feat(tagging): allowlist tuning dashboard + post-accept toast + merge preview UI (#7c/#7d/#8b)

Cluster B frontend, milestone #99.

#7c: AllowlistTable gains Applied + Covers columns and a live 'covers ~N at T'
projection as the operator drags a row's threshold (debounced coverage call,
then commits the threshold). allowlist store gains coverage(tagId, threshold)
and refreshes coverage_count after a save.

#7d: suggestions store surfaces a non-blocking toast when accept/alias newly
allowlists a tag — '<verb>: <tag> — allowlisted, auto-applying to ~N images'
(N is the projection; apply runs async). Falls back to the plain toast when
the tag was already allowlisted.

#8b: TagsView merge picker now previews the merge via usePreviewCommit before
committing — shows images moving / already-on-target / series pages / alias-or-
delete / a thumbnail sample, blocks the Merge button on an incompatible
kind/fandom. adminStore.mergeTags gains a dryRun option.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XCUHUGQLrBrkgyk1t49kpX

frontend/src/components/settings/AllowlistTable.vue

@@ -2,33 +2,60 @@
   <MaintenanceTile
     icon="mdi-playlist-check"
     :title="`Allowlisted tags (${store.rows.length})`"
-    blurb="Tags auto-applied to images that score above their threshold."
+    blurb="Tags auto-applied to images that score above their threshold. Tune the
+           threshold and see how many images it would cover."
   >
     <v-data-table-virtual
       :headers="headers" :items="store.rows" :loading="store.loading"
       height="360" density="compact"
       no-data-text="No tags on the allowlist yet — accept a suggestion to add one."
     >
-      <template #item.min_confidence="{ item }">
-        <v-text-field
-          :model-value="item.min_confidence" type="number"
-          density="compact" hide-details style="max-width: 100px;"
-          :min="floor" max="1" step="0.05"
-          @update:model-value="(v) => onThreshold(item.tag_id, v)"
-        />
+      <template #item.applied_count="{ item }">
+        <span class="fc-num">{{ item.applied_count ?? '—' }}</span>
       </template>
+
+      <template #item.min_confidence="{ item }">
+        <div class="fc-thr">
+          <v-text-field
+            :model-value="item.min_confidence" type="number"
+            density="compact" hide-details style="max-width: 100px;"
+            :min="floor" max="1" step="0.05"
+            :aria-label="`Auto-apply threshold for ${item.tag_name}`"
+            @update:model-value="(v) => onThreshold(item, v)"
+          />
+          <span
+            v-if="proj[item.tag_id]"
+            class="fc-thr__proj"
+            :class="{ 'fc-thr__proj--loading': proj[item.tag_id].loading }"
+            :title="`At ${proj[item.tag_id].threshold}, a sweep would cover this many images`"
+          >≈ {{ proj[item.tag_id].count }} at {{ proj[item.tag_id].threshold }}</span>
+        </div>
+      </template>
+
+      <template #item.coverage_count="{ item }">
+        <span class="fc-num" :title="`Images a sweep covers at ${item.min_confidence}`">
+          {{ item.coverage_count ?? '—' }}
+        </span>
+      </template>
+
       <template #item.actions="{ item }">
         <v-btn
           icon="mdi-delete" size="x-small" variant="text" color="error"
+          :aria-label="`Remove ${item.tag_name} from the allowlist`"
           @click="store.remove(item.tag_id)"
         />
       </template>
     </v-data-table-virtual>
+    <p class="fc-muted text-caption mt-2">
+      <strong>Applied</strong> = images currently carrying the tag.
+      <strong>Covers</strong> = images a sweep would auto-apply it to at the
+      current threshold. Lower the threshold to cover more (less certain) images.
+    </p>
   </MaintenanceTile>
 </template>
 
 <script setup>
-import { computed, onMounted } from 'vue'
+import { computed, onMounted, reactive } from 'vue'
 import { useAllowlistStore } from '../../stores/allowlist.js'
 import { useMLStore } from '../../stores/ml.js'
 import MaintenanceTile from '../common/MaintenanceTile.vue'
@@ -41,21 +68,53 @@ const ml = useMLStore()
 const floor = computed(() => ml.settings?.tagger_store_floor ?? 0.70)
 const headers = [
   { title: 'Tag', key: 'tag_name', sortable: true },
-  { title: 'Kind', key: 'tag_kind', sortable: true, width: 110 },
-  { title: 'Min confidence', key: 'min_confidence', sortable: false, width: 140 },
-  { title: '', key: 'actions', sortable: false, width: 60 }
+  { title: 'Kind', key: 'tag_kind', sortable: true, width: 100 },
+  { title: 'Applied', key: 'applied_count', sortable: true, width: 90 },
+  { title: 'Min confidence', key: 'min_confidence', sortable: false, width: 220 },
+  { title: 'Covers', key: 'coverage_count', sortable: true, width: 90 },
+  { title: '', key: 'actions', sortable: false, width: 56 }
 ]
+
+// Per-row live projection while the operator drags a threshold:
+//   proj[tagId] = { threshold, count, loading }
+const proj = reactive({})
+
 onMounted(() => {
   store.load()
   if (!ml.settings) ml.loadSettings()
 })
 
