feat(provenance): per-image artist on gallery scroll payload

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/app/api/gallery.py

@@ -43,6 +43,7 @@ async def scroll():
                     "height": i.height,
                     "created_at": i.created_at.isoformat(),
                     "thumbnail_url": i.thumbnail_url,
+                    "artist": i.artist,
                 }
                 for i in page.images
             ],

backend/app/services/gallery_service.py

@@ -13,7 +13,7 @@ from datetime import datetime
 from sqlalchemy import and_, exists, func, or_, select
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from ..models import ImageProvenance, ImageRecord, Source, Tag
+from ..models import Artist, ImageProvenance, ImageRecord, Post, Source, Tag
 from ..models.tag import image_tag
 
 CURSOR_SEPARATOR = "|"
@@ -43,6 +43,7 @@ class GalleryImage:
     height: int | None
     created_at: datetime
     thumbnail_url: str
+    artist: dict | None = None
 
 
 @dataclass(frozen=True)
@@ -92,6 +93,47 @@ def _provenance_clause(post_id, artist_id):
     return None
 
 
+async def _artists_for(session, image_ids: list[int]) -> dict[int, dict]:
+    """Map image_id -> {"name","slug"} using the primary-post path first,
+    then the lowest-id ImageProvenance row as fallback. Bounded by page
+    size (<= 200) → two indexed selects, no N+1."""
+    if not image_ids:
+        return {}
+    out: dict[int, dict] = {}
+
+    primary = (
+        select(ImageRecord.id, Artist.name, Artist.slug)
+        .join(Post, Post.id == ImageRecord.primary_post_id)
+        .join(Source, Source.id == Post.source_id)
+        .join(Artist, Artist.id == Source.artist_id)
+        .where(ImageRecord.id.in_(image_ids))
+    )
+    for img_id, name, slug in (await session.execute(primary)).all():
+        out[img_id] = {"name": name, "slug": slug}
+
+    remaining = [i for i in image_ids if i not in out]
+    if remaining:
+        fb = (
+            select(
+                ImageProvenance.image_record_id,
+                ImageProvenance.id,
+                Artist.name,
+                Artist.slug,
+            )
+            .join(Source, Source.id == ImageProvenance.source_id)
+            .join(Artist, Artist.id == Source.artist_id)
+            .where(ImageProvenance.image_record_id.in_(remaining))
+            .order_by(
+                ImageProvenance.image_record_id.asc(),
+                ImageProvenance.id.asc(),
+            )
+        )
+        for img_id, _pid, name, slug in (await session.execute(fb)).all():
+            if img_id not in out:  # first (lowest id) wins
+                out[img_id] = {"name": name, "slug": slug}
+    return out
+
+
 class GalleryService:
     def __init__(self, session: AsyncSession):
         self.session = session
@@ -135,6 +177,7 @@ class GalleryService:
             next_cursor = encode_cursor(last.created_at, last.id)
             rows = rows[:limit]
 
+        artists = await _artists_for(self.session, [r.id for r in rows])
         images = [
             GalleryImage(
                 id=r.id,
@@ -145,6 +188,7 @@ class GalleryService:
                 height=r.height,
                 created_at=r.created_at,
                 thumbnail_url=thumbnail_url(r.sha256, r.mime),
+                artist=artists.get(r.id),
             )
             for r in rows
         ]