diff --git a/ui/src/ui/app-lifecycle.node.test.ts b/ui/src/ui/app-lifecycle.node.test.ts
index b15a13eb069..8a29dbcb189 100644
--- a/ui/src/ui/app-lifecycle.node.test.ts
+++ b/ui/src/ui/app-lifecycle.node.test.ts
@@ -1,45 +1,150 @@
-import { describe, expect, it, vi } from "vitest";
-import { handleDisconnected } from "./app-lifecycle.ts";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+const { scheduleChatScrollMock, scheduleLogsScrollMock, scheduleMermaidRenderMock } = vi.hoisted(
+  () => ({
+    scheduleChatScrollMock: vi.fn(),
+    scheduleLogsScrollMock: vi.fn(),
+    scheduleMermaidRenderMock: vi.fn(),
+  }),
+);
+
+vi.mock("./app-scroll.ts", () => ({
+  observeTopbar: vi.fn(),
+  scheduleChatScroll: scheduleChatScrollMock,
+  scheduleLogsScroll: scheduleLogsScrollMock,
+}));
+
+vi.mock("./mermaid.ts", () => ({
+  scheduleMermaidRender: scheduleMermaidRenderMock,
+}));
+
+import { handleDisconnected, handleUpdated } from "./app-lifecycle.ts";
+
+type TestHost = {
+  basePath: string;
+  client: { stop: () => void } | null;
+  connectGeneration: number;
+  connected: boolean;
+  tab: "chat";
+  assistantName: string;
+  assistantAvatar: null;
+  assistantAgentId: null;
+  serverVersion: null;
+  chatHasAutoScrolled: boolean;
+  chatManualRefreshInFlight: boolean;
+  chatLoading: boolean;
+  chatMessages: unknown[];
+  chatToolMessages: unknown[];
+  chatStream: string | null;
+  settings: {
+    chatShowThinking: boolean;
+    chatShowToolCalls: boolean;
+  };
+  logsAutoFollow: boolean;
+  logsAtBottom: boolean;
+  logsEntries: unknown[];
+  popStateHandler: ReturnType<typeof vi.fn>;
+  topbarObserver: ResizeObserver | null;
+};
 
 function createHost() {
-  return {
+  const host: TestHost = {
     basePath: "",
-    client: { stop: vi.fn() },
+    client: null,
     connectGeneration: 0,
-    connected: true,
+    connected: false,
     tab: "chat",
     assistantName: "OpenClaw",
     assistantAvatar: null,
     assistantAgentId: null,
+    serverVersion: null,
     chatHasAutoScrolled: false,
     chatManualRefreshInFlight: false,
     chatLoading: false,
     chatMessages: [],
     chatToolMessages: [],
     chatStream: null,
+    settings: {
+      chatShowThinking: true,
+      chatShowToolCalls: true,
+    },
     logsAutoFollow: false,
     logsAtBottom: true,
     logsEntries: [],
     popStateHandler: vi.fn(),
-    topbarObserver: { disconnect: vi.fn() } as unknown as ResizeObserver,
+    topbarObserver: null,
   };
+
+  return host;
 }
 
+describe("handleUpdated", () => {
+  beforeEach(() => {
+    scheduleChatScrollMock.mockReset();
+    scheduleLogsScrollMock.mockReset();
+    scheduleMermaidRenderMock.mockReset();
+  });
+
+  it("rerenders Mermaid blocks when chat visibility settings change", () => {
+    const host = createHost();
+    host.settings = {
+      chatShowThinking: false,
+      chatShowToolCalls: true,
+    };
+    const changed = new Map<PropertyKey, unknown>([
+      [
+        "settings",
+        {
+          chatShowThinking: true,
+          chatShowToolCalls: true,
+        },
+      ],
+    ]);
+
+    handleUpdated(host as never, changed);
+
+    expect(scheduleChatScrollMock).toHaveBeenCalledOnce();
+    expect(scheduleMermaidRenderMock).toHaveBeenCalledOnce();
+  });
+
+  it("does not rerender Mermaid blocks for unrelated settings changes", () => {
+    const host = createHost();
+    const changed = new Map<PropertyKey, unknown>([
+      [
+        "settings",
+        {
+          chatShowThinking: true,
+          chatShowToolCalls: true,
+          locale: "en",
+        },
+      ],
+    ]);
+
+    handleUpdated(host as never, changed);
+
+    expect(scheduleChatScrollMock).not.toHaveBeenCalled();
+    expect(scheduleMermaidRenderMock).not.toHaveBeenCalled();
+  });
+});
+
 describe("handleDisconnected", () => {
   it("stops and clears gateway client on teardown", () => {
     const removeSpy = vi.spyOn(window, "removeEventListener").mockImplementation(() => undefined);
     const host = createHost();
-    const disconnectSpy = (
-      host.topbarObserver as unknown as { disconnect: ReturnType<typeof vi.fn> }
-    ).disconnect;
+    const stop = vi.fn();
+    const disconnect = vi.fn();
+    host.client = { stop };
+    host.connected = true;
+    host.topbarObserver = { disconnect } as unknown as ResizeObserver;
 
