Align thread summary rows

desktop/src/features/messages/lib/threadTreeLayout.ts

@@ -1,7 +1,7 @@
 const THREAD_REPLY_MAX_VISIBLE_DEPTH = 6;
 
 const THREAD_REPLY_AVATAR_SIZE_REM = 2.25; // Tailwind size-9
-const THREAD_REPLY_ROW_MARGIN_INLINE_REM = 0.25; // Tailwind mx-1
+export const THREAD_REPLY_ROW_MARGIN_INLINE_REM = 0.25; // Tailwind mx-1
 const THREAD_REPLY_ROW_CONTENT_INSET_REM = 0.5; // Tailwind px-2
 const THREAD_REPLY_ROW_CONTENT_GAP_REM = 0.625; // Tailwind gap-2.5
 const THREAD_REPLY_ROW_PADDING_TOP_REM = 0.375; // Tailwind py-1.5

desktop/src/features/messages/ui/MessageHeader.tsx

@@ -43,6 +43,7 @@ export function MessageAuthorText({
         hoverUnderline && "hover:underline",
         className,
       )}
+      data-testid="message-author"
     >
       {children}
     </Component>

desktop/src/features/messages/ui/MessageThreadPanel.tsx

@@ -95,7 +95,7 @@ type MessageThreadPanelProps = {
 const EMPTY_THREAD_REPLIES: MainTimelineEntry[] = [];
 const THREAD_PANEL_MESSAGE_GUTTER_CLASS = "px-2";
 const THREAD_PANEL_COMPOSER_GUTTER_CLASS = "px-5";
-const THREAD_PANEL_SUMMARY_INDENT_OFFSET_REM = -0.125;
+const THREAD_PANEL_SUMMARY_INDENT_OFFSET_REM = 0;
 type MessageThreadPanelSkeletonProps = {
   isSinglePanelView?: boolean;
   layout?: "standalone" | "split";

desktop/src/features/messages/ui/MessageThreadSummaryRow.tsx

@@ -13,10 +13,15 @@ import {
   threadReplyLength,
   THREAD_REPLY_BODY_OFFSET_REM,
   THREAD_REPLY_LINE_WIDTH_REM,
+  THREAD_REPLY_ROW_MARGIN_INLINE_REM,
 } from "@/features/messages/lib/threadTreeLayout";
 import { cn } from "@/shared/lib/cn";
 import { UserAvatar } from "@/shared/ui/UserAvatar";
 
+const THREAD_SUMMARY_CONTENT_OFFSET_REM =
+  THREAD_REPLY_BODY_OFFSET_REM - THREAD_REPLY_ROW_MARGIN_INLINE_REM;
+const THREAD_SUMMARY_SURFACE_AVATAR_INSET_REM = 0.25;
+
 function ParticipantAvatar({
   participant,
   index,
@@ -80,8 +85,15 @@ export function MessageThreadSummaryRow({
   unreadCount?: number;
 }) {
   const indentRem = getThreadReplyIndentRem(depth);
-  const marginLeftRem =
-    indentRem + THREAD_REPLY_BODY_OFFSET_REM + summaryIndentOffsetRem;
+  const hoverLeftRem =
+    indentRem + THREAD_REPLY_ROW_MARGIN_INLINE_REM + summaryIndentOffsetRem;
+  const hoverLeft = threadReplyLength(hoverLeftRem);
+  const contentPaddingStart = threadReplyLength(
+    THREAD_SUMMARY_CONTENT_OFFSET_REM,
+  );
+  const surfaceInsetStart = `calc(${contentPaddingStart} - ${threadReplyLength(
+    THREAD_SUMMARY_SURFACE_AVATAR_INSET_REM,
+  )})`;
   const replyLabel = summary.replyCount === 1 ? "reply" : "replies";
   const summaryAriaLabel = summary.lastReplyAt
     ? `View thread with ${summary.replyCount} ${replyLabel}, last reply ${formatThreadSummaryLastReplyTime(summary.lastReplyAt)}`
@@ -198,14 +210,27 @@ export function MessageThreadSummaryRow({
 
