diff --git a/mobile/app/h/[hostId]/accounts.tsx b/mobile/app/h/[hostId]/accounts.tsx
index 1a07a0d6ecc..b107f34da97 100644
--- a/mobile/app/h/[hostId]/accounts.tsx
+++ b/mobile/app/h/[hostId]/accounts.tsx
@@ -14,7 +14,7 @@ import { ChevronLeft, Check, RefreshCw, User } from 'lucide-react-native'
 import { loadHosts } from '../../../src/transport/host-store'
 import { useHostClient } from '../../../src/transport/client-context'
 import { colors, spacing } from '../../../src/theme/mobile-theme'
-import { styles } from './accounts-screen-styles'
+import { styles } from '../../../src/accounts/mobile-accounts-screen-styles'
 import { useNow } from '../../../src/hooks/use-now'
 import { ClaudeIcon, OpenAIIcon } from '../../../src/components/AgentIcons'
 import {
diff --git a/mobile/app/h/[hostId]/session/[worktreeId].tsx b/mobile/app/h/[hostId]/session/[worktreeId].tsx
index 5d9ba390035..8f6d7ca0c97 100644
--- a/mobile/app/h/[hostId]/session/[worktreeId].tsx
+++ b/mobile/app/h/[hostId]/session/[worktreeId].tsx
@@ -267,8 +267,8 @@ import {
   reconcileMobileSessionCreateWarningState
 } from '../../../../src/session/mobile-session-create-warning-state'
 import { colors, spacing } from '../../../../src/theme/mobile-theme'
-import { styles } from './mobile-session-styles'
-import { QuickCommandsTabButton } from './QuickCommandsTabButton'
+import { QuickCommandsTabButton } from '../../../../src/session/QuickCommandsTabButton'
+import { styles } from '../../../../src/session/mobile-session-styles'
 import type { DiffComment, TerminalQuickCommand } from '../../../../../src/shared/types'
 import type {
   DiffCommentActions,
@@ -289,7 +289,7 @@ import type {
   TerminalCreateResult,
   TerminalGestureInputBucket,
   TerminalGestureInputQueue
-} from './mobile-session-route-types'
+} from '../../../../src/session/mobile-session-route-types'
 
 const TERMINAL_KEYBOARD_DISMISS_ACTION_SHEET_FALLBACK_MS = 450
 
diff --git a/mobile/app/h/[hostId]/accounts-screen-styles.ts b/mobile/src/accounts/mobile-accounts-screen-styles.ts
similarity index 97%
rename from mobile/app/h/[hostId]/accounts-screen-styles.ts
rename to mobile/src/accounts/mobile-accounts-screen-styles.ts
index 4a987b7a442..65074f340ae 100644
--- a/mobile/app/h/[hostId]/accounts-screen-styles.ts
+++ b/mobile/src/accounts/mobile-accounts-screen-styles.ts
@@ -1,5 +1,5 @@
 import { StyleSheet } from 'react-native'
-import { colors, spacing, typography, radii } from '../../../src/theme/mobile-theme'
+import { colors, spacing, typography, radii } from '../theme/mobile-theme'
 
