feat: load-based scaling in SLA Planner (#6145)

Signed-off-by: hongkuanz <hongkuanz@nvidia.com>

components/src/dynamo/planner/README.md

@@ -19,5 +19,28 @@ limitations under the License.
 
 SLA-driven autoscaling controller for Dynamo inference graphs.
 
-- **User docs**: [docs/planner/](/docs/pages/components/planner/) (deployment, configuration, examples)
-- **Design docs**: [docs/pages/design-docs/planner-design.md](/docs/pages/design-docs/planner-design.md) (architecture, algorithms)
+## Scaling Modes
+
+The SLA Planner supports two scaling modes that can be used independently or together:
+
+### Throughput-Based Scaling
+
+Uses pre-deployment profiling data and traffic prediction to compute the number of prefill/decode replicas needed to meet TTFT and ITL SLA targets. Requires profiling data from the Dynamo profiler.
+
+### Load-Based Scaling (Experimental)
+
+Uses real-time per-worker load metrics (active prefill tokens, active KV blocks) from the router to make SLA-aware scaling decisions via online linear regression. Does not require profiling data. Responds quickly to traffic bursts.
+
+When both modes are enabled, throughput-based scaling provides a lower bound on replicas while load-based scaling handles real-time adjustments.
+
+### Support Matrix
+
+| Deployment Type | Throughput-Based | Load-Based (Experimental) |
+|-----------------|:----------------:|:-------------------------:|
+| Disaggregated   | Supported        | Supported                 |
+| Aggregated      | Unsupported      | Supported                 |
+
+## Documentation
+
+- **User docs**: [Planner Guide](../../../../docs/pages/components/planner/planner-guide.md) (deployment, configuration, examples)
+- **Design docs**: [Planner Design](../../../../docs/pages/design-docs/planner-design.md) (architecture, algorithms)

components/src/dynamo/planner/__init__.py

@@ -5,17 +5,12 @@ __all__ = [
     "PlannerConnector",
     "KubernetesConnector",
     "VirtualConnector",
-    "LoadPlannerDefaults",
     "SLAPlannerDefaults",
     "TargetReplica",
     "SubComponentType",
 ]
 # Import the classes
-from dynamo.planner.defaults import (
-    LoadPlannerDefaults,
-    SLAPlannerDefaults,
-    SubComponentType,
-)
+from dynamo.planner.defaults import SLAPlannerDefaults, SubComponentType
 from dynamo.planner.kubernetes_connector import KubernetesConnector, TargetReplica
 from dynamo.planner.planner_connector import PlannerConnector
 from dynamo.planner.virtual_connector import VirtualConnector

components/src/dynamo/planner/defaults.py

@@ -48,14 +48,6 @@ class BasePlannerDefaults:
     metric_reporting_prometheus_port = int(os.environ.get("PLANNER_PROMETHEUS_PORT", 0))
 
 
-class LoadPlannerDefaults(BasePlannerDefaults):
-    metric_pulling_interval = 10  # in seconds
-    decode_kv_scale_up_threshold = 0.9
-    decode_kv_scale_down_threshold = 0.5
-    prefill_queue_scale_up_threshold = 5.0
-    prefill_queue_scale_down_threshold = 0.2
-
-
 class SLAPlannerDefaults(BasePlannerDefaults):
     # Prometheus endpoint URL for pulling/querying metrics
     metric_pulling_prometheus_endpoint = os.environ.get(
@@ -81,6 +73,20 @@ class SLAPlannerDefaults(BasePlannerDefaults):
     no_correction = False  # disable correction factor, might be useful under some conditions like long cold start time
     mode = "disagg"  # ["disagg", "prefill", "decode"]
 
+    # Scaling mode flags
+    enable_throughput_scaling = True
+    enable_loadbased_scaling = False
+
+    # Load-based scaling settings
+    loadbased_router_metrics_url: Optional[
+        str
+    ] = None  # will be auto-discovered from the DGD in kubernetes mode if not provided
+    loadbased_adjustment_interval = 5  # in seconds, must be < adjustment_interval
+    loadbased_learning_window = 50  # sliding window size for regression
+    loadbased_scaling_down_sensitivity = 80  # 0-100
+    loadbased_metric_samples = 10  # number of samples per interval
+    loadbased_min_observations = 5  # cold start threshold
+
 
 class VllmComponentName:
     prefill_worker_k8s_name = "VllmPrefillWorker"

components/src/dynamo/planner/kubernetes_connector.py

@@ -278,6 +278,28 @@ class KubernetesConnector(PlannerConnector):
 
         return prefill_gpu_count, decode_gpu_count
 
+    def get_frontend_metrics_url(self, port: int = 8000) -> Optional[str]:
+        """Auto-discover the Frontend service's metrics URL from the DGD.
+
+        Iterates spec.services to find the service with componentType "frontend",
+        then constructs the in-cluster URL using the operator's naming convention:
+        http://{dgd_name}-{service_key_lowercase}:{port}/metrics
+
+        Returns:
+            The metrics URL string, or None if no frontend service is found.
+        """
+        deployment = self.kube_api.get_graph_deployment(self.graph_deployment_name)
+        services = deployment.get("spec", {}).get("services", {})
+
+        for service_key, service_spec in services.items():
+            if service_spec.get("componentType", "") == "frontend":
+                service_name = f"{self.graph_deployment_name}-{service_key.lower()}"
+                url = f"http://{service_name}:{port}/metrics"
+                logger.info(f"Auto-discovered frontend metrics URL: {url}")
+                return url
+
+        return None
+
     async def wait_for_deployment_ready(self):
         """Wait for the deployment to be ready"""
         await self.kube_api.wait_for_graph_deployment_ready(

components/src/dynamo/planner/planner_sla.py

@@ -13,13 +13,20 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import argparse
 import asyncio
 import logging
 
 from pydantic import BaseModel
 
-from dynamo.planner.utils.planner_argparse import create_sla_planner_parser
-from dynamo.planner.utils.planner_core import start_sla_planner
+from dynamo.planner.utils.agg_planner import AggPlanner
+from dynamo.planner.utils.decode_planner import DecodePlanner
+from dynamo.planner.utils.disagg_planner import DisaggPlanner
+from dynamo.planner.utils.planner_argparse import (
+    create_sla_planner_parser,
+    validate_sla_planner_args,
+)
+from dynamo.planner.utils.prefill_planner import PrefillPlanner
 from dynamo.runtime import DistributedRuntime, dynamo_worker
 
 logger = logging.getLogger(__name__)
@@ -33,6 +40,24 @@ class RequestType(BaseModel):
     text: str
 
 
+async def start_sla_planner(runtime: DistributedRuntime, args: argparse.Namespace):
+    validate_sla_planner_args(args)
+
+    mode = getattr(args, "mode", "disagg")
+    if mode == "disagg":
+        planner = DisaggPlanner(runtime, args)
+    elif mode == "prefill":
+        planner = PrefillPlanner(runtime, args)
+    elif mode == "decode":
+        planner = DecodePlanner(runtime, args)
+    elif mode == "agg":
+        planner = AggPlanner(runtime, args)
+    else:
+        raise ValueError(f"Invalid planner mode: {mode}")
+    await planner._async_init()
+    await planner.run()
+
+
 @dynamo_worker()
 async def init_planner(runtime: DistributedRuntime, args):
     await asyncio.sleep(INIT_PLANNER_START_DELAY)

components/src/dynamo/planner/utils/agg_planner.py

+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+import argparse
+import asyncio
+import logging
+from typing import Optional
+
+from dynamo.planner import SubComponentType, TargetReplica
+from dynamo.planner.utils.load_based_regression import LoadBasedRegressionModel
+from dynamo.planner.utils.planner_core import (
+    BasePlanner,
+    PlannerPrometheusMetrics,
+    PlannerSharedState,
+    _apply_component_gpu_budget,
+    _initialize_gpu_counts,
+)
+from dynamo.planner.utils.prometheus import CachedLoadMetrics
+from dynamo.runtime import DistributedRuntime
+from dynamo.runtime.logging import configure_dynamo_logging
+
+configure_dynamo_logging()
+logger = logging.getLogger(__name__)
+
+
+class AggPlanner:
+    """Aggregated planner: load-based scaling only, single engine type.
+
+    In aggregated mode, engines handle both prefill and decode (chunked prefill).
+    Engine metrics are labeled "decode" by the router.
+
+    Scaling logic:
+    - TTFT and ITL regression models are both maintained.
+    - Regression uses per-worker time-averaged metrics (not latest snapshot)
+      because chunked prefill adds noise to instantaneous TTFT/ITL.
+    - Scale up if either prefill or decode target is exceeded.
+    - Scale down if both prefill and decode are below their boundaries.
+    """
+
+    # Engine metrics from agg workers are labeled "decode" by the router
+    ENGINE_WORKER_TYPE = "decode"
+
+    def __init__(
+        self, runtime: Optional[DistributedRuntime], args: argparse.Namespace
+    ) -> None:
+        self.args = args
+        self.shared_state = PlannerSharedState()
+
+        if getattr(args, "enable_throughput_scaling", False):
+            raise ValueError(
+                "Aggregated planner only supports load-based scaling. "
+                "Please use --disable-throughput-scaling or do not set --enable-throughput-scaling."
+            )
+        if not getattr(args, "enable_loadbased_scaling", False):
+            raise ValueError("Aggregated planner requires --enable-loadbased-scaling.")
+
+        prometheus_metrics = PlannerPrometheusMetrics()
+
+        # Use a single BasePlanner instance for infra (connector, prometheus, etc.)
+        # We use DECODE component_type because engine metrics are labeled "decode"
+        self.planner = BasePlanner(
+            runtime,
+            args,
+            shared_state=self.shared_state,
+            prometheus_metrics=prometheus_metrics,
+            start_prometheus_server=True,
+        )
+        # Override: agg planner uses component_type DECODE for metrics fetching
+        self.planner.component_type = SubComponentType.DECODE
+
+        # Create both regression models (agg needs both TTFT and ITL)
+        self.ttft_regression = LoadBasedRegressionModel(
+            window_size=args.loadbased_learning_window,
+            min_observations=args.loadbased_min_observations,
+        )
+        self.itl_regression = LoadBasedRegressionModel(
+            window_size=args.loadbased_learning_window,
+            min_observations=args.loadbased_min_observations,
+        )
+
+        self.cached_load_metrics = CachedLoadMetrics()
+
+    async def _async_init(self):
+        await self.planner._async_init()
+
+    async def run(self):
+        if not self.args.no_operation:
+            logger.info("Validating deployment...")
+            # Agg mode: only decode component exists (engines serve both P and D)
+            await self.planner.connector.validate_deployment(
+                prefill_component_name=None,
+                decode_component_name=self.planner.decode_component_name,
+                require_prefill=False,
+                require_decode=True,
+            )
+            logger.info("Successfully validated the deployment")
+
+            _initialize_gpu_counts(
+                self.args,
+                self.planner.connector,
+                require_prefill=False,
+                require_decode=True,
+            )
+
+            await self.planner.connector.wait_for_deployment_ready()
+
+        # Model name discovery runs in all modes (needed for metrics collection)
+        if not self.args.no_operation:
+            model_name = await self.planner._get_model_name(
+                require_prefill=False, require_decode=True
+            )
+            logger.info(f"Detected model name from deployment: {model_name}")
+            self.planner.model_name = model_name.lower()
+        else:
+            model_name = getattr(self.args, "model_name", None)
+            if not model_name:
+                raise ValueError(
+                    "Model name is required in no-operation mode. "
+                    "Please provide --model-name."
+                )
+            self.planner.model_name = model_name.lower()
+
+        loops = [
+            self._load_loop(),
+            self.planner.prometheus_engine_client.run_sampling_loop(
+                self.args.loadbased_metric_samples,
+                self.args.loadbased_adjustment_interval,
+            ),
+        ]
+        await asyncio.gather(*loops)
+
+    async def _observe_engine_load_stats(self) -> None:
+        """Fetch metrics and update regression models using per-worker time-averaged data."""
+        result = self.planner.prometheus_engine_client.get_recent_and_averaged_metrics(
+            self.ENGINE_WORKER_TYPE
+        )
+        if result is None:
+            logger.warning(
+                f"No per-worker metrics available yet for {self.ENGINE_WORKER_TYPE} (buffer empty)"
+            )
+            return
+
+        recent, per_worker_averaged, cluster_averaged = result
+        self.cached_load_metrics = CachedLoadMetrics(
+            recent=recent,
+            per_worker_averaged=per_worker_averaged,
+            cluster_averaged=cluster_averaged,
+        )
+
+        # Agg uses per-worker time-averaged metrics for regression
+        # because chunked prefill adds noise to instantaneous TTFT/ITL
+        for wid, m in per_worker_averaged.items():
+            # TTFT regression: (active_prefill_tokens + ISL) -> TTFT
+            active_prefill = m.get("active_prefill_tokens", 0.0)
+            last_isl = m.get("last_isl", 0.0)
+            last_ttft = m.get("last_ttft", 0.0)
+            if last_ttft > 0 and last_isl > 0:
+                x = active_prefill + last_isl
+                y = last_ttft * 1000  # seconds -> ms
+                logger.info(
+                    f"Agg Worker {wid} prefill observation: TTFT {y:.2f}ms @ tokens {x:.2f}"
+                )
+                self.ttft_regression.add_observation(x, y)
+
+            # ITL regression: active_decode_blocks -> ITL
+            active_decode = m.get("active_decode_blocks", 0.0)
+            last_itl = m.get("last_itl", 0.0)
+            if last_itl > 0 and active_decode > 0:
+                x = active_decode
+                y = last_itl * 1000  # seconds -> ms
+                logger.info(
+                    f"Agg Worker {wid} decode observation: ITL {y:.2f}ms @ blocks {x:.2f}"
+                )
+                self.itl_regression.add_observation(x, y)
+
+    def _prefill_scaling_decision(self, num_workers: int) -> Optional[str]:
+        """Returns "up", "down", or None for prefill dimension."""
+        if not self.cached_load_metrics.recent:
+            return None
+        if not self.ttft_regression.has_sufficient_data():
+            logger.info(
+                f"TTFT regression: insufficient data ({self.ttft_regression.num_observations}"
+                f"/{self.ttft_regression.min_observations}), skipping"
+            )
+            return None
+
+        x_sla = self.ttft_regression.predict_x_from_sla(self.args.ttft)
+        if x_sla is None:
+            return None
+
+        recent = self.cached_load_metrics.recent
+        cluster_averaged = self.cached_load_metrics.cluster_averaged
+        avg_isl = cluster_averaged.get("last_isl", 0.0)
+        target = x_sla - avg_isl
+
+        if target <= 0:
+            logger.warning(
+                f"Agg TTFT SLA unachievable at current ISL: x_sla={x_sla:.1f}, "
+                f"avg_isl={avg_isl:.1f}, skipping prefill scaling decision"
+            )
+            return None
+
+        logger.info(
+            f"Agg prefill: x_sla={x_sla:.1f}, avg_isl={avg_isl:.1f}, "
+            f"target_active_tokens={target:.1f}, workers={num_workers}"
+        )
+
+        # Scale up: ALL workers above target
+        if all(m.get("active_prefill_tokens", 0.0) > target for m in recent.values()):
+            return "up"
+
+        # Scale down: ALL workers below boundary
+        if num_workers > 1:
+            sensitivity = self.args.loadbased_scaling_down_sensitivity / 100.0
+            boundary = target * (num_workers - 1) / num_workers * sensitivity
+            if all(
+                m.get("active_prefill_tokens", 0.0) < boundary for m in recent.values()
+            ):
+                return "down"
+
+        return None
+
+    def _decode_scaling_decision(self, num_workers: int) -> Optional[str]:
+        """Returns "up", "down", or None for decode dimension."""
+        if not self.cached_load_metrics.recent:
+            return None
+        if not self.itl_regression.has_sufficient_data():
+            logger.info(
+                f"ITL regression: insufficient data ({self.itl_regression.num_observations}"
+                f"/{self.itl_regression.min_observations}), skipping"
+            )
+            return None
+
+        x_sla = self.itl_regression.predict_x_from_sla(self.args.itl)
+        if x_sla is None:
+            return None
+
+        if x_sla <= 0:
+            logger.warning(
+                f"Agg ITL SLA unachievable: x_sla={x_sla:.1f}, "
+                "skipping decode scaling decision"
+            )
+            return None
+
+        recent = self.cached_load_metrics.recent
+
+        logger.info(f"Agg decode: x_sla={x_sla:.1f}, workers={num_workers}")
+
+        # Scale up: ALL workers above target
+        if all(m.get("active_decode_blocks", 0.0) > x_sla for m in recent.values()):
+            return "up"
+
+        # Scale down: ALL workers below boundary
+        # TODO: should we strictly enforce all workers below boundary?
+        # how about user-configurable percentage?
+        if num_workers > 1:
+            sensitivity = self.args.loadbased_scaling_down_sensitivity / 100.0
+            boundary = x_sla * (num_workers - 1) / num_workers * sensitivity
+            if all(
+                m.get("active_decode_blocks", 0.0) < boundary for m in recent.values()
+            ):
+                return "down"
+
+        return None
+
+    async def _load_loop(self) -> None:
+        """Load-based scaling loop for aggregated mode."""
+        while True:
+            await asyncio.sleep(self.args.loadbased_adjustment_interval)
+            logger.info("New agg load-based adjustment interval started!")
+
+            # Query DGD for fresh worker counts
+            _, num_d, _ = await self.planner.get_workers_info(
+                require_prefill=False, require_decode=True
+            )
+            self.shared_state.num_d_workers = num_d
+            num_workers = num_d
+
+            # Observe per-worker metrics
+            await self._observe_engine_load_stats()
+
+            # Reconcile worker counts
+            prom_count = len(self.cached_load_metrics.recent)
+            if prom_count != num_workers:
+                logger.warning(
+                    f"Worker count mismatch: DGD reports {num_workers}, "
+                    f"router metrics reports {prom_count}. Skipping."
+                )
+                continue
+
+            if not self.cached_load_metrics.recent:
+                continue
+
+            # Make scaling decisions separately for prefill and decode
+            p_decision = self._prefill_scaling_decision(num_workers)
+            d_decision = self._decode_scaling_decision(num_workers)
+
+            logger.info(
+                f"Agg scaling decisions: prefill={p_decision}, decode={d_decision}"
+            )
+
+            # Scale up if EITHER needs scale up
+            # Scale down if BOTH need scale down
+            if p_decision == "up" or d_decision == "up":
+                desired = num_workers + 1
+            elif p_decision == "down" and d_decision == "down":
+                desired = num_workers - 1
+            else:
+                logger.info("Agg scaling: no scaling needed")
+                continue
+
+            desired = max(desired, self.args.min_endpoint)
+            desired = _apply_component_gpu_budget(
+                desired, self.args.decode_engine_num_gpu, self.args
+            )
+
+            logger.info(f"Agg load-based scaling: {num_workers} -> {desired}")
+
+            if (
+                self.planner.prometheus_port != 0
+                and self.planner.prometheus_metrics is not None
+            ):
+                self.planner.prometheus_metrics.predicted_num_d.set(desired)
+
+            if not self.args.no_operation:
+                target_replicas = [
+                    TargetReplica(
+                        sub_component_type=SubComponentType.DECODE,
+                        component_name=self.planner.decode_component_name,
+                        desired_replicas=desired,
+                    )
+                ]
+                await self.planner.connector.set_component_replicas(
+                    target_replicas, blocking=True
+                )

