diff --git a/tests/test_delegated_writers.py b/tests/test_delegated_writers.py
new file mode 100644
index 0000000..a4a96c5
--- /dev/null
+++ b/tests/test_delegated_writers.py
@@ -0,0 +1,92 @@
+"""Integration coverage for utility writes delegated to copick core."""
+
+from types import SimpleNamespace
+
+import numpy as np
+import pytest
+import zarr
+from copick.impl.filesystem import CopickConfigFSSpec, CopickRootFSSpec
+from copick.util.ome import get_level_path
+from copick_utils.converters import lazy_converter
+from copick_utils.io import writers
+from copick_utils.process.rescale import rescale_segmentation
+
+
+@pytest.fixture
+def run(tmp_path):
+    config = CopickConfigFSSpec(
+        pickable_objects=[],
+        overlay_root=f"local://{tmp_path}",
+        overlay_fs_args={"auto_mkdir": True},
+    )
+    return CopickRootFSSpec(config).new_run("run")
+
+
+def _assert_canonical_volume(entity, expected):
+    group = zarr.open_group(store=entity.zarr(), mode="r")
+    level = group[get_level_path(group, 0)]
+
+    assert group.metadata.zarr_format == 3
+    assert group.attrs["ome"]["version"] == "0.5"
+    assert level.metadata.dimension_names == ("z", "y", "x")
+    assert level.chunks == (128, 128, 128)
+    np.testing.assert_array_equal(level[:], expected)
+
+
+def test_io_writers_delegate_canonical_tomogram_and_segmentation_output(run):
+    volume = np.arange(4 * 5 * 6, dtype=np.float32).reshape(4, 5, 6)
+    labels = (volume % 3).astype(np.uint8)
+
+    writers.tomogram(run, volume, voxel_size=10, algorithm="wbp")
+    writers.segmentation(run, labels, "writer", name="source", voxel_size=10)
+
+    tomogram = run.get_voxel_spacing(10).get_tomogram("wbp")
+    segmentation = run.get_segmentations(name="source")[0]
+    _assert_canonical_volume(tomogram, volume)
+    _assert_canonical_volume(segmentation, labels)
+
+
+def test_processor_reads_and_writes_through_copick_entities(run):
+    volume = np.arange(4 * 5 * 6, dtype=np.float32).reshape(4, 5, 6)
+    labels = (volume % 3).astype(np.uint8)
+    writers.tomogram(run, volume, voxel_size=10, algorithm="wbp")
+    writers.segmentation(run, labels, "writer", name="source", voxel_size=10)
+    source = run.get_segmentations(name="source")[0]
+
+    derived, stats = rescale_segmentation(
+        source,
+        run,
+        object_name="derived",
+        session_id="1",
+        user_id="processor",
+        target_voxel_spacing=10,
+        tomo_type="wbp",
+    )
+
+    assert stats == {"rescaled": 1, "labels_preserved": 1}
+    _assert_canonical_volume(derived, labels)
+
+
+def test_lazy_worker_preserves_core_writer_failure(monkeypatch):
+    task = {
+        "segmentation": SimpleNamespace(session_id="input"),
+        "object_name": "derived",
+        "user_id": "processor",
+        "session_id": "1",
+        "voxel_spacing": 10,
+    }
+    monkeypatch.setattr(lazy_converter, "discover_tasks_for_run", lambda run, selector: [task])
+
+    def reject_write(**kwargs):
+        raise ValueError("requested shard exceeds the configured size limit")
+
+    result = lazy_converter.lazy_conversion_worker(
+        run=SimpleNamespace(name="run"),
+        config=SimpleNamespace(type="single_selector", selector=object()),
+        converter_func=reject_write,
+    )
+
+    assert result["processed"] == 0
+    assert result["errors"] == [
+        "Error processing task in run: requested shard exceeds the configured size limit",
+    ]