diff --git a/config/focus-setting-read-baseline.txt b/config/focus-setting-read-baseline.txt
index 6ddd89b6570..93fb2d5732d 100644
--- a/config/focus-setting-read-baseline.txt
+++ b/config/focus-setting-read-baseline.txt
@@ -257,7 +257,7 @@
 4 src/renderer/src/lib/workspace-browser-tab-open.ts
 1 src/renderer/src/lib/worktree-activation.ts
 1 src/renderer/src/lib/worktree-jump-navigation.ts
-1 src/renderer/src/lib/worktree-runtime-owner.ts # typed owner resolver and the legacy-fallback adapter the folds moved to (round 3 F0); F8 deleted the deprecated pair
+1 src/renderer/src/lib/worktree-runtime-owner.ts # a setup terminal with no row spawns on the focused runtime
 17 src/renderer/src/runtime/runtime-jira-client.ts
 2 src/renderer/src/runtime/runtime-jira-summary-client.ts
 1 src/renderer/src/runtime/runtime-jira-target.ts
diff --git a/src/renderer/src/components/browser-pane/assemble-chrome/browser-deferred-lifecycle.test.tsx b/src/renderer/src/components/browser-pane/assemble-chrome/browser-deferred-lifecycle.test.tsx
index ffaddf3cff8..d6212a7e14d 100644
--- a/src/renderer/src/components/browser-pane/assemble-chrome/browser-deferred-lifecycle.test.tsx
+++ b/src/renderer/src/components/browser-pane/assemble-chrome/browser-deferred-lifecycle.test.tsx
@@ -35,7 +35,7 @@ vi.mock('@/store', async () => {
   }
 })
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => null,
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => null,
   getExecutionHostIdForWorktree: () => mocks.executionHostId
 }))
 vi.mock('@/components/contextual-tours/use-contextual-tour', () => ({
diff --git a/src/renderer/src/components/browser-pane/assemble-chrome/browser-workspace-pane.retention-props.test.tsx b/src/renderer/src/components/browser-pane/assemble-chrome/browser-workspace-pane.retention-props.test.tsx
index d5f592246fe..36a691b3731 100644
--- a/src/renderer/src/components/browser-pane/assemble-chrome/browser-workspace-pane.retention-props.test.tsx
+++ b/src/renderer/src/components/browser-pane/assemble-chrome/browser-workspace-pane.retention-props.test.tsx
@@ -33,7 +33,7 @@ vi.mock('@/store', () => ({
 }))
 
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => null
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => null
 }))
 
 vi.mock('@/components/contextual-tours/use-contextual-tour', () => ({
diff --git a/src/renderer/src/components/browser-pane/assemble-chrome/browser-workspace-pane.tsx b/src/renderer/src/components/browser-pane/assemble-chrome/browser-workspace-pane.tsx
index 852ef860d55..aa822bc00dc 100644
--- a/src/renderer/src/components/browser-pane/assemble-chrome/browser-workspace-pane.tsx
+++ b/src/renderer/src/components/browser-pane/assemble-chrome/browser-workspace-pane.tsx
@@ -1,6 +1,6 @@
 import { useCallback, useEffect, useMemo } from 'react'
 import { useAppStore } from '@/store'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { isClientHostedBrowserPageHandle } from '@/store/slices/browser'
 import type { BrowserWorkspace as BrowserWorkspaceState } from '../../../../../shared/browser-workspace-types'
 import { destroyPersistentWebview } from '../host-guest/webview-registry'
@@ -41,7 +41,7 @@ export default function BrowserPane({
 }): React.JSX.Element {
   const resolvedChromeShortcutScope = chromeShortcutScope ?? (isActive ? 'focused' : 'inactive')
   const activeRuntimeEnvironmentId = useAppStore((s) =>
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(s, browserTab.worktreeId)
+    runtimeEnvironmentIdOrLocalUnlessTwin(s, browserTab.worktreeId)
   )
   const browserPages = useAppStore((s) =>
     getBrowserPagesForWorkspace(s.browserPagesByWorkspace, browserTab.id)
diff --git a/src/renderer/src/components/browser-pane/stream-remote/use-remote-browser-page-lifecycle.ts b/src/renderer/src/components/browser-pane/stream-remote/use-remote-browser-page-lifecycle.ts
index 349699dda97..88ecd769542 100644
--- a/src/renderer/src/components/browser-pane/stream-remote/use-remote-browser-page-lifecycle.ts
+++ b/src/renderer/src/components/browser-pane/stream-remote/use-remote-browser-page-lifecycle.ts
@@ -1,6 +1,6 @@
 import { useCallback, useEffect, useLayoutEffect, useMemo, useRef, useState } from 'react'
 import { useAppStore } from '@/store'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { RemoteBrowserStreamLifecycle } from './remote-browser-stream-lifecycle'
 import type {
   RemoteBrowserOperationToken,
@@ -237,10 +237,7 @@ export function useRemoteBrowserPageLifecycle({
         return
       }
       const state = useAppStore.getState()
-      const currentEnvironmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
-        state,
-        worktreeId
-      )
+      const currentEnvironmentId = runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)
       const pageStillExists = browserPageExists(browserTab.id)
       if (currentEnvironmentId === activeRuntimeEnvironmentId && pageStillExists) {
         return
diff --git a/src/renderer/src/components/browser-pane/workspace-doc/doc-preview-document-actions.test.ts b/src/renderer/src/components/browser-pane/workspace-doc/doc-preview-document-actions.test.ts
index 66526126f0b..a60f2dcc7de 100644
--- a/src/renderer/src/components/browser-pane/workspace-doc/doc-preview-document-actions.test.ts
+++ b/src/renderer/src/components/browser-pane/workspace-doc/doc-preview-document-actions.test.ts
@@ -28,7 +28,7 @@ vi.mock('@/lib/connection-owner-resolution', () => ({
   getConnectionIdForFileFromState: () => mocks.connectionIdForFile
 }))
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => mocks.worktreeRuntimeOwnerId
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => mocks.worktreeRuntimeOwnerId
 }))
 vi.mock('@/lib/file-owner-runtime-target', () => {
   const getRuntimeTargetForFileOwner = (
diff --git a/src/renderer/src/components/browser-pane/workspace-doc/doc-preview-document-actions.ts b/src/renderer/src/components/browser-pane/workspace-doc/doc-preview-document-actions.ts
index 9208e9619b9..097062aa0e4 100644
--- a/src/renderer/src/components/browser-pane/workspace-doc/doc-preview-document-actions.ts
+++ b/src/renderer/src/components/browser-pane/workspace-doc/doc-preview-document-actions.ts
@@ -2,7 +2,7 @@ import { LOCAL_EXECUTION_HOST_ID } from '../../../../../shared/execution-host'
 import { toast } from 'sonner'
 import { translate } from '@/i18n/i18n'
 import { getConnectionIdForFileFromState } from '@/lib/connection-owner-resolution'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { isTwinWorkspace } from '@/lib/resolve-owner'
 import { detectLanguage } from '@/lib/language-detect'
 import {
@@ -71,7 +71,7 @@ export function openDocPreviewExternally(document: DocPreviewDocument): void {
   // renders through was minted against the worktree's owner at render time, and a tab opened or
   // restored before that owner was known still carries null — which reads as local.
   const runtimeEnvironmentId =
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, document.worktreeId) ??
+    runtimeEnvironmentIdOrLocalUnlessTwin(state, document.worktreeId) ??
     document.runtimeEnvironmentId
   const fileContext = buildWorkspaceFileContextForFile(
     document.worktreeId,
diff --git a/src/renderer/src/components/browser-pane/workspace-doc/workspace-doc-page-pane.test.tsx b/src/renderer/src/components/browser-pane/workspace-doc/workspace-doc-page-pane.test.tsx
index 0b535961469..becffb91763 100644
--- a/src/renderer/src/components/browser-pane/workspace-doc/workspace-doc-page-pane.test.tsx
+++ b/src/renderer/src/components/browser-pane/workspace-doc/workspace-doc-page-pane.test.tsx
@@ -23,7 +23,7 @@ vi.mock('@/store', () => ({
   useAppStore: (selector: (state: unknown) => unknown) => selector(mocks.storeState)
 }))
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => null
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => null
 }))
 vi.mock('./HtmlDocPreview', () => ({
   HtmlDocPreview: ({ holdsGuestFocus }: { holdsGuestFocus?: boolean }) => {
diff --git a/src/renderer/src/components/browser-pane/workspace-doc/workspace-doc-page-pane.tsx b/src/renderer/src/components/browser-pane/workspace-doc/workspace-doc-page-pane.tsx
index 0367d15040f..f6b2dd8f977 100644
--- a/src/renderer/src/components/browser-pane/workspace-doc/workspace-doc-page-pane.tsx
+++ b/src/renderer/src/components/browser-pane/workspace-doc/workspace-doc-page-pane.tsx
@@ -1,6 +1,6 @@
 import { useMemo } from 'react'
 import { getRelativePathInsideRoot } from '@/lib/path'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { useAppStore } from '@/store'
 import { HtmlDocPreview } from './HtmlDocPreview'
 import type { BrowserPage } from '../../../../../shared/browser-workspace-types'
@@ -24,7 +24,7 @@ export function WorkspaceDocPagePane({
   // Why resolved here rather than stored on the page: ownership moves. A page persisted before a
   // pairing or an SSH reconnect would otherwise route its document actions at yesterday's host.
   const runtimeEnvironmentId = useAppStore((store) =>
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(store, worktreeId)
+    runtimeEnvironmentIdOrLocalUnlessTwin(store, worktreeId)
   )
   const relativePath = useMemo(
     () => getRelativePathInsideRoot(filePath, worktreeRoot) ?? filePath,
diff --git a/src/renderer/src/components/native-chat/NativeChatInlineVisual.open-as-file.test.tsx b/src/renderer/src/components/native-chat/NativeChatInlineVisual.open-as-file.test.tsx
index 6ea1e48c877..3c1699cb077 100644
--- a/src/renderer/src/components/native-chat/NativeChatInlineVisual.open-as-file.test.tsx
+++ b/src/renderer/src/components/native-chat/NativeChatInlineVisual.open-as-file.test.tsx
@@ -22,7 +22,7 @@ vi.mock('@/lib/connection-owner-resolution', async (importOriginal) => ({
 }))
 vi.mock('@/lib/worktree-runtime-owner', async (importOriginal) => ({
   ...(await importOriginal<typeof WorktreeRuntimeOwnerModule>()),
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => 'env-1'
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => 'env-1'
 }))
 
 import { NativeChatInlineVisual } from './NativeChatInlineVisual'
diff --git a/src/renderer/src/components/native-chat/native-chat-file-link.ts b/src/renderer/src/components/native-chat/native-chat-file-link.ts
index c8a23104b89..b7aeea15717 100644
--- a/src/renderer/src/components/native-chat/native-chat-file-link.ts
+++ b/src/renderer/src/components/native-chat/native-chat-file-link.ts
@@ -4,7 +4,7 @@ import {
   resolveExplicitFileLinkTarget,
   resolveExplicitFileLinkTargetPath
 } from '@/lib/explicit-file-link-target'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import type { AppState } from '@/store/types'
 import { resolveNativeChatTabDirectory } from './native-chat-tab-directory'
 
@@ -122,7 +122,7 @@ function resolveNativeChatFileLinkContextForOwner(
   return {
     worktreeId,
     worktreePath,
-    runtimeEnvironmentId: runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId),
+    runtimeEnvironmentId: runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId),
     sourceTabId: terminalTabId
   }
 }
diff --git a/src/renderer/src/components/native-chat/native-chat-http-link-source-owner.test.ts b/src/renderer/src/components/native-chat/native-chat-http-link-source-owner.test.ts
index aad334a46fe..86ea93e03bb 100644
--- a/src/renderer/src/components/native-chat/native-chat-http-link-source-owner.test.ts
+++ b/src/renderer/src/components/native-chat/native-chat-http-link-source-owner.test.ts
@@ -6,15 +6,14 @@ import {
 } from './native-chat-http-link-source-owner'
 
 const mocks = vi.hoisted(() => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: vi.fn(),
+  runtimeEnvironmentIdOrLocalUnlessTwin: vi.fn(),
   getConnectionIdFromState: vi.fn(),
   canOpenWorkspaceBrowserTabOnRuntime: vi.fn(),
   canOpenWorkspaceBrowserTabOnSsh: vi.fn()
 }))
 
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin:
-    mocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin
+  runtimeEnvironmentIdOrLocalUnlessTwin: mocks.runtimeEnvironmentIdOrLocalUnlessTwin
 }))
 vi.mock('@/lib/connection-owner-resolution', () => ({
   getConnectionIdFromState: mocks.getConnectionIdFromState
@@ -32,7 +31,7 @@ afterEach(() => {
 
 describe('resolveNativeChatHttpLinkSourceOwner', () => {
   it('prefers the workspace runtime owner', () => {
-    mocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin.mockReturnValue('env-1')
+    mocks.runtimeEnvironmentIdOrLocalUnlessTwin.mockReturnValue('env-1')
 
     expect(resolveNativeChatHttpLinkSourceOwner(state, 'wt-1')).toEqual({
       kind: 'runtime',
@@ -42,7 +41,7 @@ describe('resolveNativeChatHttpLinkSourceOwner', () => {
   })
 
   it('falls back to the SSH connection that owns the workspace', () => {
-    mocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin.mockReturnValue(null)
+    mocks.runtimeEnvironmentIdOrLocalUnlessTwin.mockReturnValue(null)
     mocks.getConnectionIdFromState.mockReturnValue('ssh-1')
 
     expect(resolveNativeChatHttpLinkSourceOwner(state, 'wt-1')).toEqual({
@@ -52,7 +51,7 @@ describe('resolveNativeChatHttpLinkSourceOwner', () => {
   })
 
   it('reads a null connection as local', () => {
-    mocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin.mockReturnValue(null)
+    mocks.runtimeEnvironmentIdOrLocalUnlessTwin.mockReturnValue(null)
     mocks.getConnectionIdFromState.mockReturnValue(null)
 
     expect(resolveNativeChatHttpLinkSourceOwner(state, 'wt-1')).toEqual({ kind: 'local' })
@@ -61,7 +60,7 @@ describe('resolveNativeChatHttpLinkSourceOwner', () => {
   // An unresolved owner must not be mistaken for local: a remote link would then
   // open against the wrong host.
   it('reports an unresolved owner as unknown', () => {
-    mocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin.mockReturnValue(null)
+    mocks.runtimeEnvironmentIdOrLocalUnlessTwin.mockReturnValue(null)
     mocks.getConnectionIdFromState.mockReturnValue(undefined)
 
     expect(resolveNativeChatHttpLinkSourceOwner(state, 'wt-1')).toEqual({ kind: 'unknown' })
diff --git a/src/renderer/src/components/native-chat/native-chat-http-link-source-owner.ts b/src/renderer/src/components/native-chat/native-chat-http-link-source-owner.ts
index b5fc881bb42..9b8798f2f26 100644
--- a/src/renderer/src/components/native-chat/native-chat-http-link-source-owner.ts
+++ b/src/renderer/src/components/native-chat/native-chat-http-link-source-owner.ts
@@ -4,7 +4,7 @@ import {
   canOpenWorkspaceBrowserTabOnRuntime,
   canOpenWorkspaceBrowserTabOnSsh
 } from '@/lib/workspace-browser-tab-open'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import type { AppState } from '@/store/types'
 
