diff --git a/sdk/python/feast/cli/cli.py b/sdk/python/feast/cli/cli.py
index 886c91f69ae..a549a5f41b3 100644
--- a/sdk/python/feast/cli/cli.py
+++ b/sdk/python/feast/cli/cli.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 import json
 import logging
+import sys
 from datetime import datetime
 from importlib.metadata import version as importlib_version
 from pathlib import Path
@@ -49,7 +50,7 @@
 from feast.cli.ui import ui
 from feast.cli.validation_references import validation_references_cmd
 from feast.constants import FEAST_FS_YAML_FILE_PATH_ENV_NAME
-from feast.errors import FeastProviderLoginError
+from feast.errors import FeastError, FeastProviderLoginError
 from feast.repo_config import load_repo_config
 from feast.repo_operations import (
     apply_total,
@@ -258,6 +259,9 @@ def plan_command(
         plan(repo_config, repo, skip_source_validation, skip_feature_view_validation)
     except FeastProviderLoginError as e:
         print(str(e))
+    except FeastError as e:
+        print(str(e))
+        sys.exit(1)
 
 
 @cli.command("apply", cls=NoOptionDefaultFormat)
@@ -316,6 +320,9 @@ def apply_total_command(
         )
     except FeastProviderLoginError as e:
         print(str(e))
+    except FeastError as e:
+        print(str(e))
+        sys.exit(1)
 
 
 @cli.command("teardown", cls=NoOptionDefaultFormat)
diff --git a/sdk/python/feast/repo_operations.py b/sdk/python/feast/repo_operations.py
index 28fe86602ad..7e8e2cf175b 100644
--- a/sdk/python/feast/repo_operations.py
+++ b/sdk/python/feast/repo_operations.py
@@ -21,6 +21,7 @@
 from feast.data_source import DataSource, KafkaSource, KinesisSource
 from feast.diff.registry_diff import extract_objects_for_keep_delete_update_add
 from feast.entity import Entity
+from feast.errors import ConflictingFeatureViewNames, DataSourceRepeatNamesException
 from feast.feature_service import FeatureService
 from feast.feature_store import FeatureStore
 from feast.feature_view import DUMMY_ENTITY, FeatureView
@@ -219,6 +220,33 @@ def parse_repo(repo_root: Path) -> RepoContents:
             elif isinstance(obj, Project) and not any((obj is p) for p in res.projects):
                 res.projects.append(obj)
 
+    # Early duplicate detection: validate feature view names are case-insensitively unique
+    # This runs before FeatureStore initialization to avoid slow cleanup on error
+    fv_names_seen = {}
+    all_feature_views = (
+        res.feature_views + res.stream_feature_views + res.on_demand_feature_views
+    )
+    for fv in all_feature_views:
+        lower_name = fv.name.lower()
+        if lower_name in fv_names_seen:
+            existing_fv = fv_names_seen[lower_name]
+            raise ConflictingFeatureViewNames(
+                fv.name,
+                existing_type=type(existing_fv).__name__,
+                new_type=type(fv).__name__,
+            )
+        fv_names_seen[lower_name] = fv
+
+    # Early duplicate detection: validate data source names are case-insensitively unique
+    ds_names_seen = {}
+    for ds in res.data_sources:
+        if ds.name is None:
+            continue
+        lower_name = ds.name.lower()
+        if lower_name in ds_names_seen:
+            raise DataSourceRepeatNamesException(ds.name)
+        ds_names_seen[lower_name] = ds
+
     res.entities.append(DUMMY_ENTITY)
     return res