components/src/dynamo/planner/utils/decode_planner.py

+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+import logging
+import math
+from typing import Optional
+
+from dynamo.planner import SubComponentType
+from dynamo.planner.utils.planner_core import BasePlanner
+from dynamo.runtime.logging import configure_dynamo_logging
+
+configure_dynamo_logging()
+logger = logging.getLogger(__name__)
+
+
+class DecodePlanner(BasePlanner):
+    component_type = SubComponentType.DECODE
+
+    def loadbased_plan_adjustment(self) -> Optional[int]:
+        """Load-based scaling decision for decode. Returns desired_replicas or None."""
+        if not self.itl_regression.has_sufficient_data():
+            logger.info(
+                f"ITL regression: insufficient data ({self.itl_regression.num_observations}"
+                f"/{self.itl_regression.min_observations}), skipping load-based scaling"
+            )
+            return None
+
+        x_sla = self.itl_regression.predict_x_from_sla(self.args.itl)
+        if x_sla is None:
+            return None
+
+        if x_sla <= 0:
+            logger.warning(
+                f"ITL SLA unachievable: x_sla={x_sla:.1f}, "
+                "skipping load-based decode scaling"
+            )
+            return None
+
+        if not self.cached_load_metrics.recent:
+            return None
+
+        recent = self.cached_load_metrics.recent
+
+        num_workers = self.shared_state.num_d_workers
+        if num_workers == 0:
+            return None
+
+        logger.info(
+            f"Load-based decode: x_sla={x_sla:.1f}, workers={num_workers}, "
+            f"slope={self.itl_regression.slope:.6f}, intercept={self.itl_regression.intercept:.3f}"
+        )
+
+        # Scale up: ALL workers above target (use recent metrics)
+        all_above = all(
+            m.get("active_decode_blocks", 0.0) > x_sla for m in recent.values()
+        )
+        if all_above:
+            logger.info(
+                f"Load-based decode: ALL workers above target ({x_sla:.1f}), "
+                f"scaling up to {num_workers + 1}"
+            )
+            return num_workers + 1
+
+        # Scale down: ALL workers below boundary (use recent metrics)
+        if num_workers > 1:
+            sensitivity = self.args.loadbased_scaling_down_sensitivity / 100.0
+            boundary = x_sla * (num_workers - 1) / num_workers * sensitivity
+            all_below = all(
+                m.get("active_decode_blocks", 0.0) < boundary for m in recent.values()
+            )
+            if all_below:
+                logger.info(
+                    f"Load-based decode: ALL workers below boundary ({boundary:.1f}), "
+                    f"scaling down to {num_workers - 1}"
+                )
+                return num_workers - 1
+
+        return None
+
+    def _update_correction_factor(self) -> bool:
+        if self.shared_state.num_d_workers == 0:
+            logger.warning(
+                "No decode workers found for correction factor, skipping correction update"
+            )
+            return True
+        expect_itl = self.decode_interpolator.interpolate_itl(
+            concurrency=self.last_metrics.num_req  # type: ignore
+            / self.shared_state.num_d_workers
+            * self.last_metrics.request_duration  # type: ignore
+            / self.args.adjustment_interval,
+            context_length=self.last_metrics.isl + self.last_metrics.osl / 2,  # type: ignore
+        )
+        self.d_correction_factor = self.last_metrics.itl / expect_itl
+        logger.info(f"Correction factor (decode ITL): {self.d_correction_factor:.3f}")
+        if self.prometheus_port != 0 and self.prometheus_metrics is not None:
+            self.prometheus_metrics.d_correction_factor.set(self.d_correction_factor)
+        return True
+
+    def _compute_replica_requirements(
+        self, next_num_req: float, next_isl: float, next_osl: float
+    ) -> int:
+        if self.d_correction_factor <= 0:
+            logger.warning(
+                f"d_correction_factor is {self.d_correction_factor}, using default value of 1.0"
+            )
+            corrected_itl = self.args.itl
+        else:
+            corrected_itl = self.args.itl / self.d_correction_factor
+        (
+            pred_decode_thpt_per_gpu,
+            _,
+            _,
+        ) = self.decode_interpolator.find_best_throughput_per_gpu(
+            itl=corrected_itl, context_length=next_isl + next_osl / 2
+        )
+        if pred_decode_thpt_per_gpu <= 0:
+            logger.warning(
+                f"pred_decode_thpt_per_gpu is {pred_decode_thpt_per_gpu} "
+                "(no throughput satisfies ITL target), falling back to min_endpoint"
+            )
+            return self.args.min_endpoint
+        pred_decode_throughput = next_num_req * next_osl / self.args.adjustment_interval
+        next_num_d = math.ceil(
+            pred_decode_throughput
+            / pred_decode_thpt_per_gpu
+            / self.args.decode_engine_num_gpu
+        )
+        next_num_d = max(next_num_d, self.args.min_endpoint)
+        logger.info(
+            f"Decode calculation: {pred_decode_throughput:.2f}(d_thpt) / "
+            f"{pred_decode_thpt_per_gpu * self.args.decode_engine_num_gpu:.2f}(d_engine_cap) = "
+            f"{next_num_d}(num_d)"
+        )
+        return next_num_d
+
+    def update_predicted_replicas_metric(self, desired_replicas: int) -> None:
+        if self.prometheus_port != 0 and self.prometheus_metrics is not None:
+            self.prometheus_metrics.predicted_num_d.set(desired_replicas)

