diff --git a/src/image-watcher.ts b/src/image-watcher.ts
index f57edd9d..eb5e4443 100644
--- a/src/image-watcher.ts
+++ b/src/image-watcher.ts
@@ -87,6 +87,7 @@ export class ImageWatcher extends EventEmitter {
 
   constructor() {
     super();
+    this.setMaxListeners(50);
   }
 
   // ========== Public API ==========
diff --git a/src/session.ts b/src/session.ts
index 52bf0745..839814de 100644
--- a/src/session.ts
+++ b/src/session.ts
@@ -369,6 +369,7 @@ export class Session extends EventEmitter {
     niceConfig?: NiceConfig;  // Nice prioritying configuration
   }) {
     super();
+    this.setMaxListeners(25);
 
     // Default error handler prevents unhandled 'error' events from crashing the process.
     // Server attaches its own handler after construction — this is a safety net for the gap.
diff --git a/src/state-store.ts b/src/state-store.ts
index be786691..e87073d2 100644
--- a/src/state-store.ts
+++ b/src/state-store.ts
@@ -64,6 +64,9 @@ export class StateStore {
   private consecutiveSaveFailures: number = 0;
   private circuitBreakerOpen: boolean = false;
 
+  // Guard against concurrent saveNowAsync() calls (debounce can race with in-flight write)
+  private _saveInFlight: Promise<void> | null = null;
+
   constructor(filePath?: string) {
     this.filePath = filePath || join(homedir(), '.claudeman', 'state.json');
     this.ralphStatePath = this.filePath.replace('.json', '-inner.json');
@@ -130,8 +133,25 @@ export class StateStore {
    * Async version of saveNow — used by the debounced save() path.
    * Uses non-blocking fs.promises to avoid blocking the event loop during
    * the debounced write cycle. For synchronous shutdown flush, use saveNow().
+   *
+   * Guards against concurrent execution: if a save is already in flight,
+   * waits for it to complete then re-checks dirty flag before starting another.
    */
   async saveNowAsync(): Promise<void> {
+    if (this._saveInFlight) {
+      await this._saveInFlight;
+      // After waiting, re-check if still dirty (the previous save may have handled it)
+      if (!this.dirty) return;
+    }
+    this._saveInFlight = this._doSaveAsync();
+    try {
+      await this._saveInFlight;
+    } finally {
+      this._saveInFlight = null;
+    }
+  }
+
+  private async _doSaveAsync(): Promise<void> {
     if (this.saveTimeout) {
       clearTimeout(this.saveTimeout);
       this.saveTimeout = null;
diff --git a/src/subagent-watcher.ts b/src/subagent-watcher.ts
index b7559bef..f38eb22e 100644
--- a/src/subagent-watcher.ts
+++ b/src/subagent-watcher.ts
@@ -177,6 +177,7 @@ export class SubagentWatcher extends EventEmitter {
 
   constructor() {
     super();
+    this.setMaxListeners(50);
   }
 
   /**
diff --git a/src/tmux-manager.ts b/src/tmux-manager.ts
index 11df98a2..3d9fa8c1 100644
--- a/src/tmux-manager.ts
+++ b/src/tmux-manager.ts
@@ -141,6 +141,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
 
