diff --git a/.gitignore b/.gitignore
index 10d4d4b..c726541 100644
--- a/.gitignore
+++ b/.gitignore
@@ -69,3 +69,4 @@ Thumbs.db
 alembic/versions/__pycache__/
 *.sqlite
 *.sqlite-journal
+.superpowers/
diff --git a/alembic/env.py b/alembic/env.py
index 0530946..b657465 100644
--- a/alembic/env.py
+++ b/alembic/env.py
@@ -2,12 +2,21 @@
 
 from logging.config import fileConfig
 
-from sqlalchemy import engine_from_config, pool
+from sqlalchemy import engine_from_config, pool, text
 
 from alembic import context
 from backend.app.config import get_config
 from backend.app.models import Base
 
+# Arbitrary fixed 64-bit key for the session/transaction advisory lock that
+# serializes concurrent `alembic upgrade head` runs. Every `web` replica runs
+# migrations in its entrypoint, so under `docker stack deploy` two replicas can
+# boot at once and race the same DDL — duplicate CREATE TABLE, then a crashed
+# replica (operator-flagged 2026-06-07: 0040 raced; one backend died with
+# AdminShutdown). The first replica to reach the lock migrates; the rest block,
+# then find the version table already at head and apply nothing.
+_MIGRATION_LOCK_KEY = 0xFCA1E35C
+
 config = context.config
 
 if config.config_file_name is not None:
@@ -44,6 +53,18 @@ def run_migrations_online() -> None:
             compare_type=True,
         )
         with context.begin_transaction():
+            # Serialize concurrent migrators (see _MIGRATION_LOCK_KEY). A
+            # transaction-scoped advisory lock: the first replica to get here
+            # holds it for the whole upgrade and is auto-released when this
+            # transaction ends. A sibling replica blocks on this line, and only
+            # once the leader commits does it proceed to read the version table
+            # — now at head — so it runs zero migrations instead of re-applying
+            # the same DDL. The lock is acquired BEFORE run_migrations() reads
+            # the current revision, which is what makes the no-op correct.
+            connection.execute(
+                text("SELECT pg_advisory_xact_lock(:k)"),
+                {"k": _MIGRATION_LOCK_KEY},
+            )
             context.run_migrations()
 
 
diff --git a/alembic/versions/0042_series_chapter_stated_part.py b/alembic/versions/0042_series_chapter_stated_part.py
new file mode 100644
index 0000000..f898e56
--- /dev/null
+++ b/alembic/versions/0042_series_chapter_stated_part.py
@@ -0,0 +1,32 @@
+"""series chapter stated_part: operator-facing Part N label (FC-6.4)
+
+Revision ID: 0042
+Revises: 0041
+Create Date: 2026-06-07
+
+A chapter's positional chapter_number is auto-managed (rewritten 1..N on
+reorder/delete), so it can't double as the installment number the operator wants
+to type (e.g. a series authored from a post that is Part 2). Add a nullable
+stated_part alongside it — the same split as series_page.page_number (order) vs
+series_page.stated_page (printed number). Nullable; the UI falls back to
+chapter_number when unset.
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "0042"
+down_revision: Union[str, None] = "0041"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "series_chapter", sa.Column("stated_part", sa.Integer, nullable=True)
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("series_chapter", "stated_part")
diff --git a/backend/app/api/tags.py b/backend/app/api/tags.py
index 918fa42..59dc286 100644
--- a/backend/app/api/tags.py
+++ b/backend/app/api/tags.py
@@ -528,6 +528,11 @@ async def series_chapter_update(tag_id: int, chapter_id: int):
         if body["title"] is not None and not isinstance(body["title"], str):
             return jsonify({"error": "title must be a string"}), 400
         kwargs.update(set_title=True, title=body["title"])
+    if "stated_part" in body:
+        part, perr = _opt_int(body, "stated_part")
+        if perr:
+            return perr
+        kwargs.update(set_part=True, stated_part=part)
     if "stated_page_start" in body:
         start, serr = _opt_int(body, "stated_page_start")
         if serr:
diff --git a/backend/app/models/series_chapter.py b/backend/app/models/series_chapter.py
index 4012174..9695272 100644
--- a/backend/app/models/series_chapter.py
+++ b/backend/app/models/series_chapter.py
@@ -12,6 +12,12 @@ A chapter may be a placeholder (is_placeholder=True) — a reserved empty slot f
 a section the operator doesn't have yet; it holds no pages and shows as a gap in
 the reader. stated_page_start/end carry the page range parsed from the source
 post (FC-6.2), used to flag missing-page gaps; both are nullable when unknown.
+
+stated_part is the operator-facing "Part N" label (FC-6.4), separate from the
+positional chapter_number: chapter_number is auto-managed ordering (rewritten
+1..N on reorder/delete), while stated_part is the real installment number the
+operator types — e.g. a series authored from a post that is Part 2 of a story.
+Nullable when unset (the UI then falls back to showing chapter_number).
 """
 
 from datetime import datetime
@@ -30,6 +36,7 @@ class SeriesChapter(Base):
         ForeignKey("tag.id", ondelete="CASCADE"), nullable=False, index=True
     )
     chapter_number: Mapped[int] = mapped_column(Integer, nullable=False)
+    stated_part: Mapped[int | None] = mapped_column(Integer, nullable=True)
     title: Mapped[str | None] = mapped_column(Text, nullable=True)
     is_placeholder: Mapped[bool] = mapped_column(
         Boolean, nullable=False, server_default="false"
diff --git a/backend/app/models/tag_allowlist.py b/backend/app/models/tag_allowlist.py
index 75bd0f2..3bbbc7a 100644
--- a/backend/app/models/tag_allowlist.py
+++ b/backend/app/models/tag_allowlist.py
@@ -22,7 +22,11 @@ class TagAllowlist(Base):
     tag_id: Mapped[int] = mapped_column(
         ForeignKey("tag.id", ondelete="CASCADE"), primary_key=True
     )
-    min_confidence: Mapped[float] = mapped_column(Float, nullable=False, default=0.95)
+    # Default auto-apply threshold for a newly-accepted tag. 0.90 (lowered from
+    # 0.95 on operator evidence 2026-06-07: 0.95 was too strict and skipped
+    # confident-enough applications). Per-tag value is still tunable in the
+    # allowlist table; existing rows keep whatever they were stored with.
+    min_confidence: Mapped[float] = mapped_column(Float, nullable=False, default=0.90)
     added_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), nullable=False, server_default=func.now()
     )
diff --git a/backend/app/services/series_service.py b/backend/app/services/series_service.py
index 7c943a1..9fbb634 100644
--- a/backend/app/services/series_service.py
+++ b/backend/app/services/series_service.py
@@ -131,6 +131,29 @@ class SeriesService:
             prev = ch
         return out
 
