feat(ui): nest parent-child issues in inbox/mine view

Groups child issues under their parent in the inbox, matching the
nesting pattern used on the issues list page. Parent groups sort by
the most recent activity across all family members. Archived parents
don't hide their children — orphans show independently.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/lib/inbox.ts

@@ -314,6 +314,68 @@ export function getInboxWorkItems({
   });
 }
 
+/**
+ * Groups parent-child issues in a flat InboxWorkItem list.
+ *
+ * - Children whose parent is also in the list are removed from the top level
+ *   and stored in `childrenByIssueId`.
+ * - The parent's sort timestamp becomes max(parent, children) so that a group
+ *   with a recently-updated child floats to the top.
+ * - If a parent is absent (e.g. archived), children remain as independent roots.
+ */
+export function buildInboxNesting(items: InboxWorkItem[]): {
+  displayItems: InboxWorkItem[];
+  childrenByIssueId: Map<string, Issue[]>;
+} {
+  const issueItems: (InboxWorkItem & { kind: "issue" })[] = [];
+  const nonIssueItems: InboxWorkItem[] = [];
+  for (const item of items) {
+    if (item.kind === "issue") issueItems.push(item as InboxWorkItem & { kind: "issue" });
+    else nonIssueItems.push(item);
+  }
+
+  const issueIdSet = new Set(issueItems.map((i) => i.issue.id));
+  const childrenByIssueId = new Map<string, Issue[]>();
+  const childIds = new Set<string>();
+
+  for (const item of issueItems) {
+    const { issue } = item;
+    if (issue.parentId && issueIdSet.has(issue.parentId)) {
+      childIds.add(issue.id);
+      const arr = childrenByIssueId.get(issue.parentId) ?? [];
+      arr.push(issue);
+      childrenByIssueId.set(issue.parentId, arr);
+    }
+  }
+
+  // Sort each child list by most recent activity
+  for (const children of childrenByIssueId.values()) {
+    children.sort(sortIssuesByMostRecentActivity);
+  }
+
+  // Build root issue items with group-adjusted timestamps
+  const rootIssueItems: InboxWorkItem[] = issueItems
+    .filter((item) => !childIds.has(item.issue.id))
+    .map((item) => {
+      const children = childrenByIssueId.get(item.issue.id);
+      if (!children?.length) return item;
+      const maxChildTs = Math.max(...children.map(issueLastActivityTimestamp));
+      return { ...item, timestamp: Math.max(item.timestamp, maxChildTs) };
+    });
+
+  // Merge and re-sort
+  const displayItems = [...rootIssueItems, ...nonIssueItems].sort((a, b) => {
+    const diff = b.timestamp - a.timestamp;
+    if (diff !== 0) return diff;
+    if (a.kind === "issue" && b.kind === "issue") {
+      return sortIssuesByMostRecentActivity(a.issue, b.issue);
+    }
+    return 0;
+  });
+
+  return { displayItems, childrenByIssueId };
+}
+
 export function shouldShowInboxSection({
   tab,
   hasItems,

ui/src/pages/Inbox.tsx

@@ -62,6 +62,7 @@ import {
 import {
   Inbox as InboxIcon,
   AlertTriangle,
+  ChevronRight,
   XCircle,
   X,
   RotateCcw,
@@ -74,6 +75,7 @@ import type { Approval, HeartbeatRun, Issue, JoinRequest } from "@paperclipai/sh
 import {
   ACTIONABLE_APPROVAL_STATUSES,
   DEFAULT_INBOX_ISSUE_COLUMNS,
+  buildInboxNesting,
   getAvailableInboxIssueColumns,
   getApprovalsForTab,
   getInboxWorkItems,
@@ -900,6 +902,21 @@ export function Inbox() {
     projectWorkspaceById,
   ]);
 
