fix: prevent renderer memory leak from unbounded expansion state

- Clear expansion Maps/Sets (aiGroupExpansionLevels, expandedStepIds,
  expandedDisplayItemIds, expandedAIGroupIds) when switching sessions
  to prevent unbounded growth over long uptime
- Add periodic pruning for sessionRefreshGeneration and
  projectRefreshGeneration Maps
- Add SubagentDisplayMeta type to Process for memory-efficient subagent
  rendering without holding full transcripts
- Add subagentMessageCacheSlice (Zustand) with single-flight Promise
  dedup and LRU eviction for on-demand subagent message loading
- Refactor SubagentItem to read displayMeta for collapsed headers and
  lazy-load message bodies only when expanded via useSubagentMessages
- Update AIChatGroup and modelExtractor to prefer displayMeta over
  iterating raw messages

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: psypeal

src/main/types/chunks.ts

@@ -12,14 +12,58 @@
  * - Constants
  */
 
-import { type Session, type SessionMetrics } from './domain';
+import {
+  type PhaseTokenBreakdown,
+  type Session,
+  type SessionMetrics,
+  type TokenUsage,
+} from './domain';
 import { type ToolUseResultData } from './jsonl';
 import { type ParsedMessage, type ToolCall, type ToolResult } from './messages';
 
 // =============================================================================
 // Process Types (Subagent Execution)
 // =============================================================================
 
+/**
+ * Pre-computed display data for a subagent.
+ *
+ * Extracted in main process during parsing so the renderer can render the
+ * collapsed SubagentItem header without holding the full transcript. Keeps
+ * `Process.messages` empty in the worker output path, reducing per-cached-
+ * SessionDetail memory by ~MB→KB per subagent.
+ *
+ * Full message bodies are loaded lazily via the get-subagent-messages IPC
+ * when the user expands a subagent or a highlighted-error needs the trace.
+ */
+export interface SubagentDisplayMeta {
+  /** Number of assistant messages containing at least one tool_use block. */
+  toolCount: number;
+  /** Model name from the first assistant message that has one (excluding `<synthetic>`). */
+  modelName: string | null;
+  /** Usage block from the LAST assistant message that has one. */
+  lastUsage: TokenUsage | null;
+  /** Count of assistant messages that have a usage block (used for "N turns"). */
+  turnCount: number;
+  /**
+   * True when this is a team member whose only assistant action is a
+   * SendMessage(shutdown_response). Used to render the slim shutdown row.
+   */
+  isShutdownOnly: boolean;
+  /** Multi-phase context breakdown when subagent has compaction events. */
+  phaseBreakdown?: {
+    phases: PhaseTokenBreakdown[];
+    totalConsumption: number;
+    compactionCount: number;
+  };
+  /**
+   * Every tool_use id and tool_result tool_use_id seen in this subagent's
+   * messages. Used by AIChatGroup.containsToolUseId and SubagentItem's
+   * highlighted-error check without iterating messages.
+   */
+  toolUseIds: string[];
+}
+
 /**
  * Resolved subagent information.
  */
@@ -28,7 +72,14 @@ export interface Process {
   id: string;
   /** Path to the subagent JSONL file */
   filePath: string;
-  /** Parsed messages from the subagent session */
+  /**
+   * Parsed messages from the subagent session.
+   *
+   * In the worker output path this is intentionally empty; the renderer
+   * loads bodies on demand via get-subagent-messages. Direct callers of
+   * SubagentResolver (drill-down via SubagentDetailBuilder) still get the
+   * full array.
+   */
   messages: ParsedMessage[];
   /** When the subagent started */
   startTime: Date;
@@ -38,6 +89,12 @@ export interface Process {
   durationMs: number;
   /** Aggregated metrics for the subagent */
   metrics: SessionMetrics;
+  /**
+   * Pre-computed display data for inline rendering without loading messages.
+   * Optional for backwards compat with code paths that don't compute it,
+   * but the worker output and SubagentResolver always populate it.
+   */
+  displayMeta?: SubagentDisplayMeta;
   /** Task description from parent Task call */
   description?: string;
   /** Subagent type from Task call (e.g., "Explore", "Plan") */
@@ -401,6 +458,8 @@ export interface SessionDetail {
   processes: Process[];
   /** Aggregated metrics for the entire session */
   metrics: SessionMetrics;
+  /** Timestamp (ms) when Rust native pipeline was used, or false if JS fallback */
+  _nativePipeline?: number | false;
 }
 
