feat(runtime): add hierarchical Model/WorkerSet architecture for multi-namespace support (#6054)

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

components/src/dynamo/common/configuration/groups/runtime_args.py

@@ -9,6 +9,7 @@ from dynamo._core import get_reasoning_parser_names, get_tool_parser_names
 from dynamo.common.configuration.arg_group import ArgGroup
 from dynamo.common.configuration.config_base import ConfigBase
 from dynamo.common.configuration.utils import add_argument, add_negatable_bool_argument
+from dynamo.common.utils.namespace import get_worker_namespace
 from dynamo.common.utils.output_modalities import OutputModality
 
 
@@ -35,6 +36,8 @@ class DynamoRuntimeConfig(ConfigBase):
     media_output_http_url: Optional[str] = None
 
     def validate(self) -> None:
+        self.namespace = get_worker_namespace(self.namespace)
+
         # TODO  get a better way for spot fixes like this.
         self.enable_local_indexer = not self.durable_kv_events
         self._validate_output_modalities()
@@ -69,7 +72,8 @@ class DynamoRuntimeArgGroup(ArgGroup):
             flag_name="--namespace",
             env_var="DYN_NAMESPACE",
             default="dynamo",
-            help="Dynamo namespace",
+            help="Dynamo namespace. If DYN_NAMESPACE_WORKER_SUFFIX is set, "
+            "'-{suffix}' is appended to support multiple worker pools",
         )
         add_argument(
             g,

components/src/dynamo/common/utils/__init__.py

@@ -17,6 +17,7 @@ Submodules:
 from dynamo.common.utils import (
     endpoint_types,
     engine_response,
+    namespace,
     otel_tracing,
     paths,
     prometheus,
@@ -26,6 +27,7 @@ from dynamo.common.utils import (
 __all__ = [
     "endpoint_types",
     "engine_response",
+    "namespace",
     "otel_tracing",
     "paths",
     "prometheus",

components/src/dynamo/common/utils/namespace.py

+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+import os
+from typing import Optional
+
+
+def get_worker_namespace(namespace: Optional[str] = None) -> str:
+    """Get the Dynamo namespace for a worker.
+
+    Uses the provided namespace, or falls back to the DYN_NAMESPACE environment
+    variable (defaulting to "dynamo"). If DYN_NAMESPACE_WORKER_SUFFIX is set,
+    it is appended as "{namespace}-{suffix}" to support multiple sets of workers
+    for the same model.
+    """
+    if not namespace:
+        namespace = os.environ.get("DYN_NAMESPACE", "dynamo")
+
+    suffix = os.environ.get("DYN_NAMESPACE_WORKER_SUFFIX")
+    if suffix:
+        namespace = f"{namespace}-{suffix}"
+    return namespace

components/src/dynamo/frontend/frontend_args.py

@@ -54,6 +54,7 @@ class FrontendConfig(ConfigBase):
     router_max_tree_size: int
     router_prune_target_ratio: float
     namespace: Optional[str] = None
+    namespace_prefix: Optional[str] = None
     router_replica_sync: bool
     router_snapshot_threshold: int
     router_reset_states: bool
@@ -128,9 +129,8 @@ class FrontendArgGroup(ArgGroup):
             env_var="DYN_NAMESPACE",
             default=None,
             help=(
-                "Dynamo namespace for model discovery scoping. If specified, models will "
-                "only be discovered from this namespace. If not specified, discovers models "
-                "from all namespaces (global discovery)."
+                "Dynamo namespace for model discovery scoping. Use for exact namespace matching. "
+                "If --namespace-prefix is also specified, prefix takes precedence."
             ),
         )
 
@@ -256,6 +256,18 @@ class FrontendArgGroup(ArgGroup):
             arg_type=float,
         )
 
+        add_argument(
+            g,
+            flag_name="--namespace-prefix",
+            env_var="DYN_NAMESPACE_PREFIX",
+            default=None,
+            help=(
+                "Dynamo namespace prefix for model discovery scoping. Discovers models from "
+                "namespaces starting with this prefix (e.g., 'ns' matches 'ns', 'ns-abc123', "
+                "'ns-def456'). Takes precedence over --namespace if both are specified."
+            ),
+        )
+
         add_negatable_bool_argument(
             g,
             flag_name="--router-replica-sync",

components/src/dynamo/frontend/main.py

@@ -230,6 +230,8 @@ async def async_main():
         kwargs["tls_key_path"] = config.tls_key_path
     if config.namespace:
         kwargs["namespace"] = config.namespace
+    if config.namespace_prefix:
+        kwargs["namespace_prefix"] = config.namespace_prefix
     if config.kserve_grpc_server and config.grpc_metrics_port:
         kwargs["http_metrics_port"] = config.grpc_metrics_port
 

components/src/dynamo/mocker/args.py

@@ -8,6 +8,8 @@ import os
 import tempfile
 from pathlib import Path
 
+from dynamo.common.utils.namespace import get_worker_namespace
+
 from . import __version__
 from .utils.planner_profiler_perf_data_converter import (
     convert_profile_results_to_npz,
@@ -15,7 +17,7 @@ from .utils.planner_profiler_perf_data_converter import (
     is_profile_results_dir,
 )
 
