feat(webui): add context window setting

webui/src/components/settings/SettingsView.tsx

@@ -139,6 +139,7 @@ interface AgentSettingsDraft {
   provider: string;
   modelPreset: string;
   presetLabel: string;
+  contextWindowTokens: number;
   timezone: string;
   botName: string;
   botIcon: string;
@@ -164,6 +165,7 @@ type ProviderForm = { apiKey: string; apiBase: string; apiType: ProviderApiType
 type CustomMcpTransport = "stdio" | "streamableHttp" | "sse";
 
 const NANOBOT_ICON_SRC = "/brand/nanobot_icon.png";
+const CONTEXT_WINDOW_TOKEN_OPTIONS = [65_536, 262_144] as const;
 
 const FALLBACK_TIMEZONES = [
   "UTC",
@@ -279,6 +281,10 @@ function defaultPreset(payload: SettingsPayload): SettingsPayload["model_presets
   return payload.model_presets.find((preset) => preset.is_default) ?? null;
 }
 
+function normalizeContextWindowTokens(value: number | null | undefined): number {
+  return typeof value === "number" && Number.isFinite(value) && value > 0 ? value : 65_536;
+}
+
 function editableDefaultProvider(payload: SettingsPayload): string {
   const base = defaultPreset(payload);
   return base?.provider ?? payload.agent.provider ?? payload.agent.resolved_provider ?? "";
@@ -373,6 +379,7 @@ export function SettingsView({
     provider: "",
     modelPreset: "default",
     presetLabel: "Default",
+    contextWindowTokens: 65_536,
     timezone: "UTC",
     botName: "nanobot",
     botIcon: "",
@@ -398,6 +405,9 @@ export function SettingsView({
         : activePreset?.provider ?? editableDefaultProvider(payload),
       modelPreset: activePresetName,
       presetLabel: activePreset?.label ?? activePresetName,
+      contextWindowTokens: normalizeContextWindowTokens(
+        activePreset?.context_window_tokens ?? payload.agent.context_window_tokens,
+      ),
       timezone: payload.agent.timezone,
       botName: payload.agent.bot_name,
       botIcon: payload.agent.bot_icon,
@@ -533,6 +543,7 @@ export function SettingsView({
       form.modelPreset !== activePresetName ||
       form.model !== selectedPreset.model ||
       form.provider !== selectedProvider ||
+      form.contextWindowTokens !== normalizeContextWindowTokens(selectedPreset.context_window_tokens) ||
       (!selectedPreset.is_default && form.presetLabel.trim() !== selectedPreset.label)
     );
   }, [form, settings]);
@@ -644,14 +655,23 @@ export function SettingsView({
           label: form.presetLabel.trim(),
           model: form.model,
           provider: form.provider,
+          ...(form.contextWindowTokens !== selectedPreset.context_window_tokens
+            ? { contextWindowTokens: form.contextWindowTokens }
+            : {}),
         });
       } else {
         const defaultModel = defaultPreset(settings)?.model ?? settings.agent.model;
         const defaultProvider = editableDefaultProvider(settings);
+        const defaultContextWindowTokens = normalizeContextWindowTokens(
+          defaultPreset(settings)?.context_window_tokens ?? settings.agent.context_window_tokens,
+        );
         payload = await updateSettings(token, {
           modelPreset: form.modelPreset,
           ...(form.model !== defaultModel ? { model: form.model } : {}),
           ...(form.provider !== defaultProvider ? { provider: form.provider } : {}),
+          ...(form.contextWindowTokens !== defaultContextWindowTokens
+            ? { contextWindowTokens: form.contextWindowTokens }
+            : {}),
         });
       }
       applyPayload(payload);
@@ -1876,6 +1896,9 @@ function ModelsSettings({
                     ? editableDefaultProvider(settings)
                     : nextPreset?.provider ?? prev.provider,
                   presetLabel: nextPreset?.label ?? modelPreset,
+                  contextWindowTokens: normalizeContextWindowTokens(
+                    nextPreset?.context_window_tokens ?? prev.contextWindowTokens,
+                  ),
                 }));
               }}
               onCreateConfiguration={onCreateConfiguration}
@@ -1895,49 +1918,73 @@ function ModelsSettings({
               />
             </SettingsRow>
           ) : null}
-              <SettingsRow
-                title={t("settings.rows.provider")}
-                description={t("settings.help.provider")}
+          <SettingsRow
+            title={t("settings.rows.provider")}
+            description={t("settings.help.provider")}
+          >
+            <ProviderPicker
+              providers={providerOptions}
+              value={providerValue}
+              emptyLabel={t("settings.byok.noConfiguredProviders")}
