diff --git a/backend/app/api/__init__.py b/backend/app/api/__init__.py
index a2d743b..4a88c1e 100644
--- a/backend/app/api/__init__.py
+++ b/backend/app/api/__init__.py
@@ -20,6 +20,7 @@ def all_blueprints() -> list[Blueprint]:
     from .artist import artist_bp
     from .artists import artists_bp
     from .attachments import attachments_bp
+    from .cleanup import cleanup_bp
     from .credentials import credentials_bp
     from .downloads import downloads_bp
     from .extension import extension_bp
@@ -50,6 +51,7 @@ def all_blueprints() -> list[Blueprint]:
         system_activity_bp,
         system_backup_bp,
         admin_bp,
+        cleanup_bp,
         import_admin_bp,
         migrate_bp,
         suggestions_bp,
diff --git a/backend/app/api/cleanup.py b/backend/app/api/cleanup.py
new file mode 100644
index 0000000..386c3e5
--- /dev/null
+++ b/backend/app/api/cleanup.py
@@ -0,0 +1,193 @@
+"""FC-Cleanup: /api/cleanup/* — retroactive enforcement of import filters.
+
+Endpoints:
+  POST /min-dimension/preview     synchronous SQL audit
+  POST /min-dimension/delete      synchronous SQL delete (Tier-C token)
+  POST /audit                      async transparency / single_color start
+  GET  /audit                      list recent audit_run rows
+  GET  /audit/<id>                 single audit_run row
+  POST /audit/<id>/apply           apply matched_ids deletes (Tier-C token)
+  POST /audit/<id>/cancel          flip running audit to cancelled
+
+Unused-tags retroactive prune intentionally NOT in this namespace —
+TagMaintenanceCard (Maintenance tab → moved to Cleanup tab in v26.05.25.7)
+uses the existing /api/admin/tags/prune-unused endpoint via the admin
+store. No duplicate route here.
+
+Confirm-token format matches modal/DestructiveConfirmModal.vue convention:
+  `delete-min-dim-<sha8(w,h)>` for min-dim delete
+  `delete-audit-<id>` for audit apply
+(Modal hardcodes action ∈ {'restore', 'delete'}; "apply audit" is semantically a delete of the matched images, so we use `delete-audit-<id>`.)
+"""
+
+from __future__ import annotations
+
+import hashlib
+from pathlib import Path
+
+from quart import Blueprint, jsonify, request
+from sqlalchemy import select
+
+from ..extensions import get_session
+from ..models import LibraryAuditRun
+from ..services import cleanup_service
+
+cleanup_bp = Blueprint("cleanup", __name__, url_prefix="/api/cleanup")
+
+IMAGES_ROOT = Path("/images")
+
+
+def _bad(error: str, *, status: int = 400, **extra):
+    body = {"error": error}
+    body.update(extra)
+    return jsonify(body), status
+
+
+def _min_dim_token(min_w: int, min_h: int) -> str:
+    # SHA-256 (not MD5) — Web Crypto's subtle.digest rejects MD5; both
+    # sides use SHA-256 truncated to 8 hex chars.
+    canon = f"{min_w}x{min_h}"
+    return f"delete-min-dim-{hashlib.sha256(canon.encode()).hexdigest()[:8]}"
+
+
+def _serialize_audit_run(audit: LibraryAuditRun) -> dict:
+    return {
+        "id": audit.id,
+        "rule": audit.rule,
+        "params": audit.params,
+        "status": audit.status,
+        "started_at": audit.started_at.isoformat() if audit.started_at else None,
+        "finished_at": audit.finished_at.isoformat() if audit.finished_at else None,
+        "scanned_count": audit.scanned_count,
+        "matched_count": audit.matched_count,
+        "matched_ids": audit.matched_ids,
+        "error": audit.error,
+    }
+
+
+@cleanup_bp.route("/min-dimension/preview", methods=["POST"])
+async def min_dim_preview():
+    body = await request.get_json(silent=True) or {}
+    try:
+        min_w = int(body.get("min_width", 0))
+        min_h = int(body.get("min_height", 0))
+    except (TypeError, ValueError):
+        return _bad("invalid_dimensions")
+    if min_w < 0 or min_h < 0:
+        return _bad("invalid_dimensions")
+    async with get_session() as session:
+        projection = await session.run_sync(
+            lambda s: cleanup_service.project_min_dimension_violations(
+                s, min_width=min_w, min_height=min_h,
+            )
+        )
+    return jsonify(projection)
+
+
+@cleanup_bp.route("/min-dimension/delete", methods=["POST"])
+async def min_dim_delete():
+    body = await request.get_json(silent=True) or {}
+    try:
+        min_w = int(body.get("min_width", 0))
+        min_h = int(body.get("min_height", 0))
+    except (TypeError, ValueError):
+        return _bad("invalid_dimensions")
+    if min_w < 0 or min_h < 0:
+        return _bad("invalid_dimensions")
+    supplied = body.get("confirm", "")
+    expected = _min_dim_token(min_w, min_h)
+    if supplied != expected:
+        return _bad("confirm_mismatch", expected=expected)
+    async with get_session() as session:
+        deleted = await session.run_sync(
+            lambda s: cleanup_service.delete_min_dimension_violations(
+                s, min_width=min_w, min_height=min_h, images_root=IMAGES_ROOT,
+            )
+        )
+        await session.commit()
+    return jsonify({"deleted": deleted})
+
+
+@cleanup_bp.route("/audit", methods=["POST"])
+async def audit_create():
+    body = await request.get_json(silent=True) or {}
+    rule = body.get("rule")
+    params = body.get("params") or {}
+    if rule not in ("transparency", "single_color"):
+        return _bad("invalid_rule")
+    if not isinstance(params, dict):
+        return _bad("invalid_params")
+    async with get_session() as session:
+        try:
+            audit_id = await session.run_sync(
+                lambda s: cleanup_service.start_audit_run(
+                    s, rule=rule, params=params,
+                )
+            )
+        except cleanup_service.AuditAlreadyRunning as running_id:
+            return _bad(
+                "audit_already_running", status=409,
+                running_id=int(str(running_id)),
+            )
+        except ValueError as exc:
+            return _bad(str(exc))
+        await session.commit()
+    return jsonify({"audit_id": audit_id, "status": "running"}), 202
+
+
+@cleanup_bp.route("/audit/<int:audit_id>", methods=["GET"])
+async def audit_get(audit_id: int):
+    async with get_session() as session:
+        audit = (await session.execute(
+            select(LibraryAuditRun).where(LibraryAuditRun.id == audit_id)
+        )).scalar_one_or_none()
+        if audit is None:
+            return _bad("not_found", status=404)
+        return jsonify(_serialize_audit_run(audit))
+
+
+@cleanup_bp.route("/audit", methods=["GET"])
+async def audit_history():
+    try:
+        limit = min(int(request.args.get("limit", "20")), 100)
+    except ValueError:
+        return _bad("invalid_limit")
+    async with get_session() as session:
+        rows = (await session.execute(
+            select(LibraryAuditRun)
+            .order_by(LibraryAuditRun.id.desc())
+            .limit(limit)
+        )).scalars().all()
+        return jsonify({"runs": [_serialize_audit_run(r) for r in rows]})
+
+
+@cleanup_bp.route("/audit/<int:audit_id>/apply", methods=["POST"])
+async def audit_apply(audit_id: int):
+    body = await request.get_json(silent=True) or {}
+    confirm = body.get("confirm", "")
+    async with get_session() as session:
+        try:
+            deleted = await session.run_sync(
+                lambda s: cleanup_service.apply_audit_run(
+                    s, audit_id=audit_id, confirm_token=confirm,
+                    images_root=IMAGES_ROOT,
+                )
+            )
+        except cleanup_service.AuditNotReady as exc:
+            return _bad("audit_not_ready", current_status=str(exc))
+        except cleanup_service.ConfirmTokenMismatch as exc:
+            return _bad("confirm_mismatch", expected=str(exc))
+        except ValueError as exc:
+            return _bad("not_found", status=404, detail=str(exc))
+        await session.commit()
+    return jsonify({"deleted": deleted})
+
+
+@cleanup_bp.route("/audit/<int:audit_id>/cancel", methods=["POST"])
+async def audit_cancel(audit_id: int):
+    async with get_session() as session:
+        await session.run_sync(
+            lambda s: cleanup_service.cancel_audit_run(s, audit_id=audit_id)
+        )
+        await session.commit()
+    return jsonify({"cancelled": True})
diff --git a/backend/app/api/extension.py b/backend/app/api/extension.py
index 54d569f..4f4766f 100644
--- a/backend/app/api/extension.py
+++ b/backend/app/api/extension.py
@@ -93,10 +93,20 @@ def _read_manifest_sync() -> dict | None:
     asyncio.to_thread (ASYNC240: no pathlib I/O in async functions)."""
     if not XPI_DIR.is_dir():
         return None
-    xpis = sorted(XPI_DIR.glob("fabledcurator-*.xpi"), key=lambda p: p.stat().st_mtime)
-    if not xpis:
+    # Exclude the `fabledcurator-latest.xpi` alias when picking the file to
+    # extract a version from — it's a copy of the latest versioned XPI,
+    # written at the same mtime by build.yml, and would otherwise tie or
+    # win the sort (operator-flagged 2026-05-26: UI displayed "v latest"
+    # because `_extract_version("fabledcurator-latest.xpi")` returns
+    # the literal "latest"). The alias still serves as `latest_url`.
+    versioned = [
+        p for p in XPI_DIR.glob("fabledcurator-*.xpi")
+        if p.name != "fabledcurator-latest.xpi"
+    ]
+    if not versioned:
         return None
-    latest = xpis[-1]
+    versioned.sort(key=lambda p: p.stat().st_mtime)
+    latest = versioned[-1]
     return {
         "installed": True,
         "version": _extract_version(latest.name),
diff --git a/backend/app/services/cleanup_service.py b/backend/app/services/cleanup_service.py
index b8325d5..7025b8b 100644
--- a/backend/app/services/cleanup_service.py
+++ b/backend/app/services/cleanup_service.py
@@ -481,7 +481,11 @@ def apply_audit_run(
         raise ValueError(f"audit_run {audit_id} not found")
     if audit.status != "ready":
         raise AuditNotReady(audit.status)
-    expected = f"apply-audit-{audit_id}"
+    # Token format matches modal/DestructiveConfirmModal.vue convention:
+    # ${action}-${kind}-${runId}. The modal hardcodes action ∈ {'restore',
+    # 'delete'}; "apply audit" is semantically a delete of the matched
+    # images, so we use 'delete-audit-<id>' (not 'apply-audit-<id>').
+    expected = f"delete-audit-{audit_id}"
     if confirm_token != expected:
         raise ConfirmTokenMismatch(expected)
     ids = list(audit.matched_ids or [])
diff --git a/backend/app/services/importer.py b/backend/app/services/importer.py
index fb9d0e3..3223ec7 100644
--- a/backend/app/services/importer.py
+++ b/backend/app/services/importer.py
@@ -18,6 +18,7 @@ from pathlib import Path
 
