diff --git a/src/main/claude/claude-folder-trust-file-wsl-guest.test.ts b/src/main/claude/claude-folder-trust-file-wsl-guest.test.ts
new file mode 100644
index 00000000000..e831b7c08ee
--- /dev/null
+++ b/src/main/claude/claude-folder-trust-file-wsl-guest.test.ts
@@ -0,0 +1,133 @@
+import type * as NodeFs from 'node:fs'
+import {
+  chmodSync,
+  mkdirSync,
+  mkdtempSync,
+  readdirSync,
+  readFileSync,
+  realpathSync,
+  rmSync,
+  statSync,
+  writeFileSync
+} from 'node:fs'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import type { WslResult, WslSpec } from '../wsl/wsl-runner'
+import { grantClaudeFolderTrust } from './claude-folder-trust-file'
+
+const { DISTRO, GUEST_PREFIX, guest } = vi.hoisted(() => ({
+  DISTRO: 'Ubuntu-24.04',
+  GUEST_PREFIX: '//wsl.localhost/Ubuntu-24.04',
+  guest: { root: '' }
+}))
+
+function toGuestDisk(path: string): string {
+  return path.startsWith(GUEST_PREFIX) ? `${guest.root}${path.slice(GUEST_PREFIX.length)}` : path
+}
+
+// Why: models Windows Node over \\wsl.localhost: a synthetic 0o666 mode, chmod that cannot reach
+// the guest bits, and new files at the guest's default 0644 whatever mode was requested.
+vi.mock('node:fs', async (importOriginal) => {
+  const actual = await importOriginal<typeof NodeFs>()
+  const onGuest = (path: unknown): path is string =>
+    typeof path === 'string' && path.startsWith(GUEST_PREFIX)
+  const disk = (path: string): string => `${guest.root}${path.slice(GUEST_PREFIX.length)}`
+  const windowsView = (stats: NodeFs.Stats): NodeFs.Stats =>
+    Object.assign(stats, { mode: (stats.mode & ~0o777) | 0o666 })
+  return {
+    ...actual,
+    existsSync: (path: string) => actual.existsSync(onGuest(path) ? disk(path) : path),
+    lstatSync: (path: string) =>
+      onGuest(path) ? windowsView(actual.lstatSync(disk(path))) : actual.lstatSync(path),
+    statSync: (path: string) =>
+      onGuest(path) ? windowsView(actual.statSync(disk(path))) : actual.statSync(path),
+    realpathSync: (path: string) =>
+      onGuest(path)
+        ? `${GUEST_PREFIX}${actual.realpathSync(disk(path)).slice(guest.root.length)}`
+        : actual.realpathSync(path),
+    readFileSync: (path: string, options: BufferEncoding) =>
+      actual.readFileSync(onGuest(path) ? disk(path) : path, options),
+    writeFileSync: (path: string, data: string, options?: NodeFs.WriteFileOptions) => {
+      if (!onGuest(path)) {
+        return actual.writeFileSync(path, data, options)
+      }
+      const created = !actual.existsSync(disk(path))
+      const flag = typeof options === 'object' && options ? options.flag : undefined
+      actual.writeFileSync(disk(path), data, { flag })
+      if (created) {
+        actual.chmodSync(disk(path), 0o644)
+      }
+    },
+    chmodSync: (path: string, mode: number) =>
+      onGuest(path) ? undefined : actual.chmodSync(path, mode),
+    renameSync: (from: string, to: string) =>
+      actual.renameSync(onGuest(from) ? disk(from) : from, onGuest(to) ? disk(to) : to),
+    rmSync: (path: string, options?: NodeFs.RmOptions) =>
+      actual.rmSync(onGuest(path) ? disk(path) : path, options)
+  }
+})
+
+vi.mock('proper-lockfile', () => ({
+  lock: vi.fn(async () => async () => {})
+}))
+
+const runWslProcess = vi.hoisted(() => vi.fn<(spec: WslSpec) => Promise<WslResult>>())