 /** The chat transcript has no PTY, so link ownership comes from the session's
@@ -14,7 +14,7 @@ export function resolveNativeChatHttpLinkSourceOwner(
   state: AppState,
   worktreeId: string
 ): HttpLinkSourceOwner {
-  const runtimeEnvironmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId)
+  const runtimeEnvironmentId = runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)
   if (runtimeEnvironmentId) {
     return { kind: 'runtime', runtimeEnvironmentId }
   }
diff --git a/src/renderer/src/components/native-chat/native-chat-runtime-owner.ts b/src/renderer/src/components/native-chat/native-chat-runtime-owner.ts
index dd5b6558119..3eecf88a1c7 100644
--- a/src/renderer/src/components/native-chat/native-chat-runtime-owner.ts
+++ b/src/renderer/src/components/native-chat/native-chat-runtime-owner.ts
@@ -1,4 +1,4 @@
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import type { WorktreeRuntimeOwnerState } from '@/lib/worktree-runtime-owner-state'
 import type { AppState } from '@/store/types'
 import {
@@ -26,7 +26,7 @@ export function selectNativeChatRuntimeEnvironmentId(
   state: NativeChatRuntimeOwnerState,
   terminalTabId: string
 ): string | null {
-  return runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
+  return runtimeEnvironmentIdOrLocalUnlessTwin(
     state,
     findTerminalTabWorktreeId(state.tabsByWorktree, terminalTabId)
   )
@@ -35,7 +35,7 @@ export function selectNativeChatRuntimeEnvironmentId(
 export function createNativeChatRuntimeSelector(terminalTabId: string) {
   const selectOwner = createNativeChatTabOwnerSelector(terminalTabId)
   return (state: NativeChatRuntimeOwnerState): string | null => {
-    return runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
+    return runtimeEnvironmentIdOrLocalUnlessTwin(
       state,
       selectOwner({ tabsByWorktree: state.tabsByWorktree })
     )
diff --git a/src/renderer/src/components/right-sidebar/FileExplorer.tsx b/src/renderer/src/components/right-sidebar/FileExplorer.tsx
index 3e9157e04f1..24ffbbe80c4 100644
--- a/src/renderer/src/components/right-sidebar/FileExplorer.tsx
+++ b/src/renderer/src/components/right-sidebar/FileExplorer.tsx
@@ -1,6 +1,6 @@
 import React, { useCallback, useMemo } from 'react'
 import { useAppStore } from '@/store'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { getWorkspaceFileRevealOwner } from '@/lib/reveal-in-file-manager'
 import { getRouteForLocalPathOpenOwner } from '@/lib/local-path-open-guard'
 import { useActiveWorktree, useRepoById } from '@/store/selectors'
@@ -51,7 +51,7 @@ function FileExplorerFiles(): React.JSX.Element {
   const searchPanel = useFileSearchPanel(explorerView)
   const activeWorktreeId = useAppStore((s) => s.activeWorktreeId)
   const runtimeEnvironmentId = useAppStore((s) =>
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(s, activeWorktreeId)
+    runtimeEnvironmentIdOrLocalUnlessTwin(s, activeWorktreeId)
   )
   const wslHostUnavailable = useWslHostUnavailableReason(activeWorktreeId)
   const activeWorktree = useActiveWorktree()
diff --git a/src/renderer/src/components/right-sidebar/checks-panel/use-checks-panel-controller-state.tsx b/src/renderer/src/components/right-sidebar/checks-panel/use-checks-panel-controller-state.tsx
index 0864da3c5b8..acffc243b97 100644
--- a/src/renderer/src/components/right-sidebar/checks-panel/use-checks-panel-controller-state.tsx
+++ b/src/renderer/src/components/right-sidebar/checks-panel/use-checks-panel-controller-state.tsx
@@ -9,7 +9,7 @@ import { useMountedRef } from '@/hooks/useMountedRef'
 import { useConfirmationDialog } from '@/components/confirmation-dialog-context'
 import { getWorktreeGitIdentityDisplay } from '../../../../../shared/worktree/git-identity-display'
 import { resolveRepoWorktreeLaunchPlatform } from '@/lib/execution-host-facts'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { normalizeGlobalWindowsRuntimeDefault } from '../../../../../shared/project-execution-runtime'
 import {
   saveSourceControlActionRecipe,
@@ -223,7 +223,7 @@ export function useChecksPanelControllerState() {
       ? resolveRepoWorktreeLaunchPlatform(useAppStore.getState(), repo, activeWorktree)
       : undefined
   const runtimeEnvironmentId = useAppStore((s) =>
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(s, activeWorktreeId)
+    runtimeEnvironmentIdOrLocalUnlessTwin(s, activeWorktreeId)
   )
   const ownerSettings = useMemo<AppState['settings']>(
     () =>
diff --git a/src/renderer/src/components/right-sidebar/file-explorer-row-context-menu.tsx b/src/renderer/src/components/right-sidebar/file-explorer-row-context-menu.tsx
index e65c21ae124..30ff70084be 100644
--- a/src/renderer/src/components/right-sidebar/file-explorer-row-context-menu.tsx
+++ b/src/renderer/src/components/right-sidebar/file-explorer-row-context-menu.tsx
@@ -34,7 +34,7 @@ import {
   revealInFileManager
 } from '@/lib/reveal-in-file-manager'
 import { isRevealOrEditorOpenBlocked } from '@/lib/local-path-open-guard'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import type { FileExplorerRowProps } from './FileExplorerRow'
 import {
   shouldShowCollapseFolderAction,
@@ -123,7 +123,7 @@ export function FileExplorerRowContextMenu({
   const revealOwner = useAppStore((s) =>
     getWorkspaceFileRevealOwner(s, s.activeWorktreeId, {
       connectionId,
-      runtimeEnvironmentId: runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(s, s.activeWorktreeId)
+      runtimeEnvironmentId: runtimeEnvironmentIdOrLocalUnlessTwin(s, s.activeWorktreeId)
     })
   )
   const revealBlocked = isRevealOrEditorOpenBlocked(revealOwner)
diff --git a/src/renderer/src/components/right-sidebar/git-status-file-watch-refresh.ts b/src/renderer/src/components/right-sidebar/git-status-file-watch-refresh.ts
index ad8e9f014d4..f9ff00af392 100644
--- a/src/renderer/src/components/right-sidebar/git-status-file-watch-refresh.ts
+++ b/src/renderer/src/components/right-sidebar/git-status-file-watch-refresh.ts
@@ -2,7 +2,7 @@ import { useEffect, useRef } from 'react'
 import { useAppStore } from '@/store'
 import { shouldPollActiveGitStatus } from '@/lib/passive-macos-app-data-access'
 import { isWindowVisible } from '@/lib/window-visibility-interval'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import {
   normalizeRuntimePathForComparison,
   relativePathInsideRoot
@@ -72,7 +72,7 @@ export function useGitStatusFileWatchRefresh({
   worktreePath
 }: UseGitStatusFileWatchRefreshParams): void {
   const activeRuntimeEnvironmentId = useAppStore((state) =>
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, activeWorktreeId)
+    runtimeEnvironmentIdOrLocalUnlessTwin(state, activeWorktreeId)
   )
   const fetchStatusRef = useRef(fetchStatus)
   fetchStatusRef.current = fetchStatus
diff --git a/src/renderer/src/components/right-sidebar/source-control-entry-context-menu.test.tsx b/src/renderer/src/components/right-sidebar/source-control-entry-context-menu.test.tsx
index 3b5ab76bf4d..7d1a729a122 100644
--- a/src/renderer/src/components/right-sidebar/source-control-entry-context-menu.test.tsx
+++ b/src/renderer/src/components/right-sidebar/source-control-entry-context-menu.test.tsx
@@ -48,7 +48,7 @@ vi.mock('@/store', () => ({
 }))
 
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => ownerRuntime.environmentId
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => ownerRuntime.environmentId
 }))
 
 vi.mock(import('@/lib/reveal-in-file-manager'), async (importOriginal) => ({
diff --git a/src/renderer/src/components/right-sidebar/source-control/listing/entry-context-menu.tsx b/src/renderer/src/components/right-sidebar/source-control/listing/entry-context-menu.tsx
index 8581d9b2102..55b01910d0e 100644
--- a/src/renderer/src/components/right-sidebar/source-control/listing/entry-context-menu.tsx
+++ b/src/renderer/src/components/right-sidebar/source-control/listing/entry-context-menu.tsx
@@ -25,7 +25,7 @@ import {
   getRouteForLocalPathOpenOwner,
   isRevealOrEditorOpenBlocked
 } from '@/lib/local-path-open-guard'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { NO_OPEN_IN_APPLICATIONS } from '@/lib/open-in-application-selection'
 import {
   getOpenInEntryAvailability,
@@ -63,7 +63,7 @@ export function SourceControlEntryContextMenu({
   // Why: a repo can belong to a runtime other than the focused one, and the OS reveal
   // cannot tell that host's path from a local one of the same name.
   const runtimeEnvironmentId = useAppStore((s) =>
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(s, currentWorktreeId)
+    runtimeEnvironmentIdOrLocalUnlessTwin(s, currentWorktreeId)
   )
   const revealOwner = useAppStore((s) =>
     getWorkspaceFileRevealOwner(s, currentWorktreeId, { connectionId, runtimeEnvironmentId })
diff --git a/src/renderer/src/components/right-sidebar/use-file-explorer-tree-pane-state.ts b/src/renderer/src/components/right-sidebar/use-file-explorer-tree-pane-state.ts
index 6767c75d53e..abf594a6d65 100644
--- a/src/renderer/src/components/right-sidebar/use-file-explorer-tree-pane-state.ts
+++ b/src/renderer/src/components/right-sidebar/use-file-explorer-tree-pane-state.ts
@@ -1,7 +1,7 @@
 import type { Dispatch, RefObject, SetStateAction } from 'react'
 import { useEffect, useMemo, useRef } from 'react'
 import { useAppStore } from '@/store'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { useWorkspaceFileBrowserActionPredicate } from '@/lib/file-preview'
 import { openWorkspaceFile } from '@/lib/workspace-file-open'
 import type { RuntimeFileOperationArgs } from '@/runtime/runtime-file-client-types'
@@ -130,7 +130,7 @@ export function useFileExplorerTreePaneState({
       : false
   })
   const ownerRuntimeEnvironmentId = useAppStore((s) =>
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(s, activeWorktreeId)
+    runtimeEnvironmentIdOrLocalUnlessTwin(s, activeWorktreeId)
   )
   const toggleDir = useAppStore((s) => s.toggleDir)
   const makePreviewFilePermanent = useAppStore((s) => s.makePreviewFilePermanent)
diff --git a/src/renderer/src/components/right-sidebar/useFileSearchRunner.ts b/src/renderer/src/components/right-sidebar/useFileSearchRunner.ts
index 1002ac2e93b..cfdc485071d 100644
--- a/src/renderer/src/components/right-sidebar/useFileSearchRunner.ts
+++ b/src/renderer/src/components/right-sidebar/useFileSearchRunner.ts
@@ -14,7 +14,7 @@ import { searchRuntimeFiles } from '@/runtime/runtime-file-search-client'
 import { useAppStore } from '@/store'
 import {
   getExecutionHostIdForWorktree,
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin
+  runtimeEnvironmentIdOrLocalUnlessTwin
 } from '@/lib/worktree-runtime-owner'
 import { isTwinWorkspace } from '@/lib/resolve-owner'
 import type { SearchResult } from '../../../../shared/code-search-types'
@@ -45,7 +45,7 @@ export function useFileSearchRunner({
   cancelPendingSearch: () => void
 } {
   const runtimeEnvironmentId = useAppStore((state) =>
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, activeWorktreeId)
+    runtimeEnvironmentIdOrLocalUnlessTwin(state, activeWorktreeId)
   )
   const executionHostId = useAppStore((state) =>
     getExecutionHostIdForWorktree(state, activeWorktreeId)
diff --git a/src/renderer/src/components/right-sidebar/useFileSearchScope.ts b/src/renderer/src/components/right-sidebar/useFileSearchScope.ts
index afc52fa393e..e206d04aac6 100644
--- a/src/renderer/src/components/right-sidebar/useFileSearchScope.ts
+++ b/src/renderer/src/components/right-sidebar/useFileSearchScope.ts
@@ -2,7 +2,7 @@ import { useCallback, useEffect } from 'react'
 import { useAppStore } from '@/store'
 import {
   getExecutionHostIdForWorktree,
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin
+  runtimeEnvironmentIdOrLocalUnlessTwin
 } from '@/lib/worktree-runtime-owner'
 import {
   isFileSearchResultOwnerCurrent,
@@ -25,7 +25,7 @@ export function useFileSearchScope({
   updateActiveSearchState: (updates: { results: null; resultOwner: null; error: null }) => void
 }) {
   const runtimeEnvironmentId = useAppStore((state) =>
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, activeWorktreeId)
+    runtimeEnvironmentIdOrLocalUnlessTwin(state, activeWorktreeId)
   )
   const executionHostId = useAppStore((state) =>
     getExecutionHostIdForWorktree(state, activeWorktreeId)
diff --git a/src/renderer/src/components/tab-bar/use-tab-bar-runtime-model-worktree-write-probe.ts b/src/renderer/src/components/tab-bar/use-tab-bar-runtime-model-worktree-write-probe.ts
index 2c208ef79e2..4cc17f03ad7 100644
--- a/src/renderer/src/components/tab-bar/use-tab-bar-runtime-model-worktree-write-probe.ts
+++ b/src/renderer/src/components/tab-bar/use-tab-bar-runtime-model-worktree-write-probe.ts
@@ -107,7 +107,7 @@ export function tabBarRuntimeModelStubs(): Record<string, () => Record<string, u
     detectedAgents: () => ({ useDetectedAgents: () => DETECTED_AGENTS }),
     detectionTarget: () => ({ useAgentDetectionTargetForWorktree: () => null }),
     connectionContext: () => ({ getConnectionIdFromState: () => null }),
-    runtimeOwner: () => ({ runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => null }),
+    runtimeOwner: () => ({ runtimeEnvironmentIdOrLocalUnlessTwin: () => null }),
     nativeChatReadability: () => ({ isNativeChatTranscriptLocalReadable: () => false }),
     creationPolicy: () => ({ getClientCreationActionPolicy: () => CREATION_POLICY }),
     agentProjections: () => ({ selectTabBarAgentProjections: () => AGENT_PROJECTIONS }),
diff --git a/src/renderer/src/components/tab-bar/use-tab-bar-runtime-model.ts b/src/renderer/src/components/tab-bar/use-tab-bar-runtime-model.ts
index ff979fb25d8..096853d867b 100644
--- a/src/renderer/src/components/tab-bar/use-tab-bar-runtime-model.ts
+++ b/src/renderer/src/components/tab-bar/use-tab-bar-runtime-model.ts
@@ -11,7 +11,7 @@ import { useAgentDetectionTargetForWorktree } from '@/hooks/useAgentDetectionTar
 import { getConnectionIdFromState } from '@/lib/connection-context'
 import { getLocalProjectExecutionRuntimeContext } from '@/lib/local-preflight-context'
 import { isNativeChatTranscriptLocalReadable } from '@/lib/native-chat-transcript-readability'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { runtimeTargetForOwnerEnvironment } from '@/runtime/runtime-client-target'
 import { useOptionalShortcutLabel, useShortcutLabel } from '@/hooks/useShortcutLabel'
 import {
@@ -126,7 +126,7 @@ export function useTabBarRuntimeModel({
   const settings = useAppStore((s) => s.settings)
   // Why: use the worktree's owning host so offered Windows shells match the host that actually runs the terminal.
   const activeRuntimeEnvironmentId = useAppStore((s) =>
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(s, worktreeId)
+    runtimeEnvironmentIdOrLocalUnlessTwin(s, worktreeId)
   )
   // Why: retained tab strips rerun selectors on every store write; reuse canonical indexes, don't flatten both slices here.
   const worktreeConnectionId = useAppStore(
diff --git a/src/renderer/src/components/tab-bar/web-runtime-tab-move-mirror.ts b/src/renderer/src/components/tab-bar/web-runtime-tab-move-mirror.ts
index f15aedab71e..5d40f6da463 100644
--- a/src/renderer/src/components/tab-bar/web-runtime-tab-move-mirror.ts
+++ b/src/renderer/src/components/tab-bar/web-runtime-tab-move-mirror.ts
@@ -1,5 +1,5 @@
 import type { RuntimeMobileSessionTabMove } from '../../../../shared/runtime-types'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { useAppStore } from '../../store'
 import { isWebRuntimeSessionActive } from '../../runtime/web-runtime-session-environment'
 import { moveWebRuntimeSessionTab } from '../../runtime/web-runtime-session-tab-move'
@@ -9,7 +9,7 @@ export function mirrorWebRuntimeTabMove(
     worktreeId: string
   }
 ): void {
-  const environmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
+  const environmentId = runtimeEnvironmentIdOrLocalUnlessTwin(
     useAppStore.getState(),
     args.worktreeId
   )
diff --git a/src/renderer/src/components/tab-group/useTabGroupActivationCommands.ts b/src/renderer/src/components/tab-group/useTabGroupActivationCommands.ts
index 7a7ec61aa57..6580676a42f 100644
--- a/src/renderer/src/components/tab-group/useTabGroupActivationCommands.ts
+++ b/src/renderer/src/components/tab-group/useTabGroupActivationCommands.ts
@@ -5,7 +5,7 @@ import { focusTerminalTabSurface } from '../../lib/focus-terminal-tab-surface'
 import { TOGGLE_TERMINAL_PANE_EXPAND_EVENT } from '@/constants/terminal'
 import { activateWebRuntimeSessionTab } from '../../runtime/web-runtime-session-tab-lifecycle'
 import { isWebRuntimeSessionActive } from '../../runtime/web-runtime-session-environment'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { browserWorkspaceHasRemoteOwner } from '@/runtime/remote-browser-tab-ownership'
 import { activateStructuredAgentSessionTab } from '@/lib/structured-agent-session-tab-activation'
 import type { TabGroupWorktreeSnapshot } from './useTabGroupItemProjections'
@@ -38,7 +38,7 @@ export function useTabGroupActivationCommands({
       }
       focusGroup(worktreeId, groupId)
       activateTab(item.id)
-      const runtimeEnvironmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
+      const runtimeEnvironmentId = runtimeEnvironmentIdOrLocalUnlessTwin(
         useAppStore.getState(),
         worktreeId
       )
@@ -117,7 +117,7 @@ export function useTabGroupActivationCommands({
       }
       focusGroup(worktreeId, groupId)
       activateTab(item.id)
-      const runtimeEnvironmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
+      const runtimeEnvironmentId = runtimeEnvironmentIdOrLocalUnlessTwin(
         useAppStore.getState(),
         worktreeId
       )
diff --git a/src/renderer/src/components/tab-group/useTabGroupCreationCommands.local-shell.test.ts b/src/renderer/src/components/tab-group/useTabGroupCreationCommands.local-shell.test.ts
index 4649d82be95..d7d3f37e858 100644
--- a/src/renderer/src/components/tab-group/useTabGroupCreationCommands.local-shell.test.ts
+++ b/src/renderer/src/components/tab-group/useTabGroupCreationCommands.local-shell.test.ts
@@ -13,7 +13,7 @@ const mocks = vi.hoisted(() => ({
   openNewBrowserTabInActiveWorkspace: vi.fn(),
   openNewMarkdownInActiveWorkspace: vi.fn(),
   openNewTerminalTabInActiveWorkspace: vi.fn(),
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: vi.fn(),
+  runtimeEnvironmentIdOrLocalUnlessTwin: vi.fn(),
   focusTerminalTabSurface: vi.fn(),
   runtimeCall: vi.fn()
 }))
@@ -21,8 +21,7 @@ const mocks = vi.hoisted(() => ({
 vi.mock('react', async () => await stubHeadlessReact())
 