 from PIL import Image
 from sqlalchemy import select
+from sqlalchemy.exc import IntegrityError
 from sqlalchemy.orm import Session
 
 from ..models import (
@@ -202,6 +203,80 @@ class Importer:
                 (phash, width or 0, height or 0, image_id)
             )
 
+    def _find_or_create_source(
+        self, *, artist_id: int, platform: str, url: str,
+    ) -> Source:
+        """Race-safe find-or-create on `source` keyed by
+        (artist_id, platform, url) — the same key as the
+        `uq_source_artist_platform_url` constraint.
+
+        Two concurrent workers processing different files in the same
+        post can both find no existing Source row then both INSERT,
+        which trips the unique constraint and poisons the session with
+        `psycopg.errors.UniqueViolation`. Operator-flagged 2026-05-26.
+
+        Pattern: select; if absent, open a savepoint and INSERT.
+        On IntegrityError, roll the savepoint back (NOT the outer
+        transaction, which would lose the surrounding scan's progress)
+        and re-select — the concurrent op just created the row we
+        wanted, so the second select will find it.
+        """
+        existing = self.session.execute(
+            select(Source).where(
+                Source.artist_id == artist_id,
+                Source.platform == platform,
+                Source.url == url,
+            )
+        ).scalar_one_or_none()
+        if existing is not None:
+            return existing
+        sp = self.session.begin_nested()
+        try:
+            row = Source(artist_id=artist_id, platform=platform, url=url)
+            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,
+                    Source.url == url,
+                )
+            ).scalar_one()
+
+    def _find_or_create_post(
+        self, *, source_id: int, external_post_id: str,
+    ) -> Post:
+        """Race-safe find-or-create on `post` keyed by
+        (source_id, external_post_id). Mirrors `_find_or_create_source`
+        — same savepoint + IntegrityError-recovery pattern."""
+        existing = self.session.execute(
+            select(Post).where(
+                Post.source_id == source_id,
+                Post.external_post_id == external_post_id,
+            )
+        ).scalar_one_or_none()
+        if existing is not None:
+            return existing
+        sp = self.session.begin_nested()
+        try:
+            row = Post(source_id=source_id, external_post_id=external_post_id)
+            self.session.add(row)
+            self.session.flush()
+            sp.commit()
+            return row
+        except IntegrityError:
+            sp.rollback()
+            return self.session.execute(
+                select(Post).where(
+                    Post.source_id == source_id,
+                    Post.external_post_id == external_post_id,
+                )
+            ).scalar_one()
+
     def import_one(self, source: Path) -> ImportResult:
         """Dispatch by kind. Media → normal pipeline. Archive → extract
         media members (one Post via the archive-adjacent sidecar) and
@@ -241,29 +316,13 @@ class Importer:
         sd = parse_sidecar(data)
         platform = sd.platform or "unknown"
         url = sd.post_url or f"sidecar:{platform}"
-        src = self.session.execute(
-            select(Source).where(
-                Source.artist_id == artist.id,
-                Source.platform == platform,
-                Source.url == url,
-            )
-        ).scalar_one_or_none()
-        if src is None:
-            src = Source(artist_id=artist.id, platform=platform, url=url)
-            self.session.add(src)
-            self.session.flush()
+        src = self._find_or_create_source(
+            artist_id=artist.id, platform=platform, url=url,
+        )
         epid = sd.external_post_id or sc.stem
-        post = self.session.execute(
-            select(Post).where(
-                Post.source_id == src.id,
-                Post.external_post_id == epid,
-            )
-        ).scalar_one_or_none()
-        if post is None:
-            post = Post(source_id=src.id, external_post_id=epid)
-            self.session.add(post)
-            self.session.flush()
-        return post
+        return self._find_or_create_post(
+            source_id=src.id, external_post_id=epid,
+        )
 
     def _capture_attachment(
         self, source: Path, *, post: Post | None = None,
@@ -705,29 +764,14 @@ class Importer:
         else:
             platform = sd.platform or "unknown"
             url = sd.post_url or f"sidecar:{platform}"
-            src = self.session.execute(
-                select(Source).where(
-                    Source.artist_id == artist.id,
-                    Source.platform == platform,
-                    Source.url == url,
-                )
-            ).scalar_one_or_none()
-            if src is None:
-                src = Source(artist_id=artist.id, platform=platform, url=url)
-                self.session.add(src)
-                self.session.flush()
+            src = self._find_or_create_source(
+                artist_id=artist.id, platform=platform, url=url,
+            )
 
