diff --git a/src/renderer/src/components/terminal-pane/terminal-pane-split-with-inherited-cwd.test.ts b/src/renderer/src/components/terminal-pane/terminal-pane-split-with-inherited-cwd.test.ts
index 40b549126fd..39b300de69d 100644
--- a/src/renderer/src/components/terminal-pane/terminal-pane-split-with-inherited-cwd.test.ts
+++ b/src/renderer/src/components/terminal-pane/terminal-pane-split-with-inherited-cwd.test.ts
@@ -6,13 +6,24 @@ import { splitTerminalPaneWithInheritedCwd } from './terminal-pane-split-with-in
 import { createDeferred } from './pty-connection-test-async'
 import type { splitPaneInMain, splitServerPane } from './terminal-pane-split-in-main'
 
-const mocks = vi.hoisted(() => ({
-  layoutOwnerIsMain: false,
-  recordCreatedTerminalPaneSplit: vi.fn(),
-  resolveSplitCwd: vi.fn(),
-  splitPaneInMain: vi.fn<typeof splitPaneInMain>(),
-  splitServerPane: vi.fn<typeof splitServerPane>(),
-  splitWebRuntimeTerminal: vi.fn()
+const mocks = vi.hoisted(() => {
+  return {
+    layoutOwnerIsMain: false,
+    recordCreatedTerminalPaneSplit: vi.fn(),
+    resolveSplitCwd: vi.fn(),
+    splitPaneInMain: vi.fn<typeof splitPaneInMain>(),
+    splitServerPane: vi.fn<typeof splitServerPane>(),
+    splitWebRuntimeTerminal: vi.fn(),
+    readHostPublishedSplitSourcePtyId: vi.fn<() => string | null>(),
+    isHostTabPane: vi.fn<() => boolean>(),
+    notifyHostTabSplitRefused: vi.fn()
+  }
+})
+
+vi.mock('@/runtime/web-runtime-split-source-pty', () => ({
+  readHostPublishedSplitSourcePtyId: mocks.readHostPublishedSplitSourcePtyId,
+  isHostTabPane: mocks.isHostTabPane,
+  notifyHostTabSplitRefused: mocks.notifyHostTabSplitRefused
 }))
 
 vi.mock('../../../../shared/layout-owner-switch', () => ({
@@ -67,6 +78,64 @@ describe('splitTerminalPaneWithInheritedCwd', () => {
     mocks.resolveSplitCwd.mockReset()
     mocks.splitWebRuntimeTerminal.mockReset()
     mocks.splitWebRuntimeTerminal.mockReturnValue(false)
+    mocks.readHostPublishedSplitSourcePtyId.mockReset().mockReturnValue(null)
+    mocks.isHostTabPane.mockReset().mockReturnValue(false)
+    mocks.notifyHostTabSplitRefused.mockReset()
+  })
+
+  describe('a pane of a paired server tab whose own attach has not landed', () => {
+    const HOST_TAB = 'web-terminal-host-tab-1'
+    const HOST_PTY = 'remote:env-1@@terminal-1'
+    const SOURCE = { worktreeId: 'worktree-1', tabId: HOST_TAB, leafId: 'leaf-1' }
+
+    function splitHostTabPane(splitPane: ReturnType<typeof vi.fn>, serverTakesSplit = true): void {
+      mocks.isHostTabPane.mockReturnValue(true)
+      mocks.splitWebRuntimeTerminal.mockImplementation(
+        (ptyId: string | null) => serverTakesSplit && Boolean(ptyId)
+      )
+      splitTerminalPaneWithInheritedCwd({
+        worktreeId: 'worktree-1',
+        tabId: HOST_TAB,
+        manager: makeManager(splitPane),
+        // No transport yet: the pane's attach has not landed.
+        paneTransports: new Map(),
+        paneCwdMap: new Map(),
+        fallbackCwd: '/fallback',
+        pane: LAYOUT_OWNER_SOURCE_PANE,
+        direction: 'vertical',
+        source: 'keyboard'
+      })
+    }
+
+    it('splits on the server from the terminal the server published for it', () => {
+      mocks.readHostPublishedSplitSourcePtyId.mockReturnValue(HOST_PTY)
+      const splitPane = vi.fn()
+
+      splitHostTabPane(splitPane)
+
+      expect(mocks.splitWebRuntimeTerminal).toHaveBeenCalledWith(
+        HOST_PTY,
+        'vertical',
+        'keyboard',
+        SOURCE
+      )
+      expect(splitPane).not.toHaveBeenCalled()
+    })
+
+    // A pane split here has no server terminal, and nothing would ever start one.