components/src/dynamo/planner/utils/disagg_planner.py

+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+import argparse
+import asyncio
+import logging
+import time
+from typing import Optional
+
+from dynamo.planner import SubComponentType, TargetReplica
+from dynamo.planner.utils.decode_planner import DecodePlanner
+from dynamo.planner.utils.planner_core import (
+    PlannerPrometheusMetrics,
+    PlannerSharedState,
+    _apply_global_gpu_budget,
+    _initialize_gpu_counts,
+)
+from dynamo.planner.utils.prefill_planner import PrefillPlanner
+from dynamo.runtime import DistributedRuntime
+from dynamo.runtime.logging import configure_dynamo_logging
+
+configure_dynamo_logging()
+logger = logging.getLogger(__name__)
+
+
+class DisaggPlanner:
+    def __init__(
+        self, runtime: Optional[DistributedRuntime], args: argparse.Namespace
+    ) -> None:
+        self.args = args
+        self.shared_state = PlannerSharedState()
+        prometheus_metrics = PlannerPrometheusMetrics()
+
+        self.enable_throughput = getattr(args, "enable_throughput_scaling", True)
+        self.enable_loadbased = getattr(args, "enable_loadbased_scaling", False)
+
+        self.prefill_planner = PrefillPlanner(
+            runtime,
+            args,
+            shared_state=self.shared_state,
+            prometheus_metrics=prometheus_metrics,
+            start_prometheus_server=True,
+        )
+        self.decode_planner = DecodePlanner(
+            runtime,
+            args,
+            shared_state=self.shared_state,
+            prometheus_metrics=prometheus_metrics,
+            prometheus_traffic_client=getattr(
+                self.prefill_planner, "prometheus_traffic_client", None
+            ),
+            prometheus_engine_client=getattr(
+                self.prefill_planner, "prometheus_engine_client", None
+            ),
+            connector=getattr(self.prefill_planner, "connector", None),
+            start_prometheus_server=False,
+        )
+
+    async def _async_init(self):
+        # Prefill/Decode share the same connector instance in disagg mode.
+        await self.prefill_planner._async_init()
+
+    async def run(self):
+        if not self.args.no_operation:
+            logger.info("Validating deployment...")
+            await self.prefill_planner.connector.validate_deployment(
+                prefill_component_name=self.prefill_planner.prefill_component_name,
+                decode_component_name=self.prefill_planner.decode_component_name,
+                require_prefill=True,
+                require_decode=True,
+            )
+            logger.info("Successfully validated the deployment")
+
+            # Initialize GPU counts
+            _initialize_gpu_counts(
+                self.args,
+                self.prefill_planner.connector,
+                require_prefill=True,
+                require_decode=True,
+            )
+
+            await self.prefill_planner.connector.wait_for_deployment_ready()
+
+        # Model name discovery runs in all modes (needed for metrics collection)
+        if not self.args.no_operation:
+            model_name = await self.prefill_planner._get_model_name(
+                require_prefill=True, require_decode=True
+            )
+            logger.info(f"Detected model name from deployment: {model_name}")
+            model_name = model_name.lower()
+        else:
+            model_name = getattr(self.args, "model_name", None)
+            if not model_name:
+                raise ValueError(
+                    "Model name is required in no-operation mode. "
+                    "Please provide --model-name."
+                )
+            model_name = model_name.lower()
+        self.prefill_planner.model_name = model_name
+        self.decode_planner.model_name = model_name
+
+        self.shared_state.last_adjustment_time = time.time()
+        self.shared_state.last_loadbased_adjustment_time = time.time()
+
+        # Build list of concurrent loops based on enabled scaling modes
+        loops = []
+        if self.enable_throughput:
+            loops.append(self._throughput_loop())
+        if self.enable_loadbased:
+            loops.append(self._load_loop())
+            loops.append(
+                self.prefill_planner.prometheus_engine_client.run_sampling_loop(
+                    self.args.loadbased_metric_samples,
+                    self.args.loadbased_adjustment_interval,
+                )
+            )
+
+        await asyncio.gather(*loops)
+
+    async def _throughput_loop(self) -> None:
+        """Throughput-based scaling loop for disagg mode."""
+        while True:
+            current_time = time.time()
+
+            if (
+                current_time - self.shared_state.last_adjustment_time
+                >= self.args.adjustment_interval
+            ):
+                self.shared_state.last_adjustment_time = time.time()
+                logger.info("New throughput adjustment interval started!")
+
+                await self.prefill_planner.observe_traffic_stats(
+                    require_prefill=True, require_decode=True
+                )
+                self.decode_planner.update_predictors_from_metrics(
+                    self.shared_state.last_metrics
+                )
+                next_num_p = self.prefill_planner.plan_adjustment()
+                next_num_d = self.decode_planner.plan_adjustment()
+                if next_num_p is None or next_num_d is None:
+                    await asyncio.sleep(self.args.adjustment_interval / 10)
+                    continue
+
+                if self.enable_loadbased:
+                    # When load-based is also enabled: just set lower bounds
+                    self.shared_state.throughput_lower_bound_p = next_num_p
+                    self.shared_state.throughput_lower_bound_d = next_num_d
+                    logger.info(
+                        f"Throughput lower bounds set: prefill={next_num_p}, decode={next_num_d}"
+                    )
+                else:
+                    # Throughput-only: apply scaling directly
+                    next_num_p, next_num_d = _apply_global_gpu_budget(
+                        next_num_p, next_num_d, self.args
+                    )
+                    self.prefill_planner.update_predicted_replicas_metric(next_num_p)
+                    self.decode_planner.update_predicted_replicas_metric(next_num_d)
+
+                    if not self.args.no_operation:
+                        target_replicas = [
+                            TargetReplica(
+                                sub_component_type=SubComponentType.PREFILL,
+                                component_name=self.prefill_planner.prefill_component_name,
+                                desired_replicas=next_num_p,
+                            ),
+                            TargetReplica(
+                                sub_component_type=SubComponentType.DECODE,
+                                component_name=self.prefill_planner.decode_component_name,
+                                desired_replicas=next_num_d,
+                            ),
+                        ]
+                        await self.prefill_planner.connector.set_component_replicas(
+                            target_replicas, blocking=False
+                        )
+
+            await asyncio.sleep(self.args.adjustment_interval / 10)
+
+    async def _load_loop(self) -> None:
+        """Load-based scaling loop for disagg mode at shorter interval."""
+        while True:
+            await asyncio.sleep(self.args.loadbased_adjustment_interval)
+            logger.info("New load-based adjustment interval started!")
+
+            # Query DGD for fresh worker counts
+            num_p, num_d, _ = await self.prefill_planner.get_workers_info(
+                require_prefill=True, require_decode=True
+            )
+            self.shared_state.num_p_workers = num_p
+            self.shared_state.num_d_workers = num_d
+
+            # Observe per-worker metrics from router
+            await self.prefill_planner.observe_engine_load_stats()
+            await self.decode_planner.observe_engine_load_stats()
+
+            # Reconcile DGD worker counts with router Prometheus counts
+            p_prom_count = len(self.prefill_planner.cached_load_metrics.recent)
+            d_prom_count = len(self.decode_planner.cached_load_metrics.recent)
+            if p_prom_count != num_p or d_prom_count != num_d:
+                logger.warning(
+                    f"Worker count mismatch: DGD reports P={num_p}, D={num_d}; "
+                    f"router metrics reports P={p_prom_count}, D={d_prom_count}. "
+                    "Skipping load-based scaling adjustment."
+                )
+                continue
+
+            # Scale prefill and decode independently
+            p_desired = self.prefill_planner.loadbased_plan_adjustment()
+            d_desired = self.decode_planner.loadbased_plan_adjustment()
+
+            final_p = (
+                p_desired if p_desired is not None else self.shared_state.num_p_workers
+            )
+            final_d = (
+                d_desired if d_desired is not None else self.shared_state.num_d_workers
+            )
+
+            if (
+                final_p == self.shared_state.num_p_workers
+                and final_d == self.shared_state.num_d_workers
+            ):
+                logger.info("Load-based scaling: no scaling needed")
+                continue
+
+            # Enforce lower bounds from throughput-based
+            if self.enable_throughput:
+                final_p = max(final_p, self.shared_state.throughput_lower_bound_p)
+                final_d = max(final_d, self.shared_state.throughput_lower_bound_d)
+
+            # Apply GPU budget
+            final_p, final_d = _apply_global_gpu_budget(final_p, final_d, self.args)
+
+            logger.info(
+                f"Load-based disagg scaling: prefill {self.shared_state.num_p_workers}->{final_p}, "
+                f"decode {self.shared_state.num_d_workers}->{final_d}"
+            )
+
+            self.prefill_planner.update_predicted_replicas_metric(final_p)
+            self.decode_planner.update_predicted_replicas_metric(final_d)
+
+            if not self.args.no_operation:
+                target_replicas = [
+                    TargetReplica(
+                        sub_component_type=SubComponentType.PREFILL,
+                        component_name=self.prefill_planner.prefill_component_name,
+                        desired_replicas=final_p,
+                    ),
+                    TargetReplica(
+                        sub_component_type=SubComponentType.DECODE,
+                        component_name=self.prefill_planner.decode_component_name,
+                        desired_replicas=final_d,
+                    ),
+                ]
+                await self.prefill_planner.connector.set_component_replicas(
+                    target_replicas, blocking=True
+                )

components/src/dynamo/planner/utils/dryrun.py

@@ -4,18 +4,24 @@
 import argparse
 from typing import Optional
 
+from dynamo.planner.utils.decode_planner import DecodePlanner
 from dynamo.planner.utils.dryrun_plot_utils import create_dryrun_plot
 from dynamo.planner.utils.planner_core import (
-    DecodePlanner,
     PlannerSharedState,
-    PrefillPlanner,
     _apply_component_gpu_budget,
     _apply_global_gpu_budget,
 )
+from dynamo.planner.utils.prefill_planner import PrefillPlanner
 from dynamo.planner.utils.trace_data_extractor import extract_metrics_from_mooncake
 
 
 def run_sla_planner_dryrun(args: argparse.Namespace) -> None:
+    if getattr(args, "enable_loadbased_scaling", False):
+        raise ValueError(
+            "Load-based scaling is not supported in dryrun mode. "
+            "Disable --enable-loadbased-scaling to use dryrun."
+        )
+
     # Dryrun mode: use defaults if GPU counts not provided (no DGD available)
     if args.prefill_engine_num_gpu is None:
         args.prefill_engine_num_gpu = 1
@@ -90,7 +96,7 @@ def run_sla_planner_dryrun(args: argparse.Namespace) -> None:
             compute_safe_p_thpt(args.start_num_p, isl[0], args.ttft)
             * args.adjustment_interval
         ]
-        prefill_planner.dryrun_observe_metrics(rr[0], isl[0], osl[0])
+        prefill_planner.dryrun_observe_traffic_stats(rr[0], isl[0], osl[0])
     else:
         num_p = [0]
         p_thpt = [0]
@@ -103,7 +109,7 @@ def run_sla_planner_dryrun(args: argparse.Namespace) -> None:
             compute_safe_d_thpt(args.start_num_d, isl[0], osl[0], args.itl)
             * args.adjustment_interval
         ]
-        decode_planner.dryrun_observe_metrics(rr[0], isl[0], osl[0])
+        decode_planner.dryrun_observe_traffic_stats(rr[0], isl[0], osl[0])
     else:
         num_d = [0]
         d_thpt = [0]
@@ -152,7 +158,7 @@ def run_sla_planner_dryrun(args: argparse.Namespace) -> None:
         # update load predictor
         for planner in [prefill_planner, decode_planner]:
             if planner is not None:
-                planner.dryrun_observe_metrics(
+                planner.dryrun_observe_traffic_stats(
                     metric["request_count"], metric["avg_isl"], metric["avg_osl"]
                 )
 

components/src/dynamo/planner/utils/load_based_regression.py

+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+from collections import deque
+from typing import Optional
+
+import numpy as np
+from sklearn.linear_model import LinearRegression
+
+from dynamo.runtime.logging import configure_dynamo_logging
+
+configure_dynamo_logging()
+logger = logging.getLogger(__name__)
+
+
+class LoadBasedRegressionModel:
+    """Sliding window linear regression for load-based scaling.
+
+    Maintains a fixed-size window of (X, y) observations and provides:
+    - Forward prediction: y = mx + b (given X, predict latency)
+    - Reverse prediction: X = (y - b) / m (given target SLA, find max load)
+
+    Used to map:
+    - Prefill: (active_prefill_tokens + ISL) -> TTFT
+    - Decode: active_decode_blocks -> ITL
+    """
+
+    def __init__(self, window_size: int, min_observations: int = 5):
+        self.window_size = window_size
+        self.min_observations = min_observations
+        self._observations: deque = deque(maxlen=window_size)
+        self._model = LinearRegression()
+        self._is_fitted = False
+
+    def add_observation(self, x: float, y: float) -> None:
+        """Add an (X, y) observation to the sliding window."""
+        self._observations.append((x, y))
+        self._is_fitted = False
+
+    def fit(self) -> bool:
+        """Fit the linear regression model on current observations.
+
+        Returns:
+            True if fitting succeeded, False if insufficient data.
+        """
+        if len(self._observations) < self.min_observations:
+            return False
+        X = np.array([obs[0] for obs in self._observations]).reshape(-1, 1)
+        y = np.array([obs[1] for obs in self._observations])
+        self._model.fit(X, y)
+        self._is_fitted = True
+        return True
+
+    def predict_x_from_sla(self, target_y: float) -> Optional[float]:
+        """Reverse prediction: given a target latency (SLA), find the max load.
+
+        Solves: x = (y - b) / m
+
+        Safety guards:
+        - Returns None if insufficient data (cold start)
+        - Falls back to observation-based heuristic if slope <= 0
+        - Clamps result to non-negative
+
+        Args:
+            target_y: Target latency SLA value (e.g., TTFT in ms, ITL in ms)
+
+        Returns:
+            Maximum load value that satisfies the SLA, or None if insufficient data.
+        """
+        if not self._is_fitted and not self.fit():
+            return None
+
+        coef = float(self._model.coef_[0])
+        intercept = float(self._model.intercept_)
+
+        if coef <= 0:
+            logger.warning(
+                f"Regression slope is non-positive ({coef:.6f}), "
+                "falling back to observation-based heuristic"
+            )
+            return self._fallback_x_from_observations(target_y)
+
+        x_sla = (target_y - intercept) / coef
+        return max(0.0, x_sla)
+
+    def _fallback_x_from_observations(self, target_y: float) -> float:
+        """Fallback when regression slope is non-positive.
+
+        Returns the minimum x among observations where y < target_y.
+        If all observations have y >= target_y, returns the smallest x overall.
+        """
+        below = [(x, y) for x, y in self._observations if y < target_y]
+        if below:
+            result = min(x for x, _ in below)
+        else:
+            result = min(x for x, _ in self._observations)
+        logger.info(
+            f"Fallback x from observations: {result:.1f} "
+            f"(points below SLA: {len(below)}/{len(self._observations)})"
+        )
+        return max(0.0, result)
+
+    def has_sufficient_data(self) -> bool:
+        """Check if enough observations have been collected (cold start guard)."""
+        return len(self._observations) >= self.min_observations
+
+    @property
+    def num_observations(self) -> int:
+        return len(self._observations)
+
+    @property
+    def slope(self) -> Optional[float]:
+        """Return the current regression slope, or None if not fitted."""
+        if not self._is_fitted and not self.fit():
+            return None
+        return float(self._model.coef_[0])
+
+    @property
+    def intercept(self) -> Optional[float]:
+        """Return the current regression intercept, or None if not fitted."""
+        if not self._is_fitted and not self.fit():
+            return None
+        return float(self._model.intercept_)

