diff --git a/README.md b/README.md
index b20a8a6..0edcc5c 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,7 @@ $ ./setup.sh
 
 The script creates `.env` and installs the Python dependencies listed in `pyproject.toml`.
 If `uv` is available, it uses `uv venv` and `uv pip install`; otherwise it uses the standard `venv` module and `pip`.
+It also builds a local precompiled header under `.env/pch/` to speed up repeated C++ compilations.
 
 Add `bin/` to your `PATH` so the tools can be invoked with short command names:
 
diff --git a/bin/build_pch.py b/bin/build_pch.py
new file mode 100644
index 0000000..e6af97b
--- /dev/null
+++ b/bin/build_pch.py
@@ -0,0 +1,77 @@
+#!/usr/bin/env python3
+
+import hashlib
+import json
+from pathlib import Path
+import shutil
+import subprocess
+
+from run import COMPILER, COMPILE_FLAGS, PCH_BUILD_FLAGS, PCH_CONTENT, PCH_GCH, PCH_HEADER
+
+
+def compiler_identity() -> dict[str, str | int]:
+    compiler_path = shutil.which(COMPILER)
+    if compiler_path is None:
+        raise FileNotFoundError(f"Compiler not found: {COMPILER}")
+
+    resolved_compiler = Path(compiler_path).resolve()
+    cc1plus = subprocess.check_output(
+        [COMPILER, "-print-prog-name=cc1plus"], text=True
+    ).strip()
+    cc1plus_path = Path(cc1plus).resolve()
+
+    return {
+        "path": str(resolved_compiler),
+        "mtime_ns": resolved_compiler.stat().st_mtime_ns,
+        "cc1plus_path": str(cc1plus_path),
+        "cc1plus_mtime_ns": cc1plus_path.stat().st_mtime_ns,
+        "version": subprocess.check_output(
+            [COMPILER, "-dumpfullversion", "-dumpversion"], text=True
+        ).strip(),
+    }
+
+
+def pch_signature() -> str:
+    payload = {
+        "compiler": compiler_identity(),
+        "compile_flags": COMPILE_FLAGS,
+        "pch_build_flags": PCH_BUILD_FLAGS,
+        "content": PCH_CONTENT,
+    }
+    encoded = json.dumps(payload, sort_keys=True).encode()
+    return hashlib.sha256(encoded).hexdigest()
+
+
+def main() -> int:
+    PCH_HEADER.parent.mkdir(parents=True, exist_ok=True)
+    if not PCH_HEADER.exists() or PCH_HEADER.read_text(encoding="utf8") != PCH_CONTENT:
+        PCH_HEADER.write_text(PCH_CONTENT, encoding="utf8")
+
+    stamp_path = PCH_HEADER.with_suffix(PCH_HEADER.suffix + ".sha256")
+    signature = pch_signature()
+
+    if PCH_GCH.exists() and stamp_path.exists() and stamp_path.read_text().strip() == signature:
+        print(f"PCH is up to date: {PCH_GCH}")
+        return 0
+
+    command = [
+        COMPILER,
+        *PCH_BUILD_FLAGS,
+        "-x",
+        "c++-header",
+        str(PCH_HEADER),
+        "-o",
+        str(PCH_GCH),
+    ]
+
+    print(f"Building PCH: {PCH_GCH}")
+    PCH_GCH.unlink(missing_ok=True)
+    subprocess.run(command, check=True)
+    if not PCH_GCH.is_file():
+        raise RuntimeError(f"Compiler did not create PCH: {PCH_GCH}")
+    stamp_path.write_text(signature + "\n", encoding="utf8")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/bin/run.py b/bin/run.py
index 462ba25..2bb7bbd 100644
--- a/bin/run.py
+++ b/bin/run.py
@@ -1,11 +1,36 @@
 import os
 import subprocess
+from pathlib import Path
 
 from message import debug_print
-from path import BIN_PATH
+from path import BIN_PATH, PROJ_PATH
 
