diff --git a/vscode-extension/src/monitors/pasteMonitor.ts b/vscode-extension/src/monitors/pasteMonitor.ts
new file mode 100644
index 0000000..8ddcaa9
--- /dev/null
+++ b/vscode-extension/src/monitors/pasteMonitor.ts
@@ -0,0 +1,64 @@
+import * as vscode from 'vscode';
+
+interface PasteEvent {
+    timestamp: number;
+    size: number;
+    content: string;
+    source?: 'clipboard' | 'external';
+}
+
+export class PasteMonitor {
+    private pastes: PasteEvent[] = [];
+    private readonly LARGE_PASTE_THRESHOLD = 100; // lines
+    
+    constructor() {
+        vscode.workspace.onDidChangeTextDocument(this.detectPaste, this);
+    }
+    
+    private detectPaste(event: vscode.TextDocumentChangeEvent) {
+        for (const change of event.contentChanges) {
+            // Heuristic: Large single change likely a paste
+            const lineCount = change.text.split('\n').length;
+            
+            if (lineCount > 10) {
+                this.pastes.push({
+                    timestamp: Date.now(),
+                    size: lineCount,
+                    content: change.text,
+                    source: this.detectSource(change.text)
+                });
+            }
+        }
+    }
+    
+    private detectSource(text: string): 'clipboard' | 'external' | undefined {
+        // Try to detect if this came from external AI tool
+        // Look for characteristic formatting, comments, etc.
+        
+        if (this.hasAICommentPattern(text)) {
+            return 'external';
+        }
+        
+        return 'clipboard';
+    }
+    
+    private hasAICommentPattern(text: string): boolean {
+        // AI-generated code often has specific comment patterns
+        const patterns = [
+            /\/\/ Helper function to/,
+            /\/\/ This function/,
+            /"""[\s\S]*Args:[\s\S]*Returns:/,  // Python docstring
+        ];
+        
+        return patterns.some(p => p.test(text));
+    }
+    
+    public getScore(document: vscode.TextDocument): number {
+        const largePastes = this.pastes.filter(p => p.size > this.LARGE_PASTE_THRESHOLD);
+        const totalLines = document.lineCount;
+        const pastedLines = largePastes.reduce((sum, p) => sum + p.size, 0);
+        
+        // If >30% of file came from large pastes, suspicious
+        return Math.min((pastedLines / totalLines) / 0.3, 1.0);
+    }
+}