feat: add global system prompt override support

- Users can now define global system prompts in ~/.roo/system-prompt-{mode}
- Local project prompts still take precedence over global ones
- Updated tests to cover the new functionality
- Fixes #6813

Author: roomote

src/core/prompts/sections/__tests__/custom-system-prompt.spec.ts

@@ -1,16 +1,19 @@
 // Mocks must come first, before imports
 
 vi.mock("fs/promises")
+vi.mock("os")
 
 // Then imports
 import type { Mock } from "vitest"
 import path from "path"
+import os from "os"
 import { readFile } from "fs/promises"
 import type { Mode } from "../../../../shared/modes" // Type-only import
-import { loadSystemPromptFile, PromptVariables } from "../custom-system-prompt"
+import { loadSystemPromptFile, PromptVariables, getGlobalSystemPromptFilePath } from "../custom-system-prompt"
 
 // Cast the mocked readFile to the correct Mock type
 const mockedReadFile = readFile as Mock<typeof readFile>
+const mockedHomedir = os.homedir as Mock<typeof os.homedir>
 
 describe("loadSystemPromptFile", () => {
 	// Corrected PromptVariables type and added mockMode
@@ -19,15 +22,18 @@ describe("loadSystemPromptFile", () => {
 	}
 	const mockCwd = "/mock/cwd"
 	const mockMode: Mode = "test" // Use Mode type, e.g., 'test'
+	const mockHomeDir = "/home/user"
 	// Corrected expected file path format
-	const expectedFilePath = path.join(mockCwd, ".roo", `system-prompt-${mockMode}`)
+	const expectedLocalFilePath = path.join(mockCwd, ".roo", `system-prompt-${mockMode}`)
+	const expectedGlobalFilePath = path.join(mockHomeDir, ".roo", `system-prompt-${mockMode}`)
 
 	beforeEach(() => {
 		// Clear mocks before each test
 		mockedReadFile.mockClear()
+		mockedHomedir.mockReturnValue(mockHomeDir)
 	})
 
-	it("should return an empty string if the file does not exist (ENOENT)", async () => {
+	it("should return an empty string if neither local nor global file exists (ENOENT)", async () => {
 		const error: NodeJS.ErrnoException = new Error("File not found")
 		error.code = "ENOENT"
 		mockedReadFile.mockRejectedValue(error)
@@ -36,8 +42,9 @@ describe("loadSystemPromptFile", () => {
 		const result = await loadSystemPromptFile(mockCwd, mockMode, mockVariables)
 
 		expect(result).toBe("")
-		expect(mockedReadFile).toHaveBeenCalledTimes(1)
-		expect(mockedReadFile).toHaveBeenCalledWith(expectedFilePath, "utf-8")
+		expect(mockedReadFile).toHaveBeenCalledTimes(2)
+		expect(mockedReadFile).toHaveBeenCalledWith(expectedLocalFilePath, "utf-8")
+		expect(mockedReadFile).toHaveBeenCalledWith(expectedGlobalFilePath, "utf-8")
 	})
 
 	// Updated test: should re-throw unexpected errors
@@ -50,18 +57,23 @@ describe("loadSystemPromptFile", () => {
 
 		// Verify readFile was still called correctly
 		expect(mockedReadFile).toHaveBeenCalledTimes(1)
-		expect(mockedReadFile).toHaveBeenCalledWith(expectedFilePath, "utf-8")
+		expect(mockedReadFile).toHaveBeenCalledWith(expectedLocalFilePath, "utf-8")
 	})
 
-	it("should return an empty string if the file content is empty", async () => {
-		mockedReadFile.mockResolvedValue("")
+	it("should return an empty string if the local file content is empty and check global", async () => {
+		const error: NodeJS.ErrnoException = new Error("File not found")
+		error.code = "ENOENT"
+
+		// Local file is empty, global file doesn't exist
+		mockedReadFile.mockResolvedValueOnce("").mockRejectedValueOnce(error)
 
