Improve chat rendering

package-lock.json

@@ -12,7 +12,8 @@
         "@fastify/websocket": "^11.2.0",
         "@mariozechner/pi-coding-agent": "^0.73.0",
         "fastify": "^5.6.1",
-        "lit": "^3.3.1"
+        "lit": "^3.3.1",
+        "marked": "^18.0.3"
       },
       "devDependencies": {
         "@types/node": "^24.10.1",
@@ -1825,6 +1826,18 @@
         "url": "https://github.com/sponsors/isaacs"
       }
     },
+    "node_modules/@mariozechner/pi-coding-agent/node_modules/marked": {
+      "version": "15.0.12",
+      "resolved": "https://registry.npmjs.org/marked/-/marked-15.0.12.tgz",
+      "integrity": "sha512-8dD6FusOQSrpv9Z1rdNMdlSgQOIP880DHqnohobOmYLElGEqAL/JvxvuxZO16r4HtjTlfPRDC1hbvxC9dPN2nA==",
+      "license": "MIT",
+      "bin": {
+        "marked": "bin/marked.js"
+      },
+      "engines": {
+        "node": ">= 18"
+      }
+    },
     "node_modules/@mariozechner/pi-tui": {
       "version": "0.73.0",
       "resolved": "https://registry.npmjs.org/@mariozechner/pi-tui/-/pi-tui-0.73.0.tgz",
@@ -1844,6 +1857,18 @@
         "koffi": "^2.9.0"
       }
     },
+    "node_modules/@mariozechner/pi-tui/node_modules/marked": {
+      "version": "15.0.12",
+      "resolved": "https://registry.npmjs.org/marked/-/marked-15.0.12.tgz",
+      "integrity": "sha512-8dD6FusOQSrpv9Z1rdNMdlSgQOIP880DHqnohobOmYLElGEqAL/JvxvuxZO16r4HtjTlfPRDC1hbvxC9dPN2nA==",
+      "license": "MIT",
+      "bin": {
+        "marked": "bin/marked.js"
+      },
+      "engines": {
+        "node": ">= 18"
+      }
+    },
     "node_modules/@mistralai/mistralai": {
       "version": "2.2.1",
       "resolved": "https://registry.npmjs.org/@mistralai/mistralai/-/mistralai-2.2.1.tgz",
@@ -4389,15 +4414,15 @@
       }
     },
     "node_modules/marked": {
-      "version": "15.0.12",
+      "version": "18.0.3",
-      "resolved": "https://registry.npmjs.org/marked/-/marked-15.0.12.tgz",
+      "resolved": "https://registry.npmjs.org/marked/-/marked-18.0.3.tgz",
-      "integrity": "sha512-8dD6FusOQSrpv9Z1rdNMdlSgQOIP880DHqnohobOmYLElGEqAL/JvxvuxZO16r4HtjTlfPRDC1hbvxC9dPN2nA==",
+      "integrity": "sha512-7VT90JOkDeaRWpfjOReRGPEKn0ecdARBkDGL+tT1wZY0efPPqkUxLUSmzy/C7TIylQYJC9STISEsCHrqb/7VIA==",
       "license": "MIT",
       "bin": {
         "marked": "bin/marked.js"
       },
       "engines": {
-        "node": ">= 18"
+        "node": ">= 20"
       }
     },
     "node_modules/mime": {

package.json

@@ -15,7 +15,8 @@
     "@fastify/websocket": "^11.2.0",
     "@mariozechner/pi-coding-agent": "^0.73.0",
     "fastify": "^5.6.1",
-    "lit": "^3.3.1"
+    "lit": "^3.3.1",
+    "marked": "^18.0.3"
   },
   "devDependencies": {
     "@types/node": "^24.10.1",