+              showProviderLogos={showBrandLogos}
+              onChange={(provider) => setForm((prev) => ({ ...prev, provider }))}
+            />
+          </SettingsRow>
+          {selectedProviderNeedsSignIn ? (
+            <SettingsRow
+              title={tx("settings.oauth.signInRequired", "Sign in required")}
+              description={tx(
+                "settings.oauth.signInBeforeSaving",
+                "Sign in before saving this OAuth provider as the active model provider.",
+              )}
+            >
+              <Button
+                size="sm"
+                variant="outline"
+                onClick={() => selectedProvider && onProviderOAuthLogin(selectedProvider.name)}
+                disabled={!selectedProvider?.oauth_login_supported || selectedProviderSigningIn}
+                className="rounded-full"
               >
-                <ProviderPicker
-                  providers={providerOptions}
-                  value={providerValue}
-                  emptyLabel={t("settings.byok.noConfiguredProviders")}
-                  showProviderLogos={showBrandLogos}
-                  onChange={(provider) => setForm((prev) => ({ ...prev, provider }))}
-                />
-              </SettingsRow>
-              {selectedProviderNeedsSignIn ? (
-                <SettingsRow
-                  title={tx("settings.oauth.signInRequired", "Sign in required")}
-                  description={tx("settings.oauth.signInBeforeSaving", "Sign in before saving this OAuth provider as the active model provider.")}
-                >
-                  <Button
-                    size="sm"
-                    variant="outline"
-                    onClick={() => selectedProvider && onProviderOAuthLogin(selectedProvider.name)}
-                    disabled={!selectedProvider?.oauth_login_supported || selectedProviderSigningIn}
-                    className="rounded-full"
-                  >
-                    {selectedProviderSigningIn ? (
-                      <Loader2 className="mr-1.5 h-3.5 w-3.5 animate-spin" aria-hidden />
-                    ) : null}
-                    {selectedProviderSigningIn
-                      ? tx("settings.oauth.signingIn", "Signing in...")
-                      : tx("settings.oauth.signIn", "Sign in")}
-                  </Button>
-                </SettingsRow>
-              ) : null}
-              <SettingsRow
-                title={t("settings.rows.model")}
-                description={t("settings.help.model")}
-              >
-                <Input
-                  value={form.model}
-                  onChange={(event) => setForm((prev) => ({ ...prev, model: event.target.value }))}
-                  className="h-8 w-[min(280px,70vw)] rounded-full text-[13px]"
-                />
-              </SettingsRow>
+                {selectedProviderSigningIn ? (
+                  <Loader2 className="mr-1.5 h-3.5 w-3.5 animate-spin" aria-hidden />
+                ) : null}
+                {selectedProviderSigningIn
+                  ? tx("settings.oauth.signingIn", "Signing in...")
+                  : tx("settings.oauth.signIn", "Sign in")}
+              </Button>
+            </SettingsRow>
+          ) : null}
+          <SettingsRow
+            title={t("settings.rows.model")}
+            description={t("settings.help.model")}
+          >
+            <Input
+              value={form.model}
+              onChange={(event) => setForm((prev) => ({ ...prev, model: event.target.value }))}
+              className="h-8 w-[min(280px,70vw)] rounded-full text-[13px]"
+            />
+          </SettingsRow>
+          <SettingsRow
+            title={tx("settings.rows.contextWindow", "Context window")}
+            description={tx(
+              "settings.help.contextWindow",
+              "Choose the default context budget for this model configuration.",
+            )}
+          >
+            <SegmentedControl
+              value={String(form.contextWindowTokens)}
+              options={CONTEXT_WINDOW_TOKEN_OPTIONS.map((tokens) => ({
+                value: String(tokens),
+                label: tokens === 262_144 ? "256K" : "64K",
+              }))}
+              onChange={(value) =>
+                setForm((prev) => ({
+                  ...prev,
+                  contextWindowTokens: normalizeContextWindowTokens(Number(value)),
+                }))
+              }
+            />
+          </SettingsRow>
           <SettingsFooter
             dirty={dirty}
             saving={saving}

