diff --git a/src/main/ai-vault/runtime-session-scanner.test.ts b/src/main/ai-vault/runtime-session-scanner.test.ts
index a891a8000a9..db718a4380d 100644
--- a/src/main/ai-vault/runtime-session-scanner.test.ts
+++ b/src/main/ai-vault/runtime-session-scanner.test.ts
@@ -200,6 +200,35 @@ describe('runtime AI Vault session scanner', () => {
       })
     ).rejects.toThrow('Invalid aiVault.prepareSessionResume response')
   })
+
+  it('emits the desktop sentinel only for this exact missing RPC', async () => {
+    mocks.callRuntimeEnvironment.mockResolvedValueOnce({
+      ok: false,
+      error: { code: 'method_not_found', message: 'Unknown method: aiVault.prepareSessionResume' }
+    })
+
+    await expect(
+      prepareRuntimeAiVaultSessionResume('/user-data', 'env-1', {
+        agent: 'claude',
+        filePath: '/sessions/a.jsonl',
+        codexHome: null,
+        executionHostId: 'runtime:env-1'
+      })
+    ).rejects.toThrow('aiVault.prepareSessionResume: method_not_found')
+
+    mocks.callRuntimeEnvironment.mockResolvedValueOnce({
+      ok: false,
+      error: { code: 'method_not_found', message: 'Unknown method: terminal.send' }
+    })
+    await expect(
+      prepareRuntimeAiVaultSessionResume('/user-data', 'env-1', {
+        agent: 'claude',
+        filePath: '/sessions/a.jsonl',
+        codexHome: null,
+        executionHostId: 'runtime:env-1'
+      })
+    ).rejects.toThrow('Unknown method: terminal.send')
+  })
 })
 
 function result(
diff --git a/src/main/ai-vault/runtime-session-scanner.ts b/src/main/ai-vault/runtime-session-scanner.ts
index 794a2177c00..e81e29e9160 100644
--- a/src/main/ai-vault/runtime-session-scanner.ts
+++ b/src/main/ai-vault/runtime-session-scanner.ts
@@ -149,6 +149,13 @@ export async function prepareRuntimeAiVaultSessionResume(
     args
   )
   if (response.ok !== true) {
+    if (
+      response.error.code === 'method_not_found' &&
+      response.error.message === 'Unknown method: aiVault.prepareSessionResume'
+    ) {
+      // Why: Electron drops custom error fields; this exact message preserves the host's verdict.
+      throw new Error('aiVault.prepareSessionResume: method_not_found')
+    }
     throw new Error(response.error.message)
   }
   const parsed = aiVaultPrepareSessionResumeResultSchema.safeParse(response.result)
diff --git a/src/main/ipc/ai-vault-resume.test.ts b/src/main/ipc/ai-vault-resume.test.ts
new file mode 100644
index 00000000000..89187a0593b
--- /dev/null
+++ b/src/main/ipc/ai-vault-resume.test.ts
@@ -0,0 +1,44 @@
+import { afterEach, expect, it, vi } from 'vitest'
+import { setStructuredAgentSessionHost } from '../native-chat/agent-session-wire/structured-agent-session-registry'
+import {
+  installOwnership,
+  PROVIDER_SESSION
+} from '../ai-vault/structured-session-ownership.test-support'
+import { prepareAiVaultSessionResume } from './ai-vault-resume'
+
+vi.mock('electron', () => ({ ipcMain: { handle: vi.fn() } }))
+afterEach(() => setStructuredAgentSessionHost(null))
+
+it('refuses the native owner while preserving forks and other execution hosts', async () => {
+  installOwnership({ handle: { transport: 'acp', agent: 'omp', nativeId: PROVIDER_SESSION } })
+  const local = {
+    agent: 'omp' as const,
+    sessionId: PROVIDER_SESSION,
+    filePath: '/sessions/conversation.jsonl',
+    codexHome: null,
+    executionHostId: 'local' as const
+  }
+  const prepareSessionResume = vi.fn().mockResolvedValue({ useRealCodexHome: false })
+  const prepareRuntimeSessionResume = vi.fn().mockResolvedValue({ useRealCodexHome: false })
+  const options = { prepareSessionResume, prepareRuntimeSessionResume }
+  await expect(prepareAiVaultSessionResume(local, options)).rejects.toThrow(
+    'agent_session_conflict'
+  )
+  expect(prepareSessionResume).not.toHaveBeenCalled()
+  await expect(prepareAiVaultSessionResume({ ...local, fork: true }, options)).resolves.toEqual({
+    useRealCodexHome: false
+  })
