diff --git a/README.md b/README.md
index 02f9007..95847ab 100644
--- a/README.md
+++ b/README.md
@@ -62,7 +62,7 @@ Open **Providers**, click **Add Provider**, then choose a built-in preset or **O
 
 ### 2. Configure routing
 
-Open **Routing** to choose the default route, add conditional rules, configure request rewrites, and set fallback behavior.
+Open **Routing** to add conditional rules, configure request rewrites, and set fallback behavior.
 
 Use **Add Routing Rule** for request conditions, model-prefix routing, or rule-level fallback targets.
 
diff --git a/README_zh.md b/README_zh.md
index 3963630..15bdb68 100644
--- a/README_zh.md
+++ b/README_zh.md
@@ -24,7 +24,7 @@ Claude Code Router Desktop 是一个本地网关和桌面控制台，用来把 C
 
 - **概览仪表盘**：查看系统状态、用量组件、账号余额、模型分布和分享卡片。
 - **Provider 管理**：添加预设或自定义端点，探测协议支持，检测模型连通性，管理凭据，并在可用时查看账号余额。
-- **路由规则**：配置默认路由、条件路由、模型前缀规则、失败降级和请求改写。
+- **路由规则**：配置条件路由、模型前缀规则、失败降级和请求改写。
 - **Agent配置**：为 Claude Code、Codex 和 ZCode 配置启动入口、模型、作用范围和多开 App 配置。
 - **网关兼容层**：通过本地 CCR 模型网关转换支持的客户端请求。
 - **代理模式**：通过本地代理捕获支持的 API 流量，可选系统代理和网络捕获。
@@ -61,7 +61,7 @@ CCR 可以完全通过桌面 UI 完成配置。首次使用建议按下面顺序
 
 ### 2. 设置路由
 
-打开 **路由**，选择默认路由，添加条件规则，配置请求改写和失败降级。
+打开 **路由**，添加条件规则，配置请求改写和失败降级。
 
 如果需要更细粒度控制，使用 **添加路由规则** 添加模型前缀、请求条件或规则级失败降级目标。
 
diff --git a/docs/src/content/docs/en/configuration/routing.md b/docs/src/content/docs/en/configuration/routing.md
index 5c534d2..a378c56 100644
--- a/docs/src/content/docs/en/configuration/routing.md
+++ b/docs/src/content/docs/en/configuration/routing.md
@@ -9,9 +9,9 @@ lead: Choose the model for a request, then automatically retry or switch to fall
 
 ### Claude Code
 
-The built-in Claude Code route detects requests from Claude Code and routes main requests to the Claude Code Agent Config model or the default route model.
+The built-in Claude Code route detects requests from Claude Code and routes main requests to the Claude Code Agent Config model.
 
-Claude Code **main requests** use the Claude Code Agent Config model by default; if it is unset, they use the Routing page default model. CCR also automatically removes the first `x-anthropic-billing-header` system message injected by Claude Code so that billing helper messages do not affect later routing decisions. Claude Code Subagent, Task, and Workflow-created agents can still choose different models through the tag mechanism below.
+Claude Code **main requests** use the Claude Code Agent Config model. If that model is unset, the built-in route remains inactive. CCR also automatically removes the first `x-anthropic-billing-header` system message injected by Claude Code so that billing helper messages do not affect later routing decisions. Claude Code Subagent, Task, and Workflow-created agents can still choose different models through the tag mechanism below.
 
 #### Subagent / Workflow Auto-Routing
 
@@ -176,7 +176,7 @@ Configure **Default on failure** at the top of the Routing page:
 2. If you choose **Retry**, set `Retries`.
 3. If you choose **Fallback targets**, add backup models in priority order.
 
-Global Fallback applies to the default route and to rules that do not define their own Fallback.
+Global Fallback applies to routing rules that do not define their own Fallback.
 
