diff --git a/frontend/src/stores/admin.js b/frontend/src/stores/admin.js
index 3b05893..86cd059 100644
--- a/frontend/src/stores/admin.js
+++ b/frontend/src/stores/admin.js
@@ -7,186 +7,114 @@ export const useAdminStore = defineStore('admin', () => {
   const api = useApi()
   const lastError = ref(null)
 
-  // --- Tier-C: artist cascade ---------------------------------------
-
-  async function projectArtistCascade(slug) {
+  // Every admin action runs through _guard: reset lastError, run the call,
+  // surface its message to lastError on failure, and re-throw so callers still
+  // see the rejection. One copy of the capture/rethrow instead of 13.
+  async function _guard(fn) {
     lastError.value = null
     try {
-      return await api.post(
-        `/api/admin/artists/${encodeURIComponent(slug)}/cascade-delete`,
-        { body: { dry_run: true } },
-      )
+      return await fn()
     } catch (e) {
       lastError.value = e.message
       throw e
     }
   }
 
-  async function dispatchArtistCascade(slug, confirm) {
-    lastError.value = null
-    try {
-      return await api.post(
-        `/api/admin/artists/${encodeURIComponent(slug)}/cascade-delete`,
-        { body: { dry_run: false, confirm } },
-      )
-    } catch (e) {
-      lastError.value = e.message
-      throw e
-    }
+  // The Tier-A maintenance endpoints share one shape: POST a dry_run flag
+  // (default the SAFE preview), optionally with extra body fields. The backend's
+  // same predicate drives preview + apply, so the UI just toggles dryRun.
+  function _dryRunPost(url, { dryRun = true, ...extra } = {}) {
+    return _guard(() => api.post(url, { body: { dry_run: dryRun, ...extra } }))
+  }
+
+  // --- Tier-C: artist cascade ---------------------------------------
+
+  function projectArtistCascade(slug) {
+    return _guard(() => api.post(
+      `/api/admin/artists/${encodeURIComponent(slug)}/cascade-delete`,
+      { body: { dry_run: true } },
+    ))
+  }
+
+  function dispatchArtistCascade(slug, confirm) {
+    return _guard(() => api.post(
+      `/api/admin/artists/${encodeURIComponent(slug)}/cascade-delete`,
+      { body: { dry_run: false, confirm } },
+    ))
   }
 
   // --- Tier-C: bulk image delete ------------------------------------
 
-  async function projectBulkImageDelete(imageIds) {
-    lastError.value = null
-    try {
-      return await api.post(
-        '/api/admin/images/bulk-delete',
-        { body: { image_ids: imageIds, dry_run: true } },
-      )
-    } catch (e) {
-      lastError.value = e.message
-      throw e
-    }
+  function projectBulkImageDelete(imageIds) {
+    return _guard(() => api.post(
+      '/api/admin/images/bulk-delete',
+      { body: { image_ids: imageIds, dry_run: true } },
+    ))
   }
 
-  async function dispatchBulkImageDelete(imageIds, confirm) {
-    lastError.value = null
-    try {
-      return await api.post(
-        '/api/admin/images/bulk-delete',
-        { body: { image_ids: imageIds, dry_run: false, confirm } },
-      )
-    } catch (e) {
-      lastError.value = e.message
-      throw e
-    }
+  function dispatchBulkImageDelete(imageIds, confirm) {
+    return _guard(() => api.post(
+      '/api/admin/images/bulk-delete',
+      { body: { image_ids: imageIds, dry_run: false, confirm } },
+    ))
   }
 
   // --- Tier-B: tag delete + merge -----------------------------------
 
-  async function deleteTag(tagId) {
-    lastError.value = null
-    try {
-      return await api.delete(`/api/admin/tags/${tagId}`)
-    } catch (e) {
-      lastError.value = e.message
-      throw e
-    }
+  function deleteTag(tagId) {
+    return _guard(() => api.delete(`/api/admin/tags/${tagId}`))
   }
 