components/src/dynamo/planner/utils/planner_argparse.py

@@ -45,8 +45,8 @@ def create_sla_planner_parser() -> argparse.ArgumentParser:
     parser.add_argument(
         "--mode",
         default=SLAPlannerDefaults.mode,
-        choices=["disagg", "prefill", "decode"],
-        help="Planner mode: disagg (prefill+decode), prefill-only, or decode-only",
+        choices=["disagg", "prefill", "decode", "agg"],
+        help="Planner mode: disagg (prefill+decode), prefill-only, decode-only, or agg (aggregated)",
     )
     parser.add_argument(
         "--no-operation",
@@ -176,4 +176,126 @@ def create_sla_planner_parser() -> argparse.ArgumentParser:
         type=str,
         help="Model name of deployment (only required for virtual environment)",
     )
+
+    # Scaling mode flags
+    parser.add_argument(
+        "--enable-throughput-scaling",
+        action="store_true",
+        default=SLAPlannerDefaults.enable_throughput_scaling,
+        help="Enable throughput-based scaling (default: True)",
+    )
+    parser.add_argument(
+        "--disable-throughput-scaling",
+        action="store_true",
+        default=False,
+        help="Disable throughput-based scaling",
+    )
+    parser.add_argument(
+        "--enable-loadbased-scaling",
+        action="store_true",
+        default=SLAPlannerDefaults.enable_loadbased_scaling,
+        help="Enable load-based scaling",
+    )
+
+    # Load-based scaling settings
+    parser.add_argument(
+        "--loadbased-router-metrics-url",
+        type=str,
+        default=SLAPlannerDefaults.loadbased_router_metrics_url,
+        help="URL to router's /metrics endpoint for direct load metric queries (default: auto-discovered from the DGD)",
+    )
+    parser.add_argument(
+        "--loadbased-adjustment-interval",
+        type=int,
+        default=SLAPlannerDefaults.loadbased_adjustment_interval,
+        help="Load-based adjustment interval in seconds (must be < --adjustment-interval)",
+    )
+    parser.add_argument(
+        "--loadbased-learning-window",
+        type=int,
+        default=SLAPlannerDefaults.loadbased_learning_window,
+        help="Sliding window size for load-based regression (number of observations)",
+    )
+    parser.add_argument(
+        "--loadbased-scaling-down-sensitivity",
+        type=int,
+        default=SLAPlannerDefaults.loadbased_scaling_down_sensitivity,
+        help="Scale-down sensitivity 0-100 (0=never scale down, 100=aggressive)",
+    )
+    parser.add_argument(
+        "--loadbased-metric-samples",
+        type=int,
+        default=SLAPlannerDefaults.loadbased_metric_samples,
+        help="Number of metric samples to average per load-based adjustment interval",
+    )
+    parser.add_argument(
+        "--loadbased-min-observations",
+        type=int,
+        default=SLAPlannerDefaults.loadbased_min_observations,
+        help="Minimum regression observations before load-based scaling starts (cold start)",
+    )
+
     return parser
+
+
+def validate_sla_planner_args(args: argparse.Namespace) -> None:
+    """Validate and normalize SLA planner arguments.
+
+    Resolves conflicting flags, checks required arguments, and enforces
+    constraints between related arguments. Should be called after parsing
+    and before constructing any planner.
+
+    Raises:
+        ValueError: If argument constraints are violated
+    """
+    # Resolve enable/disable throughput flags
+    if getattr(args, "disable_throughput_scaling", False):
+        args.enable_throughput_scaling = False
+
+    enable_throughput = getattr(args, "enable_throughput_scaling", True)
+    enable_loadbased = getattr(args, "enable_loadbased_scaling", False)
+
+    # At least one scaling mode must be enabled
+    if not enable_throughput and not enable_loadbased:
+        raise ValueError(
+            "At least one scaling mode must be enabled "
+            "(--enable-throughput-scaling or --enable-loadbased-scaling)"
+        )
+
+    if enable_loadbased:
+        # Router metrics URL is required for load-based scaling unless in
+        # kubernetes mode where it can be auto-discovered from the DGD.
+        environment = getattr(args, "environment", "kubernetes")
+        if (
+            not getattr(args, "loadbased_router_metrics_url", None)
+            and environment != "kubernetes"
+        ):
+            raise ValueError(
+                "--loadbased-router-metrics-url is required when "
+                "load-based scaling is enabled outside kubernetes mode"
+            )
+
+        # Load-based interval must be shorter than throughput interval
+        if enable_throughput:
+            if args.loadbased_adjustment_interval >= args.adjustment_interval:
+                raise ValueError(
+                    f"--loadbased-adjustment-interval ({args.loadbased_adjustment_interval}s) "
+                    f"must be shorter than --adjustment-interval ({args.adjustment_interval}s). "
+                    "Load-based scaling is the fast reactive loop; throughput-based is the "
+                    "slow predictive loop."
+                )
+
+        # Auto-disable correction factor: load-based regression already
+        # accounts for actual latency conditions.
+        if not getattr(args, "no_correction", False):
+            import logging
+
+            logger = logging.getLogger(__name__)
+
+            # TODO: enable correction after we can gather engine forward pass metrics
+            logger.warning(
+                "Correction factor is automatically disabled when load-based "
+                "scaling is enabled. Load-based scaling already accounts for "
+                "actual latency conditions."
+            )
+            args.no_correction = True

components/src/dynamo/planner/utils/planner_core.py

@@ -25,7 +25,12 @@ from dynamo.planner.utils.perf_interpolation import (
     PrefillInterpolator,
 )
 from dynamo.planner.utils.pre_swept_results_utils import PreSweptResultsHelper
-from dynamo.planner.utils.prometheus import PrometheusAPIClient
+from dynamo.planner.utils.prometheus import (
+    CachedLoadMetrics,
+    DirectRouterMetricsClient,
+    Metrics,
+    PrometheusAPIClient,
+)
 from dynamo.planner.utils.trace_data_extractor import extract_metrics_from_mooncake
 from dynamo.runtime import DistributedRuntime
 from dynamo.runtime.logging import configure_dynamo_logging
@@ -34,31 +39,6 @@ configure_dynamo_logging()
 logger = logging.getLogger(__name__)
 
 
-@dataclass
-class Metrics:
-    ttft: Optional[float] = None
-    itl: Optional[float] = None
-    num_req: Optional[float] = None
-    isl: Optional[float] = None
-    osl: Optional[float] = None
-    request_duration: Optional[float] = None
-    p_load: Optional[float] = None
-    d_load: Optional[float] = None
-
-    def is_valid(self) -> bool:
-        """Check if all metrics are valid (not None and not NaN)."""
-        return (
-            self.ttft is not None
-            and self.itl is not None
-            and self.isl is not None
-            and self.osl is not None
-            and not math.isnan(self.ttft)
-            and not math.isnan(self.itl)
-            and not math.isnan(self.isl)
-            and not math.isnan(self.osl)
-        )
-
-
 class PlannerPrometheusMetrics:
     """Container for all Planner Prometheus metrics."""
 
@@ -127,6 +107,11 @@ class PlannerSharedState:
     num_d_workers: int = 0
     cumulative_gpu_hours: float = 0.0
     last_adjustment_time: float = 0.0
+    # Lower bounds from throughput-based scaling (used when both modes enabled)
+    throughput_lower_bound_p: int = 1
+    throughput_lower_bound_d: int = 1
+    # Separate timestamp for load-based adjustment loop
+    last_loadbased_adjustment_time: float = 0.0
 
 
 def _apply_global_gpu_budget(
@@ -265,7 +250,8 @@ class BasePlanner:
         dryrun: bool = False,
         shared_state: Optional[PlannerSharedState] = None,
         prometheus_metrics: Optional[PlannerPrometheusMetrics] = None,
-        prometheus_api_client: Optional[PrometheusAPIClient] = None,
+        prometheus_traffic_client: Optional[PrometheusAPIClient] = None,
+        prometheus_engine_client: Optional[DirectRouterMetricsClient] = None,
         connector=None,
         start_prometheus_server: bool = True,
     ):
@@ -296,10 +282,13 @@ class BasePlanner:
                 else:
                     raise ValueError(f"Invalid environment: {args.environment}")
 
-            self.prometheus_api_client = prometheus_api_client or PrometheusAPIClient(
+            self.prometheus_traffic_client = (
+                prometheus_traffic_client
+                or PrometheusAPIClient(
                     args.metric_pulling_prometheus_endpoint,
                     args.namespace,
                 )
+            )
 
         predictor_cls = LOAD_PREDICTORS[args.load_predictor]
         # Predictors read configuration from `args` directly.
@@ -337,6 +326,15 @@ class BasePlanner:
                     if hasattr(p, "reset_idle_skip"):
                         p.reset_idle_skip()
 
+        # Load-based scaling flags.
+        # Argument validation (flag resolution, constraint checks, correction factor
+        # auto-disable) is handled by validate_sla_planner_args() in planner_argparse.
+        self.enable_loadbased = getattr(args, "enable_loadbased_scaling", False)
+        self.enable_throughput = getattr(args, "enable_throughput_scaling", True)
+
+        # Only create interpolators when throughput-based scaling is enabled
+        # (they require profiling data that isn't needed for load-based-only mode)
+        if self.enable_throughput:
             if "use-pre-swept-results" in args.profile_results_dir:
                 config_list = args.profile_results_dir.split(":")
                 configs = {
@@ -364,7 +362,9 @@ class BasePlanner:
                         "Cannot set profile_results_dir to 'use-pre-swept-results' in non-dryrun mode"
                     )
             else:
-            self.prefill_interpolator = PrefillInterpolator(args.profile_results_dir)
+                self.prefill_interpolator = PrefillInterpolator(
+                    args.profile_results_dir
+                )
                 self.decode_interpolator = DecodeInterpolator(args.profile_results_dir)
 
         self.prefill_component_name = WORKER_COMPONENT_NAMES[
@@ -405,6 +405,48 @@ class BasePlanner:
         else:
             self.no_correction = args.no_correction
 
+        if self.enable_loadbased:
+            if prometheus_engine_client is not None:
+                self.prometheus_engine_client = prometheus_engine_client
+            else:
+                # Auto-discover frontend metrics URL in Kubernetes mode
+                if not args.loadbased_router_metrics_url and isinstance(
+                    getattr(self, "connector", None), KubernetesConnector
+                ):
+                    args.loadbased_router_metrics_url = (
+                        self.connector.get_frontend_metrics_url()
+                    )
+                    if not args.loadbased_router_metrics_url:
+                        raise ValueError(
+                            "Could not auto-discover frontend metrics URL from DGD. "
+                            "No service with componentType 'frontend' found. "
+                            "Please provide --loadbased-router-metrics-url explicitly."
+                        )
+                    else:
+                        logger.info(
+                            f"Auto-discovered frontend metrics URL: {args.loadbased_router_metrics_url}"
+                        )
+
+                self.prometheus_engine_client = DirectRouterMetricsClient(
+                    args.loadbased_router_metrics_url, args.namespace
+                )
+            self.cached_load_metrics = CachedLoadMetrics()
+
+            from dynamo.planner.utils.load_based_regression import (
+                LoadBasedRegressionModel,
+            )
+
+            if self.component_type == SubComponentType.PREFILL:
+                self.ttft_regression = LoadBasedRegressionModel(
+                    window_size=self.args.loadbased_learning_window,
+                    min_observations=self.args.loadbased_min_observations,
+                )
+            elif self.component_type == SubComponentType.DECODE:
+                self.itl_regression = LoadBasedRegressionModel(
+                    window_size=self.args.loadbased_learning_window,
+                    min_observations=self.args.loadbased_min_observations,
+                )
+
     @property
     def last_metrics(self) -> Metrics:
         return self.shared_state.last_metrics
@@ -508,7 +550,7 @@ class BasePlanner:
 
         return num_p_workers, num_d_workers, True  # Always stable for non-K8s
 
-    async def observe_metrics(
+    async def observe_traffic_stats(
         self, require_prefill: bool = True, require_decode: bool = True
     ) -> None:
         """
@@ -546,37 +588,39 @@ class BasePlanner:
 
         # Prometheus returns seconds, convert to milliseconds
         self.last_metrics.ttft = (
-            self.prometheus_api_client.get_avg_time_to_first_token(
+            self.prometheus_traffic_client.get_avg_time_to_first_token(
                 f"{self.args.adjustment_interval}s",
                 self.model_name,
             )
             * 1000
         )
         self.last_metrics.itl = (
-            self.prometheus_api_client.get_avg_inter_token_latency(
+            self.prometheus_traffic_client.get_avg_inter_token_latency(
                 f"{self.args.adjustment_interval}s",
                 self.model_name,
             )
             * 1000
         )
-        self.last_metrics.num_req = self.prometheus_api_client.get_avg_request_count(
+        self.last_metrics.num_req = (
+            self.prometheus_traffic_client.get_avg_request_count(
                 f"{self.args.adjustment_interval}s",
                 self.model_name,
             )
+        )
         self.last_metrics.request_duration = (
-            self.prometheus_api_client.get_avg_request_duration(
+            self.prometheus_traffic_client.get_avg_request_duration(
                 f"{self.args.adjustment_interval}s",
                 self.model_name,
             )
         )
         self.last_metrics.isl = (
-            self.prometheus_api_client.get_avg_input_sequence_tokens(
+            self.prometheus_traffic_client.get_avg_input_sequence_tokens(
                 f"{self.args.adjustment_interval}s",
                 self.model_name,
             )
         )
         self.last_metrics.osl = (
-            self.prometheus_api_client.get_avg_output_sequence_tokens(
+            self.prometheus_traffic_client.get_avg_output_sequence_tokens(
                 f"{self.args.adjustment_interval}s",
                 self.model_name,
             )
@@ -623,7 +667,9 @@ class BasePlanner:
             logger.error(f"Failed to predict load: {e}")
             return None, None, None
 
-    def dryrun_observe_metrics(self, num_req: int, isl_avg: float, osl_avg: float):
+    def dryrun_observe_traffic_stats(
+        self, num_req: int, isl_avg: float, osl_avg: float
+    ):
         self.num_req_predictor.add_data_point(num_req)
         self.isl_predictor.add_data_point(isl_avg)
         self.osl_predictor.add_data_point(osl_avg)
@@ -700,44 +746,73 @@ class BasePlanner:
         ]
         await self.connector.set_component_replicas(target_replicas, blocking=False)
 