 ### Rule-Level Fallback
 
diff --git a/docs/src/content/docs/zh/configuration.md b/docs/src/content/docs/zh/configuration.md
index 26df10a..6515d0f 100644
--- a/docs/src/content/docs/zh/configuration.md
+++ b/docs/src/content/docs/zh/configuration.md
@@ -16,7 +16,7 @@ lead: 深入配置概览仪表盘、API 密钥、服务、供应商、路由、A
 | 服务配置 | Host、Port、代理模式、系统代理、网络捕获和 CA 证书 |
 | 供应商配置 | 上游服务、协议、基础 URL、模型列表和凭据 |
 | 一键导入供应商 | Provider deeplink 协议、Manifest 导入、一键导入按钮和安全边界 |
-| 路由配置 | 默认路由、条件规则、fallback 和请求改写 |
+| 路由配置 | 条件规则、fallback 和请求改写 |
 | 日志&观测 | 请求日志、Agent 执行追踪、工具调用和工具结果 |
 | Fusion 组合模型 | 把基础模型与视觉、搜索、MCP 工具组合成新的可选模型 |
 | Agent配置 | Agent 启动方式、模型、作用范围、多开和 Bot 绑定 |
diff --git a/docs/src/content/docs/zh/configuration/routing.md b/docs/src/content/docs/zh/configuration/routing.md
index 32fb625..c00f069 100644
--- a/docs/src/content/docs/zh/configuration/routing.md
+++ b/docs/src/content/docs/zh/configuration/routing.md
@@ -9,9 +9,9 @@ lead: 设置请求如何选择模型，并在失败时通过 Fallback 自动重
 
 ### Claude Code
 
-Claude Code 内置路由的作用是识别 Claude Code 发来的请求，并把主请求路由到 Claude Code Agent 配置或默认路由中的模型。
+Claude Code 内置路由的作用是识别 Claude Code 发来的请求，并把主请求路由到 Claude Code Agent 配置中的模型。
 
-Claude Code **主请求** 默认使用 Claude Code Agent 配置中的模型；如果未设置，则使用路由页的默认模型。CCR 也会自动删除 Claude Code 注入的第一条 `x-anthropic-billing-header` system 消息，避免这类计费辅助消息影响后续路由判断。Claude Code 创建的 Subagent、Task 或 Workflow 内部 Agent 可以继续用下面的标签机制自动选择不同模型。
+Claude Code **主请求** 使用 Claude Code Agent 配置中的模型；如果未设置，该内置路由不会生效。CCR 也会自动删除 Claude Code 注入的第一条 `x-anthropic-billing-header` system 消息，避免这类计费辅助消息影响后续路由判断。Claude Code 创建的 Subagent、Task 或 Workflow 内部 Agent 可以继续用下面的标签机制自动选择不同模型。
 
 #### Subagent / Workflow 自动路由
 
@@ -176,7 +176,7 @@ Fallback 处理请求失败后的降级。第一次选模型由路由完成；
 2. 如果选择 **继续重试**，填写 `Retries`。
 3. 如果选择 **失败降级目标**，按优先级添加备用模型。
 
-全局 Fallback 会应用到默认路由，以及没有单独配置 Fallback 的规则。
+全局 Fallback 会应用到没有单独配置 Fallback 的规则。
 
 ### 规则级失败降级
 
diff --git a/docs/src/content/docs/zh/troubleshooting.md b/docs/src/content/docs/zh/troubleshooting.md
index da049b7..f37bc12 100644
--- a/docs/src/content/docs/zh/troubleshooting.md
+++ b/docs/src/content/docs/zh/troubleshooting.md
@@ -13,7 +13,7 @@ A: 服务运行状态、Agent 启动方式、配置应用状态和作用范围
 
 ### Q: 请求命中了错误模型怎么办？
 
-A: 请求日志会展示 `request model`、`resolved provider` 和 `resolved model`。路由配置页包含默认路由、规则顺序、匹配条件和 fallback。
+A: 请求日志会展示 `request model`、`resolved provider` 和 `resolved model`。路由配置页包含规则顺序、匹配条件和 fallback。
 
 ### Q: 供应商返回 401 或 403 怎么处理？
 
diff --git a/src/main/config.ts b/src/main/config.ts
index 89a9c4d..bccbc7d 100644
--- a/src/main/config.ts
+++ b/src/main/config.ts
@@ -1190,10 +1190,6 @@ function parseRouter(value: unknown): Partial<RouterConfig> | undefined {
   }
 
   const router: Partial<RouterConfig> = {};
-  const defaultRoute = readString(value.default);
-  if (defaultRoute) {
-    router.default = defaultRoute;
-  }
   const builtInRules = parseRouterBuiltInRules(value.builtInRules ?? value.builtinRules ?? value.agentRules);
   if (builtInRules) {
     router.builtInRules = builtInRules;
diff --git a/src/main/profile-launch-service.ts b/src/main/profile-launch-service.ts
index cd2d01a..8aecd07 100644
--- a/src/main/profile-launch-service.ts
+++ b/src/main/profile-launch-service.ts
@@ -514,11 +514,7 @@ function profileGatewayConfigWithToken(config: AppConfig, profile: ReturnType<ty
         key: token,
         name: `Profile: ${profile.name?.trim() || profile.id || profile.agent}`
       }
-    ],
-    Router: {
-      ...config.Router,
-      ...(profile.model.trim() ? { default: profile.model.trim() } : {})
-    }
+    ]
   };
 }
 
