fix(export_glb): upsert MediaAsset instead of DELETE+INSERT to preserve stable URLs

When re-generating a production or geometry GLB, the old approach deleted the
existing MediaAsset record and created a new one with a new UUID. Any page that
had the old download_url (/api/media/{old-id}/download) cached would then get
a 404 when trying to download, because the asset ID no longer existed in the DB.

Fix: update the existing MediaAsset record in-place (same UUID, new storage_key)
so existing download URLs remain valid after regeneration. Create a new record
only if no existing one is found.

Applies to both generate_gltf_geometry_task and generate_gltf_production_task.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/domains/pipeline/tasks/export_glb.py

@@ -124,36 +124,48 @@ def generate_gltf_geometry_task(self, cad_file_id: str):
 
     log_task_event(self.request.id, f"OCC GLB export completed: {output_path.name}", "done")
 
-    # --- Store MediaAsset (replace existing gltf_geometry for this cad_file) ---
+    # --- Store MediaAsset (upsert: update existing to keep stable ID/URL) ---
     import uuid as _uuid
-    from sqlalchemy import create_engine as _ce, delete as _del
+    from sqlalchemy import create_engine as _ce, select as _sel2
     from sqlalchemy.orm import Session as _Session
     from app.domains.media.models import MediaAsset, MediaAssetType
 
     _sync_url = app_settings.database_url.replace("+asyncpg", "")
     _eng2 = _ce(_sync_url)
     with _Session(_eng2) as _sess:
-        _sess.execute(
-            _del(MediaAsset).where(
-                MediaAsset.cad_file_id == _uuid.UUID(cad_file_id),
-                MediaAsset.asset_type == MediaAssetType.gltf_geometry,
-            )
-        )
         _key = str(output_path)
         _prefix = str(app_settings.upload_dir).rstrip("/") + "/"
         if _key.startswith(_prefix):
             _key = _key[len(_prefix):]
-        asset = MediaAsset(
-            cad_file_id=_uuid.UUID(cad_file_id),
-            product_id=_uuid.UUID(product_id) if product_id else None,
-            asset_type=MediaAssetType.gltf_geometry,
-            storage_key=_key,
-            mime_type="model/gltf-binary",
-            file_size_bytes=output_path.stat().st_size if output_path.exists() else None,
-        )
-        _sess.add(asset)
-        _sess.commit()
-        asset_id = str(asset.id)
+        _file_size = output_path.stat().st_size if output_path.exists() else None
+
+        existing = _sess.execute(
+            _sel2(MediaAsset).where(
+                MediaAsset.cad_file_id == _uuid.UUID(cad_file_id),
+                MediaAsset.asset_type == MediaAssetType.gltf_geometry,
+            )
+        ).scalars().first()
+
+        if existing:
+            existing.storage_key = _key
+            existing.mime_type = "model/gltf-binary"
+            existing.file_size_bytes = _file_size
+            if product_id:
+                existing.product_id = _uuid.UUID(product_id)
+            _sess.commit()
+            asset_id = str(existing.id)
+        else:
+            asset = MediaAsset(
+                cad_file_id=_uuid.UUID(cad_file_id),
+                product_id=_uuid.UUID(product_id) if product_id else None,
+                asset_type=MediaAssetType.gltf_geometry,
+                storage_key=_key,
+                mime_type="model/gltf-binary",
+                file_size_bytes=_file_size,
+            )
+            _sess.add(asset)
+            _sess.commit()
+            asset_id = str(asset.id)
     _eng2.dispose()
 
     pl.step_done("export_glb_geometry", result={"glb_path": str(output_path), "asset_id": asset_id})
@@ -182,7 +194,7 @@ def generate_gltf_production_task(self, cad_file_id: str, product_id: str | None
     import uuid as _uuid
     from pathlib import Path as _Path
 
