feat: display session ID and custom title in chat UI

src/main/services/discovery/ProjectScanner.ts

@@ -28,6 +28,7 @@ import {
 } from '@main/types';
 import {
   analyzeSessionFileMetadata,
+  extractCustomTitle,
   extractCwd,
   extractFirstUserMessagePreview,
 } from '@main/utils/jsonl';
@@ -80,6 +81,10 @@ export class ProjectScanner {
     string,
     { mtimeMs: number; size: number; preview: { text: string; timestamp: string } | null }
   >();
+  private readonly sessionCustomTitleCache = new Map<
+    string,
+    { mtimeMs: number; size: number; customTitle: string | undefined }
+  >();
 
   /** Cached project list for search — avoids re-scanning disk on every query */
   private searchProjectCache: { projects: Project[]; timestamp: number } | null = null;
@@ -767,6 +772,7 @@ export class ProjectScanner {
       todoData,
       createdAt: Math.floor(createdAt),
       firstMessage: metadata.firstUserMessage?.text,
+      customTitle: metadata.customTitle,
       messageTimestamp: metadata.firstUserMessage?.timestamp,
       hasSubagents,
       messageCount: metadata.messageCount,
@@ -819,12 +825,27 @@ export class ProjectScanner {
         ? previewTimestampMs
         : birthtimeMs;
 
+    // Fast scan for /rename custom title (only parses lines containing "custom-title")
+    const cachedCustomTitle = this.sessionCustomTitleCache.get(filePath);
+    const customTitle =
+      cachedCustomTitle?.mtimeMs === effectiveMtime && cachedCustomTitle.size === effectiveSize
+        ? cachedCustomTitle.customTitle
+        : await extractCustomTitle(filePath, this.fsProvider);
+    if (cachedCustomTitle?.mtimeMs !== effectiveMtime || cachedCustomTitle.size !== effectiveSize) {
+      this.sessionCustomTitleCache.set(filePath, {
+        mtimeMs: effectiveMtime,
+        size: effectiveSize,
+        customTitle,
+      });
+    }
+
     return {
       id: sessionId,
       projectId,
       projectPath,
       createdAt: Math.floor(createdAt),
       firstMessage: preview?.text,
+      customTitle,
       messageTimestamp: preview?.timestamp,
       hasSubagents: false,
       messageCount: 0,

src/main/types/domain.ts

@@ -91,6 +91,8 @@ export interface Session {
   createdAt: number;
   /** First user message text (for preview) */
   firstMessage?: string;
+  /** Custom title set via /rename command */
+  customTitle?: string;
   /** Timestamp of first user message (RFC3339) */
   messageTimestamp?: string;
   /** Whether this session has subagents */

src/main/utils/jsonl.ts

@@ -38,7 +38,7 @@ const logger = createLogger('Util:jsonl');
 const defaultProvider = new LocalFileSystemProvider();
 
 // Re-export for backwards compatibility
-export { extractCwd, extractFirstUserMessagePreview } from './metadataExtraction';
+export { extractCustomTitle, extractCwd, extractFirstUserMessagePreview } from './metadataExtraction';
 export { checkMessagesOngoing } from './sessionStateDetection';
 
 // =============================================================================
@@ -344,6 +344,8 @@ export interface SessionFileMetadata {
   messageCount: number;
   isOngoing: boolean;
   gitBranch: string | null;
+  /** Custom title set via /rename command */
+  customTitle?: string;
   /** Total context consumed (compaction-aware) */
   contextConsumption?: number;
   /** Number of compaction events */
@@ -381,6 +383,7 @@ export async function analyzeSessionFileMetadata(
   let firstCommandMessage: { text: string; timestamp: string } | null = null;
   let messageCount = 0;
   let hasDisplayableContent = false;
+  let customTitle: string | undefined;
   // After a UserGroup, await the first main-thread assistant message to count the AIGroup
   let awaitingAIGroup = false;
   let gitBranch: string | null = null;
@@ -412,6 +415,12 @@ export async function analyzeSessionFileMetadata(
       continue;
     }
 