-let debounce = null
-function onThreshold(tagId, value) {
-  if (debounce) clearTimeout(debounce)
-  debounce = setTimeout(() => {
-    const v = Math.max(parseFloat(value), floor.value)
-    if (v > 0 && v <= 1) store.updateThreshold(tagId, v)
+const debounces = {}
+function onThreshold(item, value) {
+  const tagId = item.tag_id
+  const v = Math.max(parseFloat(value), floor.value)
+  if (!(v > 0 && v <= 1)) return
+  const shown = Number(v.toFixed(2))
+  // Optimistic live projection box (loading until the count returns).
+  proj[tagId] = { threshold: shown, count: proj[tagId]?.count ?? '…', loading: true }
+  if (debounces[tagId]) clearTimeout(debounces[tagId])
+  debounces[tagId] = setTimeout(async () => {
+    try {
+      const { count } = await store.coverage(tagId, v)
+      proj[tagId] = { threshold: shown, count, loading: false }
+    } catch {
+      delete proj[tagId]  // drop the projection rather than show a wrong number
+    }
+    // Commit the new threshold (also refreshes the row's stored coverage_count).
+    store.updateThreshold(tagId, v)
   }, 500)
 }
 </script>
+
+<style scoped>
+.fc-num { font-variant-numeric: tabular-nums; }
+.fc-thr { display: flex; align-items: center; gap: 10px; }
+.fc-thr__proj {
+  font-size: 12px;
+  font-variant-numeric: tabular-nums;
+  color: rgb(var(--v-theme-accent));
+  white-space: nowrap;
+}
+.fc-thr__proj--loading { color: rgb(var(--v-theme-on-surface-variant)); }
+.fc-muted { color: rgb(var(--v-theme-on-surface-variant)); }
+</style>

frontend/src/stores/admin.js

@@ -65,10 +65,11 @@ export const useAdminStore = defineStore('admin', () => {
     return _guard(() => api.delete(`/api/admin/tags/${tagId}`))
   }
 
-  function mergeTags(destId, sourceId) {
+  // dryRun → {preview: {...}} (non-mutating counts + sample); else {result}.
+  function mergeTags(destId, sourceId, { dryRun = false } = {}) {
     return _guard(() => api.post(
       `/api/admin/tags/${destId}/merge`,
-      { body: { source_id: sourceId } },
+      { body: { source_id: sourceId, dry_run: dryRun } },
     ))
   }
 

frontend/src/stores/allowlist.js

@@ -18,7 +18,21 @@ export const useAllowlistStore = defineStore('allowlist', () => {
       body: { min_confidence: minConfidence }
     })
     const r = rows.value.find(x => x.tag_id === tagId)
-    if (r) r.min_confidence = minConfidence
+    if (r) {
+      r.min_confidence = minConfidence
+      // The committed threshold changed the covered pool — refresh the row's
+      // coverage so the table stays truthful after a save.
+      try { r.coverage_count = (await coverage(tagId, minConfidence)).count }
+      catch { /* leave the stale count rather than blank it */ }
+    }
+  }
+
+  // Live "at threshold T, a sweep would cover ~N images" projection for the
+  // tuning dashboard. Returns { count, threshold }.
+  async function coverage(tagId, threshold) {
+    return api.get(`/api/tags/${tagId}/allowlist/coverage`, {
+      params: { threshold }
+    })
   }
 
   async function remove(tagId) {
@@ -26,5 +40,5 @@ export const useAllowlistStore = defineStore('allowlist', () => {
     rows.value = rows.value.filter(x => x.tag_id !== tagId)
   }
 
