diff --git a/vllm/disaggregated/pd_client.py b/vllm/disaggregated/pd_client.py
new file mode 100644
index 0000000000000..9d00a29030133
--- /dev/null
+++ b/vllm/disaggregated/pd_client.py
@@ -0,0 +1,323 @@
+# SPDX-License-Identifier: Apache-2.0
+
+import asyncio
+import os
+from collections.abc import AsyncGenerator, Mapping
+from typing import Optional
+
+import msgspec
+import zmq
+import zmq.asyncio
+
+from vllm.config import DecodingConfig, ModelConfig
+from vllm.core.scheduler import SchedulerOutputs
+from vllm.entrypoints.disaggregated.types import PDRequest, PDResponse
+from vllm.inputs.data import PromptType
+from vllm.inputs.preprocess import InputPreprocessor
+from vllm.logger import init_logger
+from vllm.lora.request import LoRARequest
+from vllm.model_executor.layers.sampler import SamplerOutput
+from vllm.outputs import CompletionOutput, PoolingRequestOutput, RequestOutput
+from vllm.pooling_params import PoolingParams
+from vllm.prompt_adapter.request import PromptAdapterRequest
+from vllm.sampling_params import BeamSearchParams, SamplingParams
+from vllm.transformers_utils.tokenizer import AnyTokenizer
+from vllm.transformers_utils.tokenizer_group import TokenizerGroup
+from vllm.utils import Device
+
+logger = init_logger(__name__)
+
+DEFAULT_MAX_TOKENS = 32000
+
+
+class PDClient:
+    """
+    PDEngine:
+        Equiavlent of AsyncLLM for P/D. Assumes there is
+        a Prefill and Decode service already running.
+
+        * TODO: actually handle errors and failure.
+        * TODO: support more than just text input.
+    """
+
+    def __init__(self, prefill_addr: str, decode_addr: str,
+                 connector_addr: str, model_name: str):
+        # Request queues.
+        self.queues: dict[str, asyncio.Queue] = {}
+
+        # Serialization encoder.
+        self.encoder = msgspec.msgpack.Encoder()
+
+        # ZMQ communication.
+        self.ctx = zmq.asyncio.Context()
+        self.to_decode = self.ctx.socket(zmq.constants.PUSH)
+        self.to_decode.bind(f"{decode_addr}")
+        self.to_prefill = self.ctx.socket(zmq.constants.PUSH)
+        self.to_prefill.bind(f"{prefill_addr}")
+        self.connector_addr = connector_addr
+        self.decode_addr = decode_addr
+        self.prefill_addr = prefill_addr
+
+        # Background loops (started on first generate()).
+        self.output_handler: Optional[asyncio.Task] = None
+        self.log_running: Optional[asyncio.Task] = None
+
+        # Dummy: needed for EngineClient Protocol.
+        # TODO: refactor EngineClient to avoid needing this.
+        self.model_config = ModelConfig(model=model_name,
+                                        tokenizer=model_name,
+                                        tokenizer_mode="auto",
+                                        trust_remote_code=False,
+                                        dtype="auto",
+                                        task="generate",
+                                        seed=42)
+
+        # Dummy: needed for EngineClient Protocol.
+        # TODO: refactor EngineClient to avoid needing this.
+        init_kwargs = dict(
+            tokenizer_id=self.model_config.tokenizer,
+            enable_lora=False,
+            max_num_seqs=1024,
+            max_loras=0,
+            max_input_length=None,
+            tokenizer_mode=self.model_config.tokenizer_mode,
+            trust_remote_code=self.model_config.trust_remote_code,
+            revision=self.model_config.tokenizer_revision,
+            truncation_side=self.model_config.truncation_side)
+        self.tokenizer = TokenizerGroup(**init_kwargs)
+
+    def shutdown(self):
+        if (ctx := self.ctx) is not None:
+            ctx.destroy(linger=0)
+        if (task := self.log_running) is not None:
+            task.cancel()
+        if (task := self.output_handler) is not None:
+            task.cancel()
+
+        ipc_paths = [self.connector_addr, self.decode_addr, self.prefill_addr]
+        for path in ipc_paths:
+            socket_path = path.replace("ipc://", "")
+            if os.path.exists(socket_path):
+                os.remove(socket_path)
+
+    async def _run_log_running(self):
+        logger.info("Running requests: %d", len(self.queues))
+        await asyncio.sleep(10.)
+
+    async def _run_output_handler(self):
+        """
+        Pull responses from Decode + Prefill engines and
+        distribute back to the generate() tasks.
