fix(windows): quote shell args with spaces

packages/server/src/server/agent/provider-launch-config.test.ts

@@ -2,6 +2,7 @@ import { afterEach, beforeEach, describe, expect, test, vi } from "vitest";
 
 import {
   findExecutable,
+  quoteWindowsArgument,
   quoteWindowsCommand,
   resolveProviderCommandPrefix,
   applyProviderEnv,
@@ -255,3 +256,39 @@ describe("quoteWindowsCommand", () => {
     expect(quoteWindowsCommand("/usr/local/bin/claude code")).toBe("/usr/local/bin/claude code");
   });
 });
+
+describe("quoteWindowsArgument", () => {
+  const originalPlatform = process.platform;
+
+  function setPlatform(value: string) {
+    Object.defineProperty(process, "platform", { value, writable: true });
+  }
+
+  afterEach(() => {
+    setPlatform(originalPlatform);
+  });
+
+  test("quotes a Windows argument with spaces", () => {
+    setPlatform("win32");
+    expect(quoteWindowsArgument("C:\\Program Files\\Anthropic\\cli.js")).toBe(
+      '"C:\\Program Files\\Anthropic\\cli.js"',
+    );
+  });
+
+  test("does not double-quote an already-quoted argument", () => {
+    setPlatform("win32");
+    expect(quoteWindowsArgument('"C:\\Program Files\\Anthropic\\cli.js"')).toBe(
+      '"C:\\Program Files\\Anthropic\\cli.js"',
+    );
+  });
+
+  test("returns the argument unchanged when there are no spaces", () => {
+    setPlatform("win32");
+    expect(quoteWindowsArgument("--version")).toBe("--version");
+  });
+
+  test("returns the argument unchanged on non-Windows platforms", () => {
+    setPlatform("darwin");
+    expect(quoteWindowsArgument("/usr/local/bin/claude code")).toBe("/usr/local/bin/claude code");
+  });
+});

packages/server/src/server/agent/provider-launch-config.ts

@@ -286,6 +286,18 @@ export function quoteWindowsCommand(command: string): string {
   return `"${command}"`;
 }
 
+/**
+ * `spawn(..., { shell: true })` on Windows also passes argv through `cmd.exe`.
+ * Any argument containing spaces must be quoted or it will be split before the
+ * child process sees it.
+ */
+export function quoteWindowsArgument(argument: string): string {
+  if (process.platform !== "win32") return argument;
+  if (!argument.includes(" ")) return argument;
+  if (argument.startsWith('"') && argument.endsWith('"')) return argument;
+  return `"${argument}"`;
+}
+
 export function isCommandAvailable(command: string): boolean {
   return findExecutable(command) !== null;
 }

packages/server/src/server/agent/providers/claude-agent.ts

@@ -70,6 +70,7 @@ import type {
 import {
   applyProviderEnv,
   findExecutable,
+  quoteWindowsArgument,
   quoteWindowsCommand,
   type ProviderRuntimeSettings,
 } from "../provider-launch-config.js";
@@ -214,7 +215,10 @@ function applyRuntimeSettingsToClaudeOptions(
       const isDefaultRuntime =
         resolved.command === "node" || resolved.command === "bun";
       const command = isDefaultRuntime ? process.execPath : resolved.command;
-      const child = spawn(quoteWindowsCommand(command), resolved.args, {
+      const child = spawn(
+        quoteWindowsCommand(command),
+        resolved.args.map((argument) => quoteWindowsArgument(argument)),
+        {
         cwd: spawnOptions.cwd,
         env: {
           ...applyProviderEnv(spawnOptions.env, runtimeSettings),
@@ -223,7 +227,8 @@ function applyRuntimeSettingsToClaudeOptions(
         shell: process.platform === "win32",
         signal: spawnOptions.signal,
         stdio: ["pipe", "pipe", "pipe"],
-      });
+        },
+      );
       if (typeof options.stderr === "function") {
         child.stderr?.on("data", (chunk: Buffer | string) => {
           options.stderr?.(chunk.toString());

packages/server/src/server/agent/providers/codex-app-server-agent.ts

@@ -42,6 +42,7 @@ import {
 import {
   applyProviderEnv,
   findExecutable,
+  quoteWindowsArgument,
   quoteWindowsCommand,
   resolveProviderCommandPrefix,
   type ProviderRuntimeSettings,
@@ -3420,12 +3421,16 @@ export class CodexAppServerAgentClient implements AgentClient {
       },
       "Spawning Codex app server",
     );
-    return spawn(quoteWindowsCommand(launchPrefix.command), [...launchPrefix.args, "app-server"], {
-      detached: process.platform !== "win32",
-      shell: process.platform === "win32",
-      stdio: ["pipe", "pipe", "pipe"],
-      env: buildCodexAppServerEnv(this.runtimeSettings, launchEnv),
-    });
+    return spawn(
+      quoteWindowsCommand(launchPrefix.command),
+      [...launchPrefix.args, "app-server"].map((argument) => quoteWindowsArgument(argument)),
+      {
+        detached: process.platform !== "win32",
+        shell: process.platform === "win32",
+        stdio: ["pipe", "pipe", "pipe"],
+        env: buildCodexAppServerEnv(this.runtimeSettings, launchEnv),
+      },
+    );
   }
 
   async createSession(

packages/server/src/server/agent/providers/opencode-agent.ts

@@ -32,6 +32,7 @@ import type {
 import {
   applyProviderEnv,
   findExecutable,
+  quoteWindowsArgument,
   quoteWindowsCommand,
   resolveProviderCommandPrefix,
   type ProviderRuntimeSettings,
@@ -335,7 +336,9 @@ export class OpenCodeServerManager {
     return new Promise((resolve, reject) => {
       this.server = spawn(
         quoteWindowsCommand(launchPrefix.command),
-        [...launchPrefix.args, "serve", "--port", String(this.port)],
+        [...launchPrefix.args, "serve", "--port", String(this.port)].map((argument) =>
+          quoteWindowsArgument(argument),
+        ),
         {
           shell: process.platform === "win32",
           stdio: ["ignore", "pipe", "pipe"],

packages/server/src/server/exports.ts

@@ -33,6 +33,7 @@ export {
 export {
   findExecutable,
   applyProviderEnv,
+  quoteWindowsArgument,
   quoteWindowsCommand,
 } from "./agent/provider-launch-config.js";