diff --git a/server/service/media/index.ts b/server/service/media/index.ts
new file mode 100644
index 0000000..17354b1
--- /dev/null
+++ b/server/service/media/index.ts
@@ -0,0 +1,328 @@
+import fs from "node:fs";
+import path from "node:path";
+import { dbGlobal } from "drizzle-pkg/lib/db";
+import { mediaAssets, postMediaRefs } from "drizzle-pkg/lib/schema/content";
+import { and, count, desc, eq, inArray, isNotNull, isNull, lte, not, notExists, or, sql } from "drizzle-orm";
+import {
+  MEDIA_ORPHAN_GRACE_HOURS_AFTER_DEREF,
+  MEDIA_ORPHAN_GRACE_HOURS_NEVER_REF,
+  POST_MEDIA_PUBLIC_PREFIX,
+  RELATIVE_ASSETS_DIR,
+} from "#server/constants/media";
+import { mergePostMediaUrls, publicAssetUrlToStorageKey } from "#server/utils/post-media-urls";
+import { nextIntegerId } from "#server/utils/sqlite-id";
+
+const NEVER_REF_MS = MEDIA_ORPHAN_GRACE_HOURS_NEVER_REF * 3600 * 1000;
+const AFTER_DEREF_MS = MEDIA_ORPHAN_GRACE_HOURS_AFTER_DEREF * 3600 * 1000;
+
+function assetsBaseDir(): string {
+  return path.resolve(process.cwd(), RELATIVE_ASSETS_DIR);
+}
+
+function isPathUnderAssetsDir(resolvedFile: string): boolean {
+  const base = assetsBaseDir() + path.sep;
+  return resolvedFile === assetsBaseDir() || resolvedFile.startsWith(base);
+}
+
+/** 删除主文件及 variantsJson 中列出的、位于 assets 目录下的相对路径 */
+async function unlinkMediaFiles(storageKey: string, variantsJson: string | null): Promise<void> {
+  const main = path.resolve(assetsBaseDir(), storageKey);
+  if (!isPathUnderAssetsDir(main)) {
+    return;
+  }
+  try {
+    await fs.promises.unlink(main);
+  } catch (e) {
+    if ((e as NodeJS.ErrnoException).code !== "ENOENT") {
+      throw e;
+    }
+  }
+
+  const rels = parseVariantRelativePaths(variantsJson);
+  for (const rel of rels) {
+    if (rel.includes("..") || path.isAbsolute(rel)) {
+      continue;
+    }
+    const full = path.resolve(assetsBaseDir(), rel);
+    if (!isPathUnderAssetsDir(full)) {
+      continue;
+    }
+    try {
+      await fs.promises.unlink(full);
+    } catch (e) {
+      if ((e as NodeJS.ErrnoException).code !== "ENOENT") {
+        throw e;
+      }
+    }
+  }
+}
+
+function parseVariantRelativePaths(raw: string | null): string[] {
+  if (!raw) {
+    return [];
+  }
+  try {
+    const j = JSON.parse(raw) as unknown;
+    if (!Array.isArray(j)) {
+      return [];
+    }
+    return j.filter((x): x is string => typeof x === "string" && x.length > 0);
+  } catch {
+    return [];
+  }
+}
+
+export function isAssetDeletable(row: {
+  firstReferencedAt: Date | null;
+  dereferencedAt: Date | null;
+  createdAt: Date;
+}): boolean {
+  const now = Date.now();
+  if (row.firstReferencedAt == null) {
+    return row.createdAt.getTime() <= now - NEVER_REF_MS;
+  }
+  if (row.dereferencedAt == null) {
+    return false;
+  }
+  return row.dereferencedAt.getTime() <= now - AFTER_DEREF_MS;
+}
+
+function orphanCondition() {
+  return notExists(
+    dbGlobal.select({ x: sql`1` }).from(postMediaRefs).where(eq(postMediaRefs.assetId, mediaAssets.id)),
+  );
+}
+
+function deletableTimeCondition(now: number) {
+  const neverRefCutoff = new Date(now - NEVER_REF_MS);
+  const afterDerefCutoff = new Date(now - AFTER_DEREF_MS);
+  return or(
+    and(isNull(mediaAssets.firstReferencedAt), lte(mediaAssets.createdAt, neverRefCutoff)),
+    and(
+      isNotNull(mediaAssets.firstReferencedAt),
+      isNotNull(mediaAssets.dereferencedAt),
