diff --git a/build_libicsneo.py b/build_libicsneo.py
index 13b1fc6f..93d7b16a 100644
--- a/build_libicsneo.py
+++ b/build_libicsneo.py
@@ -14,19 +14,28 @@
 LIBUSB_BUILD = f"{LIBUSB_ROOT}/build"
 LIBUSB_INSTALL = f"{LIBUSB_ROOT}/install"
 
-# NOTE: this pin's vendored icsnVC40.h predates Vspy 3.26.3.9
-# (SRADGalaxy2Settings 840 vs 1204, no Comet3/Gigastar2), so Linux/macOS
-# wheels lag the Windows ABI. Newer upstream doesn't help yet: master
-# (4ed29b4, 2026-07-07) still has the old header AND adds a mandatory
-# icspb protobuf dependency whose codegen fails on clean CI runners.
-# Bump once upstream syncs the header and icspb builds.
-LIBICSNEO_VERSION = "830fe1a"
+# libicsneo master 2026-07-08; its vendored icsnVC40.h is byte-identical
+# to include/ics/icsnVC40.h (Vspy 3.26.3.9), so Linux/macOS wheels match
+# the Windows ABI. Keep the two headers in lockstep on future bumps.
+# libicsneo requires icspb (protobuf) as of 2026: its codegen needs the
+# Ninja generator (protobuf_generate never creates PROTOC_OUT_DIR; Make
+# doesn't pre-create declared output dirs, Ninja does), and it bootstraps
+# protobuf from source at configure time — see ICSPB_BOOTSTRAP_DIR below.
+LIBICSNEO_VERSION = "0dd8dbf"
 LIBICSNEO_ROOT = f"{ROOT}/libicsneo/{LIBICSNEO_VERSION}"
 LIBICSNEO_SOURCE = f"{LIBICSNEO_ROOT}/source"
 LIBICSNEO_BUILD = f"{LIBICSNEO_ROOT}/build"
 LIBICSNEO_INSTALL = f"{LIBICSNEO_ROOT}/install"
 print(f"LIBICSNEO PATH: {LIBICSNEO_ROOT}")
 
+# icspb bootstraps protobuf from source at configure time. Keep the
+# bootstrap OUTSIDE the libicsneo build dir so it survives the per-python
+# `git clean` in _build_libicsneo_linux and is reused across all
+# cibuildwheel builds in a job (it self-partitions by <system>-<processor>,
+# so sharing one root across archs is safe). Building protobuf once per
+# arch instead of once per python matters most under QEMU aarch64.
+ICSPB_BOOTSTRAP_DIR = f"{ROOT}/icspb_bootstrap"
+
 LIBPCAP_VERSION = "1.10.4"
 LIBPCAP_ROOT = f"{ROOT}/libpcap/{LIBPCAP_VERSION}"
 LIBPCAP_SOURCE = f"{LIBPCAP_ROOT}/source"
@@ -102,6 +111,18 @@ def _build_libpcap():
     subprocess.check_output(["make", "-j" + CPUS], cwd=LIBPCAP_BUILD)
     subprocess.check_output(["make", "install"], cwd=LIBPCAP_BUILD)
 
+def _cmake_ninja_args():
+    # pip's ninja lives inside each isolated build env, and cibuildwheel
+    # deletes that env between python versions. A reused CMake build dir
+    # caches the old (now dead) path in CMAKE_MAKE_PROGRAM and fails at
+    # the next configure, so always override with the current ninja.
+    ninja = shutil.which("ninja")
+    args = ["-G", "Ninja"]
+    if ninja:
+        args.append(f"-DCMAKE_MAKE_PROGRAM={ninja}")
+    return args
+
+
 def _build_libicsneo_linux():
     print("Cleaning libicsneo...")
     subprocess.check_output(["git", "clean", "-xdf"], cwd="libicsneo")
@@ -111,9 +132,13 @@ def _build_libicsneo_linux():
     subprocess.check_output(
         [
             "cmake",
+            # Ninja is required: icspb's protobuf_generate never creates its
+            # output dir, and only Ninja pre-creates declared output dirs.
+            *_cmake_ninja_args(),
             "-DCMAKE_BUILD_TYPE=Release",
             "-DLIBICSNEO_BUILD_ICSNEOLEGACY=ON",
             f"-DCMAKE_PREFIX_PATH={LIBUSB_INSTALL};{LIBPCAP_INSTALL}",
+            f"-DICSPB_BOOTSTRAP_DIR={ICSPB_BOOTSTRAP_DIR}",
             "-S", LIBICSNEO_SOURCE,
             "-B", LIBICSNEO_BUILD,
             "-Wno-dev",
@@ -125,17 +150,29 @@ def _build_libicsneo_linux():
     )
 
 def _build_libicsneo_macos():
+    env = os.environ.copy()
+    # Set as env vars (not only -D flags) so icspb's nested protobuf
+    # bootstrap — a separate cmake invocation via execute_process, which
+    # inherits the environment but not our -D cache entries — also builds
+    # universal2 static libs instead of arm64-only ones.
+    env["CMAKE_OSX_ARCHITECTURES"] = "arm64;x86_64"
+    env["CMAKE_OSX_DEPLOYMENT_TARGET"] = "10.13"
     subprocess.check_output(
         [
             "cmake",
+            # Ninja is required: icspb's protobuf_generate never creates its
+            # output dir, and only Ninja pre-creates declared output dirs.
+            *_cmake_ninja_args(),
             "-DCMAKE_BUILD_TYPE=Release",
             "-DCMAKE_OSX_ARCHITECTURES=arm64;x86_64",
             "-DLIBICSNEO_BUILD_ICSNEOLEGACY=ON",
             "-DCMAKE_OSX_DEPLOYMENT_TARGET=10.13",
             f"-DCMAKE_PREFIX_PATH={LIBUSB_INSTALL};{LIBPCAP_INSTALL}",
+            f"-DICSPB_BOOTSTRAP_DIR={ICSPB_BOOTSTRAP_DIR}",
             "-S", LIBICSNEO_SOURCE,
             "-B", LIBICSNEO_BUILD
-        ]
+        ],
+        env=env,
     )
 
     subprocess.check_output(
diff --git a/pyproject.toml b/pyproject.toml
index 9886c776..faea49e5 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -42,6 +42,9 @@ requires = [
   "wheel",
   "dunamai",
   "pytest>=8.4.2",
+  # Puts the ninja executable on the isolated build env's PATH; required by
+  # build_libicsneo.py's `cmake -G Ninja` on Linux/macOS (see comments there).
+  "ninja",
 ]