diff --git a/src/input-map-id.ts b/src/input-map-id.ts
index c63d8e6..9a5051e 100644
--- a/src/input-map-id.ts
+++ b/src/input-map-id.ts
@@ -22,7 +22,9 @@ function canonicalString(value: string): string {
  *
  * Objects sort keys as text; arrays retain order; strings escape only quote, backslash and control
  * characters; numbers are safe integers written in decimal. The bound avoids language-specific float
- * and large-integer spellings. Empty objects stay distinct from empty arrays.
+ * and large-integer spellings. Empty objects stay distinct from empty arrays. An object property whose
+ * value is `undefined` is absent, as it is in the uploaded JSON body, so the digest names the document
+ * the server receives.
  */
 function canonicalText(value: unknown): string {
   if (value === null) return 'null';
@@ -39,7 +41,9 @@ function canonicalText(value: unknown): string {
   if (Array.isArray(value)) return `[${value.map(canonicalText).join(',')}]`;
   if (value !== null && typeof value === 'object') {
     const record = value as Record<string, unknown>;
-    const keys = Object.keys(record).sort();
+    const keys = Object.keys(record)
+      .filter((key) => record[key] !== undefined)
+      .sort();
 
     return `{${keys.map((key) => `${canonicalString(key)}:${canonicalText(record[key])}`).join(',')}}`;
   }
diff --git a/src/map-command.ts b/src/map-command.ts
index ff8dd35..4862c5b 100644
--- a/src/map-command.ts
+++ b/src/map-command.ts
@@ -7,7 +7,7 @@ import { isProvenFlow } from './map/coordinates.js';
 import { type Flags, getStringFlag } from './flags.js';
 import { applyBuildStamp } from './build-stamp.js';
 import { isPreBundleBuildHook } from './build-hook.js';
-import { inputMapBuildId } from './input-map-id.js';
+import { inputMapBuildId, NonCanonicalInputMap } from './input-map-id.js';
 import { atomicWriteFileSync } from './safe-file.js';
 import type { Config } from './types.js';
 
@@ -138,9 +138,21 @@ export async function runMapDetailed(flags: Flags, options: MapOptions = {}): Pr
     // identity of THIS map into the imported rules file. A standalone manual map remains unbound.
     let buildId: string | null = null;
     if (options.setup || isPreBundleBuildHook()) {
-      const candidate = inputMapBuildId(map);
-      const stamp = applyBuildStamp(cwd, candidate);
-      if (stamp.kind === 'stamped' || stamp.kind === 'unchanged') {
+      let candidate: string | null = null;
+      let identityError: string | null = null;
+      try {
+        candidate = inputMapBuildId(map);
+      } catch (err) {
+        if (!(err instanceof NonCanonicalInputMap)) throw err;
+        identityError = err.message;
+      }
+      const stamp = candidate === null ? null : applyBuildStamp(cwd, candidate);
+      if (candidate === null || stamp === null) {
+        log(
+          `patchstack: could not bind this map to the runtime guard — ${identityError}. ` +
+            'Rules generated from these coordinates will detect only, not block.',
+        );
+      } else if (stamp.kind === 'stamped' || stamp.kind === 'unchanged') {
         buildId = candidate;
         log(`patchstack: bound this map to ${stamp.file} (${candidate.slice(0, 12)}).`);
       } else {
diff --git a/tests/input-map-id.test.ts b/tests/input-map-id.test.ts
index 1025221..e68a543 100644
--- a/tests/input-map-id.test.ts
+++ b/tests/input-map-id.test.ts
@@ -54,6 +54,22 @@ describe('the input-map identity', () => {
     );
   });
 
+  it('identifies the uploaded JSON form, where an undefined property is absent', () => {
+    const map = { version: 3, endpoints: [{ file: 'src/server.ts', inputs: [] }], coverage: { filesParsed: 2 } };
+    const withUndefined = {
+      ...map,
+      endpoints: [{ ...map.endpoints[0], route: undefined }],
+      coverage: { ...map.coverage, note: undefined },
+    };
+
+    expect(inputMapBuildId(withUndefined)).toBe(inputMapBuildId(map));
+    expect(inputMapBuildId(withUndefined)).toBe(inputMapBuildId(JSON.parse(JSON.stringify(withUndefined))));
+  });
+
+  it('refuses an undefined array element, which the upload would rewrite as null', () => {
+    expect(() => inputMapBuildId({ version: 3, endpoints: [undefined] })).toThrow(NonCanonicalInputMap);
+  });
+
   it('excludes the transport field that carries the digest', () => {
     const map = { version: 3, endpoints: [], coverage: {} };