add support for GROK.md custom instructions

README.md

@@ -65,6 +65,27 @@ Or specify a working directory:
 grok -d /path/to/project
 ```
 
+### Custom Instructions
+
+You can provide custom instructions to tailor Grok's behavior to your project by creating a `.grok/GROK.md` file in your project directory:
+
+```bash
+mkdir .grok
+```
+
+Create `.grok/GROK.md` with your custom instructions:
+```markdown
+# Custom Instructions for Grok CLI
+
+Always use TypeScript for any new code files.
+When creating React components, use functional components with hooks.
+Prefer const assertions and explicit typing over inference where it improves clarity.
+Always add JSDoc comments for public functions and interfaces.
+Follow the existing code style and patterns in this project.
+```
+
+Grok will automatically load and follow these instructions when working in your project directory. The custom instructions are added to Grok's system prompt and take priority over default behavior.
+
 ## Example Conversations
 
 Instead of typing commands, just tell Grok what you want to do:

src/agent/grok-agent.ts

@@ -4,6 +4,7 @@ import { TextEditorTool, BashTool, TodoTool, ConfirmationTool } from '../tools';
 import { ToolResult } from '../types';
 import { EventEmitter } from 'events';
 import { createTokenCounter, TokenCounter } from '../utils/token-counter';
+import { loadCustomInstructions } from '../utils/custom-instructions';
 
 export interface ChatEntry {
   type: 'user' | 'assistant' | 'tool_result';
@@ -43,10 +44,16 @@ export class GrokAgent extends EventEmitter {
     this.confirmationTool = new ConfirmationTool();
     this.tokenCounter = createTokenCounter('grok-4-latest');
     
+    // Load custom instructions
+    const customInstructions = loadCustomInstructions();
+    const customInstructionsSection = customInstructions 
+      ? `\n\nCUSTOM INSTRUCTIONS:\n${customInstructions}\n\nThe above custom instructions should be followed alongside the standard instructions below.`
+      : '';
+    
     // Initialize with system message
     this.messages.push({
       role: 'system',
-      content: `You are Grok CLI, an AI assistant that helps with file editing, coding tasks, and system operations. 
+      content: `You are Grok CLI, an AI assistant that helps with file editing, coding tasks, and system operations.${customInstructionsSection}
 
 You have access to these tools:
 - view_file: View file contents or directory listings

src/utils/custom-instructions.ts

@@ -0,0 +1,18 @@
+import * as fs from 'fs';
+import * as path from 'path';
+
+export function loadCustomInstructions(workingDirectory: string = process.cwd()): string | null {
+  try {
+    const instructionsPath = path.join(workingDirectory, '.grok', 'GROK.md');
+    
+    if (!fs.existsSync(instructionsPath)) {
+      return null;
+    }
+
+    const customInstructions = fs.readFileSync(instructionsPath, 'utf-8');
+    return customInstructions.trim();
+  } catch (error) {
+    console.warn('Failed to load custom instructions:', error);
+    return null;
+  }
+}