diff --git a/scripts/verify/architecture-guards.mjs b/scripts/verify/architecture-guards.mjs
index 1dde594197..837d18dc4d 100644
--- a/scripts/verify/architecture-guards.mjs
+++ b/scripts/verify/architecture-guards.mjs
@@ -5,6 +5,7 @@ import { recordPredicateCounts } from "./record-predicate-guard.mjs";
 import {
   compareCountedBaseline,
   recordLoweredBaseline,
+  reconcileBaselineFile,
 } from "./counted-baseline.mjs";
 import { localCompletenessEnumCount } from "./completeness-enum-guard.mjs";
 import { countKeyedFirstMatches } from "./keyed-first-match.mjs";
@@ -269,7 +270,8 @@ const baselinePath = join(
   root,
   "scripts/verify/architecture-guard-baselines.json",
 );
-const baselines = JSON.parse(await readFile(baselinePath, "utf8"));
+const baselineText = await readFile(baselinePath, "utf8");
+const baselines = JSON.parse(baselineText);
 const shrinkBaselines = process.argv.includes("--shrink-baselines");
 let baselinesShrunk = false;
 const checkCounted = (label, key, selected, pattern, owners) => {
@@ -671,20 +673,22 @@ checkCounted(
   [],
 );
 
-if (baselinesShrunk) {
-  const sorted = Object.fromEntries(
-    Object.entries(baselines).map(([key, counts]) => [
-      key,
-      Object.fromEntries(
-        Object.entries(counts).sort(([left], [right]) =>
-          left < right ? -1 : left > right ? 1 : 0,
-        ),
-      ),
-    ]),
+const baselineFile = reconcileBaselineFile(
+  baselineText,
+  baselines,
+  shrinkBaselines,
+);
+if (baselineFile.action === "write") {
+  await writeFile(baselinePath, baselineFile.text);
+  console.log(
+    baselinesShrunk
+      ? `Lowered counted baselines in ${relative(root, baselinePath)}.`
+      : `Rewrote ${relative(root, baselinePath)} in its sorted form.`,
+  );
+} else if (baselineFile.action === "reject")
+  failures.push(
+    `${relative(root, baselinePath)} is not in its written form (each guard's paths sorted by code unit); rewrite it with \`node scripts/verify/architecture-guards.mjs --shrink-baselines\`.`,
   );
-  await writeFile(baselinePath, `${JSON.stringify(sorted, null, 2)}\n`);
-  console.log(`Lowered counted baselines in ${relative(root, baselinePath)}.`);
-}
 