+    it.each([
+      ['no terminal yet', null],
+      // e.g. the session to that server is not active.
+      ['a terminal the server cannot take a split for', HOST_PTY]
+    ])('refuses rather than splitting here with %s', (_case, published) => {
+      mocks.readHostPublishedSplitSourcePtyId.mockReturnValue(published)
+      const splitPane = vi.fn(() => ({ id: 2 }))
+
+      splitHostTabPane(splitPane, false)
+
+      expect(splitPane).not.toHaveBeenCalled()
+      expect(mocks.notifyHostTabSplitRefused).toHaveBeenCalledOnce()
+    })
   })
 
   it.each(['keyboard', 'context_menu'] as const)(
diff --git a/src/renderer/src/components/terminal-pane/terminal-pane-split-with-inherited-cwd.ts b/src/renderer/src/components/terminal-pane/terminal-pane-split-with-inherited-cwd.ts
index 381465436d8..d3d78fad9a7 100644
--- a/src/renderer/src/components/terminal-pane/terminal-pane-split-with-inherited-cwd.ts
+++ b/src/renderer/src/components/terminal-pane/terminal-pane-split-with-inherited-cwd.ts
@@ -1,6 +1,11 @@
 import type { TerminalPaneSplitSource } from '../../../../shared/feature-education-telemetry'
 import type { ManagedPane, PaneManager } from '@/lib/pane-manager/pane-manager'
 import { splitWebRuntimeTerminal } from '@/runtime/web-runtime-terminal-actions'
+import {
+  isHostTabPane,
+  notifyHostTabSplitRefused,
+  readHostPublishedSplitSourcePtyId
+} from '@/runtime/web-runtime-split-source-pty'
 import type { PtyTransport } from './pty-transport-types'
 import { resolveSplitCwd, type PaneCwdMap } from './resolve-split-cwd'
 import { recordCreatedTerminalPaneSplit } from './terminal-pane-split-completion'
@@ -26,14 +31,12 @@ type SplitArgs = {
 }
 
 export function splitTerminalPaneWithInheritedCwd(args: SplitArgs): void {
-  const ptyId = args.paneTransports.get(args.pane.id)?.getPtyId() ?? null
-  if (
-    splitWebRuntimeTerminal(ptyId, args.direction, args.source, {
-      worktreeId: args.worktreeId,
-      tabId: args.tabId,
-      leafId: args.pane.leafId
-    })
-  ) {
+  const sourcePane = { worktreeId: args.worktreeId, tabId: args.tabId, leafId: args.pane.leafId }
+  // Why the host's binding: a pane whose attach is still in flight has no transport id yet.
+  const ptyId =
+    args.paneTransports.get(args.pane.id)?.getPtyId() ??
+    readHostPublishedSplitSourcePtyId(sourcePane)
+  if (splitWebRuntimeTerminal(ptyId, args.direction, args.source, sourcePane)) {
     return
   }
   // Switch point: main writes the split and starts its terminal; main's frame draws the pane. A
@@ -54,6 +57,10 @@ export function splitTerminalPaneWithInheritedCwd(args: SplitArgs): void {
       return
     }
   }
+  if (isHostTabPane(sourcePane)) {
+    notifyHostTabSplitRefused(sourcePane)
+    return
+  }
   splitLocally(args, () => splitCwd(args, ptyId))
 }
 
diff --git a/src/renderer/src/i18n/locales/en.json b/src/renderer/src/i18n/locales/en.json
index a79e1bef9e3..66fc5676179 100644
--- a/src/renderer/src/i18n/locales/en.json
+++ b/src/renderer/src/i18n/locales/en.json
@@ -18792,6 +18792,7 @@
       },
       "webRuntimeSession": {
         "remoteHostDisconnected": "The workspace is not connected to a remote Orca host.",
+        "splitSourceUnpublished": "The pane didn’t split: its terminal hasn’t started on the host yet.",
         "terminalCreateUnconfirmed": "Orca couldn’t confirm that the new terminal opened on the host."