webui/src/i18n/locales/en/common.json

@@ -146,7 +146,8 @@
       "cliAppsFilter": "Filter",
       "engine": "Engine",
       "logs": "Logs",
-      "diagnostics": "Diagnostics"
+      "diagnostics": "Diagnostics",
+      "contextWindow": "Context window"
     },
     "help": {
       "theme": "Switch between light and dark appearance.",
@@ -184,7 +185,8 @@
       "logs": "Open the native engine log folder.",
       "diagnostics": "Export a small runtime report for support.",
       "localServiceAccessNative": "Allow Full Access shell commands to reach services on this Mac.",
-      "webuiDefaultAccessNative": "Used by native chats without a project-specific permission."
+      "webuiDefaultAccessNative": "Used by native chats without a project-specific permission.",
+      "contextWindow": "Choose the default context budget for this model configuration."
     },
     "timezone": {
       "select": "Select timezone",

webui/src/i18n/locales/es/common.json

@@ -137,7 +137,8 @@
       "cliAppsFilter": "Filtro de apps CLI",
       "engine": "Motor",
       "logs": "Registros",
-      "diagnostics": "Diagnóstico"
+      "diagnostics": "Diagnóstico",
+      "contextWindow": "Context window"
     },
     "help": {
       "theme": "Cambia entre apariencia clara y oscura.",
@@ -175,7 +176,8 @@
       "logs": "Abre la carpeta de registros del motor de escritorio.",
       "diagnostics": "Exporta un pequeño informe de runtime para soporte.",
       "localServiceAccessNative": "Allow Full Access shell commands to reach services on this Mac.",
-      "webuiDefaultAccessNative": "Used by native chats without a project-specific permission."
+      "webuiDefaultAccessNative": "Used by native chats without a project-specific permission.",
+      "contextWindow": "Choose the default context budget for this model configuration."
     },
     "values": {
       "light": "Claro",

webui/src/i18n/locales/fr/common.json

@@ -137,7 +137,8 @@
       "cliAppsFilter": "Filtre des apps CLI",
       "engine": "Moteur",
       "logs": "Journaux",
-      "diagnostics": "Diagnostics"
+      "diagnostics": "Diagnostics",
+      "contextWindow": "Context window"
     },
     "help": {
       "theme": "Basculer entre les apparences claire et sombre.",
@@ -175,7 +176,8 @@
       "logs": "Ouvrir le dossier des journaux du moteur natif.",
       "diagnostics": "Exporter un petit rapport runtime pour le support.",
       "localServiceAccessNative": "Allow Full Access shell commands to reach services on this Mac.",
-      "webuiDefaultAccessNative": "Used by native chats without a project-specific permission."
+      "webuiDefaultAccessNative": "Used by native chats without a project-specific permission.",
+      "contextWindow": "Choose the default context budget for this model configuration."
     },
     "values": {
       "light": "Clair",

webui/src/i18n/locales/id/common.json

@@ -137,7 +137,8 @@
       "cliAppsFilter": "Filter aplikasi CLI",
       "engine": "Engine",
       "logs": "Log",
-      "diagnostics": "Diagnostik"
+      "diagnostics": "Diagnostik",
+      "contextWindow": "Context window"
     },
     "help": {
       "theme": "Beralih antara tampilan terang dan gelap.",
@@ -175,7 +176,8 @@
       "logs": "Buka folder log native engine.",
       "diagnostics": "Ekspor laporan runtime kecil untuk dukungan.",
       "localServiceAccessNative": "Allow Full Access shell commands to reach services on this Mac.",
-      "webuiDefaultAccessNative": "Used by native chats without a project-specific permission."
+      "webuiDefaultAccessNative": "Used by native chats without a project-specific permission.",
+      "contextWindow": "Choose the default context budget for this model configuration."
     },
     "values": {
       "light": "Terang",

webui/src/i18n/locales/ja/common.json

@@ -137,7 +137,8 @@
       "cliAppsFilter": "CLI アプリフィルター",
       "engine": "エンジン",
       "logs": "ログ",
-      "diagnostics": "診断"
+      "diagnostics": "診断",
+      "contextWindow": "Context window"
     },
     "help": {
       "theme": "ライト表示とダーク表示を切り替えます。",
@@ -175,7 +176,8 @@
       "logs": "Appエンジンのログフォルダを開きます。",
       "diagnostics": "サポート用の小さなランタイムレポートを書き出します。",
       "localServiceAccessNative": "Allow Full Access shell commands to reach services on this Mac.",
-      "webuiDefaultAccessNative": "Used by native chats without a project-specific permission."
+      "webuiDefaultAccessNative": "Used by native chats without a project-specific permission.",
+      "contextWindow": "Choose the default context budget for this model configuration."
     },
     "values": {
       "light": "ライト",

