diff --git a/dist/codex-hook-trust.js b/dist/codex-hook-trust.js
index 7303275f..24771dcb 100644
--- a/dist/codex-hook-trust.js
+++ b/dist/codex-hook-trust.js
@@ -43,6 +43,7 @@ export async function detectCodexHookTrustState(codexHome, cwd, timeoutMs = 1000
     const child = spawn('codex', ['app-server'], {
         env: { ...process.env, CODEX_HOME: codexHome },
         stdio: ['pipe', 'pipe', 'ignore'],
+        windowsHide: true,
     });
     const rl = readline.createInterface({ input: child.stdout });
     const pending = new Map();
diff --git a/dist/summarizer.js b/dist/summarizer.js
index 60719809..74d2c4e0 100644
--- a/dist/summarizer.js
+++ b/dist/summarizer.js
@@ -395,7 +395,8 @@ function readCommandOutput(command, args) {
     return new Promise((resolve, reject) => {
         const child = spawn(command, args, {
             env: getApiEnv(),
-            stdio: ['ignore', 'pipe', 'pipe']
+            stdio: ['ignore', 'pipe', 'pipe'],
+            windowsHide: true
         });
         let output = '';
         child.stdout.on('data', chunk => {
@@ -444,7 +445,8 @@ export async function runCodexCommand(command) {
     return new Promise((resolve, reject) => {
         const child = spawn(command.command, command.args, {
             env: getApiEnv(),
-            stdio: ['pipe', 'pipe', 'pipe']
+            stdio: ['pipe', 'pipe', 'pipe'],
+            windowsHide: true
         });
         let stderr = '';
         let answer = '';
diff --git a/dist/sync-cli.js b/dist/sync-cli.js
index 26172c70..6cd06587 100644
--- a/dist/sync-cli.js
+++ b/dist/sync-cli.js
@@ -136,6 +136,7 @@ if (isBackground) {
         ...filteredArgs
     ], {
         detached: true,
+        windowsHide: true,
         stdio: ['ignore', logFd, logFd]
     });
     child.unref(); // Allow parent to exit
diff --git a/src/codex-hook-trust.ts b/src/codex-hook-trust.ts
index 717a317e..26c11fcf 100644
--- a/src/codex-hook-trust.ts
+++ b/src/codex-hook-trust.ts
@@ -62,6 +62,7 @@ export async function detectCodexHookTrustState(
   const child = spawn('codex', ['app-server'], {
     env: { ...process.env, CODEX_HOME: codexHome },
     stdio: ['pipe', 'pipe', 'ignore'],
+    windowsHide: true,
   });
   const rl = readline.createInterface({ input: child.stdout });
   const pending = new Map<number, {
diff --git a/src/summarizer.ts b/src/summarizer.ts
index d7e3cc04..59d31ad3 100644
--- a/src/summarizer.ts
+++ b/src/summarizer.ts
@@ -456,7 +456,8 @@ function readCommandOutput(command: string, args: string[]): Promise<string> {
   return new Promise((resolve, reject) => {
     const child = spawn(command, args, {
       env: getApiEnv(),
-      stdio: ['ignore', 'pipe', 'pipe']
+      stdio: ['ignore', 'pipe', 'pipe'],
+      windowsHide: true
     });
     let output = '';
 
@@ -511,7 +512,8 @@ export async function runCodexCommand(command: CodexSummarizerCommand): Promise<
   return new Promise((resolve, reject) => {
     const child = spawn(command.command, command.args, {
       env: getApiEnv(),
-      stdio: ['pipe', 'pipe', 'pipe']
+      stdio: ['pipe', 'pipe', 'pipe'],
+      windowsHide: true
     });
 
     let stderr = '';
diff --git a/src/sync-cli.ts b/src/sync-cli.ts
index 297b20f8..bbc5fa3c 100644
--- a/src/sync-cli.ts
+++ b/src/sync-cli.ts
@@ -149,6 +149,7 @@ if (isBackground) {
     ...filteredArgs
   ], {
     detached: true,
+    windowsHide: true,
     stdio: ['ignore', logFd, logFd]
   });
 
diff --git a/test/spawn-windows-hide.test.ts b/test/spawn-windows-hide.test.ts
new file mode 100644
index 00000000..4661f7ec
--- /dev/null
+++ b/test/spawn-windows-hide.test.ts
@@ -0,0 +1,48 @@
+import { describe, it, expect } from 'vitest';
+import { readdirSync, readFileSync } from 'fs';
+import { join } from 'path';
+
+// On Windows, a console program started from a process with no console of its
+// own (the detached background sync, the summarizer it runs) gets a brand-new
+// console window unless the spawn passes `windowsHide: true`. Users saw a
+// terminal window flash for every background sync and every `codex app-server`
+// summarizer call. Every spawn in src/ must hide its window.
+const SRC_DIR = join(__dirname, '..', 'src');
+
+function spawnCallOptions(source: string): string[] {
+  const calls: string[] = [];
+  const pattern = /\bspawn\(/g;
+  let match: RegExpExecArray | null;
+  while ((match = pattern.exec(source)) !== null) {
+    let depth = 0;
+    let end = match.index + match[0].length - 1;
+    for (; end < source.length; end++) {
+      const ch = source[end];
+      if (ch === '(') depth++;
+      else if (ch === ')') {
+        depth--;
+        if (depth === 0) break;
+      }
+    }
+    calls.push(source.slice(match.index, end + 1));
+  }
+  return calls;
+}
+
+describe('child processes hide their console window on Windows', () => {
+  const files = readdirSync(SRC_DIR).filter(name => name.endsWith('.ts'));
+  const calls = files.flatMap(name =>
+    spawnCallOptions(readFileSync(join(SRC_DIR, name), 'utf8')).map(call => ({ name, call }))
+  );
+
+  it('finds the spawn calls it checks', () => {
+    expect(calls.length).toBeGreaterThanOrEqual(4);
+  });
+
+  it.each(calls.map(({ name, call }) => [name, call.split('\n')[0], call]))(
+    '%s: %s',
+    (_name, _firstLine, call) => {
+      expect(call).toMatch(/windowsHide:\s*true/);
+    }
+  );
+});