       },
       "gitlabJobTraceClient": {
diff --git a/src/renderer/src/i18n/locales/es.json b/src/renderer/src/i18n/locales/es.json
index 3afd4c23074..055f5bb9ec0 100644
--- a/src/renderer/src/i18n/locales/es.json
+++ b/src/renderer/src/i18n/locales/es.json
@@ -18511,6 +18511,7 @@
       },
       "webRuntimeSession": {
         "remoteHostDisconnected": "El espacio de trabajo no está conectado a un host Orca remoto.",
+        "splitSourceUnpublished": "El panel no se dividió: su terminal aún no se ha iniciado en el host.",
         "terminalCreateUnconfirmed": "Orca no pudo confirmar que la nueva terminal se abrió en el host."
       },
       "gitlabJobTraceClient": {
diff --git a/src/renderer/src/i18n/locales/fr.json b/src/renderer/src/i18n/locales/fr.json
index 9c78c89d314..ded65607d61 100644
--- a/src/renderer/src/i18n/locales/fr.json
+++ b/src/renderer/src/i18n/locales/fr.json
@@ -18651,6 +18651,7 @@
       },
       "webRuntimeSession": {
         "remoteHostDisconnected": "L'espace de travail n'est pas connecté à un hôte Orca distant.",
+        "splitSourceUnpublished": "Le volet n'a pas été divisé : son terminal n'a pas encore démarré sur l'hôte.",
         "terminalCreateUnconfirmed": "Orca n'a pas pu confirmer que le nouveau terminal s'est ouvert sur l'hôte."
       },
       "gitlabJobTraceClient": {
diff --git a/src/renderer/src/i18n/locales/ja.json b/src/renderer/src/i18n/locales/ja.json
index 4f35ee4a440..eecdc39af6d 100644
--- a/src/renderer/src/i18n/locales/ja.json
+++ b/src/renderer/src/i18n/locales/ja.json
@@ -18510,6 +18510,7 @@
       },
       "webRuntimeSession": {
         "remoteHostDisconnected": "このワークスペースは、リモートの Orca ホストに接続されていません。",
+        "splitSourceUnpublished": "ペインを分割できませんでした: ホスト上でターミナルがまだ起動していません。",
         "terminalCreateUnconfirmed": "Orca は、ホスト上で新規ターミナルが開いたことを確認できませんでした。"
       },
       "gitlabJobTraceClient": {
diff --git a/src/renderer/src/i18n/locales/ko.json b/src/renderer/src/i18n/locales/ko.json
index 33b04edc432..dc332e230d8 100644
--- a/src/renderer/src/i18n/locales/ko.json
+++ b/src/renderer/src/i18n/locales/ko.json
@@ -18510,6 +18510,7 @@
       },
       "webRuntimeSession": {
         "remoteHostDisconnected": "워크스페이스가 원격 Orca 호스트에 연결되어 있지 않습니다.",
+        "splitSourceUnpublished": "창을 분할하지 못했습니다: 호스트에서 터미널이 아직 시작되지 않았습니다.",
         "terminalCreateUnconfirmed": "Orca가 호스트에서 새 터미널이 열렸는지 확인할 수 없습니다."
       },
       "gitlabJobTraceClient": {
diff --git a/src/renderer/src/i18n/locales/pt.json b/src/renderer/src/i18n/locales/pt.json
index 2a20accbb9c..2f316a217f7 100644
--- a/src/renderer/src/i18n/locales/pt.json
+++ b/src/renderer/src/i18n/locales/pt.json
@@ -1038,6 +1038,7 @@
       },
       "webRuntimeSession": {
         "remoteHostDisconnected": "O espaço de trabalho não está conectado a um host Orca remoto.",
+        "splitSourceUnpublished": "O painel não foi dividido: o terminal ainda não foi iniciado no host.",
         "terminalCreateUnconfirmed": "O Orca não conseguiu confirmar que o novo terminal foi aberto no host."