 export const styles = StyleSheet.create({
   container: {
diff --git a/mobile/src/expo-route-module-boundary.test.ts b/mobile/src/expo-route-module-boundary.test.ts
new file mode 100644
index 00000000000..3870f32c216
--- /dev/null
+++ b/mobile/src/expo-route-module-boundary.test.ts
@@ -0,0 +1,121 @@
+import { readFileSync, readdirSync } from 'node:fs'
+import { fileURLToPath } from 'node:url'
+import { basename, dirname, extname, join, relative } from 'node:path'
+import ts from 'typescript'
+import { describe, expect, it } from 'vitest'
+
+const appDirectory = fileURLToPath(new URL('../app', import.meta.url))
+const routeSourceExtensions = new Set(['.js', '.jsx', '.ts', '.tsx'])
+
+function sourceFiles(directory: string): string[] {
+  return readdirSync(directory, { withFileTypes: true }).flatMap((entry) => {
+    const path = join(directory, entry.name)
+    return entry.isDirectory() ? sourceFiles(path) : [path]
+  })
+}
+
+function isNonScreenExpoModule(path: string): boolean {
+  const fileName = basename(path)
+  if (/\+api\.[jt]sx?$/.test(fileName)) {
+    return true
+  }
+  return (
+    dirname(relative(appDirectory, path)) === '.' &&
+    /^\+(?:html|middleware|native-intent)\.[jt]sx?$/.test(fileName)
+  )
+}
+
+function isPlatformSpecificApiRoute(path: string): boolean {
+  return /\+api\.(?:android|ios|native|web)\.[jt]sx?$/.test(basename(path))
+}
+
+function hasDefaultExport(path: string, source: string): boolean {
+  const extension = extname(path)
+  const sourceFile = ts.createSourceFile(
+    path,
+    source,
+    ts.ScriptTarget.Latest,
+    true,
+    extension === '.jsx'
+      ? ts.ScriptKind.JSX
+      : extension === '.js'
+        ? ts.ScriptKind.JS
+        : extension === '.tsx'
+          ? ts.ScriptKind.TSX
+          : ts.ScriptKind.TS
+  )
+
+  return sourceFile.statements.some((statement) => {
+    if (ts.isExportAssignment(statement)) {
+      return !statement.isExportEquals
+    }
+    if (ts.isExportDeclaration(statement) && !statement.isTypeOnly && statement.exportClause) {
+      if (ts.isNamespaceExport(statement.exportClause)) {
+        return statement.exportClause.name.text === 'default'
+      }
+      return statement.exportClause.elements.some(
+        (element) => !element.isTypeOnly && element.name.text === 'default'
+      )
+    }
+    const modifiers = ts.canHaveModifiers(statement) ? ts.getModifiers(statement) : undefined
+    return (
+      !ts.isInterfaceDeclaration(statement) &&
+      !ts.isTypeAliasDeclaration(statement) &&
+      modifiers?.some((modifier) => modifier.kind === ts.SyntaxKind.DeclareKeyword) !== true &&
+      modifiers?.some((modifier) => modifier.kind === ts.SyntaxKind.ExportKeyword) === true &&
+      modifiers.some((modifier) => modifier.kind === ts.SyntaxKind.DefaultKeyword)
+    )
+  })
+}
+
+function isInvalidRouteModule(path: string, source: string): boolean {
+  return (
+    isPlatformSpecificApiRoute(path) ||
+    (!isNonScreenExpoModule(path) && !hasDefaultExport(path, source))
+  )
+}
+
+describe('Expo route module boundary', () => {
+  it('allows Expo modules that are not screen routes', () => {
+    expect(isNonScreenExpoModule(join(appDirectory, 'health+api.ts'))).toBe(true)
+    expect(isNonScreenExpoModule(join(appDirectory, 'health+api.ios.ts'))).toBe(false)
+    expect(isNonScreenExpoModule(join(appDirectory, '+html.tsx'))).toBe(true)
+    expect(isNonScreenExpoModule(join(appDirectory, '+middleware.ts'))).toBe(true)
+    expect(isNonScreenExpoModule(join(appDirectory, '+native-intent.ts'))).toBe(true)
+    expect(isNonScreenExpoModule(join(appDirectory, 'nested', '+middleware.ts'))).toBe(false)
+  })
+
+  it('recognizes syntax-level default exports', () => {
+    expect(hasDefaultExport('route.tsx', 'export default function Route() {}')).toBe(true)
+    expect(
+      hasDefaultExport('route.jsx', 'export default function Route() { return <View /> }')
+    ).toBe(true)
+    expect(hasDefaultExport('route.ts', "export { default } from './route-screen'")).toBe(true)
+    expect(hasDefaultExport('route.ts', "export { Route as default } from './route-screen'")).toBe(
+      true
+    )
+    expect(hasDefaultExport('support.ts', '// export default')).toBe(false)
+    expect(hasDefaultExport('support.ts', "const marker = 'export default'")).toBe(false)
+    expect(hasDefaultExport('support.ts', 'export default interface Support {}')).toBe(false)
+    expect(
+      hasDefaultExport('support.ts', "export type { Support as default } from './types'")
+    ).toBe(false)
+  })
+
+  it('rejects platform-specific API routes even with a default export', () => {
+    expect(isPlatformSpecificApiRoute(join(appDirectory, 'health+api.ts'))).toBe(false)
+    for (const platform of ['android', 'ios', 'native', 'web']) {
+      const path = join(appDirectory, `health+api.${platform}.ts`)
+      expect(isInvalidRouteModule(path, 'export default function Route() {}')).toBe(true)
+    }
+  })
+
+  it('keeps support modules outside the app route directory', () => {
+    const invalidRoutes = sourceFiles(appDirectory)
+      .filter((path) => routeSourceExtensions.has(extname(path)))
+      .filter((path) => isInvalidRouteModule(path, readFileSync(path, 'utf8')))
+      .map((path) => relative(appDirectory, path))
+
+    expect(invalidRoutes).toEqual([])
+  })
+})
diff --git a/mobile/src/session/MobileBrowserTabActionSheet.tsx b/mobile/src/session/MobileBrowserTabActionSheet.tsx
index 655aa717ab9..5f605d1395c 100644
--- a/mobile/src/session/MobileBrowserTabActionSheet.tsx
+++ b/mobile/src/session/MobileBrowserTabActionSheet.tsx
@@ -1,5 +1,5 @@
 import { ChevronLeft, ChevronRight, RefreshCw } from 'lucide-react-native'
-import type { MobileSessionTab } from '../../app/h/[hostId]/session/mobile-session-route-types'
+import type { MobileSessionTab } from './mobile-session-route-types'
 import { ActionSheetModal, type ActionSheetAction } from '../components/ActionSheetModal'
 import { getMobileSessionTabTitle } from './mobile-terminal-tab-agent'
 