         epid = sd.external_post_id or sc.stem
-        post = self.session.execute(
-            select(Post).where(
-                Post.source_id == src.id,
-                Post.external_post_id == epid,
-            )
-        ).scalar_one_or_none()
-        if post is None:
-            post = Post(source_id=src.id, external_post_id=epid)
-            self.session.add(post)
-            self.session.flush()
+        post = self._find_or_create_post(
+            source_id=src.id, external_post_id=epid,
+        )
         if sd.post_url is not None:
             post.post_url = sd.post_url
         if sd.post_title is not None:
diff --git a/frontend/src/components/cleanup/MinDimensionCard.vue b/frontend/src/components/cleanup/MinDimensionCard.vue
new file mode 100644
index 0000000..a26ae2d
--- /dev/null
+++ b/frontend/src/components/cleanup/MinDimensionCard.vue
@@ -0,0 +1,127 @@
+<template>
+  <v-card class="fc-clean-card">
+    <v-card-title class="d-flex align-center" style="gap: 10px;">
+      <v-icon icon="mdi-image-size-select-small" size="small" />
+      <span>Minimum dimensions</span>
+    </v-card-title>
+    <v-card-text>
+      <p class="fc-muted text-body-2 mb-3">
+        Find and delete images smaller than the threshold. Mirrors the
+        import-time <code>min_width</code> / <code>min_height</code>
+        filter, applied retroactively to the existing library.
+      </p>
+
+      <v-row dense>
+        <v-col cols="6">
+          <v-text-field
+            v-model.number="minW" label="Min width (px)" type="number"
+            min="0" density="compact" hide-details
+          />
+        </v-col>
+        <v-col cols="6">
+          <v-text-field
+            v-model.number="minH" label="Min height (px)" type="number"
+            min="0" density="compact" hide-details
+          />
+        </v-col>
+      </v-row>
+
+      <div class="d-flex align-center mt-3" style="gap: 10px;">
+        <v-btn
+          color="accent" variant="flat" rounded="pill"
+          prepend-icon="mdi-magnify"
+          :loading="busy"
+          @click="onPreview"
+        >Preview</v-btn>
+
+        <span v-if="preview" class="text-body-2">
+          <strong>{{ preview.count }}</strong> image(s) would be deleted.
+        </span>
+      </div>
+
+      <v-btn
+        v-if="preview && preview.count > 0"
+        class="mt-3"
+        color="error" variant="flat" rounded="pill"
+        prepend-icon="mdi-delete"
+        @click="onDeleteClick"
+      >Delete {{ preview.count }} matching...</v-btn>
+    </v-card-text>
+
+    <DestructiveConfirmModal
+      v-model="showModal"
+      action="delete"
+      kind="min-dim"
+      :run-id="tokenSha8"
+      tier="C"
+      :projected-counts="projectedCounts"
+      :description="`Width < ${minW} OR height < ${minH}`"
+      @confirm="onConfirmedDelete"
+    />
+  </v-card>
+</template>
+
+<script setup>
+import { onMounted, ref } from 'vue'
+
+import DestructiveConfirmModal from '../modal/DestructiveConfirmModal.vue'
+import { useCleanupStore } from '../../stores/cleanup.js'
+
+const store = useCleanupStore()
+const minW = ref(0)
+const minH = ref(0)
+const preview = ref(null)
+const busy = ref(false)
+const showModal = ref(false)
+const tokenSha8 = ref('')
+const projectedCounts = ref({})
+
+onMounted(async () => {
+  await store.loadDefaults()
+  minW.value = store.defaults.min_width
+  minH.value = store.defaults.min_height
+})
+
+// SHA-256 truncated to 8 hex chars — matches the backend's
+// _min_dim_token() exactly. Web Crypto rejects MD5 as insecure.
+async function sha8(canon) {
+  const enc = new TextEncoder()
+  const buf = await crypto.subtle.digest('SHA-256', enc.encode(canon))
+  const hex = Array.from(new Uint8Array(buf)).map(b => b.toString(16).padStart(2, '0')).join('')
+  return hex.slice(0, 8)
+}
+
+async function onPreview() {
+  busy.value = true
+  try {
+    preview.value = await store.previewMinDim(minW.value, minH.value)
+  } catch (e) {
+    window.__fcToast?.({ text: `Preview failed: ${e.message}`, type: 'error' })
+  } finally {
+    busy.value = false
+  }
+}
+
+async function onDeleteClick() {
+  tokenSha8.value = await sha8(`${minW.value}x${minH.value}`)
+  projectedCounts.value = { 'Images to delete': preview.value.count }
+  showModal.value = true
+}
+
+async function onConfirmedDelete(token) {
+  try {
+    const res = await store.deleteMinDim(minW.value, minH.value, token)
+    window.__fcToast?.({
+      text: `Deleted ${res.deleted} image(s)`, type: 'success',
+    })
+    preview.value = null
+  } catch (e) {
+    window.__fcToast?.({ text: `Delete failed: ${e.message}`, type: 'error' })
+  }
+}
+</script>
+
+<style scoped>
+.fc-clean-card { border-radius: 8px; }
+.fc-muted { color: rgb(var(--v-theme-on-surface-variant)); }
+</style>
diff --git a/frontend/src/components/cleanup/SingleColorAuditCard.vue b/frontend/src/components/cleanup/SingleColorAuditCard.vue
new file mode 100644
index 0000000..ff2ecbe
--- /dev/null
+++ b/frontend/src/components/cleanup/SingleColorAuditCard.vue
@@ -0,0 +1,183 @@
+<template>
+  <v-card class="fc-clean-card">
+    <v-card-title class="d-flex align-center" style="gap: 10px;">
+      <v-icon icon="mdi-palette-swatch" size="small" />
+      <span>Single-color audit</span>
+    </v-card-title>
+    <v-card-text>
+      <p class="fc-muted text-body-2 mb-3">
+        Scan library for images dominated by one color within the
+        tolerance. Catches placeholder / solid-fill / error-page images
+        that slipped through the import filter. Same background-scan
+        cadence as the transparency audit.
+      </p>
+
+      <v-row dense>
+        <v-col cols="6">
+          <v-text-field
+            v-model.number="threshold" label="Threshold (0–1)"
+            type="number" min="0" max="1" step="0.01"
+            density="compact" hide-details
+            :disabled="audit && audit.status === 'running'"
+          />
+        </v-col>
+        <v-col cols="6">
+          <v-text-field
+            v-model.number="tolerance" label="Color tolerance (0–441)"
+            type="number" min="0" max="441"
+            density="compact" hide-details
+            :disabled="audit && audit.status === 'running'"
+          />
+        </v-col>
+      </v-row>
+
+      <v-btn
+        v-if="!audit || audit.status !== 'running'"
+        class="mt-3"
+        color="accent" variant="flat" rounded="pill"
+        prepend-icon="mdi-magnify-scan"
+        :loading="busy"
+        @click="onStart"
+      >Scan library</v-btn>
+
+      <div v-if="audit && audit.status === 'running'" class="mt-3">
+        <v-progress-linear indeterminate color="accent" />
+        <div class="text-body-2 mt-2 d-flex align-center" style="gap: 10px;">
+          <span>
+            Scanning… {{ audit.scanned_count }} checked,
+            {{ audit.matched_count }} matched
+          </span>
+          <v-btn
+            variant="text" size="small" color="warning" rounded="pill"
+            @click="onCancel"
+          >Cancel</v-btn>
+        </div>
+      </div>
+
+      <div v-if="audit && audit.status === 'ready'" class="mt-3">
+        <p class="text-body-2 mb-2">
+          Scan complete. <strong>{{ audit.matched_count }}</strong>
+          image(s) match.
+        </p>
+        <v-btn
+          v-if="audit.matched_count > 0"
+          color="error" variant="flat" rounded="pill"
+          prepend-icon="mdi-delete"
+          @click="onApplyClick"
+        >Delete {{ audit.matched_count }} matching...</v-btn>
+      </div>
+
+      <v-alert
+        v-if="audit && audit.status === 'error'"
+        type="error" variant="tonal" density="compact" class="mt-3"
+      >Scan failed: {{ audit.error }}</v-alert>
+
+      <v-alert
+        v-if="audit && audit.status === 'applied'"
+        type="success" variant="tonal" density="compact" class="mt-3"
+      >Applied — matched images deleted.</v-alert>
+    </v-card-text>
+
+    <DestructiveConfirmModal
+      v-if="audit"
+      v-model="showModal"
+      action="delete"
+      kind="audit"
+      :run-id="audit.id"
+      tier="C"
+      :projected-counts="projectedCounts"
+      description="Permanently deletes images matched by the single-color scan."
+      @confirm="onConfirmedApply"
+    />
+  </v-card>
+</template>
+
+<script setup>
+import { onMounted, onUnmounted, ref } from 'vue'
+
+import DestructiveConfirmModal from '../modal/DestructiveConfirmModal.vue'
+import { useCleanupStore } from '../../stores/cleanup.js'
+
+const store = useCleanupStore()
+const threshold = ref(0.95)
+const tolerance = ref(30)
+const audit = ref(null)
+const busy = ref(false)
+const showModal = ref(false)
+const projectedCounts = ref({})
+let pollTimer = null
+
+onMounted(async () => {
+  await store.loadDefaults()
+  threshold.value = store.defaults.single_color_threshold
+  tolerance.value = store.defaults.single_color_tolerance
+})
+
+onUnmounted(() => stopPoll())
+
+function startPoll(id) {
+  stopPoll()
+  pollTimer = setInterval(async () => {
+    try {
+      const fresh = await store.getAudit(id)
+      audit.value = fresh
+      if (fresh.status !== 'running') stopPoll()
+    } catch (e) {
+      stopPoll()
+      window.__fcToast?.({ text: `Audit poll failed: ${e.message}`, type: 'error' })
+    }
+  }, 5000)
+}
+
+function stopPoll() {
+  if (pollTimer) { clearInterval(pollTimer); pollTimer = null }
+}
+
+async function onStart() {
+  busy.value = true
+  try {
+    const res = await store.startAudit('single_color', {
+      threshold: threshold.value, tolerance: tolerance.value,
+    })
+    audit.value = await store.getAudit(res.audit_id)
+    startPoll(res.audit_id)
+  } catch (e) {
+    window.__fcToast?.({ text: `Scan start failed: ${e.message}`, type: 'error' })
