From 36384f17f41caa5cdbdf12c3e860d64ef6fe622c Mon Sep 17 00:00:00 2001
From: Neil <4138956+nwparker@users.noreply.github.com>
Date: Mon, 1 Jun 2026 15:56:01 -0700
Subject: [PATCH] Avoid no-op worktree activation fanout (#4416)

---
 docs/renderer-memory-profile-2026-06-01.md    | 13 +++++
 .../src/store/slices/store-cascades.test.ts   | 56 +++++++++++++++++++
 src/renderer/src/store/slices/worktrees.ts    | 23 +++++++-
 3 files changed, 91 insertions(+), 1 deletion(-)

diff --git a/docs/renderer-memory-profile-2026-06-01.md b/docs/renderer-memory-profile-2026-06-01.md
index d047ee525..2501e7b8b 100644
--- a/docs/renderer-memory-profile-2026-06-01.md
+++ b/docs/renderer-memory-profile-2026-06-01.md
@@ -129,3 +129,16 @@ The follow-up extends the existing tab-registration wait from page-specific
 creation to worktree/global wake flows. Runtime commands now wait for the
 renderer's actual `browser:registerGuest` IPC before routing automation, with
 the same timeout fallback used by tab creation.
+
+## Follow-up: Worktree Activation No-Op Fanout
+
+The next renderer-store check found that repeated activation of an already
+active, already-reconciled worktree could still publish a new Zustand root state
+because `setActiveWorktree` rebuilt `activeTabTypeByWorktree` even when its
+stored value was unchanged. That woke every store subscriber, including session
+persistence and runtime graph sync, for a visible no-op.
+
+The follow-up preserves the existing state reference when all derived active
+fields, unread state, and first-activation bookkeeping are unchanged. A
+regression test subscribes to the store and asserts that reselecting the
+already-active reconciled worktree does not notify subscribers.
diff --git a/src/renderer/src/store/slices/store-cascades.test.ts b/src/renderer/src/store/slices/store-cascades.test.ts
index db91aa744..15f64b127 100644
--- a/src/renderer/src/store/slices/store-cascades.test.ts
+++ b/src/renderer/src/store/slices/store-cascades.test.ts
@@ -761,6 +761,62 @@ describe('setActiveWorktree', () => {
     expect(store.getState().rightSidebarTab).toBe('checks')
   })
 
+  it('does not notify subscribers when reselecting the already-active reconciled worktree', () => {
+    const store = createTestStore()
+    const wt = 'repo1::/path/wt1'
+    const tabId = 'terminal-1'
+    const groupId = 'group-1'
+
+    seedStore(store, {
+      worktreesByRepo: {
+        repo1: [makeWorktree({ id: wt, repoId: 'repo1', path: '/path/wt1' })]
+      },
+      activeWorktreeId: wt,
+      activeTabId: tabId,
+      activeTabType: 'terminal',
+      activeTabTypeByWorktree: { [wt]: 'terminal' },
+      tabsByWorktree: {
+        [wt]: [makeTab({ id: tabId, worktreeId: wt, ptyId: 'pty-1' })]
+      },
+      ptyIdsByTabId: { [tabId]: ['pty-1'] },
+      unifiedTabsByWorktree: {
+        [wt]: [
+          makeUnifiedTab({
+            id: tabId,
+            entityId: tabId,
+            worktreeId: wt,
+            groupId,
+            contentType: 'terminal'
+          })
+        ]
+      },
+      groupsByWorktree: {
+        [wt]: [
+          makeTabGroup({
+            id: groupId,
+            worktreeId: wt,
+            activeTabId: tabId,
+            tabOrder: [tabId]
+          })
+        ]
+      },
+      activeGroupIdByWorktree: { [wt]: groupId },
+      everActivatedWorktreeIds: new Set([wt]),
+      refreshGitHubForWorktree: vi.fn(),
+      refreshGitHubForWorktreeIfStale: vi.fn()
+    })
+
+    const before = store.getState()
+    const listener = vi.fn()
+    const unsubscribe = store.subscribe(listener)
+
+    store.getState().setActiveWorktree(wt)
+
+    unsubscribe()
+    expect(listener).not.toHaveBeenCalled()
+    expect(store.getState()).toBe(before)
+  })
+
   it('does not clobber the current right sidebar tab when clearing the active worktree', () => {
     const store = createTestStore()
 
diff --git a/src/renderer/src/store/slices/worktrees.ts b/src/renderer/src/store/slices/worktrees.ts
index 39005b286..5a8a8899e 100644
--- a/src/renderer/src/store/slices/worktrees.ts
+++ b/src/renderer/src/store/slices/worktrees.ts
@@ -2145,12 +2145,33 @@ export const createWorktreeSlice: StateCreator<AppState, [], [], WorktreeSlice>
         ? applyDetectedWorktreeUpdates(s.detectedWorktreesByRepo, worktreeId, metaUpdates)
         : s.detectedWorktreesByRepo
 
+      const nextActiveTabTypeByWorktree =
+        s.activeTabTypeByWorktree[worktreeId] === activeTabType
+          ? s.activeTabTypeByWorktree
+          : { ...s.activeTabTypeByWorktree, [worktreeId]: activeTabType }
+      const hasStateChange =
+        s.activeWorktreeId !== worktreeId ||
+        s.activeFileId !== activeFileId ||
+        s.activeBrowserTabId !== activeBrowserTabId ||
+        s.activeTabType !== activeTabType ||
+        s.activeTabId !== activeTabId ||
+        nextActiveTabTypeByWorktree !== s.activeTabTypeByWorktree ||
+        nextEverActivated !== s.everActivatedWorktreeIds ||
+        nextWorktrees !== s.worktreesByRepo ||
+        nextDetectedWorktrees !== s.detectedWorktreesByRepo
+      if (!hasStateChange) {
+        // Why: repeated activation of the already-active worktree can come from
+        // clicks, IPC, and automation restore paths. Preserve the root Zustand
+        // reference so session persistence/runtime sync do not fan out on a no-op.
+        return s
+      }
+
       return {
         activeWorktreeId: worktreeId,
         activeFileId,
         activeBrowserTabId,
         activeTabType,
-        activeTabTypeByWorktree: { ...s.activeTabTypeByWorktree, [worktreeId]: activeTabType },
+        activeTabTypeByWorktree: nextActiveTabTypeByWorktree,
         activeTabId,
         everActivatedWorktreeIds: nextEverActivated,
         ...(nextWorktrees !== s.worktreesByRepo ? { worktreesByRepo: nextWorktrees } : {}),