-DYN_NAMESPACE = os.environ.get("DYN_NAMESPACE", "dynamo")
+DYN_NAMESPACE = get_worker_namespace()
 DEFAULT_ENDPOINT = f"dyn://{DYN_NAMESPACE}.backend.generate"
 DEFAULT_PREFILL_ENDPOINT = f"dyn://{DYN_NAMESPACE}.prefill.generate"
 

components/src/dynamo/trtllm/configs/diffusion_config.py

@@ -7,11 +7,12 @@ This module defines the DiffusionConfig dataclass used for configuring
 video and image diffusion workers.
 """
 
-import os
 from dataclasses import dataclass
 from typing import Optional
 
-DYN_NAMESPACE = os.environ.get("DYN_NAMESPACE", "dynamo")
+from dynamo.common.utils.namespace import get_worker_namespace
+
+DYN_NAMESPACE = get_worker_namespace()
 
 # Default model paths
 DEFAULT_VIDEO_MODEL_PATH = "Wan-AI/Wan2.1-T2V-1.3B-Diffusers"

lib/bindings/c/src/lib.rs

@@ -704,6 +704,7 @@ pub unsafe extern "C" fn create_routers(
                     Some(prefill_config),
                     enforce_disagg,
                     model_name.clone(),
+                    namespace_str.clone(),
                 )
             }
             None if enforce_disagg => {

lib/bindings/python/rust/llm/entrypoint.rs

@@ -182,6 +182,7 @@ pub(crate) struct EntrypointArgs {
     tls_key_path: Option<PathBuf>,
     extra_engine_args: Option<PathBuf>,
     namespace: Option<String>,
+    namespace_prefix: Option<String>,
     is_prefill: bool,
     migration_limit: u32,
     chat_engine_factory: Option<PyEngineFactory>,
@@ -191,7 +192,7 @@ pub(crate) struct EntrypointArgs {
 impl EntrypointArgs {
     #[allow(clippy::too_many_arguments)]
     #[new]
-    #[pyo3(signature = (engine_type, model_path=None, model_name=None, endpoint_id=None, context_length=None, template_file=None, router_config=None, kv_cache_block_size=None, http_host=None, http_port=None, http_metrics_port=None, tls_cert_path=None, tls_key_path=None, extra_engine_args=None, namespace=None, is_prefill=false, migration_limit=0, chat_engine_factory=None))]
+    #[pyo3(signature = (engine_type, model_path=None, model_name=None, endpoint_id=None, context_length=None, template_file=None, router_config=None, kv_cache_block_size=None, http_host=None, http_port=None, http_metrics_port=None, tls_cert_path=None, tls_key_path=None, extra_engine_args=None, namespace=None, namespace_prefix=None, is_prefill=false, migration_limit=0, chat_engine_factory=None))]
     pub fn new(
         py: Python<'_>,
         engine_type: EngineType,
@@ -209,6 +210,7 @@ impl EntrypointArgs {
         tls_key_path: Option<PathBuf>,
         extra_engine_args: Option<PathBuf>,
         namespace: Option<String>,
+        namespace_prefix: Option<String>,
         is_prefill: bool,
         migration_limit: u32,
         chat_engine_factory: Option<PyObject>,
@@ -254,6 +256,7 @@ impl EntrypointArgs {
             tls_key_path,
             extra_engine_args,
             namespace,
+            namespace_prefix,
             is_prefill,
             migration_limit,
             chat_engine_factory,
@@ -296,7 +299,8 @@ pub fn make_engine<'p>(
         .tls_key_path(args.tls_key_path.clone())
         .is_mocker(matches!(args.engine_type, EngineType::Mocker))
         .extra_engine_args(args.extra_engine_args.clone())
-        .namespace(args.namespace.clone());
+        .namespace(args.namespace.clone())
+        .namespace_prefix(args.namespace_prefix.clone());
     pyo3_async_runtimes::tokio::future_into_py(py, async move {
         if let Some(model_path) = args.model_path.clone() {
             let local_path = if model_path.exists() {

lib/llm/src/discovery.rs

 // SPDX-FileCopyrightText: Copyright (c) 2024-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 // SPDX-License-Identifier: Apache-2.0
 
+mod model;
+pub use model::Model;
+
 mod model_manager;
 pub use model_manager::{ModelManager, ModelManagerError};
 
