Add defaultConvertToLlm to web-ui, simplify example

- web-ui exports: defaultConvertToLlm, convertAttachments, isUserMessageWithAttachments, isArtifactMessage
- defaultConvertToLlm handles UserMessageWithAttachments and filters ArtifactMessage
- Example's customMessageTransformer now extends defaultConvertToLlm
- Removes duplicated attachment conversion logic from example

packages/web-ui/example/src/custom-messages.ts

@@ -1,7 +1,7 @@
 import { Alert } from "@mariozechner/mini-lit/dist/Alert.js";
-import type { ImageContent, Message, TextContent } from "@mariozechner/pi-ai";
-import type { AgentMessage, Attachment, MessageRenderer, UserMessageWithAttachments } from "@mariozechner/pi-web-ui";
-import { registerMessageRenderer } from "@mariozechner/pi-web-ui";
+import type { Message } from "@mariozechner/pi-ai";
+import type { AgentMessage, MessageRenderer } from "@mariozechner/pi-web-ui";
+import { defaultConvertToLlm, registerMessageRenderer } from "@mariozechner/pi-web-ui";
 import { html } from "lit";
 
 // ============================================================================
@@ -75,72 +75,25 @@ export function createSystemNotification(
 // 5. CUSTOM MESSAGE TRANSFORMER
 // ============================================================================
 
-// Convert attachments to content blocks
-function convertAttachments(attachments: Attachment[]): (TextContent | ImageContent)[] {
-	const content: (TextContent | ImageContent)[] = [];
-	for (const attachment of attachments) {
-		if (attachment.type === "image") {
-			content.push({
-				type: "image",
-				data: attachment.content,
-				mimeType: attachment.mimeType,
-			} as ImageContent);
-		} else if (attachment.type === "document" && attachment.extractedText) {
-			content.push({
-				type: "text",
-				text: `\n\n[Document: ${attachment.fileName}]\n${attachment.extractedText}`,
-			} as TextContent);
-		}
-	}
-	return content;
-}
-
-// Transform custom messages to LLM-compatible messages
+/**
+ * Custom message transformer that extends defaultConvertToLlm.
+ * Handles system-notification messages by converting them to user messages.
+ */
 export function customMessageTransformer(messages: AgentMessage[]): Message[] {
-	return messages
-		.filter((m) => {
-			// Filter out artifact messages - they're for session reconstruction only
-			if (m.role === "artifact") {
-				return false;
-			}
+	// First, handle our custom system-notification type
+	const processed = messages.map((m): AgentMessage => {
+		if (m.role === "system-notification") {
+			const notification = m as SystemNotificationMessage;
+			// Convert to user message with <system> tags
+			return {
+				role: "user",
+				content: `<system>${notification.message}</system>`,
+				timestamp: Date.now(),
+			};
+		}
+		return m;
+	});
 
-			// Keep LLM-compatible messages + custom messages
-			return (
-				m.role === "user" ||
-				m.role === "user-with-attachments" ||
-				m.role === "assistant" ||
-				m.role === "toolResult" ||
-				m.role === "system-notification"
-			);
-		})
-		.map((m) => {
-			// Transform system notifications to user messages
-			if (m.role === "system-notification") {
-				const notification = m as SystemNotificationMessage;
-				return {
-					role: "user",
-					content: `<system>${notification.message}</system>`,
-					timestamp: Date.now(),
-				} as Message;
-			}
-
-			// Convert user-with-attachments to user message with content blocks
-			if (m.role === "user-with-attachments") {
-				const msg = m as UserMessageWithAttachments;
-				const textContent: (TextContent | ImageContent)[] =
-					typeof msg.content === "string" ? [{ type: "text", text: msg.content }] : [...msg.content];
-
-				if (msg.attachments) {
-					textContent.push(...convertAttachments(msg.attachments));
-				}
-
-				return {
-					role: "user",
-					content: textContent,
-					timestamp: msg.timestamp,
-				} as Message;
-			}
-
-			return m as Message;
-		});
+	// Then use defaultConvertToLlm for standard handling
+	return defaultConvertToLlm(processed);
 }

packages/web-ui/example/src/main.ts

@@ -74,8 +74,8 @@ let chatPanel: ChatPanel;
 let agentUnsubscribe: (() => void) | undefined;
 
 const generateTitle = (messages: AgentMessage[]): string => {
-	const firstUserMsg = messages.find((m) => m.role === "user");
-	if (!firstUserMsg || firstUserMsg.role !== "user") return "";
+	const firstUserMsg = messages.find((m) => m.role === "user" || m.role === "user-with-attachments");
+	if (!firstUserMsg || (firstUserMsg.role !== "user" && firstUserMsg.role !== "user-with-attachments")) return "";
 
 	let text = "";
 	const content = firstUserMsg.content;
@@ -98,7 +98,7 @@ const generateTitle = (messages: AgentMessage[]): string => {
 };
 
 const shouldSaveSession = (messages: AgentMessage[]): boolean => {
-	const hasUserMsg = messages.some((m: any) => m.role === "user");
+	const hasUserMsg = messages.some((m: any) => m.role === "user" || m.role === "user-with-attachments");
 	const hasAssistantMsg = messages.some((m: any) => m.role === "assistant");
 	return hasUserMsg && hasAssistantMsg;
 };

