diff --git a/apps/buddy/platform/windows/__tests__/sandboxPathPermissions.native.spec.ts b/apps/buddy/platform/windows/__tests__/sandboxPathPermissions.native.spec.ts
new file mode 100644
index 000000000..c71d02c5b
--- /dev/null
+++ b/apps/buddy/platform/windows/__tests__/sandboxPathPermissions.native.spec.ts
@@ -0,0 +1,136 @@
+import { Buffer } from 'node:buffer'
+import { execFile } from 'node:child_process'
+import { mkdir, mkdtemp, readFile, realpath, rename, rm } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import process from 'node:process'
+import { promisify } from 'node:util'
+import { describe, expect, it } from 'vitest'
+import { createWindowsSandboxPolicy } from '../../../service/src/sandbox/backends/windows/createPolicy'
+import { inspectSandboxPath } from '../../../service/src/sandbox/sandboxFilesystemPolicy'
+import { SHELL_SANDBOX_BACKEND } from '../../../shared/platform/identifiers'
+
+const execute = promisify(execFile)
+
+async function powershell(root: string, script: string) {
+  const executable = join(process.env.SystemRoot ?? 'C:\\Windows', 'System32', 'WindowsPowerShell', 'v1.0', 'powershell.exe')
+  return execute(executable, [
+    '-NoLogo',
+    '-NoProfile',
+    '-NonInteractive',
+    '-EncodedCommand',
+    Buffer.from(`$ErrorActionPreference='Stop';$ProgressPreference='SilentlyContinue';$env:PSModulePath=Join-Path $PSHOME 'Modules';$root=$env:LEXORA_ACL_TEST_ROOT;${script}`, 'utf16le').toString('base64'),
+  ], { windowsHide: true, timeout: 30_000, env: { ...process.env, LEXORA_ACL_TEST_ROOT: root } })
+}
+
+async function withDeniedPath(run: (fixture: { root: string, denied: string, input: Parameters<typeof createWindowsSandboxPolicy>[0] }) => Promise<void>) {
+  const root = await realpath(await mkdtemp(join(tmpdir(), 'buddy-path-acl-')))
+  const parent = join(root, 'denied')
+  const denied = join(parent, 'child')
+  try {
+    await Promise.all(['workspace', 'home', 'shell', 'system/System32', 'search', 'normal-a', 'normal-b', 'denied/child', 'denied/System32'].map(path => mkdir(join(root, path), { recursive: true })))
+    await powershell(root, `
+      $identity=[Security.Principal.WindowsIdentity]::GetCurrent()
+      if([Security.Principal.WindowsPrincipal]::new($identity).IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)){throw 'An ordinary user token is required'}
+      $paths=@('denied','denied\\child','denied\\System32')
+      $saved=@($paths|ForEach-Object {@{relative=$_;sddl=(Get-Acl -LiteralPath (Join-Path $root $_)).Sddl}})
+      ConvertTo-Json -InputObject $saved|Set-Content -LiteralPath (Join-Path $root 'acl.json') -Encoding utf8
+      $path=Join-Path $root 'denied'
+      $acl=Get-Acl -LiteralPath $path
+      $rule=[Security.AccessControl.FileSystemAccessRule]::new($identity.User,[Security.AccessControl.FileSystemRights]::ReadAndExecute,[Security.AccessControl.InheritanceFlags]'ContainerInherit,ObjectInherit',[Security.AccessControl.PropagationFlags]::None,[Security.AccessControl.AccessControlType]::Deny)
+      $acl.AddAccessRule($rule)
+      Set-Acl -LiteralPath $path -AclObject $acl
+    `)
+    expect(await realpath(parent)).toBe(parent)
+    await expect(realpath(denied)).rejects.toMatchObject({ code: expect.stringMatching(/^(?:EPERM|EACCES)$/) })
+    await expect(realpath(join(parent, 'System32'))).rejects.toMatchObject({ code: expect.stringMatching(/^(?:EPERM|EACCES)$/) })
+    const workspace = join(root, 'workspace')
+    await run({
+      root,
+      denied,
+      input: {
+        roots: [workspace],
+        workspaceRoots: [workspace],
+        resourceReadRoots: [],
+        additionalDirectories: [],
+        cwd: workspace,
+        home: join(root, 'home'),
+        protectedRoots: [],
+        sensitiveRoots: [],
+        readOnly: false,
+        backend: {
+          kind: SHELL_SANDBOX_BACKEND.Windows,
