diff --git a/source/core/self-update-check.ts b/source/core/self-update-check.ts
index 1440fd9..bfd503a 100644
--- a/source/core/self-update-check.ts
+++ b/source/core/self-update-check.ts
@@ -76,6 +76,8 @@ export interface SelfUpdateResult {
 export const CACHE_FILENAME = 'self-update.json';
 export const TTL_MS = 24 * 60 * 60 * 1000;
 export const FETCH_TIMEOUT_MS = 3000;
+/** Node's `setTimeout` delay ceiling (2^31−1 ms); larger values overflow to ~1ms. */
+const TIMER_MAX_MS = 2_147_483_647;
 export const NPM_REGISTRY_URL = 'https://registry.npmjs.org/shardmind/latest';
 const CACHE_SCHEMA_VERSION = 1 as const;
 const SHARDMIND_DIRNAME = 'shardmind';
@@ -130,6 +132,29 @@ export function getSelfUpdateCacheDir(): string {
   return path.join(os.homedir(), '.cache', SHARDMIND_DIRNAME);
 }
 
+/**
+ * Resolve the fetch timeout at call time. Production default is
+ * `FETCH_TIMEOUT_MS` (3s) — short, because a courtesy notifier must never make
+ * a real command feel slow. It can be raised via
+ * `SHARDMIND_SELF_UPDATE_FETCH_TIMEOUT_MS` for two cases: a user on a genuinely
+ * slow link, and Layer-1 flow tests where heavy parallel CPU load can starve
+ * the event loop past 3s before the (fast, local) stub response is processed —
+ * which would spuriously abort the fetch and the banner would never render.
+ * Mirrors the call-time env reads in `getRegistryUrl` / `getSelfUpdateCacheDir`.
+ * A non-numeric or non-positive value falls back to the default (never disables
+ * the timeout).
+ */
+export function getConfiguredFetchTimeoutMs(): number {
+  const raw = process.env['SHARDMIND_SELF_UPDATE_FETCH_TIMEOUT_MS'];
+  if (raw === undefined) return FETCH_TIMEOUT_MS;
+  const n = Number(raw.trim());
+  if (!Number.isFinite(n) || n <= 0) return FETCH_TIMEOUT_MS;
+  // Node's setTimeout delay is a 32-bit signed int; a value above that overflows
+  // to ~1ms (the OPPOSITE of a longer timeout — it would abort the fetch almost
+  // immediately). Truncate fractions and clamp to the timer ceiling.
+  return Math.min(Math.trunc(n), TIMER_MAX_MS);
+}
+
 function cachePath(cacheDir: string): string {
   return path.join(cacheDir, CACHE_FILENAME);
 }
@@ -253,7 +278,7 @@ export async function checkSelfUpdate(
     currentVersion,
     cacheDir = getSelfUpdateCacheDir(),
     ttlMs = TTL_MS,
-    fetchTimeoutMs = FETCH_TIMEOUT_MS,
+    fetchTimeoutMs = getConfiguredFetchTimeoutMs(),
     now = Date.now(),
     signal,
   } = opts;
diff --git a/tests/component/flows/self-update-flow.test.tsx b/tests/component/flows/self-update-flow.test.tsx
index e189cb7..512df86 100644
--- a/tests/component/flows/self-update-flow.test.tsx
+++ b/tests/component/flows/self-update-flow.test.tsx
@@ -121,6 +121,7 @@ describe('self-update notifier — Layer 1 flow tests (#113)', () => {
     'SHARDMIND_SELF_UPDATE_FORCE_TTY',
     'SHARDMIND_SELF_UPDATE_REGISTRY_URL',
     'SHARDMIND_SELF_UPDATE_CACHE_DIR',
+    'SHARDMIND_SELF_UPDATE_FETCH_TIMEOUT_MS',
     'CI',
   ] as const;
   let envSnapshot: Partial<Record<(typeof TOUCHED_ENV)[number], string | undefined>>;
@@ -165,6 +166,13 @@ describe('self-update notifier — Layer 1 flow tests (#113)', () => {
     delete process.env['CI'];
     process.env['SHARDMIND_SELF_UPDATE_FORCE_TTY'] = '1';
     process.env['SHARDMIND_SELF_UPDATE_REGISTRY_URL'] = npmStub.url;
+    // The local stub answers in single-digit ms, but under heavy parallel CPU
+    // load the event loop can starve past the production 3s fetch timeout
+    // before the response is processed — aborting the fetch so the banner
+    // never renders and the banner-wait below times out. Give the fetch a wide
+    // budget here (above the 30s banner waitFor below, under the 60s test
+    // timeout); production keeps the 3s default. (Fixes the flaky scenario 7.)