 /**
@@ -444,6 +503,7 @@ export interface FileChangeEvent {
   projectId?: string;
   sessionId?: string;
   isSubagent: boolean;
+  fileSize?: number;
 }
 
 // =============================================================================

src/preload/constants/ipcChannels.ts

@@ -187,3 +187,10 @@ export const FIND_SESSION_BY_ID = 'find-session-by-id';
 
 /** Find sessions whose IDs contain a given hex fragment */
 export const FIND_SESSIONS_BY_PARTIAL_ID = 'find-sessions-by-partial-id';
+
+// =============================================================================
+// Subagent API Channels
+// =============================================================================
+
+/** Lazy-load a single subagent's parsed messages (renderer expansion path) */
+export const SUBAGENT_GET_MESSAGES = 'subagent:get-messages';

src/preload/index.ts

@@ -22,6 +22,7 @@ import {
   SSH_SAVE_LAST_CONNECTION,
   SSH_STATUS,
   SSH_TEST,
+  SUBAGENT_GET_MESSAGES,
   UPDATER_CHECK,
   UPDATER_DOWNLOAD,
   UPDATER_INSTALL,
@@ -96,6 +97,7 @@ interface IpcFileChangePayload {
   projectId?: string;
   sessionId?: string;
   isSubagent: boolean;
+  fileSize?: number;
 }
 
 /**
@@ -152,11 +154,12 @@ const electronAPI: ElectronAPI = {
     ipcRenderer.invoke('get-waterfall-data', projectId, sessionId),
   getSubagentDetail: (projectId: string, sessionId: string, subagentId: string) =>
     ipcRenderer.invoke('get-subagent-detail', projectId, sessionId, subagentId),
+  getSubagentMessages: (projectId: string, sessionId: string, subagentId: string) =>
+    ipcRenderer.invoke(SUBAGENT_GET_MESSAGES, projectId, sessionId, subagentId),
   getSessionGroups: (projectId: string, sessionId: string) =>
     ipcRenderer.invoke('get-session-groups', projectId, sessionId),
   getSessionsByIds: (projectId: string, sessionIds: string[], options?: SessionsByIdsOptions) =>
     ipcRenderer.invoke('get-sessions-by-ids', projectId, sessionIds, options),
-
   // Repository grouping (worktree support)
   getRepositoryGroups: () => ipcRenderer.invoke('get-repository-groups'),
   getWorktreeSessions: (worktreeId: string) =>

src/renderer/api/httpClient.ts

@@ -23,6 +23,7 @@ import type {
   NotificationsAPI,
   NotificationTrigger,
   PaginatedSessionsResult,
+  ParsedMessage,
   Project,
   RepositoryGroup,
   SearchSessionsResult,
@@ -255,6 +256,15 @@ export class HttpAPIClient implements ElectronAPI {
       `/api/projects/${encodeURIComponent(projectId)}/sessions/${encodeURIComponent(sessionId)}/subagents/${encodeURIComponent(subagentId)}`
     );
 
+  getSubagentMessages = (
+    projectId: string,
+    sessionId: string,
+    subagentId: string
+  ): Promise<ParsedMessage[]> =>
+    this.get<ParsedMessage[]>(
+      `/api/projects/${encodeURIComponent(projectId)}/sessions/${encodeURIComponent(sessionId)}/subagents/${encodeURIComponent(subagentId)}/messages`
+    );
+
   getSessionGroups = (projectId: string, sessionId: string): Promise<ConversationGroup[]> =>
     this.get<ConversationGroup[]>(
       `/api/projects/${encodeURIComponent(projectId)}/sessions/${encodeURIComponent(sessionId)}/groups`

src/renderer/components/chat/AIChatGroup.tsx

@@ -4,7 +4,6 @@ import { COLOR_TEXT_MUTED, COLOR_TEXT_SECONDARY } from '@renderer/constants/cssV
 import { useTabUI } from '@renderer/hooks/useTabUI';
 import { useStore } from '@renderer/store';
 import { enhanceAIGroup, type PrecedingSlashInfo } from '@renderer/utils/aiGroupEnhancer';
-import { extractSlashInfo, isCommandContent } from '@shared/utils/contentSanitizer';
 import { getModelColorClass } from '@shared/utils/modelParser';
 import { estimateTokens } from '@shared/utils/tokenFormatting';
 import { format } from 'date-fns';
@@ -22,39 +21,11 @@ import type {
   AIGroup,
   AIGroupDisplayItem,
   EnhancedAIGroup,
-  UserGroup,
 } from '@renderer/types/groups';
 import type { TriggerColor } from '@shared/constants/triggerColors';
 
