diff --git a/packages/trpc/src/index.ts b/packages/trpc/src/index.ts
index 50acc58..0ede111 100644
--- a/packages/trpc/src/index.ts
+++ b/packages/trpc/src/index.ts
@@ -38,3 +38,7 @@ export {
     buildSearchQuery,
 } from "./services/scrape.service.js";
 export type { BangumiSearchHit } from "./services/scrape.service.js";
+
+// Playback / danmaku
+export { playbackService } from "./services/playback.service.js";
+export { danmakuService } from "./services/danmaku.service.js";
diff --git a/packages/trpc/src/services/danmaku.service.ts b/packages/trpc/src/services/danmaku.service.ts
new file mode 100644
index 0000000..e8ba06f
--- /dev/null
+++ b/packages/trpc/src/services/danmaku.service.ts
@@ -0,0 +1,114 @@
+import { createHash } from "node:crypto";
+import { danmakuCacheDao, mediaItemDao, mountDao } from "@app/dao";
+import type { DanmakuFetchOutput } from "@app/types";
+import { decryptSecret } from "./secret.js";
+import { createWebdav } from "./webdav-client.js";
+
+const CACHE_TTL_MS = 24 * 60 * 60 * 1000;
+
+function openApiBase(): string {
+    return process.env["OPEN_DANMAKU_API_BASE"] ?? "https://api.dandanplay.net";
+}
+
+function matchKeyFor(path: string, size: number): string {
+    return createHash("sha256").update(`${path}:${size}`).digest("hex");
+}
+
+/** 取 WebDAV 文件 hash（首 64KiB + 尺寸），用于开放网络识别 */
+async function remoteSampleHash(userId: string, mediaId: string): Promise<string | null> {
+    const item = await mediaItemDao.getByIdForUser(mediaId, userId);
+    if (!item?.mountId) return null;
+    const mount = await mountDao.getByIdForUser(item.mountId, userId);
+    if (!mount) return null;
+    const client = createWebdav({
+        baseUrl: mount.baseUrl,
+        username: mount.username ?? undefined,
+        password: mount.secretEnc ? decryptSecret(mount.secretEnc) : undefined,
+    });
+    try {
+        const abs = mount.rootPath.replace(/\/+$/, "") + item.path;
+        const stream = client.createReadStream(abs, { range: { start: 0, end: 65535 } });
+        const sample = await new Promise<Buffer>((resolve, reject) => {
+            const chunks: Buffer[] = [];
+            stream.on("data", (chunk: Buffer) => {
+                chunks.push(Buffer.isBuffer(chunk) ? chunk : Buffer.from(String(chunk)));
+            });
+            stream.on("end", () => resolve(Buffer.concat(chunks)));
+            stream.on("error", reject);
+        });
+        return createHash("sha256")
+            .update(sample)
+            .update(String(item.size))
+            .digest("hex")
+            .toUpperCase();
+    } catch {
+        return null;
+    }
+}
+
+async function fetchOpenNetworkXml(
+    path: string,
+    size: number,
+    hash: string | null,
+): Promise<string | null> {
+    const base = openApiBase();
+    try {
+        const identifyRes = await fetch(`${base}/api/v2/identify`, {
+            method: "POST",
+            headers: { "Content-Type": "application/json" },
+            body: JSON.stringify({
+                fileHash: hash ?? "",
+                fileSize: size,
+                fileName: path.split("/").pop() ?? path,
+            }),
+        });
+        if (!identifyRes.ok) return null;
+        const identified = (await identifyRes.json()) as {
+            isMatched?: boolean;
+            matched?: boolean;
+            episodeId?: number;
+        };
+        const episodeId = identified.episodeId;
+        if (!episodeId || !(identified.isMatched || identified.matched)) return null;
+        const commentRes = await fetch(`${base}/api/v2/comment/${episodeId}?withResponses=false`);
+        if (!commentRes.ok) return null;
+        const body = (await commentRes.json()) as { danmaku?: string; xml?: string };
+        return body.danmaku ?? body.xml ?? null;
+    } catch {
+        return null;
+    }
+}
+
+export const danmakuService = {
+    async fetch(userId: string, mediaItemId: string): Promise<DanmakuFetchOutput> {
+        const item = await mediaItemDao.getByIdForUser(mediaItemId, userId);
+        if (!item) return { ok: false, source: "none", xml: "", message: "媒体不存在" };
+
+        const matchKey = matchKeyFor(item.path, item.size);
+        const cached = await danmakuCacheDao.getValid(matchKey);
+        if (cached) {
+            return { ok: true, source: "cache", xml: cached.payload };
+        }
+
+        const hash = await remoteSampleHash(userId, mediaItemId);
+        const xml = await fetchOpenNetworkXml(item.path, item.size, hash);
+        if (!xml) {
+            return { ok: true, source: "none", xml: "", message: "开放网络未匹配到弹幕" };
+        }
+        await danmakuCacheDao.upsert({
+            matchKey,
+            payload: xml,
+            source: "open-network",
+            expiresAt: new Date(Date.now() + CACHE_TTL_MS),
+        });
+        return { ok: true, source: "open-network", xml };
+    },
+
+    /** 本地 XML 由前端解析后直接喂播放器；此处仅确认媒体存在并记 size 日志约束 */
+    async importMeta(userId: string, mediaItemId: string, byteSize: number): Promise<{ ok: true }> {
+        const item = await mediaItemDao.getByIdForUser(mediaItemId, userId);
+        if (!item) return Promise.reject(new Error("媒体不存在"));
+        if (byteSize > 20_000_000) return Promise.reject(new Error("XML 过大"));
+        return { ok: true };
+    },
+};
diff --git a/packages/trpc/src/services/playback.service.ts b/packages/trpc/src/services/playback.service.ts
new file mode 100644
index 0000000..6d3291d
--- /dev/null
+++ b/packages/trpc/src/services/playback.service.ts
@@ -0,0 +1,29 @@
+import { playbackProgressDao } from "@app/dao";
+import type { PlaybackReportInput } from "@app/types";
+
+export const playbackService = {
+    async report(userId: string, input: PlaybackReportInput) {
+        const row = await playbackProgressDao.upsert(
+            userId,
+            input.mediaItemId,
+            input.positionMs,
+            input.durationMs,
+        );
+        return {
+            mediaItemId: row.mediaItemId,
+            positionMs: row.positionMs,
+            durationMs: row.durationMs,
+            updatedAt: row.updatedAt,
+        };
+    },
+    async get(userId: string, mediaItemId: string) {
+        const row = await playbackProgressDao.get(userId, mediaItemId);
+        if (!row) return { mediaItemId, positionMs: 0, durationMs: 0, updatedAt: null };
+        return {
+            mediaItemId: row.mediaItemId,
+            positionMs: row.positionMs,
+            durationMs: row.durationMs,
+            updatedAt: row.updatedAt,
+        };
+    },
+};