diff --git a/apps/desktop/src/main/config.test.ts b/apps/desktop/src/main/config.test.ts
index bd7d1b86929..b7bba066697 100644
--- a/apps/desktop/src/main/config.test.ts
+++ b/apps/desktop/src/main/config.test.ts
@@ -3,6 +3,7 @@ import { tmpdir } from 'node:os'
 import { dirname, join } from 'node:path'
 import { describe, expect, it } from 'vitest'
 import {
+  addressSpaceOverrideForOrigin,
   canonicalOrigin,
   createConfigStore,
   DEFAULT_ORIGIN,
@@ -42,6 +43,17 @@ describe('partitionForOrigin', () => {
   })
 })
 
+describe('addressSpaceOverrideForOrigin', () => {
+  it('marks only self-hosted deployment hosts as public', () => {
+    expect(addressSpaceOverrideForOrigin('https://sim.internal.example')).toBe(
+      'sim.internal.example=public'
+    )
+    expect(addressSpaceOverrideForOrigin('https://192.168.50.173')).toBe('192.168.50.173=public')
+    expect(addressSpaceOverrideForOrigin('https://www.sim.ai')).toBeNull()
+    expect(addressSpaceOverrideForOrigin('http://localhost:3000')).toBeNull()
+  })
+})
+
 describe('canonicalOrigin', () => {
   it('keeps a rewritten install on its existing cookie partition', () => {
     // The whole point of rewriting rather than leaving the apex in place: the
diff --git a/apps/desktop/src/main/config.ts b/apps/desktop/src/main/config.ts
index 28ca953f16f..f4ebf2eeed9 100644
--- a/apps/desktop/src/main/config.ts
+++ b/apps/desktop/src/main/config.ts
@@ -203,6 +203,24 @@ export function isSimCloudOrigin(origin: string): boolean {
   }
 }
 
+/**
+ * Chromium's Local Network Access checks reject a top-level navigation when a
+ * self-hosted deployment name resolves to RFC1918 space, before Electron can
+ * show a permission prompt or the request reaches the server. The configured
+ * Sim origin is an explicit trust decision and already owns the shell's preload
+ * bridge, so classify only that hostname as public instead of disabling the
+ * process-wide checks that protect arbitrary browser tabs.
+ */
+export function addressSpaceOverrideForOrigin(origin: string): string | null {
+  try {
+    const host = new URL(origin).hostname.toLowerCase()
+    if (isLoopbackHostname(host) || isSimCloudOrigin(origin)) return null
+    return `${host}=public`
+  } catch {
+    return null
+  }
+}
+
 /**
  * Maps a server origin to its cookie/storage partition. Each origin gets an
  * isolated persistent partition so sessions never leak across instances.
diff --git a/apps/desktop/src/main/index.ts b/apps/desktop/src/main/index.ts
index a0efc04faf5..34f22869713 100644
--- a/apps/desktop/src/main/index.ts
+++ b/apps/desktop/src/main/index.ts
@@ -61,6 +61,7 @@ import { NativeComputerUseClient } from '@/main/computer-use/native-client'
 import { ComputerUseService } from '@/main/computer-use/service'
 import {
   APP_NAME_FOR_CHANNEL,
+  addressSpaceOverrideForOrigin,
   channelForOrigin,
   createConfigStore,
   DEFAULT_ORIGIN,
@@ -156,6 +157,10 @@ function main(): void {
       logger.error('Could not repair desktop settings for account-data recovery')
     }
   }
+  const addressSpaceOverride = addressSpaceOverrideForOrigin(config.getOrigin())
+  if (addressSpaceOverride) {
+    app.commandLine.appendSwitch('ip-address-space-overrides', addressSpaceOverride)
+  }
   const accountDataAvailable = () =>
     config.isPersistenceAvailable() && !isAccountDataTeardownRequired()
   const events = createEventLog(join(userDataPath, 'logs'))