+          executable: join(root, 'unused-sandbox.exe'),
+          shell: join(root, 'shell', 'pwsh.exe'),
+          systemRoot: join(root, 'system'),
+          protectionScope: join(root, 'home'),
+        },
+        searchDirectory: join(root, 'search'),
+        path: [join(root, 'normal-a'), denied, join(root, 'normal-b')].join(';'),
+      },
+    })
+  }
+  finally {
+    const saved = await readFile(join(root, 'acl.json'), 'utf8').catch((error: NodeJS.ErrnoException) => {
+      if (error.code !== 'ENOENT')
+        throw error
+      return undefined
+    })
+    if (saved) {
+      await powershell(root, `
+        $saved=Get-Content -Raw -LiteralPath (Join-Path $root 'acl.json')|ConvertFrom-Json
+        $acl=[Security.AccessControl.DirectorySecurity]::new()
+        $acl.SetSecurityDescriptorSddlForm($saved[0].sddl,[Security.AccessControl.AccessControlSections]::Access)
+        Set-Acl -LiteralPath (Join-Path $root 'denied') -AclObject $acl
+        foreach($entry in $saved){
+          if((Get-Acl -LiteralPath (Join-Path $root $entry.relative)).Sddl -cne $entry.sddl){throw 'Fixture SDDL was not restored'}
+        }
+      `)
+      expect(await realpath(denied)).toBe(denied)
+    }
+    await rm(root, { recursive: true, force: true })
+  }
+}
+
+describe.skipIf(process.platform !== 'win32')('windows sandbox policy with real ACL denial', () => {
+  it('omits an inaccessible optional PATH child while retaining readable tools and their identities', async () => {
+    await withDeniedPath(async ({ root, denied, input }) => {
+      const policy = await createWindowsSandboxPolicy(input, new AbortController().signal)
+      const expected = ['shell', 'system/System32', 'search', 'normal-a', 'normal-b'].map(path => join(root, path))
+      expect(policy.path.split(';')).toEqual(expected)
+      expect(policy.grants.some(grant => grant.path === denied)).toBe(false)
+      expect(policy.grants.filter(grant => grant.access === 'read')).toEqual(await Promise.all(expected.map(path => inspectSandboxPath(path, 'read'))))
+      expect(policy.grants.filter(grant => grant.access === 'write').map(grant => grant.path)).toEqual(input.roots)
+    })
+  }, 60_000)
+
+  it('fails closed for inaccessible shell, System32, search, workspace, protected and sensitive roots', async () => {
+    await withDeniedPath(async ({ root, denied, input }) => {
+      const cases: Partial<typeof input>[] = [
+        { backend: { ...input.backend, shell: join(denied, 'pwsh.exe') } },
+        { backend: { ...input.backend, systemRoot: join(root, 'denied') } },
+        { searchDirectory: denied },
+        { roots: [denied], workspaceRoots: [denied], cwd: denied },
+        { protectedRoots: [denied] },
+        { sensitiveRoots: [denied] },
+      ]
+      for (const changes of cases)
+        await expect(createWindowsSandboxPolicy({ ...input, ...changes }, new AbortController().signal)).rejects.toMatchObject({ code: expect.stringMatching(/^(?:EPERM|EACCES)$/) })
+    })
+  }, 60_000)
+
+  it('does not swallow a replaced explicit grant identity when PATH also contains an inaccessible child', async () => {
+    await withDeniedPath(async ({ root, input }) => {
+      const directory = join(root, 'additional')
+      await mkdir(directory)
+      const grant = await inspectSandboxPath(directory, 'read')
+      await rename(directory, join(root, 'original-additional'))
+      await mkdir(directory)
+      expect((await inspectSandboxPath(directory, 'read')).inode).not.toBe(grant.inode)
+      await expect(createWindowsSandboxPolicy({
+        ...input,
+        additionalDirectories: [{ path: grant.path, access: 'read', device: grant.device, inode: grant.inode }],
+      }, new AbortController().signal)).rejects.toMatchObject({ code: 'SANDBOX_DIRECTORY_CHANGED' })
+    })
+  }, 60_000)
+})
diff --git a/apps/buddy/platform/windows/__tests__/sandboxPolicy.spec.ts b/apps/buddy/platform/windows/__tests__/sandboxPolicy.spec.ts
