diff --git a/tools/server/webui/src/lib/services/chat.service.ts b/tools/server/webui/src/lib/services/chat.service.ts
index ee575c42cf..e17160fedd 100644
--- a/tools/server/webui/src/lib/services/chat.service.ts
+++ b/tools/server/webui/src/lib/services/chat.service.ts
@@ -1,7 +1,7 @@
 import { getJsonHeaders, formatAttachmentText, isAbortError } from '$lib/utils';
 import { AGENTIC_REGEX } from '$lib/constants/agentic';
 import { AttachmentType, MessageRole, ReasoningFormat } from '$lib/enums';
-import type { ApiChatMessageContentPart } from '$lib/types/api';
+import type { ApiChatMessageContentPart, ApiChatCompletionToolCall } from '$lib/types/api';
 import type { DatabaseMessageExtraMcpPrompt } from '$lib/types';
 
 /**
@@ -634,11 +634,34 @@ export class ChatService {
 	static convertDbMessageToApiChatMessageData(
 		message: DatabaseMessage & { extra?: DatabaseMessageExtra[] }
 	): ApiChatMessageData {
-		if (!message.extra || message.extra.length === 0) {
+		// Handle tool result messages (role: 'tool')
+		if (message.role === MessageRole.TOOL && message.toolCallId) {
 			return {
+				role: MessageRole.TOOL,
+				content: message.content,
+				tool_call_id: message.toolCallId
+			};
+		}
+
+		// Parse tool calls for assistant messages
+		let toolCalls: ApiChatCompletionToolCall[] | undefined;
+		if (message.toolCalls) {
+			try {
+				toolCalls = JSON.parse(message.toolCalls);
+			} catch {
+				// Ignore parse errors for malformed tool calls
+			}
+		}
+
+		if (!message.extra || message.extra.length === 0) {
+			const result: ApiChatMessageData = {
 				role: message.role as MessageRole,
 				content: message.content
 			};
+			if (toolCalls && toolCalls.length > 0) {
+				result.tool_calls = toolCalls;
+			}
+			return result;
 		}
 
 		const contentParts: ApiChatMessageContentPart[] = [];
@@ -741,10 +764,14 @@ export class ChatService {
 			});
 		}
 
-		return {
+		const result: ApiChatMessageData = {
 			role: message.role as MessageRole,
 			content: contentParts
 		};
+		if (toolCalls && toolCalls.length > 0) {
+			result.tool_calls = toolCalls;
+		}
+		return result;
 	}
 
 	/**
diff --git a/tools/server/webui/src/lib/types/database.d.ts b/tools/server/webui/src/lib/types/database.d.ts
index 927de3cb74..e4e24a6099 100644
--- a/tools/server/webui/src/lib/types/database.d.ts
+++ b/tools/server/webui/src/lib/types/database.d.ts
@@ -81,7 +81,10 @@ export interface DatabaseMessage {
 	 * @deprecated - left for backward compatibility
 	 */
 	thinking?: string;
+	/** Serialized JSON array of tool calls made by assistant messages */
 	toolCalls?: string;
+	/** Tool call ID for tool result messages (role: 'tool') */
+	toolCallId?: string;
 	children: string[];
 	extra?: DatabaseMessageExtra[];
 	timings?: ChatMessageTimings;