+  } finally {
+    busy.value = false
+  }
+}
+
+async function onCancel() {
+  if (!audit.value) return
+  try {
+    await store.cancelAudit(audit.value.id)
+    audit.value = await store.getAudit(audit.value.id)
+    stopPoll()
+  } catch (e) {
+    window.__fcToast?.({ text: `Cancel failed: ${e.message}`, type: 'error' })
+  }
+}
+
+function onApplyClick() {
+  projectedCounts.value = { 'Images to delete': audit.value.matched_count }
+  showModal.value = true
+}
+
+async function onConfirmedApply(token) {
+  try {
+    const res = await store.applyAudit(audit.value.id, token)
+    window.__fcToast?.({
+      text: `Deleted ${res.deleted} image(s)`, type: 'success',
+    })
+    audit.value = await store.getAudit(audit.value.id)
+  } catch (e) {
+    window.__fcToast?.({ text: `Apply failed: ${e.message}`, type: 'error' })
+  }
+}
+</script>
+
+<style scoped>
+.fc-clean-card { border-radius: 8px; }
+.fc-muted { color: rgb(var(--v-theme-on-surface-variant)); }
+</style>
diff --git a/frontend/src/components/cleanup/TransparencyAuditCard.vue b/frontend/src/components/cleanup/TransparencyAuditCard.vue
new file mode 100644
index 0000000..4e91ac0
--- /dev/null
+++ b/frontend/src/components/cleanup/TransparencyAuditCard.vue
@@ -0,0 +1,166 @@
+<template>
+  <v-card class="fc-clean-card">
+    <v-card-title class="d-flex align-center" style="gap: 10px;">
+      <v-icon icon="mdi-checkerboard" size="small" />
+      <span>Transparency audit</span>
+    </v-card-title>
+    <v-card-text>
+      <p class="fc-muted text-body-2 mb-3">
+        Scan library for images whose transparent-pixel fraction exceeds
+        the threshold. Animated WebPs / GIFs are skipped (the import-side
+        rule does the same). Runs as a background task — ~50ms per image,
+        so a 57k library takes ~50 minutes.
+      </p>
+
+      <v-text-field
+        v-model.number="threshold" label="Transparency threshold (0–1)"
+        type="number" min="0" max="1" step="0.01" density="compact" hide-details
+        :disabled="audit && audit.status === 'running'"
+        class="mb-3"
+      />
+
+      <v-btn
+        v-if="!audit || audit.status !== 'running'"
+        color="accent" variant="flat" rounded="pill"
+        prepend-icon="mdi-magnify-scan"
+        :loading="busy"
+        @click="onStart"
+      >Scan library</v-btn>
+
+      <div v-if="audit && audit.status === 'running'" class="mt-3">
+        <v-progress-linear indeterminate color="accent" />
+        <div class="text-body-2 mt-2 d-flex align-center" style="gap: 10px;">
+          <span>
+            Scanning… {{ audit.scanned_count }} checked,
+            {{ audit.matched_count }} matched
+          </span>
+          <v-btn
+            variant="text" size="small" color="warning" rounded="pill"
+            @click="onCancel"
+          >Cancel</v-btn>
+        </div>
+      </div>
+
+      <div v-if="audit && audit.status === 'ready'" class="mt-3">
+        <p class="text-body-2 mb-2">
+          Scan complete. <strong>{{ audit.matched_count }}</strong>
+          image(s) match.
+        </p>
+        <v-btn
+          v-if="audit.matched_count > 0"
+          color="error" variant="flat" rounded="pill"
+          prepend-icon="mdi-delete"
+          @click="onApplyClick"
+        >Delete {{ audit.matched_count }} matching...</v-btn>
+      </div>
+
+      <v-alert
+        v-if="audit && audit.status === 'error'"
+        type="error" variant="tonal" density="compact" class="mt-3"
+      >Scan failed: {{ audit.error }}</v-alert>
+
+      <v-alert
+        v-if="audit && audit.status === 'applied'"
+        type="success" variant="tonal" density="compact" class="mt-3"
+      >Applied — matched images deleted.</v-alert>
+    </v-card-text>
+
+    <DestructiveConfirmModal
+      v-if="audit"
+      v-model="showModal"
+      action="delete"
+      kind="audit"
+      :run-id="audit.id"
+      tier="C"
+      :projected-counts="projectedCounts"
+      description="Permanently deletes images matched by the transparency scan."
+      @confirm="onConfirmedApply"
+    />
+  </v-card>
+</template>
+
+<script setup>
+import { onMounted, onUnmounted, ref } from 'vue'
+
+import DestructiveConfirmModal from '../modal/DestructiveConfirmModal.vue'
+import { useCleanupStore } from '../../stores/cleanup.js'
+
+const store = useCleanupStore()
+const threshold = ref(0.9)
+const audit = ref(null)
+const busy = ref(false)
+const showModal = ref(false)
+const projectedCounts = ref({})
+let pollTimer = null
+
+onMounted(async () => {
+  await store.loadDefaults()
+  threshold.value = store.defaults.transparency_threshold
+})
+
+onUnmounted(() => stopPoll())
+
+function startPoll(id) {
+  stopPoll()
+  pollTimer = setInterval(async () => {
+    try {
+      const fresh = await store.getAudit(id)
+      audit.value = fresh
+      if (fresh.status !== 'running') stopPoll()
+    } catch (e) {
+      stopPoll()
+      window.__fcToast?.({ text: `Audit poll failed: ${e.message}`, type: 'error' })
+    }
+  }, 5000)
+}
+
+function stopPoll() {
+  if (pollTimer) { clearInterval(pollTimer); pollTimer = null }
+}
+
+async function onStart() {
+  busy.value = true
+  try {
+    const res = await store.startAudit('transparency', { threshold: threshold.value })
+    audit.value = await store.getAudit(res.audit_id)
+    startPoll(res.audit_id)
+  } catch (e) {
+    window.__fcToast?.({ text: `Scan start failed: ${e.message}`, type: 'error' })
+  } finally {
+    busy.value = false
+  }
+}
+
+async function onCancel() {
+  if (!audit.value) return
+  try {
+    await store.cancelAudit(audit.value.id)
+    audit.value = await store.getAudit(audit.value.id)
+    stopPoll()
+  } catch (e) {
+    window.__fcToast?.({ text: `Cancel failed: ${e.message}`, type: 'error' })
+  }
+}
+
+function onApplyClick() {
+  projectedCounts.value = { 'Images to delete': audit.value.matched_count }
+  showModal.value = true
+}
+
+async function onConfirmedApply(token) {
+  try {
+    const res = await store.applyAudit(audit.value.id, token)
+    window.__fcToast?.({
+      text: `Deleted ${res.deleted} image(s)`, type: 'success',
+    })
+    audit.value = await store.getAudit(audit.value.id)
+  } catch (e) {
+    window.__fcToast?.({ text: `Apply failed: ${e.message}`, type: 'error' })
+  }
+}
+</script>
+
+<style scoped>
+.fc-clean-card { border-radius: 8px; }
+.fc-muted { color: rgb(var(--v-theme-on-surface-variant)); }
+</style>
diff --git a/frontend/src/components/common/ErrorDetailModal.vue b/frontend/src/components/common/ErrorDetailModal.vue
new file mode 100644
index 0000000..d8281a5
--- /dev/null
+++ b/frontend/src/components/common/ErrorDetailModal.vue
@@ -0,0 +1,87 @@
+<template>
+  <v-dialog :model-value="modelValue" max-width="900"
+            @update:model-value="$emit('update:modelValue', $event)">
+    <v-card>
+      <v-card-title class="d-flex align-center" style="gap: 12px;">
+        <v-icon icon="mdi-alert-circle-outline" color="error" />
+        <span>{{ title }}</span>
+        <v-spacer />
+        <v-btn icon variant="text" size="small" @click="close">
+          <v-icon>mdi-close</v-icon>
+        </v-btn>
+      </v-card-title>
+      <v-card-text>
+        <pre class="fc-err-pre">{{ message || '(no error message)' }}</pre>
+      </v-card-text>
+      <v-card-actions>
+        <v-btn
+          variant="text" rounded="pill" size="small"
+          :prepend-icon="copied ? 'mdi-check' : 'mdi-content-copy'"
+          @click="onCopy"
+        >{{ copied ? 'Copied' : 'Copy' }}</v-btn>
+        <v-spacer />
+        <v-btn variant="text" rounded="pill" @click="close">Close</v-btn>
+      </v-card-actions>
+    </v-card>
+  </v-dialog>
+</template>
+
+<script setup>
+import { ref, watch } from 'vue'
+
+const props = defineProps({
+  modelValue: { type: Boolean, default: false },
+  title: { type: String, default: 'Error details' },
+  message: { type: String, default: '' },
+})
+
+const emit = defineEmits(['update:modelValue'])
+
+const copied = ref(false)
+let copiedTimer = null
+
+watch(() => props.modelValue, (open) => {
+  if (!open) {
+    copied.value = false
+    if (copiedTimer) { clearTimeout(copiedTimer); copiedTimer = null }
+  }
+})
+
+function close() {
+  emit('update:modelValue', false)
+}
+
+async function onCopy() {
+  try {
+    await navigator.clipboard.writeText(props.message || '')
+    copied.value = true
+    if (copiedTimer) clearTimeout(copiedTimer)
+    copiedTimer = setTimeout(() => { copied.value = false }, 1500)
+  } catch (e) {
+    window.__fcToast?.({ text: `Copy failed: ${e.message}`, type: 'error' })
+  }
+}
+</script>
+
+<style scoped>
+/* The full error often contains a SQLAlchemy statement + parameters
+   block + multi-line traceback. Pre-wrap keeps long lines readable;
+   monospace + tabular layout keeps the structure scannable. The
+   max-height + overflow-auto prevents a 50-line traceback from
+   pushing the Close button off-screen. Operator-flagged 2026-05-26:
+   the prior :title="..." tooltip was unusable for content this long. */
+.fc-err-pre {
+  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
+  font-size: 12px;
+  line-height: 1.5;
+  white-space: pre-wrap;
+  word-break: break-word;
+  background: rgb(var(--v-theme-surface-variant, 38 36 41));
+  color: rgb(var(--v-theme-on-surface));
+  padding: 12px 14px;
+  border-radius: 6px;
+  max-height: 60vh;
+  overflow: auto;
+  margin: 0;
+}
+</style>
diff --git a/frontend/src/components/settings/BrowserExtensionCard.vue b/frontend/src/components/settings/BrowserExtensionCard.vue
index 2dbe591..db5d3a3 100644
--- a/frontend/src/components/settings/BrowserExtensionCard.vue
+++ b/frontend/src/components/settings/BrowserExtensionCard.vue
@@ -34,11 +34,18 @@
 
