diff --git a/.jules/sentinel.md b/.jules/sentinel.md
new file mode 100644
index 0000000..79618ac
--- /dev/null
+++ b/.jules/sentinel.md
@@ -0,0 +1,3 @@
+# Sentinel Security Journal
+
+## 2026-09-13 - AI Endpoint Transport Security Validation **Vulnerability:** Remote AI service endpoints permitted unencrypted HTTP, risking plaintext transmission of user credentials and sensitive AI prompt data over untrusted networks. **Learning:** User-configurable endpoints often mix remote API services with local development servers (e.g., Ollama), requiring explicit differentiation between loopback hosts and remote endpoints. **Prevention:** Enforce HTTPS scheme validation for remote endpoints while allowing HTTP strictly for local loopback hosts (`localhost`, `127.0.0.1`, `::1`).
diff --git a/lib/providers/settings_provider.dart b/lib/providers/settings_provider.dart
index a005a2f..9208d22 100644
--- a/lib/providers/settings_provider.dart
+++ b/lib/providers/settings_provider.dart
@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:janus/models/app_settings.dart';
+import 'package:janus/services/ai_endpoint_validator.dart';
 import 'package:janus/services/settings_service.dart';
 import 'package:riverpod_annotation/riverpod_annotation.dart';
 
@@ -192,6 +193,17 @@ class AppSettingsNotifier extends _$AppSettingsNotifier {
   }
 
   // AI settings
+  Future<bool> setEndPoint(String endPoint) async {
+    final trimmed = endPoint.trim();
+    if (trimmed.isNotEmpty && !AiEndpointValidator.isValidEndpoint(trimmed)) {
+      return false;
+    }
+    await _persist(
+      (state.value ?? const AppSettings()).copyWith(endPoint: trimmed),
+    );
+    return true;
+  }
+
   Future<void> setUseAiDailySummary(bool enabled) async {
     await _persist(
       (state.value ?? const AppSettings()).copyWith(aiDailySummary: enabled),
diff --git a/lib/services/ai_endpoint_validator.dart b/lib/services/ai_endpoint_validator.dart
new file mode 100644
index 0000000..2a9fe89
--- /dev/null
+++ b/lib/services/ai_endpoint_validator.dart
@@ -0,0 +1,26 @@
+/// Utility for validating AI service API endpoints for secure transport.
+class AiEndpointValidator {
+  AiEndpointValidator._();
+
+  /// Validates whether [url] is a secure AI endpoint URL.
+  ///
+  /// Enforces HTTPS for remote connections to prevent plaintext credential
+  /// interception via MITM attacks, while permitting HTTP for local loopback hosts
+  /// (`localhost`, `127.0.0.1`, `::1`) used during local LLM development.
+  static bool isValidEndpoint(String url) {
+    if (url.trim().isEmpty) return false;
+    final uri = Uri.tryParse(url.trim());
+    if (uri == null || !uri.hasScheme) return false;
+
+    final scheme = uri.scheme.toLowerCase();
+    if (scheme == 'https') return true;
+    if (scheme == 'http') {
+      final host = uri.host.toLowerCase();
+      return host == 'localhost' ||
+          host == '127.0.0.1' ||
+          host == '::1' ||
+          host == '[::1]';
+    }
+    return false;
+  }
+}
diff --git a/test/unit/services/ai_endpoint_validator_test.dart b/test/unit/services/ai_endpoint_validator_test.dart
new file mode 100644
index 0000000..8560a2b
--- /dev/null
+++ b/test/unit/services/ai_endpoint_validator_test.dart
@@ -0,0 +1,47 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:janus/services/ai_endpoint_validator.dart';
+
+void main() {
+  group('AiEndpointValidator', () {
+    test('allows valid HTTPS remote URLs', () {
+      expect(
+        AiEndpointValidator.isValidEndpoint('https://api.openai.com/v1'),
+        isTrue,
+      );
+      expect(
+        AiEndpointValidator.isValidEndpoint('https://api.deepseek.com'),
+        isTrue,
+      );
+    });
+
+    test('rejects unencrypted HTTP remote URLs', () {
+      expect(
+        AiEndpointValidator.isValidEndpoint('http://api.openai.com/v1'),
+        isFalse,
+      );
+      expect(
+        AiEndpointValidator.isValidEndpoint('http://example.com/api'),
+        isFalse,
+      );
+    });
+
+    test('allows HTTP URLs for local development loopback hosts', () {
+      expect(
+        AiEndpointValidator.isValidEndpoint('http://localhost:11434'),
+        isTrue,
+      );
+      expect(
+        AiEndpointValidator.isValidEndpoint('http://127.0.0.1:8080/v1'),
+        isTrue,
+      );
+      expect(AiEndpointValidator.isValidEndpoint('http://[::1]:11434'), isTrue);
+    });
+
+    test('rejects empty, invalid, or non-http/https URIs', () {
+      expect(AiEndpointValidator.isValidEndpoint(''), isFalse);
+      expect(AiEndpointValidator.isValidEndpoint('   '), isFalse);
+      expect(AiEndpointValidator.isValidEndpoint('ftp://server.com'), isFalse);
+      expect(AiEndpointValidator.isValidEndpoint('not_a_url'), isFalse);
+    });
+  });
+}
diff --git a/test/unit/settings/settings_provider_test.dart b/test/unit/settings/settings_provider_test.dart
index c799fe9..247db5d 100644
--- a/test/unit/settings/settings_provider_test.dart
+++ b/test/unit/settings/settings_provider_test.dart
@@ -414,6 +414,33 @@ void main() {
     });
 
     // AI
+    test('setEndPoint saves valid HTTPS and loopback endpoints', () async {
+      final container = ProviderContainer();
+      addTearDown(() => container.dispose());
+      await waitForInit(container);
+
+      final success = await notifierOf(
+        container,
+      ).setEndPoint('https://api.openai.com/v1');
+      expect(success, isTrue);
+      expect(
+        container.read(appSettingsProvider).value!.endPoint,
+        'https://api.openai.com/v1',
+      );
+    });
+
+    test('setEndPoint rejects unencrypted remote HTTP endpoints', () async {
+      final container = ProviderContainer();
+      addTearDown(() => container.dispose());
+      await waitForInit(container);
+
+      final success = await notifierOf(
+        container,
+      ).setEndPoint('http://insecure.remote.com/api');
+      expect(success, isFalse);
+      expect(container.read(appSettingsProvider).value!.endPoint, '');
+    });
+
     test('setUseAiDailySummary 更新 AI 日报开关', () async {
       final container = ProviderContainer();
       addTearDown(() => container.dispose());