diff --git a/.gitignore b/.gitignore
index 2467e2f..8be9f7a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -27,8 +27,5 @@ devenv.local.nix
 # direnv
 .direnv
 
-# pre-commit
-.pre-commit-config.yaml
-
 # Local runtime artifacts
 /.state/
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 0000000..5564ea6
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,23 @@
+# Shared by Nix/devenv and Guix shells. Keep hook entries PATH-based.
+default_stages:
+  - pre-commit
+
+repos:
+  - repo: local
+    hooks:
+      - id: check-added-large-files
+        name: check added large files
+        entry: scripts/hooks/check-added-large-files
+        args: ["--maxkb=16384"]
+        language: system
+        types: [file]
+        stages: [pre-commit, pre-push, manual]
+
+      - id: npm-format-check
+        name: npm format check
+        entry: npm run format:check
+        language: system
+        pass_filenames: false
+        files: '\.(cjs|js|json|md|mjs|ts|tsx|yaml|yml)$'
+        types: [text]
+        stages: [pre-commit]
diff --git a/scripts/hooks/check-added-large-files b/scripts/hooks/check-added-large-files
new file mode 100755
index 0000000..b46fa23
--- /dev/null
+++ b/scripts/hooks/check-added-large-files
@@ -0,0 +1,38 @@
+#!/usr/bin/env sh
+set -eu
+
+maxkb=500
+while [ "$#" -gt 0 ]; do
+  case "$1" in
+    --maxkb=*)
+      maxkb=${1#--maxkb=}
+      shift
+      ;;
+    --)
+      shift
+      break
+      ;;
+    -*)
+      echo "check-added-large-files: unknown option: $1" >&2
+      exit 2
+      ;;
+    *)
+      break
+      ;;
+  esac
+done
+
+limit=$((maxkb * 1024))
+failed=0
+
+for file in "$@"; do
+  [ -f "$file" ] || continue
+  size=$(wc -c < "$file" | tr -d '[:space:]')
+  if [ "$size" -gt "$limit" ]; then
+    kb=$(((size + 1023) / 1024))
+    echo "$file (${kb} KB) exceeds ${maxkb} KB" >&2
+    failed=1
+  fi
+done
+
+exit "$failed"