feat: improve error display with custom titles and expandable UI

- Add metadata support to ClineMessage type for storing custom error titles
- Update ChatRow component to display errors with expandable UI similar to diff_error
- Add sayError helper method to Task class for convenient error reporting
- Update existing error calls to use custom titles for better context
- Fix test to match new error format with metadata

implementation-plan.md

@@ -0,0 +1,113 @@
+# Implementation Plan: Improve Error Display in Webview
+
+## Overview
+
+Currently, `cline.say("error", ...)` displays error text in red. We want to improve this to look more like the "Edit Unsuccessful" display with:
+
+1. A custom title that can be passed as metadata
+2. An expandable/collapsible UI pattern
+3. The error text shown when expanded
+
+## Current Implementation Analysis
+
+### 1. Error Display Flow
+
+- **Backend (Task.ts)**: `say("error", text)` method sends error messages
+- **Frontend (ChatRow.tsx)**: Renders error messages with red text styling
+- **Diff Error Pattern**: Already implements the expandable UI pattern we want to replicate
+
+### 2. Diff Error Implementation (lines 960-1048 in ChatRow.tsx)
+
+The diff_error display has:
+
+- Warning icon with yellow/orange color
+- Bold title ("Edit Unsuccessful")
+- Copy button
+- Expand/collapse chevron
+- Expandable content area showing the error details
+
+## Implementation Steps
+
+### Step 1: Extend the say method signature
+
+**File**: `src/core/task/Task.ts`
+
+The say method already accepts an `options` parameter with metadata support. We need to:
+
+- Document that error messages can include a `title` in metadata
+- No changes needed to the method signature itself
+
+### Step 2: Update ChatRow.tsx to handle enhanced error display
+
+**File**: `webview-ui/src/components/chat/ChatRow.tsx`
+
+Changes needed:
+
+1. Add state for error expansion (similar to `isDiffErrorExpanded`)
+2. Extract metadata from error messages
+3. Render errors with the expandable UI pattern
+4. Use custom title from metadata or default to "Error"
+
+### Step 3: Update translation files
+
+**Files**: All files in `webview-ui/src/i18n/locales/*/chat.json`
+
+Add new translation keys:
+
+- `error.defaultTitle`: Default title when no custom title is provided
+- Keep existing `error` key for backward compatibility
+
+### Step 4: Update existing error calls
+
+Search for all `say("error", ...)` calls and optionally add metadata with custom titles where appropriate.
+
+## Technical Details
+
+### Message Structure
+
+```typescript
+// When calling say with error and custom title:
+await this.say(
+	"error",
+	"Detailed error message here",
+	undefined, // images
+	false, // partial
+	undefined, // checkpoint
+	undefined, // progressStatus
+	{
+		metadata: {
+			title: "Custom Error Title",
+		},
+	},
+)
+```
+
+### Frontend Rendering Logic
+
+```typescript
+// In ChatRow.tsx, for case "error":
+// 1. Extract title from metadata or use default
+// 2. Render expandable UI similar to diff_error
+// 3. Show error text in expanded section
+```
+
+## Benefits
+
+1. **Consistency**: Error display matches the existing "Edit Unsuccessful" pattern
+2. **Clarity**: Custom titles provide immediate context about the error type
+3. **User Experience**: Collapsible errors reduce visual clutter
+4. **Flexibility**: Backward compatible - existing error calls continue to work
+
+## Testing Considerations
+
+1. Test with errors that have custom titles
+2. Test with errors without custom titles (should use default)
+3. Test expand/collapse functionality
+4. Test copy button functionality
+5. Verify all translations work correctly
+
+## Migration Strategy
+
+- The implementation is backward compatible
+- Existing `say("error", ...)` calls will continue to work
+- We can gradually update error calls to include custom titles where beneficial

packages/types/src/message.ts

@@ -224,6 +224,7 @@ export const clineMessageSchema = z.object({
 					reasoning_summary: z.string().optional(),
 				})
 				.optional(),
+			title: z.string().optional(), // Custom title for error messages
 		})
 		.optional(),
 })

src/core/task/Task.ts

@@ -1169,10 +1169,33 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 			`Roo tried to use ${toolName}${
 				relPath ? ` for '${relPath.toPosix()}'` : ""
 			} without value for required parameter '${paramName}'. Retrying...`,
+			undefined,
+			undefined,
+			undefined,
+			undefined,
+			{
+				metadata: {
+					title: "Missing Parameter Error",
+				},
+			},
 		)
 		return formatResponse.toolError(formatResponse.missingToolParameterError(paramName))
 	}
 
+	/**
+	 * Helper method to say an error with a custom title
+	 * @param title - The title to display for the error
+	 * @param text - The error message text
+	 * @param images - Optional images to include
+	 */
+	async sayError(title: string, text: string, images?: string[]) {
+		await this.say("error", text, images, undefined, undefined, undefined, {
+			metadata: {
+				title,
+			},
+		})
+	}
+
 	// Lifecycle
 	// Start / Resume / Abort / Dispose
 

src/core/tools/__tests__/insertContentTool.spec.ts

@@ -226,7 +226,19 @@ describe("insertContentTool", () => {
 			expect(mockedFsReadFile).not.toHaveBeenCalled()
 			expect(mockCline.consecutiveMistakeCount).toBe(1)
 			expect(mockCline.recordToolError).toHaveBeenCalledWith("insert_content")
-			expect(mockCline.say).toHaveBeenCalledWith("error", expect.stringContaining("non-existent file"))
+			expect(mockCline.say).toHaveBeenCalledWith(
+				"error",
+				expect.stringContaining("non-existent file"),
+				undefined,
+				undefined,
+				undefined,
+				undefined,
+				expect.objectContaining({
+					metadata: expect.objectContaining({
+						title: "Invalid Line Number",
+					}),
+				}),
+			)
 			expect(mockCline.diffViewProvider.update).not.toHaveBeenCalled()
 			expect(mockCline.diffViewProvider.pushToolWriteResult).not.toHaveBeenCalled()
 		})

