fix(ui): cache control ui markdown

CHANGELOG.md

@@ -17,6 +17,7 @@ Docs: https://docs.clawd.bot
 - Docker: update gateway command in docker-compose and Hetzner guide. (#1514)
 - Voice wake: auto-save wake words on blur/submit across iOS/Android and align limits with macOS.
 - UI: keep the Control UI sidebar visible while scrolling long pages. (#1515) Thanks @pookNast.
+- UI: cache Control UI markdown rendering + memoize chat text extraction to reduce Safari typing jank.
 - Tailscale: retry serve/funnel with sudo only for permission errors and keep original failure details. (#1551) Thanks @sweepies.
 - Agents: add CLI log hint to "agent failed before reply" messages. (#1550) Thanks @sweepies.
 - Discord: limit autoThread mention bypass to bot-owned threads; keep ack reactions mention-gated. (#1511) Thanks @pvoo.

ui/src/ui/chat/grouped-render.ts

@@ -7,8 +7,8 @@ import type { MessageGroup } from "../types/chat-types";
 import { renderCopyAsMarkdownButton } from "./copy-as-markdown";
 import { isToolResultMessage, normalizeRoleForGrouping } from "./message-normalizer";
 import {
-  extractText,
-  extractThinking,
+  extractTextCached,
+  extractThinkingCached,
   formatReasoningMarkdown,
 } from "./message-extract";
 import { extractToolCards, renderToolCardSidebar } from "./tool-cards";
@@ -180,9 +180,11 @@ function renderGroupedMessage(
   const toolCards = extractToolCards(message);
   const hasToolCards = toolCards.length > 0;
 
-  const extractedText = extractText(message);
+  const extractedText = extractTextCached(message);
   const extractedThinking =
-    opts.showReasoning && role === "assistant" ? extractThinking(message) : null;
+    opts.showReasoning && role === "assistant"
+      ? extractThinkingCached(message)
+      : null;
   const markdownBase = extractedText?.trim() ? extractedText : null;
   const reasoningMarkdown = extractedThinking
     ? formatReasoningMarkdown(extractedThinking)

ui/src/ui/chat/message-extract.test.ts

@@ -1,34 +1,46 @@
 import { describe, expect, it } from "vitest";
-import { stripEnvelope } from "./message-extract";
 
-describe("stripEnvelope", () => {
-  it("strips UTC envelope", () => {
-    const text = "[WebChat agent:main:main 2026-01-18T05:19Z] hello world";
-    expect(stripEnvelope(text)).toBe("hello world");
+import {
+  extractText,
+  extractTextCached,
+  extractThinking,
+  extractThinkingCached,
+} from "./message-extract";
+
+describe("extractTextCached", () => {
+  it("matches extractText output", () => {
+    const message = {
+      role: "assistant",
+      content: [{ type: "text", text: "Hello there" }],
+    };
+    expect(extractTextCached(message)).toBe(extractText(message));
   });
 
-  it("strips local-time envelope", () => {
-    const text = "[Telegram Ada Lovelace (@ada) id:1234 2026-01-18 19:29 GMT+1] test";
-    expect(stripEnvelope(text)).toBe("test");
+  it("returns consistent output for repeated calls", () => {
+    const message = {
+      role: "user",
+      content: "plain text",
+    };
+    expect(extractTextCached(message)).toBe("plain text");
+    expect(extractTextCached(message)).toBe("plain text");
+  });
 });
 
-  it("strips envelopes without timestamps for known channels", () => {
-    const text = "[WhatsApp +1234567890] hi there";
-    expect(stripEnvelope(text)).toBe("hi there");
+describe("extractThinkingCached", () => {
+  it("matches extractThinking output", () => {
+    const message = {
+      role: "assistant",
+      content: [{ type: "thinking", thinking: "Plan A" }],
+    };
+    expect(extractThinkingCached(message)).toBe(extractThinking(message));
   });
 
-  it("handles multi-line messages", () => {
-    const text = "[Slack #general 2026-01-18T05:19Z] first line\nsecond line";
-    expect(stripEnvelope(text)).toBe("first line\nsecond line");
-  });
-
-  it("returns text as-is when no envelope present", () => {
-    const text = "just a regular message";
-    expect(stripEnvelope(text)).toBe("just a regular message");
-  });
-
-  it("does not strip non-envelope brackets", () => {
-    expect(stripEnvelope("[OK] hello")).toBe("[OK] hello");
-    expect(stripEnvelope("[1/2] step one")).toBe("[1/2] step one");
+  it("returns consistent output for repeated calls", () => {
+    const message = {
+      role: "assistant",
+      content: [{ type: "thinking", thinking: "Plan A" }],
+    };
+    expect(extractThinkingCached(message)).toBe("Plan A");
+    expect(extractThinkingCached(message)).toBe("Plan A");
   });
 });

ui/src/ui/chat/message-extract.ts

@@ -16,6 +16,9 @@ const ENVELOPE_CHANNELS = [
   "BlueBubbles",
 ];
 
