diff --git a/src/core/diff/strategies/multi-search-replace.ts b/src/core/diff/strategies/multi-search-replace.ts
index 00cebd2bea..f8f4e656e8 100644
--- a/src/core/diff/strategies/multi-search-replace.ts
+++ b/src/core/diff/strategies/multi-search-replace.ts
@@ -423,8 +423,10 @@ Only use a single line of '=======' between search and replacement content, beca
 			let searchStartIndex = 0
 			let searchEndIndex = resultLines.length
 
+			startLine = endLine = 0
+
 			// Validate and handle line range if provided
-			if (startLine) {
+			if (startLine && endLine) {
 				// Convert to 0-based index
 				const exactStartIndex = startLine - 1
 				const searchLen = searchLines.length
@@ -483,7 +485,7 @@ Only use a single line of '=======' between search and replacement content, beca
 				} else {
 					// No match found with either method
 					const originalContentSection =
-						startLine !== undefined && endLine !== undefined
+						startLine && endLine
 							? `\n\nOriginal Content:\n${addLineNumbers(
 									resultLines
 										.slice(
diff --git a/src/core/prompts/tools/insert-content.ts b/src/core/prompts/tools/insert-content.ts
index 7e339513d5..c575c0eb5c 100644
--- a/src/core/prompts/tools/insert-content.ts
+++ b/src/core/prompts/tools/insert-content.ts
@@ -29,5 +29,23 @@ Example for appending to the end of file:
 // This is the end of the file
 </content>
 </insert_content>
+
+Example for creating very large files that exceed output limits:
+<write_to_file>
+<path>src/large_file.txt</path>
+<content>
+// This is the beginning of a very large file but you must terminate prematurely in order for line_count to be produced:
+</content>
+<line_count>100</line_count>
+</write_to_file>
+
+Then use insert_content to append the rest of the content starting immediately where you left off; repeat as many times as necessary:
+<insert_content>
+<path>src/large_file.txt</path>
+<line>0</line>
+<content>
+// This is a continuation of very large file
+</content>
+</insert_content>
 `
 }
diff --git a/src/core/tools/insertContentTool.ts b/src/core/tools/insertContentTool.ts
index 8e6c5fc89e..d85f6c35ed 100644
--- a/src/core/tools/insertContentTool.ts
+++ b/src/core/tools/insertContentTool.ts
@@ -78,6 +78,13 @@ export async function insertContentTool(
 			return
 		}
 
+		if (lineNumber !== 0) {
+			cline.consecutiveMistakeCount++
+			cline.recordToolError("insert_content")
+			pushToolResult(formatResponse.toolError("Invalid line number: only append is supported so line must be 0"))
+			return
+		}
+
 		cline.consecutiveMistakeCount = 0
 
 		// Read the file
diff --git a/src/core/tools/writeToFileTool.ts b/src/core/tools/writeToFileTool.ts
index a23aea9714..e0a302e1a1 100644
--- a/src/core/tools/writeToFileTool.ts
+++ b/src/core/tools/writeToFileTool.ts
@@ -1,6 +1,7 @@
 import path from "path"
 import delay from "delay"
 import * as vscode from "vscode"
+import { countFileLines } from "../../integrations/misc/line-counter"
 
 import { Cline } from "../Cline"
 import { ClineSayTool } from "../../shared/ExtensionMessage"
@@ -69,6 +70,21 @@ export async function writeToFileTool(
 	const fullPath = relPath ? path.resolve(cline.cwd, removeClosingTag("path", relPath)) : ""
 	const isOutsideWorkspace = isPathOutsideWorkspace(fullPath)
 
+	if (fileExists) {
+		// Count the lines in the file
+		const absolutePath = path.resolve(cline.cwd, relPath)
+		const lineCount = await countFileLines(absolutePath)
+		// Only show error if file has more than 25 lines
+		if (lineCount > 25) {
+			pushToolResult(
+				formatResponse.toolError(
+					`File '${relPath}' already exists and is >25 lines long, write_to_file failed: You must use the '<apply_diff>' or '<search_and_replace>' tool to change an existing file.`,
+				),
+			)
+			return
+		}
+	}
+
 	const sharedMessageProps: ClineSayTool = {
 		tool: fileExists ? "editedExistingFile" : "newFileCreated",
 		path: getReadablePath(cline.cwd, removeClosingTag("path", relPath)),
diff --git a/src/integrations/misc/extract-text.ts b/src/integrations/misc/extract-text.ts
index 5bbbbf8514..924badc1d1 100644
--- a/src/integrations/misc/extract-text.ts
+++ b/src/integrations/misc/extract-text.ts
@@ -55,6 +55,8 @@ async function extractTextFromIPYNB(filePath: string): Promise<string> {
 }
 
 export function addLineNumbers(content: string, startLine: number = 1): string {
+	return content
+
 	// If content is empty, return empty string - empty files should not have line numbers
 	// If content is empty but startLine > 1, return "startLine | " because we know the file is not empty
 	// but the content is empty at that line offset