fix: avoid versioned describe table for namespace opens

java/src/main/java/org/lance/OpenDatasetBuilder.java

@@ -216,8 +216,8 @@ private Dataset buildFromNamespaceClient() {
     // Call describe_table to get location and storage options
     DescribeTableRequest request = new DescribeTableRequest();
     request.setId(tableId);
-    // Only set version if present
-    options.getVersion().ifPresent(v -> request.setVersion(Long.valueOf(v)));
+    // Do not set the dataset version here. Some namespace implementations only support describing
+    // the latest table metadata; the requested version is applied when opening the dataset below.
 
     DescribeTableResponse response = namespaceClient.describeTable(request);
 

java/src/test/java/org/lance/namespace/DirectoryNamespaceTest.java

@@ -189,6 +189,33 @@ void testNamespaceId() {
         "namespaceId should contain 'DirectoryNamespace', got: " + namespaceId);
   }
 
+  @Test
+  void testOpenSpecificVersionDoesNotPassVersionToDescribeTable() throws Exception {
+    VersionRejectingNamespace versionRejectingNamespace =
+        new VersionRejectingNamespace(innerNamespaceClient);
+    namespaceClient = versionRejectingNamespace;
+    List<String> tableId = Arrays.asList("test_table");
+
+    namespaceClient.createTable(new CreateTableRequest().id(tableId), createTestTableData());
+    namespaceClient.insertIntoTable(
+        new InsertIntoTableRequest().id(tableId).mode("append"), createTestTableData());
+
+    try (Dataset versionOne =
+        Dataset.open()
+            .allocator(allocator)
+            .namespaceClient(namespaceClient)
+            .tableId(tableId)
+            .readOptions(new ReadOptions.Builder().setVersion(1L).build())
+            .build()) {
+      assertEquals(1, versionOne.version());
+      assertEquals(3, versionOne.countRows());
+    }
+
+    assertTrue(
+        versionRejectingNamespace.getDescribeTableCallCount() > 0,
+        "Expected describeTable to be called when opening through namespace");
+  }
+
   @Test
   void testCreateAndListNamespaces() {
     // Create a namespace
@@ -1439,4 +1466,25 @@ private byte[] createVectorTableData(int numRows, int dim) throws Exception {
       return out.toByteArray();
     }
   }
+
+  private static class VersionRejectingNamespace extends CustomNamespace {
+    private final AtomicInteger describeTableCallCount = new AtomicInteger();
+
+    VersionRejectingNamespace(DirectoryNamespace inner) {
+      super(inner);
+    }
+
+    @Override
+    public DescribeTableResponse describeTable(DescribeTableRequest request) {
+      describeTableCallCount.incrementAndGet();
+      assertNull(
+          request.getVersion(),
+          "Dataset version should be passed to dataset open, not describeTable");
+      return super.describeTable(request);
+    }
+
+    int getDescribeTableCallCount() {
+      return describeTableCallCount.get();
+    }
+  }
 }

python/python/lance/__init__.py

@@ -230,7 +230,9 @@ def dataset(
                 "Both 'namespace_client' and 'table_id' must be provided together."
             )
 
-        request = DescribeTableRequest(id=table_id, version=version)
+        # Resolve the latest table metadata here. The requested dataset version is
+        # applied by the lower-level dataset open path after namespace resolution.
+        request = DescribeTableRequest(id=table_id, version=None)
         response = namespace_client.describe_table(request)
 
         uri = response.location

python/python/tests/test_namespace_dir.py

@@ -979,6 +979,49 @@ def test_external_manifest_store_invokes_namespace_apis(use_custom):
         ), "describe_table_version should be called once when opening version 1"
 
 
+def test_dataset_namespace_open_does_not_pass_version_to_describe_table():
+    """Dataset versions are applied to dataset open, not namespace describe_table."""
+
+    class VersionRejectingNamespace(CustomNamespace):
+        def __init__(self, inner: lance.namespace.DirectoryNamespace):
+            super().__init__(inner)
+            self.describe_versions = []
+
+        def describe_table(
+            self, request: DescribeTableRequest
+        ) -> DescribeTableResponse:
+            self.describe_versions.append(request.version)
+            assert request.version is None
+            return super().describe_table(request)
+
+    with tempfile.TemporaryDirectory() as tmpdir:
+        inner_ns_client = lance.namespace.DirectoryNamespace(root=tmpdir)
+        ns_client = VersionRejectingNamespace(inner_ns_client)
+        table_id = ["test_table"]
+
+        table1 = pa.Table.from_pylist([{"a": 1}, {"a": 2}])
+        ds = lance.write_dataset(
+            table1, namespace_client=ns_client, table_id=table_id, mode="create"
+        )
+        assert ds.count_rows() == 2
+        assert ds.version == 1
+
+        table2 = pa.Table.from_pylist([{"a": 3}])
+        ds = lance.write_dataset(
+            table2, namespace_client=ns_client, table_id=table_id, mode="append"
+        )
+        assert ds.count_rows() == 3
+        assert ds.version == 2
+
+        version_one = lance.dataset(
+            namespace_client=ns_client, table_id=table_id, version=1
+        )
+        assert version_one.count_rows() == 2
+        assert version_one.version == 1
+        assert ns_client.describe_versions
+        assert all(version is None for version in ns_client.describe_versions)
+
+
 @pytest.mark.skipif(
     sys.platform == "win32",
     reason="Windows file locking prevents reliable concurrent filesystem operations",