diff --git a/scripts/render-builds-table.py b/scripts/render-builds-table.py
index 9289a9cd11..f75df96e2d 100644
--- a/scripts/render-builds-table.py
+++ b/scripts/render-builds-table.py
@@ -53,7 +53,7 @@ from urllib.parse import quote
 # Direct-script invocation starts with scripts/, not the repository root.
 sys.path.insert(0, str(Path(__file__).resolve().parents[1]))
 
-from scripts.releases import handoff, r2, semver, stable  # noqa: E402
+from scripts.releases import handoff, r2, semver, stable, versioning  # noqa: E402
 
 MARKER = "<!-- HERMES_BUILDS_TABLE -->"
 END_MARKER = "<!-- /HERMES_BUILDS_TABLE -->"
@@ -409,6 +409,13 @@ def render_page(tag: str, assets_by_app: dict, base_url: str,
         f"<p>Release {_link(tag_url)}<code>{html.escape(tag)}</code></a>. Only objects this release "
         "actually staged in the bucket are listed.</p>",
     ]
+    attempt = versioning.parse_attempt_ref(tag)
+    if attempt is not None:
+        version = attempt[0]
+        body.append("<p><strong>"
+                    + html.escape(f"Attempt builds are not upgrade-safe: every attempt of {version} has the same "
+                                  f"package version, so an installed attempt is not replaced by the published {version}.")
+                    + "</strong></p>")
     if incomplete_jobs:
         body.append("<p><strong>Build incomplete.</strong> Jobs not successful: "
                     + html.escape(", ".join(incomplete_jobs))
diff --git a/tests/scripts/test_render_builds_publication.py b/tests/scripts/test_render_builds_publication.py
index 2c9b11625c..df70800731 100644
--- a/tests/scripts/test_render_builds_publication.py
+++ b/tests/scripts/test_render_builds_publication.py
@@ -118,6 +118,16 @@ def test_incomplete_tag_keeps_channel_and_links_diagnostics(monkeypatch, r2_serv
     assert r2_server.store['releases/canary/index.html'][0] == b'previous good page'
 
 
+def test_attempt_page_warns_and_canary_page_does_not():
+    base = 'https://cdn.example'
+    sentence = ('Attempt builds are not upgrade-safe: every attempt of 1.2.3 has the same '
+                'package version, so an installed attempt is not replaced by the published 1.2.3.')
+    page = rbt.render_page('rc.1-v1.2.3', {}, base)
+    assert sentence in page
+    for tag in ('v1.2.3', 'v1.2.3+canary.20260818T101010Z', 'abandoned-rc.1-v1.2.3'):
+        assert sentence not in rbt.render_page(tag, {}, base)
+
+
 @pytest.mark.parametrize('version,name', [
     ('1.2.3', 'HermesBundled-1.2.3-win-x64.msix'),
     ('1.2.3+canary.20260818T000000Z', 'HermesBundled-1.2.3+canary.20260818T000000Z-win-x64.msix'),