+  const paired = { ...local, executionHostId: 'runtime:paired' as const }
+  await expect(prepareAiVaultSessionResume(paired, options)).resolves.toEqual({
+    useRealCodexHome: false
+  })
+  expect(prepareRuntimeSessionResume).toHaveBeenCalledWith('paired', paired)
+  await expect(
+    prepareAiVaultSessionResume({ ...local, executionHostId: 'ssh:server' }, options)
+  ).resolves.toEqual({ useRealCodexHome: false })
+  const wsl = { ...local, filePath: String.raw`\\wsl.localhost\Ubuntu\home\qa\session.jsonl` }
+  await expect(prepareAiVaultSessionResume(wsl, options)).resolves.toEqual({
+    useRealCodexHome: false
+  })
+  expect(prepareSessionResume).toHaveBeenCalledWith(wsl)
+})
diff --git a/src/main/ipc/ai-vault-resume.ts b/src/main/ipc/ai-vault-resume.ts
index 37055ab182b..25469b1d244 100644
--- a/src/main/ipc/ai-vault-resume.ts
+++ b/src/main/ipc/ai-vault-resume.ts
@@ -5,7 +5,9 @@ import type {
   AiVaultSessionResumePreparation
 } from '../../shared/ai-vault-resume-preparation'
 import { isUnresolvedOwnerHostId, parseExecutionHostId } from '../../shared/execution-host'
+import { isWslUncPath } from '../../shared/wsl-paths'
 import { assertLegacyAiVaultResumeAllowed } from '../ai-vault/structured-session-ownership'
+import { tryEnsureStructuredAgentSessionHostForResume } from '../runtime/structured-agent-session-host-refusal'
 
 export type AiVaultResumeHandlerOptions = {
   ensureStructuredSessionOwnership?: () => Promise<void>
@@ -26,8 +28,6 @@ export async function prepareAiVaultSessionResume(
   args: AiVaultPrepareSessionResumeArgs,
   options: AiVaultResumeHandlerOptions
 ): Promise<AiVaultPrepareSessionResumeResult> {
-  await options.ensureStructuredSessionOwnership?.()
-  assertLegacyAiVaultResumeAllowed(args)
   const executionHost = parseExecutionHostId(args.executionHostId)
   if (executionHost?.kind === 'runtime') {
     if (!options.prepareRuntimeSessionResume || isUnresolvedOwnerHostId(executionHost.id)) {
@@ -39,5 +39,13 @@ export async function prepareAiVaultSessionResume(
   if (executionHost?.kind === 'ssh') {
     return { useRealCodexHome: false }
   }
+  if (!isWslUncPath(args.filePath)) {
+    if (options.ensureStructuredSessionOwnership) {
+      await (args.codexHome === null && !args.fork
+        ? tryEnsureStructuredAgentSessionHostForResume(options.ensureStructuredSessionOwnership)
+        : options.ensureStructuredSessionOwnership())
+    }
+    assertLegacyAiVaultResumeAllowed(args)
+  }
   return options.prepareSessionResume?.(args) ?? { useRealCodexHome: false }
 }
diff --git a/src/main/runtime/rpc/methods/ai-vault.ts b/src/main/runtime/rpc/methods/ai-vault.ts
index cda50f28f67..a5e6d6a5890 100644
--- a/src/main/runtime/rpc/methods/ai-vault.ts
+++ b/src/main/runtime/rpc/methods/ai-vault.ts
@@ -12,13 +12,17 @@ import { conditionalAiVaultListResult } from '../../../ai-vault/session-list-fin
 import { restampAiVaultListResult } from '../../../ai-vault/session-list-results'
 import type { AiVaultPrepareSessionResumeArgs } from '../../../../shared/ai-vault-resume-preparation'
 import { LOCAL_EXECUTION_HOST_ID } from '../../../../shared/execution-host'
+import { isWslUncPath } from '../../../../shared/wsl-paths'
 import { describeAiVaultScanError } from '../../../../shared/ai-vault-scan-error-message'
 import {
   assertLegacyAiVaultResumeAllowed,
   projectStructuredAiVaultSessions,
   searchWithStructuredOwners
 } from '../../../ai-vault/structured-session-ownership'
-import { ensureStructuredAgentSessionHostUnlessRefused } from '../../structured-agent-session-host-refusal'
+import {
+  ensureStructuredAgentSessionHostUnlessRefused,
+  tryEnsureStructuredAgentSessionHostForResume
+} from '../../structured-agent-session-host-refusal'
 import {
   clientOpensStructuredChatFromHistory,
   supportsStructuredAgentSessions
@@ -133,10 +137,13 @@ export const AI_VAULT_METHODS = [
         // client-provided runtime/SSH stamp escape that host boundary.