src/client/src/chatMessages.ts

@@ -0,0 +1,76 @@
+import type { ChatLine, ChatPart } from "./components/shared";
+
+export function normalizeMessages(messages: any[]): ChatLine[] {
+  return messages.flatMap(normalizeMessage).filter((message) => message.parts.length > 0);
+}
+
+export function textMessage(role: ChatLine["role"], text: string): ChatLine {
+  return { role, parts: [{ type: "text", text }] };
+}
+
+export function appendText(messages: ChatLine[], role: ChatLine["role"], text: string): ChatLine[] {
+  const last = messages.at(-1);
+  const lastPart = last?.parts.at(-1);
+  if (last?.role === role && lastPart?.type === "text") {
+    return [
+      ...messages.slice(0, -1),
+      { ...last, parts: [...last.parts.slice(0, -1), { ...lastPart, text: lastPart.text + text }] },
+    ];
+  }
+  return [...messages, textMessage(role, text)];
+}
+
+function normalizeMessage(message: any): ChatLine[] {
+  const role = normalizeRole(message?.role);
+  const parts = normalizeContent(message?.content, message);
+  if (role === "tool") return [{ role, parts }];
+
+  const visible = parts.filter((part) => part.type !== "empty");
+  return visible.length ? [{ role, parts: visible }] : [];
+}
+
+function normalizeRole(role: unknown): ChatLine["role"] {
+  if (role === "assistant") return "assistant";
+  if (role === "user") return "user";
+  if (role === "toolResult") return "tool";
+  return "system";
+}
+
+function normalizeContent(content: unknown, message: any): ChatPart[] {
+  if (typeof content === "string") return content ? [{ type: "text", text: content }] : [];
+  if (!Array.isArray(content)) return objectFallback(content);
+
+  return content.flatMap((part: any): ChatPart[] => {
+    if (part?.type === "text") return part.text ? [{ type: "text", text: part.text }] : [];
+    if (part?.type === "thinking") return part.thinking || part.text ? [{ type: "thinking", text: part.thinking ?? part.text }] : [];
+    if (part?.type === "toolCall") return [{ type: "toolCall", toolName: part.name ?? "tool", summary: summarizeArgs(part.arguments) }];
+    if (part?.type === "image") return [{ type: "text", text: "[image]" }];
+    return objectFallback(part);
+  }).map((part) => part.type === "text" && message?.role === "toolResult"
+    ? { type: "toolResult", toolName: message.toolName ?? "tool", text: part.text, isError: !!message.isError }
+    : part);
+}
+
+function objectFallback(value: unknown): ChatPart[] {
+  if (value == null) return [];
+  if (typeof value === "object") return [{ type: "text", text: summarizeArgs(value) }];
+  return [{ type: "text", text: String(value) }];
+}
+
+function summarizeArgs(args: any): string {
+  if (!args || typeof args !== "object") return args == null ? "" : String(args);
+  if (typeof args.command === "string") return args.command;
+  if (typeof args.path === "string") return args.path;
+  if (typeof args.oldText === "string" && typeof args.newText === "string") return "edit text replacement";
+  if (Array.isArray(args.edits)) return `${args.edits.length} edit${args.edits.length === 1 ? "" : "s"}`;
+  const entries = Object.entries(args).filter(([, value]) => value != null).slice(0, 3);
+  return entries.map(([key, value]) => `${key}: ${shortValue(value)}`).join(" · ");
+}
+
+function shortValue(value: unknown): string {
+  if (typeof value === "string") return value.length > 80 ? `${value.slice(0, 77)}…` : value;
+  if (typeof value === "number" || typeof value === "boolean") return String(value);
+  if (Array.isArray(value)) return `${value.length} item${value.length === 1 ? "" : "s"}`;
+  if (typeof value === "object" && value) return "object";
+  return "";
+}

src/client/src/components/ChatView.ts

@@ -1,19 +1,63 @@
 import { LitElement, html } from "lit";
-import { customElement, property } from "lit/decorators.js";
+import { customElement, property, query, state } from "lit/decorators.js";
-import type { ChatLine } from "./shared";
+import type { ChatLine, ChatPart } from "./shared";
 import { chatStyles } from "./shared";
+import "./FormattedText";
 
 @customElement("chat-view")
 export class ChatView extends LitElement {
   @property({ attribute: false }) messages: ChatLine[] = [];
+  @query(".chat") private chat?: HTMLDivElement;
+  @state() private pinnedToBottom = true;
+
+  protected willUpdate(): void {
+    this.pinnedToBottom = this.isNearBottom();
+  }
+
+  protected updated(): void {
+    if (this.pinnedToBottom) this.scrollToBottom();
+  }
 
   render() {
     return html`
-      <div class="chat">
+      <div class="chat" @scroll=${this.onScroll}>
-        ${this.messages.map((message) => html`<div class="msg ${message.role}"><b>${message.role}</b><pre>${message.text}</pre></div>`)}
+        ${this.messages.map((message) => html`
+          <article class="msg ${message.role}">
+            <b class="label">${message.role}</b>
+            ${message.parts.map((part) => this.renderPart(part))}
+          </article>
+        `)}
       </div>
     `;
   }
 
