fix(importer): Source = one per (artist, platform), not one per post — filesystem importer's sidecar paths now reuse the artist's existing subscription Source (or create one synthetic anchor with enabled=False) instead of fabricating a new Source per post URL. Alembic 0022 consolidates existing per-post Sources to canonical (prefers campaign URL; falls back to sidecar:<platform>:<slug>) and re-parents Posts + ImageProvenance, merging Post collisions.

Operator-flagged 2026-05-26: Atole artist detail page showed 406 Sources where 1 was right.

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

backend/app/services/importer.py

@@ -247,6 +247,62 @@ class Importer:
                 )
             ).scalar_one()
 
+    def _source_for_sidecar(
+        self, *, artist_id: int, platform: str, artist_slug: str,
+    ) -> Source:
+        """Filesystem-import sidecar Source resolver.
+
+        Source represents a subscription feed (one per artist+platform — the
+        gallery-dl URL polled by the FC-3 downloader). The filesystem importer
+        used to call _find_or_create_source(url=sd.post_url), which created
+        one Source row per post URL — 100s of junk Sources per artist, all
+        with enabled=True, polluting the artist detail page and tricking the
+        subscription checker into trying to poll patreon post URLs as feeds.
+        Operator-flagged 2026-05-26.
+
+        New behaviour: if any Source row exists for (artist_id, platform),
+        reuse it regardless of its URL — the artist's real subscription Source
+        (created by the downloader / extension / UI) is the canonical
+        attachment point for filesystem-imported posts. If none exists, create
+        ONE synthetic anchor with url='sidecar:<platform>:<artist_slug>' and
+        enabled=False (so the subscription checker doesn't poll it).
+        """
+        existing = self.session.execute(
+            select(Source)
+            .where(
+                Source.artist_id == artist_id,
+                Source.platform == platform,
+            )
+            .order_by(Source.id.asc())
+            .limit(1)
+        ).scalar_one_or_none()
+        if existing is not None:
+            return existing
+        synthetic_url = f"sidecar:{platform}:{artist_slug}"
+        sp = self.session.begin_nested()
+        try:
+            row = Source(
+                artist_id=artist_id,
+                platform=platform,
+                url=synthetic_url,
+                enabled=False,
+            )
+            self.session.add(row)
+            self.session.flush()
+            sp.commit()
+            return row
+        except IntegrityError:
+            sp.rollback()
+            return self.session.execute(
+                select(Source)
+                .where(
+                    Source.artist_id == artist_id,
+                    Source.platform == platform,
+                )
+                .order_by(Source.id.asc())
+                .limit(1)
+            ).scalar_one()
+
     def _find_or_create_post(
         self, *, source_id: int, external_post_id: str,
     ) -> Post:
@@ -315,9 +371,8 @@ class Importer:
             return None
         sd = parse_sidecar(data)
         platform = sd.platform or "unknown"
-        url = sd.post_url or f"sidecar:{platform}"
-        src = self._find_or_create_source(
-            artist_id=artist.id, platform=platform, url=url,
+        src = self._source_for_sidecar(
+            artist_id=artist.id, platform=platform, artist_slug=artist.slug,
         )
         epid = sd.external_post_id or sc.stem
         return self._find_or_create_post(
@@ -763,9 +818,9 @@ class Importer:
             src = explicit_source
         else:
             platform = sd.platform or "unknown"
-            url = sd.post_url or f"sidecar:{platform}"
-            src = self._find_or_create_source(
-                artist_id=artist.id, platform=platform, url=url,
+            src = self._source_for_sidecar(
+                artist_id=artist.id, platform=platform,
+                artist_slug=artist.slug,
             )
 
         epid = sd.external_post_id or sc.stem