diff --git a/README.md b/README.md
index dece1f37..c693d385 100644
--- a/README.md
+++ b/README.md
@@ -77,6 +77,11 @@ uv run --extra=dev tox -e e2e
 
 Note: E2E tests require the frontend to be built first. Run `npm run build` or `npm run start` in `server/frontend/` before running E2E tests.
 
+E2E test data lives in `tests/e2e/fixtures/fixtures.json` and is generated by `tests/e2e/scripts/generate_e2e_fixtures.py`. Edit `BUCKETS_CONFIG` in that script to add or modify test buckets and their reports, then regenerate the fixture file:
+
+```
+uv run --extra=server python tests/e2e/scripts/generate_e2e_fixtures.py
+```
 
 To run all python tests excluding E2E tests:
 
diff --git a/server/frontend/src/components/Buckets/ReportPreviewRow.vue b/server/frontend/src/components/Buckets/ReportPreviewRow.vue
index fe44bf55..b26fcc91 100644
--- a/server/frontend/src/components/Buckets/ReportPreviewRow.vue
+++ b/server/frontend/src/components/Buckets/ReportPreviewRow.vue
@@ -1,7 +1,9 @@
 <template>
-  <tr @click="report.view_url">
+  <tr @click="report.view_url" :class="{ warning: isNewAfterUntriage }">
     <td class="wrap-normal">
-      {{ formatShorterDate(report.reported_at) }}<br />
+      <span v-if="isNewAfterUntriage" class="label label-warning">new</span
+      ><br />
+      {{ formatShorterDate(report.reported_at) }}
       (<a :href="report.view_url">Full details</a>)
     </td>
     <td class="url-col">
@@ -96,6 +98,16 @@ export default {
       type: Object,
       required: true,
     },
+    triagedAt: {
+      type: String,
+      default: null,
+    },
+  },
+  computed: {
+    isNewAfterUntriage() {
+      if (!this.triagedAt || !this.report.reported_at) return false;
+      return new Date(this.report.reported_at) > new Date(this.triagedAt);
+    },
   },
   methods: {
     formatShorterDate: shorterDate,
diff --git a/server/frontend/src/components/Buckets/View.vue b/server/frontend/src/components/Buckets/View.vue
index 97336941..7f8cd876 100644
--- a/server/frontend/src/components/Buckets/View.vue
+++ b/server/frontend/src/components/Buckets/View.vue
@@ -31,6 +31,17 @@
               </div>
             </td>
             <td v-else>
+              <div
+                v-if="lastTriagedAt"
+                class="alert alert-warning last-triaged"
+                data-testid="untriage-warning"
+              >
+                <i class="bi bi-exclamation-triangle-fill"></i>
+                This bucket was last triaged on
+                {{ formatDate(lastTriagedAt) }} but was automatically untriaged
+                due to a spike in activity. Reports causing the spike are
+                highlighted below.
+              </div>
               No bug associated.
               <span v-if="triageStatus" data-testid="triage-status-display"
                 >Marked triaged as:
@@ -208,6 +219,7 @@
               v-else
               :key="report.id"
               :report="report"
+              :triaged-at="lastTriagedAt"
             />
           </tbody>
         </table>
@@ -313,6 +325,13 @@ export default {
     };
   },
   computed: {
+    lastTriagedAt() {
+      if (!this.triageStatus && this.triagedAt) {
+        return this.triagedAt;
+      }
+
+      return null;
+    },
     prettySignature() {
       return jsonPretty(this.bucket.signature);
     },
@@ -586,4 +605,8 @@ button[aria-expanded="false"] .bi-eye-slash-fill {
   padding: 0;
   margin: 0.25em 0 0;
 }
+
+.last-triaged {
+  max-width: 500px;
+}
 </style>
diff --git a/tests/e2e/fixtures/fixtures.json b/tests/e2e/fixtures/fixtures.json
index a849e2bb..0c0f2da5 100644
--- a/tests/e2e/fixtures/fixtures.json
+++ b/tests/e2e/fixtures/fixtures.json
@@ -231,6 +231,22 @@
       "cluster": 99999
     }
   },
+  {
+    "model": "reportmanager.bucket",
+    "pk": 888888,
+    "fields": {
+      "bug": null,
+      "color": null,
+      "description": "www.example-spike.com [Cluster 88888]",
+      "domain": "www.example-spike.com",
+      "triage_status": null,
+      "triaged_at": "2026-04-10T18:05:00+00:00",
+      "priority": 0,
+      "signature": "{\"symptoms\": [{\"type\": \"url\", \"part\": \"hostname\", \"value\": \"www.example-spike.com\"}]}",
+      "reassign_in_progress": false,
+      "cluster": 88888
+    }
+  },
   {
     "model": "reportmanager.reportentry",
     "pk": 1000,
@@ -672,6 +688,69 @@
       "cluster": 99999
     }
   },
+  {
+    "model": "reportmanager.reportentry",
+    "pk": 1021,
+    "fields": {
+      "app": 1,
+      "breakage_category": 1,
+      "bucket": 888888,
+      "comments": "Old report before triage",
+      "comments_translated": "Old report before triage",
+      "comments_original_language": "en",
+      "comments_preprocessed": "old report before triage",
+      "details": {},
+      "domain": "www.example-spike.com",
+      "ml_valid_probability": 0.9,
+      "os": 1,
+      "reported_at": "2026-04-08T18:05:00+00:00",
+      "url": "https://www.example-spike.com/",
+      "uuid": "00000000-0000-0000-0000-000000001021",
+      "cluster": 88888
+    }
+  },
+  {
+    "model": "reportmanager.reportentry",
+    "pk": 1022,
+    "fields": {
+      "app": 2,
+      "breakage_category": 1,
+      "bucket": 888888,
+      "comments": "New report after spike untriage",
+      "comments_translated": "New report after spike untriage",
+      "comments_original_language": "en",
+      "comments_preprocessed": "new report after spike untriage",
+      "details": {},
+      "domain": "www.example-spike.com",
+      "ml_valid_probability": 0.88,
+      "os": 2,
+      "reported_at": "2026-04-12T18:05:00+00:00",
+      "url": "https://www.example-spike.com/",
+      "uuid": "00000000-0000-0000-0000-000000001022",
+      "cluster": 88888
+    }
+  },
+  {
+    "model": "reportmanager.reportentry",
+    "pk": 1023,
+    "fields": {
+      "app": 3,
+      "breakage_category": 2,
+      "bucket": 888888,
+      "comments": "Another new report after spike untriage",
+      "comments_translated": "Another new report after spike untriage",
+      "comments_original_language": "en",
+      "comments_preprocessed": "another new report after spike untriage",
+      "details": {},
+      "domain": "www.example-spike.com",
+      "ml_valid_probability": 0.85,
+      "os": 3,
+      "reported_at": "2026-04-14T18:05:00+00:00",
+      "url": "https://www.example-spike.com/",
+      "uuid": "00000000-0000-0000-0000-000000001023",
+      "cluster": 88888
+    }
+  },
   {
     "model": "reportmanager.cluster",
     "pk": 70854,
@@ -711,5 +790,13 @@
       "domain": "www.example-triaged.com",
       "centroid": 1019
     }
+  },
+  {
+    "model": "reportmanager.cluster",
+    "pk": 88888,
+    "fields": {
+      "domain": "www.example-spike.com",
+      "centroid": 1021
+    }
   }
 ]
\ No newline at end of file
diff --git a/tests/e2e/fixtures/reports_data.py b/tests/e2e/fixtures/reports_data.py
index 80c8a3ff..fefc3890 100644
--- a/tests/e2e/fixtures/reports_data.py
+++ b/tests/e2e/fixtures/reports_data.py
@@ -5,7 +5,7 @@
 from django.contrib.contenttypes.models import ContentType
 from django.core.management import call_command
 
