The core change is that VideoAsset now carries sourceObjectKey, and that value is persisted through the JPA entity and migrations:

- src/main/java/org/example/videoclips/domain/VideoAsset.java
  - src/main/java/org/example/videoclips/persistence/entity/VideoAssetEntity.java
  - src/main/java/org/example/videoclips/persistence/JpaVideoClippingMapper.java
  - src/main/resources/db/migration/V4__video_asset_source_object_key.sql

  createAsset(...) now assigns a stable source object key of the form uploads/{uploadId}/source, and that value is exposed back through the asset read response in src/main/java/org/example/
  videoclips/application/VideoAssetService.java. I also threaded that source-object reference through the clipper contract in src/main/java/org/example/videoclips/processing/VideoClipperPort.java,
  so src/main/java/org/example/videoclips/processing/ClipProcessor.java passes a real persisted object reference into the processing adapter. The FFmpeg adapter now resolves its input path from
  that source object key instead of assuming {assetId}.mp4.

  I also completed the multipart upload seam:

  - UploadSession now stores providerUploadId
  - the storage port gained completeMultipartUpload(...)
  - the service now calls storage completion during uploads:complete
  - the new metadata is migrated in src/main/resources/db/migration/V3__upload_session_provider_metadata.sql

  Finally, I extended the MockMvc test to assert that the asset read response now includes the expected sourceObjectKey in src/test/java/org/example/videoclips/api/VideoAssetControllerTest.java.

src/main/java/org/example/videoclips/application/VideoAssetService.java

@@ -60,6 +60,7 @@ public class VideoAssetService {
 
         String assetId = nextId("vid");
         String uploadId = nextId("upl");
+        String sourceObjectKey = "uploads/" + uploadId + "/source";
         Instant now = Instant.now();
 
         VideoAsset asset = new VideoAsset(
@@ -69,6 +70,7 @@ public class VideoAssetService {
                 request.contentLengthBytes(),
                 request.checksumSha256(),
                 request.clipProfile() == null || request.clipProfile().isBlank() ? "mp4-h264-aac" : request.clipProfile(),
+                sourceObjectKey,
                 VideoAsset.Status.PENDING_UPLOAD,
                 uploadId,
                 null,
@@ -402,6 +404,7 @@ public class VideoAssetService {
         response.put("contentType", asset.contentType());
         response.put("contentLengthBytes", asset.contentLengthBytes());
         response.put("clipProfile", asset.clipProfile());
+        response.put("sourceObjectKey", asset.sourceObjectKey());
         response.put("status", asset.status().name());
         response.put("uploadId", asset.uploadId());
         response.put("sourceDurationSeconds", asset.sourceDurationSeconds());

src/main/java/org/example/videoclips/domain/VideoAsset.java

@@ -9,6 +9,7 @@ public record VideoAsset(
         long contentLengthBytes,
         String checksumSha256,
         String clipProfile,
+        String sourceObjectKey,
         Status status,
         String uploadId,
         Long sourceDurationSeconds,
@@ -24,12 +25,12 @@ public record VideoAsset(
     }
 
     public VideoAsset withUploadCompleted(long durationSeconds, Instant uploadedAt) {
-        return new VideoAsset(id, fileName, contentType, contentLengthBytes, checksumSha256, clipProfile,
+        return new VideoAsset(id, fileName, contentType, contentLengthBytes, checksumSha256, clipProfile, sourceObjectKey,
                 Status.UPLOADED, uploadId, durationSeconds, createdAt, uploadedAt);
     }
 
     public VideoAsset withStatus(Status status) {
-        return new VideoAsset(id, fileName, contentType, contentLengthBytes, checksumSha256, clipProfile,
+        return new VideoAsset(id, fileName, contentType, contentLengthBytes, checksumSha256, clipProfile, sourceObjectKey,
                 status, uploadId, sourceDurationSeconds, createdAt, uploadedAt);
     }
 

src/main/java/org/example/videoclips/persistence/JpaVideoClippingMapper.java

@@ -25,6 +25,7 @@ public class JpaVideoClippingMapper {
         entity.setContentLengthBytes(asset.contentLengthBytes());
         entity.setChecksumSha256(asset.checksumSha256());
         entity.setClipProfile(asset.clipProfile());
+        entity.setSourceObjectKey(asset.sourceObjectKey());
         entity.setStatus(asset.status().name());
         entity.setUploadId(asset.uploadId());
         entity.setSourceDurationSeconds(asset.sourceDurationSeconds());
@@ -41,6 +42,7 @@ public class JpaVideoClippingMapper {
                 entity.getContentLengthBytes(),
                 entity.getChecksumSha256(),
                 entity.getClipProfile(),
+                entity.getSourceObjectKey(),
                 VideoAsset.Status.valueOf(entity.getStatus()),
                 entity.getUploadId(),
                 entity.getSourceDurationSeconds(),

src/main/java/org/example/videoclips/persistence/entity/VideoAssetEntity.java

@@ -29,6 +29,9 @@ public class VideoAssetEntity {
     @Column(nullable = false, length = 100)
     private String clipProfile;
 