       <template v-else-if="manifest?.installed">
         <div class="fc-ext-install mt-3">
+          <!-- Install button: direct :href anchor click (no programmatic
+               window.location.assign). Firefox's XPI-install gesture
+               requires a user-clicked anchor pointing at an
+               application/x-xpinstall response; programmatic navigation
+               sometimes triggered nothing instead of the install dialog
+               (operator-flagged 2026-05-26). No `download` attribute —
+               that would force a save dialog instead of install. -->
           <v-btn
             v-if="isFirefox"
             color="accent" variant="flat" rounded="pill"
             prepend-icon="mdi-firefox"
-            @click="installXpi"
+            :href="manifest.latest_url"
           >Install Firefox extension</v-btn>
 
           <v-btn
@@ -146,11 +153,6 @@ async function loadKey() {
   }
 }
 
-function installXpi() {
-  if (!manifest.value?.latest_url) return
-  window.location.assign(manifest.value.latest_url)
-}
-
 async function rotateKey() {
   rotating.value = true
   try {
diff --git a/frontend/src/components/settings/ImportTaskList.vue b/frontend/src/components/settings/ImportTaskList.vue
index c3edbd1..97bbebf 100644
--- a/frontend/src/components/settings/ImportTaskList.vue
+++ b/frontend/src/components/settings/ImportTaskList.vue
@@ -45,9 +45,11 @@
       <template #item.size_bytes="{ item }">{{ formatBytes(item.size_bytes) }}</template>
       <template #item.created_at="{ item }">{{ formatDate(item.created_at) }}</template>
       <template #item.error="{ item }">
-        <span v-if="item.error" :title="item.error" class="text-caption">
-          {{ shorten(item.error, 60) }}
-        </span>
+        <button
+          v-if="item.error" type="button" class="fc-err-link text-caption"
+          @click="openError(`Task ${item.id} failed`, item.error)"
+          title="Click for full error"
+        >{{ shorten(item.error, 60) }}</button>
       </template>
     </v-data-table-virtual>
     <div v-if="store.hasMore" class="d-flex justify-center py-3">
@@ -100,16 +102,35 @@
         </v-card-actions>
       </v-card>
     </v-dialog>
+
+    <ErrorDetailModal
+      v-model="showErrorModal"
+      :title="errorModalTitle"
+      :message="errorModalMessage"
+    />
   </v-card>
 </template>
 
 <script setup>
 import { computed, ref } from 'vue'
 import { useImportStore } from '../../stores/import.js'
+import ErrorDetailModal from '../common/ErrorDetailModal.vue'
 
 const store = useImportStore()
 const statusFilter = ref(null)
 const clearDialog = ref(false)
+// Click-to-open modal for full error text (operator-flagged 2026-05-26
+// — the prior :title="..." tooltip cramped multi-line SQLAlchemy
+// tracebacks into an unusable popup with no copy-paste affordance).
+const showErrorModal = ref(false)
+const errorModalTitle = ref('')
+const errorModalMessage = ref('')
+
+function openError(title, message) {
+  errorModalTitle.value = title
+  errorModalMessage.value = message || ''
+  showErrorModal.value = true
+}
 const clearAgeDays = ref(7)
 const clearStuckDialog = ref(false)
 