+        """
+        decoder = msgspec.msgpack.Decoder(PDResponse)
+
+        socket: Optional[zmq.asyncio.Socket] = None
+        try:
+            socket = self.ctx.socket(zmq.constants.PULL)
+            socket.bind(self.connector_addr)
+
+            while True:
+                reponse_bytes = await socket.recv()
+                response = decoder.decode(reponse_bytes)
+                logger.debug("Got Response: %s", response.request_id)
+                self.queues[response.request_id].put_nowait(response)
+        except:
+            # TODO: actually handle failure and shutdown.
+            raise
+        finally:
+            if socket is not None:
+                socket.close(linger=0)
+
+    async def _prefill(
+        self,
+        request: PDRequest,
+        q: asyncio.Queue[PDResponse],
+    ):
+        # Send request to the prefill instance.
+        req_bytes = self.encoder.encode(request)
+        await self.to_prefill.send(req_bytes, copy=False)
+
+        # Wait for the prefill to be done.
+        response = await q.get()
+        assert response.request_id == request.request_id
+        if not response.success:
+            # TODO: actual error handling and shutdown.
+            raise Exception("Failed Prefill Request.")
+
+    async def _decode(
+        self,
+        request: PDRequest,
+        q: asyncio.Queue[PDResponse],
+    ) -> AsyncGenerator[PDRequest]:
+
+        # Send request to the decode instance.
+        req_bytes = self.encoder.encode(request)
+        await self.to_decode.send(req_bytes, copy=False)
+
+        # Iterate response queue and yield each response to caller..
+        finished = False
+        while not finished:
+            response = await q.get()
+            if not response.success:
+                # TODO: actual error handling and shutdown.
+                raise Exception("Failed Decode Request.")
+            finished = response.finish_reason is not None
+            yield response
+
+    def _to_request_output(
+        self,
+        pd_response: PDResponse,
+        prompt_token_ids: list[int],
+    ) -> RequestOutput:
+        finished = pd_response.finish_reason is not None
+        return RequestOutput(
+            request_id=pd_response.request_id,
+            prompt=None,
+            prompt_token_ids=prompt_token_ids,
+            prompt_logprobs=None,
+            outputs=[
+                CompletionOutput(index=0,
+                                 text=pd_response.text,
+                                 token_ids=pd_response.token_ids,
+                                 cumulative_logprob=None,
+                                 logprobs=None,
+                                 finish_reason=pd_response.finish_reason,
+                                 stop_reason=pd_response.stop_reason)
+            ],
+            finished=finished,
+        )
+
+    async def generate(
+        self,
+        prompt: PromptType,
+        sampling_params: SamplingParams,
+        request_id: str,
+        lora_request: Optional[LoRARequest] = None,
+        trace_headers: Optional[Mapping[str, str]] = None,
+        prompt_adapter_request: Optional[PromptAdapterRequest] = None,
+        priority: int = 0,
+    ) -> AsyncGenerator[RequestOutput]:
+        # Start loops on first request.
+        if self.output_handler is None:
+            self.output_handler = asyncio.create_task(
+                self._run_output_handler())
+            self.log_running = asyncio.create_task(self._run_log_running())
+
+        # TODO: Expand to support the full matrix.
+        if "prompt_token_ids" not in prompt:
+            raise NotImplementedError(
+                "We currently only support TokensPrompt for P/D!")
+        if lora_request is not None:
+            raise NotImplementedError(
+                "We currently do not support LoRA for P/D!")
+        if trace_headers is not None:
+            raise NotImplementedError(
+                "We currently do not support tracing for P/D!")
+        if prompt_adapter_request is not None:
+            raise NotImplementedError(
+                "We currently do not support prompt adapter for P/D!")
+        if priority != 0:
+            raise NotImplementedError(
+                "We currently do not support priority for P/D!")
+        if request_id in self.queues:
+            raise ValueError(f"Found duplicate request_id: {request_id}!")
+
+        # Queue to gather output from output_handler.
+        q: asyncio.Queue[PDResponse] = asyncio.Queue()
+        self.queues[request_id] = q
+
+        # (1) Perform the Prefill.
+        original_max_tokens = sampling_params.max_tokens
+        prompt_token_ids = prompt["prompt_token_ids"]
+        request = PDRequest(request_id=request_id,
+                            prompt_token_ids=prompt_token_ids,
+                            sampling_params=sampling_params)
+        request.sampling_params.max_tokens = 1
+        logger.debug("Sending Prefill: %s", request.request_id)
+        pd_response = await self._prefill(request, q)
+
+        # (2) Perform the Decodes.
