diff --git a/src/main/agent-hooks/installer-utils.ts b/src/main/agent-hooks/installer-utils.ts
index ac4abee9469..19c190b12d4 100644
--- a/src/main/agent-hooks/installer-utils.ts
+++ b/src/main/agent-hooks/installer-utils.ts
@@ -106,7 +106,7 @@ export function getSharedManagedScriptPath(scriptFileName: string): string {
   return join(homedir(), '.orca', 'agent-hooks', scriptFileName)
 }
 
-export { wrapPosixHookCommand } from './posix-hook-command'
+export { wrapPosixHookCommand, wrapPosixHookCommandForExec } from './posix-hook-command'
 
 export function quotePowerShellString(value: string): string {
   return `'${value.replaceAll("'", "''")}'`
diff --git a/src/main/agent-hooks/posix-hook-command.ts b/src/main/agent-hooks/posix-hook-command.ts
index 23d8f1acba8..35e7ee475bd 100644
--- a/src/main/agent-hooks/posix-hook-command.ts
+++ b/src/main/agent-hooks/posix-hook-command.ts
@@ -31,3 +31,12 @@ export function wrapPosixHookCommand(
   ].join(' && ')
   return `if ${guards}; then ${invocation}; else ${fallback}; fi`
 }
+
+// ACP launches argv[0] directly; give the shell guard an executable interpreter.
+export function wrapPosixHookCommandForExec(
+  scriptPath: string,
+  env: Record<string, string> = {},
+  options: { fallbackStdout?: string; requiredEnvVar?: string } = {}
+): string {
+  return `/bin/sh -c ${quotePosixShellString(wrapPosixHookCommand(scriptPath, env, options))}`
+}
diff --git a/src/main/agent-hooks/posix-hook-exec-command.test-fixture.ts b/src/main/agent-hooks/posix-hook-exec-command.test-fixture.ts
new file mode 100644
index 00000000000..9498e62f8fe
--- /dev/null
+++ b/src/main/agent-hooks/posix-hook-exec-command.test-fixture.ts
@@ -0,0 +1,53 @@
+// Mirrors the ACP host's POSIX `shlex.split` so tests can exercise the exec path (#16087).
+// Throws on malformed input like shlex does, so a broken quoting change fails loudly here.
+export function shlexSplit(command: string): string[] {
+  const tokens: string[] = []
+  let current = ''
+  let started = false
+  let quote: '"' | "'" | null = null
+  for (let index = 0; index < command.length; index += 1) {
+    const char = command[index]
+    if (char === '\\' && quote !== "'") {
+      const next = command[index + 1]
+      if (next === undefined) {
+        throw new Error(`shlexSplit: trailing backslash with nothing to escape: ${command}`)
+      }
+      current += quote === '"' && next !== '"' && next !== '\\' ? char + next : next
+      started = true
+      index += 1
+      continue
+    }
+    if (quote === null && (char === '"' || char === "'")) {
+      quote = char
+      started = true
+      continue
+    }
+    if (quote === char) {
+      quote = null
+      continue
+    }
+    if (quote === null && /\s/.test(char)) {
+      if (started) {
+        tokens.push(current)
+        current = ''
+        started = false
+      }
+      continue
+    }
+    current += char
+    started = true
+  }
+  if (quote !== null) {
+    throw new Error(`shlexSplit: unbalanced ${quote} quote: ${command}`)
+  }
+  if (started) {
+    tokens.push(current)
+  }
+  return tokens
+}
+
+// Unwrap the `/bin/sh -c` payload so assertions match the snippet, not its escaping.
+export function posixHookInnerCommand(command: string): string {
+  const argv = shlexSplit(command)
+  return argv[0] === '/bin/sh' && argv[1] === '-c' && argv[2] !== undefined ? argv[2] : command
+}
diff --git a/src/main/agent-hooks/posix-hook-exec-command.test.ts b/src/main/agent-hooks/posix-hook-exec-command.test.ts
new file mode 100644
index 00000000000..12ffb2f4b97
--- /dev/null
+++ b/src/main/agent-hooks/posix-hook-exec-command.test.ts
@@ -0,0 +1,66 @@
+import { afterEach, beforeEach, describe, expect, it } from 'vitest'
+import { chmodSync, mkdtempSync, rmSync, writeFileSync } from 'node:fs'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { runProcess } from '../../shared/child-process/run-process'
+import { wrapPosixHookCommandForExec } from './posix-hook-command'
+import { shlexSplit } from './posix-hook-exec-command.test-fixture'
+
+it('rejects incomplete command quoting', () => {
+  expect(() => shlexSplit("/bin/sh -c 'printf ok")).toThrow(/unbalanced/)
+  expect(() => shlexSplit('/bin/sh -c foo\\')).toThrow(/trailing backslash/)
+})
+
+it('preserves quoted backslashes and escaped single quotes', () => {
+  expect(shlexSplit(String.raw`cmd "a\q" 'a'\''b'`)).toEqual(['cmd', 'a\\q', "a'b"])
+})
+
+describe.skipIf(process.platform === 'win32')('POSIX exec hook command', () => {
+  let root: string
+  beforeEach(() => {
+    root = mkdtempSync(join(tmpdir(), 'orca-exec-hook-'))
+  })
+  afterEach(() => rmSync(root, { recursive: true, force: true }))
+
+  it.each(['present', 'missing', 'not-executable', 'missing-env'])(
+    'preserves the gate response with a %s script',
+    async (state) => {
+      const script = join(root, "hook 'quoted' $literal `name` 日本語.sh")
+      writeFileSync(script, '#!/bin/sh\nprintf \'%s\\n\' "$ORCA_TEST_EVENT"\ncat >/dev/null\n', {
+        mode: 0o700
+      })
+      if (state === 'missing') {
+        rmSync(script)
+      }
+      if (state === 'not-executable') {
+        chmodSync(script, 0o600)
+      }
+      const response = '{"decision":"ask"}'
+      const command = wrapPosixHookCommandForExec(
+        script,
+        { ORCA_TEST_EVENT: 'managed hook ran' },
+        { fallbackStdout: response, requiredEnvVar: 'ORCA_TEST_REQUIRED' }
+      )
+      const [program, ...args] = shlexSplit(command)
+      expect(program).toBe('/bin/sh')
+      if (!program) {
+        throw new Error('missing hook program')
+      }
+      for (const route of ['exec', 'shell']) {
+        const result = await runProcess({
+          program: route === 'exec' ? program : '/bin/sh',
+          args: route === 'exec' ? args : ['-c', command],
+          input: '{"toolCall":{"name":"read_file"}}',
+          env: { ...process.env, ORCA_TEST_REQUIRED: state === 'missing-env' ? '' : '1' },
+          timeoutMs: 5000
+        })
+        expect(result).toMatchObject({
+          code: 0,
+          stdout: `${state === 'present' ? 'managed hook ran' : response}\n`,
+          stderr: '',
+          timedOut: false
+        })
+      }
+    }
+  )
+})
diff --git a/src/main/agent-hooks/remote-hook-service-installers.test.ts b/src/main/agent-hooks/remote-hook-service-installers.test.ts
index 2e4cbb06496..fb2a7ee4498 100644
--- a/src/main/agent-hooks/remote-hook-service-installers.test.ts
+++ b/src/main/agent-hooks/remote-hook-service-installers.test.ts
@@ -1,6 +1,8 @@
+import { ANTIGRAVITY_EVENTS } from '../antigravity/hook-events'
 import { describe, expect, it, vi } from 'vitest'
 import { parse as parseJsonc } from 'jsonc-parser'
 import type { SFTPWrapper } from 'ssh2'
+import { posixHookInnerCommand } from './posix-hook-exec-command.test-fixture'
 