diff --git a/src/main/profile-service.ts b/src/main/profile-service.ts
index e8cf65e..87be49b 100644
--- a/src/main/profile-service.ts
+++ b/src/main/profile-service.ts
@@ -1304,10 +1304,6 @@ function gatewayEndpoint(config: AppConfig): string {
 }
 
 function defaultClientModel(config: AppConfig): string {
-  const configuredDefault = normalizeClientModel(config.Router.default);
-  if (configuredDefault) {
-    return configuredDefault;
-  }
   const preferred = config.Providers.find((provider) => provider.name === config.preferredProvider) ?? config.Providers[0];
   if (preferred?.name && preferred.models[0]) {
     return `${preferred.name}/${preferred.models[0]}`;
diff --git a/src/main/zcode-profile-config.ts b/src/main/zcode-profile-config.ts
index 8ac037c..9e62c65 100644
--- a/src/main/zcode-profile-config.ts
+++ b/src/main/zcode-profile-config.ts
@@ -282,10 +282,6 @@ function gatewayEndpoint(config: AppConfig): string {
 }
 
 function defaultClientModel(config: AppConfig): string {
-  const configuredDefault = normalizeClientModel(config.Router.default);
-  if (configuredDefault) {
-    return configuredDefault;
-  }
   const preferred = config.Providers.find((provider) => provider.name === config.preferredProvider) ?? config.Providers[0];
   if (preferred?.name && preferred.models[0]) {
     return `${preferred.name}/${preferred.models[0]}`;
diff --git a/src/renderer/components/ui/switch.tsx b/src/renderer/components/ui/switch.tsx
index 5440546..616f640 100644
--- a/src/renderer/components/ui/switch.tsx
+++ b/src/renderer/components/ui/switch.tsx
@@ -6,8 +6,8 @@ export interface SwitchProps extends Omit<React.InputHTMLAttributes<HTMLInputEle
 }
 