       <button
         aria-label={summaryAriaLabel}
-        className="group relative isolate inline-flex h-8 w-fit max-w-full cursor-pointer items-center gap-1.5 rounded-full text-left text-xs font-medium text-muted-foreground transition-[color,opacity] before:pointer-events-none before:absolute before:-bottom-0.5 before:-left-0.5 before:-right-2 before:-top-0.5 before:-z-10 before:rounded-full before:content-[''] before:transition-[background-color,box-shadow] hover:text-foreground hover:opacity-90 hover:before:bg-background/95 hover:before:ring-1 hover:before:ring-border/70 focus-visible:outline-hidden focus-visible:before:bg-background/95 focus-visible:before:ring-1 focus-visible:before:ring-ring"
+        className="group relative isolate inline-flex h-8 w-fit max-w-full cursor-pointer items-center gap-1.5 rounded-full py-0 pr-3 text-left text-xs font-medium text-muted-foreground transition-[color,opacity] hover:text-foreground hover:opacity-90 focus-visible:outline-hidden"
         data-thread-head-id={message.id}
         data-testid="message-thread-summary"
         onClick={() => onOpenThread(message)}
-        style={{ marginLeft: threadReplyLength(marginLeftRem) }}
+        style={{
+          marginLeft: hoverLeft,
+          maxWidth: `calc(100% - ${hoverLeft})`,
+          paddingLeft: contentPaddingStart,
+        }}
         type="button"
       >
-        <div className="ml-0.5 flex shrink-0 items-center">
+        <span
+          aria-hidden="true"
+          className="pointer-events-none absolute bottom-[-0.125rem] top-[-0.125rem] rounded-full opacity-0 ring-border/70 transition-[background-color,box-shadow,opacity] group-hover:bg-background/95 group-hover:opacity-100 group-hover:ring-1 group-focus-visible:bg-background/95 group-focus-visible:opacity-100 group-focus-visible:ring-1 group-focus-visible:ring-ring"
+          data-testid="message-thread-summary-surface"
+          style={{
+            left: surfaceInsetStart,
+            right: 0,
+          }}
+        />
+        <div className="relative z-10 flex shrink-0 items-center">
           {summary.participants.map((participant, index) => (
             <ParticipantAvatar
               index={index}
@@ -215,7 +240,7 @@ export function MessageThreadSummaryRow({
             />
           ))}
         </div>
-        <div className="min-w-0">
+        <div className="relative z-10 min-w-0">
           <div>
             <span className="font-medium transition-colors group-hover:text-foreground">
               {summary.replyCount} {replyLabel}

desktop/src/features/messages/ui/TimelineMessageList.tsx

@@ -7,6 +7,7 @@ import {
   getTimelineItemKey,
   type TimelineItem,
 } from "@/features/messages/lib/timelineItems";
+import { THREAD_REPLY_ROW_MARGIN_INLINE_REM } from "@/features/messages/lib/threadTreeLayout";
 import { buildMainTimelineEntries } from "@/features/messages/lib/threadPanel";
 import type { MainTimelineEntry } from "@/features/messages/lib/threadPanel";
 import {
@@ -353,7 +354,7 @@ function MessageRowItem({
     return (
       <div
         className={cn(
-          "group/message relative mx-1 flex flex-col gap-0 rounded-2xl px-0 py-1 pb-2.5 transition-colors hover:bg-muted/50 focus-within:bg-muted/50",
+          "group/message relative mx-1 mb-1.5 flex flex-col gap-0 rounded-2xl px-0 py-1 transition-colors hover:bg-muted/50 focus-within:bg-muted/50",
           isHighlighted &&
             "-mx-4 px-4 before:absolute before:-inset-y-1.5 before:inset-x-0 before:animate-[route-target-highlight-fade_2s_ease-out_forwards] before:bg-primary/10 before:content-[''] motion-reduce:before:animate-none sm:-mx-6 sm:px-6",
         )}
@@ -396,6 +397,7 @@ function MessageRowItem({
           onOpenThread={onReply}
           showDepthGuides={false}
           summary={summary}
+          summaryIndentOffsetRem={-THREAD_REPLY_ROW_MARGIN_INLINE_REM}
           unreadCount={threadUnreadCounts?.get(message.id)}
         />
         {footer}

desktop/tests/e2e/messaging.spec.ts

@@ -30,6 +30,67 @@ async function expectThreadReplyUnobscured(row: Locator) {
     .toBe(true);
 }
 