 if (failures.length > 0) {
   console.error(`Architecture guards failed:\n\n${failures.join("\n\n")}\n`);
diff --git a/scripts/verify/counted-baseline.d.mts b/scripts/verify/counted-baseline.d.mts
index 4a10c97d7b..3635801947 100644
--- a/scripts/verify/counted-baseline.d.mts
+++ b/scripts/verify/counted-baseline.d.mts
@@ -27,3 +27,17 @@ export function recordLoweredBaseline(
     readonly lowered: boolean;
   },
 ): boolean;
+
+/** The baseline file text: guard order kept, each guard's paths in code-unit order. */
+export function serializeCountedBaselines(
+  baselines: Readonly<Record<string, Readonly<Record<string, number>>>>,
+): string;
+
+/** Leave, rewrite or reject the baseline file read as `text`. */
+export function reconcileBaselineFile(
+  text: string,
+  baselines: Readonly<Record<string, Readonly<Record<string, number>>>>,
+  shrink: boolean,
+):
+  | { readonly action: "none" | "reject" }
+  | { readonly action: "write"; readonly text: string };
diff --git a/scripts/verify/counted-baseline.mjs b/scripts/verify/counted-baseline.mjs
index a090377c22..6a74fefc7f 100644
--- a/scripts/verify/counted-baseline.mjs
+++ b/scripts/verify/counted-baseline.mjs
@@ -36,3 +36,36 @@ export const recordLoweredBaseline = (baselines, key, compared) => {
   else baselines[key] = compared.baseline;
   return true;
 };
+
+const byCodeUnit = ([left], [right]) =>
+  left < right ? -1 : left > right ? 1 : 0;
+
+/**
+ * The baseline file's one written form: guard keys keep their order and each
+ * guard's paths are sorted by code unit. The guard rejects a file in any other
+ * form, so a hand edit or merge cannot leave an order the next
+ * `--shrink-baselines` would silently rewrite in an unrelated change.
+ */
+export const serializeCountedBaselines = (baselines) =>
+  `${JSON.stringify(
+    Object.fromEntries(
+      Object.entries(baselines).map(([key, counts]) => [
+        key,
+        Object.fromEntries(Object.entries(counts).sort(byCodeUnit)),
+      ]),
+    ),
+    null,
+    2,
+  )}\n`;
+
+/**
+ * What the guard does with the baseline file it read as `text`, given the
+ * baselines after comparison: nothing when the file is already in its written
+ * form; otherwise `write` that form when shrinking (even if no count was
+ * lowered), or `reject` the file so a hand edit is fixed in its own change.
+ */
+export const reconcileBaselineFile = (text, baselines, shrink) => {
+  const written = serializeCountedBaselines(baselines);
+  if (written === text) return { action: "none" };
+  return shrink ? { action: "write", text: written } : { action: "reject" };
+};
diff --git a/tests/boundary/filesystem/countedBaseline.test.ts b/tests/boundary/filesystem/countedBaseline.test.ts
index 9617ff763f..b6a816abd0 100644
--- a/tests/boundary/filesystem/countedBaseline.test.ts
+++ b/tests/boundary/filesystem/countedBaseline.test.ts
@@ -2,7 +2,9 @@ import { expect, it } from "vitest";
 
 import {
   compareCountedBaseline,
+  reconcileBaselineFile,
   recordLoweredBaseline,
+  serializeCountedBaselines,
 } from "../../../scripts/verify/counted-baseline.mjs";
 
 it("rejects a file that gains copies or is missing from the baseline", () => {
@@ -90,3 +92,44 @@ it("removes a key when shrinking removes its last recorded count", () => {
   expect(recordLoweredBaseline(baselines, "gone", compared)).toBe(true);
   expect(baselines).toEqual({ kept: { "src/b.ts": 2 } });
 });
+
+it("writes each guard's paths in code-unit order and keeps guard order", () => {
+  const baselines = {
+    later: { "src/b.ts": 1, "src/Upper.ts": 2, "src/a.ts": 3 },
+    earlier: {},
+  };
+  expect(serializeCountedBaselines(baselines)).toBe(
+    `${JSON.stringify(
+      {
+        later: { "src/Upper.ts": 2, "src/a.ts": 3, "src/b.ts": 1 },
+        earlier: {},
+      },
+      null,
+      2,
+    )}\n`,
+  );
+});
+
+it("rejects an unsorted baseline file unless shrinking, which rewrites it", () => {
+  const baselines = { guard: { "src/a.ts": 1, "src/b.ts": 2 } };
+  const written = serializeCountedBaselines(baselines);
+  const unsorted = `${JSON.stringify(
+    { guard: { "src/b.ts": 2, "src/a.ts": 1 } },
+    null,
+    2,
+  )}\n`;
+  expect(reconcileBaselineFile(written, baselines, false)).toEqual({
+    action: "none",
+  });
+  expect(reconcileBaselineFile(written, baselines, true)).toEqual({
+    action: "none",
+  });
+  expect(reconcileBaselineFile(unsorted, baselines, false)).toEqual({
+    action: "reject",
+  });
+  // No count was lowered; shrinking still writes the sorted form.
+  expect(reconcileBaselineFile(unsorted, baselines, true)).toEqual({
+    action: "write",
+    text: written,
+  });
+});