webui/src/i18n/locales/ko/common.json

@@ -137,7 +137,8 @@
       "cliAppsFilter": "CLI 앱 필터",
       "engine": "엔진",
       "logs": "로그",
-      "diagnostics": "진단"
+      "diagnostics": "진단",
+      "contextWindow": "Context window"
     },
     "help": {
       "theme": "밝은 모드와 어두운 모드를 전환합니다.",
@@ -175,7 +176,8 @@
       "logs": "App 엔진 로그 폴더를 엽니다.",
       "diagnostics": "지원용 작은 런타임 보고서를 내보냅니다.",
       "localServiceAccessNative": "Allow Full Access shell commands to reach services on this Mac.",
-      "webuiDefaultAccessNative": "Used by native chats without a project-specific permission."
+      "webuiDefaultAccessNative": "Used by native chats without a project-specific permission.",
+      "contextWindow": "Choose the default context budget for this model configuration."
     },
     "values": {
       "light": "라이트",

webui/src/i18n/locales/vi/common.json

@@ -137,7 +137,8 @@
       "cliAppsFilter": "Bộ lọc ứng dụng CLI",
       "engine": "Engine",
       "logs": "Nhật ký",
-      "diagnostics": "Chẩn đoán"
+      "diagnostics": "Chẩn đoán",
+      "contextWindow": "Context window"
     },
     "help": {
       "theme": "Chuyển giữa giao diện sáng và tối.",
@@ -175,7 +176,8 @@
       "logs": "Mở thư mục nhật ký native engine.",
       "diagnostics": "Xuất báo cáo runtime nhỏ để hỗ trợ.",
       "localServiceAccessNative": "Allow Full Access shell commands to reach services on this Mac.",
-      "webuiDefaultAccessNative": "Used by native chats without a project-specific permission."
+      "webuiDefaultAccessNative": "Used by native chats without a project-specific permission.",
+      "contextWindow": "Choose the default context budget for this model configuration."
     },
     "values": {
       "light": "Sáng",

webui/src/i18n/locales/zh-CN/common.json

@@ -146,7 +146,8 @@
       "cliAppsFilter": "筛选",
       "engine": "引擎",
       "logs": "日志",
-      "diagnostics": "诊断"
+      "diagnostics": "诊断",
+      "contextWindow": "上下文窗口"
     },
     "help": {
       "theme": "在浅色和深色外观之间切换。",
@@ -184,7 +185,8 @@
       "logs": "打开App引擎日志文件夹。",
       "diagnostics": "导出一份用于支持排查的运行时报告。",
       "localServiceAccessNative": "允许完全访问模式下的 shell 命令访问这台 Mac 上的服务。",
-      "webuiDefaultAccessNative": "用于没有单独选择权限的原生 App 对话。"
+      "webuiDefaultAccessNative": "用于没有单独选择权限的原生 App 对话。",
+      "contextWindow": "选择这个模型配置默认使用的上下文预算。"
     },
     "timezone": {
       "select": "选择时区",

webui/src/i18n/locales/zh-TW/common.json

@@ -137,7 +137,8 @@
       "cliAppsFilter": "CLI 應用篩選",
       "engine": "引擎",
       "logs": "日誌",
-      "diagnostics": "診斷"
+      "diagnostics": "診斷",
+      "contextWindow": "上下文視窗"
     },
     "help": {
       "theme": "在淺色與深色外觀之間切換。",
@@ -175,7 +176,8 @@
       "logs": "開啟App引擎日誌資料夾。",
       "diagnostics": "匯出一份供支援排查用的執行階段報告。",
       "localServiceAccessNative": "允許完全存取模式下的 shell 命令存取這台 Mac 上的服務。",
-      "webuiDefaultAccessNative": "用於沒有單獨選擇權限的原生 App 對話。"
+      "webuiDefaultAccessNative": "用於沒有單獨選擇權限的原生 App 對話。",
+      "contextWindow": "選擇這個模型設定預設使用的上下文預算。"
     },
     "values": {
       "light": "淺色",