+async function measureThreadSummaryGeometry(summaryRow: Locator) {
+  return summaryRow.evaluate((summaryButton) => {
+    const summaryWrapper = summaryButton.parentElement;
+    const container = summaryWrapper?.parentElement;
+    const messageRow = container?.querySelector<HTMLElement>(
+      '[data-testid="message-row"]',
+    );
+    const messageMarkdown =
+      messageRow?.querySelector<HTMLElement>(".message-markdown");
+    const messageAuthor = messageRow?.querySelector<HTMLElement>(
+      '[data-testid="message-author"]',
+    );
+    const firstParticipant = summaryButton.querySelector<HTMLElement>(
+      '[data-testid="message-thread-summary-participant"]',
+    );
+    const summarySurface = summaryButton.querySelector<HTMLElement>(
+      '[data-testid="message-thread-summary-surface"]',
+    );
+    const firstAvatar = firstParticipant?.firstElementChild;
+
+    if (
+      !summaryWrapper ||
+      !container ||
+      !messageRow ||
+      !messageAuthor ||
+      !messageMarkdown ||
+      !summarySurface ||
+      !(firstAvatar instanceof HTMLElement)
+    ) {
+      throw new Error("Expected measurable thread summary geometry.");
+    }
+
+    const containerRect = container.getBoundingClientRect();
+    const messageRowRect = messageRow.getBoundingClientRect();
+    const messageAuthorRect = messageAuthor.getBoundingClientRect();
+    const messageMarkdownRect = messageMarkdown.getBoundingClientRect();
+    const summaryButtonRect = summaryButton.getBoundingClientRect();
+    const summaryButtonStyle = getComputedStyle(summaryButton);
+    const summaryButtonPaddingLeft = Number.parseFloat(
+      summaryButtonStyle.paddingLeft,
+    );
+    const summaryWrapperRect = summaryWrapper.getBoundingClientRect();
+    const firstAvatarRect = firstAvatar.getBoundingClientRect();
+    const summarySurfaceRect = summarySurface.getBoundingClientRect();
+
+    return {
+      authorLeft: messageAuthorRect.left,
+      avatarLeft: firstAvatarRect.left,
+      bodyLeft: messageMarkdownRect.left,
+      bottomPadding: containerRect.bottom - summaryWrapperRect.bottom,
+      messageRowLeft: messageRowRect.left,
+      summaryButtonContentLeft:
+        summaryButtonRect.left + summaryButtonPaddingLeft,
+      summaryButtonLeft: summaryButtonRect.left,
+      summaryButtonPaddingLeft,
+      summarySurfaceLeft: summarySurfaceRect.left,
+      topPadding: messageRowRect.top - containerRect.top,
+    };
+  });
+}
+
 test.beforeEach(async ({ page }) => {
   await installMockBridge(page);
 });
@@ -583,6 +644,44 @@ test("opens a single-level thread panel with inline expansion", async ({
         }),
     )
     .toBe("28x28");
+  const summaryGeometry = await measureThreadSummaryGeometry(rootSummaryRow);
+  expect(
+    Math.abs(summaryGeometry.authorLeft - summaryGeometry.bodyLeft),
+  ).toBeLessThanOrEqual(1);
+  expect(
+    Math.abs(summaryGeometry.avatarLeft - summaryGeometry.bodyLeft),
+  ).toBeLessThanOrEqual(1);
+  expect(
+    Math.abs(
+      summaryGeometry.summaryButtonContentLeft - summaryGeometry.bodyLeft,
+    ),
+  ).toBeLessThanOrEqual(1);
+  expect(
+    Math.abs(
+      summaryGeometry.summaryButtonLeft - summaryGeometry.messageRowLeft,
+    ),
+  ).toBeLessThanOrEqual(1);
+  expect(summaryGeometry.summaryButtonLeft).toBeLessThan(
+    summaryGeometry.bodyLeft,
+  );
+  expect(
+    Math.abs(
+      summaryGeometry.bodyLeft -
+        summaryGeometry.summaryButtonLeft -
+        summaryGeometry.summaryButtonPaddingLeft,
+    ),
+  ).toBeLessThanOrEqual(1);
+  expect(summaryGeometry.summarySurfaceLeft).toBeLessThan(
+    summaryGeometry.avatarLeft,
+  );
+  expect(
+    Math.abs(
+      summaryGeometry.avatarLeft - summaryGeometry.summarySurfaceLeft - 4,
+    ),
+  ).toBeLessThanOrEqual(1);
+  expect(
+    Math.abs(summaryGeometry.topPadding - summaryGeometry.bottomPadding),
+  ).toBeLessThanOrEqual(1);
 
   await page.mouse.move(0, 0);
   const rootSummaryWidthBeforeHover = await rootSummaryRow.evaluate((row) =>