@@ -179,3 +200,21 @@ async function onClearStuckConfirm() {
   clearStuckDialog.value = false
 }
 </script>
+
+<style scoped>
+.fc-err-link {
+  /* Truncated error preview as a clickable button — opens
+     ErrorDetailModal with the full text. Inherits the row's font
+     sizing so it doesn't visually drift from the prior tooltip-bearing
+     span. */
+  color: rgb(var(--v-theme-error, 220 80 80));
+  background: transparent;
+  border: 0;
+  padding: 0;
+  font: inherit;
+  text-align: left;
+  text-decoration: underline dotted;
+  cursor: pointer;
+}
+.fc-err-link:hover { text-decoration: underline; }
+</style>
diff --git a/frontend/src/components/settings/MaintenancePanel.vue b/frontend/src/components/settings/MaintenancePanel.vue
index 0f39bac..90c410b 100644
--- a/frontend/src/components/settings/MaintenancePanel.vue
+++ b/frontend/src/components/settings/MaintenancePanel.vue
@@ -13,7 +13,9 @@
     <AllowlistTable class="mt-4" />
     <AliasTable class="mt-4" />
     <BackupCard class="mt-6" />
-    <TagMaintenanceCard class="mt-6" />
+    <!-- TagMaintenanceCard moved to Cleanup tab (v26.05.25.7) — it
+         operates on the existing library which fits the Cleanup-tab
+         theme, and clusters with the other audit cards. -->
     <LegacyMigrationCard class="mt-6" />
   </div>
 </template>
@@ -25,7 +27,6 @@ import MLThresholdSliders from './MLThresholdSliders.vue'
 import AllowlistTable from './AllowlistTable.vue'
 import AliasTable from './AliasTable.vue'
 import BackupCard from './BackupCard.vue'
-import TagMaintenanceCard from './TagMaintenanceCard.vue'
 import LegacyMigrationCard from './LegacyMigrationCard.vue'
 </script>
 
diff --git a/frontend/src/components/settings/SystemActivityTab.vue b/frontend/src/components/settings/SystemActivityTab.vue
index 1db2724..f623bb0 100644
--- a/frontend/src/components/settings/SystemActivityTab.vue
+++ b/frontend/src/components/settings/SystemActivityTab.vue
@@ -59,8 +59,12 @@
               <td>{{ r.queue }}</td>
               <td><code>{{ shortTaskName(r.task_name) }}</code></td>
               <td class="fc-tabular">{{ r.target_id ?? '—' }}</td>
-              <td class="fc-err" :title="r.error_message">
-                {{ r.error_type }}
+              <td>
+                <button
+                  type="button" class="fc-err-link"
+                  @click="openError(r.error_type, r.error_message)"
+                  :title="'Click for full error'"
+                >{{ r.error_type }}</button>
               </td>
             </tr>
             <tr v-if="!filteredFailures.length">
@@ -138,6 +142,12 @@
         </div>
       </v-card-text>
     </v-card>
+
+    <ErrorDetailModal
+      v-model="showErrorModal"
+      :title="errorModalTitle"
+      :message="errorModalMessage"
+    />
   </div>
 </template>
 
@@ -145,8 +155,23 @@
 import { computed, onMounted, onUnmounted, ref } from 'vue'
 
 import { useSystemActivityStore } from '../../stores/systemActivity.js'
+import ErrorDetailModal from '../common/ErrorDetailModal.vue'
 import QueuesTable from './QueuesTable.vue'
 
+// Click-to-open modal for full error text. Replaces the unusable
+// :title="..." tooltip (operator-flagged 2026-05-26: SQLAlchemy
+// rollback + traceback content rendered as a cramped browser tooltip
+// you couldn't copy from or scroll within).
+const showErrorModal = ref(false)
+const errorModalTitle = ref('')
+const errorModalMessage = ref('')
+
+function openError(title, message) {
+  errorModalTitle.value = title || 'Error details'
+  errorModalMessage.value = message || ''
+  showErrorModal.value = true
+}
+
 const store = useSystemActivityStore()
 
 const filterQueue = ref(null)
@@ -276,5 +301,18 @@ function formatRelative(iso) {
   font-feature-settings: 'tnum';
 }
 .fc-err { color: rgb(var(--v-theme-error, 220 80 80)); }
+.fc-err-link {
+  /* Styled as a text-only button so the error_type cell stays
+     visually identical to the prior tooltip-bearing row, but is
+     now a real clickable target with hover affordance. */
+  color: rgb(var(--v-theme-error, 220 80 80));
+  background: transparent;
+  border: 0;
+  padding: 0;
+  font: inherit;
+  text-decoration: underline dotted;
+  cursor: pointer;
+}
+.fc-err-link:hover { text-decoration: underline; }
 .fc-muted { color: rgb(var(--v-theme-on-surface-variant)); }
 </style>
diff --git a/frontend/src/stores/cleanup.js b/frontend/src/stores/cleanup.js
new file mode 100644
index 0000000..fac5112
--- /dev/null
+++ b/frontend/src/stores/cleanup.js
@@ -0,0 +1,72 @@
+import { defineStore } from 'pinia'
+import { ref } from 'vue'
+import { useApi } from '../composables/useApi.js'
+
+export const useCleanupStore = defineStore('cleanup', () => {
+  const api = useApi()
+
+  // Defaults sourced from ImportSettings on mount. Cards pre-fill from
+  // these so the common case ("apply current import filters
+  // retroactively") is one click; operator can override per-audit.
+  const defaults = ref({
+    min_width: 0,
+    min_height: 0,
+    transparency_threshold: 0.9,
+    single_color_threshold: 0.95,
+    single_color_tolerance: 30,
+  })
+
+  const recentRuns = ref([])
+
+  async function loadDefaults() {
+    const s = await api.get('/api/settings/import')
+    defaults.value = {
+      min_width: s.min_width ?? 0,
+      min_height: s.min_height ?? 0,
+      transparency_threshold: s.transparency_threshold ?? 0.9,
+      single_color_threshold: s.single_color_threshold ?? 0.95,
+      single_color_tolerance: s.single_color_tolerance ?? 30,
+    }
+  }
+
+  async function previewMinDim(min_width, min_height) {
+    return await api.post('/api/cleanup/min-dimension/preview', {
+      body: { min_width, min_height },
+    })
+  }
+
+  async function deleteMinDim(min_width, min_height, confirm) {
+    return await api.post('/api/cleanup/min-dimension/delete', {
+      body: { min_width, min_height, confirm },
+    })
+  }
+
+  async function startAudit(rule, params) {
+    return await api.post('/api/cleanup/audit', { body: { rule, params } })
+  }
+
+  async function getAudit(id) {
+    return await api.get(`/api/cleanup/audit/${id}`)
+  }
+
+  async function loadHistory(limit = 20) {
+    const body = await api.get(`/api/cleanup/audit?limit=${limit}`)
+    recentRuns.value = body.runs
+    return body.runs
+  }
+
+  async function applyAudit(id, confirm) {
+    return await api.post(`/api/cleanup/audit/${id}/apply`, { body: { confirm } })
+  }
+
+  async function cancelAudit(id) {
+    return await api.post(`/api/cleanup/audit/${id}/cancel`)
+  }
+
+  return {
+    defaults, recentRuns,
+    loadDefaults,
+    previewMinDim, deleteMinDim,
+    startAudit, getAudit, loadHistory, applyAudit, cancelAudit,
+  }
+})
diff --git a/frontend/src/views/CleanupView.vue b/frontend/src/views/CleanupView.vue
new file mode 100644
index 0000000..f02e63a
--- /dev/null
+++ b/frontend/src/views/CleanupView.vue
@@ -0,0 +1,31 @@
+<template>
+  <div class="fc-cleanup">
+    <p class="fc-muted text-body-2 mb-4">
+      Retroactive enforcement of import-filter rules. Each card scans the
+      existing library for content that the current import filters would
+      now exclude. Destructive — typed-token confirmation required.
+    </p>
+
+    <MinDimensionCard class="mb-4" />
+    <TransparencyAuditCard class="mb-4" />
+    <SingleColorAuditCard class="mb-4" />
+    <TagMaintenanceCard />
+  </div>
+</template>
+
+<script setup>
+import MinDimensionCard from '../components/cleanup/MinDimensionCard.vue'
+import TransparencyAuditCard from '../components/cleanup/TransparencyAuditCard.vue'
+import SingleColorAuditCard from '../components/cleanup/SingleColorAuditCard.vue'
+// Reuse existing TagMaintenanceCard (FC-3k) as-is — it already handles
+// preview + commit of prune-unused-tags via the admin store. Operator
+// confirmed 2026-05-26: don't duplicate into a new UnusedTagsCard.
+// MaintenancePanel drops its TagMaintenanceCard reference in the
+// SettingsView edit (Task 16) so this is now the sole rendering site.
+import TagMaintenanceCard from '../components/settings/TagMaintenanceCard.vue'
+</script>
+
+<style scoped>
+.fc-cleanup { max-width: 900px; }
+.fc-muted { color: rgb(var(--v-theme-on-surface-variant)); }
+</style>
diff --git a/frontend/src/views/SettingsView.vue b/frontend/src/views/SettingsView.vue
index 8d41770..99f536d 100644
--- a/frontend/src/views/SettingsView.vue
+++ b/frontend/src/views/SettingsView.vue
@@ -14,6 +14,7 @@
       <v-tab value="overview">Overview</v-tab>
       <v-tab value="activity">Activity</v-tab>
       <v-tab value="import">Import</v-tab>
+      <v-tab value="cleanup">Cleanup</v-tab>
       <v-tab value="maintenance">Maintenance</v-tab>
     </v-tabs>
 
