diff --git a/.github/scripts/minimal_smoke.py b/.github/scripts/minimal_smoke.py
new file mode 100644
index 0000000..38cd537
--- /dev/null
+++ b/.github/scripts/minimal_smoke.py
@@ -0,0 +1,120 @@
+"""Smoke test for a MINIMAL installation of bluesky-tiled-plugins.
+
+Run with plain python (not pytest) in an environment where only the package and
+its declared runtime dependencies are installed -- no extras, no dev/test
+dependency groups:
+
+    uv venv && uv pip install . && .venv/bin/python .github/scripts/minimal_smoke.py
+
+It verifies that the declared runtime dependencies are sufficient: every
+submodule imports, the client-side writing machinery works, and the optional
+ragged dependencies are genuinely absent (so this script will fail by design
+if run in a full dev/test environment).
+"""
+
+import importlib
+import pkgutil
+import traceback
+
+import bluesky_tiled_plugins as btp
+
+# Modules that intentionally require tiled[server] and are only imported in
+# server deployments (e.g. mounted via the server config).
+SERVER_ONLY = {"bluesky_tiled_plugins.routers.validator"}
+
+failures = []
+for mod in pkgutil.walk_packages(btp.__path__, btp.__name__ + "."):
+    if mod.name in SERVER_ONLY:
+        continue
+    try:
+        importlib.import_module(mod.name)
+    except Exception:
+        failures.append((mod.name, traceback.format_exc()))
+
+for name, tb in failures:
+    print(f"FAILED IMPORT: {name}\n{tb}")
+if failures:
+    raise SystemExit(f"{len(failures)} module(s) failed to import; see above.")
+
+# The public API is usable.
+from bluesky_tiled_plugins import TiledInserter, TiledWriter  # noqa: E402, F401
+from bluesky_tiled_plugins.writing.consolidators import (  # noqa: E402
+    consolidator_factory,
+)
+from bluesky_tiled_plugins.writing.tiled_writer import RunNormalizer  # noqa: E402
+
+# The document-processing machinery works without a server.
+received = []
+normalizer = RunNormalizer()
+normalizer.subscribe(lambda name, doc: received.append(name))
+normalizer("start", {"uid": "u1", "time": 0.0})
+normalizer(
+    "descriptor",
+    {
+        "uid": "d1",
+        "run_start": "u1",
+        "time": 0.0,
+        "name": "primary",
+        "data_keys": {"x": {"source": "s", "dtype": "number", "shape": []}},
+        "object_keys": {"det": ["x"]},
+        "configuration": {},
+        "hints": {},
+    },
+)
+normalizer(
+    "event",
+    {
+        "uid": "e1",
+        "descriptor": "d1",
+        "time": 1.0,
+        "seq_num": 1,
+        "data": {"x": 1.0},
+        "timestamps": {"x": 1.0},
+        "filled": {},
+    },
+)
+normalizer(
+    "stop",
+    {
+        "uid": "s1",
+        "run_start": "u1",
+        "time": 2.0,
+        "exit_status": "success",
+        "reason": "",
+        "num_events": {"primary": 1},
+    },
+)
+assert "start" in received and "stop" in received, received
+
+consolidator = consolidator_factory(
+    {
+        "data_key": "img",
+        "uri": "file:///x",
+        "mimetype": "multipart/related;type=image/tiff",
+        "parameters": {"chunk_shape": (1, 5, 7), "template": "f_{:06d}.tiff"},
+    },
+    {
+        "data_keys": {
+            "img": {"shape": [3, 5, 7], "dtype": "array", "dtype_numpy": "|u1"}
+        }
+    },
+)
+consolidator.consume_stream_datum(
+    {"indices": {"start": 0, "stop": 1}, "seq_nums": {"start": 1, "stop": 2}}
+)
+assert consolidator.shape and consolidator.assets
+assert consolidator.structure() is not None
+
+# The optional ragged dependencies must NOT be present in a minimal install;
+# this guards against them sneaking back in through a transitive dependency
+# (install bluesky-tiled-plugins[ragged] to get them).
+try:
+    import tiled.structures.ragged  # noqa: F401
+except ImportError:
+    pass
+else:
+    raise SystemExit(
+        "tiled.structures.ragged is importable: the environment is not minimal."
+    )
+
+print("Minimal installation smoke test: OK")
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0809d01..4561fa5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -11,6 +11,11 @@ concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
   cancel-in-progress: true
 