         executionHostId: LOCAL_EXECUTION_HOST_ID
       }
-      await ensureStructuredAgentSessionHostUnlessRefused(() =>
-        runtime.ensureStructuredAgentSessionHost()
-      )
-      assertLegacyAiVaultResumeAllowed(args)
+      if (!isWslUncPath(args.filePath)) {
+        const ensureHost = () => runtime.ensureStructuredAgentSessionHost()
+        await (args.codexHome === null && !args.fork
+          ? tryEnsureStructuredAgentSessionHostForResume(ensureHost)
+          : ensureStructuredAgentSessionHostUnlessRefused(ensureHost))
+        assertLegacyAiVaultResumeAllowed(args)
+      }
       return runtime.prepareAiVaultSessionResume(args)
     }
   })
diff --git a/src/main/runtime/structured-agent-session-host-refusal.ts b/src/main/runtime/structured-agent-session-host-refusal.ts
index 30465c0fb12..765e05093f4 100644
--- a/src/main/runtime/structured-agent-session-host-refusal.ts
+++ b/src/main/runtime/structured-agent-session-host-refusal.ts
@@ -38,6 +38,25 @@ export async function ensureStructuredAgentSessionHostUnlessRefused(
   }
 }
 
+/** Chat-host setup is bookkeeping for a terminal resume; an existing owner is checked afterward. */
+export async function tryEnsureStructuredAgentSessionHostForResume(
+  ensureHost: () => Promise<unknown>
+): Promise<void> {
+  try {
+    await ensureStructuredAgentSessionHostUnlessRefused(ensureHost)
+  } catch (error) {
+    const code = isAgentSessionRefusalError(error)
+      ? error.refusal.code
+      : error instanceof Error
+        ? error.message
+        : null
+    if (code === 'agent_session_conflict' || code === 'agent_session_ownership_unknown') {
+      throw error
+    }
+    console.warn('[ai-vault] native chat host setup failed during terminal resume:', error)
+  }
+}
+
 /** Set when the journal database would not open; cleared by a later install. The install retries
  *  on the next call, so a refusal that can clear does. */
 export function recordStructuredAgentSessionHostInstallRefusal(
diff --git a/src/renderer/src/components/right-sidebar/ai-vault-session-cli-fork.ts b/src/renderer/src/components/right-sidebar/ai-vault-session-cli-fork.ts
index 6e9c9f95434..f5c86c938fa 100644
--- a/src/renderer/src/components/right-sidebar/ai-vault-session-cli-fork.ts
+++ b/src/renderer/src/components/right-sidebar/ai-vault-session-cli-fork.ts
@@ -1,5 +1,5 @@
 import { translate } from '@/i18n/i18n'
-import { compactIpcErrorMessage } from '@/lib/ipc-error'
+import { isAiVaultOwnershipRefusal } from '@/lib/ai-vault-resume-refusal'
 import type { AiVaultSession } from '../../../../shared/ai-vault-types'
 import { getAgentForkArgv, isResumableTuiAgent } from '../../../../shared/agent-session-resume'
 import { getAiVaultAgentProviderSession } from '@/lib/ai-vault-resume-command'
@@ -29,8 +29,7 @@ export function aiVaultSessionCliForkWorktreeId(
  *  the fork as a second writer, so that refusal asks for the update instead of naming a code. */
 export function describeAiVaultCliForkFailure(message: string): string {
   // The desktop preparation's refusal arrives inside Electron's IPC wrapper.