-  async function mergeTags(destId, sourceId) {
-    lastError.value = null
-    try {
-      return await api.post(
-        `/api/admin/tags/${destId}/merge`,
-        { body: { source_id: sourceId } },
-      )
-    } catch (e) {
-      lastError.value = e.message
-      throw e
-    }
+  function mergeTags(destId, sourceId) {
+    return _guard(() => api.post(
+      `/api/admin/tags/${destId}/merge`,
+      { body: { source_id: sourceId } },
+    ))
   }
 
   async function tagUsageCount(tagId) {
-    lastError.value = null
-    try {
+    return _guard(async () => {
       const body = await api.get(`/api/admin/tags/${tagId}/usage-count`)
       return body.count
-    } catch (e) {
-      lastError.value = e.message
-      throw e
-    }
+    })
   }
 
-  // --- Tier-A: prune unused -----------------------------------------
+  // --- Tier-A: dry-run/apply maintenance ----------------------------
 
-  async function pruneUnusedTags({ dryRun = true } = {}) {
-    lastError.value = null
-    try {
-      return await api.post(
-        '/api/admin/tags/prune-unused',
-        { body: { dry_run: dryRun } },
-      )
-    } catch (e) {
-      lastError.value = e.message
-      throw e
-    }
+  function pruneUnusedTags(opts = {}) {
+    return _dryRunPost('/api/admin/tags/prune-unused', opts)
   }
 
-  // Tier-A: delete bare posts (no images + no attachments) — the empty-post
-  // flood shells. Preview/apply parity on the backend; UI previews then confirms.
-  async function pruneBarePosts({ dryRun = true } = {}) {
-    lastError.value = null
-    try {
-      return await api.post(
-        '/api/admin/posts/prune-bare',
-        { body: { dry_run: dryRun } },
-      )
-    } catch (e) {
-      lastError.value = e.message
-      throw e
-    }
+  // Delete bare posts (no images + no attachments) — the empty-post flood
+  // shells. Preview/apply parity on the backend; UI previews then confirms.
+  function pruneBarePosts(opts = {}) {
+    return _dryRunPost('/api/admin/posts/prune-bare', opts)
   }
 
-  // Tier-A: unify duplicate post rows (gallery-dl attachment-id + native post-id
-  // for the same real post) onto one post-id-keyed keeper. Images untouched.
-  // Preview/apply parity on the backend; UI previews then confirms.
-  async function reconcileDuplicatePosts({ dryRun = true, sourceId = null } = {}) {
-    lastError.value = null
-    try {
-      return await api.post(
-        '/api/admin/posts/reconcile-duplicates',
-        { body: { dry_run: dryRun, source_id: sourceId } },
-      )
-    } catch (e) {
-      lastError.value = e.message
-      throw e
-    }
+  // Unify duplicate post rows (gallery-dl attachment-id + native post-id for the
+  // same real post) onto one post-id-keyed keeper. Images untouched. sourceId
+  // (optional) scopes to one source; sent as source_id in the body.
+  function reconcileDuplicatePosts({ sourceId = null, ...opts } = {}) {
+    return _dryRunPost('/api/admin/posts/reconcile-duplicates', {
+      ...opts, source_id: sourceId,
+    })
   }
 
-  async function purgeLegacyTags({ dryRun = true } = {}) {
-    lastError.value = null
-    try {
-      return await api.post(
-        '/api/admin/tags/purge-legacy',
-        { body: { dry_run: dryRun } },
-      )
-    } catch (e) {
-      lastError.value = e.message
-      throw e
-    }
+  function purgeLegacyTags(opts = {}) {
+    return _dryRunPost('/api/admin/tags/purge-legacy', opts)
   }
 
   // Destructive: deletes ALL general + character tags so the operator can
   // re-tag from scratch via auto-suggest. fandom + series preserved.
-  async function resetContentTagging({ dryRun = true } = {}) {
-    lastError.value = null
-    try {
-      return await api.post(
-        '/api/admin/tags/reset-content',
-        { body: { dry_run: dryRun } },
-      )
-    } catch (e) {
-      lastError.value = e.message
-      throw e
-    }
+  function resetContentTagging(opts = {}) {
+    return _dryRunPost('/api/admin/tags/reset-content', opts)
   }
 