-from reportmanager.models import Bucket
+from reportmanager.models import Bucket, ReportEntry
 from reportmanager.models import User as ReportManagerUser
 
 from .defaults import TEST_USER_EMAIL, TEST_USER_PASSWORD
@@ -28,6 +28,9 @@ def e2e_data(db):
     )
     user.user_permissions.add(write_perm)
 
+    spike_bucket = Bucket.objects.get(pk=888888)
+    spike_triaged_at = spike_bucket.triaged_at
+
     return {
         "bucket_count": Bucket.objects.count(),
         "triaged_bucket_id": Bucket.objects.filter(triage_status__isnull=False)
@@ -39,4 +42,8 @@ def e2e_data(db):
         .first()
         .id,
         "triaged_count": Bucket.objects.filter(triage_status__isnull=False).count(),
+        "spike_bucket_id": spike_bucket.id,
+        "spike_new_report_count": ReportEntry.objects.filter(
+            bucket=spike_bucket, reported_at__gt=spike_triaged_at
+        ).count(),
     }
diff --git a/tests/e2e/page_objects/bucket_view.py b/tests/e2e/page_objects/bucket_view.py
index 505bc147..cd526e63 100644
--- a/tests/e2e/page_objects/bucket_view.py
+++ b/tests/e2e/page_objects/bucket_view.py
@@ -16,6 +16,7 @@ def __init__(self, page, live_server, bucket_id):
         self.triage_status_display = self.page.get_by_test_id("triage-status-display")
         self.triage_status_label = self.page.get_by_test_id("triage-status-label")
         self.unmark_option = self.page.get_by_test_id("triage-unmark")
+        self.untriage_warning = self.page.get_by_test_id("untriage-warning")
 
