diff --git a/bin/gstack-ff-update b/bin/gstack-ff-update
index 79b527a93..538d6aca6 100755
--- a/bin/gstack-ff-update
+++ b/bin/gstack-ff-update
@@ -73,13 +73,14 @@ g() { git -c core.fsmonitor=false -c core.splitIndex=false "$@"; }
 _PF=$(
   unset GIT_DIR GIT_WORK_TREE GIT_INDEX_FILE GIT_COMMON_DIR GIT_OBJECT_DIRECTORY
   cd -- "$DIR/.." 2>/dev/null || exit 0
-  _top=$(git rev-parse --show-toplevel 2>/dev/null) || exit 0
-  _rel="$(git rev-parse --show-prefix 2>/dev/null)${DIR##*/}" || exit 0
+  pg() { git -c core.fsmonitor=false -c core.splitIndex=false "$@"; }
+  _top=$(pg rev-parse --show-toplevel 2>/dev/null) || exit 0
+  _rel="$(pg rev-parse --show-prefix 2>/dev/null)${DIR##*/}" || exit 0
   _n=0
   while IFS= read -r _l; do
     case "$_l" in (''|'160000 '*) ;; (*) _n=$((_n + 1)) ;; esac
   done <<EOF_PF
-$(git -C "$_top" --literal-pathspecs ls-files -s -- "$_rel" 2>/dev/null)
+$(pg -C "$_top" --literal-pathspecs ls-files -s -- "$_rel" 2>/dev/null)
 EOF_PF
   [ "$_n" -gt 0 ] && printf '%s\n%s\n%s\n' "$_top" "$_rel" "$_n"
 )
@@ -87,11 +88,12 @@ if [ -n "$_PF" ]; then
   _top=$(printf '%s\n' "$_PF" | sed -n 1p) _rel=$(printf '%s\n' "$_PF" | sed -n 2p) _n=$(printf '%s\n' "$_PF" | sed -n 3p)
   refuse 6 tracked-by-project "$_top tracks $_n files of the gstack install at $_rel, so every checkout there puts old gstack files back (VERSION frozen, #1022); nothing was changed; fix: git -C $(ff_quote "$_top") rm -r -q --cached -- $(ff_quote "$_rel"), add /$_rel/ to $(ff_quote "$_top/.gitignore") and commit both on every branch you check out (or vendor gstack as a git submodule), then git -C $(ff_quote "$DIR") stash push -m 'files reverted by the project' (keeps every edit) and re-run" 900
 fi
-if g cat-file -e HEAD:VERSION 2>/dev/null; then
+# An unmerged VERSION is left to the rescue below.
+if g cat-file -e HEAD:VERSION 2>/dev/null && [ -z "$(g ls-files -u -- VERSION 2>/dev/null)" ]; then
   g diff --quiet HEAD -- VERSION 2>/dev/null
   if [ $? -eq 1 ]; then
     _have=$(head -1 VERSION 2>/dev/null | tr -d '\r') _want=$(g show HEAD:VERSION 2>/dev/null | head -1 | tr -d '\r')
-    refuse 6 version-reverted "VERSION says ${_have:-nothing} but the checkout is at $_want: something outside git put old gstack files back (an enclosing project's checkout, #1022); nothing was changed; fix: git -C $(ff_quote "$DIR") stash push -m 'files reverted by the project' (keeps every edit), then re-run" 900
+    refuse 6 version-reverted "VERSION says ${_have:-nothing} but the checkout is at $_want: files changed outside git (an enclosing project's checkout puts old ones back, #1022, or a hand edit); nothing was changed; fix: git -C $(ff_quote "$DIR") stash push -m 'files reverted by the project' (keeps every edit), then re-run" 900
   fi
 fi
 [ "$PREFLIGHT" -eq 1 ] && exit 0
diff --git a/test/gstack-ff-update.test.ts b/test/gstack-ff-update.test.ts
index 78a6e1bbc..e1730c69a 100644
--- a/test/gstack-ff-update.test.ts
+++ b/test/gstack-ff-update.test.ts
@@ -289,6 +289,32 @@ describe.skipIf(process.platform === 'win32')('gstack-ff-update: moving the tree
     expect(reverted.status).toBe(6);
     expect(reverted.stdout).toStartWith('version-reverted: VERSION says 1.0.0 but the checkout is at 1.1.0');
     expect(read(fx, 'VERSION')).toBe('1.0.0\n');
+    write(fx, 'VERSION', '9.9.9\n');
+    expect(ff(fx).stdout).toStartWith('version-reverted: VERSION says 9.9.9 but the checkout is at 1.1.0: files changed outside git');
+  });
+
+  // Value: protects=an unmerged VERSION still takes the existing rescue, which the unmerged-files banner's command relies on;
+  //   fails_when=the version-reverted preflight fires on conflict markers; why_new=the preflight is new; seam=none
+  test('preflight: an unmerged VERSION is rescued, not refused as version-reverted', () => {
+    const fx = makeFixture();
+    makeUnmerged(fx, 'VERSION');
+    const target = release(fx, { 'notes.txt': 'x\n' });
+    const r = ff(fx, target);
+    expect(r.status, r.stdout + r.stderr).toBe(0);
+    expect(r.stdout).toMatch(/^rescued .* unmerged=1/);
+  });
+
+  // Value: protects=the preflight runs no code from the enclosing project (its core.fsmonitor hook); fails_when=an enclosing-repo git call
+  //   drops the fsmonitor override; why_new=the enclosing-project probe is new; seam=none
+  test('preflight: an enclosing project\'s core.fsmonitor hook never runs', () => {
+    const fx = makeFixture();
+    const sentinel = path.join(fx.base, 'fsmonitor-ran');
+    git(fx.base, 'init', '-q', '-b', 'main');
+    fs.writeFileSync(path.join(fx.base, 'hook.sh'), `#!/bin/sh\ntouch '${sentinel}'\n`, { mode: 0o755 });
+    git(fx.base, 'config', 'core.fsmonitor', path.join(fx.base, 'hook.sh'));
+    const r = spawnSync('bash', [FF, '--preflight', fx.install], { encoding: 'utf8', env: isolatedEnv(fx.base), timeout: 60_000 });
+    expect(r.status, r.stdout + r.stderr).toBe(0);
+    expect(fs.existsSync(sentinel)).toBe(false);
   });
 
   test('refusals: not a fast-forward, an unresolvable target, and a missing checkout', () => {