+    @staticmethod
+    def _part_gaps(chapters: list[dict]) -> list[dict]:
+        """Missing-Part gaps between consecutive chapters whose stated_part
+        numbers jump by more than 1 (e.g. a series with Part 1 and Part 3, or one
+        authored straight from a Part 2 post). Mirrors _gaps but on stated_part —
+        only chapters that actually carry a stated_part participate."""
+        out: list[dict] = []
+        prev = None
+        for ch in chapters:
+            cur = ch["stated_part"]
+            if cur is None:
+                continue
+            if prev is not None and cur > prev["stated_part"] + 1:
+                out.append(
+                    {
+                        "after_chapter_id": prev["id"],
+                        "start": prev["stated_part"] + 1,
+                        "end": cur - 1,
+                    }
+                )
+            prev = ch
+        return out
+
     async def list_pages(self, series_tag_id: int) -> dict:
         tag = await self._require_series(series_tag_id)
         rows = (
@@ -138,6 +161,7 @@ class SeriesService:
                 select(
                     SeriesChapter.id.label("chapter_id"),
                     SeriesChapter.chapter_number,
+                    SeriesChapter.stated_part,
                     SeriesChapter.title,
                     SeriesChapter.is_placeholder,
                     SeriesChapter.stated_page_start,
@@ -149,10 +173,13 @@ class SeriesService:
                     ImageRecord.mime,
                     ImageRecord.path,
                     ImageRecord.thumbnail_path,
+                    ImageRecord.primary_post_id,
+                    Post.post_title,
                 )
                 .select_from(SeriesChapter)
                 .outerjoin(SeriesPage, SeriesPage.chapter_id == SeriesChapter.id)
                 .outerjoin(ImageRecord, ImageRecord.id == SeriesPage.image_id)
+                .outerjoin(Post, Post.id == ImageRecord.primary_post_id)
                 .where(SeriesChapter.series_tag_id == series_tag_id)
                 .order_by(
                     SeriesChapter.chapter_number.asc(),
@@ -164,22 +191,30 @@ class SeriesService:
         chapters: list[dict] = []
         flat: list[dict] = []
         by_id: dict[int, dict] = {}
+        # chapter_id -> {post_id: title} seen across its pages, so we can label a
+        # chapter with its source post when all its pages come from one post.
+        posts_seen: dict[int, dict[int, str | None]] = {}
         for r in rows:
             ch = by_id.get(r.chapter_id)
             if ch is None:
                 ch = {
                     "id": r.chapter_id,
                     "chapter_number": r.chapter_number,
+                    "stated_part": r.stated_part,
                     "title": r.title,
                     "is_placeholder": r.is_placeholder,
                     "stated_page_start": r.stated_page_start,
                     "stated_page_end": r.stated_page_end,
+                    "source_post": None,
                     "pages": [],
                 }
                 by_id[r.chapter_id] = ch
+                posts_seen[r.chapter_id] = {}
                 chapters.append(ch)
             if r.image_id is None:
                 continue  # placeholder / empty chapter
+            if r.primary_post_id is not None:
+                posts_seen[r.chapter_id][r.primary_post_id] = r.post_title
             page = {
                 "image_id": r.image_id,
                 "chapter_id": r.chapter_id,
@@ -191,11 +226,21 @@ class SeriesService:
             ch["pages"].append(page)
             flat.append(page)
 
+        # A chapter's source_post is set only when every page shares one post —
+        # the common case (a series authored from a post). Mixed chapters stay
+        # null rather than guessing.
+        for ch in chapters:
+            seen = posts_seen.get(ch["id"], {})
+            if len(seen) == 1:
+                pid, title = next(iter(seen.items()))
+                ch["source_post"] = {"id": pid, "title": title}
+
         return {
             "series": {"id": tag.id, "name": tag.name},
             "chapters": chapters,
             "pages": flat,  # back-compat: flat reading order across chapters
             "gaps": self._gaps(chapters),
+            "part_gaps": self._part_gaps(chapters),
         }
 
     # ---- pages ------------------------------------------------------------
@@ -353,19 +398,23 @@ class SeriesService:
         chapter_id: int,
         *,
         title: str | None = None,
+        stated_part: int | None = None,
         stated_page_start: int | None = None,
         stated_page_end: int | None = None,
         set_title: bool = False,
+        set_part: bool = False,
         set_start: bool = False,
         set_end: bool = False,
     ) -> None:
         """Partial chapter edit. The set_* flags say which fields to write (so
-        None can be written explicitly, e.g. clearing a stated page)."""
+        None can be written explicitly, e.g. clearing a stated page or part)."""
         await self._require_series(series_tag_id)
         await self._require_chapter(series_tag_id, chapter_id)
         values: dict = {}
         if set_title:
             values["title"] = title
+        if set_part:
+            values["stated_part"] = stated_part
         if set_start:
             values["stated_page_start"] = stated_page_start
         if set_end:
diff --git a/backend/app/services/tag_service.py b/backend/app/services/tag_service.py
index c798bfb..4616812 100644
--- a/backend/app/services/tag_service.py
+++ b/backend/app/services/tag_service.py
@@ -743,6 +743,10 @@ async def normalize_existing_tags(
         "sample": sample,
     }
     start = time.monotonic()
+    log.info(
+        "normalize_existing_tags: %d group(s) need changes (budget=%ss)",
+        len(touched), time_budget_seconds,
+    )
     for done, (key, members) in enumerate(touched):
         # Time-box: stop cleanly before the Celery limit kills us mid-group and
         # strands the run as a timeout. The caller re-enqueues to finish the
@@ -754,6 +758,16 @@ async def normalize_existing_tags(
             summary["partial"] = True
             summary["remaining"] = len(touched) - done
             break
+        # Heartbeat so a long run is diagnosable instead of silent — the timeout
+        # operator-flagged 2026-06-07 produced zero logs because the only log was
+        # per finished group and it was stuck mid-group on a lock.
+        if done and done % 25 == 0:
+            log.info(
+                "normalize_existing_tags: %d/%d groups (%d merged, %d errors, "
+                "%.0fs elapsed)",
+                done, len(touched), summary["merged"], summary["errors"],
+                time.monotonic() - start,
+            )
         canonical = key[2]
         names_by_id = dict(members)
         # Survivor: prefer a member already named canonically (no rename, no
diff --git a/backend/app/tasks/_async_session.py b/backend/app/tasks/_async_session.py
index e8c9094..0252dc3 100644
--- a/backend/app/tasks/_async_session.py
+++ b/backend/app/tasks/_async_session.py
@@ -15,8 +15,15 @@ from sqlalchemy.pool import NullPool
 from ..config import get_config
 
 
-def async_session_factory():
-    """Return ``(sessionmaker, engine)`` bound to a fresh async engine."""
+def async_session_factory(*, server_settings: dict | None = None):
+    """Return ``(sessionmaker, engine)`` bound to a fresh async engine.
+
+    ``server_settings`` (optional) are applied by asyncpg as per-connection GUCs
+    on connect. Because NullPool opens a fresh real connection per checkout, every
+    transaction in the task inherits them — used to set ``lock_timeout`` so a
+    statement blocked on a lock fails fast instead of hanging to the Celery hard
+    limit (operator-flagged normalize_tags timeout 2026-06-07).
+    """
     cfg = get_config()
     # NullPool: this engine lives for ONE task (created + disposed per
     # asyncio.run loop), so intra-task connection pooling buys nothing and
@@ -26,5 +33,13 @@ def async_session_factory():
     # phase 3 (asyncpg ConnectionDoesNotExistError, Anduo #40014). NullPool
     # opens a fresh real connection on each checkout, so phase 3 always
     # reconnects clean; pre_ping is then redundant.
-    engine = create_async_engine(cfg.database_url, future=True, poolclass=NullPool)
+    connect_args = {}
+    if server_settings:
+        connect_args["server_settings"] = {
+            k: str(v) for k, v in server_settings.items()
+        }
+    engine = create_async_engine(
+        cfg.database_url, future=True, poolclass=NullPool,
+        connect_args=connect_args,
+    )
     return async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False), engine
diff --git a/backend/app/tasks/admin.py b/backend/app/tasks/admin.py
index 8096707..c6a1b08 100644
--- a/backend/app/tasks/admin.py
+++ b/backend/app/tasks/admin.py
@@ -126,7 +126,16 @@ def normalize_tags_task(self) -> dict:
     from ._async_session import async_session_factory
 
