diff --git a/scripts/validate-members.mjs b/scripts/validate-members.mjs
index 4600d92b..3077b18d 100644
--- a/scripts/validate-members.mjs
+++ b/scripts/validate-members.mjs
@@ -417,9 +417,13 @@ if (landscape) {
       message: `membership source ID set mismatch (missing: ${missing.join(', ') || 'none'}; unexpected: ${unexpected.join(', ') || 'none'})`,
     });
   }
+  // collectedAt is the one field of this block the site renders
+  // (DirectoryFreshness), and the generator copies it from the snapshot root
+  // rather than from snapshot.source like the other two.
   if (
     data.sources?.landscape?.revision !== landscape.source?.revision ||
-    data.sources?.landscape?.sourceUrl !== landscape.source?.sourceUrl
+    data.sources?.landscape?.sourceUrl !== landscape.source?.sourceUrl ||
+    data.sources?.landscape?.collectedAt !== landscape.collectedAt
   ) {
     errors.push({
       path: 'members.json.sources.landscape',
diff --git a/tests/e2e-data-fixture-validity.test.mjs b/tests/e2e-data-fixture-validity.test.mjs
index f2eadbf1..e348f182 100644
--- a/tests/e2e-data-fixture-validity.test.mjs
+++ b/tests/e2e-data-fixture-validity.test.mjs
@@ -181,13 +181,10 @@ const EXPECTED = new Map([
   [
     'data-variant/members.json',
     {
-      // Recorded as an empty delta because that is what the gate does today,
-      // not because the shape is benign: DirectoryFreshness renders
-      // sources.landscape.collectedAt and validate-members.mjs never reads it,
-      // unlike every sibling validator's document-level timestamp. If that gap
-      // is closed this entry gains the new error, which is the signal.
-      why: 'makes sources.landscape.collectedAt unparseable to degrade the DirectoryFreshness note; validate-members.mjs does not check that field',
-      adds: [],
+      why: 'makes sources.landscape.collectedAt unparseable to degrade the DirectoryFreshness note; validate-members.mjs holds that field to the snapshot like revision and sourceUrl',
+      adds: [
+        'members.json.sources.landscape: landscape provenance must match enduser-landscape.json',
+      ],
     },
   ],
   [
diff --git a/tests/validate-members-membership.test.mjs b/tests/validate-members-membership.test.mjs
index 1ba1eaff..ca43a222 100644
--- a/tests/validate-members-membership.test.mjs
+++ b/tests/validate-members-membership.test.mjs
@@ -37,10 +37,12 @@ function member(id, membershipStatus, membershipSources = []) {
   };
 }
 
+const COLLECTED_AT = '2026-10-01T00:00:00.000Z';
+
 function snapshot(sourceIds) {
   return {
     generated: true,
-    collectedAt: '2026-10-01T00:00:00.000Z',
+    collectedAt: COLLECTED_AT,
     source: {
       repository: 'https://github.com/cncf/landscape',
       revision: REVISION,
@@ -54,7 +56,7 @@ function snapshot(sourceIds) {
   };
 }
 
-function run(members, landscape) {
+function run(members, landscape, provenance = {}) {
   return runScriptWithFixtures(SCRIPT, {
     'data/members.json': JSON.stringify({
       description: 'directory',
@@ -64,6 +66,8 @@ function run(members, landscape) {
           repository: 'https://github.com/cncf/landscape',
           revision: REVISION,
           sourceUrl: SOURCE_URL,
+          collectedAt: COLLECTED_AT,
+          ...provenance,
         },
       },
       schema: {},
@@ -172,6 +176,29 @@ test('rejects duplicate, missing, unexpected, and stale landscape provenance', (
   assert.match(result.stderr, /landscape provenance must match/);
 });
 
+// The generator writes revision, sourceUrl and collectedAt into
+// sources.landscape from one snapshot in one statement, and collectedAt is
+// the only one of the three DirectoryFreshness renders. A members.json that
+// kept the snapshot's revision but a different sync time (a partial
+// regeneration, a merge that took one side) states a date the data does not
+// support, so it is held to the snapshot like the other two.
+test('rejects a collectedAt that differs from the snapshot it claims', () => {
+  const memberSource = source('member-source', 'member');
+  const members = [member('one', 'member', [memberSource])];
+  const landscape = snapshot(['member-source']);
+  for (const collectedAt of [
+    '1999-01-01T00:00:00.000Z',
+    'not a timestamp',
+    null,
+    undefined,
+  ]) {
+    const result = run(members, landscape, { collectedAt });
+    assert.equal(result.status, 1, `collectedAt ${String(collectedAt)}`);
+    assert.match(result.stderr, /landscape provenance must match/);
+  }
+  assert.equal(run(members, landscape).status, 0);
+});
+
 test('requires membership fields for modern landscape-backed output', () => {
   const legacyShape = member('legacy-shape', 'unknown');
   delete legacyShape.membershipStatus;