diff --git a/src/renderer/src/components/terminal-pane/remote-runtime-pty-transport-host-absence-evidence.test.ts b/src/renderer/src/components/terminal-pane/remote-runtime-pty-transport-host-absence-evidence.test.ts
index 719aebfe795..813ffa7b5c1 100644
--- a/src/renderer/src/components/terminal-pane/remote-runtime-pty-transport-host-absence-evidence.test.ts
+++ b/src/renderer/src/components/terminal-pane/remote-runtime-pty-transport-host-absence-evidence.test.ts
@@ -1,4 +1,8 @@
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import type {
+  RuntimeMobileSessionTabsResult,
+  RuntimeMobileSessionTerminalClientTab
+} from '../../../../shared/runtime-types'
 import {
   createRemoteRuntimeTransportMocks,
   type MultiplexSubscriptionCallbacks
@@ -54,11 +58,227 @@ function readySnapshot(snapshotVersion: number): unknown {
   }
 }
 
+function splitLeaf(
+  leafId: string,
+  terminal: string | null,
+  isActive = false
+): RuntimeMobileSessionTerminalClientTab {
+  const tab = {
+    type: 'terminal' as const,
+    id: `host-tab-1::${leafId}`,
+    parentTabId: 'host-tab-1',
+    leafId,
+    title: `Terminal ${leafId}`,
+    isActive
+  }
+  return terminal === null
+    ? { ...tab, status: 'pending-handle', terminal: null }
+    : { ...tab, status: 'ready', terminal }
+}
+
+function hostTabs(
+  snapshotVersion: number,
+  tabs: RuntimeMobileSessionTerminalClientTab[],
+  retiredLeafIds: string[] = []
+): RuntimeMobileSessionTabsResult {
+  return {
+    worktree: 'id:wt-1',
+    publicationEpoch: 'epoch-1',
+    snapshotVersion,
+    activeGroupId: 'group-1',
+    activeTabId: tabs.find((tab) => tab.isActive)?.id ?? null,
+    activeTabType: tabs.length > 0 ? 'terminal' : null,
+    ...(retiredLeafIds.length > 0
+      ? {
+          retiredTerminalSurfaces: retiredLeafIds.map((leafId) => ({
+            parentTabId: 'host-tab-1',
+            leafId,
+            ptyId: `pty-${leafId}`,
+            terminal: `terminal-${leafId}`
+          }))
+        }
+      : {}),
+    tabs
+  }
+}
+
+/** Activation reports the pane's leaf pending; each listing answers in turn, the last one repeating. */
+function serveHostSession(
+  activated: RuntimeMobileSessionTabsResult,
+  listings: RuntimeMobileSessionTabsResult[]
+): void {
+  let listCount = 0
+  runtimeCall.mockImplementation(async (args: { method: string }) => {
+    if (args.method === 'session.tabs.activate') {
+      return { ok: true, result: activated }
+    }
+    if (args.method === 'session.tabs.list') {
+      const listing = listings[Math.min(listCount, listings.length - 1)]
+      listCount += 1
+      return { ok: true, result: listing }
+    }
+    return { ok: true, result: { terminal: { handle: 'duplicate-terminal' } } }
+  })
+}
+
+function sessionTabsListCount(): number {
+  return runtimeCall.mock.calls.filter((call) => call[0].method === 'session.tabs.list').length
+}
+
+const leaf2Pending = hostTabs(1, [
+  splitLeaf('leaf-1', 'terminal-1'),
+  splitLeaf('leaf-2', null, true)
+])
+const siblingOnly = hostTabs(2, [splitLeaf('leaf-1', 'terminal-1', true)])
+
 describe('remote runtime pty transport host absence evidence', () => {
   beforeEach(() => {
     resetRemoteRuntimeTransport()
   })
 
+  afterEach(() => {
+    vi.useRealTimers()
+  })
+
+  it('retires a split leaf once two listings agree it is gone while a sibling remains', async () => {
+    vi.useFakeTimers()
+    serveHostSession(leaf2Pending, [siblingOnly])
+    const { createRemoteRuntimePtyTransport } = await import('./remote-runtime-pty-transport')
+    const onError = vi.fn()
+    const transport = createRemoteRuntimePtyTransport('env-1', {
+      worktreeId: 'wt-1',
+      tabId: 'web-terminal-host-tab-1',
+      leafId: 'leaf-2'
+    })
+
+    const connect = transport.connect({ url: '', callbacks: { onError } })
+    await vi.advanceTimersByTimeAsync(450)
+
+    await expect(connect).resolves.toBeUndefined()
+    expect(onError).toHaveBeenCalledWith('Remote terminal was closed.')