 const Switch = React.forwardRef<HTMLInputElement, SwitchProps>(
-  ({ checked = false, className, disabled, onChange, onCheckedChange, ...props }, ref) => (
-    <span className={cn("relative inline-flex h-[30px] w-[54px] shrink-0", className)}>
+  ({ checked = false, className, disabled, onChange, onCheckedChange, title, ...props }, ref) => (
+    <span className={cn("relative inline-flex h-[30px] w-[54px] shrink-0", className)} title={title}>
       <input
         aria-checked={checked}
         checked={checked}
@@ -19,6 +19,7 @@ const Switch = React.forwardRef<HTMLInputElement, SwitchProps>(
         }}
         ref={ref}
         role="switch"
+        title={title}
         type="checkbox"
         {...props}
       />
diff --git a/src/renderer/pages/home/components/routing.tsx b/src/renderer/pages/home/components/routing.tsx
index 1d702f8..4f54c8e 100644
--- a/src/renderer/pages/home/components/routing.tsx
+++ b/src/renderer/pages/home/components/routing.tsx
@@ -4,11 +4,11 @@ import {
   CardHeader, Check, CircleAlert, clampNumber, cn, createRouteModelOptions, createRoutingRewriteDraftRow,
   Dialog, DialogBody, DialogContent, DialogFooter, DialogHeader, DialogTitle,
   disclosureSpringTransition, Field, formatRouterRuleCondition, formatRouterRuleTarget, GatewayProviderConfig, Input,
-  Info, motion, normalizeRouterFallbackConfig, Pencil, Plus, Route, RouterFallbackConfig,
+  AppI18nContext, appCopy, ExternalLink, Info, motion, normalizeRouterFallbackConfig, Pencil, Plus, Route, RouterFallbackConfig,
   RouterBuiltInAgentRuleId, RouterFallbackMode, routerConditionSourceOptions, routerFallbackModeOptions, RouterRule, routerRewriteOperationOptions, routerRuleOperatorOptions,
   RouterBuiltInAgentRuleConfig,
   RouteTargetControl, routingRuleRowMatchesQuery, Search, SelectControl, Toggle, translateOptions,
-  Trash2, uniqueStrings, useAppText, useMemo, useState, X
+  Trash2, uniqueStrings, useAppText, useContext, useMemo, useState, X
 } from "../shared";
 import { ROUTER_FALLBACK_MAX_RETRY_COUNT } from "../../../../shared/app";
 export function RoutingView({
@@ -100,6 +100,7 @@ export function RoutingView({
                   {visibleRules.map((row) => {
                     const rowSourceLabel = row.builtInAgent ? t(row.sourceLabel) : row.sourceLabel;
                     const rowTarget = row.target === "Profile model unset" ? t(row.target) : row.target;
+                    const toggleDisabledReason = row.toggleDisabledReason ? t(row.toggleDisabledReason) : undefined;
                     return (
                       <AnimatedListItem
                         className="grid min-h-[58px] grid-cols-[minmax(160px,0.8fr)_minmax(220px,1fr)_minmax(240px,1.15fr)_84px_148px] items-center gap-3 px-4 py-2.5 transition-colors hover:bg-muted/35"
@@ -108,7 +109,7 @@ export function RoutingView({
                       <div className="min-w-0">
                         <div className="flex min-w-0 items-center gap-2">
                           <div className="truncate text-[12px] font-semibold">{row.name || t("Unnamed")}</div>
-                          {row.builtInAgent ? <BuiltInRouteInfoIcon description={builtInRouteDescription(row.builtInAgent, t)} /> : null}
+                          {row.builtInAgent ? <BuiltInRouteInfoIcon agent={row.builtInAgent} /> : null}
                           {row.builtInAgent ? <Badge variant="outline">{t("Built-in")}</Badge> : row.readonly ? <Badge variant="outline">{t("Plugin")}</Badge> : null}
                         </div>
                         <div className="mt-0.5 truncate font-mono text-[11px] text-muted-foreground" title={`${rowSourceLabel}: ${row.ruleId}`}>
@@ -129,17 +130,28 @@ export function RoutingView({
                         {row.builtInAgent ? null : rowTarget}
                       </div>
                       <div className="flex min-w-0 items-center gap-2">
-                        <Toggle
-                          checked={row.enabled}
-                          disabled={row.readonly || row.toggleDisabled}
-                          onChange={(enabled) => {
-                            if (row.builtInAgent) {
-                              updateBuiltInRule(row.builtInAgent, { enabled });
-                            } else if (row.index !== undefined) {
-                              updateRule(row.index, { enabled });
-                            }
-                          }}
-                        />
+                        <span
+                          aria-label={toggleDisabledReason}
+                          className="group relative inline-flex rounded-full outline-none focus-visible:ring-2 focus-visible:ring-ring/30"
+                          tabIndex={toggleDisabledReason ? 0 : undefined}
+                        >
+                          <Toggle
+                            checked={row.enabled}
+                            disabled={row.readonly || row.toggleDisabled}
+                            onChange={(enabled) => {
+                              if (row.builtInAgent) {
+                                updateBuiltInRule(row.builtInAgent, { enabled });
+                              } else if (row.index !== undefined) {
+                                updateRule(row.index, { enabled });
+                              }
+                            }}
+                          />
+                          {toggleDisabledReason ? (
+                            <span className="pointer-events-none absolute right-full top-1/2 z-[80] mr-2 hidden w-[240px] -translate-y-1/2 rounded-md border border-border bg-popover px-2.5 py-2 text-left text-[11px] font-medium leading-4 text-popover-foreground shadow-card group-hover:block group-focus:block group-focus-within:block">
+                              {toggleDisabledReason}
+                            </span>
+                          ) : null}
+                        </span>
                       </div>
                       <div className="flex items-center justify-end gap-1">
                         {!row.builtInAgent ? (
@@ -185,22 +197,55 @@ export function RoutingView({
   );
 }
 
-function BuiltInRouteInfoIcon({ description }: { description: string }) {
+function BuiltInRouteInfoIcon({ agent }: { agent: RouterBuiltInAgentRuleId }) {
+  const t = useAppText();
+  const copy = useContext(AppI18nContext);
+  const description = builtInRouteDescription(agent, t);
+  const docsUrl = builtInRouteDocsUrl(agent, copy === appCopy.zh ? "zh" : "en");
+
   return (
-    <span aria-label={description} className="group relative inline-flex h-5 w-5 shrink-0 items-center justify-center rounded-full text-muted-foreground outline-none focus-visible:ring-2 focus-visible:ring-ring/30" tabIndex={0} title={description}>
+    <span aria-label={description} className="group relative inline-flex h-5 w-5 shrink-0 items-center justify-center rounded-full text-muted-foreground outline-none focus-visible:ring-2 focus-visible:ring-ring/30" tabIndex={0}>
       <Info className="h-3.5 w-3.5" aria-hidden="true" />
-      <span className="pointer-events-none absolute left-full top-1/2 z-[80] ml-2 hidden w-[260px] -translate-y-1/2 rounded-md border border-border bg-popover px-2.5 py-2 text-left text-[11px] font-medium leading-4 text-popover-foreground shadow-card group-hover:block group-focus:block">
-        {description}
+      <span className="absolute left-full top-1/2 z-[80] hidden w-[232px] -translate-y-1/2 pl-2 group-hover:block group-focus:block group-focus-within:block">
+        <span className="block rounded-md border border-border bg-popover px-2.5 py-2 text-left text-[11px] font-medium leading-4 text-popover-foreground shadow-card">
+          <span>{description}</span>
+          <a
+            className="ml-1 inline-flex items-center gap-1 text-primary underline-offset-2 hover:underline focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring/30"
+            href={docsUrl}
+            onClick={(event) => {
+              event.preventDefault();
+              openExternalUrl(docsUrl);
+            }}
+            rel="noreferrer"
+            target="_blank"
+          >
+            {t("Docs")}
+            <ExternalLink className="h-3 w-3" />
+          </a>
+        </span>
       </span>
     </span>
   );
 }
 