-  const code = compactIpcErrorMessage(message)
-  return code === 'agent_session_conflict' || code === 'agent_session_ownership_unknown'
+  return isAiVaultOwnershipRefusal(message)
     ? translate(
         'auto.components.right.sidebar.AiVaultPanel.resumeInNewCliHostTooOld',
         'Update Orca on the host that runs this chat to resume it in a new CLI.'
diff --git a/src/renderer/src/components/right-sidebar/ai-vault-session-launch-actions.test.ts b/src/renderer/src/components/right-sidebar/ai-vault-session-launch-actions.test.ts
index 175a5d0b9e1..a17cfb36890 100644
--- a/src/renderer/src/components/right-sidebar/ai-vault-session-launch-actions.test.ts
+++ b/src/renderer/src/components/right-sidebar/ai-vault-session-launch-actions.test.ts
@@ -9,6 +9,7 @@ const mocks = vi.hoisted(() => ({
   buildAiVaultResumeStartupForWorktree: vi.fn(),
   prepareAiVaultSessionForFork: vi.fn(),
   prepareAiVaultSessionForResume: vi.fn(),
+  prepareAiVaultSessionForTerminalResume: vi.fn(),
   launchAiVaultSessionInNewTab: vi.fn(),
   activateAiVaultResumeWorkspace: vi.fn(),
   toastError: vi.fn(),
@@ -25,6 +26,7 @@ vi.mock('@/lib/ai-vault-resume-command', () => ({
 vi.mock('@/lib/ai-vault-session-resume-preparation', () => ({
   prepareAiVaultSessionForFork: mocks.prepareAiVaultSessionForFork,
   prepareAiVaultSessionForResume: mocks.prepareAiVaultSessionForResume,
+  prepareAiVaultSessionForTerminalResume: mocks.prepareAiVaultSessionForTerminalResume,
   dropDeletedSshResumeCwd: async (session: unknown) => session
 }))
 vi.mock('@/lib/launch-ai-vault-session', () => ({
@@ -154,3 +156,21 @@ describe('Resume in New CLI launch', () => {
     expect(mocks.launchAiVaultSessionInNewTab).not.toHaveBeenCalled()
   })
 })
+
+it('refuses the stale OMP row before creating a second terminal writer', async () => {
+  vi.clearAllMocks()
+  mocks.prepareAiVaultSessionForTerminalResume.mockRejectedValue(
+    new Error(
+      "Error invoking remote method 'aiVault:prepareSessionResume': Error: agent_session_conflict"
+    )
+  )
+  renderActions().handleResume(
+    { ...owned, agent: 'omp', structuredSession: undefined },
+    'worktree-1'
+  )
+  await waitFor(() => expect(mocks.toastError).toHaveBeenCalledOnce())
+  expect(mocks.toastError).toHaveBeenCalledWith(
+    'This OMP conversation is open in a chat. Refresh Session History to open it.'
+  )
+  expect(mocks.launchAiVaultSessionInNewTab).not.toHaveBeenCalled()
+})
diff --git a/src/renderer/src/components/right-sidebar/ai-vault-session-launch-actions.ts b/src/renderer/src/components/right-sidebar/ai-vault-session-launch-actions.ts
index 135a8d2ce21..08421b670b8 100644
--- a/src/renderer/src/components/right-sidebar/ai-vault-session-launch-actions.ts
+++ b/src/renderer/src/components/right-sidebar/ai-vault-session-launch-actions.ts
@@ -13,7 +13,8 @@ import type { AiVaultAgent, AiVaultSession } from '../../../../shared/ai-vault-t
 import {
   dropDeletedSshResumeCwd,
   prepareAiVaultSessionForFork,
-  prepareAiVaultSessionForResume
+  prepareAiVaultSessionForResume,
+  prepareAiVaultSessionForTerminalResume
 } from '@/lib/ai-vault-session-resume-preparation'
 import type { Worktree } from '../../../../shared/worktree/types'
 import { translate } from '@/i18n/i18n'
@@ -25,6 +26,7 @@ import type { AgentSessionContinuationRequest } from '@/lib/agent-session-contin
 import { activateAiVaultStructuredSession } from '@/lib/activate-ai-vault-structured-session'
 import { adoptsCliConversations } from '../../../../shared/structured-agent-cli-conversation-adoption'
 import { newAgentLaunchRequestId } from '@/lib/agent-launch-request-id'
+import { describeAiVaultResumeFailure } from '@/lib/ai-vault-resume-refusal'
 import {
   activateAiVaultResumeWorkspace,
   resumeAiVaultSessionInNewChat
@@ -86,7 +88,7 @@ export function useAiVaultSessionLaunchActions({
           )
         )
       } catch (error) {
-        notifyAiVaultSessionPreparationFailure(error)
+        notifyAiVaultSessionPreparationFailure(error, session.agent)
       }
     },
     [buildResumeCommand]
@@ -150,7 +152,9 @@ export function useAiVaultSessionLaunchActions({
           }
           showQueuedToast()
         })
