diff --git a/src/main/agent-hooks/windows-hook-post-interpreter.test.ts b/src/main/agent-hooks/windows-hook-post-interpreter.test.ts
index e495f2d01ca..e089737d5af 100644
--- a/src/main/agent-hooks/windows-hook-post-interpreter.test.ts
+++ b/src/main/agent-hooks/windows-hook-post-interpreter.test.ts
@@ -1,14 +1,7 @@
-// Why (#15117): Antigravity spent three months posting hook status through Windows
-// PowerShell 5.1 after every other agent had moved to curl.exe. Nothing caught it, because
-// the drift was invisible to per-agent tests: the shared builder took only `(source)` and had
-// no way to add the extra form field Antigravity needs, so it forked a private copy of the
-// then-correct PowerShell command (#2100). When the shared builder switched to curl (#6402),
-// every agent that *called* it was fixed for free and the private copy silently was not.
-//
-// This suite asserts the invariant that drift violated, across every agent at once: a managed
-// Windows .cmd hook posts through curl.exe and spawns no interpreter. It generates the scripts
-// under a mocked win32 platform rather than executing them, so it guards the POSIX CI legs too
-// — the drift would otherwise only be visible on a Windows runner.
+// Why (#15117): an agent holding a private copy of the shared post command missed the move to
+// curl for three months, invisible to per-agent tests. Assert the invariant across every agent
+// at once: a managed Windows .cmd hook posts through curl.exe and spawns no interpreter.
+// Generated under a mocked win32 platform, not executed, so the POSIX CI legs guard it too.
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { mkdtempSync, readFileSync, readdirSync, rmSync } from 'node:fs'
 import { tmpdir } from 'node:os'
diff --git a/src/main/antigravity/hook-script.ts b/src/main/antigravity/hook-script.ts
index 1c03a13cd8d..0645416c005 100644
--- a/src/main/antigravity/hook-script.ts
+++ b/src/main/antigravity/hook-script.ts
@@ -7,14 +7,10 @@ import {
 import { buildWindowsAgentHookPostCommand } from '../agent-hooks/installer-utils'
 import { ANTIGRAVITY_PRE_TOOL_USE_DECISION } from './hook-events'
 
-// Why (#15117): Antigravity was the last agent posting hook status through Windows
-// PowerShell 5.1. Its ~300ms cold start per event is what made the console the agent
-// allocates for each hook visible; curl.exe (Win10 1803+) finishes in ~10ms and, unlike
-// PowerShell, does not recode the UTF-8 payload through the console code page.
+// Why (#15117): PowerShell cost ~300ms of startup per event, which is what made the console
+// the agent allocates for each hook last long enough to see.
 const WINDOWS_ANTIGRAVITY_HOOK_POST_COMMAND = buildWindowsAgentHookPostCommand('antigravity', [
-  // Why: Antigravity alone takes its event name from the wrapper's env rather than the piped
-  // payload. Before `extraFormLines` existed this forced a private copy of the shared command,
-  // which is how this script missed the fleet-wide move to curl for three months (#15117).
+  // Why: Antigravity alone takes its event name from the wrapper's env, not the piped payload.
   '  --data-urlencode "hook_event_name=%ORCA_ANTIGRAVITY_EVENT%" ^'
 ])
 