diff --git a/mobile/src/session/MobileSessionHeaderIconButton.tsx b/mobile/src/session/MobileSessionHeaderIconButton.tsx
index 68e1a1173a4..b1037bb958f 100644
--- a/mobile/src/session/MobileSessionHeaderIconButton.tsx
+++ b/mobile/src/session/MobileSessionHeaderIconButton.tsx
@@ -1,7 +1,7 @@
 import type { ComponentType } from 'react'
 import { Pressable } from 'react-native'
 import { colors } from '../theme/mobile-theme'
-import { styles } from '../../app/h/[hostId]/session/mobile-session-styles'
+import { styles } from './mobile-session-styles'
 
 type HeaderIconProps = {
   size?: number
diff --git a/mobile/app/h/[hostId]/session/QuickCommandsTabButton.tsx b/mobile/src/session/QuickCommandsTabButton.tsx
similarity index 92%
rename from mobile/app/h/[hostId]/session/QuickCommandsTabButton.tsx
rename to mobile/src/session/QuickCommandsTabButton.tsx
index 5faebb7691d..364a35daf75 100644
--- a/mobile/app/h/[hostId]/session/QuickCommandsTabButton.tsx
+++ b/mobile/src/session/QuickCommandsTabButton.tsx
@@ -1,7 +1,7 @@
 import { Pressable, View } from 'react-native'
 import { SquareChevronRight } from 'lucide-react-native'
 
-import { colors } from '../../../../src/theme/mobile-theme'
+import { colors } from '../theme/mobile-theme'
 import { styles } from './mobile-session-styles'
 
 type Props = {
diff --git a/mobile/src/session/mobile-bulk-close-sheet-actions.ts b/mobile/src/session/mobile-bulk-close-sheet-actions.ts
index 8565575fe08..68dee5c2af3 100644
--- a/mobile/src/session/mobile-bulk-close-sheet-actions.ts
+++ b/mobile/src/session/mobile-bulk-close-sheet-actions.ts
@@ -1,7 +1,4 @@
-import type {
-  MarkdownDocState,
-  MobileSessionTab
-} from '../../app/h/[hostId]/session/mobile-session-route-types'
+import type { MarkdownDocState, MobileSessionTab } from './mobile-session-route-types'
 import type { ActionSheetAction } from '../components/ActionSheetModal'
 import {
   BULK_TAB_CLOSE_ACTIONS,
diff --git a/mobile/app/h/[hostId]/session/mobile-session-command-input-styles.ts b/mobile/src/session/mobile-session-command-input-styles.ts
similarity index 98%
rename from mobile/app/h/[hostId]/session/mobile-session-command-input-styles.ts
rename to mobile/src/session/mobile-session-command-input-styles.ts
index 1bb852c4218..b19c13a502e 100644
--- a/mobile/app/h/[hostId]/session/mobile-session-command-input-styles.ts
+++ b/mobile/src/session/mobile-session-command-input-styles.ts
@@ -1,6 +1,6 @@
 import { StyleSheet } from 'react-native'
 
