diff --git a/frontend/src/stores/seriesManage.js b/frontend/src/stores/seriesManage.js
new file mode 100644
index 0000000..17f84ee
--- /dev/null
+++ b/frontend/src/stores/seriesManage.js
@@ -0,0 +1,91 @@
+import { defineStore } from 'pinia'
+import { ref } from 'vue'
+import { useApi } from '../composables/useApi.js'
+
+// Pure, unit-tested: move arr[from] to index `to`, returning a new array.
+export function moveItem(arr, from, to) {
+  const next = arr.slice()
+  const [x] = next.splice(from, 1)
+  next.splice(to, 0, x)
+  return next
+}
+
+export const useSeriesManageStore = defineStore('seriesManage', () => {
+  const api = useApi()
+
+  const tagId = ref(null)
+  const series = ref(null)
+  const pages = ref([])              // [{image_id, page_number, thumbnail_url}]
+  const picker = ref([])             // gallery scroll results
+  const pickerCursor = ref(null)
+  const pickerSelection = ref([])    // image ids
+  const loading = ref(false)
+
+  async function load(id) {
+    tagId.value = id
+    loading.value = true
+    try {
+      const body = await api.get(`/api/series/${id}/pages`)
+      series.value = body.series
+      pages.value = body.pages
+    } finally {
+      loading.value = false
+    }
+  }
+
+  async function refresh() {
+    if (tagId.value != null) await load(tagId.value)
+  }
+
+  async function loadPicker(reset = false) {
+    if (reset) { picker.value = []; pickerCursor.value = null }
+    const params = { limit: 50 }
+    if (pickerCursor.value) params.cursor = pickerCursor.value
+    const body = await api.get('/api/gallery/scroll', { params })
+    picker.value.push(...body.images)
+    pickerCursor.value = body.next_cursor
+  }
+
+  function togglePick(imageId) {
+    const i = pickerSelection.value.indexOf(imageId)
+    if (i === -1) pickerSelection.value.push(imageId)
+    else pickerSelection.value.splice(i, 1)
+  }
+
+  async function addSelected() {
+    if (pickerSelection.value.length === 0) return
+    await api.post(`/api/series/${tagId.value}/pages`, {
+      body: { image_ids: pickerSelection.value }
+    })
+    pickerSelection.value = []
+    await refresh()
+    globalThis.window?.__fcToast?.({ text: 'Added to series', type: 'success' })
+  }
+
+  async function remove(imageId) {
+    await api.post(`/api/series/${tagId.value}/pages/remove`, {
+      body: { image_ids: [imageId] }
+    })
+    await refresh()
+  }
+
+  async function reorder(orderedImageIds) {
+    await api.post(`/api/series/${tagId.value}/reorder`, {
+      body: { image_ids: orderedImageIds }
+    })
+    await refresh()
+  }
+
+  async function setCover(imageId) {
+    await api.post(`/api/series/${tagId.value}/cover`, {
+      body: { image_id: imageId }
+    })
+    await refresh()
+  }
+
+  return {
+    tagId, series, pages, picker, pickerCursor, pickerSelection, loading,
+    load, refresh, loadPicker, togglePick, addSelected, remove,
+    reorder, setCover
+  }
+})
diff --git a/frontend/test/seriesManage.spec.js b/frontend/test/seriesManage.spec.js
new file mode 100644
index 0000000..3076d6a
--- /dev/null
+++ b/frontend/test/seriesManage.spec.js
@@ -0,0 +1,69 @@
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest'
+import { setActivePinia, createPinia } from 'pinia'
+import { useSeriesManageStore, moveItem } from '../src/stores/seriesManage.js'
+
+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))
+    }
+  })
+}
+
+describe('seriesManage', () => {
+  beforeEach(() => setActivePinia(createPinia()))
+  afterEach(() => vi.restoreAllMocks())
+
+  it('moveItem reorders immutably', () => {
+    expect(moveItem([1, 2, 3, 4], 3, 0)).toEqual([4, 1, 2, 3])
+    expect(moveItem([1, 2, 3], 0, 2)).toEqual([2, 3, 1])
+  })
+
+  it('load fetches pages + series', async () => {
+    const s = useSeriesManageStore()
+    stubFetch(() => ({
+      status: 200,
+      body: { series: { id: 7, name: 'V' },
+              pages: [{ image_id: 1, page_number: 1, thumbnail_url: 't' }] }
+    }))
+    await s.load(7)
+    expect(s.series).toEqual({ id: 7, name: 'V' })
+    expect(s.pages.map(p => p.image_id)).toEqual([1])
+  })
+
+  it('reorder posts the full ordered id list', async () => {
+    const s = useSeriesManageStore()
+    s.tagId = 7
+    s.pages = [{ image_id: 1 }, { image_id: 2 }, { image_id: 3 }]
+    const calls = []
+    stubFetch((url, init) => {
+      calls.push({ url, body: JSON.parse(init.body) })
+      if (url.includes('/reorder')) return { status: 200, body: { ok: true } }
+      return { status: 200, body: { series: { id: 7, name: 'V' }, pages: [] } }
+    })
+    await s.reorder([3, 1, 2])
+    const r = calls.find(c => c.url.includes('/reorder'))
+    expect(r.url).toContain('/api/series/7/reorder')
+    expect(r.body).toEqual({ image_ids: [3, 1, 2] })
+  })
+
+  it('addSelected posts picker selection then reloads', async () => {
+    const s = useSeriesManageStore()
+    s.tagId = 7
+    s.pickerSelection = [9, 10]
+    const calls = []
+    stubFetch((url, init) => {
+      calls.push({ url, body: init.body ? JSON.parse(init.body) : null })
+      if (url.includes('/pages') && init.method === 'POST')
+        return { status: 200, body: { added_count: 2 } }
+      return { status: 200, body: { series: { id: 7, name: 'V' }, pages: [] } }
+    })
+    await s.addSelected()
+    const add = calls.find(c => c.url.endsWith('/api/series/7/pages'))
+    expect(add.body).toEqual({ image_ids: [9, 10] })
+    expect(s.pickerSelection).toEqual([])
+  })
+})