diff --git a/packages/desktop/scripts/dev-build-contract.test.mjs b/packages/desktop/scripts/dev-build-contract.test.mjs
index 7c6994a64e..f9b3a34b0d 100644
--- a/packages/desktop/scripts/dev-build-contract.test.mjs
+++ b/packages/desktop/scripts/dev-build-contract.test.mjs
@@ -19,9 +19,17 @@ import { describe, expect, test } from "vitest";
 const desktopDir = path.resolve(import.meta.dirname, "..");
 const repoRoot = path.resolve(desktopDir, "../..");
 const execFileAsync = promisify(execFile);
-const npmCommand = process.platform === "win32" ? "npm.cmd" : "npm";
+const npmCommand = process.platform === "win32" ? process.execPath : "npm";
+const npmPrefixArgs =
+  process.platform === "win32" ? [requireEnvironmentVariable("npm_execpath")] : [];
 const prerequisite = "npm run dev:prerequisites";
 
+function requireEnvironmentVariable(name) {
+  const value = process.env[name];
+  if (!value) throw new Error(`${name} is required to invoke npm on Windows`);
+  return value;
+}
+
 describe("desktop dev build contract", () => {
   test("runs one prerequisite before either platform dev entry point", async () => {
     const packageJson = JSON.parse(await readFile(path.join(desktopDir, "package.json"), "utf8"));
@@ -127,10 +135,14 @@ async function createIsolatedBuildCheckout() {
 
 async function runPrerequisite(isolatedRoot) {
   try {
-    await execFileAsync(npmCommand, ["run", "dev:prerequisites", "--workspace=@getpaseo/desktop"], {
-      cwd: isolatedRoot,
-      timeout: 60_000,
-    });
+    await execFileAsync(
+      npmCommand,
+      [...npmPrefixArgs, "run", "dev:prerequisites", "--workspace=@getpaseo/desktop"],
+      {
+        cwd: isolatedRoot,
+        timeout: 60_000,
+      },
+    );
   } catch (error) {
     throw new Error(`${error.stdout ?? ""}\n${error.stderr ?? ""}`, { cause: error });
   }
diff --git a/packages/workspace-helper/test/standalone.test.mjs b/packages/workspace-helper/test/standalone.test.mjs
index 655ebb97f5..14e6def7a6 100644
--- a/packages/workspace-helper/test/standalone.test.mjs
+++ b/packages/workspace-helper/test/standalone.test.mjs
@@ -7,19 +7,31 @@ import assert from "node:assert/strict";
 import { promisify } from "node:util";
 
 const run = promisify(execFile);
-const npmCommand = process.platform === "win32" ? "npm.cmd" : "npm";
+const npmCommand = process.platform === "win32" ? process.execPath : "npm";
+const npmPrefixArgs =
+  process.platform === "win32" ? [requireEnvironmentVariable("npm_execpath")] : [];
 const packageRoot = path.resolve(import.meta.dirname, "..");
 
+function requireEnvironmentVariable(name) {
+  const value = process.env[name];
+  if (!value) throw new Error(`${name} is required to invoke npm on Windows`);
+  return value;
+}
+
+function runNpm(args, options) {
+  return run(npmCommand, [...npmPrefixArgs, ...args], options);
+}
+
 test("packed helper works from a fresh project without monorepo source fallback", async (t) => {
   const root = await mkdtemp(path.join(tmpdir(), "paseo-helper-standalone-"));
   t.after(() => rm(root, { recursive: true, force: true }));
   const packDirectory = path.join(root, "packs");
   const project = path.join(root, "project");
   await Promise.all([mkdir(packDirectory), mkdir(project)]);
-  await run(npmCommand, ["run", "build"], { cwd: packageRoot });
+  await runNpm(["run", "build"], { cwd: packageRoot });
   const packed = JSON.parse(
     (
-      await run(npmCommand, ["pack", "--json", "--pack-destination", packDirectory], {
+      await runNpm(["pack", "--json", "--pack-destination", packDirectory], {
         cwd: packageRoot,
       })
     ).stdout,
@@ -31,7 +43,7 @@ test("packed helper works from a fresh project without monorepo source fallback"
       dependencies: { "@getpaseo/workspace-helper": `file:${path.join(packDirectory, packed)}` },
     }),
   );
-  await run(npmCommand, ["install", "--ignore-scripts"], { cwd: project });
+  await runNpm(["install", "--ignore-scripts"], { cwd: project });
   await writeFile(path.join(project, "notes.txt"), "before\n");
 
   const imported = JSON.parse(
diff --git a/packages/workspace-runtime-contract/test/contract.test.mjs b/packages/workspace-runtime-contract/test/contract.test.mjs
index da50e41de3..fb222d0d92 100644
--- a/packages/workspace-runtime-contract/test/contract.test.mjs
+++ b/packages/workspace-runtime-contract/test/contract.test.mjs
@@ -33,10 +33,22 @@ import {
 } from "../dist/index.js";
 
 const run = promisify(execFile);
-const npmCommand = process.platform === "win32" ? "npm.cmd" : "npm";
+const npmCommand = process.platform === "win32" ? process.execPath : "npm";
+const npmPrefixArgs =
+  process.platform === "win32" ? [requireEnvironmentVariable("npm_execpath")] : [];
 const packageRoot = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..");
 const examples = JSON.parse(await readFile(path.join(packageRoot, "examples/v1.json"), "utf8"));
 
+function requireEnvironmentVariable(name) {
+  const value = process.env[name];
+  if (!value) throw new Error(`${name} is required to invoke npm on Windows`);
+  return value;
+}
+
+function runNpm(args, options) {
+  return run(npmCommand, [...npmPrefixArgs, ...args], options);
+}
+
 test("documented lifecycle, fd3, control, and fd4 examples are exact newline-terminated bytes", () => {
   for (const [name, schema] of [
     ["describeResponse", CommandRuntimeDescribeResponseSchema],
@@ -522,7 +534,7 @@ test("every export condition resolves from a packed standalone install", async (
   t.after(() => rm(root, { recursive: true, force: true }));
   const pack = JSON.parse(
     (
-      await run(npmCommand, ["pack", "--json", "--ignore-scripts", "--pack-destination", root], {
+      await runNpm(["pack", "--json", "--ignore-scripts", "--pack-destination", root], {
         cwd: packageRoot,
       })
     ).stdout,
@@ -530,7 +542,7 @@ test("every export condition resolves from a packed standalone install", async (
   const archive = path.join(root, pack[0].filename);
   const installRoot = path.join(root, "standalone");
   await mkdir(installRoot);
-  await run(npmCommand, ["install", "--ignore-scripts", "--no-package-lock", archive], {
+  await runNpm(["install", "--ignore-scripts", "--no-package-lock", archive], {
     cwd: installRoot,
   });
   const installed = path.join(installRoot, "node_modules/@getpaseo/workspace-runtime-contract");