-import { colors, spacing, radii, typography } from '../../../../src/theme/mobile-theme'
+import { colors, spacing, radii, typography } from '../theme/mobile-theme'
 
 export const mobileSessionCommandInputStyles = StyleSheet.create({
   createWarningBanner: {
diff --git a/mobile/app/h/[hostId]/session/mobile-session-frame-styles.ts b/mobile/src/session/mobile-session-frame-styles.ts
similarity index 97%
rename from mobile/app/h/[hostId]/session/mobile-session-frame-styles.ts
rename to mobile/src/session/mobile-session-frame-styles.ts
index 738632ba495..a02c14be014 100644
--- a/mobile/app/h/[hostId]/session/mobile-session-frame-styles.ts
+++ b/mobile/src/session/mobile-session-frame-styles.ts
@@ -1,6 +1,6 @@
 import { StyleSheet } from 'react-native'
 
-import { colors, spacing, radii, typography } from '../../../../src/theme/mobile-theme'
+import { colors, spacing, radii, typography } from '../theme/mobile-theme'
 
 export const mobileSessionFrameStyles = StyleSheet.create({
   container: {
diff --git a/mobile/app/h/[hostId]/session/mobile-session-reader-styles.ts b/mobile/src/session/mobile-session-reader-styles.ts
similarity index 97%
rename from mobile/app/h/[hostId]/session/mobile-session-reader-styles.ts
rename to mobile/src/session/mobile-session-reader-styles.ts
index aba5340ec7a..eedd47d328b 100644
--- a/mobile/app/h/[hostId]/session/mobile-session-reader-styles.ts
+++ b/mobile/src/session/mobile-session-reader-styles.ts
@@ -1,6 +1,6 @@
 import { Platform, StyleSheet } from 'react-native'
 
-import { colors, spacing, radii, typography } from '../../../../src/theme/mobile-theme'
+import { colors, spacing, radii, typography } from '../theme/mobile-theme'
 
 export const mobileSessionReaderStyles = StyleSheet.create({
   markdownTextInput: {
diff --git a/mobile/app/h/[hostId]/session/mobile-session-review-comment-styles.ts b/mobile/src/session/mobile-session-review-comment-styles.ts
similarity index 98%
rename from mobile/app/h/[hostId]/session/mobile-session-review-comment-styles.ts
rename to mobile/src/session/mobile-session-review-comment-styles.ts
index b9d19578b83..8d8b2d11ccd 100644
--- a/mobile/app/h/[hostId]/session/mobile-session-review-comment-styles.ts
+++ b/mobile/src/session/mobile-session-review-comment-styles.ts
@@ -1,6 +1,6 @@
 import { StyleSheet } from 'react-native'
 
-import { colors, spacing, radii, typography } from '../../../../src/theme/mobile-theme'
+import { colors, spacing, radii, typography } from '../theme/mobile-theme'
 
