diff --git a/src/utils/__tests__/storage.spec.ts b/src/utils/__tests__/storage.spec.ts
new file mode 100644
index 0000000000..5cc99895b3
--- /dev/null
+++ b/src/utils/__tests__/storage.spec.ts
@@ -0,0 +1,177 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest"
+import * as vscode from "vscode"
+import * as fs from "fs/promises"
+import * as path from "path"
+import { getStorageBasePath } from "../storage"
+
+// Mock vscode module
+vi.mock("vscode", () => ({
+	workspace: {
+		getConfiguration: vi.fn(),
+	},
+	window: {
+		showErrorMessage: vi.fn(),
+	},
+}))
+
+// Mock fs/promises module
+vi.mock("fs/promises", () => ({
+	mkdir: vi.fn(),
+	writeFile: vi.fn(),
+	rm: vi.fn(),
+}))
+
+describe("storage", () => {
+	const mockFs = fs as any
+	const mockVscode = vscode as any
+
+	beforeEach(() => {
+		vi.clearAllMocks()
+	})
+
+	afterEach(() => {
+		vi.restoreAllMocks()
+	})
+
+	describe("getStorageBasePath", () => {
+		const defaultPath = "/default/storage/path"
+
+		it("should return default path when no custom path is configured", async () => {
+			mockVscode.workspace.getConfiguration.mockReturnValue({
+				get: vi.fn().mockReturnValue(""),
+			})
+
+			const result = await getStorageBasePath(defaultPath)
+			expect(result).toBe(defaultPath)
+		})
+
+		it("should return default path when vscode configuration is not accessible", async () => {
+			mockVscode.workspace.getConfiguration.mockImplementation(() => {
+				throw new Error("VSCode not available")
+			})
+
+			const consoleSpy = vi.spyOn(console, "warn").mockImplementation(() => {})
+			const result = await getStorageBasePath(defaultPath)
+
+			expect(result).toBe(defaultPath)
+			expect(consoleSpy).toHaveBeenCalledWith("Could not access VSCode configuration - using default path")
+
+			consoleSpy.mockRestore()
+		})
+
+		it("should return custom path when it is writable", async () => {
+			const customPath = "/custom/storage/path"
+
+			mockVscode.workspace.getConfiguration.mockReturnValue({
+				get: vi.fn().mockReturnValue(customPath),
+			})
+
+			mockFs.mkdir.mockResolvedValue(undefined)
+			mockFs.writeFile.mockResolvedValue(undefined)
+			mockFs.rm.mockResolvedValue(undefined)
+
+			const result = await getStorageBasePath(defaultPath)
+
+			expect(result).toBe(customPath)
+			expect(mockFs.mkdir).toHaveBeenCalledWith(customPath, { recursive: true })
+			expect(mockFs.writeFile).toHaveBeenCalledWith(
+				expect.stringMatching(/\.write_test_\d+_\d+_[a-z0-9]+$/),
+				"test",
+			)
+			expect(mockFs.rm).toHaveBeenCalledWith(expect.stringMatching(/\.write_test_\d+_\d+_[a-z0-9]+$/))
+		})
+
+		it("should return default path when custom path is not writable", async () => {
+			const customPath = "/custom/storage/path"
+
+			mockVscode.workspace.getConfiguration.mockReturnValue({
+				get: vi.fn().mockReturnValue(customPath),
+			})
+
+			mockFs.mkdir.mockResolvedValue(undefined)
+			mockFs.writeFile.mockRejectedValue(new Error("Permission denied"))
+
+			const consoleSpy = vi.spyOn(console, "error").mockImplementation(() => {})
+			const result = await getStorageBasePath(defaultPath)
+
+			expect(result).toBe(defaultPath)
+			expect(consoleSpy).toHaveBeenCalledWith(expect.stringContaining("Custom storage path is unusable"))
+			expect(mockVscode.window.showErrorMessage).toHaveBeenCalled()
+
+			consoleSpy.mockRestore()
+		})
+
+		it("should handle concurrent calls without race conditions", async () => {
+			const customPath = "/custom/storage/path"
+
+			mockVscode.workspace.getConfiguration.mockReturnValue({
+				get: vi.fn().mockReturnValue(customPath),
+			})
+
+			mockFs.mkdir.mockResolvedValue(undefined)
+			mockFs.writeFile.mockResolvedValue(undefined)
+			mockFs.rm.mockResolvedValue(undefined)
+
+			// Simulate multiple concurrent calls
+			const promises = Array.from({ length: 10 }, () => getStorageBasePath(defaultPath))
+			const results = await Promise.all(promises)
+
+			// All should return the custom path
+			results.forEach((result) => {
+				expect(result).toBe(customPath)
+			})
+
+			// Check that each call used a unique test file
+			const writeFileCalls = mockFs.writeFile.mock.calls
+			const testFilePaths = writeFileCalls.map((call: any[]) => call[0])
+			const uniquePaths = new Set(testFilePaths)
+
+			// Each concurrent call should have used a unique test file
+			expect(uniquePaths.size).toBe(10)
+
+			// All test files should have unique suffixes
+			testFilePaths.forEach((filePath: string) => {
+				expect(filePath).toMatch(/\.write_test_\d+_\d+_[a-z0-9]+$/)
+			})
+		})
+
+		it("should use unique test file names with process ID, timestamp, and random suffix", async () => {
+			const customPath = "/custom/storage/path"
+
+			mockVscode.workspace.getConfiguration.mockReturnValue({
+				get: vi.fn().mockReturnValue(customPath),
+			})
+
+			mockFs.mkdir.mockResolvedValue(undefined)
+			mockFs.writeFile.mockResolvedValue(undefined)
+			mockFs.rm.mockResolvedValue(undefined)
+
+			const processId = process.pid
+			const beforeTime = Date.now()
+
+			await getStorageBasePath(defaultPath)
+
+			const afterTime = Date.now()
+
+			const writeFileCall = mockFs.writeFile.mock.calls[0]
+			const testFilePath = writeFileCall[0]
+
+			// Extract the suffix from the test file path
+			const match = testFilePath.match(/\.write_test_(\d+)_(\d+)_([a-z0-9]+)$/)
+			expect(match).toBeTruthy()
+
+			const [, pid, timestamp, random] = match
+
+			// Verify process ID
+			expect(parseInt(pid)).toBe(processId)
+
+			// Verify timestamp is within expected range
+			const ts = parseInt(timestamp)
+			expect(ts).toBeGreaterThanOrEqual(beforeTime)
+			expect(ts).toBeLessThanOrEqual(afterTime)
+
+			// Verify random suffix format
+			expect(random).toMatch(/^[a-z0-9]{7}$/)
+		})
+	})
+})
diff --git a/src/utils/storage.ts b/src/utils/storage.ts
index 8240588794..360e7fe636 100644
--- a/src/utils/storage.ts
+++ b/src/utils/storage.ts
@@ -33,7 +33,9 @@ export async function getStorageBasePath(defaultPath: string): Promise<string> {
 		await fs.mkdir(customStoragePath, { recursive: true })
 
 		// Test if path is writable
-		const testFile = path.join(customStoragePath, ".write_test")
+		// Use unique suffix to prevent race conditions when multiple instances run simultaneously
+		const uniqueSuffix = `${process.pid}_${Date.now()}_${Math.random().toString(36).substring(2, 9)}`
+		const testFile = path.join(customStoragePath, `.write_test_${uniqueSuffix}`)
 		await fs.writeFile(testFile, "test")
 		await fs.rm(testFile)