 vi.mock('electron', () => ({
   app: {
@@ -348,25 +350,23 @@ describe('remote hook service installers', () => {
         { matcher?: string; command?: string; hooks?: { command: string }[] }[]
       >
     }
-    for (const eventName of ['PreInvocation', 'PostInvocation', 'Stop']) {
-      const command = antigravityConfig['orca-status'][eventName]?.[0]?.command
+    const agyHooks = antigravityConfig['orca-status']
+    for (const { eventName, schema } of ANTIGRAVITY_EVENTS) {
+      const definition = agyHooks[eventName]?.[0]
+      const raw = definition?.command ?? definition?.hooks?.[0]?.command ?? ''
+      expect(raw).toMatch(/^\/bin\/sh -c /)
+      const command = posixHookInnerCommand(raw)
+      if (schema === 'tool') {
+        expect(definition?.matcher).toBe('*')
+      }
       expect(command).toContain('/home/dev/.orca/agent-hooks/antigravity-hook.sh')
       expect(command).toContain(`ORCA_ANTIGRAVITY_EVENT='${eventName}'`)
     }
-    for (const eventName of ['PreToolUse', 'PostToolUse']) {
-      const definition = antigravityConfig['orca-status'][eventName]?.[0]
-      const command = definition?.hooks?.[0]?.command
-      expect(definition?.matcher).toBe('*')
-      expect(command).toContain('/home/dev/.orca/agent-hooks/antigravity-hook.sh')
-      expect(command).toContain(`ORCA_ANTIGRAVITY_EVENT='${eventName}'`)
-    }
-    // Why: #2426 was an SSH report — a remote host missing the script must still answer the gate, not deny every tool.
-    expect(antigravityConfig['orca-status'].PreToolUse[0].hooks?.[0]?.command).toContain(
-      `printf '%s\\n' '{"decision":"ask"}'`
-    )
-    expect(antigravityConfig['orca-status'].PostToolUse[0].hooks?.[0]?.command).not.toContain(
-      '{"decision"'
-    )
+    // A remote host missing the script must still answer the gate (#2426).
+    const preTool = posixHookInnerCommand(agyHooks.PreToolUse[0].hooks?.[0]?.command ?? '')
+    const postTool = posixHookInnerCommand(agyHooks.PostToolUse[0].hooks?.[0]?.command ?? '')
+    expect(preTool).toContain(`printf '%s\\n' '{"decision":"ask"}'`)
+    expect(postTool).not.toContain('{"decision"')
 