+mod worker_set;
+pub use worker_set::WorkerSet;
+
 pub(crate) mod runtime_configs;
 pub use runtime_configs::{RuntimeConfigWatch, runtime_config_watch};
 

lib/llm/src/discovery/model.rs

+// SPDX-FileCopyrightText: Copyright (c) 2024-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+//! A Model represents a named model (e.g., "llama-3-70b") that may be served by
+//! one or more WorkerSets. Each WorkerSet corresponds to a namespace.
+//!
+//! Requests are routed to a WorkerSet selected by weighted random (proportional to worker count).
+
+use std::sync::{Arc, OnceLock};
+
+use dashmap::DashMap;
+use rand::Rng;
+
+use super::worker_monitor::LoadThresholdConfig;
+use super::worker_set::WorkerSet;
+use super::{KvWorkerMonitor, ModelManagerError};
+use crate::protocols::openai::ParsingOptions;
+
+use crate::types::{
+    generic::tensor::TensorStreamingEngine,
+    openai::{
+        chat_completions::OpenAIChatCompletionsStreamingEngine,
+        completions::OpenAICompletionsStreamingEngine, embeddings::OpenAIEmbeddingsStreamingEngine,
+        images::OpenAIImagesStreamingEngine, videos::OpenAIVideosStreamingEngine,
+    },
+};
+
+/// A named model backed by one or more WorkerSets.
+pub struct Model {
+    name: String,
+    worker_sets: DashMap<String, Arc<WorkerSet>>,
+    /// The canonical MDC checksum for this model. Set by the first WorkerSet registered;
+    /// all subsequent WorkerSets must match. Naturally cleared when the Model is dropped
+    /// (last WorkerSet removed), allowing a new version to register.
+    canonical_checksum: OnceLock<String>,
+}
+
+impl Model {
+    pub fn new(name: String) -> Self {
+        Self {
+            name,
+            worker_sets: DashMap::new(),
+            canonical_checksum: OnceLock::new(),
+        }
+    }
+
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    /// Add a WorkerSet to this model. Returns `Err` if the WorkerSet's checksum
+    /// doesn't match the model's canonical checksum (set by the first WorkerSet).
+    pub fn add_worker_set(
+        &self,
+        namespace: String,
+        worker_set: Arc<WorkerSet>,
+    ) -> Result<(), ModelManagerError> {
+        self.set_canonical_checksum(worker_set.mdcsum())?;
+        tracing::info!(
+            model = %self.name,
+            namespace = %namespace,
+            "Adding worker set to model"
+        );
+        self.worker_sets.insert(namespace, worker_set);
+        Ok(())
+    }
+
+    pub fn remove_worker_set(&self, namespace: &str) -> Option<Arc<WorkerSet>> {
+        let removed = self.worker_sets.remove(namespace).map(|(_, ws)| ws);
+        if removed.is_some() {
+            tracing::info!(
+                model = %self.name,
+                namespace = %namespace,
+                remaining_sets = self.worker_sets.len(),
+                "Removed worker set from model"
+            );
+        }
+        removed
+    }
+
+    pub fn has_worker_set(&self, namespace: &str) -> bool {
+        self.worker_sets.contains_key(namespace)
+    }
+
+    pub fn get_worker_set(&self, namespace: &str) -> Option<Arc<WorkerSet>> {
+        self.worker_sets
+            .get(namespace)
+            .map(|entry| entry.value().clone())
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.worker_sets.is_empty()
+    }
+
+    pub fn worker_set_count(&self) -> usize {
+        self.worker_sets.len()
+    }
+
+    /// Check if this model has any decode engine (chat or completions) across any WorkerSet.
+    pub fn has_decode_engine(&self) -> bool {
+        self.worker_sets
+            .iter()
+            .any(|entry| entry.value().has_decode_engine())
+    }
+
+    /// Check if this model tracks prefill (any WorkerSet is a prefill set).
+    pub fn has_prefill(&self) -> bool {
+        self.worker_sets
+            .iter()
+            .any(|entry| entry.value().is_prefill_set())
+    }
+
+    /// Check if any WorkerSet has a chat engine.
+    pub fn has_chat_engine(&self) -> bool {
+        self.worker_sets
+            .iter()
+            .any(|entry| entry.value().has_chat_engine())
+    }
+
+    /// Check if any WorkerSet has a completions engine.
+    pub fn has_completions_engine(&self) -> bool {
+        self.worker_sets
+            .iter()
+            .any(|entry| entry.value().has_completions_engine())
+    }
+
+    /// Check if any WorkerSet has an embeddings engine.
+    pub fn has_embeddings_engine(&self) -> bool {
+        self.worker_sets
+            .iter()
+            .any(|entry| entry.value().has_embeddings_engine())
+    }
+
+    /// Check if any WorkerSet has a tensor engine.
+    pub fn has_tensor_engine(&self) -> bool {
+        self.worker_sets
+            .iter()
+            .any(|entry| entry.value().has_tensor_engine())
+    }
+
+    /// Check if any WorkerSet has an images engine.
+    pub fn has_images_engine(&self) -> bool {
+        self.worker_sets
+            .iter()
+            .any(|entry| entry.value().has_images_engine())
+    }
+
+    /// Check if any WorkerSet has a videos engine.
+    pub fn has_videos_engine(&self) -> bool {
+        self.worker_sets
+            .iter()
+            .any(|entry| entry.value().has_videos_engine())
+    }
+
+    /// Check if a candidate checksum is valid for this model.
+    /// Returns `Some(true)` if it matches the canonical checksum, `Some(false)` if it
+    /// doesn't match, or `None` if no canonical checksum has been set yet (no WorkerSets).
+    pub fn is_valid_checksum(&self, candidate: &str) -> Option<bool> {
