diff --git a/lib/git-hooks/install.test.mjs b/lib/git-hooks/install.test.mjs
index 3b80f722f8f..acfd336a04c 100644
--- a/lib/git-hooks/install.test.mjs
+++ b/lib/git-hooks/install.test.mjs
@@ -34,13 +34,22 @@ after(() => rmSync(work, { recursive: true, force: true }));
 const has = (tool) => spawnSync("sh", ["-c", `command -v ${tool}`]).status === 0;
 const posixHost = process.platform !== "win32";
 
-// Git sees no global or system config, so a host core.hooksPath cannot leak in.
-const baseEnv = { ...process.env, GIT_CONFIG_GLOBAL: path.join(work, "no-global"), GIT_CONFIG_NOSYSTEM: "1" };
+// Git sees no global or system config, so a host core.hooksPath cannot leak in,
+// and runs no detached auto maintenance, whose lock file would change a tree() snapshot.
+const gitEnv = {
+  GIT_CONFIG_GLOBAL: path.join(work, "no-global"),
+  GIT_CONFIG_NOSYSTEM: "1",
+  GIT_CONFIG_COUNT: "2",
+  GIT_CONFIG_KEY_0: "maintenance.auto",
+  GIT_CONFIG_VALUE_0: "false",
+  GIT_CONFIG_KEY_1: "gc.auto",
+  GIT_CONFIG_VALUE_1: "0",
+};
+const baseEnv = { ...process.env, ...gitEnv };
 for (const k of ["GIT_DIR", "GIT_WORK_TREE", "GIT_INDEX_FILE", "CLAUDECODE", "AI_AGENT", "HUSKY", "CLAUDE_PLUGIN_DATA"]) {
   delete baseEnv[k];
 }
-process.env.GIT_CONFIG_GLOBAL = baseEnv.GIT_CONFIG_GLOBAL;
-process.env.GIT_CONFIG_NOSYSTEM = "1";
+Object.assign(process.env, gitEnv);
 
 let counter = 0;
 function git(repo, args, env = {}) {