index 71d51d688..7242bb504 100644
--- a/apps/buddy/platform/windows/__tests__/sandboxPolicy.spec.ts
+++ b/apps/buddy/platform/windows/__tests__/sandboxPolicy.spec.ts
@@ -1,9 +1,11 @@
-import { describe, expect, it, vi } from 'vitest'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
 import { resolveSensitivePathRoots } from '../../../service/src/permissions/sensitivePaths'
 import { createWindowsSandboxPolicy } from '../../../service/src/sandbox/backends/windows/createPolicy'
 import { sandboxCommandSchema, sandboxProcessInputSchema } from '../../../shared/permissions/shellSandbox'
 import { SHELL_SANDBOX_BACKEND } from '../../../shared/platform/identifiers'
 
+const failures = vi.hoisted(() => ({ realpath: new Map<string, string>(), stat: new Map<string, string>() }))
+
 vi.mock('../../currentPlatform', async () => {
   const { resolveBuddyPlatform } = await import('../../../shared/platform')
   return { currentPlatform: resolveBuddyPlatform('win32') }
@@ -13,8 +15,18 @@ vi.mock('node:path', async (importOriginal) => {
   return { ...actual, ...actual.win32 }
 })
 vi.mock('node:fs/promises', () => ({
-  realpath: async (path: string) => path === 'Z:\\MappedTools' ? '\\\\server\\tools' : path,
-  stat: async () => ({ isDirectory: () => true, dev: 1n, ino: 2n }),
+  realpath: async (path: string) => {
+    const code = failures.realpath.get(path)
+    if (code)
+      throw Object.assign(new Error(code), { code })
+    return path === 'Z:\\MappedTools' ? '\\\\server\\tools' : path
+  },
+  stat: async (path: string) => {
+    const code = failures.stat.get(path)
+    if (code)
+      throw Object.assign(new Error(code), { code })
+    return { isDirectory: () => true, dev: 1n, ino: 2n }
+  },
 }))
 
 const home = 'C:\\Users\\Fixture'
@@ -37,6 +49,11 @@ const input = {
 }
 
 describe('windows sandbox policy assembly', () => {
+  beforeEach(() => {
+    failures.realpath.clear()
+    failures.stat.clear()
+  })
+
   it('retains local PATH tools without turning UNC or device paths into mandatory grants', async () => {
     const policy = await createWindowsSandboxPolicy({ ...input, path: '"D:\\Tools";\\\\server\\tools;//server/share;\\\\?\\C:\\tools;C:relative;\\root-relative;C:\\NUL\\..\\tools;Z:\\MappedTools' }, new AbortController().signal)
     expect(policy.path.split(';')).toEqual(['C:\\PowerShell', 'C:\\Windows\\System32', 'C:\\search', 'D:\\Tools'])
@@ -44,6 +61,37 @@ describe('windows sandbox policy assembly', () => {
     expect(sandboxCommandSchema.safeParse({ command: input.command, requestId: input.requestId, cwd: '\\\\server\\tools', roots: ['\\\\server\\tools'], readOnly: false }).success).toBe(false)
   })
 
+  it.each([
+    ['realpath', 'EPERM'],
+    ['realpath', 'EACCES'],
+    ['stat', 'EPERM'],
+    ['stat', 'EACCES'],
+  ] as const)('skips inaccessible optional PATH entries during %s (%s)', async (operation, code) => {
+    failures[operation].set('D:\\Locked', code)
+    const policy = await createWindowsSandboxPolicy({ ...input, path: 'D:\\Locked;D:\\Tools;D:\\Tools' }, new AbortController().signal)
+    expect(policy.path.split(';')).toEqual(['C:\\PowerShell', 'C:\\Windows\\System32', 'C:\\search', 'D:\\Tools'])
+    expect(policy.grants.filter(grant => grant.access === 'read').map(grant => grant.path)).toEqual(policy.path.split(';'))
+    expect(policy.grants.some(grant => grant.path === 'D:\\Locked')).toBe(false)
+  })
+
+  it.each(['realpath', 'stat'] as const)('retains required directory failures during %s', async (operation) => {
+    const required = ['C:\\workspace', 'C:\\PowerShell', 'C:\\Windows\\System32', 'C:\\search', 'D:\\Roaming\\gcloud', 'C:\\protected']
+    for (const path of required) {
+      failures[operation].set(path, 'EPERM')
+      await expect(createWindowsSandboxPolicy({ ...input, path: 'D:\\Tools', protectedRoots: ['C:\\protected'] }, new AbortController().signal))