-  return { rows, loading, load, updateThreshold, remove }
+  return { rows, loading, load, updateThreshold, coverage, remove }
 })

frontend/src/stores/suggestions.js

@@ -100,7 +100,7 @@ export const useSuggestionsStore = defineStore('suggestions', () => {
       })
       tagId = created.id
     }
-    await api.post(`/api/images/${imageId}/suggestions/accept`, {
+    const res = await api.post(`/api/images/${imageId}/suggestions/accept`, {
       body: { tag_id: tagId }
     })
     // Only drop from THIS image's category list — if the user navigated,
@@ -108,10 +108,23 @@ export const useSuggestionsStore = defineStore('suggestions', () => {
     if (currentImageId === imageId) {
       _dropEverywhere(suggestion)
     }
-    toast({
-      text: `Tagged: ${suggestion.display_name}`,
-      type: 'success'
-    })
+    _acceptToast('Tagged', suggestion.display_name, res)
+  }
+
+  // One non-blocking toast for accept/alias. When the accept newly allowlisted
+  // the tag, surface the coverage PROJECTION (#7) so the operator sees the
+  // auto-apply reach without a blocking pre-accept preview — the apply itself
+  // runs async, hence "~N".
+  function _acceptToast(verb, displayName, res) {
+    if (res?.allowlisted) {
+      const n = res.projected_count
+      toast({
+        text: `${verb}: ${displayName} — allowlisted, auto-applying to ~${n} image${n === 1 ? '' : 's'}`,
+        type: 'success'
+      })
+    } else {
+      toast({ text: `${verb}: ${displayName}`, type: 'success' })
+    }
   }
 
   async function aliasAccept(suggestion, canonicalTagId) {
@@ -123,7 +136,7 @@ export const useSuggestionsStore = defineStore('suggestions', () => {
     // reappearing unaliased. raw_name is null only for centroid hits, which
     // can't be aliased (the UI hides the action for them).
     const aliasString = suggestion.raw_name ?? suggestion.display_name
-    await api.post(`/api/images/${imageId}/suggestions/alias`, {
+    const res = await api.post(`/api/images/${imageId}/suggestions/alias`, {
       body: {
         alias_string: aliasString,
         alias_category: suggestion.category,
@@ -133,10 +146,7 @@ export const useSuggestionsStore = defineStore('suggestions', () => {
     if (currentImageId === imageId) {
       _dropEverywhere(suggestion)
     }
-    toast({
-      text: `Aliased & tagged: ${suggestion.display_name}`,
-      type: 'success'
-    })
+    _acceptToast('Aliased & tagged', suggestion.display_name, res)
   }
 