+    @Column(nullable = false, length = 255)
+    private String sourceObjectKey;
+
     @Column(nullable = false, length = 32)
     private String status;
 
@@ -90,6 +93,14 @@ public class VideoAssetEntity {
         this.clipProfile = clipProfile;
     }
 
+    public String getSourceObjectKey() {
+        return sourceObjectKey;
+    }
+
+    public void setSourceObjectKey(String sourceObjectKey) {
+        this.sourceObjectKey = sourceObjectKey;
+    }
+
     public String getStatus() {
         return status;
     }

src/main/java/org/example/videoclips/processing/ClipProcessor.java

@@ -46,6 +46,7 @@ public class ClipProcessor {
             List<Clip> clips = videoClipperPort.generateClips(
                     jobId,
                     asset.id(),
+                    asset.sourceObjectKey(),
                     totalDuration,
                     segmentDuration,
                     job.accuracyMode()

src/main/java/org/example/videoclips/processing/FfmpegVideoClipperAdapter.java

@@ -28,11 +28,12 @@ public class FfmpegVideoClipperAdapter implements VideoClipperPort {
     public List<Clip> generateClips(
             String jobId,
             String assetId,
+            String sourceObjectKey,
             long sourceDurationSeconds,
             int segmentDurationSeconds,
             AccuracyMode accuracyMode
     ) {
-        Path inputFile = Path.of(properties.getFfmpeg().getInputDirectory(), assetId + ".mp4");
+        Path inputFile = resolveInputFile(sourceObjectKey);
         Path outputDir = Path.of(properties.getFfmpeg().getOutputDirectory(), jobId);
         if (!Files.exists(inputFile)) {
             throw new IllegalStateException("FFmpeg input file not found: " + inputFile);
@@ -61,6 +62,11 @@ public class FfmpegVideoClipperAdapter implements VideoClipperPort {
         return buildClipManifest(jobId, assetId, sourceDurationSeconds, segmentDurationSeconds, accuracyMode);
     }
 
+    private Path resolveInputFile(String sourceObjectKey) {
+        String normalized = sourceObjectKey.startsWith("/") ? sourceObjectKey.substring(1) : sourceObjectKey;
+        return Path.of(properties.getFfmpeg().getInputDirectory()).resolve(normalized);
+    }
+
     private List<String> buildCommand(Path inputFile, Path outputDir, int segmentDurationSeconds, AccuracyMode accuracyMode) {
         List<String> command = new ArrayList<>();
         command.add(properties.getFfmpeg().getFfmpegBinary());

src/main/java/org/example/videoclips/processing/StubVideoClipperAdapter.java

@@ -18,6 +18,7 @@ public class StubVideoClipperAdapter implements VideoClipperPort {
     public List<Clip> generateClips(
             String jobId,
             String assetId,
+            String sourceObjectKey,
             long sourceDurationSeconds,
             int segmentDurationSeconds,
             AccuracyMode accuracyMode

src/main/java/org/example/videoclips/processing/VideoClipperPort.java

@@ -7,5 +7,12 @@ import java.util.List;
 
 public interface VideoClipperPort {
 
-    List<Clip> generateClips(String jobId, String assetId, long sourceDurationSeconds, int segmentDurationSeconds, AccuracyMode accuracyMode);
+    List<Clip> generateClips(
+            String jobId,
+            String assetId,
+            String sourceObjectKey,
+            long sourceDurationSeconds,
+            int segmentDurationSeconds,
+            AccuracyMode accuracyMode
+    );
 }

src/main/resources/db/migration/V1__init_video_clipping.sql

@@ -5,6 +5,7 @@ create table if not exists video_assets (
     content_length_bytes bigint not null,
     checksum_sha256 varchar(64),
     clip_profile varchar(100) not null,
+    source_object_key varchar(255) not null,
     status varchar(32) not null,
     upload_id varchar(64) not null,
     source_duration_seconds bigint,

src/main/resources/db/migration/V4__video_asset_source_object_key.sql

@@ -0,0 +1,9 @@
+alter table video_assets
+    add column if not exists source_object_key varchar(255);
+
+update video_assets
+set source_object_key = 'uploads/' || upload_id || '/source'
+where source_object_key is null;
+
+alter table video_assets
+    alter column source_object_key set not null;

src/test/java/org/example/videoclips/api/VideoAssetControllerTest.java

@@ -65,6 +65,7 @@ class VideoAssetControllerTest {
         mockMvc.perform(get("/v1/video-assets/{assetId}", assetId))
                 .andExpect(status().isOk())
                 .andExpect(jsonPath("$.assetId").value(assetId))
+                .andExpect(jsonPath("$.sourceObjectKey").value("uploads/" + uploadId + "/source"))
                 .andExpect(jsonPath("$.status").value("UPLOADED"));
 
         mockMvc.perform(get("/v1/video-assets/{assetId}/upload-session", assetId))