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin:
-    mocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin
+  runtimeEnvironmentIdOrLocalUnlessTwin: mocks.runtimeEnvironmentIdOrLocalUnlessTwin
 }))
 vi.mock('@/lib/runtime-session-mirror-owners', () => ({
   getRuntimeSessionMirrorEnvironmentIds: () => []
@@ -77,7 +76,7 @@ describe('tab group "+" menu shell launch on a locally-owned workspace', () => {
   beforeEach(() => {
     vi.clearAllMocks()
     storeState.activeWorkspaceExecutionHostId = 'local'
-    mocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin.mockReturnValue(null)
+    mocks.runtimeEnvironmentIdOrLocalUnlessTwin.mockReturnValue(null)
     stubRuntimeEnvironmentBridge({ call: mocks.runtimeCall })
   })
 
diff --git a/src/renderer/src/components/tab-group/useTabGroupCreationCommands.ts b/src/renderer/src/components/tab-group/useTabGroupCreationCommands.ts
index f72d1ae2e0a..edf25e933ae 100644
--- a/src/renderer/src/components/tab-group/useTabGroupCreationCommands.ts
+++ b/src/renderer/src/components/tab-group/useTabGroupCreationCommands.ts
@@ -9,7 +9,7 @@ import { openTabBarEntry, type TabCreateEntryArgs } from '../tab-bar/tab-create-
 import { openMobileEmulatorTab } from '@/lib/open-mobile-emulator-tab'
 import { ensureSimulatorTab, getSimulatorTabForWorktree } from '@/lib/ensure-simulator-tab'
 import { buildDuplicatedBrowserTabOptions } from '@/lib/duplicate-browser-tab-options'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { browserWorkspaceHasRemoteOwner } from '@/runtime/remote-browser-tab-ownership'
 import { getClientCreationActionPolicy } from '@/lib/client-creation-action-policy'
 import type { TabGroupWorktreeSnapshot } from './useTabGroupItemProjections'
@@ -70,10 +70,7 @@ export function useTabGroupCreationCommands({
         if (!source) {
           return
         }
-        const runtimeEnvironmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
-          state,
-          worktreeId
-        )
+        const runtimeEnvironmentId = runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)
         const browserAvailability = getClientCreationActionPolicy(state, worktreeId)[
           'managed-browser'
         ]
@@ -116,7 +113,7 @@ export function useTabGroupCreationCommands({
     },
     newTerminalWithShell: (shellOverride: string) => {
       void (async () => {
-        const environmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
+        const environmentId = runtimeEnvironmentIdOrLocalUnlessTwin(
           useAppStore.getState(),
           worktreeId
         )
diff --git a/src/renderer/src/components/terminal-pane/terminal-input-host-platform.ts b/src/renderer/src/components/terminal-pane/terminal-input-host-platform.ts
index 61e4abf8393..ea9a26f200a 100644
--- a/src/renderer/src/components/terminal-pane/terminal-input-host-platform.ts
+++ b/src/renderer/src/components/terminal-pane/terminal-input-host-platform.ts
@@ -4,7 +4,7 @@ import { isWslUncPath } from '../../../../shared/wsl-paths'
 import { getConnectionIdFromState } from '@/lib/connection-context'
 import {
   getExecutionHostIdForWorktree,
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin
+  runtimeEnvironmentIdOrLocalUnlessTwin
 } from '@/lib/worktree-runtime-owner'
 import { getRemoteRuntimePtyEnvironmentId } from '@/runtime/runtime-terminal-stream'
 import type { AppState } from '@/store/types'
@@ -90,10 +90,7 @@ export function resolveTerminalInputHostPlatform(args: {
 
   const host = parseExecutionHostId(getExecutionHostIdForWorktree(args.state, args.worktreeId))
   if (host?.kind === 'ssh') {
-    const ownerEnvironmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
-      args.state,
-      args.worktreeId
-    )
+    const ownerEnvironmentId = runtimeEnvironmentIdOrLocalUnlessTwin(args.state, args.worktreeId)
     return ownerEnvironmentId
       ? (args.state.sshStateByEnvironment
           .get(ownerEnvironmentId)
diff --git a/src/renderer/src/components/terminal-pane/terminal-paste-runtime.ts b/src/renderer/src/components/terminal-pane/terminal-paste-runtime.ts
index 983ad7f5e85..9cd6aec6d34 100644
--- a/src/renderer/src/components/terminal-pane/terminal-paste-runtime.ts
+++ b/src/renderer/src/components/terminal-pane/terminal-paste-runtime.ts
@@ -4,7 +4,7 @@ import {
   isRemoteRuntimePtyId,
   parseRemoteRuntimePtyId
 } from '../../../../shared/remote-runtime-pty-id'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import type { WorktreeRuntimeOwnerState } from '@/lib/worktree-runtime-owner-state'
 import type { PtyTransport } from './pty-transport-types'
 
@@ -122,6 +122,6 @@ export function resolveTerminalPasteRuntimeEnvironmentId(
   const ptyId = transport?.getPtyId() ?? null
   return (
     (ptyId ? parseRemoteRuntimePtyId(ptyId)?.environmentId : null) ??
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId)
+    runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)
   )
 }
diff --git a/src/renderer/src/components/terminal-workspace-model.ts b/src/renderer/src/components/terminal-workspace-model.ts
index 360ae69ced8..68ba7ee9728 100644
--- a/src/renderer/src/components/terminal-workspace-model.ts
+++ b/src/renderer/src/components/terminal-workspace-model.ts
@@ -1,7 +1,7 @@
 import type { Tab } from '../../../shared/tab-types'
 import type { KeybindingContext } from '../../../shared/keybindings'
 import { useAppStore } from '../store'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { isEditorTabContentType } from '@/store/slices/editor/tabs/editor-tab-content-type'
 
 export const CLOSE_DIALOG_DEBOUNCE_MS = 200
@@ -56,7 +56,7 @@ export function isPinnedVisibleTab(
 }
 
 export function getActiveWorktreeRuntimeEnvironmentId(worktreeId: string | null): string | null {
-  return runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(useAppStore.getState(), worktreeId)
+  return runtimeEnvironmentIdOrLocalUnlessTwin(useAppStore.getState(), worktreeId)
 }
 
 export function isPinnedActiveEditorTab(
diff --git a/src/renderer/src/components/worktree-jump-palette-quick-action-availability.test.tsx b/src/renderer/src/components/worktree-jump-palette-quick-action-availability.test.tsx
index b641cc6d3e7..b8d9102e352 100644
--- a/src/renderer/src/components/worktree-jump-palette-quick-action-availability.test.tsx
+++ b/src/renderer/src/components/worktree-jump-palette-quick-action-availability.test.tsx
@@ -12,7 +12,7 @@ const mocks = vi.hoisted(() => ({ state: {} as Record<string, unknown> }))
 
 vi.mock('@/store', () => ({ useAppStore: { getState: () => mocks.state } }))
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => RUNTIME_ID
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => RUNTIME_ID
 }))
 vi.mock('@/components/sidebar/delete-worktree-flow', () => ({ runWorktreeDelete: vi.fn() }))
 
diff --git a/src/renderer/src/hooks/editor-external-watch-targets.ts b/src/renderer/src/hooks/editor-external-watch-targets.ts
index 46c18de44a0..7f36f0ec7b2 100644
--- a/src/renderer/src/hooks/editor-external-watch-targets.ts
+++ b/src/renderer/src/hooks/editor-external-watch-targets.ts
@@ -4,7 +4,7 @@ import { findWorktreeById } from '@/store/slices/worktree-helpers'
 import { isVirtualEditorFile } from '@/store/slices/editor/tabs/editor-tab-content-type'
 import { findRepoForHost } from '@/store/slices/repo-host-identity'
 import { isLocalWindowsDesktopClient } from '@/lib/desktop-window-chrome'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import {
   parseExecutionHostId,
   toRuntimeExecutionHostId,
@@ -123,7 +123,7 @@ function getSidebarWatchConsumer(
   worktreeId: string
 ): WatchConsumer {
   // Why: sidebar watcher must follow the selected worktree's host owner, not the host currently focused in the UI.
-  const owner = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId)
+  const owner = runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)
   if (owner) {
     return { owner, hostId: toRuntimeExecutionHostId(owner) }
   }
diff --git a/src/renderer/src/hooks/ipc-events/browser-state-capture-paint-hold.test.ts b/src/renderer/src/hooks/ipc-events/browser-state-capture-paint-hold.test.ts
index 853de2315ab..93edfbf7a3d 100644
--- a/src/renderer/src/hooks/ipc-events/browser-state-capture-paint-hold.test.ts
+++ b/src/renderer/src/hooks/ipc-events/browser-state-capture-paint-hold.test.ts
@@ -4,7 +4,7 @@ vi.mock('../../store', () => ({
   useAppStore: { getState: () => ({}) }
 }))
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => null
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => null
 }))
 vi.mock('@/components/browser-pane/describe-page/live-browser-url-registry', () => ({
   rememberLiveBrowserUrl: vi.fn()
diff --git a/src/renderer/src/hooks/ipc-events/browser-state-ipc-bridge.ts b/src/renderer/src/hooks/ipc-events/browser-state-ipc-bridge.ts
index a84bb1c3db7..17caab7c151 100644
--- a/src/renderer/src/hooks/ipc-events/browser-state-ipc-bridge.ts
+++ b/src/renderer/src/hooks/ipc-events/browser-state-ipc-bridge.ts
@@ -1,5 +1,5 @@
 import { rememberLiveBrowserUrl } from '@/components/browser-pane/describe-page/live-browser-url-registry'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { resolveBrowserSourceUnifiedTab } from '@/lib/browser-workspace-source-resolution'
 import { redactKagiSessionToken } from '../../../../shared/browser-url'
 import { useAppStore } from '../../store'
@@ -138,10 +138,7 @@ export function registerBrowserStateIpcBridge(
       const sourcePage = Object.values(store.browserPagesByWorkspace)
         .flat()
         .find((page) => page.id === browserPageId)
-      if (
-        !sourcePage ||
-        runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(store, sourcePage.worktreeId)
-      ) {
+      if (!sourcePage || runtimeEnvironmentIdOrLocalUnlessTwin(store, sourcePage.worktreeId)) {
         return
       }
       // Why: the link inherits the opener's cookie jar. Falling back to the default profile would let
diff --git a/src/renderer/src/hooks/ipc-events/browser-state-open-link-profile.test.ts b/src/renderer/src/hooks/ipc-events/browser-state-open-link-profile.test.ts
index 75094ad2854..7512ec8bd4b 100644
--- a/src/renderer/src/hooks/ipc-events/browser-state-open-link-profile.test.ts
+++ b/src/renderer/src/hooks/ipc-events/browser-state-open-link-profile.test.ts
@@ -11,7 +11,7 @@ vi.mock('../../store', () => ({
   useAppStore: { getState: () => storeState.value }
 }))
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => null
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => null
 }))
 vi.mock('@/components/browser-pane/describe-page/live-browser-url-registry', () => ({
   rememberLiveBrowserUrl: vi.fn()
diff --git a/src/renderer/src/lib/activate-ai-vault-structured-session-reveal.test.ts b/src/renderer/src/lib/activate-ai-vault-structured-session-reveal.test.ts
index 081b0b31cd8..19e17c1555f 100644
--- a/src/renderer/src/lib/activate-ai-vault-structured-session-reveal.test.ts
+++ b/src/renderer/src/lib/activate-ai-vault-structured-session-reveal.test.ts
@@ -21,7 +21,7 @@ vi.mock('@/runtime/runtime-rpc-client', () => ({
 }))
 
 vi.mock('./worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: mocks.environmentIdFor
+  runtimeEnvironmentIdOrLocalUnlessTwin: mocks.environmentIdFor
 }))
 