-    async def run(self):
-        """Main loop for the planner"""
-        if not self.args.no_operation:
-            logger.info("Validating deployment...")
-            require_prefill = self.component_type == SubComponentType.PREFILL
-            require_decode = self.component_type == SubComponentType.DECODE
-            await self.connector.validate_deployment(
-                prefill_component_name=(
-                    self.prefill_component_name if require_prefill else None
-                ),
-                decode_component_name=(
-                    self.decode_component_name if require_decode else None
-                ),
-                require_prefill=require_prefill,
-                require_decode=require_decode,
+    async def _apply_scaling_blocking(self, desired_replicas: int) -> None:
+        """Apply scaling with blocking=True (wait for deployment ready)."""
+        if self.args.no_operation:
+            return
+        target_replicas = [
+            TargetReplica(
+                sub_component_type=self.component_type,
+                component_name=self._component_name(),
+                desired_replicas=desired_replicas,
             )
-            logger.info("Successfully validated the deployment")
+        ]
+        await self.connector.set_component_replicas(target_replicas, blocking=True)
 
-            # Initialize GPU counts
-            _initialize_gpu_counts(
-                self.args,
-                self.connector,
-                require_prefill=require_prefill,
-                require_decode=require_decode,
+    async def observe_engine_load_stats(self) -> None:
+        """Query DirectRouterMetricsClient for per-worker metrics, update regression."""
+        worker_type = self.component_type.value  # "prefill" or "decode"
+        result = self.prometheus_engine_client.get_recent_and_averaged_metrics(
+            worker_type
+        )
+        if result is None:
+            logger.warning(
+                f"No per-worker metrics available yet for {worker_type} (buffer empty)"
             )
+            return
 
-            await self.connector.wait_for_deployment_ready()
+        recent, per_worker_averaged, cluster_averaged = result
+        self.cached_load_metrics = CachedLoadMetrics(
+            recent=recent,
+            per_worker_averaged=per_worker_averaged,
+            cluster_averaged=cluster_averaged,
+        )
 
-            model_name = await self._get_model_name(
-                require_prefill=require_prefill, require_decode=require_decode
+        if self.component_type == SubComponentType.PREFILL:
+            for wid, m in recent.items():
+                active_prefill = m.get("active_prefill_tokens", 0.0)
+                last_isl = m.get("last_isl", 0.0)
+                last_ttft = m.get("last_ttft", 0.0)
+                if last_ttft > 0 and last_isl > 0:
+                    x = active_prefill + last_isl
+                    # last_ttft is in seconds from Prometheus, convert to ms
+                    y = last_ttft * 1000
+                    logger.info(
+                        f"{SubComponentType.PREFILL.value} Worker {wid} observed status: TTFT {y:.2f}ms @ prefill tokens {x:.2f}"
+                    )
+                    self.ttft_regression.add_observation(x, y)
+
+        elif self.component_type == SubComponentType.DECODE:
+            for wid, m in recent.items():
+                active_decode = m.get("active_decode_blocks", 0.0)
+                last_itl = m.get("last_itl", 0.0)
+                if last_itl > 0 and active_decode > 0:
+                    x = active_decode
+                    # last_itl is in seconds from Prometheus, convert to ms
+                    y = last_itl * 1000
+                    logger.info(
+                        f"{SubComponentType.DECODE.value} Worker {wid} observed status: ITL {y:.2f}ms @ decode blocks {x:.2f}"
                     )
-            logger.info(f"Detected model name from deployment: {model_name}")
-            self.model_name = (
-                model_name.lower()
-            )  # normalize model name to lowercase (MDC)
+                    self.itl_regression.add_observation(x, y)
 
-        self.shared_state.last_adjustment_time = time.time()
+    def loadbased_plan_adjustment(self) -> Optional[int]:
+        """Load-based scaling decision. Override in subclasses."""
+        raise NotImplementedError
 
+    async def _throughput_loop(
+        self, require_prefill: bool, require_decode: bool
+    ) -> None:
+        """Throughput-based scaling loop (existing behavior, extracted from run())."""
         while True:
             current_time = time.time()
 
@@ -746,235 +821,141 @@ class BasePlanner:
                 >= self.args.adjustment_interval
             ):
                 self.shared_state.last_adjustment_time = time.time()
-                logger.info("New adjustment interval started!")
+                logger.info("New throughput adjustment interval started!")
 
-                await self.observe_metrics(
+                await self.observe_traffic_stats(
                     require_prefill=require_prefill, require_decode=require_decode
                 )
                 desired_replicas = self.plan_adjustment()
                 if desired_replicas is not None:
+                    if self.enable_loadbased:
+                        # When load-based is also enabled: just set lower bound
+                        if self.component_type == SubComponentType.PREFILL:
+                            self.shared_state.throughput_lower_bound_p = (
+                                desired_replicas
+                            )
+                        else:
+                            self.shared_state.throughput_lower_bound_d = (
+                                desired_replicas
+                            )
+                        logger.info(
+                            f"Throughput lower bound set to {desired_replicas} for {self.component_type.value}"
+                        )
+                    else:
+                        # Throughput-only: apply scaling directly
                         desired_replicas = self.apply_component_budget(desired_replicas)
                         self.update_predicted_replicas_metric(desired_replicas)
+                        # Throughput planner does not needs blocking scaling because it monitors
+                        # and predicts the load, not relying on the current status of the engine.
                         await self._apply_scaling(desired_replicas)
 
-            # sleep for a while to avoid busy-waiting but not too long to miss the next adjustment
             await asyncio.sleep(self.args.adjustment_interval / 10)
 
+    async def _load_loop(self, require_prefill: bool, require_decode: bool) -> None:
+        """Load-based scaling loop at shorter interval."""
+        while True:
+            await asyncio.sleep(self.args.loadbased_adjustment_interval)
+            logger.info("New load-based adjustment interval started!")
 
-class PrefillPlanner(BasePlanner):
-    component_type = SubComponentType.PREFILL
-
-    def _update_correction_factor(self) -> bool:
-        expect_ttft = self.prefill_interpolator.interpolate_ttft(self.last_metrics.isl)
-        self.p_correction_factor = self.last_metrics.ttft / expect_ttft
-        logger.info(f"Correction factor (prefill TTFT): {self.p_correction_factor:.3f}")
-        if self.prometheus_port != 0 and self.prometheus_metrics is not None:
-            self.prometheus_metrics.p_correction_factor.set(self.p_correction_factor)
-        return True
-
-    def _compute_replica_requirements(
-        self, next_num_req: float, next_isl: float, next_osl: float
-    ) -> int:
-        pred_prefill_throughput = (
-            next_num_req
-            * next_isl
-            / self.args.adjustment_interval
-            * min(1, self.p_correction_factor)
-        )
-        p_thpt_per_gpu = self.prefill_interpolator.interpolate_thpt_per_gpu(next_isl)
-        next_num_p = math.ceil(
-            pred_prefill_throughput / p_thpt_per_gpu / self.args.prefill_engine_num_gpu
-        )
-        next_num_p = max(next_num_p, self.args.min_endpoint)
-        logger.info(
-            f"Prefill calculation: {pred_prefill_throughput:.2f}(p_thpt) / "
-            f"{p_thpt_per_gpu * self.args.prefill_engine_num_gpu:.2f}(p_engine_cap) = "
-            f"{next_num_p}(num_p)"
+            # Query DGD for fresh worker counts
+            num_p, num_d, _ = await self.get_workers_info(
+                require_prefill=require_prefill, require_decode=require_decode
             )
-        return next_num_p
-
-    def update_predicted_replicas_metric(self, desired_replicas: int) -> None:
-        if self.prometheus_port != 0 and self.prometheus_metrics is not None:
-            self.prometheus_metrics.predicted_num_p.set(desired_replicas)
+            self.shared_state.num_p_workers = num_p
+            self.shared_state.num_d_workers = num_d
 
+            # Observe per-worker metrics from router
+            await self.observe_engine_load_stats()
 
-class DecodePlanner(BasePlanner):
-    component_type = SubComponentType.DECODE
-
-    def _update_correction_factor(self) -> bool:
-        if self.shared_state.num_d_workers == 0:
-            logger.warning(
-                "No decode workers found for correction factor, skipping correction update"
-            )
-            return True
-        expect_itl = self.decode_interpolator.interpolate_itl(
-            concurrency=self.last_metrics.num_req  # type: ignore
-            / self.shared_state.num_d_workers
-            * self.last_metrics.request_duration  # type: ignore
-            / self.args.adjustment_interval,
-            context_length=self.last_metrics.isl + self.last_metrics.osl / 2,  # type: ignore
-        )
-        self.d_correction_factor = self.last_metrics.itl / expect_itl
-        logger.info(f"Correction factor (decode ITL): {self.d_correction_factor:.3f}")
-        if self.prometheus_port != 0 and self.prometheus_metrics is not None:
-            self.prometheus_metrics.d_correction_factor.set(self.d_correction_factor)
-        return True
-
-    def _compute_replica_requirements(
-        self, next_num_req: float, next_isl: float, next_osl: float
-    ) -> int:
-        if self.d_correction_factor <= 0:
-            logger.warning(
-                f"d_correction_factor is {self.d_correction_factor}, using default value of 1.0"
+            # Reconcile DGD worker count with router Prometheus count
+            prom_count = len(self.cached_load_metrics.recent)
+            dgd_count = (
+                num_p if self.component_type == SubComponentType.PREFILL else num_d
             )
-            corrected_itl = self.args.itl
-        else:
-            corrected_itl = self.args.itl / self.d_correction_factor
-        (
-            pred_decode_thpt_per_gpu,
-            _,
-            _,
-        ) = self.decode_interpolator.find_best_throughput_per_gpu(
-            itl=corrected_itl, context_length=next_isl + next_osl / 2
-        )
-        pred_decode_throughput = next_num_req * next_osl / self.args.adjustment_interval
-        next_num_d = math.ceil(
-            pred_decode_throughput
-            / pred_decode_thpt_per_gpu
-            / self.args.decode_engine_num_gpu
-        )
-        next_num_d = max(next_num_d, self.args.min_endpoint)
-        logger.info(
-            f"Decode calculation: {pred_decode_throughput:.2f}(d_thpt) / "
-            f"{pred_decode_thpt_per_gpu * self.args.decode_engine_num_gpu:.2f}(d_engine_cap) = "
-            f"{next_num_d}(num_d)"
+            if prom_count != dgd_count:
+                logger.warning(
+                    f"Worker count mismatch: DGD reports {dgd_count} workers, "
+                    f"router metrics reports {prom_count} workers. "
+                    "Skipping load-based scaling adjustment."
                 )
-        return next_num_d
-
-    def update_predicted_replicas_metric(self, desired_replicas: int) -> None:
-        if self.prometheus_port != 0 and self.prometheus_metrics is not None:
-            self.prometheus_metrics.predicted_num_d.set(desired_replicas)
-
-
-class DisaggPlanner:
-    def __init__(
-        self, runtime: Optional[DistributedRuntime], args: argparse.Namespace
-    ) -> None:
-        self.args = args
-        self.shared_state = PlannerSharedState()
-        prometheus_metrics = PlannerPrometheusMetrics()
+                continue
 
-        self.prefill_planner = PrefillPlanner(
-            runtime,
-            args,
-            shared_state=self.shared_state,
-            prometheus_metrics=prometheus_metrics,
-            start_prometheus_server=True,
-        )
-        self.decode_planner = DecodePlanner(
-            runtime,
-            args,
-            shared_state=self.shared_state,
-            prometheus_metrics=prometheus_metrics,
-            prometheus_api_client=getattr(
-                self.prefill_planner, "prometheus_api_client", None
-            ),
-            connector=getattr(self.prefill_planner, "connector", None),
-            start_prometheus_server=False,
-        )
+            desired_replicas = self.loadbased_plan_adjustment()
 
-    async def _async_init(self):
-        # Prefill/Decode share the same connector instance in disagg mode.
-        await self.prefill_planner._async_init()
+            if desired_replicas is not None:
+                # Enforce lower bound from throughput-based
+                if self.enable_throughput:
+                    if self.component_type == SubComponentType.PREFILL:
+                        lower_bound = self.shared_state.throughput_lower_bound_p
+                    else:
+                        lower_bound = self.shared_state.throughput_lower_bound_d
+                    desired_replicas = max(desired_replicas, lower_bound)
+                desired_replicas = self.apply_component_budget(desired_replicas)
+                self.update_predicted_replicas_metric(desired_replicas)
+                # Load-based planner needs blocking scaling because it only checks
+                # the current status of the engine, not the predicted load.
+                # We need to wait for the deployment to be steady before making another one.
+                await self._apply_scaling_blocking(desired_replicas)
 
     async def run(self):
+        """Main loop for the planner"""
+        require_prefill = self.component_type == SubComponentType.PREFILL
+        require_decode = self.component_type == SubComponentType.DECODE
+
         if not self.args.no_operation:
             logger.info("Validating deployment...")
-            await self.prefill_planner.connector.validate_deployment(
-                prefill_component_name=self.prefill_planner.prefill_component_name,
-                decode_component_name=self.prefill_planner.decode_component_name,
-                require_prefill=True,
-                require_decode=True,
+            await self.connector.validate_deployment(
+                prefill_component_name=(
+                    self.prefill_component_name if require_prefill else None
+                ),
+                decode_component_name=(
+                    self.decode_component_name if require_decode else None
+                ),
+                require_prefill=require_prefill,
+                require_decode=require_decode,
             )
             logger.info("Successfully validated the deployment")
 
             # Initialize GPU counts
             _initialize_gpu_counts(
                 self.args,
-                self.prefill_planner.connector,
-                require_prefill=True,
-                require_decode=True,
+                self.connector,
+                require_prefill=require_prefill,
+                require_decode=require_decode,
             )
 