 export const mobileSessionReviewCommentStyles = StyleSheet.create({
   diffCommentAddButton: {
diff --git a/mobile/app/h/[hostId]/session/mobile-session-route-types.ts b/mobile/src/session/mobile-session-route-types.ts
similarity index 85%
rename from mobile/app/h/[hostId]/session/mobile-session-route-types.ts
rename to mobile/src/session/mobile-session-route-types.ts
index c5a94e9d38f..7e74a5d04c0 100644
--- a/mobile/app/h/[hostId]/session/mobile-session-route-types.ts
+++ b/mobile/src/session/mobile-session-route-types.ts
@@ -1,13 +1,10 @@
-import type { MobileBrowserTab } from '../../../../src/browser/MobileBrowserPane'
-import type { MobileTerminalTheme } from '../../../../src/terminal/terminal-webview-contract'
-import type { MobileDiffLine } from '../../../../src/session/mobile-diff-lines'
-import type {
-  MobileHighlightedDiffLine,
-  MobileSyntaxSegment
-} from '../../../../src/session/mobile-file-syntax'
-import type { TerminalRecord } from '../../../../src/session/mobile-terminal-records'
-import type { DiffComment, TuiAgent } from '../../../../../src/shared/types'
-import type { AgentStatusEntry } from '../../../../../src/shared/agent-status-types'
+import type { DiffComment, TuiAgent } from '../../../src/shared/types'
+import type { AgentStatusEntry } from '../../../src/shared/agent-status-types'
+import type { MobileBrowserTab } from '../browser/MobileBrowserPane'
+import type { MobileTerminalTheme } from '../terminal/terminal-webview-contract'
+import type { MobileDiffLine } from './mobile-diff-lines'
+import type { MobileHighlightedDiffLine, MobileSyntaxSegment } from './mobile-file-syntax'
+import type { TerminalRecord } from './mobile-terminal-records'
 
 export type Terminal = TerminalRecord
 
diff --git a/mobile/app/h/[hostId]/session/mobile-session-styles.ts b/mobile/src/session/mobile-session-styles.ts
similarity index 100%
rename from mobile/app/h/[hostId]/session/mobile-session-styles.ts
rename to mobile/src/session/mobile-session-styles.ts
diff --git a/mobile/src/session/mobile-terminal-tab-agent.test.ts b/mobile/src/session/mobile-terminal-tab-agent.test.ts
index fcc7452e989..8449f988e24 100644
--- a/mobile/src/session/mobile-terminal-tab-agent.test.ts
+++ b/mobile/src/session/mobile-terminal-tab-agent.test.ts
@@ -1,7 +1,7 @@
 import { describe, expect, it } from 'vitest'
 import type { AgentStatusEntry } from '../../../src/shared/agent-status-types'
 import type { TuiAgent } from '../../../src/shared/types'
-import type { MobileSessionTab } from '../../app/h/[hostId]/session/mobile-session-route-types'
+import type { MobileSessionTab } from './mobile-session-route-types'
 import {
   getMobileSessionTabTitle,
   resolveMobileTerminalTabAgentId
diff --git a/mobile/src/session/mobile-terminal-tab-agent.ts b/mobile/src/session/mobile-terminal-tab-agent.ts
index 1ca19521b32..731d5bf4a24 100644
--- a/mobile/src/session/mobile-terminal-tab-agent.ts
+++ b/mobile/src/session/mobile-terminal-tab-agent.ts
@@ -3,7 +3,7 @@ import { resolveExplicitTerminalTitleAgentType } from '../../../src/shared/termi
 import type { AgentStatusEntry } from '../../../src/shared/agent-status-types'
 import type { TuiAgent } from '../../../src/shared/types'
 import { isBlankBrowserUrl } from '../browser/browser-url'
-import type { MobileSessionTab } from '../../app/h/[hostId]/session/mobile-session-route-types'
+import type { MobileSessionTab } from './mobile-session-route-types'
 
 // Why: tab identity + title cleaning uses the same shared glyph/label maps as
 // desktop, so the two platforms do not drift on which titles identify agents.
diff --git a/mobile/src/terminal/terminal-live-input-affordance.test.ts b/mobile/src/terminal/terminal-live-input-affordance.test.ts
index cc681e2056e..0125cb053e6 100644
--- a/mobile/src/terminal/terminal-live-input-affordance.test.ts
+++ b/mobile/src/terminal/terminal-live-input-affordance.test.ts
@@ -10,7 +10,7 @@ const liveInputStatusSource = readFileSync(
   'utf8'
 )
 const commandInputStylesSource = readFileSync(
-  new URL('../../app/h/[hostId]/session/mobile-session-command-input-styles.ts', import.meta.url),
+  new URL('../session/mobile-session-command-input-styles.ts', import.meta.url),
   'utf8'
 )
 const liveInputFocusSource = readFileSync(