diff --git a/ingestify/domain/models/ingestion/ingestion_job.py b/ingestify/domain/models/ingestion/ingestion_job.py
index 959480e..6b3b0b5 100644
--- a/ingestify/domain/models/ingestion/ingestion_job.py
+++ b/ingestify/domain/models/ingestion/ingestion_job.py
@@ -129,7 +129,6 @@ def run(self):
         with TaskSummary.update(
             self.task_id, dataset_identifier=dataset_identifier
         ) as task_summary:
-
             files = {
                 file_id: task_summary.record_load_file(
                     lambda: load_file(file_resource, dataset=self.dataset),
@@ -138,6 +137,8 @@ def run(self):
                 for file_id, file_resource in self.dataset_resource.files.items()
             }
 
+            self.dataset_resource.run_post_load_files(files)
+
             try:
                 revision = self.store.update_dataset(
                     dataset=self.dataset,
@@ -181,6 +182,9 @@ def run(self):
                 )
                 for file_id, file_resource in self.dataset_resource.files.items()
             }
+
+            self.dataset_resource.run_post_load_files(files)
+
             try:
                 revision = self.store.create_dataset(
                     dataset_type=self.dataset_resource.dataset_type,
diff --git a/ingestify/domain/models/resources/dataset_resource.py b/ingestify/domain/models/resources/dataset_resource.py
index 7473bf5..9b00f72 100644
--- a/ingestify/domain/models/resources/dataset_resource.py
+++ b/ingestify/domain/models/resources/dataset_resource.py
@@ -1,5 +1,5 @@
 from datetime import datetime
-from typing import Optional, Callable, Any, Protocol, TYPE_CHECKING  # noqa
+from typing import Optional, Callable, Any, Protocol, TYPE_CHECKING, Dict  # noqa
 from pydantic import Field
 
 from ingestify.domain.models.base import BaseModel
@@ -50,6 +50,18 @@ class DatasetResource(BaseModel):
     metadata: dict = Field(default_factory=dict)
     state: DatasetState = Field(default_factory=lambda: DatasetState.COMPLETE)
     files: dict[str, FileResource] = Field(default_factory=dict)
+    post_load_files: Optional[
+        Callable[["DatasetResource", Dict[str, DraftFile]], None]
+    ] = None
+
+    def run_post_load_files(self, files: Dict[str, DraftFile]):
+        """Hook to modify dataset attributes based on loaded file content.
+
+        Useful for setting state based on file content, e.g., keep state=SCHEDULED
+        when files contain '{}', change to COMPLETE when they contain actual data.
+        """
+        if self.post_load_files:
+            self.post_load_files(self, files)
 
     def add_file(
         self,
diff --git a/ingestify/infra/fetch/http.py b/ingestify/infra/fetch/http.py
index bfee22a..7ec418f 100644
--- a/ingestify/infra/fetch/http.py
+++ b/ingestify/infra/fetch/http.py
@@ -58,9 +58,9 @@ def retrieve_http(
             )
         # else:
         #     print(f"{current_file.modified_at=} {last_modified=}")
-        # headers["if-modified-since"] = (
-        #     format_datetime(current_file.modified_at, usegmt=True),
-        # )
+        headers["if-modified-since"] = (
+            format_datetime(current_file.modified_at, usegmt=True),
+        )
         headers["if-none-match"] = current_file.tag
 
     http_kwargs = {}
diff --git a/ingestify/tests/test_engine.py b/ingestify/tests/test_engine.py
index e26feda..23b30b7 100644
--- a/ingestify/tests/test_engine.py
+++ b/ingestify/tests/test_engine.py
@@ -10,6 +10,7 @@
     DataSpecVersionCollection,
     DraftFile,
     Dataset,
+    DatasetState,
     DatasetCreated,
 )
 from ingestify.domain.models.dataset.collection_metadata import (
@@ -435,3 +436,66 @@ def test_dev_engine():
     datasets = engine.store.get_dataset_collection()
     assert len(datasets) == 1
     assert datasets.first().name == "Test Dataset"
+
+
+def post_load_hook(dataset_resource: DatasetResource, files: dict[str, DraftFile]):
+    # Change state to COMPLETE if file content is not '{}'
+    for file in files.values():
+        if file.size > 2:
+            dataset_resource.state = DatasetState.COMPLETE
+            break
+
+
+def file_loader_with_hook(file_resource, current_file):
+    # First run: empty JSON, second run: actual data
+    content = "{}" if not current_file else '{"data": "value"}'
+    return DraftFile.from_input(content, data_feed_key="file1")
+
+
+class SourceWithHook(Source):
+    provider = "test"
+
+    def find_datasets(
+        self,
+        dataset_type: str,
+        data_spec_versions: DataSpecVersionCollection,
+        dataset_collection_metadata,
+        competition_id,
+        season_id,
+        **kwargs,
+    ):
+        last_modified = datetime.now(pytz.utc)
+
+        yield (
+            DatasetResource(
+                dataset_resource_id=dict(
+                    competition_id=competition_id, season_id=season_id, match_id=1
+                ),
+                provider="test",
+                dataset_type="match",
+                name="Test Dataset",
+                state=DatasetState.SCHEDULED,
+                post_load_files=post_load_hook,
+            ).add_file(
+                last_modified=last_modified,
+                data_feed_key="file1",
+                data_spec_version="v1",
+                file_loader=file_loader_with_hook,
+            )
+        )
+
+
+def test_post_load_files_hook(config_file):
+    """Test that post_load_files hook changes state from SCHEDULED to COMPLETE when content is not empty."""
+    engine = get_engine(config_file, "main")
+    add_ingestion_plan(engine, SourceWithHook("test"), competition_id=1, season_id=2)
+
+    # First run: file contains '{}', state should remain SCHEDULED
+    engine.load()
+    dataset1 = engine.store.get_dataset_collection().first()
+    assert dataset1.state == DatasetState.SCHEDULED
+
+    # Second run: file contains actual data, state should change to COMPLETE
+    engine.load()
+    dataset2 = engine.store.get_dataset_collection().first()
+    assert dataset2.state == DatasetState.COMPLETE