diff --git a/mobile/src/session/use-mobile-session-view-mode.test.ts b/mobile/src/session/use-mobile-session-view-mode.test.ts
index 4008ea8bd13..6cf6687f22d 100644
--- a/mobile/src/session/use-mobile-session-view-mode.test.ts
+++ b/mobile/src/session/use-mobile-session-view-mode.test.ts
@@ -4,6 +4,7 @@ import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import {
   loadDefaultSessionView,
   loadSessionViewOverrides,
+  readSessionViewOverridesPreference,
   updateSessionViewOverride,
   type MobileSessionView
 } from '../storage/session-view-preferences'
@@ -44,6 +45,7 @@ vi.mock('expo-router', async () => {
 vi.mock('../storage/session-view-preferences', () => ({
   loadDefaultSessionView: vi.fn(),
   loadSessionViewOverrides: vi.fn(),
+  readSessionViewOverridesPreference: vi.fn(),
   updateSessionViewOverride: vi.fn()
 }))
 
@@ -55,6 +57,9 @@ describe('useMobileSessionViewMode', () => {
     globalThis.IS_REACT_ACT_ENVIRONMENT = true
     vi.mocked(loadDefaultSessionView).mockReset().mockResolvedValue('terminal')
     vi.mocked(loadSessionViewOverrides).mockReset().mockResolvedValue(new Map())
+    vi.mocked(readSessionViewOverridesPreference)
+      .mockReset()
+      .mockResolvedValue({ overrides: new Map(), loaded: true })
     vi.mocked(updateSessionViewOverride).mockReset().mockResolvedValue(undefined)
     focusEffectRuntime.callback = null
   })
@@ -70,7 +75,10 @@ describe('useMobileSessionViewMode', () => {
     overrides?: Map<string, MobileSessionView>
   }): Promise<void> {
     vi.mocked(loadDefaultSessionView).mockResolvedValue(args.defaultView)
-    vi.mocked(loadSessionViewOverrides).mockResolvedValue(args.overrides ?? new Map())
+    vi.mocked(readSessionViewOverridesPreference).mockResolvedValue({
+      overrides: args.overrides ?? new Map(),
+      loaded: true
+    })
     function Harness(): null {
       controller = useMobileSessionViewMode({ hostId: 'h', worktreeId: 'w' })
       return null
@@ -124,7 +132,7 @@ describe('useMobileSessionViewMode', () => {
 
     expect(updateSessionViewOverride).toHaveBeenLastCalledWith('h', 'w', 't1', 'terminal')
     expect(controller?.isTabChatView('t1')).toBe(false)
-    expect(loadSessionViewOverrides).toHaveBeenCalledTimes(1)
+    expect(readSessionViewOverridesPreference).toHaveBeenCalledTimes(1)
   })
 
   it('toggles a terminal-default tab into chat', async () => {
@@ -141,10 +149,13 @@ describe('useMobileSessionViewMode', () => {
 
   it('does not expose overrides from the previous host while the next scope loads', async () => {
     const nextScopeLoad = deferred<Map<string, MobileSessionView>>()
-    vi.mocked(loadSessionViewOverrides).mockImplementation((hostId) =>
+    vi.mocked(readSessionViewOverridesPreference).mockImplementation((hostId) =>
       hostId === 'h1'
-        ? Promise.resolve(new Map([['same-tab-id', 'chat' as const]]))
-        : nextScopeLoad.promise
+        ? Promise.resolve({
+            overrides: new Map([['same-tab-id', 'chat' as const]]),
+            loaded: true
+          })
+        : nextScopeLoad.promise.then((overrides) => ({ overrides, loaded: true }))
     )
     function Harness(props: { hostId: string; worktreeId: string }): null {
       controller = useMobileSessionViewMode(props)
@@ -171,7 +182,9 @@ describe('useMobileSessionViewMode', () => {
 
   it('merges a toggle made during load with the other persisted overrides', async () => {
     const overridesLoad = deferred<Map<string, MobileSessionView>>()
-    vi.mocked(loadSessionViewOverrides).mockReturnValue(overridesLoad.promise)
+    vi.mocked(readSessionViewOverridesPreference).mockReturnValue(
+      overridesLoad.promise.then((overrides) => ({ overrides, loaded: true }))
+    )
     function Harness(): null {
       controller = useMobileSessionViewMode({ hostId: 'h', worktreeId: 'w' })
       return null
@@ -218,7 +231,8 @@ describe('useMobileSessionViewMode', () => {
     })
 