-        .catch((error: unknown) => notifyAiVaultSessionPreparationFailure(error, describeFailure))
+        .catch((error: unknown) =>
+          notifyAiVaultSessionPreparationFailure(error, session.agent, describeFailure)
+        )
     },
     [activeWorktree?.id, activeWorktreeId, targetState]
   )
@@ -161,10 +165,14 @@ export function useAiVaultSessionLaunchActions({
         void activateAiVaultStructuredSession(session)
         return
       }
-      launchInTerminal(session, targetWorktreeId, (worktreeId) =>
-        prepareAiVaultSessionForResume(session)
-          .then(dropDeletedSshResumeCwd)
-          .then((preparedSession) => buildResumeStartup(preparedSession, worktreeId))
+      launchInTerminal(
+        session,
+        targetWorktreeId,
+        (worktreeId) =>
+          prepareAiVaultSessionForTerminalResume(session)
+            .then(dropDeletedSshResumeCwd)
+            .then((preparedSession) => buildResumeStartup(preparedSession, worktreeId)),
+        (message) => describeAiVaultResumeFailure(new Error(message), session.agent)
       )
     },
     [buildResumeStartup, launchInTerminal]
@@ -277,16 +285,11 @@ export function useAiVaultSessionLaunchActions({
 
 function notifyAiVaultSessionPreparationFailure(
   error: unknown,
+  agent: AiVaultAgent,
   describeFailure: (message: string) => string = (message) => message
 ): void {
-  toast.error(
-    error instanceof Error
-      ? describeFailure(error.message)
-      : translate(
-          'auto.components.right.sidebar.AiVaultPanel.prepareSessionResumeFailed',
-          'Could not prepare this session for resume.'
-        )
-  )
+  const described = error instanceof Error ? new Error(describeFailure(error.message)) : error
+  toast.error(describeAiVaultResumeFailure(described, agent))
 }
 
 function resolveAiVaultSessionLaunchTargetOrNotify(
diff --git a/src/renderer/src/components/tab-group/AiVaultSessionDropLayer.tsx b/src/renderer/src/components/tab-group/AiVaultSessionDropLayer.tsx
index eb954cbe077..e785bb9de1a 100644
--- a/src/renderer/src/components/tab-group/AiVaultSessionDropLayer.tsx
+++ b/src/renderer/src/components/tab-group/AiVaultSessionDropLayer.tsx
@@ -18,12 +18,12 @@ import {
   getAiVaultAgentProviderSession
 } from '@/lib/ai-vault-resume-command'
 import { launchAiVaultSessionInNewTab } from '@/lib/launch-ai-vault-session'
-import { aiVaultSessionNeedsResumePreparation } from '@/lib/ai-vault-session-resume-preparation'
+import { prepareAiVaultTerminalResumeRequest } from '@/lib/ai-vault-session-resume-preparation'
+import { describeAiVaultResumeFailure } from '@/lib/ai-vault-resume-refusal'
 import { useAppStore } from '@/store'
 import { resolveDropZone } from './tab-drop-zone'
 import type { TabDropZone } from './useTabDragSplit'
 import { translate } from '@/i18n/i18n'
-import type { AiVaultPrepareSessionResumeResult } from '../../../../shared/ai-vault-resume-preparation'
 import { activateAiVaultStructuredSession } from '@/lib/activate-ai-vault-structured-session'
 
 type PaneDropTarget = {
@@ -222,23 +222,22 @@ export default function AiVaultSessionDropLayer({
           )
         )
       }
-      const preparation =
-        payload.sessionFilePath &&
-        payload.sessionExecutionHostId &&
-        payload.codexHome !== undefined &&
-        aiVaultSessionNeedsResumePreparation({
-          agent: payload.agent,
-          codexHome: payload.codexHome,
-          executionHostId: payload.sessionExecutionHostId
-        })
-          ? window.api.aiVault.prepareSessionResume({
-              agent: payload.agent,
-              sessionId: payload.sessionId,
-              filePath: payload.sessionFilePath,
-              executionHostId: payload.sessionExecutionHostId,
-              codexHome: payload.codexHome
-            })
-          : Promise.resolve<AiVaultPrepareSessionResumeResult>({ useRealCodexHome: false })
+      if (!payload.sessionFilePath || !payload.sessionExecutionHostId) {
+        toast.error(
+          translate(
+            'auto.components.tab.group.AiVaultSessionDropLayer.oldPayload',
+            'This session was dragged from an older Orca window. Resume it from Session History instead.'
