diff --git a/bin/gstack-decision-trail b/bin/gstack-decision-trail
index 5d560c42c..297c6aee4 100755
--- a/bin/gstack-decision-trail
+++ b/bin/gstack-decision-trail
@@ -82,8 +82,8 @@ function appendRow(file: string, cells: readonly string[]): number {
   if (dir && dir !== "." && !fs.existsSync(dir)) fs.mkdirSync(dir, { recursive: true });
   // Append the header too, never truncate: on a flaky mount the worst case is
   // one stray header line, not lost rows.
-  // A file whose first line is not the header (empty, blank, or rows written by
-  // hand) gets one appended; readRows skips a header line wherever it sits.
+  // A file with no header line anywhere (empty, blank, or rows written by hand)
+  // gets one appended once; readRows skips a header line wherever it sits.
   const size = fs.existsSync(file) ? fs.statSync(file).size : 0;
   if (size > 0 && !endsWithNewline(file, size)) fs.appendFileSync(file, "\n");
   if (size === 0 || !hasHeader(file)) fs.appendFileSync(file, HEADER);
@@ -93,8 +93,8 @@ function appendRow(file: string, cells: readonly string[]): number {
 }
 
 function hasHeader(file: string): boolean {
-  const first = fs.readFileSync(file, "utf8").split("\n", 1)[0] ?? "";
-  return first.replace(/^\uFEFF/, "").replace(/\r$/, "") === HEADER.trimEnd();
+  return fs.readFileSync(file, "utf8").replace(/^\uFEFF/, "").split("\n")
+    .some(line => line.replace(/\r$/, "") === HEADER.trimEnd());
 }
 
 function endsWithNewline(file: string, size: number): boolean {
diff --git a/bin/gstack-worktree-audit b/bin/gstack-worktree-audit
index 820ac2959..2271c63ab 100755
--- a/bin/gstack-worktree-audit
+++ b/bin/gstack-worktree-audit
@@ -137,7 +137,9 @@ git worktree list --porcelain | awk 'BEGIN { RS=""; FS="\n" } {
   # git -C read describe whichever repository contains the directory, so its
   # own files would be invisible: report it broken, never safe.
   case "$flags" in *P*) printf '%s\t?\t?\tbroken\t?\t-\t-\treview\t%s\n' "$(du -sh "$wt" 2>/dev/null | awk '{print $1}')" "$wt"; continue ;; esac
-  if [ "$(git -C "$wt" rev-parse --show-toplevel 2>/dev/null)" != "$(cd "$wt" && pwd -P)" ]; then
+  # --show-cdup is empty only when the directory is itself a toplevel; a path
+  # comparison would misfire where git and the shell spell one path differently.
+  if [ ! -e "$wt/.git" ] || [ -n "$(git -C "$wt" rev-parse --show-cdup 2>/dev/null || echo broken)" ]; then
     printf '%s\t?\t?\tbroken\t?\t-\t-\treview\t%s\n' "$(du -sh "$wt" 2>/dev/null | awk '{print $1}')" "$wt"
     continue
   fi
diff --git a/test/decision-trail.test.ts b/test/decision-trail.test.ts
index 65f1e6e51..f25510c77 100644
--- a/test/decision-trail.test.ts
+++ b/test/decision-trail.test.ts
@@ -79,9 +79,11 @@ describe("gstack-decision-trail append", () => {
     const blank = path.join(tmp, "blank.tsv");
     fs.writeFileSync(blank, "\n");
     expect(run(blank, "p", "d", "w", "e", "r").status).toBe(0);
+    expect(run(blank, "p2", "d", "w", "e", "r").status).toBe(0);
     const lines = fs.readFileSync(blank, "utf8").split("\n");
     expect(lines[1]).toBe("ts\tphase\tdecision\twhy\tevidence\tresult");
     expect(lines[2]!.split("\t").slice(1)).toEqual(["p", "d", "w", "e", "r"]);
+    expect(lines.filter(l => l === "ts\tphase\tdecision\twhy\tevidence\tresult")).toHaveLength(1);
     const bom = path.join(tmp, "bom.tsv");
     fs.writeFileSync(bom, "\uFEFFts\tphase\tdecision\twhy\tevidence\tresult\n");
     expect(run("--run", "r1", bom, "p", "d", "w", "e", "r").status).toBe(0);