diff --git a/apps/trip-cluster/app/ingest.py b/apps/trip-cluster/app/ingest.py
index d207ad0..87e2ec6 100644
--- a/apps/trip-cluster/app/ingest.py
+++ b/apps/trip-cluster/app/ingest.py
@@ -45,14 +45,23 @@ def run_ingest(client, store, thumbs_dir, *, date_from=None, date_to=None,
         if need_thumb:
             try:
                 data = client.download_thumbnail(a["id"])
-                # Write to a temp path and os.replace into place so a failure
-                # never leaves a 0-byte <id>.jpg behind.
-                tmp_path = f"{thumb_path}.tmp"
+            except Exception:
+                log.exception("Thumbnail download failed for asset %s", a["id"])
+                continue
+            # Write to a temp path and os.replace into place so a failure
+            # never leaves a 0-byte <id>.jpg behind; clean up the temp file
+            # if the write itself fails (e.g. disk full).
+            tmp_path = f"{thumb_path}.tmp"
+            try:
                 with open(tmp_path, "wb") as f:
                     f.write(data)
                 os.replace(tmp_path, thumb_path)
             except Exception:
-                log.exception("Thumbnail download failed for asset %s", a["id"])
+                log.exception("Thumbnail write failed for asset %s", a["id"])
+                try:
+                    os.unlink(tmp_path)
+                except OSError:
+                    pass
                 continue
 
         store.upsert_asset(Asset(
diff --git a/apps/trip-cluster/app/routes/review.py b/apps/trip-cluster/app/routes/review.py
index 0d26f18..6ee5805 100644
--- a/apps/trip-cluster/app/routes/review.py
+++ b/apps/trip-cluster/app/routes/review.py
@@ -113,9 +113,8 @@ def apply_one(cid):
     # Lazy import: app.writeback is owned by a later task and may be absent
     # at app-startup; importing here keeps the blueprint importable regardless.
     from app.writeback import apply_cluster
-    s = _store()
-    res = apply_cluster(_client(), s, cid)
-    s.close()
+    with _store() as s:               # close even if the Immich write-back raises
+        res = apply_cluster(_client(), s, cid)
     return jsonify(res)
 
 
@@ -123,7 +122,6 @@ def apply_one(cid):
 def apply_everything():
     # Lazy import: see apply_one above.
     from app.writeback import apply_all
-    s = _store()
-    results = apply_all(_client(), s)
-    s.close()
+    with _store() as s:               # close even if the Immich write-back raises
+        results = apply_all(_client(), s)
     return jsonify({"results": results})
diff --git a/apps/trip-cluster/app/static/app.js b/apps/trip-cluster/app/static/app.js
index 7745dc0..9cd3235 100644
--- a/apps/trip-cluster/app/static/app.js
+++ b/apps/trip-cluster/app/static/app.js
@@ -136,6 +136,8 @@ function clusterReview() {
       location.reload();
     },
     async apply() {
+      // Write-back needs explicit confirmation (mirrors applyAll/merge).
+      if (!confirm('Apply this cluster’s decision to Immich?')) return;
       const r = await this.post(`/cluster/${this.selected}/apply`, {});
       alert(`Applied ${r.succeeded.length}, failed ${r.failed.length}.`);
     },
diff --git a/apps/trip-cluster/app/writeback.py b/apps/trip-cluster/app/writeback.py
index 7416583..663e94e 100644
--- a/apps/trip-cluster/app/writeback.py
+++ b/apps/trip-cluster/app/writeback.py
@@ -3,11 +3,15 @@ from photoflow.immich import pipeline
 APPLYABLE = ("approved", "non_trip", "skipped")
 