     expect(controller?.isTabChatView('t1')).toBe(false)
-    expect(loadSessionViewOverrides).toHaveBeenCalledTimes(2)
+    expect(readSessionViewOverridesPreference).toHaveBeenCalledTimes(1)
+    expect(loadSessionViewOverrides).toHaveBeenCalledTimes(1)
   })
 
   it('does not let an older failed override roll back a newer choice', async () => {
@@ -247,7 +261,9 @@ describe('useMobileSessionViewMode', () => {
 
   it('finishes an early toggle save after the route unmounts', async () => {
     const overridesLoad = deferred<Map<string, MobileSessionView>>()
-    vi.mocked(loadSessionViewOverrides).mockReturnValue(overridesLoad.promise)
+    vi.mocked(readSessionViewOverridesPreference).mockReturnValue(
+      overridesLoad.promise.then((overrides) => ({ overrides, loaded: true }))
+    )
     function Harness(): null {
       controller = useMobileSessionViewMode({ hostId: 'h', worktreeId: 'w' })
       return null
@@ -283,6 +299,27 @@ describe('useMobileSessionViewMode', () => {
       await Promise.resolve()
     })
 
-    expect(loadSessionViewOverrides).toHaveBeenCalledTimes(1)
+    expect(readSessionViewOverridesPreference).toHaveBeenCalledTimes(1)
+    expect(loadSessionViewOverrides).not.toHaveBeenCalled()
+  })
+
+  it('fails closed to terminal when overrides cannot be read under a chat default', async () => {
+    vi.mocked(loadDefaultSessionView).mockResolvedValue('chat')
+    vi.mocked(readSessionViewOverridesPreference).mockResolvedValue({
+      overrides: new Map(),
+      loaded: false
+    })
+
+    function Harness(): null {
+      controller = useMobileSessionViewMode({ hostId: 'h', worktreeId: 'w' })
+      return null
+    }
+    await act(async () => {
+      renderer = create(createElement(Harness))
+      await Promise.resolve()
+      await Promise.resolve()
+    })
+
+    expect(controller?.isTabChatView('t1')).toBe(false)
   })
 })
diff --git a/mobile/src/session/use-mobile-session-view-mode.ts b/mobile/src/session/use-mobile-session-view-mode.ts
index 61668808acd..5b8faa59ef4 100644
--- a/mobile/src/session/use-mobile-session-view-mode.ts
+++ b/mobile/src/session/use-mobile-session-view-mode.ts
@@ -3,8 +3,10 @@ import { useFocusEffect } from 'expo-router'
 import {
   loadDefaultSessionView,
   loadSessionViewOverrides,
+  readSessionViewOverridesPreference,
   updateSessionViewOverride,
-  type MobileSessionView
+  type MobileSessionView,
+  type SessionViewOverridesPreference
 } from '../storage/session-view-preferences'
 