 function builtInRouteDescription(agent: RouterBuiltInAgentRuleId, t: (value: string) => string): string {
-  if (agent === "claude-code") {
-    return t("Routes Claude Code requests by matching the Claude user-agent and setting request.body.model to the Claude Code profile or default model.");
+  return agent === "claude-code"
+    ? t("Identifies the Claude Code user-agent to provide deep Claude Code integration.")
+    : t("Identifies the Codex user-agent to provide deep Codex integration.");
+}
+
+function builtInRouteDocsUrl(agent: RouterBuiltInAgentRuleId, language: "en" | "zh"): string {
+  const path = language === "zh" ? "/configuration/routing" : "/en/configuration/routing";
+  const hash = agent === "claude-code" ? "claude-code" : "codex";
+  return `https://ccrdesk.top${path}#${hash}`;
+}
+
+function openExternalUrl(url: string) {
+  if (window.ccr?.openExternal) {
+    void window.ccr.openExternal(url).catch(() => undefined);
+    return;
   }
-  return t("Routes Codex requests by matching the Codex user-agent and setting request.body.model to the Codex profile or default model.");
+  window.open(url, "_blank", "noopener,noreferrer");
 }
 
 function RouterFallbackControl({
diff --git a/src/renderer/pages/home/shared/controls.tsx b/src/renderer/pages/home/shared/controls.tsx
index b8bb572..3d312ed 100644
--- a/src/renderer/pages/home/shared/controls.tsx
+++ b/src/renderer/pages/home/shared/controls.tsx
@@ -529,8 +529,8 @@ export function KeyValueRowsControl({
   );
 }
 
-export function Toggle({ checked, disabled = false, onChange }: { checked: boolean; disabled?: boolean; onChange: (checked: boolean) => void }) {
-  return <Switch checked={checked} disabled={disabled} onCheckedChange={onChange} />;
+export function Toggle({ checked, disabled = false, onChange, title }: { checked: boolean; disabled?: boolean; onChange: (checked: boolean) => void; title?: string }) {
+  return <Switch checked={checked} disabled={disabled} onCheckedChange={onChange} title={title} />;
 }
 