+const textCache = new WeakMap<object, string | null>();
+const thinkingCache = new WeakMap<object, string | null>();
+
 function looksLikeEnvelopeHeader(header: string): boolean {
   if (/\d{4}-\d{2}-\d{2}T\d{2}:\d{2}Z\b/.test(header)) return true;
   if (/\d{4}-\d{2}-\d{2} \d{2}:\d{2}\b/.test(header)) return true;
@@ -59,6 +62,15 @@ export function extractText(message: unknown): string | null {
   return null;
 }
 
+export function extractTextCached(message: unknown): string | null {
+  if (!message || typeof message !== "object") return extractText(message);
+  const obj = message as object;
+  if (textCache.has(obj)) return textCache.get(obj) ?? null;
+  const value = extractText(message);
+  textCache.set(obj, value);
+  return value;
+}
+
 export function extractThinking(message: unknown): string | null {
   const m = message as Record<string, unknown>;
   const content = m.content;
@@ -88,6 +100,15 @@ export function extractThinking(message: unknown): string | null {
   return extracted.length > 0 ? extracted.join("\n") : null;
 }
 
+export function extractThinkingCached(message: unknown): string | null {
+  if (!message || typeof message !== "object") return extractThinking(message);
+  const obj = message as object;
+  if (thinkingCache.has(obj)) return thinkingCache.get(obj) ?? null;
+  const value = extractThinking(message);
+  thinkingCache.set(obj, value);
+  return value;
+}
+
 export function extractRawText(message: unknown): string | null {
   const m = message as Record<string, unknown>;
   const content = m.content;

ui/src/ui/chat/tool-cards.ts

@@ -8,7 +8,7 @@ import {
   getTruncatedPreview,
 } from "./tool-helpers";
 import { isToolResultMessage } from "./message-normalizer";
-import { extractText } from "./message-extract";
+import { extractTextCached } from "./message-extract";
 
 export function extractToolCards(message: unknown): ToolCard[] {
   const m = message as Record<string, unknown>;
@@ -45,7 +45,7 @@ export function extractToolCards(message: unknown): ToolCard[] {
       (typeof m.toolName === "string" && m.toolName) ||
       (typeof m.tool_name === "string" && m.tool_name) ||
       "tool";
-    const text = extractText(message) ?? undefined;
+    const text = extractTextCached(message) ?? undefined;
     cards.push({ kind: "result", name, text });
   }
 

ui/src/ui/markdown.ts

@@ -41,6 +41,24 @@ const allowedAttrs = ["class", "href", "rel", "target", "title", "start"];
 let hooksInstalled = false;
 const MARKDOWN_CHAR_LIMIT = 140_000;
 const MARKDOWN_PARSE_LIMIT = 40_000;
+const MARKDOWN_CACHE_LIMIT = 200;
+const MARKDOWN_CACHE_MAX_CHARS = 50_000;
+const markdownCache = new Map<string, string>();
+
+function getCachedMarkdown(key: string): string | null {
+  const cached = markdownCache.get(key);
+  if (cached === undefined) return null;
+  markdownCache.delete(key);
+  markdownCache.set(key, cached);
+  return cached;
+}
+
+function setCachedMarkdown(key: string, value: string) {
+  markdownCache.set(key, value);
+  if (markdownCache.size <= MARKDOWN_CACHE_LIMIT) return;
+  const oldest = markdownCache.keys().next().value;
+  if (oldest) markdownCache.delete(oldest);
+}
 
 function installHooks() {
   if (hooksInstalled) return;
@@ -59,6 +77,10 @@ export function toSanitizedMarkdownHtml(markdown: string): string {
   const input = markdown.trim();
   if (!input) return "";
   installHooks();
+  if (input.length <= MARKDOWN_CACHE_MAX_CHARS) {
+    const cached = getCachedMarkdown(input);
+    if (cached !== null) return cached;
+  }
   const truncated = truncateText(input, MARKDOWN_CHAR_LIMIT);
   const suffix = truncated.truncated
     ? `\n\n… truncated (${truncated.total} chars, showing first ${truncated.text.length}).`
@@ -66,16 +88,24 @@ export function toSanitizedMarkdownHtml(markdown: string): string {
   if (truncated.text.length > MARKDOWN_PARSE_LIMIT) {
     const escaped = escapeHtml(`${truncated.text}${suffix}`);
     const html = `<pre class="code-block">${escaped}</pre>`;
-    return DOMPurify.sanitize(html, {
+    const sanitized = DOMPurify.sanitize(html, {
       ALLOWED_TAGS: allowedTags,
       ALLOWED_ATTR: allowedAttrs,
     });
+    if (input.length <= MARKDOWN_CACHE_MAX_CHARS) {
+      setCachedMarkdown(input, sanitized);
+    }
+    return sanitized;
   }
   const rendered = marked.parse(`${truncated.text}${suffix}`) as string;
-  return DOMPurify.sanitize(rendered, {
+  const sanitized = DOMPurify.sanitize(rendered, {
     ALLOWED_TAGS: allowedTags,
     ALLOWED_ATTR: allowedAttrs,
   });
+  if (input.length <= MARKDOWN_CACHE_MAX_CHARS) {
+    setCachedMarkdown(input, sanitized);
+  }
+  return sanitized;
 }
 