@@ -53,6 +54,10 @@
         <ImportFiltersForm />
       </v-window-item>
 
+      <v-window-item value="cleanup">
+        <CleanupView />
+      </v-window-item>
+
       <v-window-item value="maintenance">
         <MaintenancePanel />
       </v-window-item>
@@ -72,6 +77,7 @@ import ImportTriggerPanel from '../components/settings/ImportTriggerPanel.vue'
 import ImportFiltersForm from '../components/settings/ImportFiltersForm.vue'
 import ImportTaskList from '../components/settings/ImportTaskList.vue'
 import MaintenancePanel from '../components/settings/MaintenancePanel.vue'
+import CleanupView from './CleanupView.vue'
 import { useMLStore } from '../stores/ml.js'
 
 const tab = ref('overview')
diff --git a/tests/test_api_cleanup.py b/tests/test_api_cleanup.py
new file mode 100644
index 0000000..ba9534f
--- /dev/null
+++ b/tests/test_api_cleanup.py
@@ -0,0 +1,215 @@
+"""API tests for the /api/cleanup/* blueprint.
+
+Per reference-async-coredml-test-assertions, post-DML state checks go
+via column selects, not ORM entity access.
+"""
+
+import hashlib
+from datetime import UTC, datetime
+
+import pytest
+from PIL import Image
+from sqlalchemy import func, select
+
+from backend.app import create_app
+from backend.app.celery_app import celery
+from backend.app.models import ImageRecord, LibraryAuditRun
+
+pytestmark = pytest.mark.integration
+
+
+@pytest.fixture(autouse=True)
+def disable_celery_eager(monkeypatch):
+    monkeypatch.setattr(celery.conf, "task_always_eager", False)
+
+
+@pytest.fixture
+async def app():
+    return create_app()
+
+
+@pytest.fixture
+async def client(app):
+    async with app.test_client() as c:
+        yield c
+
+
+def _sha256_min_dim_token(min_w: int, min_h: int) -> str:
+    canon = f"{min_w}x{min_h}"
+    return f"delete-min-dim-{hashlib.sha256(canon.encode()).hexdigest()[:8]}"
+
+
+async def _seed_image(db, tmp_path, *, w, h, name):
+    path = tmp_path / name
+    Image.new("RGB", (w, h), (w % 256, h % 256, 0)).save(path)
+    sha = f"api-cleanup-{name}".ljust(64, "x")[:64]
+    rec = ImageRecord(
+        path=str(path), sha256=sha,
+        size_bytes=path.stat().st_size, mime="image/png",
+        width=w, height=h, origin="imported_filesystem",
+        integrity_status="ok",
+    )
+    db.add(rec)
+    await db.flush()
+    return rec
+
+
+@pytest.mark.asyncio
+async def test_min_dimension_preview_returns_count(client, db, tmp_path):
+    await _seed_image(db, tmp_path, w=50, h=50, name="small.png")
+    await _seed_image(db, tmp_path, w=500, h=500, name="big.png")
+    await db.commit()
+    resp = await client.post(
+        "/api/cleanup/min-dimension/preview",
+        json={"min_width": 200, "min_height": 200},
+    )
+    assert resp.status_code == 200
+    body = await resp.get_json()
+    assert body["count"] == 1
+
+
+@pytest.mark.asyncio
+async def test_min_dimension_delete_with_token_removes_rows(client, db, tmp_path):
+    await _seed_image(db, tmp_path, w=50, h=50, name="s2.png")
+    await _seed_image(db, tmp_path, w=500, h=500, name="b2.png")
+    await db.commit()
+    token = _sha256_min_dim_token(200, 200)
+    resp = await client.post(
+        "/api/cleanup/min-dimension/delete",
+        json={"min_width": 200, "min_height": 200, "confirm": token},
+    )
+    assert resp.status_code == 200
+    body = await resp.get_json()
+    assert body["deleted"] == 1
+    remaining = await db.execute(select(func.count()).select_from(ImageRecord))
+    assert remaining.scalar_one() == 1
+
+
+@pytest.mark.asyncio
+async def test_min_dimension_delete_with_bad_token_returns_400(client, db, tmp_path):
+    await _seed_image(db, tmp_path, w=50, h=50, name="s3.png")
+    await db.commit()
+    resp = await client.post(
+        "/api/cleanup/min-dimension/delete",
+        json={"min_width": 200, "min_height": 200, "confirm": "nope"},
+    )
+    assert resp.status_code == 400
+    body = await resp.get_json()
+    assert body["error"] == "confirm_mismatch"
+
+
+@pytest.mark.asyncio
+async def test_audit_create_returns_id_and_running_status(
+    client, db, monkeypatch,
+):
+    from backend.app.tasks import library_audit
+    monkeypatch.setattr(
+        library_audit.scan_library_for_rule, "delay", lambda audit_id: None,
+    )
+    resp = await client.post(
+        "/api/cleanup/audit",
+        json={"rule": "transparency", "params": {"threshold": 0.9}},
+    )
+    assert resp.status_code == 202
+    body = await resp.get_json()
+    assert body["status"] == "running"
+    assert isinstance(body["audit_id"], int)
+
+
+@pytest.mark.asyncio
+async def test_audit_create_returns_409_when_another_is_running(client, db):
+    audit = LibraryAuditRun(
+        rule="transparency", params={"threshold": 0.9},
+        status="running", matched_ids=[],
+    )
+    db.add(audit)
+    await db.commit()
+    resp = await client.post(
+        "/api/cleanup/audit",
+        json={"rule": "single_color", "params": {"threshold": 0.95, "tolerance": 30}},
+    )
+    assert resp.status_code == 409
+
+
+@pytest.mark.asyncio
+async def test_audit_get_by_id_returns_full_row(client, db):
+    audit = LibraryAuditRun(
+        rule="transparency", params={"threshold": 0.85},
+        status="ready", scanned_count=100, matched_count=3,
+        matched_ids=[1, 2, 3],
+    )
+    db.add(audit)
+    await db.commit()
+    resp = await client.get(f"/api/cleanup/audit/{audit.id}")
+    assert resp.status_code == 200
+    body = await resp.get_json()
+    assert body["rule"] == "transparency"
+    assert body["matched_count"] == 3
+    assert body["matched_ids"] == [1, 2, 3]
+
+
+@pytest.mark.asyncio
+async def test_audit_history_returns_recent_runs(client, db):
+    for _ in range(3):
+        db.add(LibraryAuditRun(
+            rule="transparency", params={"threshold": 0.9},
+            status="applied", matched_ids=[],
+            finished_at=datetime.now(UTC),
+        ))
+    await db.commit()
+    resp = await client.get("/api/cleanup/audit?limit=5")
+    assert resp.status_code == 200
+    body = await resp.get_json()
+    assert len(body["runs"]) >= 3
+
+
+@pytest.mark.asyncio
+async def test_audit_apply_with_token_deletes(client, db, tmp_path):
+    rec = await _seed_image(db, tmp_path, w=100, h=100, name="apply.png")
+    audit = LibraryAuditRun(
+        rule="transparency", params={"threshold": 0.9},
+        status="ready", scanned_count=1, matched_count=1,
+        matched_ids=[rec.id],
+    )
+    db.add(audit)
+    await db.commit()
+    resp = await client.post(
+        f"/api/cleanup/audit/{audit.id}/apply",
+        json={"confirm": f"delete-audit-{audit.id}"},
+    )
+    assert resp.status_code == 200
+    body = await resp.get_json()
+    assert body["deleted"] == 1
+
+
+@pytest.mark.asyncio
+async def test_audit_apply_with_bad_token_returns_400(client, db):
+    audit = LibraryAuditRun(
+        rule="transparency", params={"threshold": 0.9},
+        status="ready", matched_ids=[],
+    )
+    db.add(audit)
+    await db.commit()
+    resp = await client.post(
+        f"/api/cleanup/audit/{audit.id}/apply",
+        json={"confirm": "wrong-token"},
+    )
+    assert resp.status_code == 400
+    body = await resp.get_json()
+    assert body["error"] == "confirm_mismatch"
+
+
+@pytest.mark.asyncio
+async def test_audit_cancel_flips_status(client, db):
+    audit = LibraryAuditRun(
+        rule="transparency", params={"threshold": 0.9},
+        status="running", matched_ids=[],
+    )
+    db.add(audit)
+    await db.commit()
+    resp = await client.post(f"/api/cleanup/audit/{audit.id}/cancel")
+    assert resp.status_code == 200
+    new_status = await db.execute(
+        select(LibraryAuditRun.status).where(LibraryAuditRun.id == audit.id)
+    )
+    assert new_status.scalar_one() == "cancelled"
diff --git a/tests/test_cleanup_service_audit.py b/tests/test_cleanup_service_audit.py
index ec488d7..f9100b0 100644
--- a/tests/test_cleanup_service_audit.py
+++ b/tests/test_cleanup_service_audit.py
@@ -133,7 +133,7 @@ def test_apply_audit_run_with_correct_token_deletes_matched(db_sync, tmp_path):
 
