perf(renderer): FIFO-cap recentlyClosedAgentStatusTabIds (#7645)

recentlyClosedAgentStatusTabIds (agent-status store) suppresses late
hook/status events for a just-closed terminal tab. It was only ever
added to — one `true` entry per agent-tab close, keyed by the ephemeral
tabId, never deleted or capped — so it grew for the renderer's whole
session. It's the renderer twin of the main-process
closedAgentStatusTabIds set that #7561 already FIFO-capped.

Fix: bound it to the 1024 most-recent closed tabs via delete-then-set
LRU with oldest-key eviction (Record key order is insertion order),
mirroring #7561. A status event for a tab closed >1024 tabs ago cannot
still arrive, so suppression behavior is unchanged.

Test (red->green): closing 1029 tabs leaves exactly 1024 markers with
the oldest evicted and the most-recent retained; without the cap all
1029 persist.

src/renderer/src/store/slices/agent-status-drop-ipc.test.ts

@@ -2,6 +2,7 @@ import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import type { AgentStatusEntry } from '../../../../shared/agent-status-types'
 import type { TerminalTab } from '../../../../shared/types'
 import type { RetainedAgentEntry } from './agent-status'
+import { RECENTLY_CLOSED_AGENT_STATUS_TAB_IDS_MAX } from './agent-status'
 import { createTestStore } from './store-test-helpers'
 
 // Why: dropAgentStatus and dismissRetainedAgentsByWorktree mirror the renderer-
@@ -119,6 +120,24 @@ describe('dropAgentStatusByTabPrefix -> IPC fan-out', () => {
       'tab-new': true
     })
   })
+
+  it('FIFO-caps recentlyClosedAgentStatusTabIds so it cannot grow unbounded', () => {
+    stubWindowApi()
+    const store = createTestStore()
+    const cap = RECENTLY_CLOSED_AGENT_STATUS_TAB_IDS_MAX
+
+    for (let i = 0; i < cap + 5; i++) {
+      store.getState().dropAgentStatusByTabPrefix(`tab-${i}`)
+    }
+
+    const closed = store.getState().recentlyClosedAgentStatusTabIds
+    expect(Object.keys(closed)).toHaveLength(cap)
+    // Oldest evicted, most-recent retained (a status event for a tab closed
+    // >cap tabs ago cannot still arrive, so suppression is unaffected).
+    expect(closed['tab-0']).toBeUndefined()
+    expect(closed['tab-4']).toBeUndefined()
+    expect(closed[`tab-${cap + 4}`]).toBe(true)
+  })
 })
 
 describe('dismissRetainedAgentsByWorktree → IPC fan-out', () => {

src/renderer/src/store/slices/agent-status.ts

@@ -733,6 +733,35 @@ function getLaunchConfigForEntry(
     : undefined
 }
 
+// Why: the renderer twin of the main-process closedAgentStatusTabIds set that
+// #7561 FIFO-capped. It suppresses late hook/status events for a just-closed tab,
+// so it must outlive the tab briefly — but tabId is ephemeral and it was only
+// ever added to, growing one entry per tab-close for the renderer's whole life.
+export const RECENTLY_CLOSED_AGENT_STATUS_TAB_IDS_MAX = 1024
+
+// delete-then-set for LRU recency, then evict the oldest keys past the cap (Record
+// key order is insertion order for non-integer string keys). A status event for a
+// tab closed >MAX tabs ago cannot still arrive, so eviction is safe.
+function boundRecentlyClosedAgentStatusTabIds(
+  existing: Record<string, true>,
+  tabId: string
+): Record<string, true> {
+  const next: Record<string, true> = {}
+  for (const key of Object.keys(existing)) {
+    if (key !== tabId) {
+      next[key] = true
+    }
+  }
+  next[tabId] = true
+  const keys = Object.keys(next)
+  if (keys.length > RECENTLY_CLOSED_AGENT_STATUS_TAB_IDS_MAX) {
+    for (const stale of keys.slice(0, keys.length - RECENTLY_CLOSED_AGENT_STATUS_TAB_IDS_MAX)) {
+      delete next[stale]
+    }
+  }
+  return next
+}
+
 function getLaunchConfigForStatusMetadata(
   state: AppState,
   metadata: AgentLaunchConfigStatusMetadata
@@ -1632,10 +1661,10 @@ export const createAgentStatusSlice: StateCreator<AppState, [], [], AgentStatusS
             delete nextAck[k]
           }
         }
-        const nextClosedTabs: Record<string, true> = {
-          ...s.recentlyClosedAgentStatusTabIds,
-          [tabIdPrefix]: true
-        }
+        const nextClosedTabs = boundRecentlyClosedAgentStatusTabIds(
+          s.recentlyClosedAgentStatusTabIds,
+          tabIdPrefix
+        )
 
         if (
           liveKeys.length === 0 &&