+          )
+        )
+        return true
+      }
+      const preparation = prepareAiVaultTerminalResumeRequest({
+        agent: payload.agent,
+        sessionId: payload.sessionId,
+        filePath: payload.sessionFilePath,
+        executionHostId: payload.sessionExecutionHostId,
+        codexHome: payload.codexHome ?? null
+      })
       void preparation
         .then((result) => {
           const startup = result.useRealCodexHome
@@ -282,7 +281,9 @@ export default function AiVaultSessionDropLayer({
             void launchResult.runtimeLaunch.then((outcome) => {
               if (outcome.status === 'failed') {
                 toast.error(
-                  outcome.message ||
+                  (outcome.message
+                    ? describeAiVaultResumeFailure(new Error(outcome.message), payload.agent)
+                    : null) ||
                     translate(
                       'auto.lib.launch.agent.in.new.tab.11cce5cc77',
                       'Could not launch {{value0}} in a new terminal.',
@@ -298,14 +299,7 @@ export default function AiVaultSessionDropLayer({
           showQueuedToast()
         })
         .catch((error: unknown) => {
-          toast.error(
-            error instanceof Error
-              ? error.message
-              : translate(
-                  'auto.components.right.sidebar.AiVaultPanel.prepareSessionResumeFailed',
-                  'Could not prepare this session for resume.'
-                )
-          )
+          toast.error(describeAiVaultResumeFailure(error, payload.agent))
         })
       return true
     },
diff --git a/src/renderer/src/i18n/locales/en.json b/src/renderer/src/i18n/locales/en.json
index d3b0d9ad556..db715cb3ff8 100644
--- a/src/renderer/src/i18n/locales/en.json
+++ b/src/renderer/src/i18n/locales/en.json
@@ -1220,6 +1220,10 @@
             }
           }
         }
+      },
+      "aiVaultResumeRefusal": {
+        "openInChat": "This {{value0}} conversation is open in a chat. Refresh Session History to open it.",
+        "ownershipUnknown": "Orca could not confirm who owns this {{value0}} conversation. Refresh Session History and try again."
       }
     },
     "hooks": {
@@ -3660,7 +3664,8 @@
             "sessionQueued": "Session queued",
             "openSupportedWorkspace": "Open a workspace before resuming a session.",
             "sessionHostMismatchUnsupported": "This session belongs to a different host. Drop it onto a workspace on the same host.",
-            "localSessionSshWorkspaceUnsupported": "This session's history is stored on this machine, so it can't resume in an SSH workspace. Drop it onto a local workspace instead."
+            "localSessionSshWorkspaceUnsupported": "This session's history is stored on this machine, so it can't resume in an SSH workspace. Drop it onto a local workspace instead.",
+            "oldPayload": "This session was dragged from an older Orca window. Resume it from Session History instead."
