diff --git a/tools/git-hooks/pre-commit b/tools/git-hooks/pre-commit
index 87629d3..a1e4b47 100755
--- a/tools/git-hooks/pre-commit
+++ b/tools/git-hooks/pre-commit
@@ -14,13 +14,11 @@ if [ -n "$bad" ]; then
   exit 1
 fi
 
-# Android: the pure model tests, on the pinned JDK (android/gradle.properties); the shell's java may be a stub.
-if [ -x "$top/android/gradlew" ] && [ -d "$top/android/core/model" ]; then
-  case "$("${JAVA_HOME:+$JAVA_HOME/bin/}java" -version 2>&1 | head -1)" in
-    *\"25*) ;;
-    *) [ -d /opt/homebrew/opt/openjdk@25 ] && export JAVA_HOME=/opt/homebrew/opt/openjdk@25/libexec/openjdk.jdk/Contents/Home ;;
-  esac
-  (cd "$top/android" && ./gradlew --quiet :core:model:test :domain:test) || {
+# Android: the pure model tests, through the one-build-at-a-time lock, with JDK 25 first on PATH and JAVA_HOME
+# untouched (CLAUDE.md › Build and verify); the shell's java may be a stub.
+if [ -x "$top/android/gradlew" ] && [ -d "$top/android/core/model" ] && [ -x "$top/tools/gradle-serial.sh" ]; then
+  [ -d /opt/homebrew/opt/openjdk@25/bin ] && PATH="/opt/homebrew/opt/openjdk@25/bin:$PATH"
+  "$top/tools/gradle-serial.sh" --quiet :core:model:test :domain:test || {
     echo "pre-commit: Android fast tests failed (see above). Run tools/gradle-serial.sh check for the full picture." >&2
     exit 1
   }
diff --git a/tools/install-git-hooks.sh b/tools/install-git-hooks.sh
index 82cda36..2da22d0 100755
--- a/tools/install-git-hooks.sh
+++ b/tools/install-git-hooks.sh
@@ -1,15 +1,24 @@
 #!/usr/bin/env bash
 # Installs the Kvitt pre-commit hook into this repository's hooks folder (shared by all worktrees).
 # The hook guards itself: on branches without android/ or server/ it only runs the secrets check.
+# An earlier version of the Kvitt hook (recognised by its first comment line) is replaced; any other hook is kept.
 set -euo pipefail
 here="$(cd "$(dirname "$0")" && pwd)"
+src="$here/git-hooks/pre-commit"
 hooks="$(git -C "$here" rev-parse --path-format=absolute --git-common-dir)/hooks"
 target="$hooks/pre-commit"
-if [[ -e "$target" ]] && ! cmp -s "$here/git-hooks/pre-commit" "$target"; then
-  echo "A different pre-commit hook already exists at $target; not overwriting. Merge them by hand." >&2
-  exit 1
+marker="# Kvitt pre-commit hook:"
+if [[ -e "$target" ]]; then
+  if cmp -s "$src" "$target"; then
+    echo "Up to date: $target"
+    exit 0
+  fi
+  if ! sed -n 2p "$target" | grep -qF "$marker"; then
+    echo "A different pre-commit hook already exists at $target; not overwriting. Merge them by hand." >&2
+    exit 1
+  fi
 fi
 mkdir -p "$hooks"
-cp "$here/git-hooks/pre-commit" "$target"
+cp "$src" "$target"
 chmod +x "$target"
 echo "Installed $target"