 import { revealStructuredSession } from './activate-ai-vault-structured-session'
diff --git a/src/renderer/src/lib/activate-ai-vault-structured-session.ts b/src/renderer/src/lib/activate-ai-vault-structured-session.ts
index 29013528a19..33a1932697f 100644
--- a/src/renderer/src/lib/activate-ai-vault-structured-session.ts
+++ b/src/renderer/src/lib/activate-ai-vault-structured-session.ts
@@ -4,7 +4,7 @@ import { translate } from '@/i18n/i18n'
 import { activateAndRevealWorktree } from './worktree-activation'
 import { activateStructuredAgentSessionById } from './structured-agent-session-tab-activation'
 import { useAppStore } from '@/store'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from './worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from './worktree-runtime-owner'
 import { callRuntimeRpc, runtimeEnvironmentSupportsCapability } from '@/runtime/runtime-rpc-client'
 import type { RuntimeClientTarget } from '../../../shared/runtime-client-target'
 import { runtimeTargetForOwnerEnvironment } from '@/runtime/runtime-client-target'
@@ -105,10 +105,7 @@ export async function activateAiVaultStructuredSession(
   const hostKey = executionHostIdForStructuredTarget(
     target ??
       runtimeTargetForOwnerEnvironment(
-        runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
-          useAppStore.getState(),
-          structured.workspaceId
-        )
+        runtimeEnvironmentIdOrLocalUnlessTwin(useAppStore.getState(), structured.workspaceId)
       )
   )
   const key = `${hostKey}\0${structured.workspaceId}\0${structured.sessionId}`
@@ -199,7 +196,7 @@ export async function revealStructuredSession(target: {
   const host =
     target.target ??
     runtimeTargetForOwnerEnvironment(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(useAppStore.getState(), target.worktreeId)
+      runtimeEnvironmentIdOrLocalUnlessTwin(useAppStore.getState(), target.worktreeId)
     )
   // Negotiated against the host that will answer this call, not the local one: a paired host runs
   // its own build, and its method-not-found is indistinguishable from a refusal we should surface.
@@ -259,9 +256,7 @@ async function refreshStructuredSessionTabs(
   const state = useAppStore.getState()
   const host =
     target ??
-    runtimeTargetForOwnerEnvironment(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId)
-    )
+    runtimeTargetForOwnerEnvironment(runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId))
   if (host.kind === 'local') {
     await withStructuredSessionRestoreTimeout(refreshLocalStructuredSessionWorktreeTabs(worktreeId))
     return
diff --git a/src/renderer/src/lib/active-agent-note-send.ts b/src/renderer/src/lib/active-agent-note-send.ts
index 7ac569f10f6..ffd4807da15 100644
--- a/src/renderer/src/lib/active-agent-note-send.ts
+++ b/src/renderer/src/lib/active-agent-note-send.ts
@@ -3,7 +3,7 @@ import { runtimeTargetForOwnerEnvironment } from '@/runtime/runtime-client-targe
 import type { RuntimeClientTarget } from '../../../shared/runtime-client-target'
 import { useAppStore } from '@/store'
 import { callRuntimeRpc } from '@/runtime/runtime-rpc-client'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { findActiveRuntimeTerminal, getActiveTerminalNoteTarget } from './active-agent-note-target'
 import type { ActiveTerminalNoteTarget } from './active-agent-note-target'
 import type { ActiveAgentNotesSendResult } from './active-agent-note-send-result'
@@ -74,7 +74,7 @@ async function sendNotesToActiveAgentSessionInternal({
     return reportNoteSendFailure({ status: 'no-active-terminal', code: 'no-note-target' }, null)
   }
   const runtimeTarget = runtimeTargetForOwnerEnvironment(
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId)
+    runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)
   )
   const terminal = await findActiveRuntimeTerminal(
     runtimeTarget,
diff --git a/src/renderer/src/lib/active-agent-note-target.ts b/src/renderer/src/lib/active-agent-note-target.ts
index bf8ca66b0b3..f492a55f2c9 100644
--- a/src/renderer/src/lib/active-agent-note-target.ts
+++ b/src/renderer/src/lib/active-agent-note-target.ts
@@ -8,7 +8,7 @@ import {
 } from '../../../shared/agent-status-types'
 import type { AppState } from '@/store/types'
 import { callRuntimeRpc } from '@/runtime/runtime-rpc-client'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import type { WorktreeRuntimeOwnerState } from '@/lib/worktree-runtime-owner-state'
 import { toRuntimeWorktreeSelector } from '@/runtime/runtime-worktree-selector'
 import { isTerminalLeafId, makePaneKey } from '../../../shared/stable-pane-id'
@@ -122,7 +122,7 @@ export function getActiveAgentRuntimeProbeDescriptor(
   // Route by the worktree's owner host so the probe targets the host that runs
   // this worktree's agent terminal, not the focused runtime.
   const runtimeTarget = runtimeTargetForOwnerEnvironment(
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId)
+    runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)
   )
   const runtimeKey =
     runtimeTarget.kind === 'environment' ? `env:${runtimeTarget.environmentId}` : 'local'
diff --git a/src/renderer/src/lib/agent-launch-caller-permissions.test.ts b/src/renderer/src/lib/agent-launch-caller-permissions.test.ts
index 1cc03e20753..0af713a2d0b 100644
--- a/src/renderer/src/lib/agent-launch-caller-permissions.test.ts
+++ b/src/renderer/src/lib/agent-launch-caller-permissions.test.ts
@@ -30,7 +30,7 @@ vi.mock('@/runtime/web-runtime-session-environment', () => ({
 }))
 vi.mock('@/lib/worktree-runtime-owner', () => ({
   getExecutionHostIdForWorktree: () => 'local',
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => null
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => null
 }))
 vi.mock('@/components/tab-bar/reconcile-order', () => ({
   reconcileTabOrder: (_stored: unknown, terminalIds: string[]) => terminalIds
diff --git a/src/renderer/src/lib/agent-launch-caller-placement.test.ts b/src/renderer/src/lib/agent-launch-caller-placement.test.ts
index 750367973c1..7f6409e3dd5 100644
--- a/src/renderer/src/lib/agent-launch-caller-placement.test.ts
+++ b/src/renderer/src/lib/agent-launch-caller-placement.test.ts
@@ -31,7 +31,7 @@ vi.mock('@/runtime/web-runtime-session-environment', () => ({
 }))
 vi.mock('@/lib/worktree-runtime-owner', () => ({
   getExecutionHostIdForWorktree: () => 'local',
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => null
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => null
 }))
 vi.mock('@/components/tab-bar/reconcile-order', () => ({
   reconcileTabOrder: (_stored: unknown, terminalIds: string[]) => terminalIds
diff --git a/src/renderer/src/lib/agent-launch-caller-prompt-transport.test.ts b/src/renderer/src/lib/agent-launch-caller-prompt-transport.test.ts
index dc0b109115e..6a9abcfecca 100644
--- a/src/renderer/src/lib/agent-launch-caller-prompt-transport.test.ts
+++ b/src/renderer/src/lib/agent-launch-caller-prompt-transport.test.ts
@@ -32,7 +32,7 @@ vi.mock('@/runtime/web-runtime-session-environment', () => ({
 }))
 vi.mock('@/lib/worktree-runtime-owner', () => ({
   getExecutionHostIdForWorktree: () => 'local',
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => null
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => null
 }))
 vi.mock('@/components/tab-bar/reconcile-order', () => ({
   reconcileTabOrder: (_stored: unknown, terminalIds: string[]) => terminalIds
diff --git a/src/renderer/src/lib/agent-launch-caller-routing.test.ts b/src/renderer/src/lib/agent-launch-caller-routing.test.ts
index 8dcac1b7e97..af6282f07a7 100644
--- a/src/renderer/src/lib/agent-launch-caller-routing.test.ts
+++ b/src/renderer/src/lib/agent-launch-caller-routing.test.ts
@@ -37,7 +37,7 @@ vi.mock('@/runtime/web-runtime-session-environment', () => ({
 }))
 vi.mock('@/lib/worktree-runtime-owner', () => ({
   getExecutionHostIdForWorktree: () => mockExecutionHostId(),
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => 'web-runtime'
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => 'web-runtime'
 }))
 vi.mock('@/lib/launch-agent-web-host-tab', () => ({
   launchAgentInWebHostTab: mockLaunchAgentInWebHostTab
diff --git a/src/renderer/src/lib/client-creation-action-policy.ts b/src/renderer/src/lib/client-creation-action-policy.ts
index a73564a2908..0979b4c1acd 100644
--- a/src/renderer/src/lib/client-creation-action-policy.ts
+++ b/src/renderer/src/lib/client-creation-action-policy.ts
@@ -3,7 +3,7 @@ import { BROWSER_SCREENCAST_RUNTIME_CAPABILITY } from '../../../shared/protocol-
 import type { RuntimeStatus } from '../../../shared/runtime-types'
 import type { AppState } from '@/store/types'
 import { isPairedWebClientWindow } from './desktop-window-chrome'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from './worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from './worktree-runtime-owner'
 import { expectsBrowserClientHosting } from '../../../shared/browser-client-hosting-eligibility'
 import {
   getOrcadSshDeployment,
@@ -77,7 +77,7 @@ export function getClientCreationActionPolicy(
   const runtimeEnvironmentId = floatingWorkspace
     ? null
     : worktreeId
-      ? runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId)
+      ? runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)
       : (state.settings?.activeRuntimeEnvironmentId?.trim() ?? null)
   const runtimeStatus = runtimeEnvironmentId
     ? (state.runtimeStatusByEnvironmentId?.get(runtimeEnvironmentId)?.status ?? null)
diff --git a/src/renderer/src/lib/doc-preview-grants.test.ts b/src/renderer/src/lib/doc-preview-grants.test.ts
index 308760c184d..b53ff82a799 100644
--- a/src/renderer/src/lib/doc-preview-grants.test.ts
+++ b/src/renderer/src/lib/doc-preview-grants.test.ts
@@ -12,8 +12,7 @@ vi.mock('@/lib/connection-owner-resolution', () => ({
   getConnectionIdForFileFromState: () => mocks.connectionId
 }))
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () =>
-    mocks.ambiguous ? null : mocks.environmentId
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => (mocks.ambiguous ? null : mocks.environmentId)
 }))
 
 import {
diff --git a/src/renderer/src/lib/doc-preview-grants.ts b/src/renderer/src/lib/doc-preview-grants.ts
index 5129830f3fd..86aa2296c13 100644
--- a/src/renderer/src/lib/doc-preview-grants.ts
+++ b/src/renderer/src/lib/doc-preview-grants.ts
@@ -1,7 +1,7 @@
 import type { DocPreviewGrantRequest } from '../../../preload/api/doc-preview-api'
 import { basename, dirname, getRelativePathInsideRoot } from '@/lib/path'
 import { getConnectionIdForFileFromState } from '@/lib/connection-owner-resolution'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { toRuntimeWorktreeSelector } from '@/runtime/runtime-worktree-selector'
 import { chatScratchFileAddress } from '@/runtime/runtime-chat-scratch-file-address'
 import type { AppState } from '@/store/types'
@@ -44,7 +44,7 @@ export function buildDocPreviewGrantRequest(
     return { owner: { kind: 'ssh', connectionId }, requestBase, root, entryRelativePath }
   }
   // Why: a twin names no server to mint against, so it gets no grant.
-  const environmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId)
+  const environmentId = runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)
   // Outside the workspace, a chat's scratch folder stands in for it: its host serves it as a root.
   const base =
     worktreeRoot && worktreeRelativePath
diff --git a/src/renderer/src/lib/execute-open-editor-path-move.ts b/src/renderer/src/lib/execute-open-editor-path-move.ts
index 703a1cf14c7..d7f4c453650 100644
--- a/src/renderer/src/lib/execute-open-editor-path-move.ts
+++ b/src/renderer/src/lib/execute-open-editor-path-move.ts
@@ -12,7 +12,7 @@ import {
 } from '@/lib/remap-open-editor-tabs-for-path-change'
 import { verifyLatchedMoveDestinations } from '@/hooks/useEditorExternalWatch'
 import { notifyHostOfMirroredEditorClose } from '@/runtime/close-mirrored-editor-tab'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { editorMoveOwnerFromContext, isOpenFileOnMoveOwner } from '@/lib/open-editor-move-owner'
 import { documentFolderAccess } from '@/lib/local-file-access'
 import { contentRekeyOutcome } from '@/runtime/layout-owner-content-rekeys'
@@ -55,7 +55,7 @@ export async function executeOpenEditorPathMove(args: {
   const addScope = (wtId: string, owner: string | null): void => {
     scopes.set(`${wtId}::${owner ?? 'local'}`, { worktreeId: wtId, owner })
   }
-  addScope(worktreeId, runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(moveState, worktreeId))
+  addScope(worktreeId, runtimeEnvironmentIdOrLocalUnlessTwin(moveState, worktreeId))
   for (const f of affected) {
     addScope(f.worktreeId, f.runtimeEnvironmentId?.trim() || null)
   }
diff --git a/src/renderer/src/lib/execution-host-facts.ts b/src/renderer/src/lib/execution-host-facts.ts
index 7836e9db404..2096a7d1c57 100644
--- a/src/renderer/src/lib/execution-host-facts.ts
+++ b/src/renderer/src/lib/execution-host-facts.ts
@@ -14,7 +14,7 @@ import { getLocalProjectExecutionRuntimeContext } from './local-preflight-contex
 import { CLIENT_PLATFORM } from './new-workspace'
 import {
   getExecutionHostIdForWorktree,
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin
+  runtimeEnvironmentIdOrLocalUnlessTwin
 } from './worktree-runtime-owner'
 
 /**
@@ -148,9 +148,7 @@ export function resolveWorktreeExecutionHostPlatform(
     nestedSshTargetId:
       host?.kind === 'runtime' ? (getConnectionIdFromState(state, worktreeId) ?? null) : null,
     sshOwnerEnvironmentId:
-      host?.kind === 'ssh'
-        ? runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId)
-        : null,
+      host?.kind === 'ssh' ? runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId) : null,
     workspacePath,
     projectRuntime: () => getLocalProjectExecutionRuntimeContext(state, worktreeId)
   })
diff --git a/src/renderer/src/lib/file-preview-action-visibility.test.tsx b/src/renderer/src/lib/file-preview-action-visibility.test.tsx
index e393b624de8..20feffe9508 100644
--- a/src/renderer/src/lib/file-preview-action-visibility.test.tsx
+++ b/src/renderer/src/lib/file-preview-action-visibility.test.tsx
@@ -18,7 +18,7 @@ vi.mock('@/lib/client-creation-action-policy', () => ({
   getClientCreationActionPolicy: () => ({ 'managed-browser': mocks.browserAvailability })
 }))
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => mocks.environmentId
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => mocks.environmentId
 }))
 
 const storeState = {
diff --git a/src/renderer/src/lib/file-preview.test.ts b/src/renderer/src/lib/file-preview.test.ts
index fb5e2b3fef8..02fe5d55cac 100644
--- a/src/renderer/src/lib/file-preview.test.ts
+++ b/src/renderer/src/lib/file-preview.test.ts
@@ -52,7 +52,7 @@ vi.mock('@/lib/client-creation-action-policy', () => ({
 }))
 