     const ampPlugin = amp.fs.files.get('/home/dev/.config/amp/plugins/orca-agent-status.ts')
     expect(ampPlugin).toContain('/hook/amp')
diff --git a/src/main/antigravity/hook-service.test.ts b/src/main/antigravity/hook-service.test.ts
index a0deb253188..31436e09006 100644
--- a/src/main/antigravity/hook-service.test.ts
+++ b/src/main/antigravity/hook-service.test.ts
@@ -18,6 +18,7 @@ vi.mock('os', async () => {
 
 import { AntigravityHookService } from './hook-service'
 import { createManagedCommandMatcher } from '../agent-hooks/installer-utils'
+import { posixHookInnerCommand } from '../agent-hooks/posix-hook-exec-command.test-fixture'
 
 const ANTIGRAVITY_SCRIPT_FILE_NAME =
   process.platform === 'win32' ? 'antigravity-hook.cmd' : 'antigravity-hook.sh'
@@ -128,10 +129,13 @@ describe('AntigravityHookService', () => {
     if (process.platform === 'win32') {
       expect(config['orca-status'].PreInvocation[0].command).not.toContain('ORCA_ANTIGRAVITY_EVENT')
     } else {
-      expect(config['orca-status'].PreInvocation[0].command).toContain(
+      expect(config['orca-status'].PreToolUse[0].hooks?.[0]?.command).toMatch(/^\/bin\/sh -c /)
+      expect(posixHookInnerCommand(config['orca-status'].PreInvocation[0].command ?? '')).toContain(
         "ORCA_ANTIGRAVITY_EVENT='PreInvocation'"
       )
-      expect(config['orca-status'].Stop[0].command).toContain("ORCA_ANTIGRAVITY_EVENT='Stop'")
+      expect(posixHookInnerCommand(config['orca-status'].Stop[0].command ?? '')).toContain(
+        "ORCA_ANTIGRAVITY_EVENT='Stop'"
+      )
     }
 
     const script = readFileSync(
diff --git a/src/main/antigravity/hook-service.ts b/src/main/antigravity/hook-service.ts
index e49a522257a..3cdd8129eeb 100644
--- a/src/main/antigravity/hook-service.ts
+++ b/src/main/antigravity/hook-service.ts
@@ -6,7 +6,7 @@ import type { AgentHookInstallState, AgentHookInstallStatus } from '../../shared
 import {
   getSharedManagedScriptPath,
   readHooksJson,
-  wrapPosixHookCommand,
+  wrapPosixHookCommandForExec,
   wrapWindowsCmdHookCommand,
   writeHooksJson,
   writeManagedScript,
@@ -60,7 +60,9 @@ function getWindowsWrapperScriptPath(event: AntigravityEvent): string {
 }
 
 function getPosixManagedCommand(scriptPath: string, event: AntigravityEvent): string {
-  return wrapPosixHookCommand(
+  // Why: Antigravity's ACP host execs this string as argv[0] rather than running it through a shell,
+  // so it must stay one spawnable token (#16087) — see wrapPosixHookCommandForExec.
+  return wrapPosixHookCommandForExec(
     scriptPath,
     { ORCA_ANTIGRAVITY_EVENT: event.eventName },
     // Why: a missing managed script must not brick tools; the guard answers PreToolUse itself instead of staying silent.