+vi.mock('../wsl/wsl-runner', () => ({ runWslProcess }))
+
+/** Runs `chmod --reference=<from> -- <to>` as the guest would. */
+async function guestChmod(spec: WslSpec): Promise<WslResult> {
+  const [reference, separator, target] = spec.args ?? []
+  expect(spec).toMatchObject({ distro: DISTRO, loginPath: 'none', program: 'chmod' })
+  expect(separator).toBe('--')
+  const from = `${guest.root}${reference.replace(/^--reference=/, '')}`
+  chmodSync(`${guest.root}${target}`, statSync(from).mode & 0o7777)
+  return { environmentResolved: true, code: 0, stdout: '', stderr: '', timedOut: false }
+}
+
+const originalPlatform = process.platform
+
+describe.skipIf(originalPlatform === 'win32')('grantClaudeFolderTrust on a WSL guest file', () => {
+  const guestFile = `${GUEST_PREFIX}/home/u/.claude.json`
+
+  beforeEach(() => {
+    guest.root = realpathSync(mkdtempSync(join(tmpdir(), 'orca-claude-trust-guest-')))
+    mkdirSync(join(guest.root, 'home/u'), { recursive: true })
+    writeFileSync(toGuestDisk(guestFile), JSON.stringify({ theme: 'dark' }))
+    chmodSync(toGuestDisk(guestFile), 0o600)
+    runWslProcess.mockReset().mockImplementation(guestChmod)
+    Object.defineProperty(process, 'platform', { configurable: true, value: 'win32' })
+  })
+
+  afterEach(() => {
+    Object.defineProperty(process, 'platform', { configurable: true, value: originalPlatform })
+    rmSync(guest.root, { recursive: true, force: true })
+  })
+
+  it("keeps the guest file's owner-only mode through the rewrite", async () => {
+    await expect(
+      grantClaudeFolderTrust({ configFile: guestFile, folderKeys: ['/home/u/wt'] })
+    ).resolves.toBe('granted')
+    expect(statSync(toGuestDisk(guestFile)).mode & 0o777).toBe(0o600)
+    expect(JSON.parse(readFileSync(toGuestDisk(guestFile), 'utf-8'))).toEqual({
+      theme: 'dark',
+      projects: { '/home/u/wt': { hasTrustDialogAccepted: true } }
+    })
+  })
+
+  it('leaves the file untouched when the guest cannot copy its mode', async () => {
+    runWslProcess.mockResolvedValue({
+      environmentResolved: true,
+      code: 1,
+      stdout: '',
+      stderr: "chmod: unrecognized option '--reference'",
+      timedOut: false
+    })
+    await expect(
+      grantClaudeFolderTrust({ configFile: guestFile, folderKeys: ['/home/u/wt'] })
+    ).rejects.toThrow(/guest mode/)
+    expect(readFileSync(toGuestDisk(guestFile), 'utf-8')).toBe(JSON.stringify({ theme: 'dark' }))
+    expect(statSync(toGuestDisk(guestFile)).mode & 0o777).toBe(0o600)
+    expect(readdirSync(join(guest.root, 'home/u'))).toEqual(['.claude.json'])
+  })
+})
diff --git a/src/main/claude/claude-folder-trust-file.test.ts b/src/main/claude/claude-folder-trust-file.test.ts
index 1c876be1457..456e8938cb6 100644
--- a/src/main/claude/claude-folder-trust-file.test.ts
+++ b/src/main/claude/claude-folder-trust-file.test.ts
@@ -4,6 +4,7 @@ import {
   lstatSync,
   mkdirSync,
   mkdtempSync,
+  readdirSync,
   readFileSync,
   realpathSync,
   rmSync,
@@ -178,6 +179,8 @@ describe('grantClaudeFolderTrust', () => {
     )
     expect(readConfig(file)).toEqual({})
     expect(existsSync(lockDir)).toBe(true)
+    // Why: the replacement file is created before the lock, so a skipped write must remove it.
+    expect(readdirSync(root).sort()).toEqual(['.claude.json', '.claude.json.lock'])
   })
 