     async def _run() -> dict:
-        async_factory, async_engine = async_session_factory()
+        # lock_timeout=30s: a per-group merge repoints FKs across image_tag and
+        # series_page; if a statement blocks on a lock (e.g. behind a schema
+        # migration holding ACCESS EXCLUSIVE on series_page — the exact wedge that
+        # made this task run to the 40-min hard limit with no progress,
+        # operator-flagged 2026-06-07), it now fails fast. The per-group handler
+        # catches it (rollback + error++) and the loop continues, so one blocked
+        # group can't strand the whole chunk.
+        async_factory, async_engine = async_session_factory(
+            server_settings={"lock_timeout": "30s"}
+        )
         try:
             async with async_factory() as session:
                 # normalize_existing_tags commits per group internally.
diff --git a/frontend/src/components/modal/FandomSetDialog.vue b/frontend/src/components/modal/FandomSetDialog.vue
index d60a362..730bf2c 100644
--- a/frontend/src/components/modal/FandomSetDialog.vue
+++ b/frontend/src/components/modal/FandomSetDialog.vue
@@ -3,20 +3,29 @@
     <v-card-title class="text-body-1">Fandom for “{{ tag.name }}”</v-card-title>
     <v-card-text>
       <template v-if="!collision">
+        <!-- Keyboard flow matches FandomPicker (operator-specified 2026-06-07):
+             focus lands here via the parent dialog's @after-enter → focusSearch
+             (autofocus is unreliable inside a v-dialog focus-trap); Tab moves to
+             the new-fandom field; a SECOND Enter (menu closed) accepts the choice
+             by Saving instead of re-opening the dropdown. -->
         <v-autocomplete
+          ref="fandomRef"
           v-model="selectedId"
+          v-model:menu="menuOpen"
           :items="store.fandomCache"
           :item-title="(f) => f.name" :item-value="(f) => f.id"
           label="Fandom" clearable density="compact"
-          autofocus
           :hint="selectedId == null
             ? 'No fandom — the character will be unassigned.' : ''"
           persistent-hint
+          @keydown.enter.capture="onSearchEnter"
+          @keydown.tab="onSearchTab"
         />
         <v-divider class="my-3" />
         <p class="text-caption mb-2">Or create a new fandom:</p>
         <div class="d-flex" style="gap: 8px;">
           <v-text-field
+            ref="newNameRef"
             v-model="newName" placeholder="New fandom name"
             density="compact" hide-details
             @keydown.enter.prevent="onCreate"
@@ -71,7 +80,7 @@
 </template>
 
 <script setup>
-import { onMounted, ref } from 'vue'
+import { nextTick, onMounted, ref } from 'vue'
 import { useTagStore } from '../../stores/tags.js'
 
 const props = defineProps({ tag: { type: Object, required: true } })
@@ -84,10 +93,25 @@ const newName = ref('')
 const busy = ref(false)
 const error = ref(null)
 const collision = ref(null)
+const menuOpen = ref(false)
+const fandomRef = ref(null)
+const newNameRef = ref(null)
 
 // Always refresh on open so the list reflects fandoms created elsewhere (#712).
 onMounted(() => store.loadFandoms())
 
+// Exposed so the parent dialog can focus the search field on @after-enter —
+// the reliable point to grab focus (the dialog transition + focus-trap are done).
+function focusSearch() {
+  nextTick(() => {
+    fandomRef.value?.focus?.()
+    // Keep the menu closed after a programmatic focus so the very next Enter
+    // accepts the value (Saves) instead of being swallowed as a menu interaction.
+    menuOpen.value = false
+  })
+}
+defineExpose({ focusSearch })
+
 async function onCreate() {
   const name = newName.value.trim()
   if (!name) return
@@ -97,6 +121,9 @@ async function onCreate() {
     const f = await store.createFandom(name)
     selectedId.value = f.id
     newName.value = ''
+    // The created fandom is now the selection; hand focus back to the dropdown
+    // so a single Enter saves it (matches FandomPicker's flow).
+    focusSearch()
   } catch (e) {
     error.value = e.message || String(e)
   } finally {
@@ -104,6 +131,29 @@ async function onCreate() {
   }
 }
 
+// Enter on the search field — bound in the CAPTURE phase so it runs BEFORE
+// Vuetify's own handler (which opens the menu on Enter). Menu open → let Vuetify
+// pick the highlighted item. Menu closed with a changed selection → Save and stop
+// the event so Vuetify never (re)opens the dropdown (the bug this fixes).
+function onSearchEnter(e) {
+  if (menuOpen.value) return
+  if (busy.value) return
+  if (selectedId.value !== (props.tag.fandom_id ?? null)) {
+    e.preventDefault()
+    e.stopPropagation()
+    onSave()
+  }
+}
+
+// Tab from the search field goes to the "new fandom" text field (operator-
+// specified). Shift+Tab keeps normal reverse traversal.
+function onSearchTab(e) {
+  if (e.shiftKey) return
+  e.preventDefault()
+  menuOpen.value = false
+  nextTick(() => newNameRef.value?.focus?.())
+}
+
 async function save(merge) {
   busy.value = true
   error.value = null
diff --git a/frontend/src/components/modal/TagPanel.vue b/frontend/src/components/modal/TagPanel.vue
index b180ec0..dfd00c2 100644
--- a/frontend/src/components/modal/TagPanel.vue
+++ b/frontend/src/components/modal/TagPanel.vue
@@ -34,8 +34,12 @@
       />
     </v-dialog>
 
-    <v-dialog v-model="fandomDialog" max-width="460">
+    <v-dialog
+      v-model="fandomDialog" max-width="460"
+      @after-enter="fandomSetRef?.focusSearch?.()"
+    >
       <FandomSetDialog
+        ref="fandomSetRef"
         v-if="fandomTarget" :tag="fandomTarget"
         @updated="onFandomUpdated" @cancel="fandomDialog = false"
       />
@@ -98,6 +102,7 @@ async function onRenamed() {
 
 const fandomDialog = ref(false)
 const fandomTarget = ref(null)
+const fandomSetRef = ref(null)
 function openSetFandom(tag) {
   fandomTarget.value = tag
   fandomDialog.value = true
diff --git a/frontend/src/components/modal/TagRenameDialog.vue b/frontend/src/components/modal/TagRenameDialog.vue
index 1bd8c08..750c8eb 100644
--- a/frontend/src/components/modal/TagRenameDialog.vue
+++ b/frontend/src/components/modal/TagRenameDialog.vue
@@ -2,25 +2,55 @@
   <v-card>
     <v-card-title>Rename tag</v-card-title>
     <v-card-text>
-      <v-text-field
-        v-model="newName" label="New name" density="compact"
-        autofocus @keydown.enter="submit"
-      />
-      <v-alert v-if="errorMsg" type="error" variant="tonal" density="compact" class="mt-2">
-        {{ errorMsg }}
-        <div v-if="isCollision" class="text-caption mt-1">
-          Merging two tags into one lands in FC-2c.
-        </div>
-      </v-alert>
+      <template v-if="!collision">
+        <v-text-field
+          v-model="newName" label="New name" density="compact"
+          autofocus @keydown.enter="submit"
+        />
+        <v-alert
+          v-if="errorMsg" type="error" variant="tonal" density="compact"
+          class="mt-2"
+        >{{ errorMsg }}</v-alert>
+      </template>
+
+      <template v-else>
+        <!-- A tag of this (kind, fandom) already has that name. Renaming onto it
+             is a merge, not a fork — same resolution the Tags view offers. -->
+        <v-alert type="warning" variant="tonal" density="compact" class="mb-3">
+          A {{ tag.kind }} tag named “{{ collision.target.name }}” already exists.
+        </v-alert>
+        <p class="text-body-2">
+          Merge “{{ tag.name }}” into “{{ collision.target.name }}”?
+          {{ collision.source_image_count }} image
+          association{{ collision.source_image_count === 1 ? '' : 's' }}
+          will move over and this tag will be deleted{{
+            collision.will_alias ? ' (its name kept as a tagger alias)' : '' }}.
+        </p>
+        <v-alert
+          v-if="errorMsg" type="error" variant="tonal" density="compact"
+          class="mt-3"
+        >{{ errorMsg }}</v-alert>
+      </template>
     </v-card-text>
     <v-card-actions>
       <v-spacer />
-      <v-btn @click="$emit('cancel')">Cancel</v-btn>
-      <v-btn
-        color="primary" rounded="pill"
-        :disabled="!newName.trim() || newName === tag.name"
-        :loading="busy" @click="submit"
-      >Rename</v-btn>
+      <template v-if="!collision">
+        <v-btn :disabled="busy" @click="$emit('cancel')">Cancel</v-btn>
+        <v-btn
+          color="primary" rounded="pill"
+          :disabled="!newName.trim() || newName === tag.name"
+          :loading="busy" @click="submit"
+        >Rename</v-btn>
+      </template>
+      <template v-else>
+        <v-btn :disabled="busy" @click="collision = null; errorMsg = null">
+          Back
+        </v-btn>
+        <v-btn
+          color="warning" variant="flat" rounded="pill"
+          :loading="busy" @click="onMerge"
+        >Merge</v-btn>
+      </template>
     </v-card-actions>
   </v-card>
 </template>
@@ -35,22 +65,41 @@ const emit = defineEmits(['renamed', 'cancel'])
 const api = useApi()
 const newName = ref(props.tag.name)
 const errorMsg = ref(null)
-const isCollision = ref(false)
+const collision = ref(null)
 const busy = ref(false)
 