 
-def _apply_tag(client, store, asset_ids, action, tag, tag_id):
+def _apply_tag(client, store, asset_ids, action, tag):
     todo = [a for a in asset_ids if not store.already_applied(a, action, tag)]
     if not todo:
         return [], []
     try:
+        # upsert_tag is part of the write: a failure here must be caught and
+        # recorded like a tag_assets failure, not propagate out of apply_cluster
+        # (which would abort the whole apply_all batch and skip later clusters).
+        tag_id = client.upsert_tag(tag)
         client.tag_assets(tag_id, todo)
     except Exception as e:                       # noqa: BLE001 — recorded, surfaced
         for a in todo:
@@ -29,12 +33,11 @@ def apply_cluster(client, store, cluster_id) -> dict:
 
     if c.status == "approved":
         tag = c.decided_name or c.suggested_name
-        ok, fail = _apply_tag(client, store, included, "trip", tag, client.upsert_tag(tag))
+        ok, fail = _apply_tag(client, store, included, "trip", tag)
         succeeded += ok
         failed += fail
     elif c.status == "non_trip":
-        ok, fail = _apply_tag(client, store, included, "non-trip", pipeline.NON_TRIP,
-                              client.upsert_tag(pipeline.NON_TRIP))
+        ok, fail = _apply_tag(client, store, included, "non-trip", pipeline.NON_TRIP)
         succeeded += ok
         failed += fail
     # 'skipped': no content/non-trip tag, only processed below.
@@ -42,8 +45,10 @@ def apply_cluster(client, store, cluster_id) -> dict:
     failed_ids = {i for i, _ in failed}
     proc_targets = [a for a in included if a not in failed_ids]
     if proc_targets:
-        _apply_tag(client, store, proc_targets, "processed", pipeline.PROCESSED,
-                   client.upsert_tag(pipeline.PROCESSED))
+        # Surface processed-marker failures too — a discarded return here makes a
+        # failed _pipeline/processed write look like success in the CLI/UI summary.
+        _, proc_fail = _apply_tag(client, store, proc_targets, "processed", pipeline.PROCESSED)
+        failed += proc_fail
         for a in proc_targets:
             if store.already_applied(a, "processed", pipeline.PROCESSED):
                 store.mark_processed(a)
diff --git a/apps/trip-cluster/tests/test_writeback.py b/apps/trip-cluster/tests/test_writeback.py
index 9deb8d6..7233c8e 100644
--- a/apps/trip-cluster/tests/test_writeback.py
+++ b/apps/trip-cluster/tests/test_writeback.py
@@ -8,9 +8,12 @@ class FakeImmich:
     def __init__(self):
         self.tagged = []
         self.fail_tag_id = None
+        self.fail_upsert = None          # tag name whose upsert_tag should raise
         self._ids = {}
 
     def upsert_tag(self, name):
+        if self.fail_upsert is not None and name == self.fail_upsert:
+            raise RuntimeError("upsert boom")
         self._ids.setdefault(name, f"id:{name}")
         return self._ids[name]
 
