feat(ui): optimize MCP App widgets to reduce chat UI overhead

src/cli.ts

@@ -161,6 +161,7 @@ async function runInit({ force }: { force: boolean }): Promise<void> {
       port,
       allowedRoots,
       publicBaseUrl,
+      widgets: files.config.widgets ?? "off",
       subagents: resolveSubagentsFlag(files.config),
     };
     const auth = {
@@ -177,6 +178,7 @@ async function runInit({ force }: { force: boolean }): Promise<void> {
       ...seededSkillPaths.map((path) => `Default skill: ${path}`),
       `Local MCP URL: http://${config.host}:${config.port}/mcp`,
       ...(publicBaseUrl ? [`Public MCP URL: ${publicBaseUrl}/mcp`] : []),
+      `UI widgets: ${config.widgets} (owner setting)`,
     ];
     prompts.note(lines.join("\n"), "DevSpace configured");
     prompts.note(
@@ -219,6 +221,7 @@ async function serve(): Promise<void> {
     console.log(`public base url: ${config.publicBaseUrl}`);
     console.log(`allowed roots: ${config.allowedRoots.join(", ")}`);
     console.log(`allowed hosts: ${config.allowedHosts.join(", ")}`);
+    console.log(`widgets: ${config.widgets}`);
     if (config.allowedHosts.includes("*")) {
       console.warn("warning: Host header allowlist is disabled because DEVSPACE_ALLOWED_HOSTS=*");
     }
@@ -264,6 +267,7 @@ async function runDoctor(): Promise<void> {
     console.log(`Public MCP URL: ${new URL("/mcp", config.publicBaseUrl).toString()}`);
     console.log(`Allowed roots: ${config.allowedRoots.join(", ")}`);
     console.log(`Allowed hosts: ${config.allowedHosts.join(", ")}`);
+    console.log(`Widgets: ${config.widgets}`);
   } catch (error) {
     console.log(`Config status: ${error instanceof Error ? error.message : String(error)}`);
   }
@@ -281,20 +285,33 @@ function runConfigCommand(args: string[]): void {
   if (subcommand !== "set") {
     throw new Error(`Unknown config command: ${subcommand}`);
   }
-  if (key !== "publicBaseUrl") {
-    throw new Error("Only `devspace config set publicBaseUrl <url|null>` is supported right now.");
+  const value = rest.join(" ").trim();
+  if (key === "publicBaseUrl") {
+    if (!value) throw new Error("Missing publicBaseUrl value.");
+    writeDevspaceConfig({
+      ...files.config,
+      publicBaseUrl: normalizeOptionalPublicBaseUrl(value),
+    });
+    console.log(`Updated ${files.configPath}`);
+    return;
   }
 
-  const value = rest.join(" ").trim();
-  if (!value) {
-    throw new Error("Missing publicBaseUrl value.");
+  if (key === "widgets") {
+    if (value !== "off" && value !== "changes" && value !== "full") {
+      throw new Error("widgets must be one of: off, changes, full.");
+    }
+    writeDevspaceConfig({
+      ...files.config,
+      widgets: value,
+    });
+    console.log(`Updated ${files.configPath}`);
+    console.log("Restart DevSpace and refresh/reconnect the MCP App for the UI mode change to take effect.");
+    return;
   }
 
-  writeDevspaceConfig({
-    ...files.config,
-    publicBaseUrl: normalizeOptionalPublicBaseUrl(value),
-  });
-  console.log(`Updated ${files.configPath}`);
+  throw new Error(
+    "Supported settings: publicBaseUrl <url|null>, widgets <off|changes|full>.",
+  );
 }
 
 function printHelp(): void {
@@ -309,6 +326,7 @@ function printHelp(): void {
       "  devspace doctor          Show config, runtime, and native dependency status",
       "  devspace config get      Print persisted config",
       "  devspace config set publicBaseUrl <url|null>",
+      "  devspace config set widgets <off|changes|full>",
       "  devspace agents ls       List subagent sessions",
       "  devspace agents run <profile-or-provider-or-id> [--model <model>] <prompt>",
       "  devspace agents show <id>",

src/config.test.ts

@@ -12,7 +12,7 @@ const baseEnv = {
   DEVSPACE_OAUTH_OWNER_TOKEN: "test-owner-token-that-is-long-enough",
 };
 