           },
           "TabGroupDropOverlay": {
             "paneColumnLabel": "New split"
diff --git a/src/renderer/src/lib/ai-vault-resume-refusal.ts b/src/renderer/src/lib/ai-vault-resume-refusal.ts
new file mode 100644
index 00000000000..23e3902e593
--- /dev/null
+++ b/src/renderer/src/lib/ai-vault-resume-refusal.ts
@@ -0,0 +1,34 @@
+import { aiVaultAgentLabel, type AiVaultAgent } from '../../../shared/ai-vault-types'
+import { translate } from '@/i18n/i18n'
+import { compactIpcErrorMessage } from './ipc-error'
+
+export function isAiVaultOwnershipRefusal(message: string): boolean {
+  const code = compactIpcErrorMessage(message)
+  return code === 'agent_session_conflict' || code === 'agent_session_ownership_unknown'
+}
+
+export function describeAiVaultResumeFailure(error: unknown, agent: AiVaultAgent): string {
+  const message = error instanceof Error ? error.message : null
+  const code = message ? compactIpcErrorMessage(message) : null
+  if (code === 'agent_session_conflict') {
+    return translate(
+      'auto.lib.aiVaultResumeRefusal.openInChat',
+      'This {{value0}} conversation is open in a chat. Refresh Session History to open it.',
+      { value0: aiVaultAgentLabel(agent) }
+    )
+  }
+  if (code === 'agent_session_ownership_unknown') {
+    return translate(
+      'auto.lib.aiVaultResumeRefusal.ownershipUnknown',
+      'Orca could not confirm who owns this {{value0}} conversation. Refresh Session History and try again.',
+      { value0: aiVaultAgentLabel(agent) }
+    )
+  }
+  return (
+    message ??
+    translate(
+      'auto.components.right.sidebar.AiVaultPanel.prepareSessionResumeFailed',
+      'Could not prepare this session for resume.'
+    )
+  )
+}
diff --git a/src/renderer/src/lib/ai-vault-session-resume-preparation.test.ts b/src/renderer/src/lib/ai-vault-session-resume-preparation.test.ts
index ebabe7c2244..b29f32fba47 100644
--- a/src/renderer/src/lib/ai-vault-session-resume-preparation.test.ts
+++ b/src/renderer/src/lib/ai-vault-session-resume-preparation.test.ts
@@ -3,7 +3,8 @@ import type { AiVaultSession } from '../../../shared/ai-vault-types'
 import {
   dropDeletedSshResumeCwd,
   prepareAiVaultSessionForFork,
-  prepareAiVaultSessionForResume
+  prepareAiVaultSessionForResume,
+  prepareAiVaultSessionForTerminalResume
 } from './ai-vault-session-resume-preparation'
 
 afterEach(() => {
@@ -99,6 +100,29 @@ describe('prepareAiVaultSessionForResume', () => {
   })
 })
 
+describe('ordinary Resume against an older paired host', () => {
+  it.each([
+    new Error(
+      "Error invoking remote method 'aiVault:prepareSessionResume': Error: aiVault.prepareSessionResume: method_not_found"
+    ),
+    Object.assign(new Error('Unknown method: aiVault.prepareSessionResume'), {
+      code: 'method_not_found'
+    })
+  ])('retains neutral resumes but requires managed Codex home preparation', async (error) => {
+    stubPreparation(vi.fn().mockRejectedValue(error))
+    const remote = session({ agent: 'claude', executionHostId: 'runtime:paired' })
+    await expect(prepareAiVaultSessionForTerminalResume(remote)).resolves.toBe(remote)
+    await expect(
+      prepareAiVaultSessionForTerminalResume(
+        session({
+          executionHostId: 'runtime:paired',
+          codexHome: '/tmp/orca/codex-runtime-home/home'
+        })
+      )
+    ).rejects.toBe(error)
+  })
+})
+
 describe('prepareAiVaultSessionForFork', () => {
   // A fork of a chat-owned conversation must run under the selected account, as a resume does.
