diff --git a/app/pages/admin/agent-config.vue b/app/pages/admin/agent-config.vue
index ac0106f..317454e 100644
--- a/app/pages/admin/agent-config.vue
+++ b/app/pages/admin/agent-config.vue
@@ -136,7 +136,7 @@ onMounted(async () => {
       <!-- System Prompt -->
       <section class="config-section">
         <h2 class="section-title">系统提示词</h2>
-        <p class="section-desc">设置 agent 对话的全局系统提示词</p>
+        <p class="section-desc">设置 Agent 对话的全局系统提示词，引导模型行为</p>
         <textarea
           v-model="systemPrompt"
           class="config-textarea"
@@ -148,10 +148,10 @@ onMounted(async () => {
         </button>
       </section>
 
-      <!-- Guest Default Model -->
+      <!-- Default Model -->
       <section class="config-section">
-        <h2 class="section-title">未登录用户模型</h2>
-        <p class="section-desc">未登录用户（临时会话）使用的默认模型与标题生成模型</p>
+        <h2 class="section-title">默认模型</h2>
+        <p class="section-desc">所有用户的默认模型与标题生成模型。未自行配置模型的用户将自动使用此设置</p>
         <div class="model-row">
           <div class="model-field">
             <label class="field-label">默认模型</label>
diff --git a/app/pages/admin/global-config/index.vue b/app/pages/admin/global-config/index.vue
index 3a1218e..bd71646 100644
--- a/app/pages/admin/global-config/index.vue
+++ b/app/pages/admin/global-config/index.vue
@@ -17,9 +17,6 @@ const configMeta: ConfigMeta[] = [
   { key: 'siteName', label: '站点名称', description: '网站标题，显示在浏览器标签和页面上', type: 'string', group: '基本设置' },
   { key: 'siteIcon', label: '站点图标', description: 'favicon 图标，支持上传或填写 URL。推荐 32×32 PNG / 16×16 ICO', type: 'string', group: '基本设置' },
   { key: 'allowRegister', label: '允许注册', description: '是否开放新用户注册功能', type: 'boolean', group: '基本设置' },
-  { key: 'agentSystemPrompt', label: 'Agent 系统提示词', description: 'Agent 对话的默认系统提示词，引导模型行为', type: 'string', group: 'Agent 设置' },
-  { key: 'agentDefaultModelId', label: 'Agent 未登录默认模型 ID', description: '未登录用户（临时会话）使用的默认 LLM 模型 ID（数字，如 2）。留 0 则不设置', type: 'number', group: 'Agent 设置' },
-  { key: 'agentTitleModelId', label: 'Agent 标题生成模型 ID', description: '用于自动生成对话标题的 LLM 模型 ID（数字，如 2）。留 0 则不自动生成标题', type: 'number', group: 'Agent 设置' },
 ]
 
 const form = reactive<Record<string, any>>(
diff --git a/app/pages/chat/[agentSlug]/index.vue b/app/pages/chat/[agentSlug]/index.vue
index 90ad273..4006c62 100644
--- a/app/pages/chat/[agentSlug]/index.vue
+++ b/app/pages/chat/[agentSlug]/index.vue
@@ -28,7 +28,7 @@ const isCustomPrompt = computed(() =>
   !!(sessions.currentSession.value?.systemPrompt?.trim()),
 );
 const preferredModelId = ref<number | null>(null);
-const guestDefaultModelId = ref<number | null>(null);
+const globalDefaultModelId = ref<number | null>(null);
 
 interface ModelOption {
   id: number;
@@ -65,9 +65,9 @@ watch(
       currentModelId.value = null;
     } else if (mid === null) {
       const fallbackSource = auth.loggedIn.value
-        ? (preferredModelId.value && modelList.some((m) => m.id === preferredModelId.value) ? preferredModelId.value : null)
-        : (guestDefaultModelId.value && modelList.some((m) => m.id === guestDefaultModelId.value) ? guestDefaultModelId.value : null);
-      const fallback = fallbackSource ?? modelList[0].id;
+        ? (preferredModelId.value && modelList.some((m) => m.id === preferredModelId.value) ? preferredModelId.value : (globalDefaultModelId.value && modelList.some((m) => m.id === globalDefaultModelId.value) ? globalDefaultModelId.value : null))
+        : (globalDefaultModelId.value && modelList.some((m) => m.id === globalDefaultModelId.value) ? globalDefaultModelId.value : null);
+      const fallback = fallbackSource ?? modelList[0]?.id ?? null;
       currentModelId.value = fallback;
     }
   },
@@ -127,9 +127,7 @@ async function loadModels() {
       providerName: m.providerName ?? "—",
       supportsTools: m.supportsTools ?? 1,
     }));
-    if (isGuest) {
-      guestDefaultModelId.value = res.data?.defaultModelId ?? null;
-    }
+    globalDefaultModelId.value = res.data?.defaultModelId ?? null;
   } catch {
     models.value = [];
   }
diff --git a/packages/drizzle-pkg/db.sqlite b/packages/drizzle-pkg/db.sqlite
index 2c425ae..9f3baeb 100644
Binary files a/packages/drizzle-pkg/db.sqlite and b/packages/drizzle-pkg/db.sqlite differ
diff --git a/server/api/admin/agent-config/index.get.ts b/server/api/admin/agent-config/index.get.ts
index dcd2b6d..a18feb0 100644
--- a/server/api/admin/agent-config/index.get.ts
+++ b/server/api/admin/agent-config/index.get.ts
@@ -2,7 +2,7 @@ import { defineWrappedResponseHandler } from "#server/utils/handler";
 import { R } from "#server/utils/response";
 import { requireAdmin } from "#server/utils/admin-guard";
 import { getConfigGlobal } from "#server/utils/context";
-import { listSystemModels } from "#server/service/llm";
+import { listAllEnabledModels } from "#server/service/llm";
 
