From f37258a21d10aeeaed3f8bee8184373112e89601 Mon Sep 17 00:00:00 2001
From: Neil <4138956+nwparker@users.noreply.github.com>
Date: Sun, 31 May 2026 04:46:49 -0700
Subject: [PATCH] perf: bound branch rename dedupe cache (#4115)

---
 .../first-work-branch-rename.test.ts          | 36 +++++++++++++++++++
 .../agent-hooks/first-work-branch-rename.ts   | 17 ++++++++-
 2 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/src/main/agent-hooks/first-work-branch-rename.test.ts b/src/main/agent-hooks/first-work-branch-rename.test.ts
index 80d5c493833..a9255541af4 100644
--- a/src/main/agent-hooks/first-work-branch-rename.test.ts
+++ b/src/main/agent-hooks/first-work-branch-rename.test.ts
@@ -38,6 +38,7 @@ vi.mock('../text-generation/commit-message-agent-environment', () => ({
 vi.mock('../ipc/worktree-logic', () => ({ computeBranchName: computeBranchNameMock }))
 
 import {
+  FIRST_WORK_BRANCH_RENAME_SETTLED_CACHE_LIMIT,
   maybeAutoRenameBranchOnFirstWork,
   resetFirstWorkBranchRenameState,
   type FirstWorkBranchRenameDeps,
@@ -203,6 +204,41 @@ describe('maybeAutoRenameBranchOnFirstWork', () => {
     expect(generateBranchNameMock).not.toHaveBeenCalled()
   })
 
+  it('bounds settled worktree dedupe while keeping recent entries', async () => {
+    gitExecFileAsyncMock.mockImplementation(
+      gitResponder({ currentBranch: 'you/my-feature', hasUpstream: false })
+    )
+    const { deps } = makeDeps()
+    const firstWorktreeId = `${REPO_ID}${WORKTREE_ID_SEPARATOR}/repo/wt-0`
+    const lastWorktreeId = `${REPO_ID}${WORKTREE_ID_SEPARATOR}/repo/wt-${FIRST_WORK_BRANCH_RENAME_SETTLED_CACHE_LIMIT}`
+
+    for (let index = 0; index <= FIRST_WORK_BRANCH_RENAME_SETTLED_CACHE_LIMIT; index += 1) {
+      await maybeAutoRenameBranchOnFirstWork(
+        workingEvent({
+          tabId: undefined,
+          paneKey: '',
+          worktreeId: `${REPO_ID}${WORKTREE_ID_SEPARATOR}/repo/wt-${index}`
+        }),
+        deps
+      )
+    }
+    expect(gitExecFileAsyncMock).toHaveBeenCalledTimes(
+      FIRST_WORK_BRANCH_RENAME_SETTLED_CACHE_LIMIT + 1
+    )
+
+    gitExecFileAsyncMock.mockClear()
+    await maybeAutoRenameBranchOnFirstWork(
+      workingEvent({ tabId: undefined, paneKey: '', worktreeId: firstWorktreeId }),
+      deps
+    )
+    await maybeAutoRenameBranchOnFirstWork(
+      workingEvent({ tabId: undefined, paneKey: '', worktreeId: lastWorktreeId }),
+      deps
+    )
+
+    expect(gitExecFileAsyncMock).toHaveBeenCalledTimes(1)
+  })
+
   it('retries on a later event after a transient failure (does not poison the worktree)', async () => {
     generateBranchNameMock.mockResolvedValueOnce({ success: false, error: 'agent not ready' })
     const { deps, onRenamed } = makeDeps()
diff --git a/src/main/agent-hooks/first-work-branch-rename.ts b/src/main/agent-hooks/first-work-branch-rename.ts
index 20a73d753ec..59bd8f04403 100644
--- a/src/main/agent-hooks/first-work-branch-rename.ts
+++ b/src/main/agent-hooks/first-work-branch-rename.ts
@@ -68,6 +68,7 @@ export type FirstWorkBranchRenameDeps = {
 // settled, so the real first prompt can still succeed on a later event.
 const inFlightWorktreeIds = new Set<string>()
 const settledWorktreeIds = new Set<string>()
+export const FIRST_WORK_BRANCH_RENAME_SETTLED_CACHE_LIMIT = 500
 
 /** Test seam: clear the per-process dedupe sets. */
 export function resetFirstWorkBranchRenameState(): void {
@@ -75,6 +76,20 @@ export function resetFirstWorkBranchRenameState(): void {
   settledWorktreeIds.clear()
 }
 
+function rememberSettledWorktreeId(worktreeId: string): void {
+  // Why: the app can see unbounded worktree ids over a long session; evicting
+  // oldest entries trades a rare re-probe for bounded process memory.
+  settledWorktreeIds.delete(worktreeId)
+  settledWorktreeIds.add(worktreeId)
+  while (settledWorktreeIds.size > FIRST_WORK_BRANCH_RENAME_SETTLED_CACHE_LIMIT) {
+    const oldest = settledWorktreeIds.values().next().value
+    if (typeof oldest !== 'string') {
+      return
+    }
+    settledWorktreeIds.delete(oldest)
+  }
+}
+
 export async function maybeAutoRenameBranchOnFirstWork(
   event: FirstWorkBranchRenameEvent,
   deps: FirstWorkBranchRenameDeps
@@ -107,7 +122,7 @@ export async function maybeAutoRenameBranchOnFirstWork(
     // ineligible); false means a transient bail that should retry later.
     const settled = await runAutoRename(worktreeId, prompt, event.assistantMessage, deps)
     if (settled) {
-      settledWorktreeIds.add(worktreeId)
+      rememberSettledWorktreeId(worktreeId)
     }
   } catch (error) {
     // Why: best-effort, opt-in convenience. A failure must never disrupt the