diff --git a/src/client/src/components/ChatView.ts b/src/client/src/components/ChatView.ts
index 193c920..ea38527 100644
--- a/src/client/src/components/ChatView.ts
+++ b/src/client/src/components/ChatView.ts
@@ -1,7 +1,7 @@
 import { LitElement, html } from "lit";
 import { customElement, property, query, state } from "lit/decorators.js";
 import { repeat } from "lit/directives/repeat.js";
-import { groupChatMessages, summarizeChatGroup } from "../chatGroups";
+import { groupChatMessages, summarizeChatGroup, type ChatGroup } from "../chatGroups";
 import { capturePrependScrollAnchor, PREPEND_RESTORE_SETTLE_FRAMES, restorePrependScrollAnchor, type PrependScrollAnchor } from "../chatScrollAnchoring";
 import { shouldRequestEarlierMessages } from "../chatHistoryLoading";
 import type { SessionActivity, SessionStatus } from "../api";
@@ -9,6 +9,9 @@ import type { ChatLine, ChatPart } from "./shared";
 import { chatStyles } from "./shared";
 import "./FormattedText";
 
+const shortTimestampFormatter = new Intl.DateTimeFormat(undefined, { month: "short", day: "numeric", hour: "2-digit", minute: "2-digit" });
+const fullTimestampFormatter = new Intl.DateTimeFormat(undefined, { dateStyle: "medium", timeStyle: "medium" });
+
 function isScrollPosition(value: unknown): value is { index?: number; key?: string; offset: number } {
   return typeof value === "object"
     && value !== null
@@ -39,6 +42,13 @@ export class ChatView extends LitElement {
   private suppressScrollSave = false;
   private suppressLoadMoreRequests = false;
   private saveScrollTimer?: number;
+  private loadMoreCheckFrame: number | undefined;
+  private scrollToBottomFrame: number | undefined;
+  private groupedMessagesInput?: ChatLine[];
+  private groupedMessagesStart = 0;
+  private groupedMessagesCache: ChatGroup[] = [];
+  private readonly messageMetaCache = new WeakMap<ChatLine, { short: string; full: string }>();
+  private readonly messageCopyTextCache = new WeakMap<ChatLine, string>();
   private lastScrollTop = 0;
   private lastClientHeight = 0;
   private touchStartY: number | undefined;
@@ -60,6 +70,8 @@ export class ChatView extends LitElement {
 
   override disconnectedCallback(): void {
     window.clearTimeout(this.saveScrollTimer);
+    if (this.loadMoreCheckFrame !== undefined) cancelAnimationFrame(this.loadMoreCheckFrame);
+    if (this.scrollToBottomFrame !== undefined) cancelAnimationFrame(this.scrollToBottomFrame);
     window.removeEventListener("resize", this.onViewportResize);
     window.visualViewport?.removeEventListener("resize", this.onViewportResize);
     super.disconnectedCallback();
@@ -90,7 +102,7 @@ export class ChatView extends LitElement {
         <div class="chat" @scroll=${() => { this.onScroll(); }} @wheel=${(event: WheelEvent) => { this.onWheel(event); }} @touchstart=${(event: TouchEvent) => { this.onTouchStart(event); }} @touchmove=${(event: TouchEvent) => { this.onTouchMove(event); }}>
           ${this.renderHistoryBoundary()}
           ${repeat(
-            groupChatMessages(this.messages, this.messageStart),
+            this.groupedMessages(),
             (group) => group.kind === "message" ? this.messageAnchorKey(group.index) : this.groupAnchorKey(group.endIndex),
             (group) => group.kind === "message"
               ? this.renderMessage(group.message, group.index)
@@ -104,6 +116,14 @@ export class ChatView extends LitElement {
     `;
   }
 
+  private groupedMessages(): ChatGroup[] {
+    if (this.groupedMessagesInput === this.messages && this.groupedMessagesStart === this.messageStart) return this.groupedMessagesCache;
+    this.groupedMessagesInput = this.messages;
+    this.groupedMessagesStart = this.messageStart;
+    this.groupedMessagesCache = groupChatMessages(this.messages, this.messageStart);
+    return this.groupedMessagesCache;
+  }
+
   private renderActivityDock() {
     const state = this.activityState();
     if (state === undefined) return null;
@@ -277,11 +297,15 @@ export class ChatView extends LitElement {
   }
 