   // Remove the alias behind an aliased suggestion (the raw prediction reverts to

frontend/src/views/TagsView.vue

@@ -45,10 +45,9 @@
       <v-card>
         <v-card-title>Merge “{{ mergeSource?.name }}” into…</v-card-title>
         <v-card-text>
-          <p class="text-body-2 mb-3" style="opacity: 0.7;">
-            Pick the target tag. Source tag will be deleted; all its
-            image associations will move to the target. Must be same
-            kind ({{ mergeSource?.kind }}).
+          <p class="fc-muted text-body-2 mb-3">
+            Pick the target tag. Source tag's image associations move to the
+            target. Must be same kind ({{ mergeSource?.kind }}).
           </p>
           <v-autocomplete
             v-model="mergeTargetId"
@@ -60,15 +59,59 @@
             @update:search="onMergeSearch"
             @keydown.enter.capture="onMergeEnter"
           />
+
+          <v-alert
+            v-if="adminStore.lastError"
+            type="warning" variant="tonal" density="compact" class="mt-3"
+          >{{ adminStore.lastError }}</v-alert>
+
+          <!-- #8: dry-run preview of what the merge will move, before commit. -->
+          <div v-if="mergeTargetId" class="fc-merge-preview mt-3">
+            <div v-if="mergePreviewing" class="d-flex align-center ga-2">
+              <v-progress-circular indeterminate size="18" width="2" color="accent" />
+              <span class="text-body-2 fc-muted">Checking what would move…</span>
+            </div>
+            <div v-else-if="mergePreview">
+              <p class="text-body-2 mb-1">
+                Moves <strong>{{ mergePreview.images_moving }}</strong>
+                image(s) onto <strong>{{ mergePreview.target_name }}</strong>.
+                <span v-if="mergePreview.images_already_on_target" class="fc-muted">
+                  ({{ mergePreview.images_already_on_target }} already on it.)
+                </span>
+              </p>
+              <p v-if="mergePreview.series_pages" class="text-body-2 mb-1">
+                {{ mergePreview.series_pages }} series page(s) repointed.
+              </p>
+              <p class="text-body-2 mb-1">
+                <template v-if="mergePreview.will_alias">
+                  “{{ mergePreview.source_name }}” kept as an alias — the tagger may still predict it.
+                </template>
+                <template v-else>
+                  “{{ mergePreview.source_name }}” will be permanently deleted.
+                </template>
+              </p>
+              <v-alert
+                v-if="!mergePreview.compatible"
+                type="error" variant="tonal" density="compact" class="mb-2"
+              >Different kind or fandom — this merge would be rejected.</v-alert>
+              <div v-if="mergePreview.sample_thumbnails?.length" class="fc-merge-thumbs">
+                <img
+                  v-for="(t, i) in mergePreview.sample_thumbnails" :key="i"
+                  :src="t" alt="" loading="lazy"
+                />
+              </div>
+            </div>
+          </div>
         </v-card-text>
         <v-card-actions>
           <v-spacer />
           <v-btn variant="text" @click="mergePickerOpen = false">Cancel</v-btn>
           <v-btn
             color="warning" variant="flat" rounded="pill"
-            :disabled="!mergeTargetId"
+            :disabled="!mergePreview || !mergePreview.compatible"
+            :loading="merging"
             @click="onMergeConfirm"
-          >Merge</v-btn>
+          >Merge{{ mergePreview ? ` ${mergePreview.images_moving} image(s)` : '' }}</v-btn>
         </v-card-actions>
       </v-card>
     </v-dialog>
@@ -114,6 +157,7 @@ import { useAdminStore } from '../stores/admin.js'
 import { useApi } from '../composables/useApi.js'
 import { useInfiniteScroll } from '../composables/useInfiniteScroll.js'
 import { useAcceptOnEnter } from '../composables/useAcceptOnEnter.js'
+import { usePreviewCommit } from '../composables/usePreviewCommit.js'
 import TagCard from '../components/discovery/TagCard.vue'
 import MergeConfirmDialog from '../components/discovery/MergeConfirmDialog.vue'
 import DestructiveConfirmModal from '../components/modal/DestructiveConfirmModal.vue'
@@ -207,10 +251,32 @@ const mergeHits = ref([])
 const mergeLoading = ref(false)
 let mergeDebounce = null
 
+// #8: dry-run preview (counts + sample of what moves) before the irreversible
+// merge — same usePreviewCommit primitive the maintenance tiles use.
+const {
+  previewData: mergePreview, previewing: mergePreviewing, committing: merging,
+  runPreview: runMergePreview, runCommit: runMergeCommit,
+} = usePreviewCommit({
+  preview: async () =>
+    (await adminStore.mergeTags(
+      mergeTargetId.value, mergeSource.value.id, { dryRun: true },
+    )).preview,
+  commit: () => adminStore.mergeTags(
+    mergeTargetId.value, mergeSource.value.id, { dryRun: false },
+  ),
+})
+
+// Re-preview whenever the chosen target changes (and clear it when unset).
+watch(mergeTargetId, (id) => {
+  if (id && mergeSource.value) runMergePreview()
+  else mergePreview.value = null
+})
+
 function onMergeWith(card) {
   mergeSource.value = card
   mergeTargetId.value = null
   mergeHits.value = []
+  mergePreview.value = null
   mergePickerOpen.value = true
 }
 
@@ -234,8 +300,9 @@ function onMergeSearch(q) {
 
 async function onMergeConfirm() {
   if (!mergeSource.value || !mergeTargetId.value) return
+  if (!mergePreview.value || !mergePreview.value.compatible) return
   try {
-    await adminStore.mergeTags(mergeTargetId.value, mergeSource.value.id)
+    await runMergeCommit()
     mergePickerOpen.value = false
     store.reset()
   } catch {
@@ -282,4 +349,18 @@ async function onDeleteTagConfirm() {
 .fc-tags__sentinel {
   display: flex; justify-content: center; padding: 32px 0; min-height: 60px;
 }
+.fc-muted { color: rgb(var(--v-theme-on-surface-variant)); }
+.fc-merge-preview {
+  padding: 10px 12px;
+  border: 1px solid rgba(var(--v-theme-on-surface), 0.12);
+  border-radius: 10px;
+  background: rgba(var(--v-theme-on-surface), 0.03);
+}
+.fc-merge-thumbs {
+  display: flex; gap: 4px; flex-wrap: wrap; margin-top: 6px;
+}
+.fc-merge-thumbs img {
+  width: 56px; height: 56px; object-fit: cover; border-radius: 6px;
+  background: rgb(var(--v-theme-surface-light));
+}
 </style>