 import time
 
+COMPILER = "g++-15"
+COMPILE_FLAGS = [
+    "-std=gnu++23",
+    "-O2",
+    "-Wall",
+    "-Wextra",
+    "-march=native",
+    # "-flto=auto",
+    "-fopenmp",
+    "-pthread",
+    "-ftrivial-auto-var-init=zero",
+    "-fconstexpr-depth=1024",
+    "-fconstexpr-loop-limit=524288",
+    "-fconstexpr-ops-limit=2097152",
+    "-DYSN_DEBUG",
+]
+PCH_BUILD_FLAGS = COMPILE_FLAGS.copy()
+LINK_FLAGS = [
+    "-lstdc++exp",
+]
+PCH_CONTENT = "#include <bits/stdc++.h>\n"
+PCH_HEADER = Path(PROJ_PATH) / ".env" / "pch" / "stdcxx_all.hpp"
+PCH_GCH = Path(str(PCH_HEADER) + ".gch")
+
 def exec_path_of(source_path):
     return os.path.splitext(source_path)[0] + ".exe"
 
@@ -36,25 +61,14 @@ def compile(source_path):
 
     debug_print(f"Compiling {source_path} ...")
     start_time = time.time()
+    pch_flags = ["-I", str(PCH_HEADER.parent), "-include", PCH_HEADER.name] if PCH_GCH.exists() else []
     compilation = subprocess.run([
-        "g++-15",
-        "-std=gnu++23",
-        "-O2",
-        "-Wall",
-        "-Wextra",
-        "-march=native",
-        "-flto=auto",
-        "-fmodules",
-        "-fopenmp",
-        "-pthread",
-        "-lstdc++exp",
-        "-ftrivial-auto-var-init=zero",
-        "-fconstexpr-depth=1024",
-        "-fconstexpr-loop-limit=524288",
-        "-fconstexpr-ops-limit=2097152",
-        "-DYSN_DEBUG",
+        COMPILER,
+        *COMPILE_FLAGS,
+        *pch_flags,
         source_path,
-        "-o", exec_path
+        "-o", exec_path,
+        *LINK_FLAGS,
     ])
     end_time = time.time()
     duration = end_time - start_time
diff --git a/documentation.md b/documentation.md
index 4cc68d9..e12cdb3 100644
--- a/documentation.md
+++ b/documentation.md
@@ -105,6 +105,7 @@ ly
 
 `setup.sh` は `.env` を作成し、`pyproject.toml` に記述された Python 依存を導入します。
 `uv` が使える環境では `uv venv` と `uv pip install` を使い、なければ標準の `venv` と `pip` にフォールバックします。
+セットアップ時には `.env/pch/` に `bits/stdc++.h` 用のローカル PCH も作成し、以後の C++ コンパイルで利用します。
 `ly` や Graphviz 出力で使う `tree` と `dot` コマンドが見つからない場合は、追加で必要なシステムコマンドとして案内します。
 
 C++ 側のテストは `CMakeLists.txt` と `vcpkg.json` で管理されます。
diff --git a/fixg++-15.sh b/fixg++-15.sh
new file mode 100644
index 0000000..4e52817
--- /dev/null
+++ b/fixg++-15.sh
@@ -0,0 +1,18 @@
+#!/bin/bash
+
+set -euo pipefail
+
+# https://github.com/orgs/Homebrew/discussions/6229#discussioncomment-14079111
+
+brew update
+brew upgrade
+brew install binutils
+brew reinstall binutils
+sudo update-alternatives \
+    --install /usr/bin/as as /home/linuxbrew/.linuxbrew/opt/binutils/bin/as 100 \
+    --slave /usr/bin/ld ld /home/linuxbrew/.linuxbrew/opt/binutils/bin/ld \
+    --slave /usr/bin/nm nm /home/linuxbrew/.linuxbrew/opt/binutils/bin/nm \
+    --slave /usr/bin/objdump objdump /home/linuxbrew/.linuxbrew/opt/binutils/bin/objdump \
+    --slave /usr/bin/objcopy objcopy /home/linuxbrew/.linuxbrew/opt/binutils/bin/objcopy \
+    --slave /usr/bin/strip strip /home/linuxbrew/.linuxbrew/opt/binutils/bin/strip
+sudo update-alternatives --config as
\ No newline at end of file
diff --git a/setup.sh b/setup.sh
index 119a4ca..94d7aeb 100644
--- a/setup.sh
+++ b/setup.sh
@@ -37,6 +37,8 @@ else
     python -m pip install "${python_dependencies[@]}"
 fi
 
+.env/bin/python bin/build_pch.py
+
 missing_commands=()
 
 if ! command -v tree >/dev/null 2>&1; then