+        let canonical = self.canonical_checksum.get()?;
+        Some(canonical == candidate)
+    }
+
+    /// Set the canonical checksum for this model. The first caller wins (OnceLock).
+    /// Returns `Err` if a different checksum was already set.
+    fn set_canonical_checksum(&self, checksum: &str) -> Result<(), ModelManagerError> {
+        // Try to set; if already set, verify it matches.
+        match self.canonical_checksum.set(checksum.to_string()) {
+            Ok(()) => Ok(()),
+            Err(_) => {
+                // OnceLock was already set — check if the value matches
+                let canonical = self.canonical_checksum.get().unwrap();
+                if canonical == checksum {
+                    Ok(())
+                } else {
+                    Err(ModelManagerError::ChecksumMismatch {
+                        model: self.name.clone(),
+                        expected: canonical.clone(),
+                        got: checksum.to_string(),
+                    })
+                }
+            }
+        }
+    }
+
+    // -- Engine accessors: select a WorkerSet, return its engine --
+
+    pub fn get_chat_engine(
+        &self,
+    ) -> Result<OpenAIChatCompletionsStreamingEngine, ModelManagerError> {
+        self.select_worker_set_with(|ws| ws.chat_engine.clone())
+            .ok_or_else(|| ModelManagerError::ModelNotFound(self.name.clone()))
+    }
+
+    pub fn get_completions_engine(
+        &self,
+    ) -> Result<OpenAICompletionsStreamingEngine, ModelManagerError> {
+        self.select_worker_set_with(|ws| ws.completions_engine.clone())
+            .ok_or_else(|| ModelManagerError::ModelNotFound(self.name.clone()))
+    }
+
+    pub fn get_embeddings_engine(
+        &self,
+    ) -> Result<OpenAIEmbeddingsStreamingEngine, ModelManagerError> {
+        self.select_worker_set_with(|ws| ws.embeddings_engine.clone())
+            .ok_or_else(|| ModelManagerError::ModelNotFound(self.name.clone()))
+    }
+
+    pub fn get_images_engine(&self) -> Result<OpenAIImagesStreamingEngine, ModelManagerError> {
+        self.select_worker_set_with(|ws| ws.images_engine.clone())
+            .ok_or_else(|| ModelManagerError::ModelNotFound(self.name.clone()))
+    }
+
+    pub fn get_videos_engine(&self) -> Result<OpenAIVideosStreamingEngine, ModelManagerError> {
+        self.select_worker_set_with(|ws| ws.videos_engine.clone())
+            .ok_or_else(|| ModelManagerError::ModelNotFound(self.name.clone()))
+    }
+
+    pub fn get_tensor_engine(&self) -> Result<TensorStreamingEngine, ModelManagerError> {
+        self.select_worker_set_with(|ws| ws.tensor_engine.clone())
+            .ok_or_else(|| ModelManagerError::ModelNotFound(self.name.clone()))
+    }
+
+    // -- Combined engine + parsing options (atomically from one WorkerSet) --
+
+    pub fn get_chat_engine_with_parsing(
+        &self,
+    ) -> Result<(OpenAIChatCompletionsStreamingEngine, ParsingOptions), ModelManagerError> {
+        self.select_worker_set_with(|ws| ws.chat_engine.clone().map(|e| (e, ws.parsing_options())))
+            .ok_or_else(|| ModelManagerError::ModelNotFound(self.name.clone()))
+    }
+
+    pub fn get_completions_engine_with_parsing(
+        &self,
+    ) -> Result<(OpenAICompletionsStreamingEngine, ParsingOptions), ModelManagerError> {
+        self.select_worker_set_with(|ws| {
+            ws.completions_engine
+                .clone()
+                .map(|e| (e, ws.parsing_options()))
+        })
+        .ok_or_else(|| ModelManagerError::ModelNotFound(self.name.clone()))
+    }
+
+    // -- Worker monitoring (aggregated across WorkerSets) --
+
+    /// Get load threshold config from the first WorkerSet that has a monitor.
+    /// When `config` is Some, updates ALL monitors (each WorkerSet has its own).
+    pub fn load_threshold_config(
+        &self,
+        config: Option<&LoadThresholdConfig>,
+    ) -> Option<LoadThresholdConfig> {
+        let mut result = None;
+        for entry in self.worker_sets.iter() {
+            if let Some(ref monitor) = entry.value().worker_monitor {
+                if let Some(cfg) = config {
+                    monitor.set_load_threshold_config(cfg);
+                }
+                if result.is_none() {
+                    result = Some(monitor.load_threshold_config());
+                }
+            }
+        }
+        result
+    }
+
+    /// Get the worker monitor for a specific namespace's WorkerSet.
+    pub fn get_worker_monitor_for_namespace(&self, namespace: &str) -> Option<KvWorkerMonitor> {
+        self.worker_sets
+            .get(namespace)
+            .and_then(|entry| entry.value().worker_monitor.clone())
+    }
+
+    /// Total worker count across all WorkerSets.
+    pub fn total_workers(&self) -> usize {
+        self.worker_sets
+            .iter()
+            .map(|entry| entry.value().worker_count())
+            .sum()
+    }
+
+    // -- Internal selection --
+
+    /// Select a WorkerSet and extract a value from it.
+    ///
+    /// When there's only one set (steady state), returns from that set directly.
+    /// With multiple sets, uses weighted random selection proportional
+    /// to worker count, filtering to sets that have the requested engine.
+    ///
+    /// The `extract` closure should return `Some(value)` if the WorkerSet has the
+    /// desired engine, or `None` if it doesn't.
+    fn select_worker_set_with<T, F>(&self, extract: F) -> Option<T>
+    where
+        F: Fn(&WorkerSet) -> Option<T>,