-            await self.prefill_planner.connector.wait_for_deployment_ready()
+            await self.connector.wait_for_deployment_ready()
 
-            model_name = await self.prefill_planner._get_model_name(
-                require_prefill=True, require_decode=True
+        # Model name discovery runs in all modes (needed for metrics collection)
+        if not self.args.no_operation:
+            model_name = await self._get_model_name(
+                require_prefill=require_prefill, require_decode=require_decode
             )
             logger.info(f"Detected model name from deployment: {model_name}")
-            model_name = model_name.lower()
-            self.prefill_planner.model_name = model_name
-            self.decode_planner.model_name = model_name
-
-        self.shared_state.last_adjustment_time = time.time()
-
-        while True:
-            current_time = time.time()
+            self.model_name = model_name.lower()
+        else:
+            model_name = getattr(self.args, "model_name", None)
+            if not model_name:
+                raise ValueError(
+                    "Model name is required in no-operation mode. "
+                    "Please provide --model-name."
+                )
+            self.model_name = model_name.lower()
 
-            if (
-                current_time - self.shared_state.last_adjustment_time
-                >= self.args.adjustment_interval
-            ):
         self.shared_state.last_adjustment_time = time.time()
-                logger.info("New adjustment interval started!")
+        self.shared_state.last_loadbased_adjustment_time = time.time()
 
-                await self.prefill_planner.observe_metrics(
-                    require_prefill=True, require_decode=True
+        # Build list of concurrent loops based on enabled scaling modes
+        loops = []
+        if self.enable_throughput:
+            loops.append(self._throughput_loop(require_prefill, require_decode))
+        if self.enable_loadbased:
+            loops.append(self._load_loop(require_prefill, require_decode))
+            loops.append(
+                self.prometheus_engine_client.run_sampling_loop(
+                    self.args.loadbased_metric_samples,
+                    self.args.loadbased_adjustment_interval,
                 )
-                self.decode_planner.update_predictors_from_metrics(
-                    self.shared_state.last_metrics
             )
-                next_num_p = self.prefill_planner.plan_adjustment()
-                next_num_d = self.decode_planner.plan_adjustment()
-                if next_num_p is None or next_num_d is None:
-                    continue
 
-                next_num_p, next_num_d = _apply_global_gpu_budget(
-                    next_num_p, next_num_d, self.args
-                )
-                self.prefill_planner.update_predicted_replicas_metric(next_num_p)
-                self.decode_planner.update_predicted_replicas_metric(next_num_d)
-
-                if not self.args.no_operation:
-                    target_replicas = [
-                        TargetReplica(
-                            sub_component_type=SubComponentType.PREFILL,
-                            component_name=self.prefill_planner.prefill_component_name,
-                            desired_replicas=next_num_p,
-                        ),
-                        TargetReplica(
-                            sub_component_type=SubComponentType.DECODE,
-                            component_name=self.prefill_planner.decode_component_name,
-                            desired_replicas=next_num_d,
-                        ),
-                    ]
-                    await self.prefill_planner.connector.set_component_replicas(
-                        target_replicas, blocking=False
-                    )
-
-            # sleep for a while to avoid busy-waiting but not too long to miss the next adjustment
-            await asyncio.sleep(self.args.adjustment_interval / 10)
-
-
-async def start_sla_planner(runtime: DistributedRuntime, args: argparse.Namespace):
-    mode = getattr(args, "mode", "disagg")
-    if mode == "disagg":
-        planner = DisaggPlanner(runtime, args)
-    elif mode == "prefill":
-        planner = PrefillPlanner(runtime, args)
-    elif mode == "decode":
-        planner = DecodePlanner(runtime, args)
-    else:
-        raise ValueError(f"Invalid planner mode: {mode}")
-    await planner._async_init()
-    await planner.run()
+        await asyncio.gather(*loops)

components/src/dynamo/planner/utils/prefill_planner.py

+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+import logging
+import math
+from typing import Optional
+
+from dynamo.planner import SubComponentType
+from dynamo.planner.utils.planner_core import BasePlanner
+from dynamo.runtime.logging import configure_dynamo_logging
+
+configure_dynamo_logging()
+logger = logging.getLogger(__name__)
+
+
+class PrefillPlanner(BasePlanner):
+    component_type = SubComponentType.PREFILL
+
+    def loadbased_plan_adjustment(self) -> Optional[int]:
+        """Load-based scaling decision for prefill. Returns desired_replicas or None."""
+        if not self.ttft_regression.has_sufficient_data():
+            logger.info(
+                f"TTFT regression: insufficient data ({self.ttft_regression.num_observations}"
+                f"/{self.ttft_regression.min_observations}), skipping load-based scaling"
+            )
+            return None
+
+        x_sla = self.ttft_regression.predict_x_from_sla(self.args.ttft)
+        if x_sla is None:
+            return None
+
+        if not self.cached_load_metrics.recent:
+            return None
+
+        recent = self.cached_load_metrics.recent
+        cluster_averaged = self.cached_load_metrics.cluster_averaged
+
+        # Averaged ISL across all workers in the past adjustment interval
+        avg_isl = cluster_averaged.get("last_isl", 0.0)
+        target_active_tokens = x_sla - avg_isl
+
+        if target_active_tokens <= 0:
+            logger.warning(
+                f"TTFT SLA unachievable at current ISL: x_sla={x_sla:.1f}, "
+                f"avg_isl={avg_isl:.1f}, skipping load-based prefill scaling"
+            )
+            return None
+
+        num_workers = self.shared_state.num_p_workers
+        if num_workers == 0:
+            return None
+
+        logger.info(
+            f"Load-based prefill: x_sla={x_sla:.1f}, avg_isl={avg_isl:.1f}, "
+            f"target_active_tokens={target_active_tokens:.1f}, workers={num_workers}, "
+            f"slope={self.ttft_regression.slope:.6f}, intercept={self.ttft_regression.intercept:.3f}"
+        )
+
+        # Scale up: ALL workers above target (use recent metrics)
+        all_above = all(
+            m.get("active_prefill_tokens", 0.0) > target_active_tokens
+            for m in recent.values()
+        )
+        if all_above:
+            logger.info(
+                f"Load-based prefill: ALL workers above target ({target_active_tokens:.1f}), "
+                f"scaling up to {num_workers + 1}"
+            )
+            return num_workers + 1
+
+        # Scale down: ALL workers below boundary (use recent metrics)
+        if num_workers > 1:
+            sensitivity = self.args.loadbased_scaling_down_sensitivity / 100.0
+            boundary = (
+                target_active_tokens * (num_workers - 1) / num_workers * sensitivity
+            )
+            all_below = all(
+                m.get("active_prefill_tokens", 0.0) < boundary for m in recent.values()
+            )
+            if all_below:
+                logger.info(
+                    f"Load-based prefill: ALL workers below boundary ({boundary:.1f}), "
+                    f"scaling down to {num_workers - 1}"
+                )
+                return num_workers - 1
+
+        return None
+
+    def _update_correction_factor(self) -> bool:
+        expect_ttft = self.prefill_interpolator.interpolate_ttft(self.last_metrics.isl)
+        self.p_correction_factor = self.last_metrics.ttft / expect_ttft
+        logger.info(f"Correction factor (prefill TTFT): {self.p_correction_factor:.3f}")
+        if self.prometheus_port != 0 and self.prometheus_metrics is not None:
+            self.prometheus_metrics.p_correction_factor.set(self.p_correction_factor)
+        return True
+
+    def _compute_replica_requirements(
+        self, next_num_req: float, next_isl: float, next_osl: float
+    ) -> int:
+        pred_prefill_throughput = (
+            next_num_req
+            * next_isl
+            / self.args.adjustment_interval
+            * min(1, self.p_correction_factor)
+        )
+        p_thpt_per_gpu = self.prefill_interpolator.interpolate_thpt_per_gpu(next_isl)
+        if p_thpt_per_gpu <= 0:
+            logger.warning(
+                f"p_thpt_per_gpu is {p_thpt_per_gpu} "
+                "(no throughput satisfies TTFT target), falling back to min_endpoint"
+            )
+            return self.args.min_endpoint
+        next_num_p = math.ceil(
+            pred_prefill_throughput / p_thpt_per_gpu / self.args.prefill_engine_num_gpu
+        )
+        next_num_p = max(next_num_p, self.args.min_endpoint)
+        logger.info(
+            f"Prefill calculation: {pred_prefill_throughput:.2f}(p_thpt) / "
+            f"{p_thpt_per_gpu * self.args.prefill_engine_num_gpu:.2f}(p_engine_cap) = "
+            f"{next_num_p}(num_p)"
+        )
+        return next_num_p
+
+    def update_predicted_replicas_metric(self, desired_replicas: int) -> None:
+        if self.prometheus_port != 0 and self.prometheus_metrics is not None:
+            self.prometheus_metrics.predicted_num_p.set(desired_replicas)

components/src/dynamo/planner/utils/prometheus.py

@@ -13,10 +13,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import asyncio
 import logging
+import math
 import typing
+from dataclasses import dataclass, field
+from typing import Optional
 
+import aiohttp
 from prometheus_api_client import PrometheusConnect
+from prometheus_client.parser import text_string_to_metric_families
 from pydantic import BaseModel, ValidationError
 
 from dynamo import prometheus_names
@@ -26,6 +32,48 @@ configure_dynamo_logging()
 logger = logging.getLogger(__name__)
 
