feat(desktop): agent activity focus view

AGENTS.md

@@ -258,6 +258,24 @@ scripts build the required E2E bridge before running Playwright.
 
 See [TESTING.md](TESTING.md) for the full multi-agent E2E guide.
 
+### Never assert a DOM element against `null` with `assert.equal`
+
+In the desktop jsdom tests (`desktop/src/**/*.test.mjs`), write
+
+```js
+assert.ok(container.querySelector(sel) === null, "no header row");
+```
+
+**not** `assert.equal(container.querySelector(sel), null, ...)`. Both pass
+identically, but when the `assert.equal` form *fails*, node serializes the
+matched element and its entire subtree to build a diff. On a real transcript
+that exhausts memory and the runner dies with SIGKILL after ~100s instead of
+printing the assertion message — so a genuine regression is unreadable and
+looks like a hang or an OOM in unrelated code. The `assert.ok(x === null)` form
+fails in milliseconds with the message you wrote.
+
+Comparing `getAttribute(...)` to `null` is fine — attributes are strings.
+
 ### PR Screenshots
 
 > **Do NOT use `buzz upload`, the relay media endpoint, or any third-party

desktop/playwright.config.ts

@@ -97,6 +97,8 @@ export default defineConfig({
         "**/thread-reply-anchor-roleplay.spec.ts",
         "**/threadpane-ultrawide.spec.ts",
         "**/thread-focus-mode.spec.ts",
+        "**/agent-activity-cover.spec.ts",
+        "**/agent-activity-cover-screenshots.spec.ts",
         "**/animated-avatar.spec.ts",
         "**/reminders.spec.ts",
         "**/reminder-click-repro.spec.ts",

desktop/src/app/AppShell.tsx

@@ -75,7 +75,7 @@ import {
 import { useDueReminderBadgeCount } from "@/features/reminders/hooks";
 import { useReminderNotifications } from "@/features/reminders/useReminderNotifications";
 import { AppSidebar } from "@/features/sidebar/ui/AppSidebar";
-import { requestFocusedThreadClose } from "@/features/channels/focusedThreadCloseRequest";
+import { requestCoverDrawerClose } from "@/features/channels/coverDrawerCloseRequest";
 import { CommunityRail } from "@/features/sidebar/ui/CommunityRail";
 import { useChannelMutes } from "@/features/sidebar/lib/useChannelMutes";
 import { useChannelStars } from "@/features/sidebar/lib/useChannelStars";
@@ -846,7 +846,7 @@ export function AppShell() {
                             addCommunityDialog.onOpenChange
                           }
                           onNewMessage={goNewMessage}
-                          onBackgroundClick={requestFocusedThreadClose}
+                          onBackgroundClick={requestCoverDrawerClose}
                           onCreateChannelOpenChange={setIsCreateChannelOpen}
                           onOpenAddCommunity={addCommunityDialog.openDialog}
                           onSendFeedback={() => setIsSendFeedbackOpen(true)}

desktop/src/features/agents/ui/AgentSessionToolItem/CompactMessageSummary.tsx

@@ -52,10 +52,13 @@ export function CompactMessageSummary({
   const { goChannel } = useAppNavigation();
   const { openProfilePanel } = useProfilePanel();
   const isCompactPreview = variant === "compactPreview";
-  const shouldClampBubble = !isCompactPreview;
+  const isConversation = variant === "conversation";
+  // Focus mode is a reading view, so sent messages remain fully visible there.
+  // The default activity surface keeps the compact clamp.
+  const shouldClampBubble = !isCompactPreview && !isConversation;
   const [bubbleRef, hasBubbleOverflow] =
     useTranscriptBubbleOverflow(shouldClampBubble);
-  const canOpenMessage = shouldClampBubble && messageLink !== null;
+  const canOpenMessage = !isCompactPreview && messageLink !== null;
   const mutedTone = compactSummaryTone();
   const avatarClassName = cn(
     "mr-2 mt-1 shrink-0",
@@ -135,14 +138,20 @@ export function CompactMessageSummary({
             testId="transcript-agent-sent-avatar"
           />
         )}
-        <div className="flex min-w-0 flex-1 flex-col items-start gap-1">
+        <div
+          className={cn(
+            "flex min-w-0 flex-1 flex-col items-start gap-1",
+            isConversation && "pr-9",
+          )}
+        >
           <div
             className={cn(
-              "w-full min-w-0 rounded-2xl border px-3 py-2 shadow-sm",
+              "w-full min-w-0 rounded-2xl border px-3 py-2",
               isCompactPreview
                 ? "text-xs leading-4"
                 : "text-sm leading-relaxed",
               shouldClampBubble && "relative max-h-36 overflow-hidden",
+              isConversation && "relative pr-4",
               canOpenMessage &&
                 "group/bubble cursor-pointer transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring",
               isCompactPreview

desktop/src/features/agents/ui/AgentSessionToolItem/ToolItem.tsx

@@ -10,6 +10,7 @@ import type { TranscriptItem } from "../agentSessionTypes";
 import { getBuzzToolInfo } from "../agentSessionToolCatalog";
 import { buildCompactToolSummary } from "../agentSessionToolSummary";
 import type { AgentTranscriptIdentityProps } from "../activityRenderClasses/types";
+import { useIsInsideWorkBlockRail } from "../agentSessionTranscriptContext";
 import {
   formatTranscriptTimestampTitle,
   getToolDurationDisplay,
@@ -34,6 +35,7 @@ export function ToolItem({
   profiles?: UserProfileLookup;
 }) {
   const [isExpanded, setIsExpanded] = React.useState(false);
+  const insideWorkBlockRail = useIsInsideWorkBlockRail();
   const hasArgs = Object.keys(item.args).length > 0;
   const hasResult = item.result.trim().length > 0;
   const canonicalToolName = item.buzzToolName ?? item.toolName;
@@ -57,7 +59,11 @@ export function ToolItem({
     [],
   );
 
-  if (compactSummary.presentation === "message") {
+  // Message presentations keep their readable bubble whenever they are standalone.
+  // The conversation grouping keeps message sends standalone rather than placing
+  // them on a work block rail; this guard preserves the muted row if another
+  // transcript composition explicitly embeds one in a rail.
+  if (compactSummary.presentation === "message" && !insideWorkBlockRail) {
     return (
       <div
         className="not-prose w-full"