-    handleDisconnected(host as unknown as Parameters<typeof handleDisconnected>[0]);
+    handleDisconnected(host as never);
 
     expect(removeSpy).toHaveBeenCalledWith("popstate", host.popStateHandler);
     expect(host.connectGeneration).toBe(1);
+    expect(stop).toHaveBeenCalledTimes(1);
     expect(host.client).toBeNull();
     expect(host.connected).toBe(false);
-    expect(disconnectSpy).toHaveBeenCalledTimes(1);
+    expect(disconnect).toHaveBeenCalledTimes(1);
     expect(host.topbarObserver).toBeNull();
     removeSpy.mockRestore();
   });
diff --git a/ui/src/ui/app-lifecycle.ts b/ui/src/ui/app-lifecycle.ts
index a986d2b6b64..9110113566f 100644
--- a/ui/src/ui/app-lifecycle.ts
+++ b/ui/src/ui/app-lifecycle.ts
@@ -36,6 +36,10 @@ type LifecycleHost = {
   chatMessages: unknown[];
   chatToolMessages: unknown[];
   chatStream: string | null;
+  settings?: {
+    chatShowThinking?: boolean;
+    chatShowToolCalls?: boolean;
+  };
   logsAutoFollow: boolean;
   logsAtBottom: boolean;
   logsEntries: unknown[];
@@ -89,13 +93,20 @@ export function handleUpdated(host: LifecycleHost, changed: Map<PropertyKey, unk
   if (host.tab === "chat" && host.chatManualRefreshInFlight) {
     return;
   }
+  const previousSettings = changed.get("settings") as LifecycleHost["settings"] | undefined;
+  const chatRenderSettingsChanged =
+    changed.has("settings") &&
+    !!previousSettings &&
+    (previousSettings.chatShowThinking !== host.settings?.chatShowThinking ||
+      previousSettings.chatShowToolCalls !== host.settings?.chatShowToolCalls);
   if (
     host.tab === "chat" &&
     (changed.has("chatMessages") ||
       changed.has("chatToolMessages") ||
       changed.has("chatStream") ||
       changed.has("chatLoading") ||
-      changed.has("tab"))
+      changed.has("tab") ||
+      chatRenderSettingsChanged)
   ) {
     const forcedByTab = changed.has("tab");
     const forcedByLoad =
diff --git a/ui/src/ui/markdown.test.ts b/ui/src/ui/markdown.test.ts
index 86ee6503717..fb848985ac5 100644
--- a/ui/src/ui/markdown.test.ts
+++ b/ui/src/ui/markdown.test.ts
@@ -42,6 +42,15 @@ describe("toSanitizedMarkdownHtml", () => {
     expect(html).toContain("Click to enlarge");
   });
 
+  it("renders Mermaid fences case-insensitively", () => {
+    const html = toSanitizedMarkdownHtml(
+      ["```Mermaid", "flowchart TD", "A --> B", "```"].join("\n"),
+    );
+
+    expect(html).toContain('class="mermaid-block"');
+    expect(html).toContain('class="language-mermaid"');
+  });
+
   it("flattens remote markdown images into alt text", () => {
     const html = toSanitizedMarkdownHtml("![Alt text](https://example.com/image.png)");
     expect(html).not.toContain("<img");
diff --git a/ui/src/ui/mermaid.ts b/ui/src/ui/mermaid.ts
index 5e2004772c4..bca7a2c7ea0 100644
--- a/ui/src/ui/mermaid.ts
+++ b/ui/src/ui/mermaid.ts
@@ -15,6 +15,15 @@ const mermaidSanitizeOptions = {
   HTML_INTEGRATION_POINTS: { foreignobject: true },
 };
 
+function setMermaidRenderError(renderTarget: HTMLElement, message: string) {
+  renderTarget.removeAttribute("role");
+  renderTarget.removeAttribute("aria-label");
+  renderTarget.removeAttribute("tabindex");
+  renderTarget.removeAttribute("title");
+  renderTarget.setAttribute("aria-live", "polite");
+  renderTarget.textContent = message;
+}
+
 async function loadMermaidApi(): Promise<MermaidApi> {
   if (!mermaidApiPromise) {
     mermaidApiPromise = import("mermaid")
@@ -152,8 +161,10 @@ async function renderMermaidBlocks(root: ParentNode): Promise<void> {
     for (const block of blocks) {
       const renderTarget = block.querySelector<HTMLElement>(".mermaid-block__render");
       if (renderTarget) {
-        renderTarget.textContent =
-          "Mermaid render failed to load. Reload the page or expand source to inspect diagram text.";
+        setMermaidRenderError(
+          renderTarget,
+          "Mermaid render failed to load. Reload the page or expand source to inspect diagram text.",
+        );
       }
       block.dataset.mermaidStatus = "error";
     }
@@ -177,7 +188,10 @@ async function renderMermaidBlocks(root: ParentNode): Promise<void> {
       block.dataset.mermaidStatus = "ready";
     } catch (err) {
       console.warn("[markdown] mermaid render failed", err);
-      renderTarget.textContent = "Mermaid render failed. Expand source to inspect diagram text.";
+      setMermaidRenderError(
+        renderTarget,
+        "Mermaid render failed. Expand source to inspect diagram text.",
+      );
       block.dataset.mermaidStatus = "error";
     }
   }