+    {
+        // Fast path: single set (same zero-worker filtering as the multi-set path below)
+        // TODO: When the single set has 0 workers, this returns None which maps to
+        // ModelNotFound (404). Ideally should be 503 "no available workers" — see follow-up.
+        if self.worker_sets.len() == 1 {
+            return self.worker_sets.iter().next().and_then(|entry| {
+                let ws = entry.value();
+                if ws.worker_count() == 0 {
+                    return None;
+                }
+                extract(ws)
+            });
+        }
+
+        // Collect eligible sets with their worker counts, skipping sets with no workers.
+        // In-process models (no discovery watcher) return count=1, so they always participate.
+        // Discovery models with count=0 have no available workers and are skipped.
+        let eligible: Vec<(T, usize)> = self
+            .worker_sets
+            .iter()
+            .filter_map(|entry| {
+                let ws = entry.value();
+                let count = ws.worker_count();
+                if count == 0 {
+                    return None;
+                }
+                extract(ws).map(|val| (val, count))
+            })
+            .collect();
+
+        if eligible.is_empty() {
+            return None;
+        }
+
+        if eligible.len() == 1 {
+            return eligible.into_iter().next().map(|(val, _)| val);
+        }
+
+        // Weighted random selection proportional to worker count
+        let total_weight: usize = eligible.iter().map(|(_, w)| w).sum();
+        let mut pick = rand::rng().random_range(0..total_weight);
+        for (val, weight) in eligible {
+            if pick < weight {
+                return Some(val);
+            }
+            pick -= weight;
+        }
+        // Should not reach here, but fallback to None
+        None
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::model_card::ModelDeploymentCard;
+    use tokio::sync::watch;
+
+    fn make_worker_set(namespace: &str, mdcsum: &str) -> Arc<WorkerSet> {
+        Arc::new(WorkerSet::new(
+            namespace.to_string(),
+            mdcsum.to_string(),
+            ModelDeploymentCard::default(),
+        ))
+    }
+
+    /// Create a WorkerSet backed by a watch channel so worker_count reflects the vec length.
+    fn make_worker_set_with_count(
+        namespace: &str,
+        mdcsum: &str,
+        worker_ids: Vec<u64>,
+    ) -> (Arc<WorkerSet>, watch::Sender<Vec<u64>>) {
+        let (tx, rx) = watch::channel(worker_ids);
+        let mut ws = WorkerSet::new(
+            namespace.to_string(),
+            mdcsum.to_string(),
+            ModelDeploymentCard::default(),
+        );
+        ws.set_instance_watcher(rx);
+        (Arc::new(ws), tx)
+    }
+
+    #[test]
+    fn test_model_new() {
+        let model = Model::new("llama".to_string());
+        assert_eq!(model.name(), "llama");
+        assert!(model.is_empty());
+        assert_eq!(model.worker_set_count(), 0);
+    }
+
+    #[test]
+    fn test_add_remove_worker_set() {
+        let model = Model::new("llama".to_string());
+        let ws = make_worker_set("ns1", "abc");
+
+        model.add_worker_set("ns1".to_string(), ws).unwrap();
+        assert!(!model.is_empty());
+        assert_eq!(model.worker_set_count(), 1);
+        assert!(model.has_worker_set("ns1"));
+        assert!(!model.has_worker_set("ns2"));
+
+        let removed = model.remove_worker_set("ns1");
+        assert!(removed.is_some());
+        assert!(model.is_empty());
+
+        let removed_again = model.remove_worker_set("ns1");
+        assert!(removed_again.is_none());
+    }
+
+    #[test]
+    fn test_get_worker_set() {
+        let model = Model::new("llama".to_string());
+        let ws = make_worker_set("ns1", "abc");
+        model.add_worker_set("ns1".to_string(), ws).unwrap();
+
+        let retrieved = model.get_worker_set("ns1");
+        assert!(retrieved.is_some());
+        assert_eq!(retrieved.unwrap().namespace(), "ns1");
+
+        assert!(model.get_worker_set("ns2").is_none());
+    }
+
+    #[test]
+    fn test_multiple_worker_sets_same_checksum() {
+        let model = Model::new("llama".to_string());
+        model
+            .add_worker_set("ns1".to_string(), make_worker_set("ns1", "abc"))
+            .unwrap();
+        model
+            .add_worker_set("ns2".to_string(), make_worker_set("ns2", "abc"))
+            .unwrap();
+
+        assert_eq!(model.worker_set_count(), 2);
+        assert!(model.has_worker_set("ns1"));
+        assert!(model.has_worker_set("ns2"));
+
+        model.remove_worker_set("ns1");
+        assert_eq!(model.worker_set_count(), 1);
+        assert!(!model.has_worker_set("ns1"));
+        assert!(model.has_worker_set("ns2"));
+    }
+
+    #[test]
+    fn test_add_worker_set_rejects_checksum_mismatch() {
+        let model = Model::new("llama".to_string());
+        model
+            .add_worker_set("ns1".to_string(), make_worker_set("ns1", "abc"))
+            .unwrap();
+
+        // Different checksum from a different namespace should be rejected
+        let result = model.add_worker_set("ns2".to_string(), make_worker_set("ns2", "def"));
+        assert!(result.is_err());
+        assert_eq!(model.worker_set_count(), 1); // ns2 was not added
+    }
+
+    #[test]
+    fn test_is_valid_checksum() {
+        let model = Model::new("llama".to_string());
+
+        // No canonical set yet
+        assert_eq!(model.is_valid_checksum("abc123"), None);
