diff --git a/src/prompt-cache.js b/src/prompt-cache.js
index b5514aa..3eb72c3 100644
--- a/src/prompt-cache.js
+++ b/src/prompt-cache.js
@@ -195,6 +195,7 @@ Code suggestions enable reviewers to apply fixes directly as GitHub suggestions.
  */
 const LINE_NUMBERS_RULE = `**CRITICAL 'lineNumbers' RULE - MANDATORY COMPLIANCE**:
 - **ALWAYS provide line numbers** - this field is REQUIRED for every issue
+- **Line numbers are shown in the file content** as a prefix on each line (e.g., "  42 | const x = 1;"). Use THESE line numbers directly - do NOT try to count lines yourself.
 - If you can identify specific lines, provide them (max 3-5 for repeated issues)
 - If the issue affects the entire file or cannot be pinpointed, provide [1] or relevant section line numbers
 - For ANY issue that occurs multiple times in a file, list ONLY the first 3-5 occurrences maximum
diff --git a/src/rag-analyzer.js b/src/rag-analyzer.js
index b19143f..2185c7c 100644
--- a/src/rag-analyzer.js
+++ b/src/rag-analyzer.js
@@ -27,6 +27,7 @@ import { isGenericDocument, getGenericDocumentContext } from './utils/document-d
 import { isTestFile, shouldProcessFile } from './utils/file-validation.js';
 import { detectFileType, detectLanguageFromExtension } from './utils/language-detection.js';
 import { debug } from './utils/logging.js';
+import { addLineNumbers } from './utils/string-utils.js';
 
 // Constants for content processing
 const MAX_QUERY_CONTEXT_LENGTH = 1500;
@@ -1047,10 +1048,10 @@ You have access to TWO pieces of information:
 - Do NOT flag functions/variables as missing if they exist elsewhere in the full file
 - The unchanged code is part of the file - check it before making assumptions
 
-**FULL FILE CONTENT (for context - DO NOT review unchanged code):**
+**FULL FILE CONTENT (for context - DO NOT review unchanged code, line numbers shown for reference):**
 
 \`\`\`${file.language}
-${file.fullFileContent || file.content}
+${addLineNumbers(file.fullFileContent || file.content)}
 \`\`\`
 
 **GIT DIFF TO REVIEW (critique ONLY these changes):**
@@ -1063,7 +1064,7 @@ Path: ${file.path}
 Language: ${file.language}
 
 \`\`\`${file.language}
-${file.content}
+${addLineNumbers(file.content)}
 \`\`\``;
 
   // Add project architecture context if available
@@ -1166,10 +1167,10 @@ You have access to TWO pieces of information:
 - Check the full file for existing test cases before making assumptions
 - The unchanged test code is part of the file - review it before suggesting additions
 
-**FULL TEST FILE CONTENT (for context - check for existing tests):**
+**FULL TEST FILE CONTENT (for context - check for existing tests, line numbers shown for reference):**
 
 \`\`\`${file.language}
-${file.fullFileContent || file.content}
+${addLineNumbers(file.fullFileContent || file.content)}
 \`\`\`
 
 **GIT DIFF TO REVIEW (critique ONLY these changes):**
@@ -1182,7 +1183,7 @@ Path: ${file.path}
 Language: ${file.language}
 
 \`\`\`${file.language}
-${file.content}
+${addLineNumbers(file.content)}
 \`\`\``;
 
   // Use shared helpers for custom docs and role definition
@@ -1317,9 +1318,9 @@ ${g.content}
 ${prFile.diff}
 \`\`\`
 