 		// Added mockMode argument
 		const result = await loadSystemPromptFile(mockCwd, mockMode, mockVariables)
 
 		expect(result).toBe("")
-		expect(mockedReadFile).toHaveBeenCalledTimes(1)
-		expect(mockedReadFile).toHaveBeenCalledWith(expectedFilePath, "utf-8")
+		expect(mockedReadFile).toHaveBeenCalledTimes(2)
+		expect(mockedReadFile).toHaveBeenNthCalledWith(1, expectedLocalFilePath, "utf-8")
+		expect(mockedReadFile).toHaveBeenNthCalledWith(2, expectedGlobalFilePath, "utf-8")
 	})
 
 	// Updated test to only check workspace interpolation
@@ -74,7 +86,7 @@ describe("loadSystemPromptFile", () => {
 
 		expect(result).toBe("Workspace is: /path/to/workspace")
 		expect(mockedReadFile).toHaveBeenCalledTimes(1)
-		expect(mockedReadFile).toHaveBeenCalledWith(expectedFilePath, "utf-8")
+		expect(mockedReadFile).toHaveBeenCalledWith(expectedLocalFilePath, "utf-8")
 	})
 
 	// Updated test for multiple occurrences of workspace
@@ -87,7 +99,7 @@ describe("loadSystemPromptFile", () => {
 
 		expect(result).toBe("Path: /path/to/workspace//path/to/workspace")
 		expect(mockedReadFile).toHaveBeenCalledTimes(1)
-		expect(mockedReadFile).toHaveBeenCalledWith(expectedFilePath, "utf-8")
+		expect(mockedReadFile).toHaveBeenCalledWith(expectedLocalFilePath, "utf-8")
 	})
 
 	// Updated test for mixed used/unused
@@ -101,7 +113,7 @@ describe("loadSystemPromptFile", () => {
 		// Unused variables should remain untouched
 		expect(result).toBe("Workspace: /path/to/workspace, Unused: {{unusedVar}}, Another: {{another}}")
 		expect(mockedReadFile).toHaveBeenCalledTimes(1)
-		expect(mockedReadFile).toHaveBeenCalledWith(expectedFilePath, "utf-8")
+		expect(mockedReadFile).toHaveBeenCalledWith(expectedLocalFilePath, "utf-8")
 	})
 
 	// Test remains valid, just needs the mode argument and updated template
@@ -114,7 +126,7 @@ describe("loadSystemPromptFile", () => {
 
 		expect(result).toBe("Workspace: /path/to/workspace, Missing: {{missingPlaceholder}}")
 		expect(mockedReadFile).toHaveBeenCalledTimes(1)
-		expect(mockedReadFile).toHaveBeenCalledWith(expectedFilePath, "utf-8")
+		expect(mockedReadFile).toHaveBeenCalledWith(expectedLocalFilePath, "utf-8")
 	})
 
 	// Removed the test for extra keys as PromptVariables is simple now
@@ -129,6 +141,39 @@ describe("loadSystemPromptFile", () => {
 
 		expect(result).toBe("This is a static prompt.")
 		expect(mockedReadFile).toHaveBeenCalledTimes(1)
-		expect(mockedReadFile).toHaveBeenCalledWith(expectedFilePath, "utf-8")
+		expect(mockedReadFile).toHaveBeenCalledWith(expectedLocalFilePath, "utf-8")
+	})
+
+	it("should use global system prompt when local file doesn't exist", async () => {
+		const error: NodeJS.ErrnoException = new Error("File not found")
+		error.code = "ENOENT"
+		const globalTemplate = "Global system prompt: {{workspace}}"
+
+		// First call (local) fails, second call (global) succeeds
+		mockedReadFile.mockRejectedValueOnce(error).mockResolvedValueOnce(globalTemplate)
+
+		const result = await loadSystemPromptFile(mockCwd, mockMode, mockVariables)
+
+		expect(result).toBe("Global system prompt: /path/to/workspace")
+		expect(mockedReadFile).toHaveBeenCalledTimes(2)
+		expect(mockedReadFile).toHaveBeenNthCalledWith(1, expectedLocalFilePath, "utf-8")
+		expect(mockedReadFile).toHaveBeenNthCalledWith(2, expectedGlobalFilePath, "utf-8")
+	})
+
+	it("should prefer local system prompt over global when both exist", async () => {
+		const localTemplate = "Local system prompt: {{workspace}}"
+		mockedReadFile.mockResolvedValueOnce(localTemplate)
+
+		const result = await loadSystemPromptFile(mockCwd, mockMode, mockVariables)
+
+		expect(result).toBe("Local system prompt: /path/to/workspace")
+		// Should only read the local file, not the global one
+		expect(mockedReadFile).toHaveBeenCalledTimes(1)
+		expect(mockedReadFile).toHaveBeenCalledWith(expectedLocalFilePath, "utf-8")
+	})
+
+	it("should correctly generate global system prompt file path", () => {
+		const result = getGlobalSystemPromptFilePath(mockMode)
+		expect(result).toBe(expectedGlobalFilePath)
 	})
 })