   // #714: Title-Case the back-catalog + merge case/whitespace-variant tags.
   // dry-run returns a projection inline; live returns {task_id} (long op —
   // FK repoints) the caller polls via pollTaskUntilDone.
-  async function normalizeTags({ dryRun = true } = {}) {
-    lastError.value = null
-    try {
-      return await api.post(
-        '/api/admin/tags/normalize',
-        { body: { dry_run: dryRun } },
-      )
-    } catch (e) {
-      lastError.value = e.message
-      throw e
-    }
+  function normalizeTags(opts = {}) {
+    return _dryRunPost('/api/admin/tags/normalize', opts)
   }
 
   // --- Task progress polling (taps FC-3i activity dashboard) --------
diff --git a/frontend/test/adminStore.spec.js b/frontend/test/adminStore.spec.js
new file mode 100644
index 0000000..2dcbce8
--- /dev/null
+++ b/frontend/test/adminStore.spec.js
@@ -0,0 +1,85 @@
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest'
+import { setActivePinia, createPinia } from 'pinia'
+import { useAdminStore } from '../src/stores/admin.js'
+
+// Covers the two helpers the admin store actions route through (DRY Finding C,
+// #753): _dryRunPost (URL + dry_run body, sourceId→source_id) and _guard
+// (lastError capture + rethrow). The store had no frontend test before.
+
+function stubFetch(handler) {
+  globalThis.fetch = vi.fn(async (url, init) => {
+    const { status, body } = handler(url, init)
+    return {
+      ok: status >= 200 && status < 300,
+      status,
+      statusText: String(status),
+      text: async () => (body == null ? '' : JSON.stringify(body)),
+    }
+  })
+}
+
+function lastCallBody(calls) {
+  return JSON.parse(calls.at(-1).init.body)
+}
+
+describe('admin store', () => {
+  beforeEach(() => setActivePinia(createPinia()))
+  afterEach(() => vi.restoreAllMocks())
+
+  it('_dryRunPost sends the apply flag to the right endpoint', async () => {
+    const s = useAdminStore()
+    const calls = []
+    stubFetch((url, init) => {
+      calls.push({ url, init })
+      return { status: 200, body: { deleted: 0 } }
+    })
+    await s.pruneUnusedTags({ dryRun: false })
+    const c = calls.at(-1)
+    expect(c.url).toContain('/api/admin/tags/prune-unused')
+    expect(c.init.method).toBe('POST')
+    expect(lastCallBody(calls)).toEqual({ dry_run: false })
+  })
+
+  it('_dryRunPost defaults to the safe preview', async () => {
+    const s = useAdminStore()
+    const calls = []
+    stubFetch((url, init) => {
+      calls.push({ url, init })
+      return { status: 200, body: { count: 0 } }
+    })
+    await s.pruneBarePosts()
+    expect(lastCallBody(calls)).toEqual({ dry_run: true })
+  })
+
+  it('reconcileDuplicatePosts maps sourceId → source_id', async () => {
+    const s = useAdminStore()
+    const calls = []
+    stubFetch((url, init) => {
+      calls.push({ url, init })
+      return { status: 200, body: { groups: 0 } }
+    })
+    await s.reconcileDuplicatePosts({ dryRun: false, sourceId: 42 })
+    const c = calls.at(-1)
+    expect(c.url).toContain('/api/admin/posts/reconcile-duplicates')
+    expect(lastCallBody(calls)).toEqual({ dry_run: false, source_id: 42 })
+  })
+
+  it('_guard captures the error message on lastError and rethrows', async () => {
+    const s = useAdminStore()
+    stubFetch(() => ({ status: 500, body: { error: 'boom' } }))
+    await expect(s.deleteTag(7)).rejects.toThrow('boom')
+    expect(s.lastError).toBe('boom')
+  })
+
+  it('_guard clears lastError on a subsequent success', async () => {
+    const s = useAdminStore()
+    stubFetch(() => ({ status: 500, body: { error: 'boom' } }))
+    await expect(s.deleteTag(7)).rejects.toThrow()
+    expect(s.lastError).toBe('boom')
+
+    stubFetch(() => ({ status: 200, body: { count: 3 } }))
+    const n = await s.tagUsageCount(7)
+    expect(n).toBe(3)  // tagUsageCount returns body.count, not the raw body
+    expect(s.lastError).toBe(null)
+  })
+})