 export type MetricTone = "amber" | "blue" | "indigo" | "rose" | "slate" | "teal";
diff --git a/src/renderer/pages/home/shared/i18n.tsx b/src/renderer/pages/home/shared/i18n.tsx
index 9d9aef3..cf70595 100644
--- a/src/renderer/pages/home/shared/i18n.tsx
+++ b/src/renderer/pages/home/shared/i18n.tsx
@@ -644,8 +644,8 @@ export const appCopy: Record<ResolvedLanguage, AppCopy> = {
       "Check trust": "检查信任",
       "Choose where each agent uses CCR.": "选择每个 Agent 在哪里使用 CCR。",
       "Built-in": "内置",
-      "Routes Claude Code requests by matching the Claude user-agent and setting request.body.model to the Claude Code profile or default model.": "通过匹配 Claude user-agent 路由 Claude Code 请求，并将 request.body.model 设置为 Claude Code 配置档案模型或默认模型。",
-      "Routes Codex requests by matching the Codex user-agent and setting request.body.model to the Codex profile or default model.": "通过匹配 Codex user-agent 路由 Codex 请求，并将 request.body.model 设置为 Codex 配置档案模型或默认模型。",
+      "Identifies the Claude Code user-agent to provide deep Claude Code integration.": "通过识别 Claude Code 的 user-agent，实现对 Claude Code 的深度适配。",
+      "Identifies the Codex user-agent to provide deep Codex integration.": "通过识别 Codex 的 user-agent，实现对 Codex 的深度适配。",
       "Click Check Connection to verify connectivity with a real model request.": "点击检测连通性，用一次真实模型请求验证是否可用。",
       "Click Add to create one": "点击添加创建一项",
       "Click Install to add one": "点击安装添加一项",
@@ -859,6 +859,7 @@ export const appCopy: Record<ResolvedLanguage, AppCopy> = {
       "None": "无",
       "Not configured": "未配置",
       "Not running": "未运行",
+      "Agent profiles are disabled.": "Agent 配置档案已关闭。",
       "Open": "打开",
       "Open Agent": "打开Agent",
       "Open CA": "打开 CA",
@@ -883,6 +884,10 @@ export const appCopy: Record<ResolvedLanguage, AppCopy> = {
       "Phone Wi-Fi target": "手机 Wi-Fi 目标",
       "Plugin": "插件",
       "Profile model unset": "未设置配置档案模型",
+      "Enable a Claude Code profile before enabling this built-in route.": "请先启用一个 Claude Code 配置档案，再启用此内置路由。",
+      "Enable a Codex profile before enabling this built-in route.": "请先启用一个 Codex 配置档案，再启用此内置路由。",
+      "Set a model on the Claude Code profile before enabling this built-in route.": "请先为 Claude Code 配置档案设置模型，再启用此内置路由。",
+      "Set a model on the Codex profile before enabling this built-in route.": "请先为 Codex 配置档案设置模型，再启用此内置路由。",
       "Plugin apps must be a JSON array.": "插件 App 必须是 JSON 数组。",
       "Plugin config JSON": "插件配置 JSON",
       "Plugin config must be a JSON object.": "插件配置必须是 JSON 对象。",
@@ -1354,6 +1359,7 @@ export const appCopy: Record<ResolvedLanguage, AppCopy> = {
       "Detecting icon": "正在检测图标",
       "Detecting provider": "正在检测供应商",
       "Disabled": "已禁用",
+      "Docs": "文档",
       "Edit description": "编辑描述",
       "Expand": "展开",
       "Expand models": "展开模型",
diff --git a/src/renderer/pages/home/shared/profiles.ts b/src/renderer/pages/home/shared/profiles.ts
index 1f8c827..bd092eb 100644
--- a/src/renderer/pages/home/shared/profiles.ts
+++ b/src/renderer/pages/home/shared/profiles.ts
@@ -389,10 +389,6 @@ export function gatewayEndpointFromConfig(config: AppConfig): string {
 }
 
 export function defaultProfileClientModel(config: AppConfig): string {
-  const configuredDefault = normalizeProfileClientModel(config.Router.default);
-  if (configuredDefault) {
-    return configuredDefault;
-  }
   const preferred = config.Providers.find((provider) => provider.name === config.preferredProvider) ?? config.Providers[0];
   if (preferred?.name && preferred.models[0]) {
     return `${preferred.name}/${preferred.models[0]}`;
diff --git a/src/renderer/pages/home/shared/routing.ts b/src/renderer/pages/home/shared/routing.ts
index 53c014e..397b133 100644
--- a/src/renderer/pages/home/shared/routing.ts
+++ b/src/renderer/pages/home/shared/routing.ts
@@ -386,10 +386,11 @@ export function normalizeRouterConfig(value: Partial<RouterConfig> | undefined):
   const router = {
     ...fallbackConfig.Router,
     ...(value || {})
-  };
+  } as RouterConfig & { default?: unknown };
+  const { default: _legacyDefault, ...routerWithoutLegacyDefault } = router;
   const rules = normalizeRouterRules((value as Record<string, unknown> | undefined)?.rules) ?? [];
   return {
-    ...router,
+    ...routerWithoutLegacyDefault,
     builtInRules: normalizeRouterBuiltInRules((value as Record<string, unknown> | undefined)?.builtInRules),
     fallback: normalizeRouterFallbackConfig((value as Record<string, unknown> | undefined)?.fallback),
     rules
@@ -847,7 +848,7 @@ export function buildRoutingRuleRows(config: AppConfig): RoutingRuleRow[] {
 export function buildBuiltInAgentRoutingRows(config: AppConfig): RoutingRuleRow[] {
   return routerBuiltInAgentRuleIds.map((agent): RoutingRuleRow => {
     const target = routerBuiltInAgentRouteTarget(config, agent);
-    const profileEnabled = Boolean(routerBuiltInAgentProfile(config, agent));
+    const toggleDisabledReason = routerBuiltInAgentRuleDisabledReason(config, agent);
     return {
       builtInAgent: agent,
       condition: `request.header.user-agent contains ${routerBuiltInAgentUserAgentNeedle(agent)}`,
@@ -859,7 +860,8 @@ export function buildBuiltInAgentRoutingRows(config: AppConfig): RoutingRuleRow[
       ruleId: `builtin-agent-${agent}`,
       sourceLabel: "Built-in",
       target: target ? `set request.body.model = ${target}` : "Profile model unset",
-      toggleDisabled: !profileEnabled || !target,
+      toggleDisabled: Boolean(toggleDisabledReason),
+      toggleDisabledReason,
       typeLabel: "Condition"
     };
   });
@@ -885,7 +887,22 @@ export function routerBuiltInAgentProfile(config: AppConfig, agent: RouterBuiltI
 }
 
