diff --git a/tests/unit/backends/nativeToolRuntime.test.ts b/tests/unit/backends/nativeToolRuntime.test.ts
new file mode 100644
index 00000000..bc152a68
--- /dev/null
+++ b/tests/unit/backends/nativeToolRuntime.test.ts
@@ -0,0 +1,165 @@
+import { constants, accessSync, existsSync, readFileSync } from 'node:fs';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+import {
+	buildNativeToolPath,
+	createNativeToolRuntimeArtifacts,
+} from '../../../src/backends/nativeToolRuntime.js';
+
+describe('createNativeToolRuntimeArtifacts', () => {
+	// Track artifacts created in each test so we can clean up even if the test fails
+	let cleanupFns: Array<() => void> = [];
+
+	afterEach(() => {
+		for (const cleanup of cleanupFns) {
+			try {
+				cleanup();
+			} catch {
+				// ignore cleanup errors in afterEach
+			}
+		}
+		cleanupFns = [];
+		vi.restoreAllMocks();
+	});
+
+	it('creates a shim directory that exists on disk', () => {
+		const { shimDir, cleanup } = createNativeToolRuntimeArtifacts();
+		cleanupFns.push(cleanup);
+
+		expect(existsSync(shimDir)).toBe(true);
+	});
+
+	it('creates a gh shim file inside the shim directory', () => {
+		const { shimDir, cleanup } = createNativeToolRuntimeArtifacts();
+		cleanupFns.push(cleanup);
+
+		const ghPath = `${shimDir}/gh`;
+		expect(existsSync(ghPath)).toBe(true);
+	});
+
+	it('gh shim is a valid shell script with the expected content', () => {
+		const { shimDir, cleanup } = createNativeToolRuntimeArtifacts();
+		cleanupFns.push(cleanup);
+
+		const ghPath = `${shimDir}/gh`;
+		const content = readFileSync(ghPath, 'utf-8');
+
+		expect(content).toContain('#!/bin/sh');
+		expect(content).toContain('cascade-tools');
+		expect(content).toContain('exit 1');
+	});
+
+	it('gh shim has executable permissions (0o755)', () => {
+		const { shimDir, cleanup } = createNativeToolRuntimeArtifacts();
+		cleanupFns.push(cleanup);
+
+		const ghPath = `${shimDir}/gh`;
+		// accessSync throws if the permission check fails; we assert it doesn't throw
+		expect(() => accessSync(ghPath, constants.X_OK)).not.toThrow();
+	});
+
+	it('cleanup removes the shim directory best-effort', () => {
+		const { shimDir, cleanup } = createNativeToolRuntimeArtifacts();
+
+		// Directory must exist before cleanup
+		expect(existsSync(shimDir)).toBe(true);
+
+		cleanup();
+
+		// Directory should be gone after cleanup
+		expect(existsSync(shimDir)).toBe(false);
+	});
+
+	it('cleanup does not throw even if the directory was already removed', () => {
+		const { shimDir, cleanup } = createNativeToolRuntimeArtifacts();
+		cleanupFns.push(cleanup);
+
+		// Remove the directory manually first
+		cleanup();
+
+		// Calling cleanup again (after removal) should not throw
+		expect(() => cleanup()).not.toThrow();
+	});
+
+	it('generates unique shim directories on each call', () => {
+		// Use fake timers so Date.now() advances between the two calls
+		vi.useFakeTimers();
+
+		const first = createNativeToolRuntimeArtifacts();
+		cleanupFns.push(first.cleanup);
+
+		vi.advanceTimersByTime(1);
+
+		const second = createNativeToolRuntimeArtifacts();
+		cleanupFns.push(second.cleanup);
+
+		vi.useRealTimers();
+
+		expect(first.shimDir).not.toBe(second.shimDir);
+	});
+});
+
+describe('buildNativeToolPath', () => {
+	it('places shim directory first in the resulting PATH', () => {
+		const result = buildNativeToolPath('/usr/bin', '/opt/cascade-tools', '/tmp/shims');
+
+		const parts = result.split(':');
+		expect(parts[0]).toBe('/tmp/shims');
+	});
+
+	it('places cliToolsDir before basePath', () => {
+		const result = buildNativeToolPath('/usr/bin', '/opt/cascade-tools', '/tmp/shims');
+
+		const parts = result.split(':');
+		const cliIdx = parts.indexOf('/opt/cascade-tools');
+		const baseIdx = parts.indexOf('/usr/bin');
+
+		expect(cliIdx).toBeGreaterThanOrEqual(0);
+		expect(baseIdx).toBeGreaterThanOrEqual(0);
+		expect(cliIdx).toBeLessThan(baseIdx);
+	});
+
+	it('preserves basePath at the end', () => {
+		const result = buildNativeToolPath('/usr/bin:/usr/local/bin', '/opt/cascade-tools');
+
+		expect(result).toContain('/usr/bin:/usr/local/bin');
+		expect(result.endsWith('/usr/bin:/usr/local/bin')).toBe(true);
+	});
+
+	it('omits shimDir from PATH when not provided', () => {
+		const result = buildNativeToolPath('/usr/bin', '/opt/cascade-tools');
+
+		const parts = result.split(':');
+		expect(parts).toHaveLength(2);
+		expect(parts).toContain('/opt/cascade-tools');
+		expect(parts).toContain('/usr/bin');
+	});
+
+	it('includes cliToolsDir even without shimDir or basePath', () => {
+		const result = buildNativeToolPath(undefined, '/opt/cascade-tools');
+
+		expect(result).toBe('/opt/cascade-tools');
+	});
+
+	it('filters out empty string entries', () => {
+		const result = buildNativeToolPath('', '/opt/cascade-tools', '');
+
+		const parts = result.split(':');
+		expect(parts).not.toContain('');
+		expect(parts).toHaveLength(1);
+	});
+
+	it('filters out undefined basePath', () => {
+		const result = buildNativeToolPath(undefined, '/opt/cascade-tools', '/tmp/shims');
+
+		const parts = result.split(':');
+		expect(parts).not.toContain('undefined');
+		expect(parts).toEqual(['/tmp/shims', '/opt/cascade-tools']);
+	});
+
+	it('returns correct shim-first ordering with all three entries', () => {
+		const result = buildNativeToolPath('/usr/bin', '/opt/cascade-tools', '/tmp/shims');
+
+		expect(result).toBe('/tmp/shims:/opt/cascade-tools:/usr/bin');
+	});
+});