+
+        model
+            .add_worker_set("ns1".to_string(), make_worker_set("ns1", "abc123"))
+            .unwrap();
+
+        // Matches canonical
+        assert_eq!(model.is_valid_checksum("abc123"), Some(true));
+        // Does not match canonical
+        assert_eq!(model.is_valid_checksum("wrong"), Some(false));
+    }
+
+    #[test]
+    fn test_no_engines_means_prefill() {
+        let model = Model::new("llama".to_string());
+        model
+            .add_worker_set("ns1".to_string(), make_worker_set("ns1", "abc"))
+            .unwrap();
+
+        // WorkerSets with no engines are treated as prefill sets
+        assert!(model.has_prefill());
+        assert!(!model.has_decode_engine());
+        assert!(!model.has_chat_engine());
+        assert!(!model.has_completions_engine());
+        assert!(!model.has_embeddings_engine());
+        assert!(!model.has_tensor_engine());
+        assert!(!model.has_images_engine());
+    }
+
+    #[test]
+    fn test_get_engine_returns_error_without_engines() {
+        let model = Model::new("llama".to_string());
+        model
+            .add_worker_set("ns1".to_string(), make_worker_set("ns1", "abc"))
+            .unwrap();
+
+        assert!(model.get_chat_engine().is_err());
+        assert!(model.get_completions_engine().is_err());
+        assert!(model.get_embeddings_engine().is_err());
+        assert!(model.get_images_engine().is_err());
+        assert!(model.get_tensor_engine().is_err());
+    }
+
+    #[test]
+    fn test_select_worker_set_with_extracts_namespace() {
+        // Test that select_worker_set_with works by going through the public API.
+        // Since we can't create real engines in tests, we verify that selection
+        // returns None/Err when no engines are configured, which exercises the
+        // filtering and selection code paths.
+        let model = Model::new("llama".to_string());
+
+        // Empty model
+        assert!(model.get_chat_engine().is_err());
+
+        // Single set (fast path)
+        model
+            .add_worker_set("ns1".to_string(), make_worker_set("ns1", "abc"))
+            .unwrap();
+        assert!(model.get_chat_engine().is_err()); // No engine → filtered out
+
+        // Multiple sets (weighted path)
+        model
+            .add_worker_set("ns2".to_string(), make_worker_set("ns2", "abc"))
+            .unwrap();
+        assert!(model.get_chat_engine().is_err()); // Still no engines → all filtered out
+    }
+
+    #[test]
+    fn test_total_workers_no_watcher() {
+        // In-process WorkerSets (no watcher) default to worker_count=1
+        let model = Model::new("llama".to_string());
+        assert_eq!(model.total_workers(), 0); // empty model
+
+        model
+            .add_worker_set("ns1".to_string(), make_worker_set("ns1", "abc"))
+            .unwrap();
+        assert_eq!(model.total_workers(), 1);
+
+        model
+            .add_worker_set("ns2".to_string(), make_worker_set("ns2", "abc"))
+            .unwrap();
+        assert_eq!(model.total_workers(), 2);
+    }
+
+    #[test]
+    fn test_total_workers_with_watcher() {
+        let model = Model::new("llama".to_string());
+
+        let (ws1, _tx1) = make_worker_set_with_count("ns1", "abc", vec![1, 2, 3]);
+        let (ws2, _tx2) = make_worker_set_with_count("ns2", "abc", vec![10, 20]);
+        model.add_worker_set("ns1".to_string(), ws1).unwrap();
+        model.add_worker_set("ns2".to_string(), ws2).unwrap();
+
+        assert_eq!(model.total_workers(), 5); // 3 + 2
+    }
+
+    #[test]
+    fn test_total_workers_updates_dynamically() {
+        let model = Model::new("llama".to_string());
+
+        let (ws1, tx1) = make_worker_set_with_count("ns1", "abc", vec![1, 2]);
+        model.add_worker_set("ns1".to_string(), ws1).unwrap();
+        assert_eq!(model.total_workers(), 2);
+
+        // Workers leave
+        tx1.send(vec![1]).unwrap();
+        assert_eq!(model.total_workers(), 1);
+
+        // All workers gone
+        tx1.send(vec![]).unwrap();
+        assert_eq!(model.total_workers(), 0);
+    }
+
+    #[test]
+    fn test_zero_worker_single_set_filtered() {
+        // Single WorkerSet with 0 workers should be filtered by select_worker_set_with.
+        // We test via select_worker_set_with's internal behavior: even though the set
+        // exists and is_prefill_set() returns true, engine accessors should fail because
+        // the zero-worker filter runs before the extract closure.
+        let model = Model::new("llama".to_string());
+
+        let (ws, _tx) = make_worker_set_with_count("ns1", "abc", vec![]);
+        model.add_worker_set("ns1".to_string(), ws).unwrap();
+
+        // WorkerSet exists but has 0 workers → selection filtered out → Err
+        assert!(model.get_chat_engine().is_err());
+        assert!(model.get_completions_engine().is_err());
+    }
+
+    #[test]
+    fn test_zero_worker_multi_set_filtered() {
+        // With multiple sets, only those with workers > 0 participate in selection.
+        let model = Model::new("llama".to_string());
+
+        let (ws1, _tx1) = make_worker_set_with_count("ns1", "abc", vec![]);
+        let (ws2, _tx2) = make_worker_set_with_count("ns2", "abc", vec![]);
+        model.add_worker_set("ns1".to_string(), ws1).unwrap();
+        model.add_worker_set("ns2".to_string(), ws2).unwrap();
+
+        // Both have 0 workers → all filtered → Err
+        assert!(model.get_chat_engine().is_err());
+    }
+}