 async function submit() {
   if (!newName.value.trim() || newName.value === props.tag.name) return
   busy.value = true
   errorMsg.value = null
-  isCollision.value = false
   try {
     const updated = await api.patch(`/api/tags/${props.tag.id}`, {
       body: { name: newName.value.trim() }
     })
     emit('renamed', updated)
+  } catch (e) {
+    // 409 → the new name collides with an existing tag of the same
+    // (kind, fandom). Offer to merge into it rather than dead-ending.
+    if (e.status === 409 && e.body && e.body.target) {
+      collision.value = e.body
+    } else {
+      errorMsg.value = e.message
+    }
+  } finally {
+    busy.value = false
+  }
+}
+
+async function onMerge() {
+  busy.value = true
+  errorMsg.value = null
+  try {
+    await api.post(`/api/tags/${props.tag.id}/merge`, {
+      body: { target_id: collision.value.target.id }
+    })
+    emit('renamed', { id: collision.value.target.id, name: collision.value.target.name })
   } catch (e) {
     errorMsg.value = e.message
-    isCollision.value = e.status === 409
   } finally {
     busy.value = false
   }
diff --git a/frontend/src/stores/seriesManage.js b/frontend/src/stores/seriesManage.js
index 9f7e628..e09da26 100644
--- a/frontend/src/stores/seriesManage.js
+++ b/frontend/src/stores/seriesManage.js
@@ -16,8 +16,9 @@ export const useSeriesManageStore = defineStore('seriesManage', () => {
 
   const tagId = ref(null)
   const series = ref(null)
-  const chapters = ref([])           // [{id, chapter_number, title, is_placeholder, stated_page_start/end, pages:[...]}]
-  const gaps = ref([])               // [{after_chapter_id, start, end}]
+  const chapters = ref([])           // [{id, chapter_number, stated_part, title, is_placeholder, stated_page_start/end, source_post, pages:[...]}]
+  const gaps = ref([])               // missing-page gaps: [{after_chapter_id, start, end}]
+  const partGaps = ref([])           // missing-Part gaps: [{after_chapter_id, start, end}]
   const pageCount = ref(0)
   const targetChapterId = ref(null)  // which chapter the picker adds into
   const picker = ref([])             // gallery scroll results
@@ -33,6 +34,7 @@ export const useSeriesManageStore = defineStore('seriesManage', () => {
       series.value = body.series
       chapters.value = body.chapters || []
       gaps.value = body.gaps || []
+      partGaps.value = body.part_gaps || []
       pageCount.value = (body.pages || []).length
       // Keep a valid add-target: the selected chapter, else the first one.
       const ids = chapters.value.map(c => c.id)
@@ -52,6 +54,10 @@ export const useSeriesManageStore = defineStore('seriesManage', () => {
     return gaps.value.find(g => g.after_chapter_id === chapterId) || null
   }
 
+  function partGapAfter(chapterId) {
+    return partGaps.value.find(g => g.after_chapter_id === chapterId) || null
+  }
+
   // ---- chapters ----
   async function createChapter({ title = null, isPlaceholder = false } = {}) {
     await api.post(`/api/series/${tagId.value}/chapters`, {
@@ -67,6 +73,13 @@ export const useSeriesManageStore = defineStore('seriesManage', () => {
     await refresh()
   }
 
+  async function setChapterPart(chapterId, part) {
+    await api.patch(`/api/series/${tagId.value}/chapters/${chapterId}`, {
+      body: { stated_part: part }
+    })
+    await refresh()
+  }
+
   async function setChapterStated(chapterId, start, end) {
     await api.patch(`/api/series/${tagId.value}/chapters/${chapterId}`, {
       body: { stated_page_start: start, stated_page_end: end }
@@ -151,11 +164,11 @@ export const useSeriesManageStore = defineStore('seriesManage', () => {
   }
 
   return {
-    tagId, series, chapters, gaps, pageCount, targetChapterId,
+    tagId, series, chapters, gaps, partGaps, pageCount, targetChapterId,
     picker, pickerCursor, pickerSelection, loading,
-    load, refresh, gapAfter,
-    createChapter, renameChapter, setChapterStated, reorderChapters,
-    moveChapter, deleteChapter, mergeChapter, reorderPages,
+    load, refresh, gapAfter, partGapAfter,
+    createChapter, renameChapter, setChapterPart, setChapterStated,
+    reorderChapters, moveChapter, deleteChapter, mergeChapter, reorderPages,
     loadPicker, togglePick, addSelected, remove, setCover
   }
 })
diff --git a/frontend/src/views/SeriesManageView.vue b/frontend/src/views/SeriesManageView.vue
index 52feba1..6f9b36e 100644
--- a/frontend/src/views/SeriesManageView.vue
+++ b/frontend/src/views/SeriesManageView.vue
@@ -1,159 +1,227 @@
 <template>
-  <v-container fluid class="pt-2 pb-6">
+  <v-container fluid class="pt-2 pb-10 fc-series">
     <div class="fc-series__head">
       <span class="fc-series__name">{{ store.series?.name || 'Series' }}</span>
       <span class="fc-series__count">
-        {{ store.chapters.length }} chapter(s) · {{ store.pageCount }} page(s)
+        {{ store.chapters.length }} part(s) · {{ store.pageCount }} page(s)
       </span>
+      <v-spacer />
       <v-btn
         v-if="store.pageCount > 0"
         size="small" variant="tonal" color="accent"
         prepend-icon="mdi-book-open"
-        class="fc-series__read"
         @click="$router.push({ name: 'series-read', params: { tagId: store.tagId } })"
       >Read</v-btn>
     </div>
 
-    <div class="fc-series__body">
-      <!-- Chapters column -->
-      <div class="fc-series__chapters">
-        <template v-for="(ch, ci) in store.chapters" :key="ch.id">
-          <section
-            class="fc-chapter"
-            :class="{ 'fc-chapter--target': ch.id === store.targetChapterId }"
-          >
-            <header class="fc-chapter__head">
-              <span class="fc-chapter__num">{{ ch.chapter_number }}</span>
-              <v-text-field
-                v-model="titleDraft[ch.id]"
-                :placeholder="`Chapter ${ch.chapter_number}`"
-                density="compact" variant="plain" hide-details
-                class="fc-chapter__title"
-                @keydown.enter="commitTitle(ch)"
-                @blur="commitTitle(ch)"
-              />
-              <span v-if="ch.is_placeholder" class="fc-chapter__ph">placeholder</span>
-              <span v-else class="fc-chapter__pc">{{ ch.pages.length }} pg</span>
+    <p class="fc-series__hint">
+      Each part is one installment — drag pages to set their order, and set the
+      <strong>Part #</strong> to mark where it falls in the story. Use
+      <strong>Add pages</strong> to pull images from the gallery into the part
+      you're working on.
+    </p>
 