+    // Detect custom-title entries (standalone, no uuid — not part of ChatHistoryEntry union)
+    const rawEntry = entry as unknown as Record<string, unknown>;
+    if (rawEntry.type === 'custom-title' && typeof rawEntry.customTitle === 'string') {
+      customTitle = rawEntry.customTitle;
+    }
+
     const parsed = parseChatHistoryEntry(entry);
     if (!parsed) {
       continue;
@@ -636,6 +645,7 @@ export async function analyzeSessionFileMetadata(
     messageCount,
     isOngoing: lastEndingIndex === -1 ? hasAnyOngoingActivity : hasActivityAfterLastEnding,
     gitBranch,
+    customTitle,
     contextConsumption,
     compactionCount: compactionPhases.length > 0 ? compactionPhases.length : undefined,
     phaseBreakdown,

src/main/utils/metadataExtraction.ts

@@ -205,3 +205,48 @@ function extractCommandName(content: string): string {
   const commandMatch = /<command-name>\/([^<]+)<\/command-name>/.exec(content);
   return commandMatch ? `/${commandMatch[1]}` : '/command';
 }
+
+/**
+ * Extract the last custom title from a session JSONL file.
+ * Scans the full file but only JSON-parses lines containing "custom-title",
+ * so the cost is minimal even for large files.
+ */
+export async function extractCustomTitle(
+  filePath: string,
+  fsProvider: FileSystemProvider = defaultProvider
+): Promise<string | undefined> {
+  if (!(await fsProvider.exists(filePath))) {
+    return undefined;
+  }
+
+  const fileStream = fsProvider.createReadStream(filePath, { encoding: 'utf8' });
+  const rl = readline.createInterface({
+    input: fileStream,
+    crlfDelay: Infinity,
+  });
+
+  let customTitle: string | undefined;
+
+  try {
+    for await (const line of rl) {
+      // Fast string check — skip JSON parse for non-matching lines
+      if (!line.includes('"custom-title"')) continue;
+
+      try {
+        const entry = JSON.parse(line) as Record<string, unknown>;
+        if (entry.type === 'custom-title' && typeof entry.customTitle === 'string') {
+          customTitle = entry.customTitle;
+        }
+      } catch {
+        // Malformed line, skip
+      }
+    }
+  } catch (error) {
+    logger.debug(`Error extracting custom title from ${filePath}:`, error);
+  } finally {
+    rl.close();
+    fileStream.destroy();
+  }
+
+  return customTitle;
+}

src/renderer/components/chat/SessionInfoBar.tsx

@@ -0,0 +1,75 @@
+import React from 'react';
+
+import { CopyButton } from '@renderer/components/common/CopyButton';
+import { useStore } from '@renderer/store';
+import { Hash, Terminal } from 'lucide-react';
+import { useShallow } from 'zustand/react/shallow';
+
+interface SessionInfoBarProps {
+  readonly tabId?: string;
+}
+
+/**
+ * Compact info strip showing the current session UUID with copy actions.
+ * Sits between SearchBar and ChatHistory in MiddlePanel so users can
+ * quickly grab the session ID or `claude --resume <id>` command.
+ */
+export const SessionInfoBar: React.FC<SessionInfoBarProps> = ({ tabId }) => {
+  const { sessionDetail } = useStore(
+    useShallow((s) => {
+      const td = tabId ? s.tabSessionData[tabId] : null;
+      return { sessionDetail: td?.sessionDetail ?? s.sessionDetail };
+    }),
+  );
+
+  if (!sessionDetail) return null;
+
+  const sessionId = sessionDetail.session.id;
+  const resumeCommand = `claude --resume ${sessionId}`;
+  const shortId = sessionId.slice(0, 8);
+
+  return (
+    <div
+      className="flex shrink-0 items-center gap-2 border-b px-3"
+      style={{
+        height: '28px',
+        borderColor: 'var(--color-border)',
+        backgroundColor: 'var(--color-surface-raised)',
+      }}
+    >
+      <Hash
+        className="size-3 shrink-0"
+        style={{ color: 'var(--color-text-muted)', opacity: 0.7 }}
+      />
+      <span
+        className="select-all font-mono"
+        title={sessionId}
+        style={{
+          fontSize: '10px',
+          color: 'var(--color-text-muted)',
+          opacity: 0.8,
+        }}
+      >
+        {shortId}
+      </span>
+      <CopyButton text={sessionId} inline />
+      <div
+        className="mx-1 h-3 border-l"
+        style={{ borderColor: 'var(--color-border)' }}
+      />
+      <button
+        onClick={() => {
+          navigator.clipboard.writeText(resumeCommand).catch(() => {
+            // Clipboard API may be unavailable in some environments
+          });
+        }}
+        className="flex items-center gap-1 rounded px-1 py-0.5 transition-colors hover:opacity-80"
+        title={resumeCommand}
+        style={{ color: 'var(--color-text-muted)' }}
+      >
+        <Terminal className="size-3" />
+        <span style={{ fontSize: '10px' }}>Resume</span>
+      </button>
+    </div>
+  );
+};

