diff --git a/.changeset/poor-adults-fetch.md b/.changeset/poor-adults-fetch.md
new file mode 100644
index 0000000..32ac663
--- /dev/null
+++ b/.changeset/poor-adults-fetch.md
@@ -0,0 +1,5 @@
+---
+"roo-cline": patch
+---
+
+Fix bug where apply_diff wasn't showing up in system prompt preview
diff --git a/src/core/webview/ClineProvider.ts b/src/core/webview/ClineProvider.ts
index 72e7e27..cce08e2 100644
--- a/src/core/webview/ClineProvider.ts
+++ b/src/core/webview/ClineProvider.ts
@@ -10,6 +10,7 @@ import { downloadTask } from "../../integrations/misc/export-markdown"
 import { openFile, openImage } from "../../integrations/misc/open-file"
 import { selectImages } from "../../integrations/misc/process-images"
 import { getTheme } from "../../integrations/theme/getTheme"
+import { getDiffStrategy } from "../diff/DiffStrategy"
 import WorkspaceTracker from "../../integrations/workspace/WorkspaceTracker"
 import { McpHub } from "../../services/mcp/McpHub"
 import { ApiConfiguration, ApiProvider, ModelInfo } from "../../shared/api"
@@ -962,7 +963,16 @@ export class ClineProvider implements vscode.WebviewViewProvider {
 								preferredLanguage,
 								browserViewportSize,
 								mcpEnabled,
+								fuzzyMatchThreshold,
+								experimentalDiffStrategy,
 							} = await this.getState()
+
+							// Create diffStrategy based on current model and settings
+							const diffStrategy = getDiffStrategy(
+								apiConfiguration.apiModelId || apiConfiguration.openRouterModelId || "",
+								fuzzyMatchThreshold,
+								experimentalDiffStrategy,
+							)
 							const cwd =
 								vscode.workspace.workspaceFolders?.map((folder) => folder.uri.fsPath).at(0) || ""
 
@@ -979,7 +989,7 @@ export class ClineProvider implements vscode.WebviewViewProvider {
 								cwd,
 								apiConfiguration.openRouterModelInfo?.supportsComputerUse ?? false,
 								mcpEnabled ? this.mcpHub : undefined,
-								undefined,
+								diffStrategy,
 								browserViewportSize ?? "900x600",
 								mode,
 								{
diff --git a/src/core/webview/__tests__/ClineProvider.test.ts b/src/core/webview/__tests__/ClineProvider.test.ts
index ff427a9..b672110 100644
--- a/src/core/webview/__tests__/ClineProvider.test.ts
+++ b/src/core/webview/__tests__/ClineProvider.test.ts
@@ -70,6 +70,13 @@ jest.mock(
 	{ virtual: true },
 )
 
+// Mock DiffStrategy
+jest.mock("../../diff/DiffStrategy", () => ({
+	getDiffStrategy: jest.fn().mockImplementation(() => ({
+		getToolDescription: jest.fn().mockReturnValue("apply_diff tool description"),
+	})),
+}))
+
 // Mock dependencies
 jest.mock("vscode", () => ({
 	ExtensionContext: jest.fn(),
@@ -963,6 +970,52 @@ describe("ClineProvider", () => {
 			)
 		})
 
+		test("passes diffStrategy to SYSTEM_PROMPT when previewing", async () => {
+			// Mock getState to return experimentalDiffStrategy and fuzzyMatchThreshold
+			jest.spyOn(provider, "getState").mockResolvedValue({
+				apiConfiguration: {
+					apiProvider: "openrouter",
+					apiModelId: "test-model",
+					openRouterModelInfo: { supportsComputerUse: true },
+				},
+				customPrompts: {},
+				mode: "code",
+				mcpEnabled: false,
+				browserViewportSize: "900x600",
+				experimentalDiffStrategy: true,
+				fuzzyMatchThreshold: 0.8,
+			} as any)
+
+			// Mock SYSTEM_PROMPT to verify diffStrategy is passed
+			const systemPromptModule = require("../../prompts/system")
+			const systemPromptSpy = jest.spyOn(systemPromptModule, "SYSTEM_PROMPT")
+
+			// Trigger getSystemPrompt
+			const handler = getMessageHandler()
+			await handler({ type: "getSystemPrompt", mode: "code" })
+
+			// Verify SYSTEM_PROMPT was called with correct arguments
+			expect(systemPromptSpy).toHaveBeenCalledWith(
+				expect.anything(), // context
+				expect.any(String), // cwd
+				true, // supportsComputerUse
+				undefined, // mcpHub (disabled)
+				expect.objectContaining({
+					// diffStrategy
+					getToolDescription: expect.any(Function),
+				}),
+				"900x600", // browserViewportSize
+				"code", // mode
+				expect.any(Object), // customPrompts
+				expect.any(Object), // customModes
+				undefined, // effectiveInstructions
+			)
+
+			// Run the test again to verify it's consistent
+			await handler({ type: "getSystemPrompt", mode: "code" })
+			expect(systemPromptSpy).toHaveBeenCalledTimes(2)
+		})
+
 		test("uses correct mode-specific instructions when mode is specified", async () => {
 			// Mock getState to return architect mode instructions
 			jest.spyOn(provider, "getState").mockResolvedValue({