+  private renderPart(part: ChatPart) {
+    if (part.type === "text") return html`<formatted-text class="part" .text=${part.text}></formatted-text>`;
+    if (part.type === "thinking") return html`<details class="part"><summary>thinking</summary><formatted-text .text=${part.text}></formatted-text></details>`;
+    if (part.type === "toolCall") return html`<div class="part tool-line">▶ ${part.toolName}<span class="summary">${part.summary}</span></div>`;
+    if (part.type === "toolResult") return html`
+      <details class="part" ?open=${part.isError}>
+        <summary>${part.isError ? "✖" : "✓"} ${part.toolName} result</summary>
+        <formatted-text .text=${part.text}></formatted-text>
+      </details>
+    `;
+    return null;
+  }
+
+  private onScroll() {
+    this.pinnedToBottom = this.isNearBottom();
+  }
+
+  private isNearBottom(): boolean {
+    const chat = this.chat;
+    if (!chat) return true;
+    return chat.scrollHeight - chat.scrollTop - chat.clientHeight < 48;
+  }
+
+  private scrollToBottom() {
+    const chat = this.chat;
+    if (chat) chat.scrollTop = chat.scrollHeight;
+  }
+
   static styles = chatStyles;
 }

src/client/src/components/FormattedText.ts

@@ -0,0 +1,55 @@
+import { LitElement, html } from "lit";
+import { customElement, property } from "lit/decorators.js";
+import { unsafeHTML } from "lit/directives/unsafe-html.js";
+import { marked } from "marked";
+import { formattedTextStyles } from "./shared";
+
+@customElement("formatted-text")
+export class FormattedText extends LitElement {
+  @property() text = "";
+
+  render() {
+    return html`<div class="formatted">${unsafeHTML(toSafeMarkdownHtml(this.text))}</div>`;
+  }
+
+  static styles = formattedTextStyles;
+}
+
+function toSafeMarkdownHtml(text: string): string {
+  const html = marked.parse(escapeHtml(text), { async: false, breaks: true, gfm: true }) as string;
+  return sanitizeHtml(html);
+}
+
+function escapeHtml(text: string): string {
+  return text
+    .replaceAll("&", "&amp;")
+    .replaceAll("<", "&lt;")
+    .replaceAll(">", "&gt;");
+}
+
+function sanitizeHtml(html: string): string {
+  const template = document.createElement("template");
+  template.innerHTML = html;
+  template.content.querySelectorAll("script, style, iframe, object, embed").forEach((node) => node.remove());
+  template.content.querySelectorAll("*").forEach((element) => {
+    for (const attribute of [...element.attributes]) {
+      const name = attribute.name.toLowerCase();
+      if (name.startsWith("on")) element.removeAttribute(attribute.name);
+      if ((name === "href" || name === "src") && !isSafeUrl(attribute.value)) element.removeAttribute(attribute.name);
+    }
+    if (element.tagName === "A") {
+      element.setAttribute("target", "_blank");
+      element.setAttribute("rel", "noreferrer noopener");
+    }
+  });
+  return template.innerHTML;
+}
+
+function isSafeUrl(url: string): boolean {
+  if (url.startsWith("#") || url.startsWith("/")) return true;
+  try {
+    return ["http:", "https:", "mailto:"].includes(new URL(url).protocol);
+  } catch {
+    return false;
+  }
+}

src/client/src/components/PiWebApp.ts

@@ -8,6 +8,7 @@ import "./WorkspaceList";
 import "./SessionList";
 import "./ChatView";
 import "./Composer";
+import { normalizeMessages, appendText, textMessage } from "../chatMessages";
 import { appStyles, type ChatLine } from "./shared";
 
 @customElement("pi-web-poc")
@@ -112,23 +113,19 @@ export class PiWebApp extends LitElement {
 
   private applyEvent(event: SessionUiEvent) {
     if (event.type === "assistant.delta") {
-      const lines = [...this.messages];
+      this.messages = appendText(this.messages, "assistant", event.text);
-      const last = lines.at(-1);
-      if (last?.role === "assistant") last.text += event.text;
-      else lines.push({ role: "assistant", text: event.text });
-      this.messages = lines;
     } else if (event.type === "tool.start") {
-      this.messages = [...this.messages, { role: "tool", text: `▶ ${event.toolName}` }];
+      this.messages = [...this.messages, { role: "tool", parts: [{ type: "toolCall", toolName: event.toolName, summary: "" }] }];
     } else if (event.type === "tool.end") {
-      this.messages = [...this.messages, { role: "tool", text: `${event.isError ? "✖" : "✓"} ${event.toolName}` }];
+      this.messages = [...this.messages, textMessage("tool", `${event.isError ? "✖" : "✓"} ${event.toolName}`)];
     } else if (event.type === "session.error") {
-      this.messages = [...this.messages, { role: "system", text: event.message }];
+      this.messages = [...this.messages, textMessage("system", event.message)];
     }
   }
 