+  // --- Parent-child nesting for inbox issues ---
+  const [collapsedInboxParents, setCollapsedInboxParents] = useState<Set<string>>(new Set());
+  const { displayItems: nestedWorkItems, childrenByIssueId } = useMemo(
+    () => buildInboxNesting(filteredWorkItems),
+    [filteredWorkItems],
+  );
+  const toggleInboxParentCollapse = useCallback((parentId: string) => {
+    setCollapsedInboxParents((prev) => {
+      const next = new Set(prev);
+      if (next.has(parentId)) next.delete(parentId);
+      else next.add(parentId);
+      return next;
+    });
+  }, []);
+
   const agentName = (id: string | null) => {
     if (!id) return null;
     return agentById.get(id) ?? null;
@@ -1169,12 +1186,12 @@ export function Inbox() {
 
   // Keep selection valid when the list shape changes, but do not auto-select on initial load.
   useEffect(() => {
-    setSelectedIndex((prev) => resolveInboxSelectionIndex(prev, filteredWorkItems.length));
-  }, [filteredWorkItems.length]);
+    setSelectedIndex((prev) => resolveInboxSelectionIndex(prev, nestedWorkItems.length));
+  }, [nestedWorkItems.length]);
 
   // Use refs for keyboard handler to avoid stale closures
   const kbStateRef = useRef({
-    workItems: filteredWorkItems,
+    workItems: nestedWorkItems,
     selectedIndex,
     canArchive: canArchiveFromTab,
     archivingIssueIds,
@@ -1183,7 +1200,7 @@ export function Inbox() {
     readItems,
   });
   kbStateRef.current = {
-    workItems: filteredWorkItems,
+    workItems: nestedWorkItems,
     selectedIndex,
     canArchive: canArchiveFromTab,
     archivingIssueIds,
@@ -1339,7 +1356,7 @@ export function Inbox() {
     dashboard.costs.monthUtilizationPercent >= 80 &&
     !dismissed.has("alert:budget");
   const hasAlerts = showAggregateAgentError || showBudgetAlert;
-  const showWorkItemsSection = filteredWorkItems.length > 0;
+  const showWorkItemsSection = nestedWorkItems.length > 0;
   const showAlertsSection = shouldShowInboxSection({
     tab,
     hasItems: hasAlerts,
@@ -1526,7 +1543,7 @@ export function Inbox() {
           {showSeparatorBefore("work_items") && <Separator />}
           <div>
             <div ref={listRef} className="overflow-hidden rounded-xl border border-border bg-card">
-              {filteredWorkItems.flatMap((item, index) => {
+              {nestedWorkItems.flatMap((item, index) => {
                 const wrapItem = (key: string, isSelected: boolean, child: ReactNode) => (
                   <div
                     key={`sel-${key}`}
@@ -1542,7 +1559,7 @@ export function Inbox() {
                   index > 0 &&
                   item.timestamp > 0 &&
                   item.timestamp < todayCutoff &&
-                  filteredWorkItems[index - 1].timestamp >= todayCutoff;
+                  nestedWorkItems[index - 1].timestamp >= todayCutoff;
                 const elements: ReactNode[] = [];
                 if (showTodayDivider) {
                   elements.push(
@@ -1666,72 +1683,135 @@ export function Inbox() {
                 }
 