 export function routerBuiltInAgentRouteTarget(config: AppConfig, agent: RouterBuiltInAgentRuleId): string {
-  return routerBuiltInAgentProfile(config, agent)?.model.trim() || config.Router.default?.trim() || "";
+  return routerBuiltInAgentProfile(config, agent)?.model.trim() || "";
+}
+
+export function routerBuiltInAgentRuleDisabledReason(config: AppConfig, agent: RouterBuiltInAgentRuleId): string | undefined {
+  if (config.profile.enabled === false) {
+    return "Agent profiles are disabled.";
+  }
+  const agentName = routerBuiltInAgentRuleName(agent);
+  const profile = routerBuiltInAgentProfile(config, agent);
+  if (!profile) {
+    return `Enable a ${agentName} profile before enabling this built-in route.`;
+  }
+  if (!profile.model.trim()) {
+    return `Set a model on the ${agentName} profile before enabling this built-in route.`;
+  }
+  return undefined;
 }
 
 export function routerBuiltInAgentRuleName(agent: RouterBuiltInAgentRuleId): string {
diff --git a/src/renderer/pages/home/shared/types.ts b/src/renderer/pages/home/shared/types.ts
index 9cbb4bc..2729e00 100644
--- a/src/renderer/pages/home/shared/types.ts
+++ b/src/renderer/pages/home/shared/types.ts
@@ -733,6 +733,7 @@ export type RoutingRuleRow = {
   sourceLabel: string;
   target: string;
   toggleDisabled?: boolean;
+  toggleDisabledReason?: string;
   typeLabel: string;
 };
 
diff --git a/src/server/gateway/claude-code-router-plugin.ts b/src/server/gateway/claude-code-router-plugin.ts
index d352db5..f809658 100644
--- a/src/server/gateway/claude-code-router-plugin.ts
+++ b/src/server/gateway/claude-code-router-plugin.ts
@@ -210,7 +210,7 @@ function resolveConfiguredRouteDecision(
     }
   }
 
-  return { fallback: router.fallback, model: normalizeRouteSelector(router.default) ?? explicitModel, reason: "default" };
+  return { fallback: router.fallback, model: explicitModel, reason: "default" };
 }
 
 function resolveBuiltInClaudeCodeSubagentRouteDecision(
@@ -287,8 +287,7 @@ function resolveBuiltInAgentProfile(config: AppConfig, agent: RouterBuiltInAgent
 }
 
 function resolveBuiltInAgentRouteTarget(config: AppConfig, agent: RouterBuiltInAgentRuleId): string | undefined {
-  return normalizeRouteSelector(resolveBuiltInAgentProfile(config, agent)?.model) ??
-    normalizeRouteSelector(config.Router.default);
+  return normalizeRouteSelector(resolveBuiltInAgentProfile(config, agent)?.model);
 }
 
 function builtInAgentUserAgentNeedle(agent: RouterBuiltInAgentRuleId): string {
diff --git a/src/shared/app.ts b/src/shared/app.ts
index 727599d..bc91702 100644
--- a/src/shared/app.ts
+++ b/src/shared/app.ts
@@ -532,7 +532,6 @@ export type RouterBuiltInRulesConfig = Record<RouterBuiltInAgentRuleId, RouterBu
 
 export type RouterConfig = {
   builtInRules: RouterBuiltInRulesConfig;
-  default?: string;
   fallback: RouterFallbackConfig;
   rules: RouterRule[];
 };
diff --git a/src/shared/claude-app-gateway.ts b/src/shared/claude-app-gateway.ts
index fff1a9c..c4127f7 100644
--- a/src/shared/claude-app-gateway.ts
+++ b/src/shared/claude-app-gateway.ts
@@ -25,14 +25,13 @@ export type ClaudeAppGatewayInferenceModel = {
   supports1m?: true;
 };
 