       },
       "gitlabJobTraceClient": {
diff --git a/src/renderer/src/i18n/locales/zh.json b/src/renderer/src/i18n/locales/zh.json
index 3af40d5080e..60f4a3b54d1 100644
--- a/src/renderer/src/i18n/locales/zh.json
+++ b/src/renderer/src/i18n/locales/zh.json
@@ -18510,6 +18510,7 @@
       },
       "webRuntimeSession": {
         "remoteHostDisconnected": "工作区未连接到远程 Orca 主机。",
+        "splitSourceUnpublished": "窗格未拆分：其终端尚未在主机上启动。",
         "terminalCreateUnconfirmed": "Orca 无法确认新终端是否在主机上打开。"
       },
       "gitlabJobTraceClient": {
diff --git a/src/renderer/src/runtime/web-runtime-split-source-pty.test.ts b/src/renderer/src/runtime/web-runtime-split-source-pty.test.ts
new file mode 100644
index 00000000000..b8d15eb1612
--- /dev/null
+++ b/src/renderer/src/runtime/web-runtime-split-source-pty.test.ts
@@ -0,0 +1,61 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import {
+  notifyHostTabSplitRefused,
+  readHostPublishedSplitSourcePtyId
+} from './web-runtime-split-source-pty'
+
+const TAB = 'web-terminal-host-tab-1'
+const SOURCE = { worktreeId: 'worktree-1', tabId: TAB, leafId: 'leaf-1' }
+
+const mocks = vi.hoisted(() => {
+  const owner: { environmentId: string | null; transport: string } = {
+    environmentId: 'env-1',
+    transport: 'ready'
+  }
+  return { owner, toastError: vi.fn() }
+})
+
+vi.mock('../store', () => ({
+  useAppStore: {
+    getState: () => ({
+      terminalLayoutsByTabId: {
+        'web-terminal-host-tab-1': { ptyIdsByLeafId: { 'leaf-1': 'remote:env-1@@terminal-1' } }
+      },
+      runtimeStatusByEnvironmentId: new Map([
+        ['env-1', { snapshot: { transport: mocks.owner.transport } }]
+      ])
+    })
+  }
+}))
+vi.mock('../lib/resolve-owner', () => ({
+  runtimeEnvironmentIdUnlessTwin: () => mocks.owner.environmentId
+}))
+vi.mock('sonner', () => ({ toast: { error: mocks.toastError } }))
+vi.mock('@/i18n/i18n', () => ({ translate: (_key: string, fallback: string) => fallback }))
+
+describe('host-tab split source', () => {
+  beforeEach(() => {
+    mocks.owner.environmentId = 'env-1'
+    mocks.owner.transport = 'ready'
+    mocks.toastError.mockReset()
+  })
+
+  it('reads the terminal the workspace’s server published for the pane', () => {
+    expect(readHostPublishedSplitSourcePtyId(SOURCE)).toBe('remote:env-1@@terminal-1')
+  })
+
+  // A split sent from it would run on a server the workspace no longer belongs to.
+  it('ignores a binding naming another server', () => {
+    mocks.owner.environmentId = 'env-2'
+    expect(readHostPublishedSplitSourcePtyId(SOURCE)).toBeNull()
+  })
+
+  it.each([
+    ['still starting', 'ready', 'its terminal hasn’t started'],
+    ['disconnected', 'disconnected', 'not connected to a remote Orca host']
+  ])('tells the user why the split was refused while the server is %s', (_c, transport, text) => {
+    mocks.owner.transport = transport
+    notifyHostTabSplitRefused(SOURCE)
+    expect(mocks.toastError).toHaveBeenCalledWith(expect.stringContaining(text), expect.anything())
+  })
+})
diff --git a/src/renderer/src/runtime/web-runtime-split-source-pty.ts b/src/renderer/src/runtime/web-runtime-split-source-pty.ts
new file mode 100644
index 00000000000..afcc4a70a3d
--- /dev/null
+++ b/src/renderer/src/runtime/web-runtime-split-source-pty.ts
@@ -0,0 +1,56 @@
+import { toast } from 'sonner'
+import { translate } from '@/i18n/i18n'
+import { isWebTerminalSurfaceTabId } from '../../../shared/terminal-surface-id'
+import { parseRemoteRuntimePtyId } from '../../../shared/remote-runtime-pty-id'
+import { runtimeEnvironmentIdUnlessTwin } from '../lib/resolve-owner'
+import { useAppStore } from '../store'
+import type { WebRuntimeSplitSource } from './web-runtime-split-focus'
+
+/**
+ * The terminal the workspace's server published for a pane of one of its tabs, before this pane's
+ * own attach lands. A binding naming any other server is not this pane's terminal.
+ */
+export function readHostPublishedSplitSourcePtyId(source: WebRuntimeSplitSource): string | null {
+  if (!isWebTerminalSurfaceTabId(source.tabId)) {
+    return null
+  }
+  const state = useAppStore.getState()
+  const ptyId = state.terminalLayoutsByTabId[source.tabId]?.ptyIdsByLeafId?.[source.leafId]
+  const environmentId = runtimeEnvironmentIdUnlessTwin(state, source.worktreeId)
+  return ptyId && environmentId && parseRemoteRuntimePtyId(ptyId)?.environmentId === environmentId
+    ? ptyId
+    : null
+}
+
+/** A pane of a paired server's tab: only that server starts terminals in it. */
+export function isHostTabPane(source: WebRuntimeSplitSource): boolean {
+  return (
+    isWebTerminalSurfaceTabId(source.tabId) &&
+    runtimeEnvironmentIdUnlessTwin(useAppStore.getState(), source.worktreeId) !== null
+  )
+}
+
+/**
+ * Why a server-tab pane did not split. Only the server starts terminals in its tabs, so splitting
+ * here instead would leave a blank pane.