+        logger.debug("Sending Decode: %s", request.request_id)
+        request.sampling_params.max_tokens = original_max_tokens
+        async for pd_response in self._decode(request, q):
+            logger.debug("Got Decode: %s", request.request_id)
+            yield self._to_request_output(pd_response, prompt_token_ids)
+
+    async def beam_search(
+        self,
+        prompt: PromptType,
+        request_id: str,
+        params: BeamSearchParams,
+    ) -> AsyncGenerator[RequestOutput, None]:
+        raise NotImplementedError
+
+    def encode(
+        self,
+        prompt: PromptType,
+        pooling_params: PoolingParams,
+        request_id: str,
+        lora_request: Optional[LoRARequest] = None,
+        trace_headers: Optional[Mapping[str, str]] = None,
+        priority: int = 0,
+    ) -> AsyncGenerator[PoolingRequestOutput, None]:
+        raise NotImplementedError
+
+    async def abort(self, request_id: str) -> None:
+        raise NotImplementedError
+
+    async def get_model_config(self) -> ModelConfig:
+        return self.model_config
+
+    async def get_decoding_config(self) -> DecodingConfig:
+        raise NotImplementedError
+
+    async def get_input_preprocessor(self) -> InputPreprocessor:
+        raise NotImplementedError
+
+    async def get_tokenizer(
+        self,
+        lora_request: Optional[LoRARequest] = None,
+    ) -> AnyTokenizer:
+        if lora_request is not None:
+            raise NotImplementedError(
+                "LoRA is not yet supported in the PDEngine.")
+        return self.tokenizer.get_lora_tokenizer(None)
+
+    async def is_tracing_enabled(self) -> bool:
+        return False
+
+    async def do_log_stats(
+        self,
+        scheduler_outputs: Optional[SchedulerOutputs] = None,
+        model_output: Optional[list[SamplerOutput]] = None,
+    ) -> None:
+        pass
+
+    async def check_health(self) -> None:
+        pass
+
+    async def start_profile(self) -> None:
+        raise NotImplementedError
+
+    async def stop_profile(self) -> None:
+        raise NotImplementedError
+
+    async def reset_prefix_cache(self,
+                                 device: Optional[Device] = None) -> None:
+        raise NotImplementedError
+
+    async def sleep(self, level: int = 1) -> None:
+        raise NotImplementedError
+
+    async def wake_up(self) -> None:
+        raise NotImplementedError
+
+    async def is_sleeping(self) -> bool:
+        return False
+
+    async def add_lora(self, lora_request: LoRARequest) -> None:
+        raise NotImplementedError
+
+    @property
+    def errored(self) -> bool:
+        return False
diff --git a/vllm/disaggregated/protocol.py b/vllm/disaggregated/protocol.py
new file mode 100644
index 0000000000000..dfc02263207ba
--- /dev/null
+++ b/vllm/disaggregated/protocol.py
@@ -0,0 +1,63 @@
+# SPDX-License-Identifier: Apache-2.0
+
+from typing import Optional
+
+import msgspec
+
+from vllm import SamplingParams
+from vllm.outputs import RequestOutput
+
+# NOTE FOR DEVELOPERS:
+# DO NOT USE PICKLE FOR THESE CLASSES. IN A MULTI NODE
+# SETUP WE WILL USE TCP. WE CANNOT USE PICKLE OTHERWISE
+# WE RISK REMOTE CODE EXECUTION FROM UNSTRUSTED USERS.
+
+
+class PDRequestType:
+    GENERATION = b"generation"
+    ABORT = b"abort"
+
+
+class PDGenerationRequest(msgspec.Struct):
+    request_id: str
+    prompt_token_ids: list[int]
+    sampling_params: SamplingParams
+    # TODO: support multimodal inputs.
+
+
+class PDAbortRequest(msgspec.Struct):
+    request_id: str
+
+
+class PDResponseType:
+    GENERATION = b"generation"
+    FAILURE = b"failure"
+
+
+class PDGenerationResponse(msgspec.Struct):
+    request_id: str
+    text: str
+    token_ids: list[int]
+    finish_reason: Optional[str] = None
+    stop_reason: Optional[str] = None
+    # TODO: support full protocol.
+    logprobs = None
+
+    @classmethod
+    def from_request_output(
+            self, request_output: RequestOutput) -> "PDGenerationResponse":
+        assert len(request_output.outputs) == 1, "Only support N=1 right now."
+        out = request_output.outputs[0]
+        return PDGenerationResponse(
+            request_id=request_output.request_id,
+            text=out.text,
+            token_ids=out.token_ids,
+            finish_reason=out.finish_reason,
+            stop_reason=out.stop_reason,
+        )
+
+
+class PDGenerationFailure(msgspec.Struct):
+    request_id: str
+    error_message: str
+    engine_dead: bool