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => mocks.environmentId
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => mocks.environmentId
 }))
 
 vi.mock('@/store', () => ({
diff --git a/src/renderer/src/lib/file-preview.ts b/src/renderer/src/lib/file-preview.ts
index 8735fc98d94..45029639a2d 100644
--- a/src/renderer/src/lib/file-preview.ts
+++ b/src/renderer/src/lib/file-preview.ts
@@ -7,7 +7,7 @@ import { useShallow } from 'zustand/react/shallow'
 import { basename, getRelativePathInsideRoot } from '@/lib/path'
 import { getConnectionIdForFileFromState } from '@/lib/connection-owner-resolution'
 import { activateBrowserWorkspaceTab } from '@/lib/browser-workspace-tab-activation'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { isTwinWorkspace } from '@/lib/resolve-owner'
 import {
   REMOTE_FILE_BROWSER_UNSUPPORTED_MESSAGE,
@@ -99,7 +99,7 @@ export function getWorkspaceFilePreviewPlan(
   }
   // Why: the doc preview needs no browser at all, so a paired runtime without the
   // screencast capability still previews documents.
-  if (runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId)) {
+  if (runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)) {
     const worktreeRoot = state.getKnownWorktreeById(worktreeId)?.path ?? null
     const outsideWorktree = worktreeRoot && !getRelativePathInsideRoot(filePath, worktreeRoot)
     // Why: the host's files.read is worktree-scoped (plus chat scratch folders, served by path), so
@@ -140,7 +140,7 @@ export function useWorkspaceFileBrowserActionPredicate(
         ? getClientCreationActionPolicy(state, worktreeId)['managed-browser'].state
         : null,
       runtimeEnvironmentId: worktreeId
-        ? runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId)
+        ? runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)
         : null,
       folderWorkspaces: selectFolderWorkspaces(state),
       projectGroups: state.projectGroups,
@@ -292,7 +292,7 @@ export function openFilePreviewToSide(params: {
 
   // Why the unfocused split on a paired workspace: the preview opens in the background, and a host
   // snapshot reads an activated empty group as a terminal pane.
-  const activate = !runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId)
+  const activate = !runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)
   const placement = existingSibling
     ? { targetGroupId: existingSibling }
     : { split: { sourceGroupId, splitDirection: 'right' as const, activate } }
diff --git a/src/renderer/src/lib/launch-agent-background-session.ts b/src/renderer/src/lib/launch-agent-background-session.ts
index 0cd9c1277ca..21ff60be960 100644
--- a/src/renderer/src/lib/launch-agent-background-session.ts
+++ b/src/renderer/src/lib/launch-agent-background-session.ts
@@ -19,7 +19,7 @@ import {
 } from '@/components/terminal-pane/pty-dispatcher'
 import { subscribeToPtyData } from '@/components/terminal-pane/pty-data-sidecar-subscriptions'
 import { callRuntimeRpc } from '@/runtime/runtime-rpc-client'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { retireProvider } from '@/lib/retire-unowned-background-terminal'
 import { createRuntimeAgentBackgroundTerminal } from '@/lib/runtime-agent-background-create'
 import { subscribeToRuntimeTerminalData } from '@/runtime/runtime-terminal-stream'
@@ -57,7 +57,7 @@ export async function launchAgentBackgroundSession(
   const { platform: launchPlatform, isRemote, isLocalHost } = launchHost
   // Route by the worktree's owner host, not the focused runtime.
   const runtimeTarget = runtimeTargetForOwnerEnvironment(
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(store, worktreeId)
+    runtimeEnvironmentIdOrLocalUnlessTwin(store, worktreeId)
   )
   if (hasExtraAgentArgs(args.extraAgentArgs) && runtimeTarget.kind === 'environment') {
     // Why: that server rebuilds the command from its own settings and would drop the extras.
diff --git a/src/renderer/src/lib/launch-agent-in-new-tab-cwd.test.ts b/src/renderer/src/lib/launch-agent-in-new-tab-cwd.test.ts
index 7b3620e5be0..b07c2a5aacc 100644
--- a/src/renderer/src/lib/launch-agent-in-new-tab-cwd.test.ts
+++ b/src/renderer/src/lib/launch-agent-in-new-tab-cwd.test.ts
@@ -44,7 +44,7 @@ vi.mock('@/runtime/web-runtime-session-environment', () => ({
 
 vi.mock('@/lib/worktree-runtime-owner', () => ({
   getExecutionHostIdForWorktree: () => 'local',
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => 'web-runtime'
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => 'web-runtime'
 }))
 
 vi.mock('@/lib/launch-agent-web-host-tab', () => ({
diff --git a/src/renderer/src/lib/launch-agent-in-new-tab-placement.test.ts b/src/renderer/src/lib/launch-agent-in-new-tab-placement.test.ts
index d083aab34d2..249149b5a9b 100644
--- a/src/renderer/src/lib/launch-agent-in-new-tab-placement.test.ts
+++ b/src/renderer/src/lib/launch-agent-in-new-tab-placement.test.ts
@@ -69,7 +69,7 @@ vi.mock('@/runtime/web-runtime-session-environment', () => ({
 
 vi.mock('@/lib/worktree-runtime-owner', () => ({
   getExecutionHostIdForWorktree: () => 'local',
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => null
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => null
 }))
 
 vi.mock('@/components/tab-bar/reconcile-order', () => ({
diff --git a/src/renderer/src/lib/launch-agent-in-new-tab.ts b/src/renderer/src/lib/launch-agent-in-new-tab.ts
index 8e2a5ad6b0f..63a755f643d 100644
--- a/src/renderer/src/lib/launch-agent-in-new-tab.ts
+++ b/src/renderer/src/lib/launch-agent-in-new-tab.ts
@@ -13,7 +13,7 @@ import {
   launchNewTabPromptThroughHost,
   newTabPromptLaunchesThroughHost
 } from '@/lib/launch-agent-new-tab-host-route'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { isWebRuntimeSessionActive } from '@/runtime/web-runtime-session-environment'
 import { launchAgentInWebHostTab } from '@/lib/launch-agent-web-host-tab'
 import {
@@ -222,7 +222,7 @@ function launchAgentInNewTabInternal(args: LaunchAgentInNewTabArgs): LaunchAgent
   }
 
   args.focusIntent?.cancel()
-  const runtimeEnvironmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(store, worktreeId)
+  const runtimeEnvironmentId = runtimeEnvironmentIdOrLocalUnlessTwin(store, worktreeId)
   if (isWebRuntimeSessionActive(runtimeEnvironmentId)) {
     if (beforeSurfaceOpen?.({ kind: 'host-published' }) === false) {
       return null
diff --git a/src/renderer/src/lib/launch-agent-structured-chat-guard.test.ts b/src/renderer/src/lib/launch-agent-structured-chat-guard.test.ts
index 10983d53a64..c1cbba55acf 100644
--- a/src/renderer/src/lib/launch-agent-structured-chat-guard.test.ts
+++ b/src/renderer/src/lib/launch-agent-structured-chat-guard.test.ts
@@ -180,7 +180,7 @@ vi.mock('@/runtime/local-runtime-capabilities', () => ({
 vi.mock('@/lib/worktree-runtime-owner', () => ({
   getExecutionHostIdForWorktree: () =>
     store.repos[0]?.connectionId ? `ssh:${store.repos[0].connectionId}` : 'local',
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => null
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => null
 }))
 vi.mock('@/runtime/structured-agent-session-client', () => ({
   callStructuredAgentSession: (target: unknown, method: string, params: unknown) =>
diff --git a/src/renderer/src/lib/launch-ai-vault-session.test.ts b/src/renderer/src/lib/launch-ai-vault-session.test.ts
index 5e8ed72b57f..967d1f92a44 100644
--- a/src/renderer/src/lib/launch-ai-vault-session.test.ts
+++ b/src/renderer/src/lib/launch-ai-vault-session.test.ts
@@ -11,7 +11,7 @@ const mockSetActiveTabType = vi.fn()
 const mockSetTabBarOrder = vi.fn()
 const runtimeMocks = vi.hoisted(() => ({
   createWebRuntimeSessionTerminal: vi.fn(),
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: vi.fn<() => string | null>(() => null),
+  runtimeEnvironmentIdOrLocalUnlessTwin: vi.fn<() => string | null>(() => null),
   isWebRuntimeSessionActive: vi.fn(() => false)
 }))
 
@@ -47,8 +47,7 @@ vi.mock('@/lib/telemetry', () => ({
 }))
 
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin:
-    runtimeMocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin
+  runtimeEnvironmentIdOrLocalUnlessTwin: runtimeMocks.runtimeEnvironmentIdOrLocalUnlessTwin
 }))
 
 vi.mock('@/runtime/web-runtime-terminal-creation', () => ({
@@ -63,7 +62,7 @@ import { launchAiVaultSessionInNewTab } from './launch-ai-vault-session'
 describe('launchAiVaultSessionInNewTab', () => {
   beforeEach(() => {
     vi.clearAllMocks()
-    runtimeMocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin.mockReturnValue(null)
+    runtimeMocks.runtimeEnvironmentIdOrLocalUnlessTwin.mockReturnValue(null)
     runtimeMocks.isWebRuntimeSessionActive.mockReturnValue(false)
     runtimeMocks.createWebRuntimeSessionTerminal.mockResolvedValue({ status: 'created' })
     mockState.tabsByWorktree = {}
@@ -159,7 +158,7 @@ describe('launchAiVaultSessionInNewTab', () => {
   })
 
   it('creates runtime-hosted resume terminals through the paired host', async () => {
-    runtimeMocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin.mockReturnValue('env-1')
+    runtimeMocks.runtimeEnvironmentIdOrLocalUnlessTwin.mockReturnValue('env-1')
     runtimeMocks.isWebRuntimeSessionActive.mockReturnValue(true)
 
     const result = launchAiVaultSessionInNewTab({
@@ -211,7 +210,7 @@ describe('launchAiVaultSessionInNewTab', () => {
 
   // #22791: a drop on a pane edge in a paired-runtime worktree opened a tab instead of a split.
   it('splits the pane before a runtime-hosted resume and targets the new group', async () => {
-    runtimeMocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin.mockReturnValue('env-1')
+    runtimeMocks.runtimeEnvironmentIdOrLocalUnlessTwin.mockReturnValue('env-1')
     runtimeMocks.isWebRuntimeSessionActive.mockReturnValue(true)
 
     const result = launchAiVaultSessionInNewTab({
@@ -234,7 +233,7 @@ describe('launchAiVaultSessionInNewTab', () => {
   })
 
   it('removes the still-empty split group when the runtime create does not succeed', async () => {
-    runtimeMocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin.mockReturnValue('env-1')
+    runtimeMocks.runtimeEnvironmentIdOrLocalUnlessTwin.mockReturnValue('env-1')
     runtimeMocks.isWebRuntimeSessionActive.mockReturnValue(true)
     runtimeMocks.createWebRuntimeSessionTerminal.mockResolvedValue({
       status: 'failed',
diff --git a/src/renderer/src/lib/launch-ai-vault-session.ts b/src/renderer/src/lib/launch-ai-vault-session.ts
index b630483e51a..0827b314878 100644
--- a/src/renderer/src/lib/launch-ai-vault-session.ts
+++ b/src/renderer/src/lib/launch-ai-vault-session.ts
@@ -1,7 +1,7 @@
 import { useAppStore } from '@/store'
 import { persistAgentLaunchTabOrder } from '@/lib/launch-agent-tab-order'
 import { tuiAgentToAgentKind } from '@/lib/telemetry'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { createWebRuntimeSessionTerminal } from '@/runtime/web-runtime-terminal-creation'
 import { isWebRuntimeSessionActive } from '@/runtime/web-runtime-session-environment'
 import type { AiVaultAgent } from '../../../shared/ai-vault-types'
@@ -34,10 +34,7 @@ export function launchAiVaultSessionInNewTab(args: {
     args.splitDirection && args.targetGroupId
       ? { sourceGroupId: args.targetGroupId, splitDirection: args.splitDirection }
       : undefined
-  const runtimeEnvironmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
-    store,
-    args.worktreeId
-  )
+  const runtimeEnvironmentId = runtimeEnvironmentIdOrLocalUnlessTwin(store, args.worktreeId)
   if (isWebRuntimeSessionActive(runtimeEnvironmentId)) {
     // Why an empty group first: the paired host creates the tab after a round trip.
     const splitGroupId = split
diff --git a/src/renderer/src/lib/paired-web-client-host.test.ts b/src/renderer/src/lib/paired-web-client-host.test.ts
index 8ccabd33fc3..ec3ddb05e34 100644
--- a/src/renderer/src/lib/paired-web-client-host.test.ts
+++ b/src/renderer/src/lib/paired-web-client-host.test.ts
@@ -1,5 +1,5 @@
 import { afterEach, describe, expect, it, vi } from 'vitest'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from './worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from './worktree-runtime-owner'
 import type { WorktreeRuntimeOwnerState } from './worktree-runtime-owner-state'
 import { resolveWorktreeOperationRoute } from './worktree-operation-route'
 import { resolveTerminalHostOwnership } from './terminal-worktree-route'
@@ -42,7 +42,7 @@ describe('a paired web client routes every owner through its server (#9047)', ()
       webState({ activeWorktreeId: WT, activeWorkspaceExecutionHostId: 'local' }),
       webState(UNSTAMPED_LOCAL_ROW)
     ]) {
-      expect(runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, WT)).toBe(ENV)
+      expect(runtimeEnvironmentIdOrLocalUnlessTwin(state, WT)).toBe(ENV)
       expect(resolveTerminalHostOwnership(state, WT, 'spawn')).toEqual({
         kind: 'runtime',
         runtimeEnvironmentId: ENV
@@ -64,9 +64,9 @@ describe('a paired web client routes every owner through its server (#9047)', ()
         { id: 'folder-1', projectGroupId: 'group-1', executionHostId: 'local', connectionId: null }
       ]
     })
-    expect(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(folderState, folderWorkspaceKey('folder-1'))
-    ).toBe(ENV)
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(folderState, folderWorkspaceKey('folder-1'))).toBe(
+      ENV
+    )
   })
 
   it('keeps an SSH target as the place and the server as the transport', () => {
@@ -88,12 +88,12 @@ describe('a paired web client routes every owner through its server (#9047)', ()
         ]
       }
     })
-    expect(runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, WT)).toBeNull()
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(state, WT)).toBeNull()
   })
 
   it('leaves a desktop window local workspace on this computer', () => {
     const state = webState(UNSTAMPED_LOCAL_ROW)
-    expect(runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, WT)).toBeNull()
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(state, WT)).toBeNull()
     expect(resolveTerminalHostOwnership(state, WT, 'spawn').kind).toBe('local-or-ssh')
   })
 })
diff --git a/src/renderer/src/lib/resolve-owner-acceptance.test-fixture.ts b/src/renderer/src/lib/resolve-owner-acceptance.test-fixture.ts
index b36ba137248..92779b3574b 100644
--- a/src/renderer/src/lib/resolve-owner-acceptance.test-fixture.ts
+++ b/src/renderer/src/lib/resolve-owner-acceptance.test-fixture.ts
@@ -1,5 +1,5 @@
-/** Hand-reviewed owner per matrix case for `resolveOwnerWithLegacyFallback` (round-3 design §5). */
-export const LEGACY_FALLBACK_OWNER_ACCEPTANCE: Record<string, string> = {
+/** Hand-reviewed owner per matrix case for `resolveOwnerOrLocal` (round-3 design §5). */
+export const OWNER_OR_LOCAL_ACCEPTANCE: Record<string, string> = {
   'focused | global-floating-terminal': 'self@local',
   'focused | local-repo::wt': 'self@local',
   'focused | legacy-repo::wt': 'self@local',
diff --git a/src/renderer/src/lib/resolve-owner-acceptance.test.ts b/src/renderer/src/lib/resolve-owner-acceptance.test.ts
index 4678ac46eda..4a5fd92a990 100644
--- a/src/renderer/src/lib/resolve-owner-acceptance.test.ts
+++ b/src/renderer/src/lib/resolve-owner-acceptance.test.ts
@@ -1,9 +1,9 @@
 import { describe, expect, it } from 'vitest'
 import type { ExecutionHostOwnerMatch } from '../../../shared/worktree-execution-host-resolution'
 import type { HostAuthority } from '../../../shared/host-authority'
-import { resolveOwnerWithLegacyFallback } from './worktree-runtime-owner'
+import { resolveOwnerOrLocal } from './worktree-runtime-owner'
 import { OWNER_RESOLUTION_CASES } from './runtime-owner-alias-matrix.test-fixture'
-import { LEGACY_FALLBACK_OWNER_ACCEPTANCE } from './resolve-owner-acceptance.test-fixture'
+import { OWNER_OR_LOCAL_ACCEPTANCE } from './resolve-owner-acceptance.test-fixture'
 import { LEGACY_RUNTIME_OWNER_GOLDEN } from './legacy-runtime-owner-answers.test-fixture'
 import type { WorktreeRuntimeOwnerState } from './worktree-runtime-owner-state'
 