   constructor() {
     super();
+    this.setMaxListeners(50);
     if (!IS_TEST_MODE) {
       this.loadSessions();
     }
diff --git a/src/web/public/app.js b/src/web/public/app.js
index 7fd1e85f..0861e90f 100644
--- a/src/web/public/app.js
+++ b/src/web/public/app.js
@@ -3097,6 +3097,8 @@ class ClaudemanApp {
     this.terminalBuffers.clear();
     this.terminalBufferCache.clear();
     this.projectInsights.clear();
+    this.teams.clear();
+    this.teamTasks.clear();
     // Clear all idle timers to prevent stale timers from firing
     for (const timer of this.idleTimers.values()) {
       clearTimeout(timer);
diff --git a/src/web/server.ts b/src/web/server.ts
index 9edaa67b..bb353c22 100644
--- a/src/web/server.ts
+++ b/src/web/server.ts
@@ -115,6 +115,8 @@ const DEC_SYNC_START = '\x1b[?2026h';  // Begin synchronized update
 const DEC_SYNC_END = '\x1b[?2026l';    // End synchronized update (flush to screen)
 // State update debounce interval (batch expensive toDetailedState() calls)
 const STATE_UPDATE_DEBOUNCE_INTERVAL = 500;
+// Cache TTL for getLightSessionsState() — avoids re-serializing all sessions on every SSE init / /api/sessions call
+const SESSIONS_LIST_CACHE_TTL = 1000;
 // Scheduled runs cleanup interval (check every 5 minutes)
 const SCHEDULED_CLEANUP_INTERVAL = 5 * 60 * 1000;
 // Completed scheduled runs max age (1 hour)
@@ -373,6 +375,8 @@ export class WebServer extends EventEmitter {
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   private cachedLightState: { data: Record<string, unknown>; timestamp: number } | null = null;
   private static readonly LIGHT_STATE_CACHE_TTL_MS = 1000;
+  // Cached sessions list for getLightSessionsState() (avoids re-serializing all sessions on every call)
+  private cachedSessionsList: { data: unknown[]; timestamp: number } | null = null;
   // Token recording for daily stats (track what's been recorded to avoid double-counting)
   private lastRecordedTokens: Map<string, { input: number; output: number }> = new Map();
   private tokenRecordingTimer: NodeJS.Timeout | null = null;
@@ -382,6 +386,7 @@ export class WebServer extends EventEmitter {
   private pendingRespawnStarts: Map<string, NodeJS.Timeout> = new Map();
   // Active plan orchestrators (for cancellation via API)
   private activePlanOrchestrators: Map<string, PlanOrchestrator> = new Map();
+  private persistDebounceTimers: Map<string, ReturnType<typeof setTimeout>> = new Map();
   // Grace period before starting restored respawn controllers (2 minutes)
   private static readonly RESPAWN_RESTORE_GRACE_PERIOD_MS = 2 * 60 * 1000;
   // Stored listener handlers for cleanup
@@ -401,6 +406,7 @@ export class WebServer extends EventEmitter {
   } | null = null;
   constructor(port: number = 3000, https: boolean = false, testMode: boolean = false) {
     super();
+    this.setMaxListeners(0);
     this.port = port;
     this.https = https;
     this.testMode = testMode;
@@ -3438,8 +3444,21 @@ NOW: Generate the implementation plan for the task above. Think step by step.`;
     }
   }
 
-  /** Persists full session state including respawn config to state.json */
+  /** Debounced wrapper — coalesces rapid persistSessionState calls per session */
   private persistSessionState(session: Session): void {
+    const existing = this.persistDebounceTimers.get(session.id);
+    if (existing) clearTimeout(existing);
+    this.persistDebounceTimers.set(session.id, setTimeout(() => {
+      this.persistDebounceTimers.delete(session.id);
+      // Session may have been removed during debounce
+      if (this.sessions.has(session.id)) {
+        this._persistSessionStateNow(session);
+      }
+    }, 100));
+  }
+
+  /** Persists full session state including respawn config to state.json */
+  private _persistSessionStateNow(session: Session): void {
     const state = session.toState();
     const controller = this.respawnControllers.get(session.id);
     if (controller) {
@@ -4341,9 +4360,15 @@ NOW: Generate the implementation plan for the task above. Think step by step.`;
    * on-demand when switching tabs via /api/sessions/:id/buffer
    */
   private getLightSessionsState() {
+    const now = Date.now();
+    if (this.cachedSessionsList && (now - this.cachedSessionsList.timestamp) < SESSIONS_LIST_CACHE_TTL) {
+      return this.cachedSessionsList.data;
+    }
     // getSessionStateWithRespawn already uses toLightDetailedState() which
     // excludes terminalBuffer and textOutput — no extra stripping needed
-    return Array.from(this.sessions.values()).map(s => this.getSessionStateWithRespawn(s));
+    const data = Array.from(this.sessions.values()).map(s => this.getSessionStateWithRespawn(s));
+    this.cachedSessionsList = { data, timestamp: now };
+    return data;
   }
 
   // Clean up old completed scheduled runs
@@ -4449,9 +4474,10 @@ NOW: Generate the implementation plan for the task above. Think step by step.`;
   }
 
   private broadcast(event: string, data: unknown): void {
-    // Invalidate light state cache on any state-changing broadcast
+    // Invalidate caches on any state-changing broadcast
     if (event.startsWith('session:') || event === 'respawn:') {
       this.cachedLightState = null;
+      this.cachedSessionsList = null;
     }
     // Performance optimization: serialize JSON once for all clients
     let message: string;
@@ -5000,6 +5026,20 @@ NOW: Generate the implementation plan for the task above. Think step by step.`;
     // Stop multiplexer and flush pending saves
     this.mux.destroy();
 
+    // Flush any pending persist-debounce timers and persist dirty sessions
+    for (const [sessionId, timer] of this.persistDebounceTimers) {
+      clearTimeout(timer);
+      const session = this.sessions.get(sessionId);
+      if (session) {
+        this._persistSessionStateNow(session);
+      }
+    }
+    this.persistDebounceTimers.clear();
+
+    // Clear cached state
+    this.cachedLightState = null;
+    this.cachedSessionsList = null;
+
     // Clear all pending respawn start timers (from restoration grace period)
     for (const timer of this.pendingRespawnStarts.values()) {
       clearTimeout(timer);