+ */
+export function notifyHostTabSplitRefused(source: WebRuntimeSplitSource): void {
+  const state = useAppStore.getState()
+  const environmentId = runtimeEnvironmentIdUnlessTwin(state, source.worktreeId)
+  const disconnected =
+    !environmentId ||
+    state.runtimeStatusByEnvironmentId.get(environmentId)?.snapshot?.transport === 'disconnected'
+  toast.error(
+    disconnected
+      ? translate(
+          'auto.runtime.webRuntimeSession.remoteHostDisconnected',
+          'The workspace is not connected to a remote Orca host.'
+        )
+      : translate(
+          'auto.runtime.webRuntimeSession.splitSourceUnpublished',
+          'The pane didn’t split: its terminal hasn’t started on the host yet.'
+        ),
+    // Why an id: repeated presses must not stack toasts.
+    { id: 'web-runtime-host-tab-split-refused' }
+  )
+}
diff --git a/tests/e2e/paired-seeded-terminal-immediate-split.spec.ts b/tests/e2e/paired-seeded-terminal-immediate-split.spec.ts
new file mode 100644
index 00000000000..7366192ac92
--- /dev/null
+++ b/tests/e2e/paired-seeded-terminal-immediate-split.spec.ts
@@ -0,0 +1,67 @@
+import type { RuntimeTerminalListResult } from '../../src/shared/runtime-types'
+import { expect, test } from './helpers/orca-app'
+import { launchHeadlessPairedRuntimeHost } from './helpers/headless-paired-runtime-host'
+import { launchPairedElectronClient } from './helpers/paired-electron-client'
+import { waitForBoundPanes } from './helpers/terminal-layout-journeys'
+import { splitActiveTerminalPane } from './helpers/terminal'
+
+const PANE = '.pane[data-leaf-id]:visible'
+
+// A split issued while the desktop's seeded first tab is still settling must still give the new
+// pane a live server terminal, not a blank pane.
+test('a split right after the first terminal of an empty paired-server workspace binds both panes', async ({
+  testRepoPath
+}, testInfo) => {
+  test.setTimeout(180_000)
+  const host = await launchHeadlessPairedRuntimeHost()
+  try {
+    await host.client.call('repo.add', { path: testRepoPath, kind: 'git' })
+    const desktop = await launchPairedElectronClient(host.offer, testInfo, 'seeded split')
+    try {
+      const page = desktop.page
+      let worktreeId = ''
+      await expect
+        .poll(
+          async () =>
+            (worktreeId = await page.evaluate(
+              (repo) =>
+                window.__store
+                  ?.getState()
+                  .allWorktrees()
+                  .find((worktree) => worktree.path === repo)?.id ?? '',
+              testRepoPath
+            )),
+          { timeout: 60_000 }
+        )
+        .not.toBe('')
+      await page.evaluate((id) => window.__store?.getState().setActiveWorktree(id), worktreeId)
+      // Split the moment the seeded pane mounts, before its terminal has attached.
+      await expect(page.locator(PANE)).toHaveCount(1, { timeout: 60_000 })
+      await splitActiveTerminalPane(page, 'vertical')
+      await waitForBoundPanes(page, 2)
+
+      const leafIds = await page
+        .locator(PANE)
+        .evaluateAll((panes) => panes.map((pane) => pane.getAttribute('data-leaf-id') ?? ''))
+      await expect
+        .poll(
+          async () => {
+            const { terminals } = (
+              await host.client.call<RuntimeTerminalListResult>('terminal.list', {
+                worktree: `id:${worktreeId}`
+              })
+            ).result
+            return leafIds.every((leafId) =>
+              terminals.some((terminal) => terminal.leafId === leafId)
+            )
+          },
+          { timeout: 30_000, message: 'a split pane has no server terminal' }
+        )
+        .toBe(true)
+    } finally {
+      await desktop.dispose()
+    }
+  } finally {
+    await host.dispose()
+  }
+})