src/renderer/components/layout/MiddlePanel.tsx

@@ -1,6 +1,7 @@
 import React from 'react';
 
 import { ChatHistory } from '../chat/ChatHistory';
+import { SessionInfoBar } from '../chat/SessionInfoBar';
 import { SearchBar } from '../search/SearchBar';
 
 interface MiddlePanelProps {
@@ -12,6 +13,7 @@ export const MiddlePanel: React.FC<MiddlePanelProps> = ({ tabId }) => {
   return (
     <div className="relative flex h-full flex-col">
       <SearchBar tabId={tabId} />
+      <SessionInfoBar tabId={tabId} />
       <ChatHistory tabId={tabId} />
     </div>
   );

src/renderer/components/sidebar/SessionItem.tsx

@@ -178,7 +178,7 @@ export const SessionItem = React.memo(function SessionItem({
         type: 'session',
         sessionId: session.id,
         projectId: activeProjectId,
-        label: session.firstMessage?.slice(0, 50) ?? 'Session',
+        label: session.customTitle ?? session.firstMessage?.slice(0, 50) ?? 'Session',
       },
       forceNewTab ? { forceNewTab } : { replaceActiveTab: true }
     );
@@ -191,7 +191,7 @@ export const SessionItem = React.memo(function SessionItem({
     setContextMenu({ x: e.clientX, y: e.clientY });
   }, []);
 
-  const sessionLabel = session.firstMessage?.slice(0, 50) ?? 'Session';
+  const sessionLabel = session.customTitle ?? session.firstMessage?.slice(0, 50) ?? 'Session';
 
   const handleOpenInCurrentPane = useCallback(() => {
     if (!activeProjectId) return;
@@ -271,7 +271,7 @@ export const SessionItem = React.memo(function SessionItem({
             className="truncate text-[13px] font-medium leading-tight"
             style={{ color: isActive ? 'var(--color-text)' : 'var(--color-text-muted)' }}
           >
-            {session.firstMessage ?? 'Untitled'}
+            {session.customTitle ?? session.firstMessage ?? 'Untitled'}
           </span>
         </div>
 

src/renderer/store/slices/sessionDetailSlice.ts

@@ -398,9 +398,10 @@ export const createSessionDetailSlice: StateCreator<AppState, [], [], SessionDet
       }
       const existingTab = findTabBySession(currentState.openTabs, sessionId);
       if (existingTab && detail) {
-        const newLabel = detail.session.firstMessage
-          ? truncateLabel(detail.session.firstMessage)
-          : `Session ${sessionId.slice(0, 8)}`;
+        const newLabel = detail.session.customTitle
+          ?? (detail.session.firstMessage
+            ? truncateLabel(detail.session.firstMessage)
+            : `Session ${sessionId.slice(0, 8)}`);
         currentState.updateTabLabel(existingTab.id, newLabel);
       }