feat(conversation): improve OpenWebUI error handling and parsing

lib/core/models/chat_message.dart

@@ -34,12 +34,88 @@ sealed class ChatMessage with _$ChatMessage {
     @JsonKey(includeFromJson: false, includeToJson: false)
     @Default(<ChatMessageVersion>[])
     List<ChatMessageVersion> versions,
+    // Error information from OpenWebUI (stored separately from content)
+    @JsonKey(fromJson: _chatMessageErrorFromJson, toJson: _chatMessageErrorToJson)
+    ChatMessageError? error,
   }) = _ChatMessage;
 
   factory ChatMessage.fromJson(Map<String, dynamic> json) =>
       _$ChatMessageFromJson(json);
 }
 
+/// Error information for a chat message, matching OpenWebUI's error format.
+/// OpenWebUI stores errors as `{ error: { content: "..." } }` on messages.
+@freezed
+abstract class ChatMessageError with _$ChatMessageError {
+  const factory ChatMessageError({
+    /// The error message content
+    @JsonKey(fromJson: _nullableString) String? content,
+  }) = _ChatMessageError;
+
+  factory ChatMessageError.fromJson(Map<String, dynamic> json) =>
+      _$ChatMessageErrorFromJson(json);
+}
+
+/// Parse ChatMessageError from various OpenWebUI formats.
+ChatMessageError? _chatMessageErrorFromJson(dynamic value) {
+  if (value == null) return null;
+
+  // Legacy format: error === true means content IS the error
+  if (value == true) {
+    return const ChatMessageError(content: null);
+  }
+
+  if (value is String && value.isNotEmpty) {
+    return ChatMessageError(content: value);
+  }
+
+  if (value is Map) {
+    // Most common: { content: "error message" }
+    final content = value['content'];
+    if (content is String && content.isNotEmpty) {
+      return ChatMessageError(content: content);
+    }
+
+    // Alternative: { message: "error message" }
+    final message = value['message'];
+    if (message is String && message.isNotEmpty) {
+      return ChatMessageError(content: message);
+    }
+
+    // Nested error: { error: { message: "..." } }
+    final nestedError = value['error'];
+    if (nestedError is Map) {
+      final nestedMessage = nestedError['message'];
+      if (nestedMessage is String && nestedMessage.isNotEmpty) {
+        return ChatMessageError(content: nestedMessage);
+      }
+    }
+
+    // FastAPI detail format: { detail: "..." }
+    final detail = value['detail'];
+    if (detail is String && detail.isNotEmpty) {
+      return ChatMessageError(content: detail);
+    }
+
+    // If it's a map but we couldn't extract content, still return an error
+    // to indicate there was an error (matches legacy error === true behavior)
+    return const ChatMessageError(content: null);
+  }
+
+  return null;
+}
+
+/// Convert ChatMessageError to OpenWebUI format for persistence.
+Map<String, dynamic>? _chatMessageErrorToJson(ChatMessageError? error) {
+  if (error == null) return null;
+  if (error.content == null) {
+    // Legacy format - just return true to indicate error
+    // But OpenWebUI expects a map, so return empty content
+    return const {'content': ''};
+  }
+  return {'content': error.content};
+}
+
 @freezed
 abstract class ChatMessageVersion with _$ChatMessageVersion {
   const factory ChatMessageVersion({

lib/core/services/api_service.dart

@@ -843,6 +843,8 @@ class ApiService {
           'attachment_ids': List<String>.from(msg.attachmentIds!),
         if (_sanitizeFilesForWebUI(msg.files) != null)
           'files': _sanitizeFilesForWebUI(msg.files),
+        // Preserve error field for OpenWebUI compatibility
+        if (msg.error != null) 'error': msg.error!.toJson(),
       };
 
       // Update parent's childrenIds if there's a previous message
@@ -863,6 +865,8 @@ class ApiService {
           'attachment_ids': List<String>.from(msg.attachmentIds!),
         if (_sanitizeFilesForWebUI(msg.files) != null)
           'files': _sanitizeFilesForWebUI(msg.files),
+        // Preserve error field for OpenWebUI compatibility
+        if (msg.error != null) 'error': msg.error!.toJson(),
       });
 
       previousId = messageId;
@@ -977,6 +981,8 @@ class ApiService {
           'sources': msg.sources.map((s) => s.toJson()).toList(),
         // Include usage statistics for persistence (issue #274)
         if (msg.usage != null) 'usage': msg.usage,
+        // Preserve error field for OpenWebUI compatibility
+        if (msg.error != null) 'error': msg.error!.toJson(),
       };
 
       // Update parent's childrenIds
@@ -1014,6 +1020,8 @@ class ApiService {
           'sources': msg.sources.map((s) => s.toJson()).toList(),
         // Include usage statistics for persistence (issue #274)
         if (msg.usage != null) 'usage': msg.usage,
+        // Preserve error field for OpenWebUI compatibility
+        if (msg.error != null) 'error': msg.error!.toJson(),
       });
 
       previousId = messageId;

lib/core/services/conversation_parsing.dart

@@ -191,6 +191,57 @@ List<Map<String, dynamic>>? _extractToolCalls(
   return null;
 }
 
