feat(provenance): ML stops surfacing the artist category

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

backend/app/services/ml/centroids.py

@@ -23,7 +23,6 @@ from .embedder import MODEL_VERSION as SIGLIP_VERSION
 
 ELIGIBLE_KINDS = {
     TagKind.character,
-    TagKind.artist,
     TagKind.fandom,
     TagKind.general,
     TagKind.series,

backend/app/services/ml/suggestions.py

@@ -48,12 +48,13 @@ class SuggestionService:
         ).scalar_one()
 
     def _threshold_for(self, s: MLSettings, category: str) -> float:
+        # 'artist' intentionally absent (FC-2d-vii-c) — falls through to
+        # the 1.01 "never surfaces" default like any unsurfaced category.
         return {
-            "artist": s.suggestion_threshold_artist,
             "character": s.suggestion_threshold_character,
             "copyright": s.suggestion_threshold_copyright,
             "general": s.suggestion_threshold_general,
-        }.get(category, 1.01)  # 1.01 => never surfaces (unsurfaced category)
+        }.get(category, 1.01)
 
     async def for_image(self, image_id: int) -> SuggestionList:
         img = await self.session.get(ImageRecord, image_id)

backend/app/services/ml/tagger.py

@@ -34,7 +34,10 @@ STORE_FLOOR = float(os.environ.get("TAGGER_STORE_FLOOR", "0.05"))
 
 # The categories FC-2b surfaces in the UI. Others (meta/rating/year) are
 # still stored but the suggestion service filters them out.
-SURFACED_CATEGORIES = {"artist", "character", "copyright", "general"}
+# FC-2d-vii-c: 'artist' retired — artist identity is acquisition-derived
+# (image_record.artist_id), never ML-inferred. Raw predictions are still
+# stored at STORE_FLOOR but artist never surfaces.
+SURFACED_CATEGORIES = {"character", "copyright", "general"}
 
 
 @dataclass(frozen=True)

tests/test_ml_artist_retired.py

@@ -0,0 +1,27 @@
+import pytest
+
+pytestmark = pytest.mark.integration
+
+
+def test_artist_not_surfaced():
+    from backend.app.services.ml.tagger import SURFACED_CATEGORIES
+    assert "artist" not in SURFACED_CATEGORIES
+
+
+def test_artist_not_centroid_eligible():
+    from backend.app.models import TagKind
+    from backend.app.services.ml.centroids import ELIGIBLE_KINDS
+    assert TagKind.artist not in ELIGIBLE_KINDS
+
+
+def test_threshold_for_artist_is_unsurfaced():
+    from backend.app.services.ml.suggestions import SuggestionService
+
+    class _S:
+        suggestion_threshold_character = 0.5
+        suggestion_threshold_copyright = 0.5
+        suggestion_threshold_general = 0.5
+
+    svc = SuggestionService.__new__(SuggestionService)
+    # 'artist' must fall through to the 1.01 "never surfaces" default
+    assert svc._threshold_for(_S(), "artist") == 1.01