-/**
- * Extract slash info from a UserGroup's message content.
- * Returns PrecedingSlashInfo if the user message was a slash invocation,
- * null otherwise.
- */
-function extractPrecedingSlashInfo(
-  userGroup: UserGroup | undefined
-): PrecedingSlashInfo | undefined {
-  if (!userGroup) return undefined;
-
-  const msg = userGroup.message;
-  const content = msg.content;
-
-  // Check if this is a slash message (has <command-name> tags)
-  if (typeof content === 'string' && isCommandContent(content)) {
-    const slashInfo = extractSlashInfo(content);
-    if (slashInfo) {
-      return {
-        name: slashInfo.name,
-        message: slashInfo.message,
-        args: slashInfo.args,
-        commandMessageUuid: msg.uuid,
-        timestamp: new Date(msg.timestamp),
-      };
-    }
-  }
-
-  return undefined;
-}
+// extractPrecedingSlashInfo moved to ChatHistory — pre-computed as a map to
+// avoid O(n) scan per visible group per refresh cycle.
 
 /**
  * Format duration in milliseconds to human-readable string.
@@ -85,24 +56,31 @@ interface AIChatGroupProps {
   highlightColor?: TriggerColor;
   /** Register ref for individual tool items (for precise scroll targeting) */
   registerToolRef?: (toolId: string, el: HTMLElement | null) => void;
+  /** Pre-computed slash info from the preceding user message (avoids O(n) scan per group). */
+  precedingSlash?: PrecedingSlashInfo;
 }
 
 /**
  * Checks if a tool ID exists within the display items (including nested subagents).
+ *
+ * For subagents we read the precomputed `displayMeta.toolUseIds` slot rather
+ * than iterating `subagent.messages`, since the worker output strips the
+ * messages array. Falls back to message iteration only if displayMeta is
+ * absent (legacy/uncached path).
  */
 function containsToolUseId(items: AIGroupDisplayItem[], toolUseId: string): boolean {
   for (const item of items) {
     if (item.type === 'tool' && item.tool.id === toolUseId) {
       return true;
     }
-    // Check nested subagent messages for the tool ID
-    if (item.type === 'subagent' && item.subagent.messages) {
-      for (const msg of item.subagent.messages) {
-        if (msg.toolCalls?.some((tc) => tc.id === toolUseId)) {
-          return true;
-        }
-        if (msg.toolResults?.some((tr) => tr.toolUseId === toolUseId)) {
-          return true;
+    if (item.type === 'subagent') {
+      const ids = item.subagent.displayMeta?.toolUseIds;
+      if (ids?.includes(toolUseId)) return true;
+      // Legacy fallback for code paths that haven't populated displayMeta.
+      if (!ids && item.subagent.messages) {
+        for (const msg of item.subagent.messages) {
+          if (msg.toolCalls?.some((tc) => tc.id === toolUseId)) return true;
+          if (msg.toolResults?.some((tr) => tr.toolUseId === toolUseId)) return true;
         }
       }
     }
@@ -125,6 +103,7 @@ const AIChatGroupInner = ({
   highlightToolUseId,
   highlightColor,
   registerToolRef,
+  precedingSlash: precedingSlashProp,
 }: Readonly<AIChatGroupProps>): React.JSX.Element => {
   // Per-tab UI state for expansion (completely isolated per tab)
   const {
@@ -147,12 +126,15 @@ const AIChatGroupInner = ({
     return s.sessions.find((sess) => sess.id === id)?.isOngoing ?? false;
   });
 
