diff --git a/apps/ui/src/components/layout/project-switcher/project-switcher.tsx b/apps/ui/src/components/layout/project-switcher/project-switcher.tsx
index e3c14fc6..516599d6 100644
--- a/apps/ui/src/components/layout/project-switcher/project-switcher.tsx
+++ b/apps/ui/src/components/layout/project-switcher/project-switcher.tsx
@@ -1,4 +1,4 @@
-import { useState, useCallback, useEffect } from 'react';
+import { useState, useCallback, useEffect, startTransition } from 'react';
 import { Plus, Bug, FolderOpen, BookOpen } from 'lucide-react';
 import { useNavigate, useLocation } from '@tanstack/react-router';
 import { cn, isMac } from '@/lib/utils';
@@ -112,9 +112,17 @@ export function ProjectSwitcher() {
         // Continue with switch even if initialization fails -
         // the project may already be initialized
       }
-      setCurrentProject(project);
-      // Navigate to board view when switching projects
-      navigate({ to: '/board' });
+      // Wrap in startTransition to let React batch the project switch and
+      // navigation into a single low-priority update. Without this, the two
+      // synchronous calls fire separate renders where currentProject points
+      // to the new project but per-project state (worktrees, features) is
+      // still stale, causing a cascade of effects and store mutations that
+      // can trigger React error #185 (maximum update depth exceeded).
+      startTransition(() => {
+        setCurrentProject(project);
+        // Navigate to board view when switching projects
+        navigate({ to: '/board' });
+      });
     },
     [setCurrentProject, navigate]
   );
diff --git a/apps/ui/src/components/views/board-view.tsx b/apps/ui/src/components/views/board-view.tsx
index 10ca5dfe..e57e0201 100644
--- a/apps/ui/src/components/views/board-view.tsx
+++ b/apps/ui/src/components/views/board-view.tsx
@@ -478,6 +478,13 @@ export function BoardView() {
 
   // Get the branch for the currently selected worktree
   // Find the worktree that matches the current selection, or use main worktree
+  //
+  // IMPORTANT: Stabilize the returned object reference using a ref to prevent
+  // cascading re-renders during project switches. The spread `{ ...found, ... }`
+  // creates a new object every time, even when the underlying data is identical.
+  // Without stabilization, the new reference propagates to useAutoMode and other
+  // consumers, contributing to the re-render cascade that triggers React error #185.
+  const prevSelectedWorktreeRef = useRef<WorktreeInfo | undefined>(undefined);
   const selectedWorktree = useMemo((): WorktreeInfo | undefined => {
     let found;
     let usedFallback = false;
@@ -495,9 +502,12 @@ export function BoardView() {
         usedFallback = true;
       }
     }
-    if (!found) return undefined;
+    if (!found) {
+      prevSelectedWorktreeRef.current = undefined;
+      return undefined;
+    }
     // Ensure all required WorktreeInfo fields are present
-    return {
+    const result: WorktreeInfo = {
       ...found,
       isCurrent:
         found.isCurrent ??
@@ -508,6 +518,21 @@ export function BoardView() {
             : found.isMain),
       hasWorktree: found.hasWorktree ?? true,
     };
+    // Return the previous reference if the key fields haven't changed,
+    // preventing downstream hooks from seeing a "new" worktree on every render.
+    const prev = prevSelectedWorktreeRef.current;
+    if (
+      prev &&
+      prev.path === result.path &&
+      prev.branch === result.branch &&
+      prev.isMain === result.isMain &&
+      prev.isCurrent === result.isCurrent &&
+      prev.hasWorktree === result.hasWorktree
+    ) {
+      return prev;
+    }
+    prevSelectedWorktreeRef.current = result;
+    return result;
   }, [worktrees, currentWorktreePath]);
 
   // Auto mode hook - pass current worktree to get worktree-specific state
diff --git a/apps/ui/src/hooks/use-auto-mode.ts b/apps/ui/src/hooks/use-auto-mode.ts
index 1e2423f8..bbd3842b 100644
--- a/apps/ui/src/hooks/use-auto-mode.ts
+++ b/apps/ui/src/hooks/use-auto-mode.ts
@@ -252,10 +252,19 @@ export function useAutoMode(worktree?: WorktreeInfo) {
     }
   }, [branchName, currentProject, setAutoModeRunning]);
 
-  // On mount, query backend for current auto loop status and sync UI state.
+  // On mount (and when refreshStatus identity changes, e.g. project switch),
+  // query backend for current auto loop status and sync UI state.
   // This handles cases where the backend is still running after a page refresh.
+  //
+  // IMPORTANT: Debounce with a short delay to prevent a synchronous cascade
+  // during project switches. Without this, the sequence is:
+  //   refreshStatus() → setAutoModeRunning() → store update → re-render →
+  //   other effects fire → more store updates → React error #185.
+  // The 150ms delay lets React settle the initial mount renders before we
+  // trigger additional store mutations from the API response.
   useEffect(() => {
-    void refreshStatus();
+    const timer = setTimeout(() => void refreshStatus(), 150);
+    return () => clearTimeout(timer);
   }, [refreshStatus]);
 
   // Periodic polling fallback when WebSocket events are stale.
diff --git a/apps/ui/src/store/ui-cache-store.ts b/apps/ui/src/store/ui-cache-store.ts
index 123e06c2..bf8415f5 100644
--- a/apps/ui/src/store/ui-cache-store.ts
+++ b/apps/ui/src/store/ui-cache-store.ts
@@ -113,8 +113,25 @@ export function syncUICache(appState: {
   if ('collapsedNavSections' in appState) {
     update.cachedCollapsedNavSections = appState.collapsedNavSections;
   }
-  if ('currentWorktreeByProject' in appState) {
-    update.cachedCurrentWorktreeByProject = appState.currentWorktreeByProject;
+  if ('currentWorktreeByProject' in appState && appState.currentWorktreeByProject) {
+    // Sanitize on write: only persist entries where path is null (main branch).
+    // Non-null paths point to worktree directories on disk that may be deleted
+    // while the app is not running. Persisting stale paths can cause crash loops
+    // on restore (the board renders with an invalid selection, the error boundary
+    // reloads, which restores the same bad cache). This mirrors the sanitization
+    // in restoreFromUICache() for defense-in-depth.
+    const sanitized: Record<string, { path: string | null; branch: string }> = {};
+    for (const [projectPath, worktree] of Object.entries(appState.currentWorktreeByProject)) {
+      if (
+        typeof worktree === 'object' &&
+        worktree !== null &&
+        'path' in worktree &&
+        worktree.path === null
+      ) {
+        sanitized[projectPath] = worktree;
+      }
+    }
+    update.cachedCurrentWorktreeByProject = sanitized;
   }
 
   if (Object.keys(update).length > 0) {