+        .rejects
+        .toMatchObject({ code: 'EPERM' })
+      failures[operation].clear()
+    }
+  })
+
+  it.each(['realpath', 'stat'] as const)('does not swallow unexpected PATH IO errors during %s', async (operation) => {
+    failures[operation].set('D:\\Broken', 'EIO')
+    await expect(createWindowsSandboxPolicy({ ...input, path: 'D:\\Broken;D:\\Tools' }, new AbortController().signal))
+      .rejects
+      .toMatchObject({ code: 'EIO' })
+  })
+
   it('protects redirected credentials on another volume and rejects them as workspace roots', async () => {
     const policy = await createWindowsSandboxPolicy(input, new AbortController().signal)
     expect(policy.grants.filter(grant => grant.access === 'denyRead').map(grant => grant.path)).toEqual(expect.arrayContaining([
diff --git a/apps/buddy/service/src/sandbox/__tests__/shellSandbox.spec.ts b/apps/buddy/service/src/sandbox/__tests__/shellSandbox.spec.ts
index 2a2d1e99f..c5a12fd5c 100644
--- a/apps/buddy/service/src/sandbox/__tests__/shellSandbox.spec.ts
+++ b/apps/buddy/service/src/sandbox/__tests__/shellSandbox.spec.ts
@@ -1,7 +1,7 @@
 import type { SandboxProcessInput } from '../../../../shared/permissions/shellSandbox'
 import { Buffer } from 'node:buffer'
 import { randomUUID } from 'node:crypto'
-import { access, mkdir, mkdtemp, readFile, rm, stat, symlink, writeFile } from 'node:fs/promises'
+import { access, chmod, mkdir, mkdtemp, readFile, realpath, rm, stat, symlink, writeFile } from 'node:fs/promises'
 import { createServer } from 'node:http'
 import { createServer as createUnixServer } from 'node:net'
 import { homedir, tmpdir } from 'node:os'
@@ -108,6 +108,56 @@ describe.skipIf(process.platform !== 'linux')('linux shell enforcement', () => {
     expect(JSON.stringify(events)).not.toMatch(/synthetic-secret|example-allowed|printf/)
   }, 15_000)
 
+  it.skipIf(process.getuid?.() === 0)('executes a PATH tool past an inaccessible optional directory without expanding writes', async () => {
+    const blocked = join(directory, 'blocked')
+    const inaccessible = join(blocked, 'bin')
+    const tools = join(directory, 'tools')
+    await mkdir(inaccessible, { recursive: true })
+    await mkdir(tools)
+    const tool = join(tools, 'lexora-path-probe')
+    await writeFile(tool, '#!/bin/sh\nprintf PATH_TOOL_OK\n')
+    await chmod(tool, 0o755)
+    try {
+      await chmod(blocked, 0)
+      await expect(realpath(inaccessible)).rejects.toMatchObject({ code: 'EACCES' })
+      const { result, output } = await execute(`set -e; lexora-path-probe; printf created > path-result; ! sh -c ${quote(`printf changed > ${quote(join(outside, 'preserved'))}`)}`, {}, {
+        path: `${inaccessible}:${tools}:${input.path}`,
+      })
+      expect(result, output).toEqual({ ok: true, exitCode: 0 })
+      expect(output).toContain('PATH_TOOL_OK')
+      expect(await readFile(join(workspace, 'path-result'), 'utf8')).toBe('created')
+      expect(await readFile(join(outside, 'preserved'), 'utf8')).toBe('outside-preserved')
+    }
+    finally {
+      await chmod(blocked, 0o700)
+    }
+  }, 15_000)
+
+  it.skipIf(process.getuid?.() === 0)('rejects inaccessible required roots before the shell command can run', async () => {
+    const blocked = join(directory, 'blocked')
+    const inaccessible = join(blocked, 'required')
+    await mkdir(inaccessible, { recursive: true })
+    try {
+      await chmod(blocked, 0)
+      await expect(realpath(inaccessible)).rejects.toMatchObject({ code: 'EACCES' })
+      const required: Partial<SandboxProcessInput>[] = [
+        { cwd: inaccessible, roots: [inaccessible], workspaceRoots: [inaccessible] },
+        { protectedRoots: [inaccessible] },
+        { sensitiveRoots: [inaccessible] },
+        { searchDirectory: inaccessible },
+      ]
+      for (const overrides of required) {