 export default defineWrappedResponseHandler(async (event) => {
   await requireAdmin(event);
@@ -14,7 +14,7 @@ export default defineWrappedResponseHandler(async (event) => {
     getConfigGlobal("agentPublicToolSlugs"),
   ]);
 
-  const systemModels = await listSystemModels();
+  const systemModels = await listAllEnabledModels();
 
   return R.success({
     systemPrompt,
diff --git a/server/api/agents/[agentSlug]/chat/index.post.ts b/server/api/agents/[agentSlug]/chat/index.post.ts
index 28f2cd1..1613d1d 100644
--- a/server/api/agents/[agentSlug]/chat/index.post.ts
+++ b/server/api/agents/[agentSlug]/chat/index.post.ts
@@ -1,5 +1,5 @@
 import { defineEventHandler, getRouterParam, readBody, setResponseHeaders } from "h3";
-import { getCurrentUser, getConfigUser } from "#server/utils/context";
+import { getCurrentUser, getConfigUser, getConfigGlobal } from "#server/utils/context";
 import { resolveAgentIdentity } from "#server/service/agent/identity";
 import { getSessionByIdAndUser } from "#server/service/agent/session";
 import { getAgentBySlug } from "#server/service/agent/agent";
@@ -61,6 +61,8 @@ export default defineEventHandler(async (event) => {
     preferredModelId = (await getConfigUser(event, "preferredLlmModelId")) ?? null;
   }
 
+  const globalDefaultModelId = (await getConfigGlobal("agentDefaultModelId")) ?? null;
+
   const user = identity.userId ? await getCurrentUser(event) : null;
 
   const { response } = await executeChat({
@@ -81,6 +83,7 @@ export default defineEventHandler(async (event) => {
     },
     ip,
     preferredModelId,
+    globalDefaultModelId,
     requestId: event.context.requestId,
     registerAbort: registerAbortController,
     unregisterAbort: unregisterAbortController,
diff --git a/server/api/agents/[agentSlug]/sessions/index.post.ts b/server/api/agents/[agentSlug]/sessions/index.post.ts
index 660eed0..a6c4b87 100644
--- a/server/api/agents/[agentSlug]/sessions/index.post.ts
+++ b/server/api/agents/[agentSlug]/sessions/index.post.ts
@@ -3,7 +3,7 @@ import { R } from "#server/utils/response";
 import { resolveAgentIdentity } from "#server/service/agent/identity";
 import { createSession } from "#server/service/agent/session";
 import { generateTempToken, setTempTokenCookie, getTempTokenTtlMs } from "#server/service/agent/temp-token";
-import { getConfigUser } from "#server/utils/context";
+import { getConfigUser, getConfigGlobal } from "#server/utils/context";
 import { getAgentBySlug } from "#server/service/agent/agent";
 
 export default defineWrappedResponseHandler(async (event) => {
@@ -44,6 +44,13 @@ export default defineWrappedResponseHandler(async (event) => {
     modelId = agent.defaultModelId;
   }
 
+  if (!modelId) {
+    const globalDefault = await getConfigGlobal("agentDefaultModelId");
+    if (globalDefault && globalDefault > 0) {
+      modelId = globalDefault;
+    }
+  }
+
   const body = await readBody(event).catch(() => ({}));
   const systemPrompt: string | null =
     typeof body?.systemPrompt === "string" && body.systemPrompt.trim().length > 0
diff --git a/server/api/llm/models/index.get.ts b/server/api/llm/models/index.get.ts
index 302f789..46e5020 100644
--- a/server/api/llm/models/index.get.ts
+++ b/server/api/llm/models/index.get.ts
@@ -1,10 +1,29 @@
 import { defineWrappedResponseHandler } from "#server/utils/handler";
 import { R } from "#server/utils/response";
-import { getCurrentUser } from "#server/utils/context";
-import { listAllEnabledModelsForUser } from "#server/service/llm";
+import { getCurrentUser, getConfigGlobal } from "#server/utils/context";
+import { listAllEnabledModelsForUser, getModelWithProviderByIdAny } from "#server/service/llm";
 
