Align grouped thread rails across chat and sidebar

src/renderer/components/thread/ChatPane/parts/items/ToolCallGroup.tsx

@@ -24,6 +24,7 @@ import {
   chatRowClass,
   chatRowHoverClass,
   chatRowIndicatorClass,
+  chatRowRailClass,
   chatRowShellClass,
   inlineRowTriggerClass,
   normalizeCallTitleSeparator,
@@ -147,7 +148,7 @@ export const ToolCallGroup = memo(function ToolCallGroup({
           </Disclosure.Trigger>
         </Disclosure.Heading>
         <Disclosure.Content>
-          <Disclosure.Body className="ml-3 border-l border-dashed border-[color:var(--border)] pb-0 pl-3 pt-0">
+          <Disclosure.Body className={`ml-3 ${chatRowRailClass} pb-0 pl-3 pt-0`}>
             {hasOverflowRows && !sameFileEditSummary ? (
               <div className="mb-0.5 flex justify-start">
                 <button

src/renderer/components/thread/ChatPane/parts/items/chatRow.tsx

@@ -33,6 +33,12 @@ export const chatRowHoverClass = "transition-colors hover:[--muted:var(--foregro
 // (`pt-1` dense, `pt-2.5` roomier).
 export const chatRowBodyClass = "mt-1 border-t border-[var(--hairline)] px-2";
 
+// Dashed left rail marking a group's nested children as belonging to it (the
+// chat tool-call group body, and the sidebar's worktree/thread groups). Only
+// the rail treatment lives here — callers add their own indent (`ml-*`/`pl-*`)
+// so a dense list can hug tighter than the roomier chat body.
+export const chatRowRailClass = "border-l border-dashed border-[color:var(--border)]";
+
 // Disclosure trigger for a dense inline row inside a tool-call group
 // (ToolCallInline, ReasoningInline): icon + title + trailing meta hugging
 // their content, with the shared hover treatment.

src/renderer/views/MainView/parts/Sidebar/parts/SidebarProjectThreadList.tsx

@@ -12,6 +12,7 @@ import { openNewThread, openNewThreadSideBySide } from "@/renderer/actions/threa
 import { useSidebarUiStore, useThreadListLimit } from "@/renderer/state/sidebarUiStore";
 import { useThreadLiveWorkflowStore } from "@/renderer/state/threadLiveWorkflowStore";
 import { SidebarButton } from "@/renderer/components/common/SidebarButton";
+import { chatRowRailClass } from "@/renderer/components/thread/ChatPane/parts/items/chatRow";
 import { NewThreadButton } from "./NewThreadButton";
 import { buildSidebarProjectRows, type SidebarRow } from "./sidebarProjectRows";
 import type { ThreadSortMode } from "./sortMode";
@@ -95,7 +96,7 @@ function SidebarThreadRow(props: {
   const { t } = useLingui();
 
   if (row.kind === "thread") {
-    return (
+    const item = (
       <SortableThreadItem
         thread={row.thread}
         threadIndex={row.threadIndex}
@@ -110,6 +111,14 @@ function SidebarThreadRow(props: {
         {...(row.sortDisabled !== undefined ? { sortDisabled: row.sortDisabled } : {})}
       />
     );
+    // Group children hang off the same dashed rail as the chat tool-call group
+    // (shared recipe). `ml-3.5` drops the rail down the centerline of the group
+    // header's icon; no left padding keeps the child hugging the rail so the
+    // nesting reads without a wide indent.
+    if (row.inGroup) {
+      return <div className={`ml-3.5 ${chatRowRailClass}`}>{item}</div>;
+    }
+    return item;
   }
 
   return (
@@ -129,12 +138,10 @@ function SidebarThreadRow(props: {
           editingThreadId={editingThreadId}
           setEditingThreadId={setEditingThreadId}
         />
-      ) : row.kind === "section-label" ? (
+      ) : (
         <div className="px-1.5 pb-0.5 pt-2 text-[10px] font-medium uppercase tracking-wider text-muted">
           {t(row.label)}
         </div>
-      ) : (
-        <div aria-hidden className="mx-1.5 my-1 h-px bg-[var(--hairline)]" />
       )}
     </div>
   );

src/renderer/views/MainView/parts/Sidebar/parts/SidebarThreadGroup.tsx

@@ -104,7 +104,7 @@ export function SidebarThreadGroup(props: {
           }
         }}
       >
-        <div className="group flex w-full items-center gap-1 rounded px-1.5 py-1">
+        <div className="group flex w-full items-center gap-1 rounded px-2 py-1">
           <button
             type="button"
             className="flex min-w-0 flex-1 items-center gap-1.5 text-left text-xs font-medium text-muted transition-colors hover:text-foreground"

src/renderer/views/MainView/parts/Sidebar/parts/sidebarProjectRows.ts

@@ -21,6 +21,8 @@ export type SidebarRow =
       showWorktreeBadge: boolean;
       showWorktreeFilesButton?: boolean;
       sortDisabled?: boolean;
+      /** Child of a worktree/thread group — rendered against a left rail. */
+      inGroup?: boolean;
     }
   | {
       kind: "worktree-group";
@@ -35,7 +37,6 @@ export type SidebarRow =
       key: string;
       entry: Extract<ThreadListEntry, { kind: "thread-group" }>;
     }
-  | { kind: "divider"; key: string }
   | { kind: "section-label"; key: string; label: MessageDescriptor }
   | { kind: "see-more"; key: string; hiddenCount: number };
 
@@ -139,6 +140,7 @@ function pushEntryRows(
           group: `wt:${entry.group.worktreePath}`,
           showWorktreeBadge: false,
           showWorktreeFilesButton: false,
+          inGroup: true,
         });
       });
     }
@@ -161,6 +163,7 @@ function pushEntryRows(
         group: `group:${groupKey}`,
         showWorktreeBadge: !!thread.worktreePath,
         sortDisabled: input.dndDisabled,
+        inGroup: true,
       });
     });
   }
@@ -237,13 +240,6 @@ export function buildSidebarProjectRows(input: {
         isCollapsed,
         nextUngroupedIndex,
       });
-      const isLast = i === list.length - 1;
-      if (isLast) return;
-      if (entry.kind === "worktree-group" && !isCollapsed(entry.group.worktreePath)) {
-        rows.push({ kind: "divider", key: `wt-divider:${entry.group.worktreePath}` });
-      } else if (entry.kind === "thread-group" && !isCollapsed(`group:${entry.group.groupId}`)) {
-        rows.push({ kind: "divider", key: `group-divider:${entry.group.groupId}` });
-      }
     });
   };