@@ -33,20 +33,20 @@ const DELIBERATE_CHANGES: Record<string, string> = {
   'folder:missing-folder': 'same'
 }
 
-describe('resolveOwnerWithLegacyFallback acceptance (round-3 design §5)', () => {
+describe('resolveOwnerOrLocal acceptance (round-3 design §5)', () => {
   it('pins the owner of every matrix case', () => {
     const actual = Object.fromEntries(
       casesWithIds.map((c) => [
         c.name,
-        describeMatch(resolveOwnerWithLegacyFallback(c.state, { workspaceId: c.worktreeId }))
+        describeMatch(resolveOwnerOrLocal(c.state, { workspaceId: c.worktreeId }))
       ])
     )
-    expect(actual).toEqual(LEGACY_FALLBACK_OWNER_ACCEPTANCE)
+    expect(actual).toEqual(OWNER_OR_LOCAL_ACCEPTANCE)
   })
 
   it('differs from the deprecated resolver only in the deliberate cases', () => {
     const changed = casesWithIds.filter((c) => {
-      const owner = resolveOwnerWithLegacyFallback(c.state, { workspaceId: c.worktreeId })
+      const owner = resolveOwnerOrLocal(c.state, { workspaceId: c.worktreeId })
       const environmentId =
         owner.kind === 'resolved' && owner.owner.endpoint.kind === 'environment'
           ? owner.owner.endpoint.environmentId
@@ -64,13 +64,13 @@ describe('resolveOwnerWithLegacyFallback acceptance (round-3 design §5)', () =>
   })
 })
 
-describe('resolveOwnerWithLegacyFallback probes', () => {
+describe('resolveOwnerOrLocal probes', () => {
   const base = OWNER_RESOLUTION_CASES.find((c) => c.name === 'focused | stale-hub-repo::wt')!.state
   const single = OWNER_RESOLUTION_CASES.find(
     (c) => c.name === 'single focus | legacy-repo::wt'
   )!.state
   const ownerOf = (state: WorktreeRuntimeOwnerState, workspaceId: string, hostId?: 'local') =>
-    describeMatch(resolveOwnerWithLegacyFallback(state, { workspaceId, hostId }))
+    describeMatch(resolveOwnerOrLocal(state, { workspaceId, hostId }))
 
   it('reads a genuine twin as ambiguous', () => {
     const withDirect = {
diff --git a/src/renderer/src/lib/structured-agent-session-tab-activation.test.ts b/src/renderer/src/lib/structured-agent-session-tab-activation.test.ts
index 6cc3a85abb6..d07effc7414 100644
--- a/src/renderer/src/lib/structured-agent-session-tab-activation.test.ts
+++ b/src/renderer/src/lib/structured-agent-session-tab-activation.test.ts
@@ -19,7 +19,7 @@ vi.mock('@/components/native-chat/use-native-chat-composer-reveal-focus', () =>
 }))
 
 vi.mock('./worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => 'env-1'
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => 'env-1'
 }))
 
 vi.mock('@/runtime/runtime-rpc-client', () => ({ callRuntimeRpc: mocks.callRuntimeRpc }))
diff --git a/src/renderer/src/lib/structured-agent-session-tab-activation.ts b/src/renderer/src/lib/structured-agent-session-tab-activation.ts
index c14d0525e05..317e37a7a63 100644
--- a/src/renderer/src/lib/structured-agent-session-tab-activation.ts
+++ b/src/renderer/src/lib/structured-agent-session-tab-activation.ts
@@ -1,4 +1,4 @@
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from './worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from './worktree-runtime-owner'
 import { requestNativeChatComposerFocus } from '@/components/native-chat/use-native-chat-composer-reveal-focus'
 import { useAppStore } from '@/store'
 import { callRuntimeRpc } from '@/runtime/runtime-rpc-client'
@@ -49,7 +49,7 @@ export function activateStructuredAgentSessionTab(args: {
   state.activateTab(tab.id, { worktreeId: args.worktreeId })
   state.setActiveTabType('agent-session', args.worktreeId)
   requestNativeChatComposerFocus(tab.id)
-  const environmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, args.worktreeId)
+  const environmentId = runtimeEnvironmentIdOrLocalUnlessTwin(state, args.worktreeId)
   void callRuntimeRpc(
     args.target ?? runtimeTargetForOwnerEnvironment(environmentId),
     'session.tabs.activate',
diff --git a/src/renderer/src/lib/tab-number-shortcuts.ts b/src/renderer/src/lib/tab-number-shortcuts.ts
index 17562c906cf..75905046bd4 100644
--- a/src/renderer/src/lib/tab-number-shortcuts.ts
+++ b/src/renderer/src/lib/tab-number-shortcuts.ts
@@ -1,7 +1,7 @@
 import { focusTerminalTabSurface } from '@/lib/focus-terminal-tab-surface'
 import { useAppStore } from '@/store'
 import type { AppState } from '@/store/types'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { dedupeTabOrder } from '../../../shared/workspace-layout/tab-order'
 import type { Tab } from '../../../shared/tab-types'
 import { activateWebRuntimeSessionTab } from '@/runtime/web-runtime-session-tab-lifecycle'
@@ -60,7 +60,7 @@ export function activateTabNumberShortcut(index: number): boolean {
   }
 
   const worktreeId = target.worktreeId
-  const runtimeEnvironmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(store, worktreeId)
+  const runtimeEnvironmentId = runtimeEnvironmentIdOrLocalUnlessTwin(store, worktreeId)
   store.focusGroup(worktreeId, target.groupId)
   store.activateTab(target.id)
 
diff --git a/src/renderer/src/lib/terminal-tab-owner-activation.test.ts b/src/renderer/src/lib/terminal-tab-owner-activation.test.ts
index efe26bb3943..269d85be365 100644
--- a/src/renderer/src/lib/terminal-tab-owner-activation.test.ts
+++ b/src/renderer/src/lib/terminal-tab-owner-activation.test.ts
@@ -2,14 +2,13 @@ import { beforeEach, describe, expect, it, vi } from 'vitest'
 
 const mocks = vi.hoisted(() => ({
   activateWebRuntimeSessionTab: vi.fn(),
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: vi.fn(),
+  runtimeEnvironmentIdOrLocalUnlessTwin: vi.fn(),
   resolveWebSessionVisibleTabId: vi.fn()
 }))
 
 vi.mock('@/store', () => ({ useAppStore: { getState: () => ({}) } }))
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin:
-    mocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin
+  runtimeEnvironmentIdOrLocalUnlessTwin: mocks.runtimeEnvironmentIdOrLocalUnlessTwin
 }))
 vi.mock('@/runtime/web-runtime-session-tab-lifecycle', () => ({
   activateWebRuntimeSessionTab: mocks.activateWebRuntimeSessionTab
@@ -31,12 +30,12 @@ describe('activateTerminalTabOnOwner', () => {
   })
 
   it('tells the paired server that owns the workspace, not the focused one', () => {
-    mocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin.mockReturnValue('env-owner')
+    mocks.runtimeEnvironmentIdOrLocalUnlessTwin.mockReturnValue('env-owner')
     mocks.resolveWebSessionVisibleTabId.mockReturnValue('unified-visible')
 
     activateTerminalTabOnOwner('wt-1', 'web-terminal-host-tab', 'leaf-b')
 
-    expect(mocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin).toHaveBeenCalledWith({}, 'wt-1')
+    expect(mocks.runtimeEnvironmentIdOrLocalUnlessTwin).toHaveBeenCalledWith({}, 'wt-1')
     expect(mocks.activateWebRuntimeSessionTab).toHaveBeenCalledWith({
       worktreeId: 'wt-1',
       tabId: 'web-terminal-host-tab',
@@ -48,7 +47,7 @@ describe('activateTerminalTabOnOwner', () => {
   })
 
   it('makes no owner round trip for a workspace this client runs', () => {
-    mocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin.mockReturnValue(null)
+    mocks.runtimeEnvironmentIdOrLocalUnlessTwin.mockReturnValue(null)
 
     activateTerminalTabOnOwner('wt-local', 'tab-1', null)
 
diff --git a/src/renderer/src/lib/terminal-tab-owner-activation.ts b/src/renderer/src/lib/terminal-tab-owner-activation.ts
index 5bf816fb685..bef6a384018 100644
--- a/src/renderer/src/lib/terminal-tab-owner-activation.ts
+++ b/src/renderer/src/lib/terminal-tab-owner-activation.ts
@@ -1,5 +1,5 @@
 import { useAppStore } from '@/store'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { activateWebRuntimeSessionTab } from '@/runtime/web-runtime-session-tab-lifecycle'
 import { isWebRuntimeSessionActive } from '@/runtime/web-runtime-session-environment'
 import { resolveWebSessionVisibleTabId } from '@/runtime/web-session-focus-intent'
@@ -17,7 +17,7 @@ export function activateTerminalTabOnOwner(
   leafId: string | null
 ): void {
   const state = useAppStore.getState()
-  const environmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId)
+  const environmentId = runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)
   if (!environmentId || !isWebRuntimeSessionActive(environmentId)) {
     return
   }
diff --git a/src/renderer/src/lib/terminal-worktree-route.ts b/src/renderer/src/lib/terminal-worktree-route.ts
index 53160cd7de9..09e81e06a16 100644
--- a/src/renderer/src/lib/terminal-worktree-route.ts
+++ b/src/renderer/src/lib/terminal-worktree-route.ts
@@ -3,7 +3,7 @@ import { isEphemeralSetupTerminalWorktreeId } from '../../../shared/ephemeral-se
 import { parseExecutionHostId } from '../../../shared/execution-host'
 import { parseWorkspaceKey } from '../../../shared/workspace-scope'
 import type { AppState } from '@/store/types'
-import { resolveOwnerWithLegacyFallback } from './worktree-runtime-owner'
+import { resolveOwnerOrLocal } from './worktree-runtime-owner'
 import { namedHostForOwnerRef, runtimeEnvironmentIdUnlessTwin } from './resolve-owner'
 import type { WorktreeRuntimeOwnerState } from './worktree-runtime-owner-state'
 import {
@@ -69,7 +69,7 @@ export function resolveTerminalHostOwnership(
     worktreeId === FLOATING_TERMINAL_WORKTREE_ID ||
     parseWorkspaceKey(worktreeId)?.type === 'folder'
   ) {
-    const owner = resolveOwnerWithLegacyFallback(state, { workspaceId: worktreeId })
+    const owner = resolveOwnerOrLocal(state, { workspaceId: worktreeId })
     if (owner.kind !== 'resolved') {
       // Why: spawn must not pick a twin; a twin's runtime PTYs carry `remote:` ids, so a raw id is
       // local or SSH on either copy.
diff --git a/src/renderer/src/lib/web-runtime-worktree-terminal-after-wake.ts b/src/renderer/src/lib/web-runtime-worktree-terminal-after-wake.ts
index ec3652b8bf7..173ca689f45 100644
--- a/src/renderer/src/lib/web-runtime-worktree-terminal-after-wake.ts
+++ b/src/renderer/src/lib/web-runtime-worktree-terminal-after-wake.ts
@@ -8,7 +8,7 @@ import {
   beginWebRuntimeWakeTerminalRespawn,
   endWebRuntimeWakeTerminalRespawn
 } from '@/runtime/web-runtime-wake-terminal-respawn'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import type { WorktreeStartupPayload } from '@/lib/worktree-startup-payload'
 import type { TuiAgent } from '../../../shared/tui-agent'
 import { toast } from 'sonner'
@@ -35,7 +35,7 @@ export function ensureWebRuntimeWorktreeTerminalAfterWake(
   const runtimeEnvironmentId =
     opts && 'runtimeEnvironmentId' in opts
       ? (opts.runtimeEnvironmentId ?? null)
-      : runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId)
+      : runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)
   if (!runtimeEnvironmentId || !isWebRuntimeSessionActive(runtimeEnvironmentId)) {
     return
   }
diff --git a/src/renderer/src/lib/workspace-file-browser-open-target.test.ts b/src/renderer/src/lib/workspace-file-browser-open-target.test.ts
index 254e4a1a391..76b7d4f2b78 100644
--- a/src/renderer/src/lib/workspace-file-browser-open-target.test.ts
+++ b/src/renderer/src/lib/workspace-file-browser-open-target.test.ts
@@ -13,7 +13,7 @@ const mocks = vi.hoisted(() => ({
 }))
 
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: () => mocks.environmentId
+  runtimeEnvironmentIdOrLocalUnlessTwin: () => mocks.environmentId
 }))
 
 vi.mock('@/store', () => ({
diff --git a/src/renderer/src/lib/workspace-file-browser-open-target.ts b/src/renderer/src/lib/workspace-file-browser-open-target.ts
index 5cf848dd31d..655b8e970c9 100644
--- a/src/renderer/src/lib/workspace-file-browser-open-target.ts
+++ b/src/renderer/src/lib/workspace-file-browser-open-target.ts
@@ -2,7 +2,7 @@ import { absolutePathToFileUri } from '@/components/editor/markdown-internal-lin
 import { getConnectionIdForFile } from '@/lib/connection-context'
 import { basename } from '@/lib/path'
 import { isTwinWorkspace } from '@/lib/resolve-owner'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { useAppStore } from '@/store'
 
 /** Still the answer for flows that need a real `file://` URL (e.g. dropping a file on a browser pane). */
@@ -39,7 +39,7 @@ export function getWorkspaceFileBrowserOpenTarget(params: {
   }
   if (
     getConnectionIdForFile(params.worktreeId, params.filePath) !== null ||
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, params.worktreeId)
+    runtimeEnvironmentIdOrLocalUnlessTwin(state, params.worktreeId)
   ) {
     // Why: Chromium resolves file:// URLs on the local machine. Remote files
     // need an Orca-served URL before the browser can render them correctly.
diff --git a/src/renderer/src/lib/workspace-tab-palette-activation.test.ts b/src/renderer/src/lib/workspace-tab-palette-activation.test.ts
index 1c98f3f261b..58135459fd5 100644
--- a/src/renderer/src/lib/workspace-tab-palette-activation.test.ts
+++ b/src/renderer/src/lib/workspace-tab-palette-activation.test.ts
@@ -63,7 +63,7 @@ const mocks = vi.hoisted(() => {
     activateAndRevealWorkspace: vi.fn(),
     activateWebRuntimeSessionTab: vi.fn(),
     focusTerminalTabSurface: vi.fn(),
-    runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: vi.fn(),
+    runtimeEnvironmentIdOrLocalUnlessTwin: vi.fn(),
     isWebRuntimeSessionActive: vi.fn()
   }
 })
@@ -79,8 +79,7 @@ vi.mock('@/lib/focus-terminal-tab-surface', () => ({
 }))
 