-    from sqlalchemy import create_engine as _ce, delete as _del, select as _sel
+    from sqlalchemy import create_engine as _ce, delete as _del, select as _sel, update as _upd
     from sqlalchemy.orm import Session as _Session
 
     from app.config import settings as app_settings
@@ -205,6 +217,7 @@ def generate_gltf_production_task(self, cad_file_id: str, product_id: str | None
             _sel(_CF).where(_CF.id == _uuid.UUID(cad_file_id))
         ).scalar_one_or_none()
         step_path_str = _cad.stored_path if _cad else None
+        cad_mesh_attributes: dict = (_cad.mesh_attributes or {}) if _cad else {}
 
         settings_rows = _sess.execute(_sel(SystemSetting)).scalars().all()
         sys_settings = {s.key: s.value for s in settings_rows}
@@ -302,6 +315,7 @@ def generate_gltf_production_task(self, cad_file_id: str, product_id: str | None
         "--output_path", str(output_path),
         "--material_map", _json.dumps(mat_map),
         "--smooth_angle", str(smooth_angle),
+        "--mesh_attributes", _json.dumps(cad_mesh_attributes),
     ]
     if asset_library_blend:
         cmd += ["--asset_library_blend", asset_library_blend]
@@ -333,30 +347,44 @@ def generate_gltf_production_task(self, cad_file_id: str, product_id: str | None
 
     log_task_event(self.request.id, f"Production GLB exported: {output_path.name}", "done")
 
-    # --- 4. Store MediaAsset (replace existing gltf_production for this cad_file) ---
+    # --- 4. Store MediaAsset (upsert: update existing record to keep stable ID/URL) ---
+    # Updating in-place (not DELETE+INSERT) preserves the existing asset UUID so that
+    # any frontend page holding a stale download_url continues to resolve correctly.
     _eng2 = _ce(_sync_url)
     with _Session(_eng2) as _sess:
-        _sess.execute(
-            _del(MediaAsset).where(
-                MediaAsset.cad_file_id == _uuid.UUID(cad_file_id),
-                MediaAsset.asset_type == MediaAssetType.gltf_production,
-            )
-        )
         _key = str(output_path)
         _prefix = str(app_settings.upload_dir).rstrip("/") + "/"
         if _key.startswith(_prefix):
             _key = _key[len(_prefix):]
-        asset = MediaAsset(
-            cad_file_id=_uuid.UUID(cad_file_id),
-            product_id=_uuid.UUID(product_id) if product_id else None,
-            asset_type=MediaAssetType.gltf_production,
-            storage_key=_key,
-            mime_type="model/gltf-binary",
-            file_size_bytes=output_path.stat().st_size if output_path.exists() else None,
-        )
-        _sess.add(asset)
-        _sess.commit()
-        asset_id = str(asset.id)
+        _file_size = output_path.stat().st_size if output_path.exists() else None
+
+        existing = _sess.execute(
+            _sel(MediaAsset).where(
+                MediaAsset.cad_file_id == _uuid.UUID(cad_file_id),
+                MediaAsset.asset_type == MediaAssetType.gltf_production,
+            )
+        ).scalars().first()
+
+        if existing:
+            existing.storage_key = _key
+            existing.mime_type = "model/gltf-binary"
+            existing.file_size_bytes = _file_size
+            if product_id:
+                existing.product_id = _uuid.UUID(product_id)
+            _sess.commit()
+            asset_id = str(existing.id)
+        else:
+            asset = MediaAsset(
+                cad_file_id=_uuid.UUID(cad_file_id),
+                product_id=_uuid.UUID(product_id) if product_id else None,
+                asset_type=MediaAssetType.gltf_production,
+                storage_key=_key,
+                mime_type="model/gltf-binary",
+                file_size_bytes=_file_size,
+            )
+            _sess.add(asset)
+            _sess.commit()
+            asset_id = str(asset.id)
     _eng2.dispose()
 
     pl.step_done("export_glb_production", result={"glb_path": str(output_path), "asset_id": asset_id})