lib/llm/src/discovery/model_manager.rs

 // SPDX-FileCopyrightText: Copyright (c) 2024-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 // SPDX-License-Identifier: Apache-2.0
 
-use std::{
-    collections::{HashMap, HashSet},
-    sync::Arc,
-};
+use std::{collections::HashSet, sync::Arc};
 
 use dashmap::{DashMap, mapref::entry::Entry};
-use parking_lot::RwLock;
 use tokio::sync::oneshot;
 
 use super::worker_monitor::LoadThresholdConfig;
-use super::{KvWorkerMonitor, RuntimeConfigWatch, runtime_config_watch};
+use super::{KvWorkerMonitor, Model, RuntimeConfigWatch, WorkerSet, runtime_config_watch};
 
 use dynamo_runtime::{
-    component::{Client, Endpoint, build_transport_type},
+    component::{Endpoint, build_transport_type},
     discovery::DiscoverySpec,
     prelude::DistributedRuntimeProvider,
     protocols::EndpointId,
@@ -27,7 +23,6 @@ use crate::{
     },
     local_model::runtime_config::DisaggregatedEndpoint,
     model_card::ModelDeploymentCard,
-    model_type::ModelType,
     types::{
         generic::tensor::TensorStreamingEngine,
         openai::{
@@ -54,31 +49,34 @@ pub enum ModelManagerError {
 
