fix: spawn cursor-agent with shell mode on Windows (model discovery falls back to static list)

src/cli/model-discovery.ts

@@ -31,10 +31,23 @@ export function parseCursorModelsOutput(output: string): DiscoveredModel[] {
   return models;
 }
 
-export function discoverModelsFromCursorAgent(): DiscoveredModel[] {
-  const raw = execFileSync(resolveCursorAgentBinary(), ["models"], {
+export type DiscoverDeps = {
+  platform?: NodeJS.Platform;
+  execFileSync?: typeof execFileSync;
+  resolveBinary?: () => string;
+};
+
+export function discoverModelsFromCursorAgent(deps: DiscoverDeps = {}): DiscoveredModel[] {
+  const platform = deps.platform ?? process.platform;
+  const exec = deps.execFileSync ?? execFileSync;
+  const resolveBinary = deps.resolveBinary ?? resolveCursorAgentBinary;
+
+  // On Windows cursor-agent is a .cmd shim, which requires shell mode when
+  // spawned from Node (execFileSync of a bare .cmd fails with EINVAL).
+  const raw = exec(resolveBinary(), ["models"], {
     encoding: "utf8",
-    ...(process.platform !== "win32" && { killSignal: "SIGTERM" as const }),
+    shell: platform === "win32",
+    ...(platform !== "win32" && { killSignal: "SIGTERM" as const }),
     stdio: ["ignore", "pipe", "pipe"],
     timeout: MODEL_DISCOVERY_TIMEOUT_MS,
   });

src/cli/opencode-cursor.ts

@@ -116,7 +116,10 @@ export function checkBun(): CheckResult {
 
 export function checkCursorAgent(): CheckResult {
   try {
-    const output = execFileSync(resolveCursorAgentBinary(), ["--version"], { encoding: "utf8" }).trim();
+    const output = execFileSync(resolveCursorAgentBinary(), ["--version"], {
+      encoding: "utf8",
+      shell: process.platform === "win32",
+    }).trim();
     const version = output.split("\n")[0] || "installed";
     return { name: "cursor-agent", passed: true, message: version };
   } catch {
@@ -134,6 +137,7 @@ export function checkCursorAgentLogin(): CheckResult {
     // Try running a command that requires auth
     execFileSync(resolveCursorAgentBinary(), ["models"], {
       encoding: "utf8",
+      shell: process.platform === "win32",
       stdio: ["ignore", "pipe", "pipe"],
       timeout: 3000,
     });

tests/unit/cli/model-discovery.test.ts

@@ -1,5 +1,8 @@
 import { describe, expect, it } from "bun:test";
-import { parseCursorModelsOutput } from "../../../src/cli/model-discovery.js";
+import {
+  discoverModelsFromCursorAgent,
+  parseCursorModelsOutput,
+} from "../../../src/cli/model-discovery.js";
 
 describe("cli/model-discovery", () => {
   it("parses model ids and names from cursor-agent output", () => {
@@ -28,3 +31,42 @@ auto - Auto
     expect(models).toEqual([{ id: "auto", name: "Auto" }]);
   });
 });
+
+describe("cli/model-discovery discoverModelsFromCursorAgent", () => {
+  it("runs cursor-agent with shell mode on Windows", () => {
+    const calls: Array<{ cmd: string; args: string[]; opts: any }> = [];
+    const exec = (cmd: string, args: string[], opts: any) => {
+      calls.push({ cmd, args, opts });
+      return "auto - Auto\n";
+    };
+
+    const models = discoverModelsFromCursorAgent({
+      platform: "win32",
+      execFileSync: exec as any,
+      resolveBinary: () => "C:\\cursor-agent\\cursor-agent.cmd",
+    });
+
+    expect(models).toEqual([{ id: "auto", name: "Auto" }]);
+    expect(calls).toHaveLength(1);
+    expect(calls[0].cmd).toBe("C:\\cursor-agent\\cursor-agent.cmd");
+    expect(calls[0].args).toEqual(["models"]);
+    expect(calls[0].opts.shell).toBe(true);
+  });
+
+  it("does not use shell mode on non-Windows platforms", () => {
+    const calls: Array<{ cmd: string; args: string[]; opts: any }> = [];
+    const exec = (cmd: string, args: string[], opts: any) => {
+      calls.push({ cmd, args, opts });
+      return "auto - Auto\n";
+    };
+
+    discoverModelsFromCursorAgent({
+      platform: "linux",
+      execFileSync: exec as any,
+      resolveBinary: () => "/usr/local/bin/cursor-agent",
+    });
+
+    expect(calls[0].opts.shell).toBe(false);
+    expect(calls[0].opts.killSignal).toBe("SIGTERM");
+  });
+});