     deleted = cleanup_service.apply_audit_run(
         db_sync, audit_id=audit.id,
-        confirm_token=f"apply-audit-{audit.id}",
+        confirm_token=f"delete-audit-{audit.id}",
         images_root=tmp_path,
     )
     assert deleted == 1
diff --git a/tests/test_importer_upsert_helpers.py b/tests/test_importer_upsert_helpers.py
new file mode 100644
index 0000000..ca8a3bc
--- /dev/null
+++ b/tests/test_importer_upsert_helpers.py
@@ -0,0 +1,147 @@
+"""Tests for Importer._find_or_create_source / _find_or_create_post —
+the race-safe savepoint-based helpers that replaced the previous
+check-then-insert pattern.
+
+Operator-flagged 2026-05-26: concurrent workers processing different
+files in the same post both found no existing Source row, then both
+INSERTed, tripping uq_source_artist_platform_url and poisoning the
+session with `psycopg.errors.UniqueViolation`. The new helpers wrap
+the INSERT in a savepoint and recover from IntegrityError by
+re-selecting the row that the concurrent op committed.
+
+Tests cover:
+  - idempotent return: same (artist_id, platform, url) → same Source row
+  - idempotent return for Post: same (source_id, external_post_id) → same Post
+  - IntegrityError recovery: monkeypatched flush raises once, helper
+    finds the row a concurrent op committed
+"""
+
+from pathlib import Path
+
+import pytest
+from sqlalchemy import select
+from sqlalchemy.exc import IntegrityError
+
+from backend.app.models import Artist, ImportSettings, Post, Source
+from backend.app.services.importer import Importer
+from backend.app.services.thumbnailer import Thumbnailer
+
+pytestmark = pytest.mark.integration
+
+
+@pytest.fixture
+def importer(db_sync, tmp_path):
+    import_root = tmp_path / "import"
+    images_root = tmp_path / "images"
+    import_root.mkdir()
+    images_root.mkdir()
+    settings = db_sync.execute(
+        select(ImportSettings).where(ImportSettings.id == 1)
+    ).scalar_one()
+    return Importer(
+        session=db_sync,
+        images_root=images_root,
+        import_root=import_root,
+        thumbnailer=Thumbnailer(images_root=images_root),
+        settings=settings,
+    )
+
+
+@pytest.fixture
+def artist_row(db_sync):
+    a = Artist(name="TestArtist", slug="testartist")
+    db_sync.add(a)
+    db_sync.flush()
+    return a
+
+
+def test_find_or_create_source_creates_then_returns_existing(importer, artist_row):
+    s1 = importer._find_or_create_source(
+        artist_id=artist_row.id, platform="patreon",
+        url="https://www.patreon.com/posts/test-1",
+    )
+    s2 = importer._find_or_create_source(
+        artist_id=artist_row.id, platform="patreon",
+        url="https://www.patreon.com/posts/test-1",
+    )
+    assert s1.id == s2.id
+
+
+def test_find_or_create_source_distinct_urls_yield_distinct_rows(
+    importer, artist_row,
+):
+    a = importer._find_or_create_source(
+        artist_id=artist_row.id, platform="patreon",
+        url="https://www.patreon.com/posts/a",
+    )
+    b = importer._find_or_create_source(
+        artist_id=artist_row.id, platform="patreon",
+        url="https://www.patreon.com/posts/b",
+    )
+    assert a.id != b.id
+
+
+def test_find_or_create_post_idempotent(importer, artist_row, db_sync):
+    src = importer._find_or_create_source(
+        artist_id=artist_row.id, platform="patreon",
+        url="https://www.patreon.com/posts/post-test",
+    )
+    p1 = importer._find_or_create_post(
+        source_id=src.id, external_post_id="ext-001",
+    )
+    p2 = importer._find_or_create_post(
+        source_id=src.id, external_post_id="ext-001",
+    )
+    assert p1.id == p2.id
+
+
+def test_find_or_create_source_recovers_from_integrity_error(
+    importer, artist_row, db_sync, monkeypatch,
+):
+    """Simulate the race: another worker has already inserted a Source row
+    matching our (artist_id, platform, url) just before our flush would
+    have. Our flush raises IntegrityError; the helper rolls back the
+    savepoint and re-selects, returning the row the concurrent op created.
+    """
+    canonical_url = "https://www.patreon.com/posts/race-141226276"
+    pre_existing = Source(
+        artist_id=artist_row.id, platform="patreon", url=canonical_url,
+    )
+    db_sync.add(pre_existing)
+    db_sync.flush()
+
+    # Force a fresh select within the helper to MISS the existing row by
+    # detaching it from the identity map; SQLAlchemy's first-level cache
+    # would otherwise return the pre_existing row immediately.
+    # Easier: monkeypatch the FIRST select inside the helper to return
+    # None on first call, real result on subsequent. We do that by
+    # patching session.execute with a single-shot wrapper.
+    real_execute = db_sync.execute
+    skip_count = [0]
+
+    def execute_with_first_select_miss(stmt, *args, **kwargs):
+        # Strip-down heuristic: the first SELECT issued by the helper is
+        # the existence check. Force it to return a "no row" result.
+        result = real_execute(stmt, *args, **kwargs)
+        if skip_count[0] == 0:
+            skip_count[0] += 1
+            # Wrap result so .scalar_one_or_none() returns None for this
+            # one call, then unwrap on subsequent uses.
+            class _ForcedMiss:
+                def scalar_one_or_none(self):
+                    return None
+
+                def scalar_one(self):
+                    return result.scalar_one()
+
+                def __getattr__(self, name):
+                    return getattr(result, name)
+            return _ForcedMiss()
+        return result
+
+    monkeypatch.setattr(db_sync, "execute", execute_with_first_select_miss)
+
+    recovered = importer._find_or_create_source(
+        artist_id=artist_row.id, platform="patreon", url=canonical_url,
+    )
+    assert recovered.id == pre_existing.id