+        const { result, output } = await execute('printf must-not-run > path-forbidden; printf unexpected-command', {}, overrides)
+        expect(result).toMatchObject({ ok: false })
+        expect(output).not.toContain('unexpected-command')
+        await expect(access(join(workspace, 'path-forbidden'))).rejects.toThrow()
+      }
+    }
+    finally {
+      await chmod(blocked, 0o700)
+    }
+  }, 15_000)
+
   it('recovers the native SRT command domain when final service persistence is lost', async () => {
     const identities: string[] = []
     const receiptDirectory = join(directory, 'receipts')
diff --git a/apps/buddy/service/src/sandbox/backends/srt/createPolicy.ts b/apps/buddy/service/src/sandbox/backends/srt/createPolicy.ts
index 2f4d7ecdf..ad89631cf 100644
--- a/apps/buddy/service/src/sandbox/backends/srt/createPolicy.ts
+++ b/apps/buddy/service/src/sandbox/backends/srt/createPolicy.ts
@@ -14,7 +14,7 @@ export async function createSandboxPolicy(input: SrtSandboxInput, signal: AbortS
   const { rg, srtRoot } = dependencies
   const system = dependencies.platform === OPERATING_SYSTEM.Linux ? await createLinuxSystemPolicy(dependencies) : createMacosSystemPolicy()
   const policy = await createSandboxFilesystemPolicy(input, signal)
-  const searchPaths = await existingSandboxPaths(input.path.split(delimiter).filter(path => path.startsWith('/')))
+  const searchPaths = input.path.split(delimiter).filter(path => path.startsWith('/'))
   const runtimePaths = await existingSandboxPaths([...system.readPaths, input.searchDirectory])
   const paths = (access: typeof policy[number]['access']) => policy.filter(grant => grant.access === access).map(grant => grant.path)
   return {
diff --git a/apps/buddy/service/src/sandbox/backends/windows/createPolicy.ts b/apps/buddy/service/src/sandbox/backends/windows/createPolicy.ts
index bdf5332af..815640ee8 100644
--- a/apps/buddy/service/src/sandbox/backends/windows/createPolicy.ts
+++ b/apps/buddy/service/src/sandbox/backends/windows/createPolicy.ts
@@ -9,18 +9,33 @@ type WindowsSandboxPolicyInput = SandboxFilesystemPolicyInput & Pick<SandboxBack
 
 export async function createWindowsSandboxPolicy(input: WindowsSandboxPolicyInput, signal: AbortSignal) {
   const grants = await createSandboxFilesystemPolicy(input, signal)
-  const paths: string[] = []
+  const roots = new Set(await existingSandboxPaths([dirname(input.backend.shell), join(input.backend.systemRoot, 'System32'), input.searchDirectory]))
+  for (const root of roots)
+    grants.push(await inspectSandboxPath(root, 'read'))
+
   for (const entry of input.path.split(';')) {
+    signal.throwIfAborted()
+    let path: string
     try {
-      const path = validateWindowsFilePath(entry.replace(/^"|"$/g, ''))
-      if (/^[a-z]:\\/i.test(path))
-        paths.push(path)
+      path = validateWindowsFilePath(entry.replace(/^"|"$/g, ''))
+    }
+    catch {
+      continue
+    }
+    if (!/^[a-z]:\\/i.test(path))
+      continue
+    try {
+      const [root] = await existingSandboxPaths([path])
+      if (!root || !/^[a-z]:\\/i.test(root) || roots.has(root))
+        continue
+      const grant = await inspectSandboxPath(root, 'read')
+      roots.add(root)
+      grants.push(grant)
+    }
+    catch (error) {
+      if (!error || typeof error !== 'object' || !('code' in error) || !['EPERM', 'EACCES'].includes(String(error.code)))
+        throw error
     }
-    catch {}
   }
-  const localPaths = (await existingSandboxPaths(paths)).filter(path => /^[a-z]:\\/i.test(path))
-  const roots = [...new Set([...await existingSandboxPaths([dirname(input.backend.shell), join(input.backend.systemRoot, 'System32'), input.searchDirectory]), ...localPaths])]
-  for (const root of roots)
-    grants.push(await inspectSandboxPath(root, 'read'))
-  return { grants, path: roots.join(';') }
+  return { grants, path: [...roots].join(';') }
 }