 
+@dataclass
+class Metrics:
+    ttft: Optional[float] = None
+    itl: Optional[float] = None
+    num_req: Optional[float] = None
+    isl: Optional[float] = None
+    osl: Optional[float] = None
+    request_duration: Optional[float] = None
+    p_load: Optional[float] = None
+    d_load: Optional[float] = None
+
+    def is_valid(self) -> bool:
+        """Check if all required metrics are valid (not None and not NaN)."""
+        required = [
+            self.ttft,
+            self.itl,
+            self.isl,
+            self.osl,
+            self.num_req,
+            self.request_duration,
+        ]
+        return all(v is not None and not math.isnan(v) for v in required)
+
+
+@dataclass
+class CachedLoadMetrics:
+    """Container for load metrics used by load-based scaling.
+
+    Attributes:
+        recent:              Most recent per-worker metrics (from the latest sample).
+                             Keyed by worker_id -> {metric_name: value}.
+        per_worker_averaged: Per-worker metrics averaged over time (not across workers).
+                             Keyed by worker_id -> {metric_name: value}.
+        cluster_averaged:    Metrics averaged over time and all workers.
+                             Flat dict {metric_name: value}.
+    """
+
+    recent: dict[str, dict[str, float]] = field(default_factory=dict)
+    per_worker_averaged: dict[str, dict[str, float]] = field(default_factory=dict)
+    cluster_averaged: dict[str, float] = field(default_factory=dict)
+
+
 class FrontendMetric(BaseModel):
     container: typing.Optional[str] = None
     dynamo_namespace: typing.Optional[str] = None
@@ -180,3 +228,181 @@ def parse_frontend_metric_containers(
             logger.error(f"Error parsing frontend metric container: {e}")
             continue
     return metrics_containers
+
+
+# Metric names for per-worker load metrics (gauge-type, queried directly from router)
+_WORKER_METRIC_NAMES = {
+    "active_prefill_tokens": f"{prometheus_names.name_prefix.FRONTEND}_{prometheus_names.frontend_service.WORKER_ACTIVE_PREFILL_TOKENS}",
+    "active_decode_blocks": f"{prometheus_names.name_prefix.FRONTEND}_{prometheus_names.frontend_service.WORKER_ACTIVE_DECODE_BLOCKS}",
+    "last_ttft": f"{prometheus_names.name_prefix.FRONTEND}_{prometheus_names.frontend_service.WORKER_LAST_TIME_TO_FIRST_TOKEN_SECONDS}",
+    "last_isl": f"{prometheus_names.name_prefix.FRONTEND}_{prometheus_names.frontend_service.WORKER_LAST_INPUT_SEQUENCE_TOKENS}",
+    "last_itl": f"{prometheus_names.name_prefix.FRONTEND}_{prometheus_names.frontend_service.WORKER_LAST_INTER_TOKEN_LATENCY_SECONDS}",
+}
+
+
+class DirectRouterMetricsClient:
+    """Query router's /metrics endpoint directly for real-time per-worker metrics.
+
+    Runs a continuous background sampling loop that collects metrics at
+    evenly-spaced intervals (interval / num_samples). At decision time,
+    the load-based loop reads the buffer via get_recent_and_averaged_metrics().
+    """
+
+    def __init__(self, router_metrics_url: str, dynamo_namespace: str):
+        self.router_metrics_url = router_metrics_url
+        self.dynamo_namespace = dynamo_namespace
+        self._sample_buffer: list[dict[str, dict[str, dict[str, float]]]] = []
+        self._num_samples: int = 10
+
+    def _parse_prometheus_text(
+        self, text: str
+    ) -> dict[str, dict[str, dict[str, float]]]:
+        """Parse Prometheus text exposition format and extract per-worker metrics.
+
+        Uses prometheus_client.parser to parse the text exposition format.
+        Groups results by worker_type label (prefill/decode) so callers
+        can access only the workers they care about.
+
+        Args:
+            text: Raw Prometheus text from /metrics endpoint
+
+        Returns:
+            {"prefill": {worker_id: {metric: float, ...}},
+             "decode":  {worker_id: {metric: float, ...}}}
+        """
+        target_metrics = set(_WORKER_METRIC_NAMES.values())
+        reverse_map = {v: k for k, v in _WORKER_METRIC_NAMES.items()}
+        result: dict[str, dict[str, dict[str, float]]] = {}
+
+        for family in text_string_to_metric_families(text):
+            if family.name not in target_metrics:
+                continue
+
+            field_name = reverse_map[family.name]
+
+            for sample in family.samples:
+                labels = sample.labels
+                worker_type = labels.get("worker_type", "unknown")
+                worker_id = labels.get("worker_id", "unknown")
+                value = sample.value
+
+                if worker_type not in result:
+                    result[worker_type] = {}
+                if worker_id not in result[worker_type]:
+                    result[worker_type][worker_id] = {}
+                result[worker_type][worker_id][field_name] = value
+
+        return result
+
+    async def _fetch_and_parse(self) -> dict[str, dict[str, dict[str, float]]]:
+        """Fetch /metrics from router and parse into per-worker metrics."""
+        try:
+            async with aiohttp.ClientSession() as session:
+                async with session.get(
+                    self.router_metrics_url, timeout=aiohttp.ClientTimeout(total=2)
+                ) as response:
+                    text = await response.text()
+            return self._parse_prometheus_text(text)
+        except Exception as e:
+            logger.warning(f"Failed to fetch router metrics: {e}")
+            return {}
+
+    async def run_sampling_loop(self, num_samples: int, interval: float) -> None:
+        """Background coroutine: continuously sample at evenly-spaced intervals.
+
+        Runs alongside the load-based loop via asyncio.gather().
+        sample_interval = interval / num_samples (e.g., 5s / 10 = 0.5s)
+        Keeps only the last num_samples in the buffer (rolling window).
+        """
+        self._num_samples = num_samples
+        sample_interval = interval / num_samples
+        while True:
+            metrics = await self._fetch_and_parse()
+            if metrics:
+                self._sample_buffer.append(metrics)
+                if len(self._sample_buffer) > num_samples:
+                    self._sample_buffer.pop(0)
+            await asyncio.sleep(sample_interval)
+
+    def get_recent_and_averaged_metrics(
+        self, worker_type: str
+    ) -> typing.Optional[
+        tuple[
+            dict[str, dict[str, float]],
+            dict[str, dict[str, float]],
+            dict[str, float],
+        ]
+    ]:
+        """Return recent, per-worker time-averaged, and cluster-averaged metrics.
+
+        Called by the load-based loop at decision time. Non-blocking.
+
+        Args:
+            worker_type: "prefill" or "decode" — only workers matching
+                         the worker_type label are included.
+
+        Returns:
+            A tuple of (recent, per_worker_averaged, cluster_averaged):
+            - recent:              {worker_id: {metric: float}} from the latest sample
+            - per_worker_averaged: {worker_id: {metric: float}} averaged over time per worker
+            - cluster_averaged:    {metric: float} averaged over all samples and all workers
+            Returns None if the sample buffer is empty.
+        """
+        if not self._sample_buffer:
+            return None
+
+        # --- Recent: last sample only ---
+        latest_sample = self._sample_buffer[-1]
+        recent: dict[str, dict[str, float]] = {}
+        for worker_id, metrics in latest_sample.get(worker_type, {}).items():
+            recent[worker_id] = dict(metrics)
+
+        # --- Per-worker averaged: across time, grouped by worker_id ---
+        pw_sums: dict[str, dict[str, float]] = {}
+        pw_counts: dict[str, dict[str, int]] = {}
+
+        for sample in self._sample_buffer:
+            typed_workers = sample.get(worker_type, {})
+            for worker_id, metrics in typed_workers.items():
+                if worker_id not in pw_sums:
+                    pw_sums[worker_id] = {}
+                    pw_counts[worker_id] = {}
+                for metric_name, value in metrics.items():
+                    pw_sums[worker_id][metric_name] = (
+                        pw_sums[worker_id].get(metric_name, 0.0) + value
+                    )
+                    pw_counts[worker_id][metric_name] = (
+                        pw_counts[worker_id].get(metric_name, 0) + 1
+                    )
+
+        if not pw_sums and not recent:
+            return None
+
+        per_worker_averaged: dict[str, dict[str, float]] = {}
+        for worker_id in pw_sums:
+            per_worker_averaged[worker_id] = {}
+            for metric_name in pw_sums[worker_id]:
+                per_worker_averaged[worker_id][metric_name] = (
+                    pw_sums[worker_id][metric_name] / pw_counts[worker_id][metric_name]
+                )
+
+        # --- Cluster averaged: across time AND worker_id ---
+        cluster_sums: dict[str, float] = {}
+        cluster_counts: dict[str, int] = {}
+        for worker_id in pw_sums:
+            for metric_name in pw_sums[worker_id]:
+                cluster_sums[metric_name] = (
+                    cluster_sums.get(metric_name, 0.0) + pw_sums[worker_id][metric_name]
+                )
+                cluster_counts[metric_name] = (
+                    cluster_counts.get(metric_name, 0)
+                    + pw_counts[worker_id][metric_name]
+                )
+
+        cluster_averaged: dict[str, float] = {}
+        for metric_name in cluster_sums:
+            cluster_averaged[metric_name] = (
+                cluster_sums[metric_name] / cluster_counts[metric_name]
+            )
+
+        return recent, per_worker_averaged, cluster_averaged

docs/pages/components/planner/README.md

@@ -8,27 +8,37 @@ title: Planner
 
 The Planner monitors system performance and automatically scales prefill/decode workers to meet latency SLAs. It runs as a component inside the Dynamo inference graph on Kubernetes.
 
+The SLA Planner supports two scaling modes:
+
+- **Throughput-based scaling**: Uses pre-deployment profiling data and traffic prediction to compute the number of replicas needed to meet TTFT and ITL SLA targets. This is the primary scaling mode for production deployments.
+- **Load-based scaling (Experimental)**: Uses real-time per-worker load metrics (active prefill tokens, active KV blocks) from the router to make SLA-aware scaling decisions via online linear regression. Does not require profiling data. Responds quickly to traffic bursts.
+
+When both modes are enabled, throughput-based scaling provides a lower bound on replicas (long-term capacity planning) while load-based scaling handles real-time adjustments (burst response).
+
 > **New to the Planner?** Start with the [SLA Planner Quick Start Guide](planner-guide.md) for a complete workflow including profiling and deployment.
 
 ## Feature Matrix
 
-| Category | Feature | Status |
-|----------|---------|--------|
-| **Backend** | Local (bare metal) | Deprecated |
-| | Kubernetes | Supported |
-| **LLM Framework** | vLLM | Supported |
-| | TensorRT-LLM | Supported |
-| | SGLang | Supported |
-| **Serving Type** | Aggregated | Unsupported |
-| | Disaggregated | Supported |
-| **Scaling Mode** | SLA-based (TTFT/ITL targets) | Supported (primary) |
-| | Load-based (KV cache/queue thresholds) | Deprecated |
-| **Load Predictors** | ARIMA | Supported |
-| | Prophet | Supported |
-| | Kalman filter | Supported |
-| | Constant (current = next) | Supported |
-| **Connectors** | KubernetesConnector (native DGD scaling) | Supported |
-| | VirtualConnector (external environments) | Supported |
+| Feature | Throughput-Based | Load-Based (Experimental) |
+|---------|:----------------:|:-------------------------:|
+| **Deployment** | | |
+| Disaggregated | Supported | Supported |
+| Aggregated | Unsupported | Supported |
+| **LLM Framework** | | |
+| vLLM | Supported | Supported |
+| TensorRT-LLM | Supported | Supported |
+| SGLang | Supported | Supported |
+| **Requires Profiling Data** | Yes | No |
+| **Load Predictors** | ARIMA, Prophet, Kalman, Constant | N/A |
+| **Connectors** | | |
+| KubernetesConnector | Supported | Supported |
+| VirtualConnector | Supported | Supported |
+
+## When to Use Which Mode
+
+- **Throughput-based scaling** should be enabled whenever engine profiling data is available (through pre-deployment profiling). It provides stable, prediction-based capacity planning.
+- **Load-based scaling** should be enabled when traffic is bursty or hard to predict. It reacts quickly to real-time load changes without requiring profiling data.
+- **Both modes together**: For the best of both worlds, enable both. Throughput-based scaling provides a lower bound (long-term capacity), while load-based scaling handles bursts above that floor. When both are enabled, use a longer `--adjustment-interval` for throughput-based scaling.
 
 ## Quick Start
 
@@ -36,21 +46,35 @@ The Planner monitors system performance and automatically scales prefill/decode
 
 - Dynamo platform installed on Kubernetes ([Installation Guide](../../kubernetes/installation-guide.md))
 - kube-prometheus-stack installed ([Metrics Setup](../../kubernetes/observability/metrics.md))
-- Pre-deployment profiling completed ([Profiling Guide](../profiler/profiler-guide.md))
 
-### Deploy with DGDR (Recommended)
+For throughput-based scaling, pre-deployment profiling is also required ([Profiling Guide](../profiler/profiler-guide.md)).
+
+### Throughput-Based Scaling (with DGDR)
 
-The fastest path to a planner-enabled deployment is through a DynamoGraphDeploymentRequest:
+The fastest path to a throughput-based planner deployment is through a DynamoGraphDeploymentRequest, which automatically profiles your model:
 
 ```bash
 kubectl apply -f components/src/dynamo/profiler/deploy/profile_sla_aic_dgdr.yaml -n $NAMESPACE
 ```
 
-This automatically profiles your model and deploys with the SLA planner. See [SLA Planner Guide](planner-guide.md) for the full workflow.
+See [Planner Guide](planner-guide.md) for the full workflow.
+
+### Load-Based Scaling (without profiling)
+
+To deploy with load-based scaling only (no profiling required), add these arguments to the planner service in your DGD:
+
+```yaml
+args:
+  - --enable-loadbased-scaling
+  - --disable-throughput-scaling
+  - --loadbased-adjustment-interval=5
+```
+
+The planner will auto-discover the frontend metrics endpoint from the DGD. See [disagg_planner_load.yaml](../../../../tests/planner/scaling/disagg_planner_load.yaml) for a complete example.
 