-              <div class="fc-chapter__stated">
-                <input
-                  class="fc-chapter__num-in" type="number" min="0"
-                  :value="ch.stated_page_start ?? ''" placeholder="–"
-                  title="Stated first page"
-                  @change="onStated(ch, 'start', $event)"
-                >
-                <span>–</span>
-                <input
-                  class="fc-chapter__num-in" type="number" min="0"
-                  :value="ch.stated_page_end ?? ''" placeholder="–"
-                  title="Stated last page"
-                  @change="onStated(ch, 'end', $event)"
-                >
-              </div>
+    <!-- Parts, full width -->
+    <div class="fc-parts">
+      <template v-for="(ch, ci) in store.chapters" :key="ch.id">
+        <section class="fc-part">
+          <header class="fc-part__head">
+            <label class="fc-part__partfield" :title="'Part number for this installment'">
+              <span class="fc-part__partlabel">Part</span>
+              <input
+                class="fc-part__partnum" type="number" min="1"
+                :value="partDraft[ch.id] ?? ''"
+                :placeholder="String(ch.chapter_number)"
+                @input="partDraft[ch.id] = $event.target.value"
+                @keydown.enter.prevent="commitPart(ch)"
+                @blur="commitPart(ch)"
+              >
+            </label>
 
-              <div class="fc-chapter__actions">
+            <v-text-field
+              v-model="titleDraft[ch.id]"
+              :placeholder="`Untitled — Part ${ch.stated_part ?? ch.chapter_number}`"
+              density="compact" variant="plain" hide-details
+              class="fc-part__title"
+              @keydown.enter="commitTitle(ch)"
+              @blur="commitTitle(ch)"
+            />
+
+            <span
+              v-if="ch.source_post?.title" class="fc-part__src"
+              :title="ch.source_post.title"
+            >
+              <v-icon size="x-small">mdi-link-variant</v-icon>
+              {{ ch.source_post.title }}
+            </span>
+
+            <span v-if="ch.is_placeholder" class="fc-part__badge">placeholder</span>
+            <span v-else class="fc-part__pc">{{ ch.pages.length }} pg</span>
+
+            <v-spacer />
+
+            <v-btn
+              v-if="!ch.is_placeholder"
+              size="small" variant="tonal" color="accent"
+              prepend-icon="mdi-image-plus"
+              @click="openPicker(ch.id)"
+            >Add pages</v-btn>
+
+            <v-menu location="bottom end">
+              <template #activator="{ props }">
                 <v-btn
-                  size="x-small" variant="text" icon="mdi-chevron-up"
-                  title="Move chapter up" :disabled="ci === 0"
+                  v-bind="props" size="small" variant="text"
+                  icon="mdi-dots-vertical" title="Part actions"
+                />
+              </template>
+              <v-list density="compact">
+                <v-list-item
+                  prepend-icon="mdi-chevron-up" title="Move up"
+                  :disabled="ci === 0"
                   @click="store.moveChapter(ch.id, -1)"
                 />
-                <v-btn
-                  size="x-small" variant="text" icon="mdi-chevron-down"
-                  title="Move chapter down"
+                <v-list-item
+                  prepend-icon="mdi-chevron-down" title="Move down"
                   :disabled="ci === store.chapters.length - 1"
                   @click="store.moveChapter(ch.id, 1)"
                 />
-                <v-btn
-                  size="x-small" variant="text" icon="mdi-arrow-collapse-up"
-                  title="Merge into previous chapter" :disabled="ci === 0"
+                <v-list-item
+                  prepend-icon="mdi-arrow-collapse-up" title="Merge into previous"
+                  :disabled="ci === 0"
                   @click="store.mergeChapter(ch.id, store.chapters[ci - 1].id)"
                 />
-                <v-btn
-                  size="x-small" variant="text" icon="mdi-target"
-                  :color="ch.id === store.targetChapterId ? 'accent' : undefined"
-                  title="Add picked images here"
-                  @click="store.targetChapterId = ch.id"
+                <v-divider />
+                <v-list-item
+                  prepend-icon="mdi-delete-outline" title="Delete part"
+                  base-color="error"
+                  @click="confirmDelete(ch)"
                 />
-                <v-btn
-                  size="x-small" variant="text" icon="mdi-delete-outline"
-                  title="Delete chapter (removes its pages from the series)"
-                  @click="store.deleteChapter(ch.id)"
-                />
-              </div>
-            </header>
+              </v-list>
+            </v-menu>
+          </header>
 
-            <div v-if="ch.is_placeholder" class="fc-chapter__reserved">
-              Reserved slot — a section you don't have yet.
-            </div>
-            <div v-else-if="ch.pages.length === 0" class="fc-chapter__empty">
-              No pages — pick this chapter (◎) then add from the right.
-            </div>
-            <div v-else class="fc-chapter__pages">
-              <div
-                v-for="(p, pi) in ch.pages" :key="p.image_id"
-                class="fc-page" draggable="true"
-                @dragstart="drag = { chapterId: ch.id, idx: pi }"
-                @dragover.prevent
-                @drop="onPageDrop(ch, pi)"
-              >
-                <span class="fc-page__pn">{{ p.page_number }}</span>
-                <img :src="p.thumbnail_url" alt="" loading="lazy" />
-                <div class="fc-page__actions">
-                  <v-btn size="x-small" variant="text" icon="mdi-image-frame"
-                         title="Make cover" @click="store.setCover(p.image_id)" />
-                  <v-btn size="x-small" variant="text" icon="mdi-close"
-                         title="Remove" @click="store.remove(p.image_id)" />
-                </div>
-              </div>
-            </div>
-          </section>
-
-          <div
-            v-if="store.gapAfter(ch.id)"
-            class="fc-gap"
-          >
-            <v-icon size="x-small">mdi-alert-outline</v-icon>
-            Gap: pages {{ store.gapAfter(ch.id).start }}–{{ store.gapAfter(ch.id).end }} missing
+          <div class="fc-part__statedrow">
+            <span class="fc-part__statedlabel">Printed pages</span>
+            <input
+              class="fc-part__statedin" type="number" min="0"
+              :value="ch.stated_page_start ?? ''" placeholder="start"
+              @change="onStated(ch, 'start', $event)"
+            >
+            <span class="fc-part__dash">–</span>
+            <input
+              class="fc-part__statedin" type="number" min="0"
+              :value="ch.stated_page_end ?? ''" placeholder="end"
+              @change="onStated(ch, 'end', $event)"
+            >
+            <span class="fc-part__statedhelp">
+              optional — the page numbers printed in this installment
+            </span>
           </div>
-        </template>
 
-        <div v-if="store.chapters.length === 0" class="fc-series__empty">
-          No chapters yet — add one, then add images from the right.
-        </div>
+          <div v-if="ch.is_placeholder" class="fc-part__reserved">
+            Reserved slot — a part you don't have yet.
+          </div>
+          <div v-else-if="ch.pages.length === 0" class="fc-part__empty">
+            No pages yet.
+            <v-btn
+              size="small" variant="text" color="accent"
+              prepend-icon="mdi-image-plus" @click="openPicker(ch.id)"
+            >Add pages</v-btn>
+          </div>
+          <div v-else class="fc-part__pages">
+            <div
+              v-for="(p, pi) in ch.pages" :key="p.image_id"
+              class="fc-page" draggable="true"
+              :class="{ 'fc-page--dragging': drag && drag.chapterId === ch.id && drag.idx === pi }"
+              @dragstart="drag = { chapterId: ch.id, idx: pi }"
+              @dragend="drag = null"
+              @dragover.prevent
+              @drop="onPageDrop(ch, pi)"
+            >
+              <span class="fc-page__pn">{{ p.page_number }}</span>
+              <img :src="p.thumbnail_url" alt="" loading="lazy" />
+              <div class="fc-page__actions">
+                <v-btn size="x-small" variant="flat" icon="mdi-image-frame"
+                       title="Make series cover" @click="store.setCover(p.image_id)" />
+                <v-btn size="x-small" variant="flat" icon="mdi-close"
+                       title="Remove from series" @click="store.remove(p.image_id)" />
+              </div>
+            </div>
+          </div>
+        </section>
 