@@ -111,3 +114,35 @@ def test_apply_skipped(tmp_path):
     assert s.get_asset("a").processed is True
     assert s.get_asset("b").processed is True
     s.close()
+
+
+def test_upsert_tag_failure_is_caught_and_does_not_abort_batch(tmp_path):
+    # A failing upsert_tag must be recorded as a per-asset failure (retryable),
+    # not propagate out of apply_cluster and abort apply_all (review finding R1).
+    s = _store(tmp_path)
+    _approved(s, name="Venice")
+    _approved(s, name="Rome")           # second cluster must still be applied
+    client = FakeImmich()
+    client.fail_upsert = "Venice"       # first cluster's trip-tag upsert fails
+    results = apply_all(client, s)
+    assert len(results) == 2            # batch was not aborted by the first failure
+    venice = next(r for r in results if r["cluster_id"] == 1)
+    assert venice["succeeded"] == [] and sorted(i for i, _ in venice["failed"]) == ["a", "b"]
+    assert s.already_applied("a", "trip", "Venice") is False   # retryable
+    rome = next(r for r in results if r["cluster_id"] == 2)
+    assert sorted(rome["succeeded"]) == ["a", "b"]
+    s.close()
+
+
+def test_processed_write_failure_is_surfaced_in_result(tmp_path):
+    # Trip tag succeeds but the _pipeline/processed write fails: the failure must
+    # appear in result["failed"] and the asset must NOT be marked processed.
+    s = _store(tmp_path)
+    cid = _approved(s, name="Venice")
+    client = FakeImmich()
+    client.fail_upsert = pipeline.PROCESSED
+    res = apply_cluster(client, s, cid)
+    assert sorted(res["succeeded"]) == ["a", "b"]              # trip tag still applied
+    assert sorted(i for i, _ in res["failed"]) == ["a", "b"]  # processed surfaced
+    assert s.get_asset("a").processed is False
+    s.close()
diff --git a/shared/photoflow/core/store.py b/shared/photoflow/core/store.py
index 32c67ab..9fafa52 100644
--- a/shared/photoflow/core/store.py
+++ b/shared/photoflow/core/store.py
@@ -67,6 +67,8 @@ CREATE TABLE IF NOT EXISTS writeback_log (
 CREATE INDEX IF NOT EXISTS idx_assets_taken_at ON assets(taken_at);
 CREATE INDEX IF NOT EXISTS idx_members_cluster ON cluster_members(cluster_id);
 CREATE INDEX IF NOT EXISTS idx_members_asset ON cluster_members(immich_id);
+CREATE INDEX IF NOT EXISTS idx_writeback_lookup
+  ON writeback_log(immich_id, action, tag, result);
 """
 
 
@@ -109,6 +111,12 @@ class Store:
             self._conn.close()
             self._conn = None
 
+    def __enter__(self) -> "Store":
+        return self
+
+    def __exit__(self, *exc) -> None:
+        self.close()
+
     def upsert_asset(self, a: Asset) -> None:
         has_gps = 1 if (a.gps_lat is not None and a.gps_lon is not None) else 0
         self.conn.execute(
@@ -284,6 +292,10 @@ class Store:
         if boundary_immich_id not in ids:
             raise ValueError(f"boundary {boundary_immich_id!r} not in cluster")
         idx = ids.index(boundary_immich_id)
+        if idx == 0:
+            raise ValueError(
+                f"boundary {boundary_immich_id!r} is the first member; "
+                "split would leave an empty cluster")
         base = self.get_cluster(cluster_id)
         left, right = pairs[:idx], pairs[idx:]
 
diff --git a/shared/photoflow/ui/templates/macros.html b/shared/photoflow/ui/templates/macros.html
index 76430b0..872e6be 100644
--- a/shared/photoflow/ui/templates/macros.html
+++ b/shared/photoflow/ui/templates/macros.html
@@ -10,7 +10,7 @@
   {% elif confidence < 0.75 %}
     <span class="badge badge-sm badge-info">med</span>
   {% else %}
-    <span class="badge badge-sm badge-success">high</span>
+    <span class="badge badge-sm badge-success" title="high-confidence">high</span>
   {% endif %}
 {% endmacro %}
 
diff --git a/shared/tests/test_store_clusters.py b/shared/tests/test_store_clusters.py
index d8bddd8..bee53ad 100644
--- a/shared/tests/test_store_clusters.py
+++ b/shared/tests/test_store_clusters.py
@@ -97,3 +97,14 @@ def test_writeback_log_idempotency(tmp_path):
     s.log_writeback("b", "trip", "Venice", "error:boom")
     assert s.already_applied("b", "trip", "Venice") is False  # only ok counts
     s.close()
+
+
+def test_split_cluster_rejects_first_member_boundary(tmp_path):
+    import pytest
+    s = _seed(tmp_path)
+    cid = s.insert_cluster(Cluster(start_at="2019-06-01", end_at="2019-06-03",
+                                   suggested_name="Trip"), _members(["a", "b", "c"]))
+    with pytest.raises(ValueError):
+        s.split_cluster(cid, "a")          # boundary == first member -> empty left
+    assert s.get_cluster(cid).status != "split"   # original untouched on rejection
+    s.close()