   it('updates a symlinked config through its target and keeps the link', async () => {
diff --git a/src/main/claude/claude-folder-trust-file.ts b/src/main/claude/claude-folder-trust-file.ts
index ca35351eeb0..5ec9bccebcc 100644
--- a/src/main/claude/claude-folder-trust-file.ts
+++ b/src/main/claude/claude-folder-trust-file.ts
@@ -15,6 +15,7 @@ import { lock } from 'proper-lockfile'
 import { renameFileWithWindowsRetry } from '../codex-accounts/fs-utils'
 import { runKeyedSerializedOperation } from '../cli/keyed-promise-queue'
 import { parseWslUncPath } from '../../shared/wsl-paths'
+import { runWslProcess } from '../wsl/wsl-runner'
 import type { ClaudeRuntimeAuthPreparation } from '../claude-accounts/runtime-auth/runtime-auth-types'
 
 export type ClaudeTrustPathStyle = 'posix' | 'win32'
@@ -144,20 +145,52 @@ function readConfigObject(target: string): Record<string, unknown> | null {
   }
 }
 
-function writeConfigAtomically(target: string, config: Record<string, unknown>): void {
-  const mode = statSync(target).mode & 0o777
-  const tmpPath = `${target}.orca-trust-${randomUUID()}.tmp`
+type ReplacementFile = { target: string; path: string }
+
+/**
+ * Creates an empty file beside `target` that already has `target`'s permission bits, so
+ * renaming it over `target` can never widen them.
+ */
+async function createReplacementFile(target: string): Promise<ReplacementFile> {
+  const suffix = `.orca-trust-${randomUUID()}.tmp`
+  const path = `${target}${suffix}`
+  const guestFile = parseWslUncPath(target)
   try {
-    writeFileSync(tmpPath, `${JSON.stringify(config, null, 2)}\n`, { encoding: 'utf-8', mode })
-    if (process.platform !== 'win32') {
-      // Why: umask may narrow the requested mode; the replacement must match the original exactly.
-      chmodSync(tmpPath, mode)
+    if (guestFile) {
+      // Why: Windows sees a synthetic 0o666 for a guest file and cannot set its bits, and the
+      // guest gives a file made through \\wsl.localhost its default 0644; only the guest can copy them.
+      writeFileSync(path, '', { flag: 'wx' })
+      const copied = await runWslProcess({
+        distro: guestFile.distro,
+        loginPath: 'none',
+        program: 'chmod',
+        args: [`--reference=${guestFile.linuxPath}`, '--', `${guestFile.linuxPath}${suffix}`]
+      })
+      if (copied.code !== 0) {
+        throw new Error(`could not copy the guest mode of ${target}: ${copied.stderr.trim()}`)
+      }
+    } else {
+      const mode = statSync(target).mode & 0o777
+      writeFileSync(path, '', { flag: 'wx', mode })
+      if (process.platform !== 'win32') {
+        // Why: umask may narrow the requested mode; the replacement must match the original exactly.
+        chmodSync(path, mode)
+      }
     }
-    renameFileWithWindowsRetry(tmpPath, target)
   } catch (error) {
-    rmSync(tmpPath, { force: true })
+    rmSync(path, { force: true })
     throw error
   }
+  return { target, path }
+}
+
+function replaceConfig(replacement: ReplacementFile, config: Record<string, unknown>): void {
+  // Why r+: reopening without create/truncate keeps the mode the replacement was given.
+  writeFileSync(replacement.path, `${JSON.stringify(config, null, 2)}\n`, {
+    encoding: 'utf-8',
+    flag: 'r+'
+  })
+  renameFileWithWindowsRetry(replacement.path, replacement.target)
 }
 
 /**
@@ -188,37 +221,49 @@ async function grantClaudeFolderTrustNow(args: {
     return planned === 'refuse' ? 'unreadable' : 'unchanged'
   }
 
-  let release: () => Promise<void>
+  // Why before the lock: a WSL guest's mode takes a guest process to copy, and Claude's
+  // lock should stay held only for the synchronous read → rename below.
+  const replacement = await createReplacementFile(probe.path)
   try {
-    release = await lock(args.configFile, {
-      // Why: Claude locks the literal `<file>.lock`, not a realpath'd one.
-      lockfilePath: `${args.configFile}.lock`,
-      realpath: false,
-      stale: NEVER_STALE_MS,
-      retries: LOCK_RETRIES,
-      onCompromised: () => {}
-    })
-  } catch {
-    return 'locked'
-  }
-  try {
-    // Why: read → rename stays synchronous so Orca's own synchronous auth writer to
-    // this file cannot interleave and lose an update.
-    const current = readConfigAt(resolveConfigTarget(args.configFile))
-    if (typeof current === 'string') {
-      return current
+    let release: () => Promise<void>
+    try {
+      release = await lock(args.configFile, {
+        // Why: Claude locks the literal `<file>.lock`, not a realpath'd one.
+        lockfilePath: `${args.configFile}.lock`,
+        realpath: false,
+        stale: NEVER_STALE_MS,
+        retries: LOCK_RETRIES,
+        onCompromised: () => {}
+      })
+    } catch {
+      return 'locked'
     }
-    const change = applyClaudeFolderTrust(current.config, args.folderKeys)
-    if (change.kind === 'refuse') {
-      return 'unreadable'
+    try {
+      // Why: read → rename stays synchronous so Orca's own synchronous auth writer to
+      // this file cannot interleave and lose an update.
+      const current = readConfigAt(resolveConfigTarget(args.configFile))
+      if (typeof current === 'string') {
+        return current
+      }
+      // Why: a link retargeted since the replacement copied its mode means Claude asks.
+      if (current.path !== replacement.target) {
+        return 'unreadable'
+      }
+      const change = applyClaudeFolderTrust(current.config, args.folderKeys)
+      if (change.kind === 'refuse') {
+        return 'unreadable'
+      }
+      if (change.kind === 'unchanged') {
+        return 'unchanged'
+      }
+      replaceConfig(replacement, change.config)
+      return 'granted'
+    } finally {
+      await release().catch(() => {})
     }
-    if (change.kind === 'unchanged') {
-      return 'unchanged'
-    }
-    writeConfigAtomically(current.path, change.config)
-    return 'granted'
   } finally {
-    await release().catch(() => {})
+    // Why: a no-op after the rename; otherwise the unused replacement must not linger.
+    rmSync(replacement.path, { force: true })
   }
 }