+    expect(sessionTabsListCount()).toBe(2)
+    await Promise.resolve()
+    await Promise.resolve()
+    expect(
+      runtimeCall.mock.calls.some((call) => call[0].method.startsWith('session.tabs.close'))
+    ).toBe(false)
+  })
+
+  it('does not retire a split leaf on one sibling-only listing the host has not caught up with', async () => {
+    vi.useFakeTimers()
+    // An orchestrator opening several panes at once: the host publishes leaf-2 a moment after the
+    // first listing, so that listing carries only the sibling (#20917).
+    serveHostSession(leaf2Pending, [
+      siblingOnly,
+      hostTabs(3, [splitLeaf('leaf-1', 'terminal-1'), splitLeaf('leaf-2', 'terminal-2', true)])
+    ])
+    const { createRemoteRuntimePtyTransport } = await import('./remote-runtime-pty-transport')
+    const onError = vi.fn()
+    const transport = createRemoteRuntimePtyTransport('env-1', {
+      worktreeId: 'wt-1',
+      tabId: 'web-terminal-host-tab-1',
+      leafId: 'leaf-2'
+    })
+
+    const connect = transport.connect({ url: '', callbacks: { onError } })
+    await vi.advanceTimersByTimeAsync(450)
+
+    await expect(connect).resolves.toEqual({
+      id: 'remote:env-1@@terminal-2',
+      replay: '',
+      isReattach: true
+    })
+    expect(onError).not.toHaveBeenCalled()
+  })
+
+  it('retires a split leaf on the host retirement proof without a second listing', async () => {
+    vi.useFakeTimers()
+    serveHostSession(leaf2Pending, [
+      hostTabs(2, [splitLeaf('leaf-1', 'terminal-1', true)], ['leaf-2'])
+    ])
+    const { createRemoteRuntimePtyTransport } = await import('./remote-runtime-pty-transport')
+    const onError = vi.fn()
+    const transport = createRemoteRuntimePtyTransport('env-1', {
+      worktreeId: 'wt-1',
+      tabId: 'web-terminal-host-tab-1',
+      leafId: 'leaf-2'
+    })
+
+    const connect = transport.connect({ url: '', callbacks: { onError } })
+    await vi.advanceTimersByTimeAsync(450)
+
+    await expect(connect).resolves.toBeUndefined()
+    expect(onError).toHaveBeenCalledWith('Remote terminal was closed.')
+    expect(sessionTabsListCount()).toBe(1)
+  })
+
+  it('retires the last leaf of a tab on the host retirement proof', async () => {
+    vi.useFakeTimers()
+    // The retired leaf was the tab's only surface, so no sibling is left to read as absence.
+    serveHostSession(hostTabs(1, [splitLeaf('leaf-1', null, true)]), [hostTabs(2, [], ['leaf-1'])])
+    const { createRemoteRuntimePtyTransport } = await import('./remote-runtime-pty-transport')
+    const onError = vi.fn()
+    const transport = createRemoteRuntimePtyTransport('env-1', {
+      worktreeId: 'wt-1',
+      tabId: 'web-terminal-host-tab-1',
+      leafId: 'leaf-1'
+    })
+
+    const connect = transport.connect({ url: '', callbacks: { onError } })
+    await vi.advanceTimersByTimeAsync(450)
+
+    await expect(connect).resolves.toBeUndefined()
+    expect(onError).toHaveBeenCalledWith('Remote terminal was closed.')
+    expect(sessionTabsListCount()).toBe(1)
+  })
+
+  it('confirms absence from a listing that began after a sibling listing still in flight', async () => {
+    vi.useFakeTimers()
+    // Only the transport's own requests reach the RPC; the sibling listings below never do.
+    serveHostSession(leaf2Pending, [
+      hostTabs(4, [splitLeaf('leaf-1', 'terminal-1'), splitLeaf('leaf-2', 'terminal-2', true)])
+    ])
+    const { createRemoteRuntimePtyTransport } = await import('./remote-runtime-pty-transport')
+    const { listRemoteRuntimeSessionTabsDeduped } =
+      await import('@/runtime/remote-runtime-session-tabs-inflight')
+    const registerSiblingListing = (settleAfterMs: number): Promise<unknown> =>
+      listRemoteRuntimeSessionTabsDeduped({
+        environmentId: 'env-1',
+        worktreeId: 'wt-1',
+        load: () =>
+          new Promise((resolve) => {
+            setTimeout(() => resolve({ snapshot: siblingOnly }), settleAfterMs)
+          })
+      })
+
+    // A pane opened moments earlier owns the in-flight listing the transport first waits out.
+    const first = registerSiblingListing(200)
+    void first.then(() => {
+      // Another sibling takes the slot before the transport lists, so its first answer is still stale.