+/// Extract error data from OpenWebUI message format.
+/// OpenWebUI stores errors in a separate 'error' field with 'content' inside.
+/// Returns a map suitable for ChatMessageError.fromJson().
+Map<String, dynamic>? _extractErrorData(
+  Map<String, dynamic> msgData,
+  Map<String, dynamic>? historyMsg,
+) {
+  // Check msgData first, then historyMsg
+  final errorRaw = msgData['error'] ?? historyMsg?['error'];
+  if (errorRaw == null) return null;
+
+  // Handle different error formats from OpenWebUI
+  if (errorRaw is Map) {
+    // Most common: { error: { content: "error message" } }
+    final content = errorRaw['content'];
+    if (content is String && content.isNotEmpty) {
+      return {'content': content};
+    }
+    // Alternative: { error: { message: "error message" } }
+    final message = errorRaw['message'];
+    if (message is String && message.isNotEmpty) {
+      return {'content': message};
+    }
+    // Nested error: { error: { error: { message: "..." } } }
+    final nestedError = errorRaw['error'];
+    if (nestedError is Map) {
+      final nestedMessage = nestedError['message'];
+      if (nestedMessage is String && nestedMessage.isNotEmpty) {
+        return {'content': nestedMessage};
+      }
+    }
+    // FastAPI detail format: { detail: "..." }
+    final detail = errorRaw['detail'];
+    if (detail is String && detail.isNotEmpty) {
+      return {'content': detail};
+    }
+    // If it's a map but we couldn't extract content, still return an error
+    // to indicate there was an error (matches legacy error === true behavior)
+    return const {'content': null};
+  } else if (errorRaw is String && errorRaw.isNotEmpty) {
+    // Simple string error
+    return {'content': errorRaw};
+  } else if (errorRaw == true) {
+    // Legacy format: error === true means content IS the error message
+    // Return a marker so the UI knows this is an error message
+    return const {'content': null};
+  }
+
+  return null;
+}
+
 Map<String, dynamic> _parseOpenWebUIMessageToJson(
   Map<String, dynamic> msgData, {
   Map<String, dynamic>? historyMsg,
@@ -253,6 +304,9 @@ Map<String, dynamic> _parseOpenWebUIMessageToJson(
     }
   }
 
+  // Extract error field from OpenWebUI - preserve it separately for round-trip
+  final errorData = _extractErrorData(msgData, historyMsg);
+
   final role = _resolveRole(msgData);
 
   final effectiveFiles = msgData['files'] ?? historyMsg?['files'];
@@ -325,6 +379,7 @@ Map<String, dynamic> _parseOpenWebUIMessageToJson(
     'sources': _parseSourcesField(sourcesRaw),
     'usage': usage,
     'versions': const <Map<String, dynamic>>[],
+    if (errorData != null) 'error': errorData,
   };
 }
 

lib/core/services/streaming_helper.dart

@@ -1126,34 +1126,33 @@ ActiveSocketStream attachUnifiedChunkedStreaming({
         // Server reports an error for the current assistant message
         try {
           dynamic err = payload is Map ? payload['error'] : null;
-          String content = '';
+          String errorContent = '';
           if (err is Map) {
             final c = err['content'];
             if (c is String) {
-              content = c;
+              errorContent = c;
             } else if (c != null) {
-              content = c.toString();
+              errorContent = c.toString();
             }
           } else if (err is String) {
-            content = err;
+            errorContent = err;
           } else if (payload is Map && payload['message'] is String) {
-            content = payload['message'];
-          }
-          if (content.isNotEmpty) {
-            // Replace current assistant message with a readable error
-            replaceLastMessageContent('⚠️ $content');
+            errorContent = payload['message'];
           }
+          // Set the error field on the message for proper OpenWebUI round-trip
+          // Also drop search-only status rows so the error feels cleaner
+          updateLastMessageWith((message) {
+            final filtered = message.statusHistory
+                .where((status) => status.action != 'knowledge_search')
+                .toList(growable: false);
+            return message.copyWith(
+              error: errorContent.isNotEmpty
+                  ? ChatMessageError(content: errorContent)
+                  : const ChatMessageError(content: null),
+              statusHistory: filtered,
+            );
+          });
         } catch (_) {}
-        // Drop search-only status rows so the error feels cleaner
-        updateLastMessageWith((message) {
-          final filtered = message.statusHistory
-              .where((status) => status.action != 'knowledge_search')
-              .toList(growable: false);
-          if (filtered.length == message.statusHistory.length) {
-            return message;
-          }
-          return message.copyWith(statusHistory: filtered);
-        });
         // Ensure UI exits streaming state
         wrappedFinishStreaming();
       } else if ((type == 'chat:message:delta' || type == 'message') &&