-### Deploy with DGD (Manual)
+### Manual DGD Deployment
 
-For manual control, use the disaggregated planner templates:
+For manual control with throughput-based scaling, use the disaggregated planner templates:
 
 ```bash
 # After profiling is complete
@@ -63,9 +87,6 @@ kubectl apply -f examples/backends/vllm/deploy/disagg_planner.yaml -n $NAMESPACE
 |----------|-------------|
 | [Planner Guide](planner-guide.md) | Deployment, configuration, integration, troubleshooting |
 | [Planner Examples](planner-examples.md) | DGDR YAML examples, sample configurations, advanced patterns |
-| [SLA Planner Guide](planner-guide.md) | End-to-end DGDR workflow: define SLAs, profile, deploy, monitor |
-| [SLA-based Planner](planner-guide.md) | Scaling algorithm, correction factors, load prediction details |
-| [Load-based Planner](README.md) | Legacy load-based scaling (deprecated) |
 | [SLA-Driven Profiling](../profiler/profiler-guide.md) | Pre-deployment profiling process and configuration |
 | [Planner Design](../../design-docs/planner-design.md) | Architecture deep-dive for contributors |
 
@@ -75,22 +96,33 @@ kubectl apply -f examples/backends/vllm/deploy/disagg_planner.yaml -n $NAMESPACE
 
 | Argument | Default | Description |
 |----------|---------|-------------|
+| **Common** | | |
 | `--namespace` | `$DYN_NAMESPACE` or `dynamo` | Dynamo logical namespace |
 | `--backend` | `vllm` | Backend framework (`vllm`, `sglang`, `trtllm`) |
+| `--mode` | `disagg` | Planner mode (`disagg`, `prefill`, `decode`, `agg`) |
 | `--environment` | `kubernetes` | Deployment environment |
-| `--adjustment-interval` | `180` | Seconds between scaling decisions |
 | `--ttft` | `500.0` | Target Time To First Token (ms) |
 | `--itl` | `50.0` | Target Inter-Token Latency (ms) |
-| `--isl` | `3000` | Expected average input sequence length |
-| `--osl` | `150` | Expected average output sequence length |
-| `--load-predictor` | `arima` | Prediction model (`arima`, `prophet`, `kalman`, `constant`) |
 | `--max-gpu-budget` | `8` | Maximum GPUs across all workers |
 | `--min-endpoint` | `1` | Minimum replicas per worker type |
 | `--decode-engine-num-gpu` | `1` | GPUs per decode engine |
 | `--prefill-engine-num-gpu` | `1` | GPUs per prefill engine |
 | `--no-operation` | `false` | Observation mode (no actual scaling) |
-| `--no-correction` | `false` | Disable correction factors |
+| **Throughput-based scaling** | | |
+| `--enable-throughput-scaling` | `true` | Enable throughput-based scaling |
+| `--adjustment-interval` | `180` | Seconds between throughput-based scaling decisions |
 | `--profile-results-dir` | `profiling_results` | Path to profiling data (NPZ/JSON) |
+| `--load-predictor` | `arima` | Prediction model (`arima`, `prophet`, `kalman`, `constant`) |
+| `--no-correction` | `false` | Disable correction factors |
+| **Load-based scaling (Experimental)** | | |
+| `--enable-loadbased-scaling` | `false` | Enable load-based scaling |
+| `--disable-throughput-scaling` | `false` | Disable throughput-based scaling (required for `agg` mode) |
+| `--loadbased-router-metrics-url` | auto-discovered | URL to router's `/metrics` endpoint |
+| `--loadbased-adjustment-interval` | `5` | Seconds between load-based scaling decisions |
+| `--loadbased-learning-window` | `50` | Sliding window size for regression model |
+| `--loadbased-scaling-down-sensitivity` | `80` | Scale-down sensitivity 0-100 (0=never, 100=aggressive) |
+| `--loadbased-metric-samples` | `10` | Number of metric samples per adjustment interval |
+| `--loadbased-min-observations` | `5` | Minimum observations before regression activates |
 
 ### Environment Variables
 
@@ -119,7 +151,12 @@ The dashboard shows:
 
 ### Prometheus Metrics
 
-The planner queries the frontend's `/metrics` endpoint via Prometheus. Required metrics:
+**Throughput-based scaling** pulls traffic metrics from the cluster-wide Prometheus server:
 - Request count and duration
 - TTFT and ITL distributions
 - Input/output sequence lengths
+
+**Load-based scaling** pulls per-engine status directly from the frontend's `/metrics` endpoint:
+- Active prefill tokens per worker
+- Active decode blocks per worker
+- Last observed TTFT, ITL, and ISL per worker

docs/pages/components/planner/planner-examples.md

@@ -4,9 +4,9 @@
 title: Planner Examples
 ---
 
-# Planner Examples
+# Planner Examples: Throughput-Based Scaling
 
-Practical examples for deploying the SLA Planner with different configurations. For deployment concepts, see the [Planner Guide](planner-guide.md). For a quick overview, see the [Planner README](README.md).
+Practical examples for deploying the SLA Planner with throughput-based scaling. All examples below use the DGDR workflow with pre-deployment profiling. For deployment concepts, see the [Planner Guide](planner-guide.md). For a quick overview, see the [Planner README](README.md).
 
 ## Basic Examples
 

docs/pages/components/planner/planner-guide.md

@@ -8,6 +8,28 @@ title: Planner Guide
 
 Deployment, configuration, and integration guide for the Dynamo SLA Planner. For a quick overview, see the [Planner README](README.md). For architecture internals, see [Planner Design](../../design-docs/planner-design.md).
 
+## Scaling Modes
+
+The SLA Planner supports two scaling modes:
+
+- **Throughput-based scaling**: Uses pre-deployment profiling data and traffic prediction. Best for stable, predictable workloads where profiling data is available.
+- **Load-based scaling (Experimental)**: Uses real-time per-worker engine metrics and online regression. Best for bursty or unpredictable traffic. Does not require profiling data.
+
+**When to use which mode:**
+- Enable **throughput-based scaling** whenever engine profiling data is available. It provides stable, prediction-based capacity planning.
+- Enable **load-based scaling** when traffic is bursty or hard to predict. It reacts quickly to real-time load changes.
+- Enable **both modes together** for the best of both worlds: throughput-based scaling provides a lower bound (long-term capacity), while load-based scaling handles bursts above that floor. When both are enabled, use a longer `--adjustment-interval` for throughput-based scaling.
+
+**DGDR and scaling modes:** Deploying via DGDR automatically triggers profiling and enables throughput-based scaling. To additionally enable load-based scaling, pass the planner arguments through the DGDR's planner config section:
+
+```yaml
+profilingConfig:
+  config:
+    planner:
+      plannerEnableLoadbasedScaling: true
+      plannerLoadbasedAdjustmentInterval: 5
+```
+
 ## Deployment
 
 ### Prerequisites
@@ -191,7 +213,7 @@ For detailed comparison, supported configurations, and limitations, see [SLA-Dri
 
 ### Load Predictors
 
-The SLA planner forecasts the number of requests, ISL, and OSL in the next adjustment interval. Four prediction models are supported:
+The throughput-based scaling mode forecasts the number of requests, ISL, and OSL in the next adjustment interval. Four prediction models are supported:
 
 #### Constant Predictor
 - **Use case**: Stable workloads with long prediction intervals
@@ -231,15 +253,13 @@ You can warm-start load predictors with a mooncake-style JSONL trace file:
 - **CLI argument**: `--load-predictor-warmup-trace <path/to/trace.jsonl>`
 - **Effect**: preloads predictors with historical request-count / ISL / OSL samples extracted from the trace
 
-### Planner Scaling Parameters
+### Throughput-Based Scaling Parameters
 
 | Argument | Default | Description |
 |----------|---------|-------------|
 | `--adjustment-interval` | `180` | Seconds between scaling decisions |
 | `--ttft` | `500.0` | Target Time To First Token (ms) |
 | `--itl` | `50.0` | Target Inter-Token Latency (ms) |
-| `--isl` | `3000` | Expected average input sequence length |
-| `--osl` | `150` | Expected average output sequence length |
 | `--max-gpu-budget` | `8` | Maximum GPUs across all workers |
 | `--min-endpoint` | `1` | Minimum replicas per worker type |
 | `--decode-engine-num-gpu` | `1` | GPUs per decode engine |
@@ -247,6 +267,8 @@ You can warm-start load predictors with a mooncake-style JSONL trace file:
 | `--no-operation` | `false` | Observation mode (no actual scaling) |
 | `--no-correction` | `false` | Disable correction factors |
 
+For the full list of arguments including load-based scaling options, see the [Planner README](README.md#key-arguments).
+
 #### Planner Configuration Passthrough
 
 Add planner-specific settings in the DGDR:

docs/pages/design-docs/planner-design.md

@@ -10,9 +10,9 @@ title: Planner Design
 
 ## Overview
 
-The Planner is Dynamo's autoscaling controller. It observes system metrics, predicts future load, and adjusts prefill/decode worker replica counts to proactively meet SLA targets. This document covers the internal architecture, algorithms, and design trade-offs.
+The Planner is Dynamo's autoscaling controller. It supports two scaling modes: **throughput-based** (using profiling data and traffic prediction) and **load-based** (using real-time engine metrics and online regression). This document covers the internal architecture, algorithms, and design trade-offs for both modes.
 
-## Architecture
+## Throughput-Based Scaling
 
 ![Planner architecture showing Metric Collector, Load Predictor, and Performance Interpolator feeding into the Scaling Algorithm and Connector Layer](../../assets/img/planner-architecture.svg)
 
@@ -167,17 +167,48 @@ After the delay:
 - **Interpolation accuracy vs profiling cost**: Higher `prefillInterpolationGranularity` and `decodeInterpolationGranularity` in the profiling sweep produce more accurate interpolation but increase profiling time linearly. Default granularity (16 prefill, 6 decode) balances accuracy with profiling duration.
 - **Predictor warm-up period**: All predictors need observation history before making reliable forecasts. ARIMA and Prophet need multiple adjustment intervals of data. Kalman starts forecasting after `--kalman-min-points` observations. During warm-up, the planner uses the constant predictor as fallback.
 
+## Load-Based Scaling (Experimental)
+
+The load-based mode uses real-time per-worker metrics from the router to make SLA-aware scaling decisions without requiring profiling data.
+
+### Metrics
+
+The planner pulls per-worker load metrics directly from the frontend's `/metrics` endpoint:
+- **Active prefill tokens**: pending prefill tokens per worker
+- **Active decode blocks**: active KV blocks per worker
+- **Last TTFT, ITL, ISL**: most recent observed latencies per worker
+
+### Regression Model
+
+A sliding-window linear regression maps load to latency:
+- Prefill: `(active_prefill_tokens + ISL)` -> `TTFT`
+- Decode: `active_decode_blocks` -> `ITL`
+
+Given a TTFT/ITL SLA target, the model reverse-solves for the maximum load that satisfies the SLA.
+
+### Scaling Decisions
+
+- **Scale up**: if ALL workers' recent load exceeds the regression-derived target
+- **Scale down**: if ALL workers' recent load is below the target adjusted by `(num_workers - 1) / num_workers * sensitivity / 100`
+- Only scales by +/-1 per interval (blocking)
+
+### Co-existence with Throughput-Based Scaling
+
+When both modes are enabled, throughput-based scaling (longer interval) sets a lower bound on replicas while load-based scaling (shorter interval) handles real-time adjustments above that floor.
+
+### Aggregated Mode
+
+In aggregated mode (`--mode agg`), engines handle both prefill and decode via chunked prefill. The planner maintains both TTFT and ITL regression models but uses per-worker time-averaged metrics (not instantaneous) for regression training to smooth out chunked prefill noise. Scale up if either prefill or decode signals overload; scale down only if both signal underload.
+
 ## Known Limitations
 
 1. **30-second startup delay**: Hardcoded wait for component registration. It should be replaced with runtime readiness probing.
 2. **Adjustment interval vs scaling latency**: If `adjustment_interval` \< time to scale, scaling decisions can pile up. The planner logs warnings but doesn't queue.
-3. **Average-based interpolation**: The planner uses average ISL/OSL, which may not represent bimodal or heavy-tailed distributions well.
+3. **Average-based interpolation**: Throughput-based scaling uses average ISL/OSL, which may not represent bimodal or heavy-tailed distributions well.
 4. **Single DGD scope**: Each planner instance manages exactly one DGD. Multi-model/multi-DGD coordination is not supported.
-5. **Load-based planner deprecated**: The load-based code path exists but is non-functional with current backends (no prefill queue metrics).
 
 ## Future Work
 
-- Support aggregated (non-disaggregated) scaling mode for single-worker deployments
 - Multi-DGD coordination for shared-cluster scenarios
 - Distribution-aware interpolation (beyond mean ISL/OSL)
 - Adaptive adjustment interval based on observed scaling latency
@@ -185,17 +216,22 @@ After the delay:
 ## File Map
 
 
-| File                         | Size | Purpose                                               |
-| ---------------------------- | ---- | ----------------------------------------------------- |
-| `planner_core.py`            | 36k  | Main scaling loop, algorithm implementation           |
-| `perf_interpolation.py`      | 13k  | NPZ data loading and throughput/latency interpolation |
-| `load_predictor.py`          | 16k  | ARIMA, Prophet, Kalman, Constant predictors           |
-| `pre_swept_results_utils.py` | 12k  | Pre-computed H100/H200 profiling data loader          |
-| `kubernetes_connector.py`    | 11k  | K8s API integration for DGD scaling                   |
-| `kube.py`                    | 7.4k | Low-level K8s client wrapper                          |
-| `exceptions.py`              | 7.2k | Custom exception hierarchy                            |
-| `prometheus.py`              | 7.3k | Prometheus query builder and client                   |
-| `defaults.py`                | 8.1k | Default configs, backend name mappings                |
-| `planner_argparse.py`        | 6.2k | CLI argument definitions                              |
+| File                         | Purpose                                               |
+| ---------------------------- | ----------------------------------------------------- |
+| `planner_core.py`            | Base planner, shared scaling loop, algorithm core     |
+| `disagg_planner.py`          | Disaggregated mode orchestrator (prefill + decode)    |
+| `agg_planner.py`             | Aggregated mode orchestrator (load-based only)        |
+| `prefill_planner.py`         | Prefill-specific scaling logic                        |
+| `decode_planner.py`          | Decode-specific scaling logic                         |
+| `load_based_regression.py`   | Sliding-window linear regression for load-based scaling |
+| `prometheus.py`              | Prometheus/router metrics clients, data classes       |
+| `perf_interpolation.py`      | NPZ data loading and throughput/latency interpolation |
+| `load_predictor.py`          | ARIMA, Prophet, Kalman, Constant predictors           |
+| `pre_swept_results_utils.py` | Pre-computed H100/H200 profiling data loader          |
+| `kubernetes_connector.py`    | K8s API integration for DGD scaling                   |
+| `kube.py`                    | Low-level K8s client wrapper                          |
+| `exceptions.py`              | Custom exception hierarchy                            |
+| `defaults.py`                | Default configs, backend name mappings                |
+| `planner_argparse.py`        | CLI argument definitions                              |
 
 

scripts/report_pytest_markers.py

@@ -112,6 +112,10 @@ STUB_MODULES = [
     "gpu_memory_service",
     "gpu_memory_service.common",
     "gpu_memory_service.common.utils",
+    "prometheus_client",
+    "prometheus_client.parser",
+    "sklearn",
+    "sklearn.linear_model",
 ]
 
 # Project paths for local imports

tests/planner/scaling/disagg_planner_load.yaml

+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+apiVersion: nvidia.com/v1alpha1
+kind: DynamoGraphDeployment
+metadata:
+  name: vllm-disagg-planner
+spec:
+  services:
+    Frontend:
+      componentType: frontend
+      replicas: 1
+      extraPodSpec:
+        mainContainer:
+          image: nvcr.io/nvidia/ai-dynamo/vllm-runtime:my-tag
+          workingDir: /workspace/examples/backends/vllm
+          command:
+            - python3
+          args:
+            - -m
+            - dynamo.frontend
+            - --router-mode
+            - kv
+    Planner:
+      componentType: planner
+      replicas: 1
+      extraPodSpec:
+        mainContainer:
+          image: nvcr.io/nvidia/ai-dynamo/vllm-runtime:my-tag
+          workingDir: /workspace/components/src/dynamo/planner
+          command:
+          - python3
+          - -m
+          - planner_sla
+          args:
+            - --environment=kubernetes
+            - --backend=vllm
+            - --enable-loadbased-scaling
+            - --disable-throughput-scaling
+            - --loadbased-adjustment-interval=5
+            - --loadbased-min-observations=5
+    VllmDecodeWorker:
+      envFromSecret: hf-token-secret
+      componentType: worker
+      subComponentType: decode
+      replicas: 1
+      resources:
+        limits:
+          gpu: "1"
+      extraPodSpec:
+        mainContainer:
+          image: nvcr.io/nvidia/ai-dynamo/vllm-runtime:my-tag
+          workingDir: /workspace/examples/backends/vllm
+          command:
+            - python3
+          args:
+            - -m
+            - dynamo.vllm
+            - --model
+            - nvidia/Llama-3.1-8B-Instruct-FP8
+    VllmPrefillWorker:
+      envFromSecret: hf-token-secret
+      componentType: worker
+      subComponentType: prefill
+      replicas: 1
+      resources:
+        limits:
+          gpu: "1"
+      extraPodSpec:
+        mainContainer:
+          image: nvcr.io/nvidia/ai-dynamo/vllm-runtime:my-tag
+          workingDir: /workspace/examples/backends/vllm
+          command:
+            - python3
+          args:
+            - -m
+            - dynamo.vllm
+            - --model
+            - nvidia/Llama-3.1-8B-Instruct-FP8
+            - --is-prefill-worker