+      lte(mediaAssets.dereferencedAt, afterDerefCutoff),
+    ),
+  );
+}
+
+export async function insertMediaAssetRow(params: {
+  userId: number;
+  storageKey: string;
+  mime: string;
+  sizeBytes: number;
+  sha256?: string | null;
+  variantsJson?: string | null;
+}): Promise<number> {
+  const id = await nextIntegerId(mediaAssets, mediaAssets.id);
+  await dbGlobal.insert(mediaAssets).values({
+    id,
+    userId: params.userId,
+    storageKey: params.storageKey,
+    mime: params.mime,
+    sizeBytes: params.sizeBytes,
+    sha256: params.sha256 ?? null,
+    variantsJson: params.variantsJson ?? null,
+  });
+  return id;
+}
+
+export async function reconcileAssetTimestampsAfterRefChange(assetIds: number[]): Promise<void> {
+  const unique = [...new Set(assetIds)];
+  for (const id of unique) {
+    const [{ c }] = await dbGlobal
+      .select({ c: count() })
+      .from(postMediaRefs)
+      .where(eq(postMediaRefs.assetId, id));
+
+    if (c > 0) {
+      const [row] = await dbGlobal.select().from(mediaAssets).where(eq(mediaAssets.id, id)).limit(1);
+      if (!row) {
+        continue;
+      }
+      await dbGlobal
+        .update(mediaAssets)
+        .set({
+          firstReferencedAt: row.firstReferencedAt ?? new Date(),
+          dereferencedAt: null,
+        })
+        .where(eq(mediaAssets.id, id));
+      continue;
+    }
+
+    const [row] = await dbGlobal.select().from(mediaAssets).where(eq(mediaAssets.id, id)).limit(1);
+    if (!row) {
+      continue;
+    }
+    if (row.firstReferencedAt == null) {
+      continue;
+    }
+    if (row.dereferencedAt != null) {
+      continue;
+    }
+    await dbGlobal
+      .update(mediaAssets)
+      .set({ dereferencedAt: new Date() })
+      .where(eq(mediaAssets.id, id));
+  }
+}
+
+export async function syncPostMediaRefs(
+  userId: number,
+  postId: number,
+  bodyMarkdown: string,
+  coverUrl: string | null,
+): Promise<void> {
+  const beforeRows = await dbGlobal
+    .select({ assetId: postMediaRefs.assetId })
+    .from(postMediaRefs)
+    .where(eq(postMediaRefs.postId, postId));
+  const beforeIds = beforeRows.map((r) => r.assetId);
+
+  await dbGlobal.delete(postMediaRefs).where(eq(postMediaRefs.postId, postId));
+
+  const urls = mergePostMediaUrls(bodyMarkdown, coverUrl);
+  const keys = [...new Set(urls.map((u) => publicAssetUrlToStorageKey(u)).filter((k): k is string => k != null))];
+
+  let afterIds: number[] = [];
+  if (keys.length > 0) {
+    const assetRows = await dbGlobal
+      .select({ id: mediaAssets.id })
+      .from(mediaAssets)
+      .where(and(eq(mediaAssets.userId, userId), inArray(mediaAssets.storageKey, keys)));
+    afterIds = assetRows.map((r) => r.id);
+    if (afterIds.length > 0) {
+      await dbGlobal
+        .insert(postMediaRefs)
+        .values(afterIds.map((assetId) => ({ postId, assetId })))
+        .onConflictDoNothing();
+    }
+  }
+
+  await reconcileAssetTimestampsAfterRefChange([...new Set([...beforeIds, ...afterIds])]);
+}
+
+export async function listOrphanCandidatesForUser(
+  userId: number,
+  filter: "all" | "deletable" | "cooling",
+  page: number,
+  pageSize: number,
+): Promise<{
+  items: Array<{
+    id: number;
+    storageKey: string;
+    publicUrl: string;
+    sizeBytes: number;
+    createdAt: Date;
+    firstReferencedAt: Date | null;
+    dereferencedAt: Date | null;