src/core/tools/applyDiffTool.ts

@@ -83,7 +83,9 @@ export async function applyDiffToolLegacy(
 				cline.consecutiveMistakeCount++
 				cline.recordToolError("apply_diff")
 				const formattedError = `File does not exist at path: ${absolutePath}\n\n<error_details>\nThe specified file could not be found. Please verify the file path and try again.\n</error_details>`
-				await cline.say("error", formattedError)
+				await cline.say("error", formattedError, undefined, undefined, undefined, undefined, {
+					metadata: { title: "File Not Found" },
+				})
 				pushToolResult(formattedError)
 				return
 			}

src/core/tools/insertContentTool.ts

@@ -87,7 +87,9 @@ export async function insertContentTool(
 				cline.consecutiveMistakeCount++
 				cline.recordToolError("insert_content")
 				const formattedError = `Cannot insert content at line ${lineNumber} into a non-existent file. For new files, 'line' must be 0 (to append) or 1 (to insert at the beginning).`
-				await cline.say("error", formattedError)
+				await cline.say("error", formattedError, undefined, undefined, undefined, undefined, {
+					metadata: { title: "Invalid Line Number" },
+				})
 				pushToolResult(formattedError)
 				return
 			}

webview-ui/src/components/chat/ChatRow.tsx

@@ -120,7 +120,9 @@ export const ChatRowContent = ({
 	const { info: model } = useSelectedModel(apiConfiguration)
 	const [reasoningCollapsed, setReasoningCollapsed] = useState(true)
 	const [isDiffErrorExpanded, setIsDiffErrorExpanded] = useState(false)
+	const [isErrorExpanded, setIsErrorExpanded] = useState(false)
 	const [showCopySuccess, setShowCopySuccess] = useState(false)
+	const [showErrorCopySuccess, setShowErrorCopySuccess] = useState(false)
 	const [isEditing, setIsEditing] = useState(false)
 	const [editedContent, setEditedContent] = useState("")
 	const [editMode, setEditMode] = useState<Mode>(mode || "code")
@@ -1243,16 +1245,99 @@ export const ChatRowContent = ({
 						</div>
 					)
 				case "error":
+					// Extract custom title from metadata if available
+					const errorTitle = (message as any).metadata?.title || t("chat:error")
+
 					return (
-						<>
-							{title && (
-								<div style={headerStyle}>
-									{icon}
-									{title}
+						<div>
+							<div
+								style={{
+									marginTop: "0px",
+									overflow: "hidden",
+									marginBottom: "8px",
+								}}>
+								<div
+									style={{
+										borderBottom: isErrorExpanded
+											? "1px solid var(--vscode-editorGroup-border)"
+											: "none",
+										fontWeight: "normal",
+										fontSize: "var(--vscode-font-size)",
+										color: "var(--vscode-editor-foreground)",
+										display: "flex",
+										alignItems: "center",
+										justifyContent: "space-between",
+										cursor: "pointer",
+									}}
+									onClick={() => setIsErrorExpanded(!isErrorExpanded)}>
+									<div
+										style={{
+											display: "flex",
+											alignItems: "center",
+											gap: "10px",
+											flexGrow: 1,
+										}}>
+										<span
+											className="codicon codicon-error"
+											style={{
+												color: "var(--vscode-errorForeground)",
+												fontSize: 16,
+												marginBottom: "-1.5px",
+											}}></span>
+										<span style={{ fontWeight: "bold", color: "var(--vscode-errorForeground)" }}>
+											{errorTitle}
+										</span>
+									</div>
+									<div style={{ display: "flex", alignItems: "center" }}>
+										<VSCodeButton
+											appearance="icon"
+											style={{
+												padding: "3px",
+												height: "24px",
+												marginRight: "4px",
+												color: "var(--vscode-editor-foreground)",
+												display: "flex",
+												alignItems: "center",
+												justifyContent: "center",
+												background: "transparent",
+											}}
+											onClick={(e) => {
+												e.stopPropagation()
+
+												// Call copyWithFeedback and handle the Promise
+												copyWithFeedback(message.text || "").then((success) => {
+													if (success) {
+														// Show checkmark
+														setShowErrorCopySuccess(true)
+
+														// Reset after a brief delay
+														setTimeout(() => {
+															setShowErrorCopySuccess(false)
+														}, 1000)
+													}
+												})
+											}}>
+											<span
+												className={`codicon codicon-${showErrorCopySuccess ? "check" : "copy"}`}></span>
+										</VSCodeButton>
+										<span
+											className={`codicon codicon-chevron-${isErrorExpanded ? "up" : "down"}`}></span>
+									</div>
 								</div>
-							)}
-							<p style={{ ...pStyle, color: "var(--vscode-errorForeground)" }}>{message.text}</p>
-						</>
+								{isErrorExpanded && (
+									<div
+										style={{
+											padding: "8px",
+											backgroundColor: "var(--vscode-editor-background)",
+											borderTop: "none",
+										}}>
+										<p style={{ ...pStyle, color: "var(--vscode-errorForeground)", margin: 0 }}>
+											{message.text}
+										</p>
+									</div>
+								)}
+							</div>
+						</div>
 					)
 				case "completion_result":
 					return (