fix(lab): stream synchronized replay fragments

tests/test_session_api.py

@@ -194,10 +194,7 @@ async def render_file_response(
         return {
             "status": response.status_code,
             "headers": response.raw_headers,
-        }, b"".join(
-            chunk.encode("utf-8") if isinstance(chunk, str) else chunk
-            for chunk in chunks
-        )
+        }, b"".join(chunk.encode("utf-8") if isinstance(chunk, str) else chunk for chunk in chunks)
     sent: list[dict[str, Any]] = []
     request_delivered = False
 
@@ -318,9 +315,7 @@ def test_session_router_exposes_immutable_lab_provenance(tmp_path: Path) -> None
 
     assert item["lab"] == binding.as_dict()
     assert [value["id"] for value in source_listing["items"]] == [source.name]
-    assert [value["id"] for value in laboratory_listing["items"]] == [
-        binding.session_id
-    ]
+    assert [value["id"] for value in laboratory_listing["items"]] == [binding.session_id]
     assert detail["lab"] == binding.as_dict()
     assert item["lab"]["source_session_id"] == source.name
     assert item["lab"]["provenance"]["source_payloads_mutated"] is False
@@ -1350,9 +1345,7 @@ def test_recorded_perception_endpoint_returns_one_complete_optional_overlay(
     assert response.body == b"RRF2perception"
     assert response.media_type == "application/vnd.rerun.rrd"
     assert response.headers["content-length"] == str(len(response.body))
-    assert calls == [
-        (session.name, "nodedc_mission_core_recorded", "recording-001")
-    ]
+    assert calls == [(session.name, "nodedc_mission_core_recorded", "recording-001")]
     status_route = endpoint(
         router,
         "/api/v1/observation-sessions/{session_id}/perception/status",
@@ -1699,8 +1692,7 @@ def test_session_router_exposes_opaque_recorded_media_manifest_and_ranges(
         render_file_response(stream_response, range_header=None)
     )
     stream_headers = {
-        key.decode("latin-1"): value.decode("latin-1")
-        for key, value in stream_start["headers"]
+        key.decode("latin-1"): value.decode("latin-1") for key, value in stream_start["headers"]
     }
     assert stream_start["status"] == 206
     assert stream_body == init[-2:] + segment[:4]
@@ -1736,6 +1728,19 @@ def test_session_router_exposes_opaque_recorded_media_manifest_and_ranges(
     assert init_start["status"] == 206
     assert init_body == init[4:8]
 
+    generation_bound_init = init_route(
+        session_id=session.name,
+        artifact_id=artifact_id,
+        epoch_ordinal=1,
+        generation=generation,
+        range_header="bytes=0-3",
+    )
+    generation_init_start, generation_init_body = asyncio.run(
+        render_file_response(generation_bound_init, range_header=b"bytes=0-3")
+    )
+    assert generation_init_start["status"] == 206
+    assert generation_init_body == init[:4]
+
     with pytest.raises(HTTPException) as stale_segment_generation:
         segment_route(
             session_id=session.name,
@@ -1768,6 +1773,31 @@ def test_session_router_exposes_opaque_recorded_media_manifest_and_ranges(
     assert headers["content-length"] == "6"
     assert headers["x-content-type-options"] == "nosniff"
 
+    generation_bound_segment = segment_route(
+        session_id=session.name,
+        artifact_id=artifact_id,
+        epoch_ordinal=1,
+        segment_sequence=1,
+        generation=generation,
+        range_header="bytes=0-3",
+    )
+    generation_segment_start, generation_segment_body = asyncio.run(
+        render_file_response(generation_bound_segment, range_header=b"bytes=0-3")
+    )
+    assert generation_segment_start["status"] == 206
+    assert generation_segment_body == segment[:4]
+
+    with pytest.raises(HTTPException) as stale_fragment_generation:
+        segment_route(
+            session_id=session.name,
+            artifact_id=artifact_id,
+            epoch_ordinal=1,
+            segment_sequence=1,
+            generation="0" * 64,
+            range_header=None,
+        )
+    assert stale_fragment_generation.value.status_code == 412
+
     original_segment = writer.segments_dir / "1.m4s"
     outside = tmp_path / "outside.m4s"
     outside.write_bytes(segment)
@@ -1859,14 +1889,12 @@ def test_replay_exposes_generation_bound_perception_video_with_native_ranges(
     )
     manifest_route = endpoint(
         router,
-        "/api/v1/observation-sessions/{session_id}/perception-media/"
-        "{result_id}/manifest",
+        "/api/v1/observation-sessions/{session_id}/perception-media/{result_id}/manifest",
         "GET",
     )
     stream_route = endpoint(
         router,
-        "/api/v1/observation-sessions/{session_id}/perception-media/"
-        "{result_id}/recording.mp4",
+        "/api/v1/observation-sessions/{session_id}/perception-media/{result_id}/recording.mp4",
         "GET",
     )
 
@@ -1929,9 +1957,7 @@ def test_replay_exposes_generation_bound_perception_video_with_native_ranges(
         range_header="bytes=7-14",
     )
     start, body = asyncio.run(render_file_response(response, range_header=b"bytes=7-14"))
-    headers = {
-        key.decode("latin-1"): value.decode("latin-1") for key, value in start["headers"]
-    }
+    headers = {key.decode("latin-1"): value.decode("latin-1") for key, value in start["headers"]}
     assert start["status"] == 206
     assert body == video_payload[7:15]
     assert headers["content-range"] == f"bytes 7-14/{len(video_payload)}"