   private messageCopyText(message: ChatLine): string {
-    return message.parts
+    const cached = this.messageCopyTextCache.get(message);
+    if (cached !== undefined) return cached;
+    const text = message.parts
       .filter((part): part is Extract<ChatPart, { type: "text" }> => part.type === "text")
       .map((part) => part.text.trim())
-      .filter((text) => text !== "")
+      .filter((partText) => partText !== "")
       .join("\n\n");
+    this.messageCopyTextCache.set(message, text);
+    return text;
   }
 
   private async copyMessage(message: ChatLine, key: string, event: MouseEvent): Promise<void> {
@@ -304,22 +328,27 @@ export class ChatView extends LitElement {
   }
 
   private messageMetaLabel(message: ChatLine): { short: string; full: string } {
+    const cached = this.messageMetaCache.get(message);
+    if (cached !== undefined) return cached;
     const timestamp = message.meta?.timestamp;
     const model = this.modelLabel(message);
-    if (timestamp === undefined && model === undefined) return { short: "no info", full: "No Pi message metadata available" };
+    if (timestamp === undefined && model === undefined) {
+      const empty = { short: "no info", full: "No Pi message metadata available" };
+      this.messageMetaCache.set(message, empty);
+      return empty;
+    }
     const time = timestamp === undefined ? undefined : this.formatTimestamp(timestamp);
     const parts = [time?.short, model].filter((part): part is string => part !== undefined && part !== "");
     const fullParts = [time?.full, model === undefined ? undefined : `Model: ${model}`].filter((part): part is string => part !== undefined && part !== "");
-    return { short: parts.join(" · "), full: fullParts.join(" · ") };
+    const label = { short: parts.join(" · "), full: fullParts.join(" · ") };
+    this.messageMetaCache.set(message, label);
+    return label;
   }
 
   private formatTimestamp(timestamp: string): { short: string; full: string } | undefined {
     const date = new Date(timestamp);
     if (!Number.isFinite(date.getTime())) return undefined;
-    return {
-      short: new Intl.DateTimeFormat(undefined, { month: "short", day: "numeric", hour: "2-digit", minute: "2-digit" }).format(date),
-      full: new Intl.DateTimeFormat(undefined, { dateStyle: "medium", timeStyle: "medium" }).format(date),
-    };
+    return { short: shortTimestampFormatter.format(date), full: fullTimestampFormatter.format(date) };
   }
 
   private modelLabel(message: ChatLine): string | undefined {
@@ -415,7 +444,9 @@ export class ChatView extends LitElement {
   }
 
   private requestLoadMoreIfNeeded(): void {
-    requestAnimationFrame(() => {
+    if (this.loadMoreCheckFrame !== undefined) return;
+    this.loadMoreCheckFrame = requestAnimationFrame(() => {
+      this.loadMoreCheckFrame = undefined;
       if (this.suppressLoadMoreRequests) return;
       const chat = this.chat;
       if (!chat) return;
@@ -459,7 +490,9 @@ export class ChatView extends LitElement {
   }
 
   private scrollToBottom() {
-    requestAnimationFrame(() => {
+    if (this.scrollToBottomFrame !== undefined) return;
+    this.scrollToBottomFrame = requestAnimationFrame(() => {
+      this.scrollToBottomFrame = undefined;
       const chat = this.chat;
       if (!chat) return;
       this.withSuppressedScrollSave(() => {
diff --git a/src/client/src/components/PiWebApp.ts b/src/client/src/components/PiWebApp.ts
index 096c4fb..8c622c2 100644
--- a/src/client/src/components/PiWebApp.ts
+++ b/src/client/src/components/PiWebApp.ts
@@ -65,13 +65,18 @@ export class PiWebApp extends LitElement {
   private readonly keyboard = new KeyboardShortcutDispatcher();
   private readonly realtime = new RealtimeSocket();
   private readonly activeTerminalIds = new Set<string>();
+  private readonly mobileNavigationMedia = typeof window !== "undefined" && "matchMedia" in window ? window.matchMedia("(max-width: 760px)") : undefined;
   private terminalAutoStartWorkspaceId: string | undefined;
   private readonly plugins = createPluginRegistry();
+  @state() private isMobileNavigationLayout = this.mobileNavigationMedia?.matches ?? false;
   private readonly onPopState = () => void this.withChatScrollTransition(() => this.restoreRoute(false));
   private readonly onFocus = () => { void this.sessions.refreshSelectedSession(); };
   private readonly onVisibilityChange = () => {
     if (document.visibilityState === "visible") void this.sessions.refreshSelectedSession();
   };
+  private readonly onMobileNavigationMediaChange = (event: MediaQueryListEvent) => {
+    this.isMobileNavigationLayout = event.matches;
+  };
   private readonly onKeyDown = (event: KeyboardEvent) => {
     if (this.keyboard.handle(event, this.getActions())) {
       event.preventDefault();
@@ -85,6 +90,7 @@ export class PiWebApp extends LitElement {
     window.addEventListener("focus", this.onFocus);
     document.addEventListener("visibilitychange", this.onVisibilityChange);
     window.addEventListener("keydown", this.onKeyDown);
+    this.mobileNavigationMedia?.addEventListener("change", this.onMobileNavigationMediaChange);
     this.connectRealtime();
     void this.loadExternalPlugins();
     void this.loadProjectsAndRestoreRoute();
@@ -95,6 +101,7 @@ export class PiWebApp extends LitElement {
     window.removeEventListener("focus", this.onFocus);
     document.removeEventListener("visibilitychange", this.onVisibilityChange);
     window.removeEventListener("keydown", this.onKeyDown);
+    this.mobileNavigationMedia?.removeEventListener("change", this.onMobileNavigationMediaChange);
     this.keyboard.reset();
     this.sessions.dispose();
     this.realtime.close();
@@ -103,6 +110,7 @@ export class PiWebApp extends LitElement {
   }
 
