diff --git a/tests/commands.test.mjs b/tests/commands.test.mjs
index 809fdff..62bea9b 100644
--- a/tests/commands.test.mjs
+++ b/tests/commands.test.mjs
@@ -4,7 +4,7 @@ import test from "node:test";
 import assert from "node:assert/strict";
 import { fileURLToPath } from "node:url";
 
-const ROOT = path.resolve(fileURLToPath(new URL("..", import.meta.url)));
+const ROOT = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..");
 const PLUGIN_ROOT = path.join(ROOT, "plugins", "codex");
 
 function read(relativePath) {
diff --git a/tests/fake-codex-fixture.mjs b/tests/fake-codex-fixture.mjs
index ac7f084..a85fd31 100644
--- a/tests/fake-codex-fixture.mjs
+++ b/tests/fake-codex-fixture.mjs
@@ -1,4 +1,6 @@
+import fs from "node:fs";
 import path from "node:path";
+import process from "node:process";
 
 import { writeExecutable } from "./helpers.mjs";
 
@@ -507,11 +509,19 @@ rl.on("line", (line) => {
 });
 `;
   writeExecutable(scriptPath, source);
+
+  // On Windows, npm global binaries are invoked via .cmd wrappers.
+  // Create a codex.cmd so the fake binary is discoverable by spawn with shell: true.
+  if (process.platform === "win32") {
+    const cmdWrapper = `@echo off\r\nnode "%~dp0codex" %*\r\n`;
+    fs.writeFileSync(path.join(binDir, "codex.cmd"), cmdWrapper, { encoding: "utf8" });
+  }
 }
 
 export function buildEnv(binDir) {
+  const sep = process.platform === "win32" ? ";" : ":";
   return {
     ...process.env,
-    PATH: `${binDir}:${process.env.PATH}`
+    PATH: `${binDir}${sep}${process.env.PATH}`
   };
 }
diff --git a/tests/helpers.mjs b/tests/helpers.mjs
index 799fe3c..945ae0e 100644
--- a/tests/helpers.mjs
+++ b/tests/helpers.mjs
@@ -1,6 +1,7 @@
 import fs from "node:fs";
 import os from "node:os";
 import path from "node:path";
+import process from "node:process";
 import { spawnSync } from "node:child_process";
 
 export function makeTempDir(prefix = "codex-plugin-test-") {
@@ -16,7 +17,9 @@ export function run(command, args, options = {}) {
     cwd: options.cwd,
     env: options.env,
     encoding: "utf8",
-    input: options.input
+    input: options.input,
+    shell: process.platform === "win32" && !path.isAbsolute(command),
+    windowsHide: true
   });
 }
 
diff --git a/tests/runtime.test.mjs b/tests/runtime.test.mjs
index 15f96c5..56ba6c1 100644
--- a/tests/runtime.test.mjs
+++ b/tests/runtime.test.mjs
@@ -10,7 +10,7 @@ import { initGitRepo, makeTempDir, run } from "./helpers.mjs";
 import { loadBrokerSession } from "../plugins/codex/scripts/lib/broker-lifecycle.mjs";
 import { resolveStateDir } from "../plugins/codex/scripts/lib/state.mjs";
 
-const ROOT = path.resolve(fileURLToPath(new URL("..", import.meta.url)));
+const ROOT = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..");
 const PLUGIN_ROOT = path.join(ROOT, "plugins", "codex");
 const SCRIPT = path.join(PLUGIN_ROOT, "scripts", "codex-companion.mjs");
 const STOP_HOOK = path.join(PLUGIN_ROOT, "scripts", "stop-review-gate-hook.mjs");