+    state: "deletable" | "cooling";
+  }>;
+  total: number;
+}> {
+  const now = Date.now();
+  const base = and(eq(mediaAssets.userId, userId), orphanCondition());
+
+  let whereClause =
+    filter === "all"
+      ? base
+      : filter === "deletable"
+        ? and(base, deletableTimeCondition(now))
+        : and(base, not(deletableTimeCondition(now)));
+
+  const [{ total: totalRaw }] = await dbGlobal.select({ total: count() }).from(mediaAssets).where(whereClause);
+
+  const offset = Math.max(0, (page - 1) * pageSize);
+  const rows = await dbGlobal
+    .select({
+      id: mediaAssets.id,
+      storageKey: mediaAssets.storageKey,
+      sizeBytes: mediaAssets.sizeBytes,
+      createdAt: mediaAssets.createdAt,
+      firstReferencedAt: mediaAssets.firstReferencedAt,
+      dereferencedAt: mediaAssets.dereferencedAt,
+    })
+    .from(mediaAssets)
+    .where(whereClause)
+    .orderBy(desc(mediaAssets.createdAt), desc(mediaAssets.id))
+    .limit(pageSize)
+    .offset(offset);
+
+  const items = rows.map((row) => {
+    const state: "deletable" | "cooling" = isAssetDeletable(row) ? "deletable" : "cooling";
+    return {
+      id: row.id,
+      storageKey: row.storageKey,
+      publicUrl: `${POST_MEDIA_PUBLIC_PREFIX}${row.storageKey}`,
+      sizeBytes: row.sizeBytes,
+      createdAt: row.createdAt,
+      firstReferencedAt: row.firstReferencedAt,
+      dereferencedAt: row.dereferencedAt,
+      state,
+    };
+  });
+
+  return { items, total: totalRaw };
+}
+
+async function assertAssetDeletableOrThrow(row: typeof mediaAssets.$inferSelect): Promise<void> {
+  const [{ c }] = await dbGlobal
+    .select({ c: count() })
+    .from(postMediaRefs)
+    .where(eq(postMediaRefs.assetId, row.id));
+  if (c > 0) {
+    throw createError({ statusCode: 400, statusMessage: "资源仍被文章引用，无法删除" });
+  }
+  if (!isAssetDeletable(row)) {
+    throw createError({ statusCode: 400, statusMessage: "资源尚在宽限期，暂不可删除" });
+  }
+}
+
+export async function deleteMediaAssetsForUser(userId: number, ids: number[]): Promise<number> {
+  if (ids.length === 0) {
+    return 0;
+  }
+
+  for (const id of ids) {
+    const [row] = await dbGlobal.select().from(mediaAssets).where(eq(mediaAssets.id, id)).limit(1);
+    if (!row || row.userId !== userId) {
+      throw createError({ statusCode: 400, statusMessage: "资源不存在或不属于当前用户" });
+    }
+    await assertAssetDeletableOrThrow(row);
+    await unlinkMediaFiles(row.storageKey, row.variantsJson);
+    await dbGlobal.delete(mediaAssets).where(eq(mediaAssets.id, id));
+  }
+
+  return ids.length;
+}
+
+export async function purgeAllDeletableOrphansGlobally(limit: number): Promise<number> {
+  const now = Date.now();
+  const whereClause = and(orphanCondition(), deletableTimeCondition(now));
+
+  const candidates = await dbGlobal
+    .select()
+    .from(mediaAssets)
+    .where(whereClause)
+    .orderBy(mediaAssets.id)
+    .limit(limit);
+
+  let deleted = 0;
+  for (const row of candidates) {
+    const [{ c }] = await dbGlobal
+      .select({ c: count() })
+      .from(postMediaRefs)
+      .where(eq(postMediaRefs.assetId, row.id));
+    if (c > 0) {
+      continue;
+    }
+    if (!isAssetDeletable(row)) {
+      continue;
+    }
+    await unlinkMediaFiles(row.storageKey, row.variantsJson);
+    await dbGlobal.delete(mediaAssets).where(eq(mediaAssets.id, row.id));
+    deleted += 1;
+  }
+
+  return deleted;
+}