-  // Per-tab session data subscriptions, falling back to global state
+  // Per-tab session data subscriptions, falling back to global state.
+  // NOTE: `conversation` is intentionally NOT subscribed here — it caused
+  // all ~16 visible AIChatGroups to fully re-render on every 3s refresh,
+  // re-running all memos (O(n) precedingSlash scan, enhanceAIGroup, etc).
+  // precedingSlash is now pre-computed and passed as a prop from ChatHistory.
   const {
     sessionClaudeMdStats,
     sessionContextStats,
     sessionPhaseInfo,
-    conversation,
     searchExpandedAIGroupIds,
     searchExpandedSubagentIds,
     searchCurrentDisplayItemId,
@@ -163,7 +145,6 @@ const AIChatGroupInner = ({
         sessionClaudeMdStats: td?.sessionClaudeMdStats ?? s.sessionClaudeMdStats,
         sessionContextStats: td?.sessionContextStats ?? s.sessionContextStats,
         sessionPhaseInfo: td?.sessionPhaseInfo ?? s.sessionPhaseInfo,
-        conversation: td?.conversation ?? s.conversation,
         searchExpandedAIGroupIds: s.searchExpandedAIGroupIds,
         searchExpandedSubagentIds: s.searchExpandedSubagentIds,
         searchCurrentDisplayItemId: s.searchCurrentDisplayItemId,
@@ -191,30 +172,10 @@ const AIChatGroupInner = ({
   const phaseNumber = sessionPhaseInfo?.aiGroupPhaseMap.get(aiGroup.id);
   const totalPhases = sessionPhaseInfo?.phases.length ?? 0;
 
-  // Find the preceding UserGroup for this AIGroup to extract slash info
-  // eslint-disable-next-line react-hooks/preserve-manual-memoization -- React Compiler can't preserve this; manual memo needed for O(n) traversal
-  const precedingSlash = useMemo(() => {
-    if (!conversation?.items) return undefined;
-
-    // Find the index of this AIGroup in the conversation
-    const aiGroupIndex = conversation.items.findIndex(
-      (item) => item.type === 'ai' && item.group.id === aiGroup.id
-    );
-
-    if (aiGroupIndex <= 0) return undefined;
-
-    // Look backwards for the nearest UserGroup
-    for (let i = aiGroupIndex - 1; i >= 0; i--) {
-      const item = conversation.items[i];
-      if (item.type === 'user') {
-        return extractPrecedingSlashInfo(item.group);
-      }
-      // Stop if we hit another AI group (shouldn't happen in normal flow)
-      if (item.type === 'ai') break;
-    }
-
-    return undefined;
-  }, [conversation?.items, aiGroup.id]);
+  // precedingSlash is pre-computed in ChatHistory and passed as prop.
+  // Previously this was an O(n) findIndex scan PER visible group PER refresh cycle,
+  // causing 16 × O(n) work on every 3s refresh for no benefit.
+  const precedingSlash = precedingSlashProp;
 
   // Enhance the AI group to get display-ready data
   const enhanced: EnhancedAIGroup = useMemo(
@@ -271,22 +232,29 @@ const AIChatGroupInner = ({
   const isExpanded =
     isAIGroupExpandedForTab(aiGroup.id) || containsHighlightedError || shouldExpandForSearch;
 
-  // Helper function to find the item ID containing the highlighted tool
+  // Helper function to find the item ID containing the highlighted tool.
+  // Subagent lookups use the precomputed displayMeta.toolUseIds set when
+  // available so we don't need to load the message body just to find an id.
   const findHighlightedItemId = useCallback(
     (toolUseId: string): string | null => {
       for (let i = 0; i < enhanced.displayItems.length; i++) {
         const item = enhanced.displayItems[i];
         if (item.type === 'tool' && item.tool.id === toolUseId) {
           return `tool-${item.tool.id}-${i}`;
         }
-        // For subagents, expand the subagent item
-        if (item.type === 'subagent' && item.subagent.messages) {
-          for (const msg of item.subagent.messages) {
-            if (
-              msg.toolCalls?.some((tc) => tc.id === toolUseId) ||
-              msg.toolResults?.some((tr) => tr.toolUseId === toolUseId)
-            ) {
-              return `subagent-${item.subagent.id}-${i}`;
+        if (item.type === 'subagent') {
+          const ids = item.subagent.displayMeta?.toolUseIds;
+          if (ids?.includes(toolUseId)) {
+            return `subagent-${item.subagent.id}-${i}`;
+          }
+          if (!ids && item.subagent.messages) {
+            for (const msg of item.subagent.messages) {
+              if (
+                msg.toolCalls?.some((tc) => tc.id === toolUseId) ||
+                msg.toolResults?.some((tr) => tr.toolUseId === toolUseId)
+              ) {
+                return `subagent-${item.subagent.id}-${i}`;
+              }
             }
           }
         }