-### Full File Content (For Context):
+### Full File Content (For Context - line numbers shown for reference):
 \`\`\`${prFile.language}
-${prFile.fullContent}
+${addLineNumbers(prFile.fullContent)}
 \`\`\`
 `;
     })
diff --git a/src/utils/string-utils.js b/src/utils/string-utils.js
index b544be5..950acd2 100644
--- a/src/utils/string-utils.js
+++ b/src/utils/string-utils.js
@@ -26,3 +26,28 @@ export function slugify(text) {
     .replace(/[^\w-]+/g, '') // Remove all non-word chars
     .replace(/--+/g, '-'); // Replace multiple - with single -
 }
+
+/**
+ * Add line numbers to source code content so LLMs can accurately reference
+ * specific lines when performing code reviews.
+ *
+ * Each line is prefixed with its 1-based line number followed by a pipe separator.
+ * The line numbers are right-aligned with consistent padding based on the total
+ * number of lines, making the output easy to read.
+ *
+ * @param {string} content - The source code content to annotate
+ * @returns {string} The content with line numbers prepended to each line
+ *
+ * @example
+ * addLineNumbers('const a = 1;\nconst b = 2;');
+ * // '1 | const a = 1;\n2 | const b = 2;'
+ *
+ * @example
+ * addLineNumbers(''); // ''
+ */
+export function addLineNumbers(content) {
+  if (!content) return '';
+  const lines = content.split('\n');
+  const padding = String(lines.length).length;
+  return lines.map((line, i) => `${String(i + 1).padStart(padding)} | ${line}`).join('\n');
+}
diff --git a/src/utils/string-utils.test.js b/src/utils/string-utils.test.js
index b96d2a0..d020834 100644
--- a/src/utils/string-utils.test.js
+++ b/src/utils/string-utils.test.js
@@ -1,4 +1,4 @@
-import { slugify } from './string-utils.js';
+import { slugify, addLineNumbers } from './string-utils.js';
 
 describe('slugify', () => {
   describe('basic transformations', () => {
@@ -84,3 +84,72 @@ describe('slugify', () => {
     });
   });
 });
+
+describe('addLineNumbers', () => {
+  describe('basic functionality', () => {
+    it('should add line numbers to each line', () => {
+      const input = 'const a = 1;\nconst b = 2;';
+      const result = addLineNumbers(input);
+      expect(result).toBe('1 | const a = 1;\n2 | const b = 2;');
+    });
+
+    it('should pad line numbers for files with 10+ lines', () => {
+      const lines = Array.from({ length: 12 }, (_, i) => `line ${i + 1}`);
+      const input = lines.join('\n');
+      const result = addLineNumbers(input);
+      const outputLines = result.split('\n');
+      // Single-digit lines should be padded with a leading space
+      expect(outputLines[0]).toBe(' 1 | line 1');
+      expect(outputLines[8]).toBe(' 9 | line 9');
+      // Double-digit lines should not be padded
+      expect(outputLines[9]).toBe('10 | line 10');
+      expect(outputLines[11]).toBe('12 | line 12');
+    });
+
+    it('should pad line numbers for files with 100+ lines', () => {
+      const lines = Array.from({ length: 105 }, (_, i) => `line ${i + 1}`);
+      const input = lines.join('\n');
+      const result = addLineNumbers(input);
+      const outputLines = result.split('\n');
+      expect(outputLines[0]).toBe('  1 | line 1');
+      expect(outputLines[9]).toBe(' 10 | line 10');
+      expect(outputLines[99]).toBe('100 | line 100');
+    });
+
+    it('should handle a single line', () => {
+      expect(addLineNumbers('hello')).toBe('1 | hello');
+    });
+
+    it('should preserve empty lines', () => {
+      const input = 'line1\n\nline3';
+      const result = addLineNumbers(input);
+      expect(result).toBe('1 | line1\n2 | \n3 | line3');
+    });
+
+    it('should preserve indentation', () => {
+      const input = 'function foo() {\n  return 1;\n}';
+      const result = addLineNumbers(input);
+      expect(result).toBe('1 | function foo() {\n2 |   return 1;\n3 | }');
+    });
+  });
+
+  describe('edge cases', () => {
+    it('should return empty string for null input', () => {
+      expect(addLineNumbers(null)).toBe('');
+    });
+
+    it('should return empty string for undefined input', () => {
+      expect(addLineNumbers(undefined)).toBe('');
+    });
+
+    it('should return empty string for empty string input', () => {
+      expect(addLineNumbers('')).toBe('');
+    });
+
+    it('should handle content with trailing newline', () => {
+      const input = 'line1\nline2\n';
+      const result = addLineNumbers(input);
+      expect(result).toBe('1 | line1\n2 | line2\n3 | ');
+    });
+  });
+});