 type ViewOverridesState = {
@@ -17,7 +19,7 @@ type ViewOverridesState = {
 type ViewOverridesRuntime = {
   hostId: string
   worktreeId: string
-  loadPromise: Promise<Map<string, MobileSessionView>>
+  loadPromise: Promise<SessionViewOverridesPreference>
   currentOverrides: Map<string, MobileSessionView>
   mutationRevisions: Map<string, number>
 }
@@ -75,7 +77,7 @@ export function useMobileSessionViewMode(args: {
     const next: ViewOverridesRuntime = {
       hostId: scopeHostId,
       worktreeId: scopeWorktreeId,
-      loadPromise: loadSessionViewOverrides(scopeHostId, scopeWorktreeId),
+      loadPromise: readSessionViewOverridesPreference(scopeHostId, scopeWorktreeId),
       currentOverrides: new Map(),
       mutationRevisions: new Map()
     }
@@ -91,15 +93,17 @@ export function useMobileSessionViewMode(args: {
   useEffect(() => {
     let active = true
     const runtime = ensureViewOverridesRuntime(hostId, worktreeId)
-    void runtime.loadPromise.then((persisted) => {
+    void runtime.loadPromise.then((preference) => {
       if (!active) {
         return
       }
       // Why: toggles made during the read are authoritative, but must not
       // discard unrelated persisted overrides from the same worktree.
-      const merged = mergeOverrides(persisted, runtime.currentOverrides)
+      const merged = mergeOverrides(preference.overrides, runtime.currentOverrides)
       runtime.currentOverrides = merged
-      const next = { hostId, worktreeId, overrides: merged, loaded: true }
+      // Why: an unreadable override store cannot safely be treated as empty when
+      // the default is chat; fail closed to terminal until a user toggles.
+      const next = { hostId, worktreeId, overrides: merged, loaded: preference.loaded }
       viewOverridesStateRef.current = next
       setViewOverridesState(next)
     })
diff --git a/mobile/src/storage/preferences.test.ts b/mobile/src/storage/preferences.test.ts
index 5b84e889c6f..13e43d45b43 100644
--- a/mobile/src/storage/preferences.test.ts
+++ b/mobile/src/storage/preferences.test.ts
@@ -24,6 +24,7 @@ import {
 import {
   loadDefaultSessionView,
   loadSessionViewOverrides,
+  readSessionViewOverridesPreference,
   saveDefaultSessionView,
   updateSessionViewOverride
 } from './session-view-preferences'
@@ -213,6 +214,11 @@ describe('session view preference', () => {
   it('does not replace saved overrides after a transient read failure', async () => {
     vi.mocked(AsyncStorage.getItem).mockRejectedValue(new Error('storage unavailable'))
 
+    await expect(readSessionViewOverridesPreference('host', 'worktree')).resolves.toEqual({
+      overrides: new Map(),
+      loaded: false
+    })
+
     await expect(updateSessionViewOverride('host', 'worktree', 'tab', 'chat')).rejects.toThrow(
       'Session view overrides could not be read'
     )
diff --git a/mobile/src/storage/session-view-preferences.ts b/mobile/src/storage/session-view-preferences.ts
index a09b2198ac9..750167e3d53 100644
--- a/mobile/src/storage/session-view-preferences.ts
+++ b/mobile/src/storage/session-view-preferences.ts
@@ -45,12 +45,14 @@ export function saveDefaultSessionView(view: MobileSessionView): Promise<void> {
   return write
 }
 
-type SessionViewOverridesRead = {
+export type SessionViewOverridesPreference = {
   overrides: Map<string, MobileSessionView>
   loaded: boolean
 }
 
-async function readSessionViewOverrides(key: string): Promise<SessionViewOverridesRead> {
+async function readSessionViewOverridesStorage(
+  key: string
+): Promise<SessionViewOverridesPreference> {
   let raw: string | null
   try {
     raw = await AsyncStorage.getItem(key)
@@ -95,9 +97,17 @@ export async function loadSessionViewOverrides(
   hostId: string,
   worktreeId: string
 ): Promise<Map<string, MobileSessionView>> {
+  return (await readSessionViewOverridesPreference(hostId, worktreeId)).overrides
+}
+
+/** Reads overrides without conflating an empty preference with unavailable storage. */
+export async function readSessionViewOverridesPreference(
+  hostId: string,
+  worktreeId: string
+): Promise<SessionViewOverridesPreference> {
   const key = sessionViewOverridesKey(hostId, worktreeId)
   await overrideUpdateBarriers.get(key)
-  return (await readSessionViewOverrides(key)).overrides
+  return readSessionViewOverridesStorage(key)
 }
 
 /** Persists one user mutation without replacing sibling overrides from another mount. */
@@ -110,7 +120,7 @@ export async function updateSessionViewOverride(
   const key = sessionViewOverridesKey(hostId, worktreeId)
   const previous = overrideUpdateBarriers.get(key) ?? Promise.resolve()
   const update = previous.then(async () => {
-    const current = await readSessionViewOverrides(key)
+    const current = await readSessionViewOverridesStorage(key)
     // Why: a transient read failure must not replace valid saved siblings with
     // a partial map containing only the latest tab.
     if (!current.loaded) {