-assert.equal(loadConfig(baseEnv).widgets, "full");
+assert.equal(loadConfig(baseEnv).widgets, "off");
 assert.equal(loadConfig({ ...baseEnv, DEVSPACE_WIDGETS: "changes" }).widgets, "changes");
 assert.equal(loadConfig({ ...baseEnv, DEVSPACE_WIDGETS: "full" }).widgets, "full");
 assert.equal(loadConfig({ ...baseEnv, DEVSPACE_WIDGETS: "off" }).widgets, "off");
@@ -162,6 +162,7 @@ writeFileSync(
     port: 8787,
     allowedRoots: [process.cwd()],
     publicBaseUrl: "https://devspace.example.com",
+    widgets: "changes",
     subagents: true,
   }),
 );
@@ -176,6 +177,11 @@ const fileConfig = loadConfig({ DEVSPACE_CONFIG_DIR: configDir });
 assert.equal(fileConfig.port, 8787);
 assert.equal(fileConfig.oauth.ownerToken, "persisted-owner-token-long-enough");
 assert.equal(fileConfig.publicBaseUrl, "https://devspace.example.com");
+assert.equal(fileConfig.widgets, "changes");
+assert.equal(
+  loadConfig({ DEVSPACE_CONFIG_DIR: configDir, DEVSPACE_WIDGETS: "full" }).widgets,
+  "full",
+);
 assert.equal(fileConfig.subagents, true);
 assert.deepEqual(fileConfig.allowedHosts, [
   "localhost",

src/config.ts

@@ -148,8 +148,8 @@ function parseLoggingConfig(env: NodeJS.ProcessEnv): LoggingConfig {
 }
 
 function parseWidgetMode(value: string | undefined): WidgetMode {
-  if (!value || value === "full") return "full";
-  if (value === "off" || value === "changes") return value;
+  if (!value || value === "off") return "off";
+  if (value === "changes" || value === "full") return value;
 
   throw new Error(`Invalid DEVSPACE_WIDGETS: ${value}`);
 }
@@ -223,7 +223,7 @@ export function loadConfig(env: NodeJS.ProcessEnv = process.env): ServerConfig {
     allowedHosts: parseAllowedHosts(env.DEVSPACE_ALLOWED_HOSTS, derivedAllowedHosts),
     publicBaseUrl,
     toolMode: parseToolMode(env),
-    widgets: parseWidgetMode(env.DEVSPACE_WIDGETS),
+    widgets: parseWidgetMode(env.DEVSPACE_WIDGETS ?? files.config.widgets),
     stateDir: resolve(expandHomePath(env.DEVSPACE_STATE_DIR ?? files.config.stateDir ?? defaultStateDir())),
     worktreeRoot: resolve(expandHomePath(env.DEVSPACE_WORKTREE_ROOT ?? files.config.worktreeRoot ?? defaultWorktreeRoot())),
     skillsEnabled: env.DEVSPACE_SKILLS === undefined ? true : parseBoolean(env.DEVSPACE_SKILLS),

src/server.ts

@@ -11,7 +11,7 @@ import { isInitializeRequest } from "@modelcontextprotocol/sdk/types.js";
 import { checkResourceAllowed, resourceUrlFromServerUrl } from "@modelcontextprotocol/sdk/shared/auth-utils.js";
 import {
   registerAppResource,
-  registerAppTool,
+  registerAppTool as registerUiTool,
   RESOURCE_MIME_TYPE,
 } from "@modelcontextprotocol/ext-apps/server";
 import express from "express";
@@ -155,6 +155,32 @@ function toolWidgetDescriptorMeta(
   };
 }
 
+const widgetModeByServer = new WeakMap<McpServer, WidgetMode>();
+
+function stripAppMeta<T>(value: T): T {
+  if (!value || typeof value !== "object") return value;
+  const { _meta: _discardedMeta, ...nativeValue } = value as Record<string, unknown>;
+  return nativeValue as T;
+}
+
+// Preserve the upstream MCP App path for changes/full, but use native
+// MCP tools in off mode so hosts do not allocate embedded UI cards.
+const registerAppTool = ((
+  server: McpServer,
+  name: string,
+  definition: any,
+  handler: (...args: any[]) => any,
+) => {
+  if (widgetModeByServer.get(server) !== "off") {
+    return registerUiTool(server, name, definition, handler);
+  }
+
+  return server.registerTool(
+    name,
+    stripAppMeta(definition),
+    async (...args: any[]) => stripAppMeta(await handler(...args)),
+  );
+}) as typeof registerUiTool;
 const toolNames = {
   openWorkspace: "open_workspace",
   read: "read",
@@ -701,8 +727,10 @@ function createMcpServer(
       instructions: serverInstructions(config),
     },
   );
+  widgetModeByServer.set(server, config.widgets);
 
-  registerAppResource(
+  if (config.widgets !== "off") {
+    registerAppResource(
     server,
     "DevSpace Diff Card",
     WORKSPACE_APP_URI,
@@ -732,6 +760,7 @@ function createMcpServer(
       };
     },
   );
+  }
 
   registerAppTool(
     server,

src/user-config.ts

@@ -14,6 +14,7 @@ export interface DevspaceUserConfig {
   port?: number;
   allowedRoots?: string[];
   publicBaseUrl?: string | null;
+  widgets?: "off" | "changes" | "full";
   allowedHosts?: string[];
   stateDir?: string;
   worktreeRoot?: string;