-        <div class="fc-series__chapter-add">
-          <v-btn size="small" variant="tonal" prepend-icon="mdi-plus"
-                 @click="store.createChapter()">Add chapter</v-btn>
-          <v-btn size="small" variant="text" prepend-icon="mdi-bookmark-outline"
-                 @click="store.createChapter({ isPlaceholder: true })">
-            Add placeholder
-          </v-btn>
+        <div v-if="store.partGapAfter(ch.id)" class="fc-gap">
+          <v-icon size="x-small">mdi-alert-outline</v-icon>
+          Missing
+          <template v-if="store.partGapAfter(ch.id).start === store.partGapAfter(ch.id).end">
+            Part {{ store.partGapAfter(ch.id).start }}
+          </template>
+          <template v-else>
+            Parts {{ store.partGapAfter(ch.id).start }}–{{ store.partGapAfter(ch.id).end }}
+          </template>
         </div>
+        <div v-if="store.gapAfter(ch.id)" class="fc-gap">
+          <v-icon size="x-small">mdi-alert-outline</v-icon>
+          Gap: printed pages {{ store.gapAfter(ch.id).start }}–{{ store.gapAfter(ch.id).end }} missing
+        </div>
+      </template>
+
+      <div v-if="store.chapters.length === 0" class="fc-series__empty">
+        No parts yet — add one, then add pages from the gallery.
       </div>
 
-      <!-- Picker column -->
-      <div class="fc-series__picker">
-        <div class="fc-series__pickerhead">
+      <div class="fc-parts__add">
+        <v-btn size="small" variant="tonal" prepend-icon="mdi-plus"
+               @click="store.createChapter()">Add part</v-btn>
+        <v-btn size="small" variant="text" prepend-icon="mdi-bookmark-outline"
+               @click="store.createChapter({ isPlaceholder: true })">
+          Add placeholder
+        </v-btn>
+      </div>
+    </div>
+
+    <!-- Picker slide-over -->
+    <v-navigation-drawer
+      v-model="pickerOpen" location="right" temporary width="420"
+      class="fc-picker"
+    >
+      <div class="fc-picker__head">
+        <div class="fc-picker__title">
+          <span>Add pages</span>
+          <v-btn size="x-small" variant="text" icon="mdi-close"
+                 @click="pickerOpen = false" />
+        </div>
+        <v-select
+          v-model="store.targetChapterId"
+          :items="chapterItems" item-title="label" item-value="id"
+          density="compact" variant="outlined" hide-details
+          label="Add to part" class="mt-2"
+        />
+        <div class="fc-picker__bar">
           <span>{{ store.pickerSelection.length }} selected</span>
           <v-btn
             size="small" color="accent" variant="flat"
             :disabled="store.pickerSelection.length === 0"
             @click="store.addSelected()"
-          >Add to {{ targetLabel }}</v-btn>
+          >Add to part</v-btn>
         </div>
-        <div class="fc-series__pickergrid">
-          <div
-            v-for="img in store.picker" :key="img.id"
-            class="fc-series__pick"
-            :class="{ on: store.pickerSelection.includes(img.id) }"
-            @click="store.togglePick(img.id)"
-          >
-            <img :src="img.thumbnail_url" alt="" loading="lazy" />
-          </div>
-        </div>
-        <div ref="sentinel" class="fc-series__sentinel" />
       </div>
-    </div>
+      <div class="fc-picker__grid">
+        <div
+          v-for="img in store.picker" :key="img.id"
+          class="fc-picker__pick"
+          :class="{ on: store.pickerSelection.includes(img.id) }"
+          @click="store.togglePick(img.id)"
+        >
+          <img :src="img.thumbnail_url" alt="" loading="lazy" />
+          <v-icon
+            v-if="store.pickerSelection.includes(img.id)"
+            class="fc-picker__check" color="accent" size="small"
+          >mdi-check-circle</v-icon>
+        </div>
+        <div ref="sentinel" class="fc-picker__sentinel" />
+      </div>
+    </v-navigation-drawer>
   </v-container>
 </template>
 
@@ -167,20 +235,29 @@ const route = useRoute()
 const store = useSeriesManageStore()
 const sentinel = ref(null)
 const drag = ref(null)            // { chapterId, idx }
-const titleDraft = reactive({})   // chapterId -> draft string
+const titleDraft = reactive({})   // chapterId -> draft title
+const partDraft = reactive({})    // chapterId -> draft stated_part (string)
+const pickerOpen = ref(false)
 
-// Keep local title drafts in sync with the loaded chapters. Edits commit on
-// blur/Enter, which refreshes and resets the draft to the saved value.
+// Keep local drafts in sync with loaded chapters. Edits commit on blur/Enter,
+// which refreshes and resets the draft to the saved value.
 watch(() => store.chapters, (chs) => {
-  Object.keys(titleDraft).forEach(k => delete titleDraft[k])
-  for (const c of chs) titleDraft[c.id] = c.title || ''
+  for (const k of Object.keys(titleDraft)) delete titleDraft[k]
+  for (const k of Object.keys(partDraft)) delete partDraft[k]
+  for (const c of chs) {
+    titleDraft[c.id] = c.title || ''
+    partDraft[c.id] = c.stated_part == null ? '' : String(c.stated_part)
+  }
 }, { immediate: true })
 
-const targetLabel = computed(() => {
-  const ch = store.chapters.find(c => c.id === store.targetChapterId)
-  if (!ch) return 'chapter'
-  return ch.title || `Chapter ${ch.chapter_number}`
-})
+const chapterItems = computed(() =>
+  store.chapters.map(c => ({
+    id: c.id,
+    label: `Part ${c.stated_part ?? c.chapter_number}` +
+      (c.title ? ` — ${c.title}` : '') +
+      (c.is_placeholder ? ' (placeholder)' : ` · ${c.pages.length} pg`),
+  }))
+)
 
 function commitTitle(ch) {
   const v = (titleDraft[ch.id] || '').trim()
@@ -188,6 +265,17 @@ function commitTitle(ch) {
   store.renameChapter(ch.id, v || null)
 }
 
+function commitPart(ch) {
+  const raw = (partDraft[ch.id] ?? '').trim()
+  const next = raw === '' ? null : parseInt(raw, 10)
+  if (raw !== '' && (Number.isNaN(next) || next < 1)) {
+    partDraft[ch.id] = ch.stated_part == null ? '' : String(ch.stated_part)
+    return
+  }
+  if (next === (ch.stated_part ?? null)) return
+  store.setChapterPart(ch.id, next)
+}
+
 function onStated(ch, which, ev) {
   const raw = ev.target.value
   const n = raw === '' ? null : parseInt(raw, 10)
@@ -206,6 +294,20 @@ function onPageDrop(chapter, toIdx) {
   store.reorderPages(chapter.id, ordered)
 }
 
