fix: improve multi-file diff error handling and UI feedback

- Fix nested array issue in multi-file-search-replace strategy
- Consolidate diff error reporting to single message
- Fix infinite spinner on single file diff failures

Author: daniel-lxs

src/core/diff/strategies/multi-file-search-replace.ts

@@ -410,7 +410,13 @@ Each file requires its own path, start_line, and diff elements.
 					resultContent = singleResult.content
 					successCount++
 				} else {
-					allFailParts.push(singleResult)
+					// If singleResult has failParts, push those directly to avoid nesting
+					if (singleResult.failParts && singleResult.failParts.length > 0) {
+						allFailParts.push(...singleResult.failParts)
+					} else {
+						// Otherwise push the single result itself
+						allFailParts.push(singleResult)
+					}
 				}
 			}
 

src/core/tools/multiApplyDiffTool.ts

@@ -161,7 +161,6 @@ Expected structure:
 Original error: ${errorMessage}`
 			throw new Error(detailedError)
 		}
-
 	} else if (legacyPath && typeof legacyDiffContent === "string") {
 		// Handle legacy parameters (old way)
 		usingLegacyParams = true
@@ -221,6 +220,7 @@ Original error: ${errorMessage}`
 	try {
 		// First validate all files and prepare for batch approval
 		const operationsToApprove: OperationResult[] = []
+		const allDiffErrors: string[] = [] // Collect all diff errors
 
 		for (const operation of operations) {
 			const { path: relPath, diff: diffItems } = operation
@@ -427,6 +427,9 @@ Original error: ${errorMessage}`
 								continue
 							}
 
+							// Collect error for later reporting
+							allDiffErrors.push(`${relPath} - Diff ${i + 1}: ${failPart.error}`)
+
 							const errorDetails = failPart.details ? JSON.stringify(failPart.details, null, 2) : ""
 							formattedError += `<error_details>
 Diff ${i + 1} failed for file: ${relPath}
@@ -471,6 +474,17 @@ ${errorDetails ? `\nTechnical details:\n${errorDetails}\n` : ""}
 						}
 						cline.recordToolError("apply_diff", formattedError)
 						results.push(formattedError)
+
+						// For single file operations, we need to send a complete message to stop the spinner
+						if (operationsToApprove.length === 1) {
+							const sharedMessageProps: ClineSayTool = {
+								tool: "appliedDiff",
+								path: getReadablePath(cline.cwd, relPath),
+								diff: diffItems.map((item) => item.content).join("\n\n"),
+							}
+							// Send a complete message (partial: false) to update the UI and stop the spinner
+							await cline.ask("tool", JSON.stringify(sharedMessageProps), false).catch(() => {})
+						}
 					}
 					continue
 				}
@@ -559,6 +573,11 @@ ${errorDetails ? `\nTechnical details:\n${errorDetails}\n` : ""}
 			results.push(...filteredOperationErrors)
 		}
 
+		// Report all diff errors at once if any
+		if (allDiffErrors.length > 0) {
+			await cline.say("diff_error", allDiffErrors.join("\n"))
+		}
+
 		// Push the final result combining all operation results
 		pushToolResult(results.join("\n\n"))
 		return