                 const issue = item.issue;
-                const isUnread = issue.isUnreadForMe && !fadingOutIssues.has(issue.id);
-                const isFading = fadingOutIssues.has(issue.id);
-                const isArchiving = archivingIssueIds.has(issue.id);
-                const issueProject = issue.projectId ? projectById.get(issue.projectId) ?? null : null;
-                const row = (
-                  <IssueRow
-                    key={`issue:${issue.id}`}
-                    issue={issue}
-                    issueLinkState={issueLinkState}
-                    selected={isSelected}
-                    className={
-                      isArchiving
-                        ? "pointer-events-none -translate-x-4 scale-[0.98] opacity-0 transition-all duration-200 ease-out"
-                        : "transition-all duration-200 ease-out"
-                    }
-                    desktopMetaLeading={
-                      <InboxIssueMetaLeading
-                        issue={issue}
-                        isLive={liveIssueIds.has(issue.id)}
-                        showStatus={visibleIssueColumnSet.has("status") && availableIssueColumnSet.has("status")}
-                        showIdentifier={visibleIssueColumnSet.has("id") && availableIssueColumnSet.has("id")}
-                      />
-                    }
-                    mobileMeta={issueActivityText(issue).toLowerCase()}
-                    unreadState={
-                      isUnread ? "visible" : isFading ? "fading" : "hidden"
-                    }
-                    onMarkRead={() => markReadMutation.mutate(issue.id)}
-                    onArchive={
-                      canArchiveFromTab
-                        ? () => archiveIssueMutation.mutate(issue.id)
-                        : undefined
-                    }
-                    archiveDisabled={isArchiving || archiveIssueMutation.isPending}
-                    desktopTrailing={
-                      visibleTrailingIssueColumns.length > 0 ? (
-                        <InboxIssueTrailingColumns
-                          issue={issue}
-                          columns={visibleTrailingIssueColumns}
-                          projectName={issueProject?.name ?? null}
-                          projectColor={issueProject?.color ?? null}
-                          workspaceName={resolveIssueWorkspaceName(issue, {
-                            executionWorkspaceById,
-                            projectWorkspaceById,
-                            defaultProjectWorkspaceIdByProjectId,
-                          })}
-                          assigneeName={agentName(issue.assigneeAgentId)}
-                          currentUserId={currentUserId}
-                          parentIdentifier={issue.parentId ? (issueById.get(issue.parentId)?.identifier ?? null) : null}
-                          parentTitle={issue.parentId ? (issueById.get(issue.parentId)?.title ?? null) : null}
-                        />
-                      ) : undefined
-                    }
-                  />
-                );
+                const childIssues = childrenByIssueId.get(issue.id) ?? [];
+                const hasChildren = childIssues.length > 0;
+                const isExpanded = hasChildren && !collapsedInboxParents.has(issue.id);
 