+    process.env['SHARDMIND_SELF_UPDATE_FETCH_TIMEOUT_MS'] = '45000';
     // Per-test cache dir keeps the dev's real ~/.cache/shardmind clean
     // and avoids one test's cache hit suppressing the next test's fetch.
     const cacheDir = path.join(cacheDirParent, crypto.randomUUID());
@@ -293,7 +301,7 @@ describe('self-update notifier — Layer 1 flow tests (#113)', () => {
           f.includes(`shardmind ${NEWER_VERSION}`) &&
           f.includes('npm install -g shardmind@latest') &&
           /shardmind\/minimal/.test(f),
-        15_000,
+        30_000,
       );
       // Banner is above the status header (StatusView's first line is
       // the namespace/name + version badge). String-position check
@@ -402,7 +410,7 @@ describe('self-update notifier — Layer 1 flow tests (#113)', () => {
       await waitFor(
         r.lastFrame,
         (f) => f.includes(`shardmind ${NEWER_VERSION}`),
-        15_000,
+        30_000,
       );
     } finally {
       if (vault) await vault.cleanup();
diff --git a/tests/unit/self-update-check.test.ts b/tests/unit/self-update-check.test.ts
index e9ea74a..a61f893 100644
--- a/tests/unit/self-update-check.test.ts
+++ b/tests/unit/self-update-check.test.ts
@@ -24,8 +24,10 @@ import crypto from 'node:crypto';
 import {
   checkSelfUpdate,
   getSelfUpdateCacheDir,
+  getConfiguredFetchTimeoutMs,
   CACHE_FILENAME,
   TTL_MS,
+  FETCH_TIMEOUT_MS,
 } from '../../source/core/self-update-check.js';
 
 function npmLatestResponse(version: string): Response {
@@ -614,4 +616,43 @@ describe('self-update-check', () => {
       expect(result).toEqual({ outdated: true, latest: '1.0.0' });
     });
   });
+
+  describe('getConfiguredFetchTimeoutMs — SHARDMIND_SELF_UPDATE_FETCH_TIMEOUT_MS', () => {
+    const KEY = 'SHARDMIND_SELF_UPDATE_FETCH_TIMEOUT_MS';
+    let original: string | undefined;
+    beforeEach(() => {
+      original = process.env[KEY];
+    });
+    afterEach(() => {
+      if (original === undefined) delete process.env[KEY];
+      else process.env[KEY] = original;
+    });
+
+    it('defaults to FETCH_TIMEOUT_MS when unset', () => {
+      delete process.env[KEY];
+      expect(getConfiguredFetchTimeoutMs()).toBe(FETCH_TIMEOUT_MS);
+    });
+
+    it('honors a positive numeric override (trimmed)', () => {
+      process.env[KEY] = '  45000 ';
+      expect(getConfiguredFetchTimeoutMs()).toBe(45000);
+    });
+
+    it('falls back to the default on non-numeric / non-positive / empty input', () => {
+      for (const bad of ['', '   ', 'abc', '0', '-5', 'NaN', 'Infinity']) {
+        process.env[KEY] = bad;
+        expect(getConfiguredFetchTimeoutMs()).toBe(FETCH_TIMEOUT_MS);
+      }
+    });
+
+    it('truncates fractions and clamps to the 32-bit setTimeout ceiling', () => {
+      // Fractional → truncated (setTimeout would truncate anyway).
+      process.env[KEY] = '45000.9';
+      expect(getConfiguredFetchTimeoutMs()).toBe(45000);
+      // Above 2^31−1 would overflow setTimeout to ~1ms; clamp to the ceiling
+      // so a fat-fingered huge value never makes the timeout *shorter*.
+      process.env[KEY] = '9999999999';
+      expect(getConfiguredFetchTimeoutMs()).toBe(2_147_483_647);
+    });
+  });
 });