-export function inferClaudeAppGatewayTargetModel(config: Pick<AppConfig, "Router" | "profile">): string {
-  return config.Router.default?.trim() ||
-    inferGlobalClaudeProfileModel(config) ||
+export function inferClaudeAppGatewayTargetModel(config: Pick<AppConfig, "profile">): string {
+  return inferGlobalClaudeProfileModel(config) ||
     CLAUDE_APP_FALLBACK_MODEL;
 }
 
 export function buildClaudeAppGatewayModelRoutes(
-  config: Pick<AppConfig, "Providers" | "Router" | "profile" | "virtualModelProfiles">,
+  config: Pick<AppConfig, "Providers" | "profile" | "virtualModelProfiles">,
   options: ClaudeAppGatewayModelRouteOptions = {}
 ): ClaudeAppGatewayModelRoute[] {
   const targetModels = claudeAppGatewayTargetModels(config);
@@ -74,7 +73,7 @@ export function buildClaudeAppGatewayModelRoutes(
 
 export function resolveClaudeAppGatewayRouteModel(
   model: string,
-  config: Pick<AppConfig, "Providers" | "Router" | "profile" | "virtualModelProfiles">,
+  config: Pick<AppConfig, "Providers" | "profile" | "virtualModelProfiles">,
   options: ClaudeAppGatewayModelRouteOptions = {}
 ): string | undefined {
   const normalized = model.trim().toLowerCase();
@@ -99,7 +98,7 @@ export function resolveClaudeAppGatewayRouteModel(
 }
 
 export function buildClaudeAppGatewayInferenceModels(
-  config: Pick<AppConfig, "Providers" | "Router" | "profile" | "virtualModelProfiles">,
+  config: Pick<AppConfig, "Providers" | "profile" | "virtualModelProfiles">,
   options: ClaudeAppGatewayModelRouteOptions = {}
 ): ClaudeAppGatewayInferenceModel[] {
   const routes = buildClaudeAppGatewayModelRoutes(config, options);
@@ -129,7 +128,7 @@ function inferGlobalClaudeProfileModel(config: Pick<AppConfig, "profile">): stri
   )?.model.trim() ?? "";
 }
 
-function claudeAppGatewayTargetModels(config: Pick<AppConfig, "Providers" | "Router" | "profile" | "virtualModelProfiles">): string[] {
+function claudeAppGatewayTargetModels(config: Pick<AppConfig, "Providers" | "profile" | "virtualModelProfiles">): string[] {
   const baseEntries = config.Providers.flatMap((provider) => {
     const providerName = provider.name?.trim();
     if (!providerName || !Array.isArray(provider.models)) {
diff --git a/tests/main/router-builtins.test.mjs b/tests/main/router-builtins.test.mjs
index 747fe76..a01894a 100644
--- a/tests/main/router-builtins.test.mjs
+++ b/tests/main/router-builtins.test.mjs
@@ -20,7 +20,6 @@ function createRouterPlugin(options = {}) {
         "claude-code": { enabled: options.claudeCodeRuleEnabled ?? true },
         codex: { enabled: options.codexRuleEnabled ?? true }
       },
-      default: options.defaultModel ?? "",
       fallback: { mode: "off", models: [], retryCount: 1 },
       rules: []
     },
@@ -59,10 +58,9 @@ test("built-in Claude Code route matches user-agent case-insensitively", async (
   assert.equal(result.decision.reason, "builtin:claude-code");
 });
 
-test("built-in Codex route can use Router.default when profile model is unset", async () => {
+test("built-in Codex route stays inactive when profile model is unset", async () => {
   const plugin = createRouterPlugin({
-    agent: "codex",
-    defaultModel: "Provider/gpt-5-codex"
+    agent: "codex"
   });
   const result = await plugin.routeRequest({
     body: {
@@ -76,8 +74,8 @@ test("built-in Codex route can use Router.default when profile model is unset",
     url: "/v1/messages"
   });
 
-  assert.equal(result.body.model, "Provider/gpt-5-codex");
-  assert.equal(result.decision.reason, "builtin:codex");
+  assert.equal(result.body.model, "gpt-5");
+  assert.equal(result.decision.reason, "default");
 });
 
 test("built-in agent route stays off after the user disables it", async () => {
@@ -417,7 +415,7 @@ test("built-in Claude Code route removes only the first billing system array ite
 test("non-Claude-Code routes keep billing system prompts unchanged", async () => {
   const plugin = createRouterPlugin({
     agent: "codex",
-    defaultModel: "Provider/gpt-5-codex"
+    profileModel: "Provider/gpt-5-codex"
   });
   const result = await plugin.routeRequest({
     body: {