+      void registerSiblingListing(400)
+    })
+
+    const onError = vi.fn()
+    const transport = createRemoteRuntimePtyTransport('env-1', {
+      worktreeId: 'wt-1',
+      tabId: 'web-terminal-host-tab-1',
+      leafId: 'leaf-2'
+    })
+
+    const connect = transport.connect({ url: '', callbacks: { onError } })
+    await vi.advanceTimersByTimeAsync(1_500)
+
+    await expect(connect).resolves.toEqual({
+      id: 'remote:env-1@@terminal-2',
+      replay: '',
+      isReattach: true
+    })
+    expect(onError).not.toHaveBeenCalled()
+    // Both sibling listings were served from the in-flight cache, so the one RPC is the
+    // confirming request the transport started only after the pending sibling settled.
+    expect(sessionTabsListCount()).toBe(1)
+  })
+
   it('does not report a live host terminal as closed when activation answers tab_not_found', async () => {
     runtimeCall.mockImplementation(async (args: { method: string }) => {
       if (args.method === 'session.tabs.activate') {
diff --git a/src/renderer/src/components/terminal-pane/remote-runtime-pty-transport-split-leaf-activation.test.ts b/src/renderer/src/components/terminal-pane/remote-runtime-pty-transport-split-leaf-activation.test.ts
index e27a981e23b..c302c4d7dad 100644
--- a/src/renderer/src/components/terminal-pane/remote-runtime-pty-transport-split-leaf-activation.test.ts
+++ b/src/renderer/src/components/terminal-pane/remote-runtime-pty-transport-split-leaf-activation.test.ts
@@ -398,98 +398,6 @@ describe('createRemoteRuntimePtyTransport', () => {
     expect(latestSubscribePayload()).toMatchObject({ terminal: 'terminal-2' })
   })
 
-  it('stops polling when a requested split leaf disappears but siblings remain', async () => {
-    vi.useFakeTimers()
-    try {
-      runtimeCall.mockImplementation((args) => {
-        if (args.method === 'session.tabs.activate') {
-          return Promise.resolve({
-            ok: true,
-            result: {
-              worktree: 'id:wt-1',
-              publicationEpoch: 'epoch-1',
-              snapshotVersion: 1,
-              activeGroupId: 'group-1',
-              activeTabId: 'host-tab-1::leaf-2',
-              activeTabType: 'terminal',
-              tabs: [
-                {
-                  type: 'terminal',
-                  id: 'host-tab-1::leaf-1',
-                  parentTabId: 'host-tab-1',
-                  leafId: 'leaf-1',
-                  title: 'Terminal 1',
-                  isActive: false,
-                  status: 'ready',
-                  terminal: 'terminal-1'
-                },
-                {
-                  type: 'terminal',
-                  id: 'host-tab-1::leaf-2',
-                  parentTabId: 'host-tab-1',
-                  leafId: 'leaf-2',
-                  title: 'Terminal 2',
-                  isActive: true,
-                  status: 'pending-handle',
-                  terminal: null
-                }
-              ]
-            }
-          })
-        }
-        if (args.method === 'session.tabs.list') {
-          return Promise.resolve({
-            ok: true,
-            result: {
-              worktree: 'id:wt-1',
-              publicationEpoch: 'epoch-1',
-              snapshotVersion: 2,
-              activeGroupId: 'group-1',
-              activeTabId: 'host-tab-1::leaf-1',
-              activeTabType: 'terminal',
-              tabs: [
-                {
-                  type: 'terminal',
-                  id: 'host-tab-1::leaf-1',
-                  parentTabId: 'host-tab-1',
-                  leafId: 'leaf-1',
-                  title: 'Terminal 1',
-                  isActive: true,
-                  status: 'ready',
-                  terminal: 'terminal-1'
-                }
-              ]
-            }
-          })
-        }
-        return Promise.resolve({ ok: true, result: { terminal: { handle: 'duplicate-terminal' } } })
-      })
-      const { createRemoteRuntimePtyTransport } = await import('./remote-runtime-pty-transport')
-      const onError = vi.fn()
-      const transport = createRemoteRuntimePtyTransport('env-1', {
-        worktreeId: 'wt-1',
-        tabId: 'web-terminal-host-tab-1',
-        leafId: 'leaf-2'
-      })
-
-      const connect = transport.connect({ url: '', callbacks: { onError } })
-      await vi.advanceTimersByTimeAsync(150)
-
-      await expect(connect).resolves.toBeUndefined()
-      expect(onError).toHaveBeenCalledWith('Remote terminal was closed.')