     def wait_for_loaded(self):
         """Wait for the bucket view's triage trigger to be visible."""
@@ -39,3 +40,6 @@ def expect_triage_label(self, text):
 
     def expect_triage_trigger(self, text):
         expect(self.triage_trigger).to_have_text(text)
+
+    def highlighted_report_rows(self):
+        return self.page.locator("tr.warning")
diff --git a/tests/e2e/scripts/generate_e2e_fixtures.py b/tests/e2e/scripts/generate_e2e_fixtures.py
index 1a94302a..7cc513d2 100644
--- a/tests/e2e/scripts/generate_e2e_fixtures.py
+++ b/tests/e2e/scripts/generate_e2e_fixtures.py
@@ -258,6 +258,45 @@
             },
         ],
     },
+    {
+        "id": 888888,
+        "domain": "www.example-spike.com",
+        "description": "www.example-spike.com [Cluster 88888]",
+        "cluster_id": 88888,
+        "priority": 0,
+        "triage_status": None,
+        "triaged_at": ANCHOR_DATE - timedelta(days=5),
+        "signature": '{"symptoms": [{"type": "url", "part": "hostname", "value": "www.example-spike.com"}]}',
+        "comments": [
+            {
+                # reported 7 days before ANCHOR_DATE = 2 days before triaged_at -> not highlighted
+                "reported_at": ANCHOR_DATE - timedelta(days=7),
+                "comments": "Old report before triage",
+                "comments_translated": "Old report before triage",
+                "comments_original_language": "en",
+                "breakage_category": "load",
+                "ml_valid_probability": 0.9,
+            },
+            {
+                # reported 3 days before ANCHOR_DATE = 2 days after triaged_at -> highlighted
+                "reported_at": ANCHOR_DATE - timedelta(days=3),
+                "comments": "New report after spike untriage",
+                "comments_translated": "New report after spike untriage",
+                "comments_original_language": "en",
+                "breakage_category": "load",
+                "ml_valid_probability": 0.88,
+            },
+            {
+                # reported 1 day before ANCHOR_DATE = 4 days after triaged_at -> highlighted
+                "reported_at": ANCHOR_DATE - timedelta(days=1),
+                "comments": "Another new report after spike untriage",
+                "comments_translated": "Another new report after spike untriage",
+                "comments_original_language": "en",
+                "breakage_category": "media",
+                "ml_valid_probability": 0.85,
+            },
+        ],
+    },
 ]
 
 # Supporting data
@@ -375,7 +414,11 @@ def generate_fixtures():
                 comments_translated.lower() if comments_translated else ""
             )
 
-            days_ago = date_offsets[i % len(date_offsets)]
+            if "reported_at" in comment_data:
+                reported_at = comment_data["reported_at"]
+            else:
+                days_ago = date_offsets[i % len(date_offsets)]
+                reported_at = ANCHOR_DATE - timedelta(days=days_ago)
 
             fixture.append(
                 {
@@ -396,9 +439,7 @@ def generate_fixtures():
                         "domain": bucket_config["domain"],
                         "ml_valid_probability": comment_data["ml_valid_probability"],
                         "os": (i % len(OS_DATA)) + 1,  # Rotate through all OS
-                        "reported_at": (
-                            ANCHOR_DATE - timedelta(days=days_ago)
-                        ).isoformat(),
+                        "reported_at": reported_at.isoformat(),
                         "url": f"https://{bucket_config['domain']}/",
                         "uuid": f"00000000-0000-0000-0000-{report_id:012d}",
                         "cluster": bucket_config["cluster_id"],
diff --git a/tests/e2e/test_bucket_view.py b/tests/e2e/test_bucket_view.py
index 3cb6c1d2..333cb638 100644
--- a/tests/e2e/test_bucket_view.py
+++ b/tests/e2e/test_bucket_view.py
@@ -1,4 +1,5 @@
 import pytest
+from playwright.sync_api import expect
 
 from .page_objects.bucket_view import BucketViewPage
 
@@ -50,3 +51,16 @@ def test_change_and_unmark_triage_status(bucket_view_page, e2e_data):
     bucket_view.unmark_triage()
     bucket_view.expect_triage_trigger("Mark triaged")
     assert bucket_view.triage_status_display.count() == 0
+
+
+@pytest.mark.ui
+@pytest.mark.django_db(transaction=True)
+def test_spike_untriage_warning_shown(bucket_view_page, e2e_data):
+    bucket_view = bucket_view_page(e2e_data["spike_bucket_id"])
+
+    # Warning banner should be visible since triage_status is None but triaged_at is set
+    expect(bucket_view.untriage_warning).to_be_visible()
+    expect(bucket_view.untriage_warning).to_contain_text("spike in activity")
+    expect(bucket_view.highlighted_report_rows()).to_have_count(
+        e2e_data["spike_new_report_count"]
+    )