fix: improve HTML entity unescaping for Gemini and other models

- Add HTML entity unescaping to applyDiffTool for non-Claude models
- Enhance unescapeHtmlEntities function to handle more entity types
- Add support for alternative encodings like ', /, \, `
- Add comprehensive tests for new entity types
- Improve comments to clarify the purpose of unescaping

Fixes #7890

src/core/tools/applyDiffTool.ts

@@ -25,6 +25,8 @@ export async function applyDiffToolLegacy(
 	const relPath: string | undefined = block.params.path
 	let diffContent: string | undefined = block.params.diff
 
+	// Unescape HTML entities for non-Claude models (e.g., Gemini, DeepSeek, Llama)
+	// These models may return content with escaped characters that need to be unescaped
 	if (diffContent && !cline.api.getModel().id.includes("claude")) {
 		diffContent = unescapeHtmlEntities(diffContent)
 	}

src/core/tools/writeToFileTool.ts

@@ -73,9 +73,11 @@ export async function writeToFileTool(
 		cline.diffViewProvider.editType = fileExists ? "modify" : "create"
 	}
 
-	// pre-processing newContent for cases where weaker models might add artifacts like markdown codeblock markers (deepseek/llama) or extra escape characters (gemini)
+	// Pre-processing newContent for cases where models might add artifacts
+	// Some models (DeepSeek/Llama) add markdown codeblock markers
+	// Others (Gemini) return content with HTML-escaped characters
 	if (newContent.startsWith("```")) {
-		// cline handles cases where it includes language specifiers like ```python ```js
+		// Handle cases where it includes language specifiers like ```python ```js
 		newContent = newContent.split("\n").slice(1).join("\n")
 	}
 
@@ -83,6 +85,8 @@ export async function writeToFileTool(
 		newContent = newContent.split("\n").slice(0, -1).join("\n")
 	}
 
+	// Unescape HTML entities for non-Claude models (e.g., Gemini, DeepSeek, Llama)
+	// These models may return content with escaped characters that need to be unescaped
 	if (!cline.api.getModel().id.includes("claude")) {
 		newContent = unescapeHtmlEntities(newContent)
 	}

src/utils/__tests__/text-normalization-extended.spec.ts

@@ -0,0 +1,57 @@
+import { describe, it, expect } from "vitest"
+import { unescapeHtmlEntities } from "../text-normalization"
+
+describe("Extended HTML entity unescaping", () => {
+	describe("unescapeHtmlEntities", () => {
+		it("unescapes alternative apostrophe encoding", () => {
+			const input = "It's working"
+			const expected = "It's working"
+			expect(unescapeHtmlEntities(input)).toBe(expected)
+		})
+
+		it("unescapes forward slash", () => {
+			const input = "path/to/file"
+			const expected = "path/to/file"
+			expect(unescapeHtmlEntities(input)).toBe(expected)
+		})
+
+		it("unescapes backslash", () => {
+			const input = "C:\Users\file"
+			const expected = "C:\\Users\\file"
+			expect(unescapeHtmlEntities(input)).toBe(expected)
+		})
+
+		it("unescapes backtick", () => {
+			const input = "`code`"
+			const expected = "`code`"
+			expect(unescapeHtmlEntities(input)).toBe(expected)
+		})
+
+		it("unescapes non-breaking space", () => {
+			const input = "Hello World"
+			const expected = "Hello World"
+			expect(unescapeHtmlEntities(input)).toBe(expected)
+		})
+
+		it("handles complex mixed content with all entity types", () => {
+			const input =
+				"<div class="test">It's a  test/path\file with `code` & more</div>"
+			const expected = '<div class="test">It\'s a  test/path\\file with `code` & more</div>'
+			expect(unescapeHtmlEntities(input)).toBe(expected)
+		})
+
+		it("handles Gemini-style escaped markdown content", () => {
+			const input =
+				"```python\n&lt;search&gt;\ndef old_function():\n    return &#x27;old&#x27;\n&lt;/search&gt;\n&lt;replace&gt;\ndef new_function():\n    return &#x27;new&#x27;\n&lt;/replace&gt;\n```"
+			const expected =
+				"```python\n<search>\ndef old_function():\n    return 'old'\n</search>\n<replace>\ndef new_function():\n    return 'new'\n</replace>\n```"
+			expect(unescapeHtmlEntities(input)).toBe(expected)
+		})
+
+		it("correctly orders ampersand unescaping to avoid double-unescaping", () => {
+			const input = "&amp;lt;&amp;gt;&amp;amp;"
+			const expected = "&lt;&gt;&amp;"
+			expect(unescapeHtmlEntities(input)).toBe(expected)
+		})
+	})
+})

src/utils/text-normalization.ts

@@ -91,5 +91,10 @@ export function unescapeHtmlEntities(text: string): string {
 		.replace(/"/g, '"')
 		.replace(/'/g, "'")
 		.replace(/'/g, "'")
-		.replace(/&/g, "&")
+		.replace(/'/g, "'") // Alternative apostrophe encoding
+		.replace(///g, "/") // Forward slash
+		.replace(/\/g, "\\") // Backslash
+		.replace(/`/g, "`") // Backtick
+		.replace(/ /g, " ") // Non-breaking space
+		.replace(/&/g, "&") // Must be last to avoid double-unescaping
 }