-      expect(
-        runtimeCall.mock.calls.filter((call) => call[0].method === 'session.tabs.list')
-      ).toHaveLength(1)
-      await Promise.resolve()
-      await Promise.resolve()
-      expect(
-        runtimeCall.mock.calls.some((call) => call[0].method.startsWith('session.tabs.close'))
-      ).toBe(false)
-    } finally {
-      vi.useRealTimers()
-    }
-  })
-
   it('leaves a timed-out pending split untouched without closing its parent', async () => {
     vi.useFakeTimers()
     try {
diff --git a/src/renderer/src/components/terminal-pane/remote-runtime-pty-transport.ts b/src/renderer/src/components/terminal-pane/remote-runtime-pty-transport.ts
index d4d899526e6..be22ebfe3da 100644
--- a/src/renderer/src/components/terminal-pane/remote-runtime-pty-transport.ts
+++ b/src/renderer/src/components/terminal-pane/remote-runtime-pty-transport.ts
@@ -87,6 +87,7 @@ import {
   toHostSessionTabId
 } from '../../../../shared/terminal-surface-id'
 import { listRemoteRuntimeSessionTabsAfterCurrentInFlight } from '@/runtime/remote-runtime-session-tabs-inflight'
+import { hasRetirementProofForSurface } from '../../../../shared/terminal-retirement-proof-ledger'
 import { subscribeAcceptedWebSessionTerminalHandle } from '@/runtime/web-session-terminal-handle-events'
 import { hostSnapshotAffirmsWorktreeContents } from '@/runtime/host-session-snapshot-authority'
 import { runRemoteAgentSessionLaunch } from '@/runtime/remote-agent-session-launch'
@@ -760,6 +761,7 @@ export function createRemoteRuntimePtyTransport(
     let pollMs = HOST_SESSION_ATTACH_POLL_MS
     let nextRequest: 'activate' | 'list' = 'list'
     let activationOutcomeUnknown = false
+    let siblingOnlyAbsenceSeen = false
     while (isCurrent()) {
       const remainingMs = HOST_SESSION_ATTACH_TIMEOUT_MS - (Date.now() - startedAt)
       if (remainingMs <= 0) {
@@ -815,12 +817,29 @@ export function createRemoteRuntimePtyTransport(
         continue
       }
       if (!hasHostSessionTerminalSurface(snapshot, hostTabId)) {
+        // Why: host-attested retirement outranks every inference below, including the empty-tab republish guard.
+        if (
+          leafId &&
+          hasRetirementProofForSurface(snapshot.retiredTerminalSurfaces, {
+            parentTabId: hostTabId,
+            leafId
+          })
+        ) {
+          return false
+        }
         const siblingStillExists =
           getHostSessionTerminalSurfaces(snapshot, hostTabId, {
             matchRequestedLeaf: false
           }).length > 0
         if (siblingStillExists) {
-          return false
+          // Why: a split still publishing, or a sibling's stale listing joined late, reads exactly like a
+          // retired leaf; one listing proves nothing, so confirm on a second (#20917).
+          if (siblingOnlyAbsenceSeen) {
+            return false
+          }
+          siblingOnlyAbsenceSeen = true
+          nextRequest = 'list'
+          continue
         }
         // Why: a populated surface list missing only this leaf is positive absence, but a list carrying no
         // surface at all for the tab is a client-side snapshot of a host that may still be republishing.
@@ -828,6 +847,8 @@ export function createRemoteRuntimePtyTransport(
         nextRequest = 'list'
         continue
       }
+      // Why: a live sighting retracts the pending absence proof, as it does for orphan reconciliation.
+      siblingOnlyAbsenceSeen = false
       // Why: a host relaunch republishes the surface unmaterialized, and only activation can mint its PTY — list-only polling waits forever.
       nextRequest = activationOutcomeUnknown ? 'list' : 'activate'
     }
diff --git a/src/shared/terminal-retirement-proof-ledger.ts b/src/shared/terminal-retirement-proof-ledger.ts
index 4d570497f67..e9aa42db082 100644
--- a/src/shared/terminal-retirement-proof-ledger.ts
+++ b/src/shared/terminal-retirement-proof-ledger.ts
@@ -25,6 +25,14 @@ export function dropRetirementProofsForLiveSurfaces(
   return retired.filter((surface) => !live.has(surfaceKey(surface)))
 }
 
+/** The host's own removal evidence for a pane, whatever handle it last held. */
+export function hasRetirementProofForSurface(
+  retired: readonly RuntimeMobileSessionRetiredTerminalSurface[] | undefined,
+  surface: { parentTabId: string; leafId: string }
+): boolean {
+  return retired?.some((proof) => surfaceKey(proof) === surfaceKey(surface)) === true
+}
+
 /** Newest evidence wins per exact identity; the oldest identities fall off past the cap. */
 export function appendRetiredTerminalSurfaceProofs(
   existing: readonly RuntimeMobileSessionRetiredTerminalSurface[] | undefined,