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin:
-    mocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin
+  runtimeEnvironmentIdOrLocalUnlessTwin: mocks.runtimeEnvironmentIdOrLocalUnlessTwin
 }))
 
 vi.mock('@/runtime/web-runtime-session-tab-lifecycle', () => ({
@@ -173,7 +172,7 @@ describe('activateWorkspaceTabPaletteResult', () => {
         .find((worktree) => worktree.id === worktreeId)
     )
     mocks.activateAndRevealWorkspace.mockReturnValue(true)
-    mocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin.mockReturnValue('runtime-1')
+    mocks.runtimeEnvironmentIdOrLocalUnlessTwin.mockReturnValue('runtime-1')
     mocks.isWebRuntimeSessionActive.mockReturnValue(false)
   })
 
diff --git a/src/renderer/src/lib/workspace-tab-palette-activation.ts b/src/renderer/src/lib/workspace-tab-palette-activation.ts
index 9a3dc6d92fd..43ca1bccb5a 100644
--- a/src/renderer/src/lib/workspace-tab-palette-activation.ts
+++ b/src/renderer/src/lib/workspace-tab-palette-activation.ts
@@ -1,5 +1,5 @@
 import { focusTerminalTabSurface } from '@/lib/focus-terminal-tab-surface'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { activateWebRuntimeSessionTab } from '@/runtime/web-runtime-session-tab-lifecycle'
 import { isWebRuntimeSessionActive } from '@/runtime/web-runtime-session-environment'
 import { useAppStore } from '@/store'
@@ -119,10 +119,7 @@ export function activateWorkspaceTabPaletteResult(
     return { status: 'failed', reason: finalFailure }
   }
 
-  const runtimeEnvironmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
-    state,
-    result.worktreeId
-  )
+  const runtimeEnvironmentId = runtimeEnvironmentIdOrLocalUnlessTwin(state, result.worktreeId)
   state.focusGroup(result.worktreeId, result.groupId)
   state.activateTab(result.tabId, { worktreeId: result.worktreeId })
 
diff --git a/src/renderer/src/lib/worktree-activation-pty-inventory.ts b/src/renderer/src/lib/worktree-activation-pty-inventory.ts
index a91a78fa24f..2018f8578a1 100644
--- a/src/renderer/src/lib/worktree-activation-pty-inventory.ts
+++ b/src/renderer/src/lib/worktree-activation-pty-inventory.ts
@@ -2,7 +2,7 @@ import { FLOATING_TERMINAL_WORKTREE_ID } from '../../../shared/constants'
 import { parseExecutionHostId } from '../../../shared/execution-host'
 import type { PtyListedSession, PtySessionListScope } from '../../../shared/pty-listed-session'
 import { getRepoIdFromWorktreeId } from '../../../shared/worktree/id'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from './worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from './worktree-runtime-owner'
 import {
   resolveIndexedRepoOwner,
   resolveIndexedWorktreeOwner
@@ -21,10 +21,7 @@ export function resolveActivationPtyListScope(
     return { connectionId: null }
   }
   const resolution = resolveWorktreeOperationRouteResult(state, worktreeId)
-  if (
-    resolution.kind === 'missing' &&
-    !runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId)
-  ) {
+  if (resolution.kind === 'missing' && !runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)) {
     const repo = resolveIndexedRepoOwner(state.repos, getRepoIdFromWorktreeId(worktreeId))
     const worktree = resolveIndexedWorktreeOwner(state.worktreesByRepo, worktreeId)
     // A known native repo remains usable while the unrelated runtime catalog hydrates.
diff --git a/src/renderer/src/lib/worktree-activation.ts b/src/renderer/src/lib/worktree-activation.ts
index f611e66ed5b..83eef2b096f 100644
--- a/src/renderer/src/lib/worktree-activation.ts
+++ b/src/renderer/src/lib/worktree-activation.ts
@@ -7,7 +7,7 @@ import { registerWorktreeActivation } from '@/lib/worktree-activation-nav-regist
 import { workspaceHasSleepingAgentSessions } from '@/lib/worktree-agent-activation-gate'
 import { resumeSleepingAgentSessionsForWorktree } from '@/lib/resume-sleeping-agent-session'
 import { shouldAutoCreateInitialTerminal } from '@/components/terminal/initial-terminal'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { folderWorkspaceKey, parseWorkspaceKey } from '../../../shared/workspace-scope'
 import {
   folderWorkspaceActivationBlocked,
@@ -211,7 +211,7 @@ export function activateAndRevealWorktree(
   // 3. Core activation: setActiveWorktree also restores per-worktree state, clears unread, bumps dead PTY generations, refreshes GitHub
   state.setActiveWorktree(worktreeId, opts?.executionHostId)
   const postActivationState = useAppStore.getState()
-  const ownerRuntimeEnvironmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
+  const ownerRuntimeEnvironmentId = runtimeEnvironmentIdOrLocalUnlessTwin(
     postActivationState,
     wt.id
   )
diff --git a/src/renderer/src/lib/worktree-creation-agent-seeds.ts b/src/renderer/src/lib/worktree-creation-agent-seeds.ts
index 81e7549c132..0ae0aab02eb 100644
--- a/src/renderer/src/lib/worktree-creation-agent-seeds.ts
+++ b/src/renderer/src/lib/worktree-creation-agent-seeds.ts
@@ -2,7 +2,7 @@ import { useAppStore } from '@/store'
 import { seedNativeChatAppliedSessionOptions } from '@/components/native-chat/native-chat-session-option-cache'
 import { seedNativeChatLaunchDraftForAgentTab } from '@/lib/agent-launch-prompt-delivery'
 import { queueHookCommandsForFirstWorktreeTab } from '@/lib/hook-command-delayed-delivery'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { toWebTerminalSurfaceTabId } from '../../../shared/terminal-surface-id'
 import type { WorktreeCreationRequest } from '@/lib/pending-worktree-creation'
 import type { TuiAgent } from '../../../shared/tui-agent'
@@ -31,7 +31,7 @@ function resolveLaunchAgentTabId(
   const worktreeTabs = state.tabsByWorktree[args.worktreeId] ?? []
   // Main spawned the agent itself, so its startup tab is authoritative.
   if (args.backendSpawned && args.startupTerminalTabId) {
-    return runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, args.worktreeId)
+    return runtimeEnvironmentIdOrLocalUnlessTwin(state, args.worktreeId)
       ? toWebTerminalSurfaceTabId(args.startupTerminalTabId)
       : args.startupTerminalTabId
   }
diff --git a/src/renderer/src/lib/worktree-reactivation-preserved-pane-replacement.test.ts b/src/renderer/src/lib/worktree-reactivation-preserved-pane-replacement.test.ts
index bbc135af0d1..41cd31c2f1f 100644
--- a/src/renderer/src/lib/worktree-reactivation-preserved-pane-replacement.test.ts
+++ b/src/renderer/src/lib/worktree-reactivation-preserved-pane-replacement.test.ts
@@ -7,7 +7,7 @@ import { waitForWorktreeAgentActivationGateForTests } from './worktree-agent-act
 import { makeCreatedAgentWorktree as makeWorktree } from '@/lib/worktree-activation-created-agent.test-fixture'
 import { makePaneKey } from '../../../shared/stable-pane-id'
 import type { ExecutionHostId } from '../../../shared/execution-host'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from './worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from './worktree-runtime-owner'
 import {
   markHostSessionMirrorHydrated,
   resetHostSessionMirrorHydrationForTests
@@ -331,9 +331,9 @@ describe('preserved-pane replacement contract on workspace activation', () => {
       }
     }))
 
-    expect(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(useAppStore.getState(), worktree.id)
-    ).toBe(RUNTIME_ENV_ID)
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(useAppStore.getState(), worktree.id)).toBe(
+      RUNTIME_ENV_ID
+    )
 
     activateAndRevealWorktree(worktree.id, { notifyHostRuntime: false })
     await waitForWorktreeAgentActivationGateForTests(worktree.id)
diff --git a/src/renderer/src/lib/worktree-row-open-in-owner.ts b/src/renderer/src/lib/worktree-row-open-in-owner.ts
index 8c95361f0a1..30cdce3589f 100644
--- a/src/renderer/src/lib/worktree-row-open-in-owner.ts
+++ b/src/renderer/src/lib/worktree-row-open-in-owner.ts
@@ -1,6 +1,6 @@
 import { parseExecutionHostId } from '../../../shared/execution-host'
 import type { Worktree } from '../../../shared/worktree/types'
-import { resolveOwnerWithLegacyFallback } from './worktree-runtime-owner'
+import { resolveOwnerOrLocal } from './worktree-runtime-owner'
 import type { WorktreeRuntimeOwnerState } from './worktree-runtime-owner-state'
 import {
   resolveWorktreeOperationRouteResultForHost,
@@ -46,7 +46,7 @@ export function resolveWorktreeRowOpenInRuntimeOwner(
   }
   if (!worktree.hostId) {
     // Why: a twin names no owner, and Open in must not launch it as this desktop's checkout.
-    const owner = resolveOwnerWithLegacyFallback(state, { workspaceId: worktree.id })
+    const owner = resolveOwnerOrLocal(state, { workspaceId: worktree.id })
     if (owner.kind === 'ambiguous') {
       return UNRESOLVED
     }
diff --git a/src/renderer/src/lib/worktree-runtime-owner.test.ts b/src/renderer/src/lib/worktree-runtime-owner.test.ts
index 4c614d22185..c93a5a27181 100644
--- a/src/renderer/src/lib/worktree-runtime-owner.test.ts
+++ b/src/renderer/src/lib/worktree-runtime-owner.test.ts
@@ -3,7 +3,7 @@ import { FLOATING_TERMINAL_WORKTREE_ID } from '../../../shared/constants'
 import {
   getExecutionHostIdForWorktree,
   getKnownExecutionHostIdForWorktree,
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin
+  runtimeEnvironmentIdOrLocalUnlessTwin
 } from './worktree-runtime-owner'
 import { resolveTerminalPtyOwner } from './terminal-worktree-route'
 import { getRuntimeSessionMirrorEnvironmentIds } from './runtime-session-mirror-owners'
@@ -44,15 +44,13 @@ const state: WorktreeRuntimeOwnerState = {
   ]
 }
 
-describe('runtimeEnvironmentIdWithLegacyFallbackUnlessTwin', () => {
+describe('runtimeEnvironmentIdOrLocalUnlessTwin', () => {
   it('routes to the runtime owner of the worktree', () => {
-    expect(runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, 'runtime-repo::wt-b')).toBe(
-      'owner-env'
-    )
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(state, 'runtime-repo::wt-b')).toBe('owner-env')
   })
 
   it('keeps explicit-local worktrees local even while a runtime is focused', () => {
-    expect(runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, 'local-repo::wt-a')).toBeNull()
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(state, 'local-repo::wt-a')).toBeNull()
   })
 
   it('keeps the synthetic floating workspace local while a runtime is focused', () => {
@@ -62,7 +60,7 @@ describe('runtimeEnvironmentIdWithLegacyFallbackUnlessTwin', () => {
       activeWorkspaceExecutionHostId: 'runtime:focused-env'
     }
     expect(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(floatingState, FLOATING_TERMINAL_WORKTREE_ID)
+      runtimeEnvironmentIdOrLocalUnlessTwin(floatingState, FLOATING_TERMINAL_WORKTREE_ID)
     ).toBeNull()
     expect(getKnownExecutionHostIdForWorktree(floatingState, FLOATING_TERMINAL_WORKTREE_ID)).toBe(
       'local'
@@ -73,9 +71,7 @@ describe('runtimeEnvironmentIdWithLegacyFallbackUnlessTwin', () => {
   })
 
   it('routes folder workspaces to their project group runtime owner', () => {
-    expect(runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, 'folder:runtime-folder')).toBe(
-      'folder-env'
-    )
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(state, 'folder:runtime-folder')).toBe('folder-env')
     expect(getExecutionHostIdForWorktree(state, 'folder:runtime-folder')).toBe('runtime:folder-env')
   })
 
@@ -111,10 +107,7 @@ describe('runtimeEnvironmentIdWithLegacyFallbackUnlessTwin', () => {
     }
 
     expect(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
-        restoredFolderState,
-        'folder:restored-folder'
-      )
+      runtimeEnvironmentIdOrLocalUnlessTwin(restoredFolderState, 'folder:restored-folder')
     ).toBe('restored-env')
     expect(ownerEnvironmentId(restoredFolderState, 'folder:restored-folder')).toBe('restored-env')
     expect(getExecutionHostIdForWorktree(restoredFolderState, 'folder:restored-folder')).toBe(
@@ -123,9 +116,7 @@ describe('runtimeEnvironmentIdWithLegacyFallbackUnlessTwin', () => {
   })
 
   it('keeps explicit-local folder workspaces local even while a runtime is focused', () => {
-    expect(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, 'folder:local-folder')
-    ).toBeNull()
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(state, 'folder:local-folder')).toBeNull()
     expect(getExecutionHostIdForWorktree(state, 'folder:local-folder')).toBe('local')
 
     const restoredOwnerState: WorktreeRuntimeOwnerState = {
@@ -135,7 +126,7 @@ describe('runtimeEnvironmentIdWithLegacyFallbackUnlessTwin', () => {
       }
     }
     expect(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(restoredOwnerState, 'folder:local-folder')
+      runtimeEnvironmentIdOrLocalUnlessTwin(restoredOwnerState, 'folder:local-folder')
     ).toBeNull()
     expect(getExecutionHostIdForWorktree(restoredOwnerState, 'folder:local-folder')).toBe('local')
   })
@@ -150,7 +141,7 @@ describe('runtimeEnvironmentIdWithLegacyFallbackUnlessTwin', () => {
     }
 
     expect(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(folderConnectionState, 'folder:folder-ssh')
+      runtimeEnvironmentIdOrLocalUnlessTwin(folderConnectionState, 'folder:folder-ssh')
     ).toBeNull()
     expect(getExecutionHostIdForWorktree(folderConnectionState, 'folder:folder-ssh')).toBe(
       'ssh:folder-remote'
@@ -166,10 +157,7 @@ describe('runtimeEnvironmentIdWithLegacyFallbackUnlessTwin', () => {
     }
 
     expect(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
-        staleFolderConnectionState,
-        'folder:runtime-folder'
-      )
+      runtimeEnvironmentIdOrLocalUnlessTwin(staleFolderConnectionState, 'folder:runtime-folder')
     ).toBe('folder-env')
     expect(getExecutionHostIdForWorktree(staleFolderConnectionState, 'folder:runtime-folder')).toBe(
       'runtime:folder-env'
@@ -200,7 +188,7 @@ describe('resolveTerminalPtyOwner', () => {
       kind: 'ambiguous'
     })
     // Why: read-only callers keep the old collapse to "no server".
-    expect(runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(twinState, 'twin-repo::wt')).toBeNull()
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(twinState, 'twin-repo::wt')).toBeNull()
   })
 })
 
@@ -228,9 +216,9 @@ describe('the explicit owner environment (resolveOwner)', () => {
     }
 
     expect(ownerEnvironmentId(nestedState, 'nested-repo::remote-worktree')).toBe('owner-hub')
-    expect(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(nestedState, 'nested-repo::remote-worktree')
-    ).toBe('owner-hub')
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(nestedState, 'nested-repo::remote-worktree')).toBe(
+      'owner-hub'
+    )
     expect(getExecutionHostIdForWorktree(nestedState, 'nested-repo::remote-worktree')).toBe(
       'ssh:hub-private-ssh'
     )
@@ -349,12 +337,12 @@ describe('the explicit owner environment (resolveOwner)', () => {
       }
     }
 