@@ -22,9 +18,8 @@ export function getManagedScript(target: 'local' | 'posix' = 'local'): string {
   if (target === 'local' && process.platform === 'win32') {
     return [
       '@echo off',
-      // Why (#9358/#9941): a bare `setlocal` inherits delayed expansion from the caller, and
-      // every `!` in a percent-expanded value on the curl line is then eaten as a delayed
-      // reference — silently mangling paneKey and dropping worktreeId. `!` is legal in a path.
+      // Why (#9358/#9941): inherited delayed expansion eats `!` out of the percent-expanded
+      // curl args, mangling paneKey and dropping worktreeId. `!` is legal in a Windows path.
       'setlocal DisableDelayedExpansion',
       'if /I "%ORCA_ANTIGRAVITY_EVENT%"=="Stop" (',
       '  echo {"decision":""}',
diff --git a/src/main/antigravity/hook-service.test.ts b/src/main/antigravity/hook-service.test.ts
index 0a8eef814bb..b9f69b03cc1 100644
--- a/src/main/antigravity/hook-service.test.ts
+++ b/src/main/antigravity/hook-service.test.ts
@@ -98,8 +98,6 @@ describe('AntigravityHookService', () => {
     )
     expect(script).toContain('/hook/antigravity')
     if (process.platform === 'win32') {
-      // Why (#15117): PowerShell's ~300ms cold start per hook event is what made the
-      // per-event console visible; curl.exe keeps the flash imperceptible.
       expect(script).not.toContain('powershell.exe')
       expect(script).toContain('%SystemRoot%\\System32\\curl.exe')
       expect(script).toContain('hook_event_name=%ORCA_ANTIGRAVITY_EVENT%')
diff --git a/src/main/antigravity/windows-hook-payload-delivery.test.ts b/src/main/antigravity/windows-hook-payload-delivery.test.ts
index cdd4be941d4..8261cc3ce91 100644
--- a/src/main/antigravity/windows-hook-payload-delivery.test.ts
+++ b/src/main/antigravity/windows-hook-payload-delivery.test.ts
@@ -1,10 +1,5 @@
-// Why (#15117): Antigravity was the last agent whose Windows hook posted status through
-// Windows PowerShell 5.1. The agent spawns each hook itself, so Orca cannot suppress the
-// console it allocates — but PowerShell's ~300ms cold start is what made that console
-// linger long enough to be seen, roughly every 2-6s for a whole session. Moving to
-// curl.exe removes the interpreter from the hot path. Shape assertions alone would not
-// catch a curl line that posts nothing, so this suite pipes a real payload through the
-// installed wrappers and follows it to a listener.
+// Why (#15117): shape assertions cannot catch a curl line that posts nothing, so this suite
+// pipes a real payload through the installed wrappers and follows it to a live listener.
 import { afterEach, describe, expect, it, vi } from 'vitest'
 import { spawn } from 'node:child_process'
 import { createServer, type Server } from 'node:http'
@@ -99,7 +94,9 @@ type HookRun = { exitCode: number | null; stdout: string; stderr: string; timedO
 function runWrapper(
   wrapperPath: string,
   env: NodeJS.ProcessEnv,
-  stdinPayload: string = PAYLOAD
+  // Why: `null` abandons stdin instead of closing it — the shape a caller outside an Orca
+  // pane produces, and the only way to prove the env guard exits before reading (#11549).
+  stdinPayload: string | null = PAYLOAD
 ): Promise<HookRun> {
   return new Promise((resolve, reject) => {
     // Why: mirror how Antigravity spawns the hook — `cmd /c <bare .cmd path>`, the exact
@@ -131,7 +128,12 @@ function runWrapper(
       // Why: curl exits once the POST is written; give the listener a beat to finish reading it.
       setTimeout(() => resolve({ exitCode, stdout, stderr, timedOut }), 250)
     })
-    child.stdin.end(Buffer.from(stdinPayload, 'utf8'))
+    // Why: an abandoned pipe raises EPIPE once the child exits; swallow it so the run still
+    // resolves on the child's own terms.
+    child.stdin.on('error', () => {})
+    if (stdinPayload !== null) {
+      child.stdin.end(Buffer.from(stdinPayload, 'utf8'))
+    }
   })
 }
 
@@ -273,7 +275,8 @@ describe.skipIf(process.platform !== 'win32')('Antigravity Windows hook payload
     // so the guard must exit before the read — otherwise the console lingers indefinitely.
     const result = await runWrapper(
       join(home, '.orca', 'agent-hooks', 'antigravity-pre-tool-use.cmd'),
-      hookEnvironment({ USERPROFILE: home, HOME: home })
+      hookEnvironment({ USERPROFILE: home, HOME: home }),
+      null
     )
 
     expect(result.timedOut).toBe(false)
diff --git a/src/shared/agent-hook-listener-antigravity.test.ts b/src/shared/agent-hook-listener-antigravity.test.ts
index 320ab951946..9eac0d75593 100644
--- a/src/shared/agent-hook-listener-antigravity.test.ts
+++ b/src/shared/agent-hook-listener-antigravity.test.ts
@@ -26,20 +26,25 @@ describe('shared agent-hook-listener', () => {
   // Why (#15117): the Windows script posts stdin verbatim through curl, so an event that
   // fires without a payload arrives as `payload=""` rather than the `{}` the POSIX script
   // substitutes. Both transports must still produce the status transition.
-  it('accepts an Antigravity event whose payload arrived empty', () => {
-    const started = normalizeHookPayload(
-      state,
-      'antigravity',
-      {
-        paneKey: PANE_KEY,
-        tabId: 'tab-1',
-        worktreeId: 'wt',
-        hook_event_name: 'PreInvocation',
-        payload: ''
-      },
-      'production'
-    )
-    expect(started?.payload).toMatchObject({ state: 'working', agentType: 'antigravity' })
+  it('accepts an Antigravity event whose payload is empty or whitespace-only', () => {
+    for (const payload of ['', '   ', '\r\n']) {
+      const started = normalizeHookPayload(
+        state,
+        'antigravity',
+        {
+          paneKey: PANE_KEY,
+          tabId: 'tab-1',
+          worktreeId: 'wt',
+          hook_event_name: 'PreInvocation',
+          payload
+        },
+        'production'
+      )
+      expect(started?.payload, `payload ${JSON.stringify(payload)}`).toMatchObject({
+        state: 'working',
+        agentType: 'antigravity'
+      })
+    }
   })
 
   // Why (#15117): this is the shape Windows actually produces — curl omits the form field