src/core/prompts/sections/custom-system-prompt.ts

@@ -1,5 +1,6 @@
 import fs from "fs/promises"
 import path from "path"
+import os from "os"
 import { Mode } from "../../../shared/modes"
 import { fileExistsAtPath } from "../../../utils/fs"
 
@@ -50,15 +51,34 @@ export function getSystemPromptFilePath(cwd: string, mode: Mode): string {
 }
 
 /**
- * Loads custom system prompt from a file at .roo/system-prompt-[mode slug]
- * If the file doesn't exist, returns an empty string
+ * Get the path to a global system prompt file for a specific mode
+ * Located in the user's home directory under .roo/system-prompt-[mode slug]
+ */
+export function getGlobalSystemPromptFilePath(mode: Mode): string {
+	return path.join(os.homedir(), ".roo", `system-prompt-${mode}`)
+}
+
+/**
+ * Loads custom system prompt from a file, checking in the following order:
+ * 1. Local project: .roo/system-prompt-[mode slug]
+ * 2. Global (home directory): ~/.roo/system-prompt-[mode slug]
+ * If neither file exists, returns an empty string
  */
 export async function loadSystemPromptFile(cwd: string, mode: Mode, variables: PromptVariables): Promise<string> {
-	const filePath = getSystemPromptFilePath(cwd, mode)
-	const rawContent = await safeReadFile(filePath)
+	// First, check for local project-specific system prompt
+	const localFilePath = getSystemPromptFilePath(cwd, mode)
+	let rawContent = await safeReadFile(localFilePath)
+
+	// If no local file exists, check for global system prompt
+	if (!rawContent) {
+		const globalFilePath = getGlobalSystemPromptFilePath(mode)
+		rawContent = await safeReadFile(globalFilePath)
+	}
+
 	if (!rawContent) {
 		return ""
 	}
+
 	const interpolatedContent = interpolatePromptContent(rawContent, variables)
 	return interpolatedContent
 }

src/core/webview/ClineProvider.ts

@@ -78,7 +78,7 @@ import { ContextProxy } from "../config/ContextProxy"
 import { ProviderSettingsManager } from "../config/ProviderSettingsManager"
 import { CustomModesManager } from "../config/CustomModesManager"
 import { Task, TaskOptions } from "../task/Task"
-import { getSystemPromptFilePath } from "../prompts/sections/custom-system-prompt"
+import { getSystemPromptFilePath, getGlobalSystemPromptFilePath } from "../prompts/sections/custom-system-prompt"
 
 import { webviewMessageHandler } from "./webviewMessageHandler"
 import { getNonce } from "./getNonce"
@@ -1480,10 +1480,18 @@ export class ClineProvider
 
 	/**
 	 * Checks if there is a file-based system prompt override for the given mode
+	 * Checks both local project directory and global home directory
 	 */
 	async hasFileBasedSystemPromptOverride(mode: Mode): Promise<boolean> {
-		const promptFilePath = getSystemPromptFilePath(this.cwd, mode)
-		return await fileExistsAtPath(promptFilePath)
+		// Check local project directory first
+		const localPromptFilePath = getSystemPromptFilePath(this.cwd, mode)
+		if (await fileExistsAtPath(localPromptFilePath)) {
+			return true
+		}
+
+		// Check global home directory
+		const globalPromptFilePath = getGlobalSystemPromptFilePath(mode)
+		return await fileExistsAtPath(globalPromptFilePath)
 	}
 
 	/**