fix(audit-g5): centroid version DB-as-truth + modal as overlay

Closes the last two findings from the 2026-06-02 audit (G5.1 + G5.4).

G5.1 — Centroid version no longer drifts:

CentroidService now reads MLSettings.embedder_model_version (the DB
row tag_and_embed already writes from) for both the centroid model-
version stamp and the drift-detection comparison. Previously the
centroid sites imported MODEL_VERSION from env, so the version stamped
on centroids could disagree with the version stamped on the embeddings
they were built from. By construction those now match, so list_drifted
won't silently miss the env-vs-DB drift case.

embedder.py keeps MODEL_VERSION as an env-driven constant for the
actual model loader — that's a different concern (which weights are
loaded) from the version-stamp that gets persisted alongside data.

G5.4 — Modal is a Pinia-only overlay:

The previous URL↔modal sync in GalleryView and ArtistGalleryTab
leaked the modal across route changes (RouterLink to /artist/<slug>
left the modal mounted on top of the new route) and re-opened it
on history back/forward with stale ?image=N entries.

Now: openImage() just calls modal.open(id) — no URL push.
GalleryView's dead closeImage helper is deleted. A route.name
watcher in App.vue closes the modal whenever the route changes,
which auto-fixes RouterLink-in-modal and back/forward.

Backward-compat: ?image=N is still honored on initial mount as a
one-shot deep-link opener, then router.replace strips the query so
the URL doesn't re-trigger and no extra history entry is added.
Existing bookmarks / shared URLs keep working; new opens stay
Pinia-only.

backend/app/services/ml/centroids.py

@@ -19,7 +19,6 @@ from ...models import (
     TagReferenceEmbedding,
 )
 from ...models.tag import image_tag
-from .embedder import MODEL_VERSION as SIGLIP_VERSION
 
 ELIGIBLE_KINDS = {
     TagKind.character,
@@ -46,6 +45,21 @@ class CentroidService:
             )
         ).scalar_one()
 
+    async def _model_version(self) -> str:
+        """Audit 2026-06-02: SigLIP model-version stamp comes from the
+        DB row, not the env constant. tag_and_embed (tasks/ml.py:110)
+        already reads from MLSettings.embedder_model_version, so by
+        sourcing centroid stamps + drift checks from the same row, we
+        eliminate the silent-drift case the audit flagged. env
+        SIGLIP_MODEL_VERSION still drives which model embedder.py
+        loads at runtime; the version stamp is purely the operator-
+        controlled identifier."""
+        return (
+            await self.session.execute(
+                select(MLSettings.embedder_model_version).where(MLSettings.id == 1)
+            )
+        ).scalar_one()
+
     async def recompute_for_tag(self, tag_id: int) -> bool:
         """Recompute one tag's centroid. Returns True if a centroid was
         written, False if skipped (ineligible kind or too few members)."""
@@ -69,19 +83,20 @@ class CentroidService:
             return False
 
         centroid = np.mean(np.stack(embeddings), axis=0).astype(np.float32)
+        model_version = await self._model_version()
 
         stmt = insert(TagReferenceEmbedding).values(
             tag_id=tag_id,
             embedding=centroid.tolist(),
             reference_count=len(embeddings),
-            model_version=SIGLIP_VERSION,
+            model_version=model_version,
         )
         stmt = stmt.on_conflict_do_update(
             index_elements=["tag_id"],
             set_={
                 "embedding": centroid.tolist(),
                 "reference_count": len(embeddings),
-                "model_version": SIGLIP_VERSION,
+                "model_version": model_version,
                 "updated_at": func.now(),
             },
         )
@@ -92,6 +107,7 @@ class CentroidService:
         """Tag ids whose centroid is stale: member count != reference_count,
         OR no centroid row, OR centroid built on a different SigLIP version.
         Only considers eligible-kind tags with embeddings present."""
+        current_model_version = await self._model_version()
         member_counts = (
             select(
                 image_tag.c.tag_id.label("tag_id"),
@@ -116,7 +132,7 @@ class CentroidService:
                     TagReferenceEmbedding.reference_count
                     != member_counts.c.members
                 )
-                | (TagReferenceEmbedding.model_version != SIGLIP_VERSION)
+                | (TagReferenceEmbedding.model_version != current_model_version)
             )
         )
         return list((await self.session.execute(stmt)).scalars().all())