packages/web-ui/src/components/MessageList.ts

@@ -50,7 +50,7 @@ export class MessageList extends LitElement {
 			}
 
 			// Fall back to built-in renderers
-			if (msg.role === "user") {
+			if (msg.role === "user" || msg.role === "user-with-attachments") {
 				items.push({
 					key: `msg:${index}`,
 					template: html`<user-message .message=${msg}></user-message>`,

packages/web-ui/src/components/Messages.ts

@@ -285,3 +285,93 @@ export class AbortedMessage extends LitElement {
 		return html`<span class="text-sm text-destructive italic">${i18n("Request aborted")}</span>`;
 	}
 }
+
+// ============================================================================
+// Default Message Transformer
+// ============================================================================
+
+import type { AgentMessage } from "@mariozechner/pi-agent-core";
+import type { Message } from "@mariozechner/pi-ai";
+
+/**
+ * Convert attachments to content blocks for LLM.
+ * - Images become ImageContent blocks
+ * - Documents with extractedText become TextContent blocks with filename header
+ */
+export function convertAttachments(attachments: Attachment[]): (TextContent | ImageContent)[] {
+	const content: (TextContent | ImageContent)[] = [];
+	for (const attachment of attachments) {
+		if (attachment.type === "image") {
+			content.push({
+				type: "image",
+				data: attachment.content,
+				mimeType: attachment.mimeType,
+			} as ImageContent);
+		} else if (attachment.type === "document" && attachment.extractedText) {
+			content.push({
+				type: "text",
+				text: `\n\n[Document: ${attachment.fileName}]\n${attachment.extractedText}`,
+			} as TextContent);
+		}
+	}
+	return content;
+}
+
+/**
+ * Check if a message is a UserMessageWithAttachments.
+ */
+export function isUserMessageWithAttachments(msg: AgentMessage): msg is UserMessageWithAttachments {
+	return (msg as UserMessageWithAttachments).role === "user-with-attachments";
+}
+
+/**
+ * Check if a message is an ArtifactMessage.
+ */
+export function isArtifactMessage(msg: AgentMessage): msg is ArtifactMessage {
+	return (msg as ArtifactMessage).role === "artifact";
+}
+
+/**
+ * Default convertToLlm for web-ui apps.
+ *
+ * Handles:
+ * - UserMessageWithAttachments: converts to user message with content blocks
+ * - ArtifactMessage: filtered out (UI-only, for session reconstruction)
+ * - Standard LLM messages (user, assistant, toolResult): passed through
+ */
+export function defaultConvertToLlm(messages: AgentMessage[]): Message[] {
+	return messages
+		.filter((m) => {
+			// Filter out artifact messages - they're for session reconstruction only
+			if (isArtifactMessage(m)) {
+				return false;
+			}
+			return true;
+		})
+		.map((m): Message | null => {
+			// Convert user-with-attachments to user message with content blocks
+			if (isUserMessageWithAttachments(m)) {
+				const textContent: (TextContent | ImageContent)[] =
+					typeof m.content === "string" ? [{ type: "text", text: m.content }] : [...m.content];
+
+				if (m.attachments) {
+					textContent.push(...convertAttachments(m.attachments));
+				}
+
+				return {
+					role: "user",
+					content: textContent,
+					timestamp: m.timestamp,
+				} as Message;
+			}
+
+			// Pass through standard LLM roles
+			if (m.role === "user" || m.role === "assistant" || m.role === "toolResult") {
+				return m as Message;
+			}
+
+			// Filter out unknown message types
+			return null;
+		})
+		.filter((m): m is Message => m !== null);
+}

packages/web-ui/src/components/StreamingMessageContainer.ts

@@ -74,7 +74,7 @@ export class StreamingMessageContainer extends LitElement {
 		if (msg.role === "toolResult") {
 			// Skip standalone tool result in streaming; the stable list will render paired tool-message
 			return html``;
-		} else if (msg.role === "user") {
+		} else if (msg.role === "user" || msg.role === "user-with-attachments") {
 			// Skip standalone tool result in streaming; the stable list will render it immediiately
 			return html``;
 		} else if (msg.role === "assistant") {

packages/web-ui/src/index.ts

@@ -12,8 +12,16 @@ export { Input } from "./components/Input.js";
 export { MessageEditor } from "./components/MessageEditor.js";
 export { MessageList } from "./components/MessageList.js";
 // Message components
-export type { UserMessageWithAttachments } from "./components/Messages.js";
-export { AssistantMessage, ToolMessage, UserMessage } from "./components/Messages.js";
+export type { ArtifactMessage, UserMessageWithAttachments } from "./components/Messages.js";
+export {
+	AssistantMessage,
+	convertAttachments,
+	defaultConvertToLlm,
+	isArtifactMessage,
+	isUserMessageWithAttachments,
+	ToolMessage,
+	UserMessage,
+} from "./components/Messages.js";
 // Message renderer registry
 export {
 	getMessageRenderer,