 function escapeHtml(value: string): string {

ui/src/ui/views/chat.ts

@@ -1,4 +1,5 @@
 import { html, nothing } from "lit";
+import { guard } from "lit/directives/guard.js";
 import { repeat } from "lit/directives/repeat.js";
 import type { SessionsListResult } from "../types";
 import type { ChatQueueItem } from "../ui-types";
@@ -7,7 +8,7 @@ import {
   normalizeMessage,
   normalizeRoleForGrouping,
 } from "../chat/message-normalizer";
-import { extractText } from "../chat/message-extract";
+import { extractTextCached } from "../chat/message-extract";
 import {
   renderMessageGroup,
   renderReadingIndicatorGroup,
@@ -114,6 +115,56 @@ export function renderChat(props: ChatProps) {
 
   const splitRatio = props.splitRatio ?? 0.6;
   const sidebarOpen = Boolean(props.sidebarOpen && props.onCloseSidebar);
+  const thread = guard(
+    [
+      props.loading,
+      props.messages,
+      props.toolMessages,
+      props.stream,
+      props.streamStartedAt,
+      props.sessionKey,
+      props.showThinking,
+      reasoningLevel,
+      props.assistantName,
+      props.assistantAvatar,
+      props.assistantAvatarUrl,
+    ],
+    () => html`
+      <div
+        class="chat-thread"
+        role="log"
+        aria-live="polite"
+        @scroll=${props.onChatScroll}
+      >
+        ${props.loading ? html`<div class="muted">Loading chat…</div>` : nothing}
+        ${repeat(buildChatItems(props), (item) => item.key, (item) => {
+          if (item.kind === "reading-indicator") {
+            return renderReadingIndicatorGroup(assistantIdentity);
+          }
+
+          if (item.kind === "stream") {
+            return renderStreamingGroup(
+              item.text,
+              item.startedAt,
+              props.onOpenSidebar,
+              assistantIdentity,
+            );
+          }
+
+          if (item.kind === "group") {
+            return renderMessageGroup(item, {
+              onOpenSidebar: props.onOpenSidebar,
+              showReasoning,
+              assistantName: props.assistantName,
+              assistantAvatar: assistantIdentity.avatar,
+            });
+          }
+
+          return nothing;
+        })}
+      </div>
+    `,
+  );
 
   return html`
     <section class="card chat">
@@ -148,41 +199,7 @@ export function renderChat(props: ChatProps) {
           class="chat-main"
           style="flex: ${sidebarOpen ? `0 0 ${splitRatio * 100}%` : "1 1 100%"}"
         >
-          <div
-            class="chat-thread"
-            role="log"
-            aria-live="polite"
-            @scroll=${props.onChatScroll}
-          >
-            ${props.loading
-              ? html`<div class="muted">Loading chat…</div>`
-              : nothing}
-            ${repeat(buildChatItems(props), (item) => item.key, (item) => {
-              if (item.kind === "reading-indicator") {
-                return renderReadingIndicatorGroup(assistantIdentity);
-              }
-
-              if (item.kind === "stream") {
-                return renderStreamingGroup(
-                  item.text,
-                  item.startedAt,
-                  props.onOpenSidebar,
-                  assistantIdentity,
-                );
-              }
-
-              if (item.kind === "group") {
-                return renderMessageGroup(item, {
-                  onOpenSidebar: props.onOpenSidebar,
-                  showReasoning,
-                  assistantName: props.assistantName,
-                  assistantAvatar: assistantIdentity.avatar,
-                });
-              }
-
-              return nothing;
-            })}
-          </div>
+          ${thread}
         </div>
 
         ${sidebarOpen
@@ -379,7 +396,8 @@ function messageKey(message: unknown, index: number): string {
   const timestamp = typeof m.timestamp === "number" ? m.timestamp : null;
   const role = typeof m.role === "string" ? m.role : "unknown";
   const fingerprint =
-    extractText(message) ?? (typeof m.content === "string" ? m.content : null);
+    extractTextCached(message) ??
+    (typeof m.content === "string" ? m.content : null);
   const seed = fingerprint ?? safeJson(message) ?? String(index);
   const hash = fnv1a(seed);
   return timestamp ? `msg:${role}:${timestamp}:${hash}` : `msg:${role}:${hash}`;