diff --git a/src/bun.js/bindings/c-bindings.cpp b/src/bun.js/bindings/c-bindings.cpp
index 71c3e46c79f6..bcb8dbcb8b44 100644
--- a/src/bun.js/bindings/c-bindings.cpp
+++ b/src/bun.js/bindings/c-bindings.cpp
@@ -473,19 +473,25 @@ extern "C" void bun_initialize_process()
             } while (devNullFd_ < 0 and errno == EINTR);
         };
 
+        if (devNullFd_ < 0) {
+            // open("/dev/null") failed (e.g., in macOS App Sandbox).
+            // Continue without redirecting; this is best-effort.
+            return;
+        }
+
         if (devNullFd_ == target_fd) {
             devNullFd_ = -1;
             return;
         }
 
-        ASSERT(devNullFd_ != -1);
         int err;
         do {
             err = dup2(devNullFd_, target_fd);
         } while (err < 0 && errno == EINTR);
 
-        if (err != 0) [[unlikely]] {
-            abort();
+        // dup2 returns the new fd on success (not 0), or -1 on error.
+        if (err < 0) [[unlikely]] {
+            bun_is_stdio_null[target_fd] = 0;
         }
     };
 
@@ -497,7 +503,6 @@ extern "C" void bun_initialize_process()
                 setDevNullFd(fd);
             }
         } else {
-            bun_stdio_tty[fd] = 1;
             int err = 0;
 
             do {
@@ -505,6 +510,11 @@ extern "C" void bun_initialize_process()
             } while (err == -1 && errno == EINTR);
 
             if (err == 0) [[likely]] {
+                // Only mark as TTY if we successfully captured termios state.
+                // In macOS App Sandbox, tcgetattr fails with EPERM even though
+                // isatty() returns true. We must not try to restore state we
+                // never captured.
+                bun_stdio_tty[fd] = 1;
                 anyTTYs = true;
             }
         }
diff --git a/test/js/bun/test-macos-app-sandbox.test.ts b/test/js/bun/test-macos-app-sandbox.test.ts
new file mode 100644
index 000000000000..05bb880b862e
--- /dev/null
+++ b/test/js/bun/test-macos-app-sandbox.test.ts
@@ -0,0 +1,122 @@
+import { describe, expect, test } from "bun:test";
+import { copyFileSync } from "fs";
+import { bunEnv, bunExe, isMacOS, tempDir } from "harness";
+import { join } from "path";
+
+// Match Bun's own entitlements from entitlements.plist, plus app-sandbox.
+const entitlementsPlist = `<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>com.apple.security.app-sandbox</key>
+	<true/>
+	<key>com.apple.security.cs.allow-jit</key>
+	<true/>
+	<key>com.apple.security.cs.allow-unsigned-executable-memory</key>
+	<true/>
+	<key>com.apple.security.cs.disable-executable-page-protection</key>
+	<true/>
+	<key>com.apple.security.cs.allow-dyld-environment-variables</key>
+	<true/>
+	<key>com.apple.security.cs.disable-library-validation</key>
+	<true/>
+	<key>com.apple.security.network.client</key>
+	<true/>
+</dict>
+</plist>`;
+
+function makeInfoPlist(bundleId: string) {
+  return `<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleExecutable</key>
+	<string>bun</string>
+	<key>CFBundleIdentifier</key>
+	<string>${bundleId}</string>
+	<key>CFBundleInfoDictionaryVersion</key>
+	<string>6.0</string>
+	<key>CFBundleName</key>
+	<string>bun_sandboxed</string>
+	<key>CFBundlePackageType</key>
+	<string>APPL</string>
+	<key>CFBundleShortVersionString</key>
+	<string>1.0</string>
+	<key>CFBundleSupportedPlatforms</key>
+	<array>
+		<string>MacOSX</string>
+	</array>
+	<key>CFBundleVersion</key>
+	<string>1</string>
+</dict>
+</plist>`;
+}
+
+function createSandboxedApp(prefix: string, bundleId: string) {
+  const dir = tempDir(prefix, {
+    "entitlements.plist": entitlementsPlist,
+    "bun_sandboxed.app": {
+      "Contents": {
+        "Info.plist": makeInfoPlist(bundleId),
+        "MacOS": {},
+      },
+    },
+  });
+
+  const bunPath = join(String(dir), "bun_sandboxed.app", "Contents", "MacOS", "bun");
+  const appBundlePath = join(String(dir), "bun_sandboxed.app");
+  const entitlementsPath = join(String(dir), "entitlements.plist");
+
+  copyFileSync(bunExe(), bunPath);
+
+  const codesignResult = Bun.spawnSync({
+    cmd: ["/usr/bin/codesign", "--entitlements", entitlementsPath, "--force", "-s", "-", appBundlePath],
+    env: bunEnv,
+    stderr: "inherit",
+  });
+  expect(codesignResult.exitCode).toBe(0);
+
+  return { dir, bunPath, bundleId };
+}
+
+// Modeled after Node.js's test/parallel/test-macos-app-sandbox.js
+describe.skipIf(!isMacOS)("macOS App Sandbox", () => {
+  test("bun can execute JavaScript inside the app sandbox", async () => {
+    const { dir, bunPath } = createSandboxedApp("macos-sandbox-test", "dev.bun.test.sandbox_exec");
+    using _dir = dir;
+
+    await using proc = Bun.spawn({
+      cmd: [bunPath, "-e", "console.log('hello sandbox')"],
+      env: bunEnv,
+      stdout: "pipe",
+      stderr: "inherit",
+    });
+
+    const [stdout, exitCode] = await Promise.all([proc.stdout.text(), proc.exited]);
+
+    expect(stdout.trim()).toBe("hello sandbox");
+    expect(exitCode).toBe(0);
+  });
+
+  test("sandboxed bun runs inside the sandbox container", async () => {
+    const { dir, bunPath, bundleId } = createSandboxedApp(
+      "macos-sandbox-test-container",
+      "dev.bun.test.sandbox_container",
+    );
+    using _dir = dir;
+
+    // When running inside a macOS App Sandbox, os.homedir() should return
+    // the sandbox container path, not the real home directory.
+    await using proc = Bun.spawn({
+      cmd: [bunPath, "-e", "console.log(require('os').homedir())"],
+      env: bunEnv,
+      stdout: "pipe",
+      stderr: "inherit",
+    });
+
+    const [stdout, exitCode] = await Promise.all([proc.stdout.text(), proc.exited]);
+
+    expect(stdout.trim()).toContain(`Library/Containers/${bundleId}`);
+    expect(exitCode).toBe(0);
+  });
+});