+function confirmDelete(ch) {
+  const label = `Part ${ch.stated_part ?? ch.chapter_number}`
+  const n = ch.pages.length
+  const msg = n
+    ? `Delete ${label} and remove its ${n} page(s) from the series?`
+    : `Delete ${label}?`
+  if (window.confirm(msg)) store.deleteChapter(ch.id)
+}
+
+function openPicker(chapterId) {
+  store.targetChapterId = chapterId
+  pickerOpen.value = true
+}
+
 useInfiniteScroll(sentinel, () => store.loadPicker())
 
 onMounted(async () => {
@@ -216,91 +318,146 @@ onMounted(async () => {
 
 <style scoped>
 .fc-series__head {
-  display: flex; align-items: baseline; gap: 12px; margin-bottom: 16px;
+  display: flex; align-items: baseline; gap: 12px; margin-bottom: 4px;
 }
-.fc-series__name { font-family: 'Fraunces', Georgia, serif; font-size: 22px; }
+.fc-series__name { font-family: 'Fraunces', Georgia, serif; font-size: 24px; }
 .fc-series__count {
   font-size: 13px; color: rgb(var(--v-theme-on-surface-variant));
 }
-.fc-series__body { display: flex; gap: 16px; align-items: flex-start; }
-.fc-series__chapters {
-  flex: 1; min-width: 0; display: flex; flex-direction: column; gap: 10px;
+.fc-series__hint {
+  font-size: 13px; color: rgb(var(--v-theme-on-surface-variant));
+  margin-bottom: 18px; max-width: 760px;
 }
 
-.fc-chapter {
+/* Parts — full width, stacked */
+.fc-parts { display: flex; flex-direction: column; gap: 14px; max-width: 1100px; }
+.fc-part {
   border: 1px solid rgb(var(--v-theme-surface-light));
-  border-radius: 8px; padding: 8px 10px;
+  border-radius: 10px; padding: 12px 14px;
   background: rgb(var(--v-theme-surface));
 }
-.fc-chapter--target { border-color: rgb(var(--v-theme-accent), 0.7); }
-.fc-chapter__head { display: flex; align-items: center; gap: 8px; }
-.fc-chapter__num {
-  flex: 0 0 auto; min-width: 22px; height: 22px; border-radius: 4px;
-  display: inline-flex; align-items: center; justify-content: center;
-  font-size: 12px; font-variant-numeric: tabular-nums;
-  background: rgb(var(--v-theme-accent), 0.16);
+.fc-part__head { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; }
+
+.fc-part__partfield {
+  display: inline-flex; align-items: center; gap: 6px;
+  background: rgb(var(--v-theme-accent), 0.12);
+  border: 1px solid rgb(var(--v-theme-accent), 0.35);
+  border-radius: 8px; padding: 4px 8px;
+}
+.fc-part__partlabel {
+  font-size: 12px; text-transform: uppercase; letter-spacing: 0.06em;
   color: rgb(var(--v-theme-accent));
 }
-.fc-chapter__title { flex: 1; min-width: 0; }
-.fc-chapter__ph {
+.fc-part__partnum {
+  width: 46px; text-align: center; font-size: 18px; font-weight: 600;
+  font-variant-numeric: tabular-nums;
+  background: transparent; border: none; color: rgb(var(--v-theme-on-surface));
+}
+.fc-part__partnum:focus { outline: none; }
+.fc-part__partnum::placeholder { color: rgb(var(--v-theme-on-surface-variant)); opacity: 0.6; }
+
+.fc-part__title { flex: 1 1 180px; min-width: 120px; font-size: 15px; }
+.fc-part__src {
+  display: inline-flex; align-items: center; gap: 4px; max-width: 240px;
+  overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
+  font-size: 12px; color: rgb(var(--v-theme-on-surface-variant));
+}
+.fc-part__badge {
   font-size: 11px; text-transform: uppercase; letter-spacing: 0.04em;
   color: rgb(var(--v-theme-on-surface-variant));
 }
-.fc-chapter__pc {
+.fc-part__pc {
   font-size: 12px; color: rgb(var(--v-theme-on-surface-variant));
   font-variant-numeric: tabular-nums;
 }
-.fc-chapter__stated { display: inline-flex; align-items: center; gap: 4px; }
-.fc-chapter__num-in {
-  width: 42px; text-align: center; font-size: 12px;
+
+.fc-part__statedrow {
+  display: flex; align-items: center; gap: 6px; margin: 8px 0 2px;
+  font-size: 12px; color: rgb(var(--v-theme-on-surface-variant));
+}
+.fc-part__statedlabel { text-transform: uppercase; letter-spacing: 0.04em; font-size: 11px; }
+.fc-part__statedin {
+  width: 56px; text-align: center; font-size: 12px;
   background: rgb(var(--v-theme-surface-light));
   border: 1px solid transparent; border-radius: 4px; padding: 2px 4px;
   color: rgb(var(--v-theme-on-surface));
 }
-.fc-chapter__num-in:focus { outline: none; border-color: rgb(var(--v-theme-accent)); }
-.fc-chapter__actions { flex: 0 0 auto; display: inline-flex; }
-.fc-chapter__reserved, .fc-chapter__empty {
-  padding: 14px; text-align: center; font-size: 13px;
+.fc-part__statedin:focus { outline: none; border-color: rgb(var(--v-theme-accent)); }
+.fc-part__dash { opacity: 0.6; }
+.fc-part__statedhelp { font-size: 11px; opacity: 0.7; }
+
+.fc-part__reserved, .fc-part__empty {
+  padding: 18px; text-align: center; font-size: 13px;
   color: rgb(var(--v-theme-on-surface-variant));
 }
-.fc-chapter__pages { display: flex; flex-direction: column; gap: 6px; margin-top: 6px; }
+
+/* Big page grid */
+.fc-part__pages {
+  display: grid; gap: 10px; margin-top: 10px;
+  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
+}
 .fc-page {
-  display: flex; align-items: center; gap: 10px; padding: 6px;
-  background: rgb(var(--v-theme-surface-light)); border-radius: 6px; cursor: grab;
+  position: relative; border-radius: 8px; overflow: hidden; cursor: grab;
+  background: rgb(var(--v-theme-surface-light));
+  border: 1px solid rgb(var(--v-theme-surface-light));
+}
+.fc-page--dragging { opacity: 0.4; }
+.fc-page img {
+  width: 100%; aspect-ratio: 3 / 4; object-fit: contain;
+  display: block; background: rgb(var(--v-theme-background));
 }
-.fc-page img { width: 56px; height: 56px; object-fit: cover; border-radius: 4px; }
 .fc-page__pn {
-  width: 26px; text-align: center; font-variant-numeric: tabular-nums;
-  color: rgb(var(--v-theme-on-surface-variant));
+  position: absolute; top: 6px; left: 6px; z-index: 2;
+  min-width: 24px; height: 24px; padding: 0 6px; border-radius: 12px;
+  display: inline-flex; align-items: center; justify-content: center;
+  font-size: 13px; font-weight: 600; font-variant-numeric: tabular-nums;
+  background: rgb(var(--v-theme-accent)); color: rgb(var(--v-theme-on-accent, 0 0 0));
 }
-.fc-page__actions { margin-left: auto; }
+.fc-page__actions {
+  position: absolute; top: 4px; right: 4px; z-index: 2;
+  display: flex; gap: 2px; opacity: 0; transition: opacity 0.12s;
+}
+.fc-page:hover .fc-page__actions, .fc-page:focus-within .fc-page__actions { opacity: 1; }
+.fc-page__actions :deep(.v-btn) {
+  background: rgba(0, 0, 0, 0.55); color: #fff;
+}
+
 .fc-gap {
-  display: flex; align-items: center; gap: 6px; padding: 4px 10px;
+  display: flex; align-items: center; gap: 6px; padding: 2px 10px;
   font-size: 12px; color: rgb(var(--v-theme-warning, var(--v-theme-accent)));
 }
-.fc-series__chapter-add { display: flex; gap: 8px; margin-top: 4px; }
+.fc-parts__add { display: flex; gap: 8px; margin-top: 4px; }
 .fc-series__empty {
-  padding: 32px; text-align: center; color: rgb(var(--v-theme-on-surface-variant));
+  padding: 40px; text-align: center; color: rgb(var(--v-theme-on-surface-variant));
 }
 