   it('repins a chat-owned per-account session, asking the host as a fork', async () => {
diff --git a/src/renderer/src/lib/ai-vault-session-resume-preparation.ts b/src/renderer/src/lib/ai-vault-session-resume-preparation.ts
index 8740d7a7796..04bef7974be 100644
--- a/src/renderer/src/lib/ai-vault-session-resume-preparation.ts
+++ b/src/renderer/src/lib/ai-vault-session-resume-preparation.ts
@@ -1,20 +1,83 @@
 import type { AiVaultSession } from '../../../shared/ai-vault-types'
+import type {
+  AiVaultPrepareSessionResumeArgs,
+  AiVaultPrepareSessionResumeResult
+} from '../../../shared/ai-vault-resume-preparation'
 import {
   isLegacySharedCodexHome,
   isPerAccountManagedCodexHome
 } from '../../../shared/ai-vault-resume-preparation'
 import {
   getSshTargetIdForExecutionHost,
-  LOCAL_EXECUTION_HOST_ID
+  LOCAL_EXECUTION_HOST_ID,
+  parseExecutionHostId
 } from '../../../shared/execution-host'
+import { readIpcErrorMessage } from './ipc-error'
 import type { AiVaultResumeCommandSession } from './ai-vault-resume-command'
 
 export function prepareAiVaultSessionForResume(session: AiVaultSession): Promise<AiVaultSession> {
-  return session.structuredSession
+  return session.structuredSession || !aiVaultSessionNeedsResumePreparation(session)
     ? Promise.resolve(session)
     : prepareAiVaultSessionHome(session, false)
 }
 
+export function prepareAiVaultSessionForTerminalResume(
+  session: AiVaultSession
+): Promise<AiVaultSession> {
+  return prepareAiVaultSessionHome(session, false, true)
+}
+
+export function prepareAiVaultSessionResumeRequest(
+  args: AiVaultPrepareSessionResumeArgs
+): Promise<AiVaultPrepareSessionResumeResult> {
+  return window.api.aiVault.prepareSessionResume(args)
+}
+
+export async function prepareAiVaultTerminalResumeRequest(
+  args: AiVaultPrepareSessionResumeArgs
+): Promise<AiVaultPrepareSessionResumeResult> {
+  const needsHomePreparation = aiVaultSessionNeedsResumePreparation(args)
+  try {
+    // Why: this request checks ownership; old desktop resumes kept the recorded home otherwise.
+    const result = await prepareAiVaultSessionResumeRequest(
+      needsHomePreparation ? args : { ...args, codexHome: null }
+    )
+    if (
+      typeof result?.useRealCodexHome !== 'boolean' ||
+      (result.substituteCodexHome !== undefined && typeof result.substituteCodexHome !== 'string')
+    ) {
+      throw new Error('Invalid aiVault.prepareSessionResume response')
+    }
+    return needsHomePreparation ? result : { useRealCodexHome: false }
+  } catch (error) {
+    if (
+      !args.fork &&
+      parseExecutionHostId(args.executionHostId)?.kind === 'runtime' &&
+      !needsHomePreparation &&
+      isMissingPairedResumePreparation(error)
+    ) {
+      return { useRealCodexHome: false }
+    }
+    throw error
+  }
+}
+
+function isMissingPairedResumePreparation(error: unknown): boolean {
+  if (!(error instanceof Error)) {
+    return false
+  }
+  const desktopPrepareError =
+    error.message.startsWith("Error invoking remote method 'aiVault:prepareSessionResume':") ||
+    error.message.startsWith("Error occurred in handler for 'aiVault:prepareSessionResume':")
+  return (
+    (desktopPrepareError &&
+      readIpcErrorMessage(error) === 'aiVault.prepareSessionResume: method_not_found') ||
+    ('code' in error &&
+      error.code === 'method_not_found' &&
+      error.message === 'Unknown method: aiVault.prepareSessionResume')
+  )
+}
+
 /** Picks the Codex home a fork of `session` runs under, the same way a resume picks it. */
 export function prepareAiVaultSessionForFork(session: AiVaultSession): Promise<AiVaultSession> {
   return prepareAiVaultSessionHome(session, true)
@@ -22,19 +85,23 @@ export function prepareAiVaultSessionForFork(session: AiVaultSession): Promise<A
 
 async function prepareAiVaultSessionHome(
   session: AiVaultSession,
-  fork: boolean
+  fork: boolean,
+  terminalResume = false
 ): Promise<AiVaultSession> {
-  if (!aiVaultSessionNeedsResumePreparation(session)) {
+  if (fork && !aiVaultSessionNeedsResumePreparation(session)) {
     return session
   }
-  const result = await window.api.aiVault.prepareSessionResume({
+  const args: AiVaultPrepareSessionResumeArgs = {
     agent: session.agent,
     sessionId: session.sessionId,
     filePath: session.filePath,
     codexHome: session.codexHome,
     executionHostId: session.executionHostId,
     ...(fork ? { fork: true } : {})
-  })
+  }
+  const result = await (terminalResume
+    ? prepareAiVaultTerminalResumeRequest(args)
+    : prepareAiVaultSessionResumeRequest(args))
   if (result.useRealCodexHome) {
     return { ...session, codexHome: null }
   }