   private setState(patch: Partial<AppState>) {
+    if (!patchChangesState(this.state, patch)) return;
     const previous = this.state;
     this.state = { ...this.state, ...patch };
     this.handleActivityTransition(previous, this.state);
@@ -376,7 +384,7 @@ export class PiWebApp extends LitElement {
     const state = this.state;
     return html`
       <div class=${`shell ${state.mainView === "navigation" ? "navigation-view" : state.mainView === "chat" ? "chat-view" : "workspace-view"}`}>
-        <aside>${this.renderNavigationPanel(false)}</aside>
+        <aside>${this.isMobileNavigationLayout ? null : this.renderNavigationPanel(false)}</aside>
         <main class=${state.mainView === "chat" ? "chat-view" : state.mainView === "navigation" ? "navigation-view" : "workspace-view"}>
           <div class="mobile-tabs">
             <button class=${state.mainView === "navigation" ? "mobile-navigation-tab selected" : "mobile-navigation-tab"} @click=${() => { this.selectMainView("navigation"); }}>Sessions</button>
@@ -386,7 +394,7 @@ export class PiWebApp extends LitElement {
             `)}
           </div>
           ${state.error ? html`<div class="error">${state.error}</div>` : null}
-          <div class="mobile-navigation-panel">${this.renderNavigationPanel(true)}</div>
+          <div class="mobile-navigation-panel">${this.isMobileNavigationLayout ? this.renderNavigationPanel(true) : null}</div>
           ${state.selectedSession ? html`
             <chat-view .sessionId=${state.selectedSession.id} .messages=${state.messages} .messageStart=${state.messagePageStart} .messageTotal=${state.messagePageTotal} .hasMore=${state.messagePageStart > 0} .loadingMore=${state.isLoadingEarlierMessages} .isReceivingPartialStream=${state.isReceivingPartialStream} .isCompacting=${state.status?.isCompacting === true} .pendingMessageCount=${state.status?.pendingMessageCount ?? 0} .status=${state.status} .activity=${state.activity} .onLoadMore=${() => this.withChatPrependTransition(() => this.sessions.loadEarlierMessages())}></chat-view>
             <prompt-editor .sessionId=${state.selectedSession.id} .cwd=${state.selectedWorkspace?.path} .disabled=${state.selectedSession.archived === true} .canSteer=${state.status?.isStreaming === true} .isCompacting=${state.status?.isCompacting === true} .canStop=${state.status?.isStreaming === true || state.status?.isBashRunning === true || state.status?.isCompacting === true || (state.status?.pendingMessageCount ?? 0) > 0} .status=${state.status} .onSend=${(text: string, streamingBehavior?: "steer" | "followUp") => this.sessions.send(text, streamingBehavior)} .onStop=${() => this.sessions.stopActiveWork()} .onSelectModel=${() => { void this.openModelDialog(); }} .onSelectThinking=${() => { void this.openThinkingDialog(); }}></prompt-editor>
@@ -412,6 +420,10 @@ function createPluginRegistry(): PluginRegistry {
   return registry;
 }
 
+function patchChangesState(state: AppState, patch: Partial<AppState>): boolean {
+  return Object.entries(patch).some(([key, value]) => Reflect.get(state, key) !== value);
+}
+
 function isActive(status: AppState["status"]): boolean {
   return status?.isStreaming === true || status?.isBashRunning === true || status?.isCompacting === true;
 }