-.fc-series__picker { flex: 1; min-width: 0; }
-.fc-series__pickerhead {
+/* Picker slide-over */
+.fc-picker__head {
+  position: sticky; top: 0; z-index: 1; padding: 12px 14px;
+  background: rgb(var(--v-theme-surface));
+  border-bottom: 1px solid rgb(var(--v-theme-surface-light));
+}
+.fc-picker__title {
   display: flex; align-items: center; justify-content: space-between;
-  margin-bottom: 8px;
+  font-family: 'Fraunces', Georgia, serif; font-size: 18px;
 }
-.fc-series__pickergrid {
-  display: grid; grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
-  gap: 6px;
+.fc-picker__bar {
+  display: flex; align-items: center; justify-content: space-between;
+  margin-top: 10px; font-size: 13px;
 }
-.fc-series__pick {
-  cursor: pointer; aspect-ratio: 1; overflow: hidden;
-  border-radius: 4px; outline: 2px solid transparent;
+.fc-picker__grid {
+  display: grid; gap: 6px; padding: 12px;
+  grid-template-columns: repeat(auto-fill, minmax(110px, 1fr));
 }
-.fc-series__pick img { width: 100%; height: 100%; object-fit: cover; }
-.fc-series__pick.on { outline-color: rgb(var(--v-theme-accent)); }
-.fc-series__sentinel { height: 40px; }
-
-@media (max-width: 900px) {
-  .fc-series__body { flex-direction: column; }
+.fc-picker__pick {
+  position: relative; cursor: pointer; aspect-ratio: 1; overflow: hidden;
+  border-radius: 6px; outline: 2px solid transparent;
 }
+.fc-picker__pick img { width: 100%; height: 100%; object-fit: cover; }
+.fc-picker__pick.on { outline-color: rgb(var(--v-theme-accent)); }
+.fc-picker__check {
+  position: absolute; top: 4px; right: 4px;
+  background: rgba(0, 0, 0, 0.5); border-radius: 50%;
+}
+.fc-picker__sentinel { grid-column: 1 / -1; height: 40px; }
 </style>
diff --git a/frontend/src/views/TagsView.vue b/frontend/src/views/TagsView.vue
index 262a755..84f7e67 100644
--- a/frontend/src/views/TagsView.vue
+++ b/frontend/src/views/TagsView.vue
@@ -87,8 +87,12 @@
       @confirm="onDeleteTagConfirm"
     />
 
-    <v-dialog v-model="fandomDialogOpen" max-width="460">
+    <v-dialog
+      v-model="fandomDialogOpen" max-width="460"
+      @after-enter="fandomSetRef?.focusSearch?.()"
+    >
       <FandomSetDialog
+        ref="fandomSetRef"
         v-if="fandomTarget" :tag="fandomTarget"
         @updated="onFandomUpdated" @cancel="fandomDialogOpen = false"
       />
@@ -152,6 +156,7 @@ function openTag(tagId) {
 // Character fandom editing (dots-menu → FandomSetDialog).
 const fandomDialogOpen = ref(false)
 const fandomTarget = ref(null)
+const fandomSetRef = ref(null)
 function onSetFandom(card) {
   fandomTarget.value = card
   fandomDialogOpen.value = true
diff --git a/frontend/test/seriesManage.spec.js b/frontend/test/seriesManage.spec.js
index dc185d5..8553766 100644
--- a/frontend/test/seriesManage.spec.js
+++ b/frontend/test/seriesManage.spec.js
@@ -75,6 +75,33 @@ describe('seriesManage', () => {
     expect(r.body).toEqual({ chapter_ids: [2, 1, 3] })
   })
 
+  it('setChapterPart patches stated_part on the chapter', async () => {
+    const s = useSeriesManageStore()
+    s.tagId = 7
+    const calls = []
+    stubFetch((url, init) => {
+      calls.push({ url, method: init.method, body: init.body ? JSON.parse(init.body) : null })
+      if (init.method === 'PATCH') return { status: 200, body: { ok: true } }
+      return { status: 200, body: SERIES_BODY }
+    })
+    await s.setChapterPart(1, 2)
+    const p = calls.find(c => c.method === 'PATCH')
+    expect(p.url).toContain('/api/series/7/chapters/1')
+    expect(p.body).toEqual({ stated_part: 2 })
+  })
+
+  it('load surfaces part_gaps and partGapAfter looks them up', async () => {
+    const s = useSeriesManageStore()
+    stubFetch(() => ({
+      status: 200,
+      body: { ...SERIES_BODY, part_gaps: [{ after_chapter_id: 1, start: 2, end: 2 }] }
+    }))
+    await s.load(7)
+    expect(s.partGaps).toHaveLength(1)
+    expect(s.partGapAfter(1)).toEqual({ after_chapter_id: 1, start: 2, end: 2 })
+    expect(s.partGapAfter(99)).toBeNull()
+  })
+
   it('addSelected posts selection + target chapter then clears', async () => {
     const s = useSeriesManageStore()
     s.tagId = 7
diff --git a/tests/test_series_from_post.py b/tests/test_series_from_post.py
index abd63f8..3c45bd2 100644
--- a/tests/test_series_from_post.py
+++ b/tests/test_series_from_post.py
@@ -113,3 +113,52 @@ async def test_list_series_cards(db):
     # artist filter keeps it; a different artist id drops it.
     assert any(r["id"] == out["series_tag_id"] for r in await svc.list_series(artist_id=artist.id))
     assert all(r["id"] != out["series_tag_id"] for r in await svc.list_series(artist_id=artist.id + 99999))
+
+
+# --- FC-6.4: stated_part, part_gaps, source_post label ---------------------
+
+
+@pytest.mark.asyncio
+async def test_update_chapter_sets_and_clears_stated_part(db):
+    svc = SeriesService(db)
+    sid = (await TagService(db).find_or_create("Part Series", TagKind.series)).id
+    ch = await svc.create_chapter(sid)
+    # Set the installment to Part 2 (chapter_number stays its positional value).
+    await svc.update_chapter(sid, ch["id"], stated_part=2, set_part=True)
+    data = await svc.list_pages(sid)
+    assert data["chapters"][0]["stated_part"] == 2
+    assert data["chapters"][0]["chapter_number"] == 1
+    # Clearing it writes NULL back.
+    await svc.update_chapter(sid, ch["id"], stated_part=None, set_part=True)
+    data = await svc.list_pages(sid)
+    assert data["chapters"][0]["stated_part"] is None
+
+
+@pytest.mark.asyncio
+async def test_part_gaps_flagged_from_stated_part(db):
+    svc = SeriesService(db)
+    sid = (await TagService(db).find_or_create("Gappy Series", TagKind.series)).id
+    c1 = await svc.create_chapter(sid)
+    c3 = await svc.create_chapter(sid)
+    await svc.update_chapter(sid, c1["id"], stated_part=1, set_part=True)
+    await svc.update_chapter(sid, c3["id"], stated_part=3, set_part=True)
+    data = await svc.list_pages(sid)
+    assert len(data["part_gaps"]) == 1
+    gap = data["part_gaps"][0]
+    assert gap["after_chapter_id"] == c1["id"]
+    assert gap["start"] == 2
+    assert gap["end"] == 2
+
+
+@pytest.mark.asyncio
+async def test_source_post_label_when_pages_share_one_post(db):
+    svc = SeriesService(db)
+    artist = await _artist(db, "Src Artist")
+    post = await _post(db, artist, "Source Comic pages 1-2", "pp5")
+    await _post_images(db, post, artist, 2)
+    out = await svc.promote_post_to_series(post.id)
+    data = await svc.list_pages(out["series_tag_id"])
+    sp = data["chapters"][0]["source_post"]
+    assert sp is not None
+    assert sp["id"] == post.id
+    assert sp["title"] == "Source Comic pages 1-2"