webui/src/lib/api.ts

@@ -280,6 +280,9 @@ export async function updateSettings(
   }
   if (update.model !== undefined) query.set("model", update.model);
   if (update.provider !== undefined) query.set("provider", update.provider);
+  if (update.contextWindowTokens !== undefined) {
+    query.set("context_window_tokens", String(update.contextWindowTokens));
+  }
   if (update.timezone !== undefined) query.set("timezone", update.timezone);
   if (update.botName !== undefined) query.set("bot_name", update.botName);
   if (update.botIcon !== undefined) query.set("bot_icon", update.botIcon);
@@ -315,6 +318,9 @@ export async function updateModelConfiguration(
   if (configuration.label !== undefined) query.set("label", configuration.label);
   if (configuration.provider !== undefined) query.set("provider", configuration.provider);
   if (configuration.model !== undefined) query.set("model", configuration.model);
+  if (configuration.contextWindowTokens !== undefined) {
+    query.set("context_window_tokens", String(configuration.contextWindowTokens));
+  }
   return request<SettingsPayload>(
     `${base}/api/settings/model-configurations/update?${query}`,
     token,

webui/src/lib/types.ts

@@ -517,6 +517,7 @@ export interface SettingsUpdate {
   model?: string;
   provider?: string;
   modelPreset?: string | null;
+  contextWindowTokens?: number;
   timezone?: string;
   botName?: string;
   botIcon?: string;
@@ -535,6 +536,7 @@ export interface ModelConfigurationUpdate {
   label?: string;
   provider?: string;
   model?: string;
+  contextWindowTokens?: number;
 }
 
 export interface ProviderSettingsUpdate {

webui/src/tests/api.test.ts

@@ -65,6 +65,7 @@ describe("webui API helpers", () => {
       modelPreset: "default",
       model: "openrouter/test",
       provider: "openrouter",
+      contextWindowTokens: 262144,
       timezone: "Asia/Shanghai",
       botName: "nanobot",
       botIcon: "nb",
@@ -72,7 +73,7 @@ describe("webui API helpers", () => {
     });
 
     expect(fetch).toHaveBeenCalledWith(
-      "/api/settings/update?model_preset=default&model=openrouter%2Ftest&provider=openrouter&timezone=Asia%2FShanghai&bot_name=nanobot&bot_icon=nb&tool_hint_max_length=120",
+      "/api/settings/update?model_preset=default&model=openrouter%2Ftest&provider=openrouter&context_window_tokens=262144&timezone=Asia%2FShanghai&bot_name=nanobot&bot_icon=nb&tool_hint_max_length=120",
       expect.objectContaining({
         headers: { Authorization: "Bearer tok" },
       }),
@@ -100,10 +101,11 @@ describe("webui API helpers", () => {
       label: "Codex",
       provider: "openai_codex",
       model: "openai-codex/gpt-5.5",
+      contextWindowTokens: 65536,
     });
 
     expect(fetch).toHaveBeenCalledWith(
-      "/api/settings/model-configurations/update?name=codex&label=Codex&provider=openai_codex&model=openai-codex%2Fgpt-5.5",
+      "/api/settings/model-configurations/update?name=codex&label=Codex&provider=openai_codex&model=openai-codex%2Fgpt-5.5&context_window_tokens=65536",
       expect.objectContaining({
         headers: { Authorization: "Bearer tok" },
       }),

webui/src/tests/settings-view.test.tsx

@@ -121,7 +121,7 @@ const installedAnyGen = {
 
 function renderSettingsView(
   options: {
-    initialSection?: "apps" | "advanced";
+    initialSection?: "apps" | "advanced" | "models";
     onSettingsChange?: (payload: SettingsPayload) => void;
   } = {},
 ) {
@@ -222,6 +222,29 @@ describe("SettingsView Apps catalog", () => {
     await waitFor(() => expect(onSettingsChange).toHaveBeenCalledWith(payload));
   });
 
+  it("shows context window options in model settings", async () => {
+    vi.stubGlobal(
+      "fetch",
+      vi.fn(async (input: RequestInfo | URL) => {
+        const url = String(input);
+        if (url === "/api/settings") return jsonResponse(settingsPayload());
+        if (url === "/api/settings/cli-apps") {
+          return jsonResponse({ apps: [], installed_count: 0 });
+        }
+        if (url === "/api/settings/mcp-presets") {
+          return jsonResponse({ presets: [], installed_count: 0 });
+        }
+        return { ok: false, status: 404, json: async () => ({}) } as Response;
+      }),
+    );
+
+    renderSettingsView({ initialSection: "models" });
+
+    expect(await screen.findByText("Context window")).toBeInTheDocument();
+    expect(screen.getByRole("button", { name: "64K" })).toBeInTheDocument();
+    expect(screen.getByRole("button", { name: "256K" })).toBeInTheDocument();
+  });
+
   it("saves network safety without exposing technical SSRF copy", async () => {
     const payload = settingsPayload();
     const fetchMock = vi.fn(async (input: RequestInfo | URL) => {