+                const renderInboxIssue = (iss: Issue, depth: number, sel: boolean) => {
+                  const isUnread = iss.isUnreadForMe && !fadingOutIssues.has(iss.id);
+                  const isFading = fadingOutIssues.has(iss.id);
+                  const isArch = archivingIssueIds.has(iss.id);
+                  const proj = iss.projectId ? projectById.get(iss.projectId) ?? null : null;
+                  return (
+                    <IssueRow
+                      key={`issue:${iss.id}`}
+                      issue={iss}
+                      issueLinkState={issueLinkState}
+                      selected={sel}
+                      className={
+                        isArch
+                          ? "pointer-events-none -translate-x-4 scale-[0.98] opacity-0 transition-all duration-200 ease-out"
+                          : "transition-all duration-200 ease-out"
+                      }
+                      desktopMetaLeading={
+                        <>
+                          {depth === 0 && hasChildren ? (
+                            <button
+                              type="button"
+                              className="hidden shrink-0 items-center sm:inline-flex"
+                              onClick={(e) => {
+                                e.preventDefault();
+                                e.stopPropagation();
+                                toggleInboxParentCollapse(issue.id);
+                              }}
+                            >
+                              <ChevronRight className={cn("h-3.5 w-3.5 transition-transform", isExpanded && "rotate-90")} />
+                            </button>
+                          ) : depth === 0 ? null : (
+                            <span className="hidden w-3.5 shrink-0 sm:block" />
+                          )}
+                          <InboxIssueMetaLeading
+                            issue={iss}
+                            isLive={liveIssueIds.has(iss.id)}
+                            showStatus={visibleIssueColumnSet.has("status") && availableIssueColumnSet.has("status")}
+                            showIdentifier={visibleIssueColumnSet.has("id") && availableIssueColumnSet.has("id")}
+                          />
+                        </>
+                      }
+                      titleSuffix={hasChildren && !isExpanded && depth === 0 ? (
+                        <span className="ml-1.5 text-xs text-muted-foreground">
+                          ({childIssues.length} sub-task{childIssues.length !== 1 ? "s" : ""})
+                        </span>
+                      ) : undefined}
+                      mobileMeta={issueActivityText(iss).toLowerCase()}
+                      mobileLeading={
+                        depth === 0 && hasChildren ? (
+                          <button type="button" onClick={(e) => {
+                            e.preventDefault();
+                            e.stopPropagation();
+                            toggleInboxParentCollapse(issue.id);
+                          }}>
+                            <ChevronRight className={cn("h-3.5 w-3.5 transition-transform", isExpanded && "rotate-90")} />
+                          </button>
+                        ) : undefined
+                      }
+                      unreadState={
+                        isUnread ? "visible" : isFading ? "fading" : "hidden"
+                      }
+                      onMarkRead={() => markReadMutation.mutate(iss.id)}
+                      onArchive={
+                        canArchiveFromTab
+                          ? () => archiveIssueMutation.mutate(iss.id)
+                          : undefined
+                      }
+                      archiveDisabled={isArch || archiveIssueMutation.isPending}
+                      desktopTrailing={
+                        visibleTrailingIssueColumns.length > 0 ? (
+                          <InboxIssueTrailingColumns
+                            issue={iss}
+                            columns={visibleTrailingIssueColumns}
+                            projectName={proj?.name ?? null}
+                            projectColor={proj?.color ?? null}
+                            workspaceName={resolveIssueWorkspaceName(iss, {
+                              executionWorkspaceById,
+                              projectWorkspaceById,
+                              defaultProjectWorkspaceIdByProjectId,
+                            })}
+                            assigneeName={agentName(iss.assigneeAgentId)}
+                            currentUserId={currentUserId}
+                            parentIdentifier={iss.parentId ? (issueById.get(iss.parentId)?.identifier ?? null) : null}
+                            parentTitle={iss.parentId ? (issueById.get(iss.parentId)?.title ?? null) : null}
+                          />
+                        ) : undefined
+                      }
+                    />
+                  );
+                };
+
+                // Render parent issue
+                const parentRow = renderInboxIssue(issue, 0, isSelected);
                 elements.push(wrapItem(`issue:${issue.id}`, isSelected, canArchiveFromTab ? (
                   <SwipeToArchive
                     key={`issue:${issue.id}`}
                     selected={isSelected}
-                    disabled={isArchiving || archiveIssueMutation.isPending}
+                    disabled={archivingIssueIds.has(issue.id) || archiveIssueMutation.isPending}
                     onArchive={() => archiveIssueMutation.mutate(issue.id)}
                   >
-                    {row}
+                    {parentRow}
                   </SwipeToArchive>
-                ) : row));
+                ) : parentRow));
+
+                // Render children if expanded
+                if (isExpanded) {
+                  for (const child of childIssues) {
+                    const childRow = renderInboxIssue(child, 1, false);
+                    const isChildArchiving = archivingIssueIds.has(child.id);
+                    elements.push(
+                      <div key={`sel-issue:${child.id}`} data-inbox-item className="relative" style={{ paddingLeft: 16 }}>
+                        {canArchiveFromTab ? (
+                          <SwipeToArchive
+                            key={`issue:${child.id}`}
+                            selected={false}
+                            disabled={isChildArchiving || archiveIssueMutation.isPending}
+                            onArchive={() => archiveIssueMutation.mutate(child.id)}
+                          >
+                            {childRow}
+                          </SwipeToArchive>
+                        ) : childRow}
+                      </div>,
+                    );
+                  }
+                }
                 return elements;
               })}
             </div>