diff --git a/app/api/routers/relay.py b/app/api/routers/relay.py
index aa7dd02..506cb81 100644
--- a/app/api/routers/relay.py
+++ b/app/api/routers/relay.py
@@ -214,6 +214,111 @@ async def relay_chat_completions(request: Request, db: Database = Depends(get_db
     )
 
 
+@router.post("/messages")
+async def relay_messages(request: Request, db: Database = Depends(get_db)):
+    """Anthropic 格式 POST /v1/messages：转发到 compute-engine。
+
+    鉴权与 chat 同规：Authorization: Bearer 或 x-api-key 均可（_auth_headers 已兼容）；
+    平台 JWT 登录态调用：按 Anthropic usage(input/output_tokens) 记账；
+    引擎 PAT 调用（第三方 Anthropic 客户端）：不额外记账，仅引擎计量。
+    流式：透传 SSE 并解析 message_delta.usage 记账。
+    """
+    try:
+        body: dict[str, Any] = await request.json()
+    except Exception as exc:  # noqa: BLE001
+        raise HTTPException(status_code=400, detail="Invalid JSON body") from exc
+
+    messages_url = f"{config.COMPUTE_BASE_URL.rstrip('/')}/v1/messages"
+    stream = bool(body.get("stream", False))
+    model = str(body.get("model") or "")
+    billing_user_id = await _resolve_billing_user(request, db)
+    headers = {**(await _auth_headers(request)), "Content-Type": "application/json"}
+    logger.info("[relay] messages model=%s stream=%s bytes=%d bill=%s", model, stream, len(json.dumps(body)), bool(billing_user_id))
+
+    client = httpx.AsyncClient(timeout=None)
+    upstream_request = client.build_request("POST", messages_url, json=body, headers=headers)
+
+    if not stream:
+        try:
+            upstream = await client.send(upstream_request)
+            payload = upstream.json() if upstream.content else None
+        except Exception:  # noqa: BLE001
+            await client.aclose()
+            raise HTTPException(status_code=502, detail="Upstream relay failed") from None
+        await client.aclose()
+        # Anthropic usage（input_tokens/output_tokens）→ 平台记账
+        if billing_user_id and isinstance(payload, dict) and payload.get("usage"):
+            await _bill_usage_anthropic(db, billing_user_id, model, payload.get("usage"))
+        return JSONResponse(status_code=upstream.status_code, content=payload)
+
+    try:
+        upstream = await client.send(upstream_request, stream=True)
+    except Exception:  # noqa: BLE001
+        await client.aclose()
+        raise HTTPException(status_code=502, detail="Upstream relay failed") from None
+
+    resp_headers: dict[str, str] = {}
+    if "content-type" in upstream.headers:
+        resp_headers["content-type"] = upstream.headers["content-type"]
+    if "x-request-id" in upstream.headers:
+        resp_headers["x-request-id"] = upstream.headers["x-request-id"]
+
+    if not billing_user_id:
+        return StreamingResponse(
+            upstream.aiter_raw(),
+            status_code=upstream.status_code,
+            media_type="text/event-stream",
+            headers=resp_headers,
+            background=BackgroundTask(client.aclose),
+        )
+
+    # 流式：透传 SSE 同时解析 usage（message_start.input_tokens + message_delta.output_tokens），结束后记账
+    async def _stream_with_billing():
+        usage: dict | None = None
+        try:
+            async for line in upstream.aiter_lines():
+                yield (line + "\n").encode("utf-8")
+                if line.startswith("data:"):
+                    payload = line[5:].strip()
+                    if payload:
+                        try:
+                            obj = json.loads(payload)
+                            if isinstance(obj, dict):
+                                if obj.get("type") == "message_start" and isinstance(obj.get("message"), dict):
+                                    usage = dict(obj["message"].get("usage") or {})
+                                elif obj.get("type") == "message_delta" and isinstance(obj.get("usage"), dict):
+                                    usage = {**(usage or {}), **obj["usage"]}
+                        except Exception:  # noqa: BLE001
+                            pass
+        finally:
+            try:
+                await client.aclose()
+            except Exception:  # noqa: BLE001
+                pass
+            if usage:
+                await _bill_usage_anthropic(db, billing_user_id, model, usage)
+
+    return StreamingResponse(
+        _stream_with_billing(),
+        status_code=upstream.status_code,
+        media_type="text/event-stream",
+        headers=resp_headers,
+    )
+
+
+async def _bill_usage_anthropic(db: Database, user_id: str, model: str, usage: dict) -> None:
+    """Anthropic usage（input_tokens/output_tokens）→ 平台记账（best-effort）。"""
+    try:
+        from ...services.compute_pricing_service import deduct_usage_post
+        await deduct_usage_post(
+            db, user_id, model,
+            int(usage.get("input_tokens") or usage.get("prompt_tokens") or 0),
+            int(usage.get("output_tokens") or usage.get("completion_tokens") or 0),
+        )
+    except Exception as exc:  # noqa: BLE001
+        logger.warning("[relay] messages billing failed user=%s model=%s err=%s", user_id, model, exc)
+
+
 async def _resolve_billing_user(request: Request, db: Database) -> str:
     """解析平台 JWT 登录态 → 平台 user_id；非 JWT（引擎 PAT）返回空串不记账。"""
     client_auth = (request.headers.get("Authorization", "") or "").strip()