-    expect(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(multiHubState, 'repo-a::ssh-worktree')
-    ).toBe('hub-a')
-    expect(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(multiHubState, 'repo-b::ssh-worktree')
-    ).toBe('hub-b')
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(multiHubState, 'repo-a::ssh-worktree')).toBe(
+      'hub-a'
+    )
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(multiHubState, 'repo-b::ssh-worktree')).toBe(
+      'hub-b'
+    )
     expect(getExecutionHostIdForWorktree(multiHubState, 'repo-a::ssh-worktree')).toBe(
       'ssh:private-a'
     )
@@ -364,9 +352,7 @@ describe('the explicit owner environment (resolveOwner)', () => {
   })
 
   it('does not treat the focused runtime as ownership for legacy-local worktrees', () => {
-    expect(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, 'legacy-repo::wt-legacy')
-    ).toBeNull()
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(state, 'legacy-repo::wt-legacy')).toBeNull()
     expect(ownerEnvironmentId(state, 'legacy-repo::wt-legacy')).toBeNull()
     expect(getExecutionHostIdForWorktree(state, 'legacy-repo::wt-legacy')).toBe('local')
     expect(getExecutionHostIdForWorktree(state, 'unknown-repo::wt')).toBe('local')
@@ -401,10 +387,7 @@ describe('the explicit owner environment (resolveOwner)', () => {
 
     expect(ownerEnvironmentId(hostOverrideState, 'runtime-repo::wt-local-override')).toBeNull()
     expect(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
-        hostOverrideState,
-        'runtime-repo::wt-local-override'
-      )
+      runtimeEnvironmentIdOrLocalUnlessTwin(hostOverrideState, 'runtime-repo::wt-local-override')
     ).toBeNull()
     expect(
       getExecutionHostIdForWorktree(hostOverrideState, 'runtime-repo::wt-local-override')
@@ -413,10 +396,7 @@ describe('the explicit owner environment (resolveOwner)', () => {
       'worktree-env'
     )
     expect(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
-        hostOverrideState,
-        'runtime-repo::wt-runtime-override'
-      )
+      runtimeEnvironmentIdOrLocalUnlessTwin(hostOverrideState, 'runtime-repo::wt-runtime-override')
     ).toBe('worktree-env')
     expect(
       getExecutionHostIdForWorktree(hostOverrideState, 'runtime-repo::wt-runtime-override')
@@ -503,13 +483,10 @@ describe('runtime owner identity indexes', () => {
     }
 
     for (let lookup = 0; lookup < 200; lookup += 1) {
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(indexedState, targetWorktreeId)
+      runtimeEnvironmentIdOrLocalUnlessTwin(indexedState, targetWorktreeId)
       ownerEnvironmentId(indexedState, targetWorktreeId)
       getExecutionHostIdForWorktree(indexedState, targetWorktreeId)
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
-        indexedState,
-        `folder:${targetFolderWorkspaceId}`
-      )
+      runtimeEnvironmentIdOrLocalUnlessTwin(indexedState, `folder:${targetFolderWorkspaceId}`)
       ownerEnvironmentId(indexedState, `folder:${targetFolderWorkspaceId}`)
       getExecutionHostIdForWorktree(indexedState, `folder:${targetFolderWorkspaceId}`)
     }
@@ -519,9 +496,7 @@ describe('runtime owner identity indexes', () => {
     expect(repoIdReads).toBe(200)
     expect(folderWorkspaceIdReads).toBe(1_000)
     expect(projectGroupIdReads).toBe(1_000)
-    expect(runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(indexedState, targetWorktreeId)).toBe(
-      'repo-owner'
-    )
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(indexedState, targetWorktreeId)).toBe('repo-owner')
     expect(getExecutionHostIdForWorktree(indexedState, `folder:${targetFolderWorkspaceId}`)).toBe(
       'runtime:folder-owner'
     )
@@ -534,10 +509,8 @@ describe('runtime owner identity indexes', () => {
       folderWorkspaces: [{ id: 'folder', projectGroupId: 'group' }],
       projectGroups: [{ id: 'group', connectionId: null, executionHostId: 'runtime:folder-one' }]
     }
-    expect(runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(first, 'worktree')).toBe('repo-one')
-    expect(runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(first, 'folder:folder')).toBe(
-      'folder-one'
-    )
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(first, 'worktree')).toBe('repo-one')
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(first, 'folder:folder')).toBe('folder-one')
 
     const second: WorktreeRuntimeOwnerState = {
       repos: [{ id: 'repo', connectionId: null, executionHostId: 'runtime:repo-two' }],
@@ -547,12 +520,8 @@ describe('runtime owner identity indexes', () => {
       folderWorkspaces: [{ id: 'folder', projectGroupId: 'group' }],
       projectGroups: [{ id: 'group', connectionId: null, executionHostId: 'runtime:folder-two' }]
     }
-    expect(runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(second, 'worktree')).toBe(
-      'worktree-two'
-    )
-    expect(runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(second, 'folder:folder')).toBe(
-      'folder-two'
-    )
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(second, 'worktree')).toBe('worktree-two')
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(second, 'folder:folder')).toBe('folder-two')
   })
 })
 
@@ -654,9 +623,9 @@ describe('active workspace host selection', () => {
   }
 
   it('keeps the HUB transport for the active paired SSH worktree', () => {
-    expect(
-      runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(pairedHubState, PAIRED_HUB_WORKTREE_ID)
-    ).toBe('hub-a')
+    expect(runtimeEnvironmentIdOrLocalUnlessTwin(pairedHubState, PAIRED_HUB_WORKTREE_ID)).toBe(
+      'hub-a'
+    )
     expect(ownerEnvironmentId(pairedHubState, PAIRED_HUB_WORKTREE_ID)).toBe('hub-a')
   })
 
diff --git a/src/renderer/src/lib/worktree-runtime-owner.ts b/src/renderer/src/lib/worktree-runtime-owner.ts
index 39810bbe26a..7ab24f74c5b 100644
--- a/src/renderer/src/lib/worktree-runtime-owner.ts
+++ b/src/renderer/src/lib/worktree-runtime-owner.ts
@@ -123,10 +123,10 @@ export function getExecutionHostIdForWorktree(
 }
 
 /**
- * {@link resolveOwner}, reading an id no row places as this app's — or, for a folder, the server
- * its saved session names, or a web client's only server.
+ * {@link resolveOwner}, except an id no row places and no caller names a host resolves to this app
+ * instead of `missing` — or, for a folder, to its saved session's server or a web client's only one.
  */
-export function resolveOwnerWithLegacyFallback(
+export function resolveOwnerOrLocal(
   state: WorktreeRuntimeOwnerState,
   ref: WorkspaceOwnerRef
 ): ExecutionHostOwnerMatch<HostAuthority> {
@@ -148,17 +148,18 @@ export function resolveOwnerWithLegacyFallback(
 }
 
 /**
- * The paired server behind {@link resolveOwnerWithLegacyFallback}, or `null` for this app, a
- * directly dialed SSH target or a twin: for readers whose twin answer is "no server", as before.
+ * The paired server {@link resolveOwnerOrLocal} names, or `null` for this app, a directly dialed
+ * SSH target or a twin. Unlike `runtimeEnvironmentIdUnlessTwin`, an unplaced folder on a web
+ * client names that client's server.
  */
-export function runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
+export function runtimeEnvironmentIdOrLocalUnlessTwin(
   state: WorktreeRuntimeOwnerState,
   workspaceId: string | null | undefined
 ): string | null {
   if (!workspaceId) {
     return null
   }
-  const match = resolveOwnerWithLegacyFallback(state, { workspaceId })
+  const match = resolveOwnerOrLocal(state, { workspaceId })
   return match.kind === 'resolved' && match.owner.endpoint.kind === 'environment'
     ? match.owner.endpoint.environmentId
     : null
diff --git a/src/renderer/src/lib/worktree-sort-order-host-split.ts b/src/renderer/src/lib/worktree-sort-order-host-split.ts
index 0e47942364b..bbfcd046eec 100644
--- a/src/renderer/src/lib/worktree-sort-order-host-split.ts
+++ b/src/renderer/src/lib/worktree-sort-order-host-split.ts
@@ -1,6 +1,6 @@
 import { LOCAL_EXECUTION_HOST_ID, toRuntimeExecutionHostId } from '../../../shared/execution-host'
 import { isUnprovenServerSshRoute } from './resolve-owner'
-import { resolveOwnerWithLegacyFallback } from './worktree-runtime-owner'
+import { resolveOwnerOrLocal } from './worktree-runtime-owner'
 import type { WorktreeRuntimeOwnerState } from './worktree-runtime-owner-state'
 
 export type WorktreeSortOrderHostGroup = {
@@ -25,7 +25,7 @@ export function splitWorktreeSortOrderByHost(
 ): WorktreeSortOrderHostGroup[] {
   const groups = new Map<string, { orderedIds: string[]; rowHostIds: string[] }>()
   for (const id of orderedIds) {
-    const owner = resolveOwnerWithLegacyFallback(state, { workspaceId: id })
+    const owner = resolveOwnerOrLocal(state, { workspaceId: id })
     // Why: a twin names no host to write to, and an unproven server route may be another machine.
     if (owner.kind !== 'resolved' || isUnprovenServerSshRoute(state, id, owner.owner)) {
       continue
diff --git a/src/renderer/src/runtime/web-runtime-session.test.ts b/src/renderer/src/runtime/web-runtime-session.test.ts
index 1e2964eef76..f04b3abfe2c 100644
--- a/src/renderer/src/runtime/web-runtime-session.test.ts
+++ b/src/renderer/src/runtime/web-runtime-session.test.ts
@@ -31,7 +31,7 @@ const mocks = vi.hoisted(() => ({
   trackTerminalPaneSplit: vi.fn(),
   deliverLaunchPromptToAgentTab: vi.fn(),
   seedNativeChatLaunchDraftForAgentTab: vi.fn(),
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin: vi.fn(),
+  runtimeEnvironmentIdOrLocalUnlessTwin: vi.fn(),
   hasMaterializedWebRuntimeBrowserPage: vi.fn(),
   recoverWebSessionTerminalOrphansBeforeApply: vi.fn(
     async (_state: unknown, snapshot: unknown) => snapshot
@@ -76,8 +76,7 @@ vi.mock('@/lib/feature-education-telemetry', () => ({
 }))
 
 vi.mock('@/lib/worktree-runtime-owner', () => ({
-  runtimeEnvironmentIdWithLegacyFallbackUnlessTwin:
-    mocks.runtimeEnvironmentIdWithLegacyFallbackUnlessTwin
+  runtimeEnvironmentIdOrLocalUnlessTwin: mocks.runtimeEnvironmentIdOrLocalUnlessTwin
 }))
 
 vi.mock('@/lib/agent-launch-prompt-delivery', () => ({
diff --git a/src/renderer/src/store/slices/browser/browser-page-conversion-actions.ts b/src/renderer/src/store/slices/browser/browser-page-conversion-actions.ts
index 857b6a85e86..59aca0e2cc1 100644
--- a/src/renderer/src/store/slices/browser/browser-page-conversion-actions.ts
+++ b/src/renderer/src/store/slices/browser/browser-page-conversion-actions.ts
@@ -8,7 +8,7 @@ import type { BrowserPage } from '../../../../../shared/browser-workspace-types'
 import { planBrowserPageConversion } from '../browser-page-conversion'
 import { findPage, findWorkspace, mirrorWorkspaceFromActivePage } from '../browser-page-records'
 import { assertManagedBrowserMaterializationAllowed } from '@/lib/client-creation-action-policy'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { closeRemoteBrowserPageInOwningEnvironment } from './browser-remote-close'
 import { releaseDocPreviewGrant } from '@/lib/doc-preview-grants'
 import { isLocalBrowserPageOwner } from './browser-host-state'
@@ -37,10 +37,7 @@ export function createBrowserPageConversionActions(
         declaredOwnership !== undefined
           ? declaredOwnership
           : oldPageForOwnership
-            ? runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
-                get(),
-                oldPageForOwnership.worktreeId
-              )
+            ? runtimeEnvironmentIdOrLocalUnlessTwin(get(), oldPageForOwnership.worktreeId)
             : null
       )
       let converted: BrowserPage | null = null
diff --git a/src/renderer/src/store/slices/browser/browser-tab-actions.ts b/src/renderer/src/store/slices/browser/browser-tab-actions.ts
index fb57dc7f400..23cd123ed5d 100644
--- a/src/renderer/src/store/slices/browser/browser-tab-actions.ts
+++ b/src/renderer/src/store/slices/browser/browser-tab-actions.ts
@@ -16,7 +16,7 @@ import {
   findWorkspace
 } from '../browser-page-records'
 import { getBrowserSessionProfileHostId } from './browser-host-state'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { admitBrowserPageMount } from '@/components/browser-pane/host-guest/browser-page-mount-admission'
 import { ownsGlobalSelection } from '../../global-selection-owner'
 import {
@@ -197,10 +197,7 @@ export function createBrowserTabActions(
         throw new Error(browserAvailability.reason)
       }
       const defaultUrl = state.browserDefaultUrl ?? 'about:blank'
-      const runtimeEnvironmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
-        state,
-        worktreeId
-      )
+      const runtimeEnvironmentId = runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)
       if (browserAvailability.provider === 'paired-runtime') {
         if (!runtimeEnvironmentId) {
           throw new Error('The paired runtime browser provider is unavailable.')
@@ -253,10 +250,7 @@ export function createBrowserTabActions(
       if (browserAvailability.state !== 'enabled') {
         return false
       }
-      const runtimeEnvironmentId = runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(
-        state,
-        worktreeId
-      )
+      const runtimeEnvironmentId = runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)
       if (browserAvailability.provider === 'paired-runtime') {
         if (!runtimeEnvironmentId) {
           return false
diff --git a/src/renderer/src/store/slices/tabs/tabs-host-mirroring.ts b/src/renderer/src/store/slices/tabs/tabs-host-mirroring.ts
index b81e883e4b1..8b778eafefc 100644
--- a/src/renderer/src/store/slices/tabs/tabs-host-mirroring.ts
+++ b/src/renderer/src/store/slices/tabs/tabs-host-mirroring.ts
@@ -1,7 +1,7 @@
 import type { AppState } from '../../types'
 import type { TerminalTab } from '../../../../../shared/terminal-tab-types'
 import { findTabAndWorktree } from '../tab-group-state'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { locateTerminalTab } from '../../terminals/terminal-tab-location'
 
 /**
@@ -33,7 +33,7 @@ export function mirrorTabPinnedToHost(state: AppState, tabId: string, isPinned:
   if (
     !found ||
     found.tab.contentType !== 'terminal' ||
-    !runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, found.worktreeId)
+    !runtimeEnvironmentIdOrLocalUnlessTwin(state, found.worktreeId)
   ) {
     return
   }
@@ -55,7 +55,7 @@ export function mirrorTabViewModeToHost(
   if (
     !found ||
     found.tab.contentType !== 'terminal' ||
-    !runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, found.worktreeId)
+    !runtimeEnvironmentIdOrLocalUnlessTwin(state, found.worktreeId)
   ) {
     return
   }
diff --git a/src/renderer/src/store/terminals/terminal-active-workspace-creation.ts b/src/renderer/src/store/terminals/terminal-active-workspace-creation.ts
index 7d11bc7a9f4..c1636f3cd70 100644
--- a/src/renderer/src/store/terminals/terminal-active-workspace-creation.ts
+++ b/src/renderer/src/store/terminals/terminal-active-workspace-creation.ts
@@ -1,7 +1,7 @@
 import { FLOATING_TERMINAL_WORKTREE_ID } from '../../../../shared/constants'
 import { parseWorkspaceKey } from '../../../../shared/workspace-scope'
 import { focusTerminalTabSurface } from '@/lib/focus-terminal-tab-surface'
-import { runtimeEnvironmentIdWithLegacyFallbackUnlessTwin } from '@/lib/worktree-runtime-owner'
+import { runtimeEnvironmentIdOrLocalUnlessTwin } from '@/lib/worktree-runtime-owner'
 import { resolveWorktreeOperationRouteResult } from '@/lib/worktree-operation-route'
 import { isWebClientLocation } from '@/lib/web-client-location'
 import type { TerminalSlice, TerminalStoreGet, TerminalStoreSet } from './terminal-state'
@@ -27,7 +27,7 @@ export function createActiveWorkspaceTerminalActions(
       }
       const runtimeEnvironmentId = worktreeRoute
         ? worktreeRoute.route.runtimeEnvironmentId
-        : runtimeEnvironmentIdWithLegacyFallbackUnlessTwin(state, worktreeId)
+        : runtimeEnvironmentIdOrLocalUnlessTwin(state, worktreeId)
       if (runtimeEnvironmentId) {
         const { createWebRuntimeSessionTerminal } =
           await import('@/runtime/web-runtime-terminal-creation')