCancel();
+        },
+      }),
+      { status: 200 }
+    );
+
+  assert.equal(
+    await getLatestVersionFromRegistry((async () =>
+      oversizedResponse(() => {
+        registryCancelled = true;
+      })) as unknown as typeof fetch),
+    null
+  );
+  assert.equal(
+    await getLatestVersionFromGitHub((async () =>
+      oversizedResponse(() => {
+        githubCancelled = true;
+      })) as unknown as typeof fetch),
+    null
+  );
+  assert.equal(registryCancelled, true);
+  assert.equal(githubCancelled, true);
+});