frontend/src/App.vue

@@ -9,7 +9,9 @@
 </template>
 
 <script setup>
-import { onMounted, ref } from 'vue'
+import { onMounted, ref, watch } from 'vue'
+import { useRoute } from 'vue-router'
+
 import AppShell from './components/AppShell.vue'
 import AppSnackbar from './components/AppSnackbar.vue'
 import ImageViewer from './components/modal/ImageViewer.vue'
@@ -17,9 +19,20 @@ import { useModalStore } from './stores/modal.js'
 
 const modal = useModalStore()
 const snackbar = ref(null)
+const route = useRoute()
 
 onMounted(() => {
   // Expose snackbar via a simple global so stores can call it without props.
   window.__fcToast = (opts) => snackbar.value?.open(opts)
 })
+
+// Audit 2026-06-02: the modal is an overlay, not a page. When the
+// route changes (RouterLink inside the modal, history back/forward,
+// programmatic push from any view), close the modal so it doesn't
+// hover over a different route. Watching route.name (not the path)
+// keeps within-route nav like /artist/foo → /artist/bar from
+// dismissing the modal mid-browse.
+watch(() => route.name, () => {
+  if (modal.isOpen) modal.close()
+})
 </script>

frontend/src/components/artist/ArtistGalleryTab.vue

@@ -11,7 +11,7 @@
 </template>
 
 <script setup>
-import { onMounted, watch } from 'vue'
+import { onMounted } from 'vue'
 import { useRoute, useRouter } from 'vue-router'
 
 import { useArtistStore } from '../../stores/artist.js'
@@ -28,18 +28,20 @@ const route = useRoute()
 const router = useRouter()
 
 onMounted(() => {
+  // Audit 2026-06-02: same overlay treatment as GalleryView —
+  // honor `?image=N` once for backward-compat, then strip the
+  // query and let the modal live in Pinia-only state.
   const initial = parseInt(route.query.image, 10)
-  if (!isNaN(initial)) modal.open(initial)
-})
-
-watch(() => route.query.image, (q) => {
-  const id = parseInt(q, 10)
-  if (!isNaN(id) && id !== modal.currentImageId) modal.open(id)
-  else if (isNaN(id) && modal.currentImageId !== null) modal.close()
+  if (!isNaN(initial)) {
+    modal.open(initial)
+    const q = { ...route.query }
+    delete q.image
+    router.replace({ query: q })
+  }
 })
 
 function openImage (id) {
-  router.push({ query: { ...route.query, image: id } })
+  modal.open(id)
 }
 </script>
 

frontend/src/views/GalleryView.vue

@@ -47,9 +47,20 @@ onMounted(async () => {
   else if (!isNaN(tagId)) store.setTagFilter(tagId)
   await store.loadInitial()
   await store.loadTimeline()
-  // Open modal if URL has ?image=N
+  // Audit 2026-06-02: modal is now a Pinia-only overlay (see
+  // G5.4 design). The previous URL↔modal sync leaked the modal
+  // across route changes and re-opened it on history back/forward.
+  // We still honor `?image=N` as a one-shot deep-link opener so
+  // existing bookmarks / shared URLs keep working; we strip the
+  // query immediately via router.replace so the URL doesn't
+  // re-trigger and no history entry is added.
   const initial = parseInt(route.query.image, 10)
-  if (!isNaN(initial)) modal.open(initial)
+  if (!isNaN(initial)) {
+    modal.open(initial)
+    const q = { ...route.query }
+    delete q.image
+    router.replace({ query: q })
+  }
 })
 
 watch(() => route.query.tag_id, (q) => {
@@ -64,19 +75,8 @@ watch(() => route.query.post_id, (q) => {
   store.setPostFilter(isNaN(postId) ? null : postId)
 })
 
-watch(() => route.query.image, (q) => {
-  const id = parseInt(q, 10)
-  if (!isNaN(id) && id !== modal.currentImageId) modal.open(id)
-  else if (isNaN(id) && modal.currentImageId !== null) modal.close()
-})
-
 function openImage(id) {
-  router.push({ query: { ...route.query, image: id } })
-}
-function closeImage() {
-  const q = { ...route.query }
-  delete q.image
-  router.push({ query: q })
+  modal.open(id)
 }
 </script>