 export default defineWrappedResponseHandler(async (event) => {
   const user = await getCurrentUser(event);
-  const list = await listAllEnabledModelsForUser(user?.id ?? null);
-  return R.success({ list });
+  const [list, globalDefaultModelId] = await Promise.all([
+    listAllEnabledModelsForUser(user?.id ?? null),
+    getConfigGlobal("agentDefaultModelId"),
+  ]);
+
+  if (globalDefaultModelId && !list.some((m) => m.id === globalDefaultModelId)) {
+    const row = await getModelWithProviderByIdAny(globalDefaultModelId);
+    if (row) {
+      list.unshift({
+        id: row.model.id,
+        name: row.model.name,
+        modelId: row.model.modelId,
+        type: row.model.type,
+        providerName: row.provider.name,
+        providerId: row.provider.id,
+        supportsTools: row.model.supportsTools,
+      });
+    }
+  }
+
+  return R.success({ list, defaultModelId: globalDefaultModelId ?? null });
 });
diff --git a/server/service/agent/chat-engine.ts b/server/service/agent/chat-engine.ts
index 36878d1..d0a3a39 100644
--- a/server/service/agent/chat-engine.ts
+++ b/server/service/agent/chat-engine.ts
@@ -45,6 +45,7 @@ export interface ChatEngineParams {
   };
   ip: string;
   preferredModelId?: number | null;
+  globalDefaultModelId?: number | null;
   requestId?: string;
   registerAbort: (sessionId: string, controller: AbortController) => void;
   unregisterAbort: (sessionId: string) => void;
@@ -222,13 +223,13 @@ export async function executeChat(params: ChatEngineParams): Promise<ChatEngineR
 
   let resolvedModel;
   if (user) {
-    const targetModelId = session.modelId ?? params.preferredModelId ?? agent.defaultModelId;
+    const targetModelId = session.modelId ?? params.preferredModelId ?? agent.defaultModelId ?? params.globalDefaultModelId;
     if (!targetModelId) {
       throw createError({ statusCode: 400, statusMessage: "未配置模型，请先在设置中选择模型" });
     }
     resolvedModel = await resolveModelForUser(targetModelId, user.id);
   } else {
-    const targetModelId = session.modelId ?? agent.defaultModelId;
+    const targetModelId = session.modelId ?? agent.defaultModelId ?? params.globalDefaultModelId;
     if (!targetModelId) {
       throw createError({ statusCode: 400, statusMessage: "系统未配置默认模型" });
     }
diff --git a/server/service/llm/index.ts b/server/service/llm/index.ts
index 24353cd..a6aa372 100644
--- a/server/service/llm/index.ts
+++ b/server/service/llm/index.ts
@@ -299,6 +299,27 @@ export async function listSystemModels(): Promise<LlmModelRow[]> {
     .orderBy(desc(llmModels.createdAt));
 }
 
+export async function listAllEnabledModels(): Promise<LlmModelRow[]> {
+  return dbGlobal
+    .select({
+      id: llmModels.id,
+      providerId: llmModels.providerId,
+      name: llmModels.name,
+      modelId: llmModels.modelId,
+      type: llmModels.type,
+      enabled: llmModels.enabled,
+      description: llmModels.description,
+      maxTokens: llmModels.maxTokens,
+      supportsTools: llmModels.supportsTools,
+      createdAt: llmModels.createdAt,
+      updatedAt: llmModels.updatedAt,
+    })
+    .from(llmModels)
+    .innerJoin(llmProviders, eq(llmModels.providerId, llmProviders.id))
+    .where(eq(llmModels.enabled, 1))
+    .orderBy(desc(llmModels.createdAt));
+}
+
 // ============ 通用 Model 查询（agent 对话核心使用）============
 
 export async function getModelWithProviderById(modelId: number, userId: number | null) {
diff --git a/server/service/llm/model-resolver.ts b/server/service/llm/model-resolver.ts
index 2d5b3ce..44e12e4 100644
--- a/server/service/llm/model-resolver.ts
+++ b/server/service/llm/model-resolver.ts
@@ -40,10 +40,13 @@ export async function resolveModelForUser(
   modelId: number,
   userId: number | null,
 ): Promise<ResolvedModel | null> {
-  const modelRow = userId
+  let modelRow = userId
     ? await getModelWithProviderById(modelId, userId)
     : await getSystemModelWithProviderById(modelId);
   if (!modelRow) {
+    modelRow = await getModelWithProviderByIdAny(modelId);
+  }
+  if (!modelRow) {
     logger.warn("[MODEL-RESOLVER] modelId=%d not found for userId=%s", modelId, userId);
     return null;
   }