   private async send(text: string) {
     if (!this.selectedSession) return;
-    this.messages = [...this.messages, { role: "user", text }];
+    this.messages = [...this.messages, textMessage("user", text)];
     try {
       await api.prompt(this.selectedSession.id, text);
     } catch (error) {
@@ -182,10 +179,3 @@ export class PiWebApp extends LitElement {
 
   static styles = appStyles;
 }
-
-function normalizeMessages(messages: any[]): ChatLine[] {
-  return messages.map((message) => ({
-    role: message.role === "assistant" ? "assistant" : message.role === "user" ? "user" : "system",
-    text: typeof message.content === "string" ? message.content : JSON.stringify(message.content, null, 2),
-  }));
-}

src/client/src/components/shared.ts

@@ -1,8 +1,15 @@
 import { css } from "lit";
 
+export type ChatPart =
+  | { type: "text"; text: string }
+  | { type: "thinking"; text: string }
+  | { type: "toolCall"; toolName: string; summary: string }
+  | { type: "toolResult"; toolName: string; text: string; isError: boolean }
+  | { type: "empty" };
+
 export interface ChatLine {
   role: "user" | "assistant" | "tool" | "system";
-  text: string;
+  parts: ChatPart[];
 }
 
 export const appStyles = css`
@@ -35,12 +42,42 @@ export const chatStyles = css`
   :host { display: block; min-height: 0; color: #e6edf3; font: 14px system-ui, sans-serif; }
   .chat { height: 100%; overflow: auto; padding: 16px; box-sizing: border-box; }
   .msg { margin: 0 0 14px; padding: 12px; border: 1px solid #30363d; border-radius: 10px; background: #161b22; }
-  .msg.user { border-color: #2f81f7; }
+  .msg.user { border-color: #2f81f7; background: #0d2847; }
-  .msg.tool { color: #d29922; }
+  .msg.tool { border-color: #6e5200; background: #1f1a10; color: #d29922; }
   .msg.system { color: #ff7b72; }
+  .label { display: block; margin-bottom: 8px; color: #8b949e; font-size: 12px; text-transform: uppercase; }
+  formatted-text.part { display: block; }
+  .part + .part { margin-top: 10px; }
+  .tool-line { color: #d29922; }
+  .summary { color: #8b949e; margin-left: 6px; }
+  details { border-top: 1px solid #30363d; padding-top: 8px; }
+  summary { cursor: pointer; color: #8b949e; }
   pre { margin: 6px 0 0; white-space: pre-wrap; overflow-wrap: anywhere; font: inherit; }
 `;
 
+export const formattedTextStyles = css`
+  :host { display: block; }
+  .formatted { white-space: normal; overflow-wrap: anywhere; line-height: 1.45; }
+  p, ul, ol, pre, blockquote, table { margin: 0 0 10px; }
+  :is(p, ul, ol, pre, blockquote, table):last-child { margin-bottom: 0; }
+  ul, ol { padding-left: 22px; }
+  li + li { margin-top: 3px; }
+  code { border: 1px solid #30363d; border-radius: 4px; background: #0d1117; padding: 1px 4px; font: 13px ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; }
+  pre { border: 1px solid #30363d; border-radius: 8px; background: #0d1117; padding: 10px; overflow: auto; }
+  pre code { border: 0; padding: 0; background: transparent; }
+  blockquote { border-left: 3px solid #30363d; padding-left: 10px; color: #8b949e; }
+  a { color: #58a6ff; }
+  h1, h2, h3, h4 { margin: 14px 0 8px; line-height: 1.2; }
+  h1:first-child, h2:first-child, h3:first-child, h4:first-child { margin-top: 0; }
+  h1 { font-size: 20px; }
+  h2 { font-size: 17px; }
+  h3 { font-size: 15px; }
+  h4 { font-size: 14px; }
+  table { border-collapse: collapse; display: block; overflow: auto; }
+  th, td { border: 1px solid #30363d; padding: 4px 8px; }
+  th { background: #161b22; }
+`;
+
 export const composerStyles = css`
   :host { display: block; color: #e6edf3; font: 14px system-ui, sans-serif; }
   footer { display: grid; grid-template-columns: 1fr auto auto; gap: 8px; padding: 12px; border-top: 1px solid #30363d; }