+# The jobs only check out the repo and run tests; the codecov upload uses its
+# own CODECOV_TOKEN secret, not the GITHUB_TOKEN.
+permissions:
+  contents: read
+
 env:
   # Many color libraries just need this variable to be set to any value.
   # Set it to 3 to support 8-bit color graphics (256 colors per channel)
@@ -90,6 +95,39 @@ jobs:
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
 
+  # Verify that the declared runtime dependencies are sufficient on their own:
+  # install the package with no extras and no dev/test dependency groups (so
+  # e.g. tiled[server] in the test group does not mask a missing runtime
+  # dependency) and smoke test it. See .github/scripts/minimal_smoke.py.
+  minimal-install:
+    name: Minimal install / Python ${{ matrix.python-version }}
+    runs-on: ubuntu-latest
+    needs: [pre-commit]
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ["3.10", "3.13"]
+
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          fetch-depth: 0
+
+      - uses: actions/setup-python@v7
+        with:
+          python-version: ${{ matrix.python-version }}
+          allow-prereleases: true
+
+      - uses: astral-sh/setup-uv@v7
+
+      - name: Install package without extras or dependency groups
+        run: |
+          uv venv --python ${{ matrix.python-version }}
+          uv pip install .
+
+      - name: Smoke test the minimal installation
+        run: .venv/bin/python .github/scripts/minimal_smoke.py
+
   # Windows and macOS jobs run without Mongo/Redis. Tests gated on
   # TEST_MONGO_URI / TEST_REDIS_URI skip themselves automatically.
   other-checks:
diff --git a/pyproject.toml b/pyproject.toml
index f14966b..30d23f6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -37,9 +37,26 @@ dependencies = [
   "dask",
   "event-model",
   "mongoquery",
+  "ndindex",  # imported by tiled.ndslice
+  "numpy",
+  "pandas",
+  "pyarrow",
   "pytz",
-  "tiled[client] >=0.2.15",
+  "tiled[minimal-client] >=0.2.19",
   "tzlocal",
+  "xarray",
+]
+
+[project.optional-dependencies]
+# Writing ragged (variable-length) array data; imported lazily by TiledWriter.
+# Pins match the tiled[client] extra.
+ragged = [
+  "awkward >=2.4.3",
+  "ragged",
+]
+# All optional features.
+all = [
+  "bluesky-tiled-plugins[ragged]",
 ]
 
 
@@ -71,7 +88,7 @@ test = [
   "redis-json-dict",
   "suitcase-mongo",
   "tifffile",
-  "tiled[server] >=0.2.15",
+  "tiled[server] >=0.2.19",
 ]
 dev = [{ include-group = "test" }]
 docs = [
diff --git a/src/bluesky_tiled_plugins/writing/tiled_writer.py b/src/bluesky_tiled_plugins/writing/tiled_writer.py
index be436df..3d6e494 100644
--- a/src/bluesky_tiled_plugins/writing/tiled_writer.py
+++ b/src/bluesky_tiled_plugins/writing/tiled_writer.py
@@ -816,7 +816,14 @@ def _write_internal_data(
 
         # 2. Write internal ragged array data, if any; remove it from the tabular data
         for key in self._int_ragged_array_keys[desc_name]:
-            from tiled.structures.ragged import make_ragged_array
+            try:
+                from tiled.structures.ragged import make_ragged_array
+            except ImportError as err:
+                raise ImportError(
+                    "Writing ragged (variable-length) array data requires optional "
+                    "dependencies. Install them with: "
+                    "pip install bluesky-tiled-plugins[ragged]"
+                ) from err
 
             arr_lst = [row.pop(key) for row in data_cache if key in row]
             shape = (len(arr_lst), *self.data_keys[key].get("shape", ()))