     #[error("Model already exists: {0}")]
     ModelAlreadyExists(String),
+
+    #[error(
+        "Checksum mismatch for model {model}: expected {expected}, got {got}. All WorkerSets of a model must share the same checksum. Drain all old workers before deploying a new version."
+    )]
+    ChecksumMismatch {
+        model: String,
+        expected: String,
+        got: String,
+    },
 }
 
 /// Central manager for model engines, routing, and configuration.
 ///
-/// Manages model lifecycle including engines, KV routers, prefill coordination,
-/// and per-model busy thresholds for load-based request rejection.
+/// Models are stored hierarchically: ModelManager → Model → WorkerSet.
+/// Each WorkerSet owns a complete pipeline built from its specific configuration.
 ///
 /// Note: Don't implement Clone for this, put it in an Arc instead.
 pub struct ModelManager {
-    // We read a lot and write rarely, so these three are RwLock
-    completion_engines: RwLock<ModelEngines<OpenAICompletionsStreamingEngine>>,
-    chat_completion_engines: RwLock<ModelEngines<OpenAIChatCompletionsStreamingEngine>>,
-    embeddings_engines: RwLock<ModelEngines<OpenAIEmbeddingsStreamingEngine>>,
-    images_engines: RwLock<ModelEngines<OpenAIImagesStreamingEngine>>,
-    videos_engines: RwLock<ModelEngines<OpenAIVideosStreamingEngine>>,
-    tensor_engines: RwLock<ModelEngines<TensorStreamingEngine>>,
-    // Prefill models don't have engines - they're only tracked for discovery/lifecycle
-    prefill_engines: RwLock<ModelEngines<()>>,
+    /// Model name → Model (which contains WorkerSets with engines)
+    models: DashMap<String, Arc<Model>>,
 
+    /// Per-instance model cards, keyed by instance path. Used for cleanup on worker removal.
     cards: DashMap<String, ModelDeploymentCard>,
-    kv_choosers: DashMap<EndpointId, Arc<KvRouter>>,
+
+    /// Prefill router activation rendezvous, keyed by "model_name:namespace".
     prefill_router_activators: DashMap<String, PrefillActivationState>,
 
-    // Per-model monitoring: worker_monitors for load-based rejection, runtime_configs for KvScheduler
-    worker_monitors: DashMap<String, KvWorkerMonitor>,
+    /// Per-endpoint runtime config watchers. Keyed by EndpointId (includes namespace).
     runtime_configs: DashMap<EndpointId, RuntimeConfigWatch>,
 }
 
@@ -91,140 +89,324 @@ impl Default for ModelManager {
 impl ModelManager {
     pub fn new() -> Self {
         Self {
-            completion_engines: RwLock::new(ModelEngines::default()),
-            chat_completion_engines: RwLock::new(ModelEngines::default()),
-            embeddings_engines: RwLock::new(ModelEngines::default()),
-            images_engines: RwLock::new(ModelEngines::default()),
-            videos_engines: RwLock::new(ModelEngines::default()),
-            tensor_engines: RwLock::new(ModelEngines::default()),
-            prefill_engines: RwLock::new(ModelEngines::default()),
+            models: DashMap::new(),
             cards: DashMap::new(),
-            kv_choosers: DashMap::new(),
             prefill_router_activators: DashMap::new(),
-            worker_monitors: DashMap::new(),
             runtime_configs: DashMap::new(),
         }
     }
 
-    pub fn is_valid_checksum(
-        &self,
-        model_type: ModelType,
-        model_name: &str,
-        candidate_checksum: &str,
-    ) -> Option<bool> {
-        let mut results = vec![];
-        for unit in model_type.units() {
-            let maybe_valid_checksum = match unit {
-                ModelType::Chat => self.chat_completion_engines.read().checksum(model_name),
-                ModelType::Completions => self.completion_engines.read().checksum(model_name),
-                ModelType::Embedding => self.embeddings_engines.read().checksum(model_name),
-                ModelType::TensorBased => self.tensor_engines.read().checksum(model_name),
-                ModelType::Images => self.images_engines.read().checksum(model_name),
-                ModelType::Videos => self.videos_engines.read().checksum(model_name),
-                ModelType::Prefill => self.prefill_engines.read().checksum(model_name),
-                _ => {
-                    continue;
+    // -- Model access --
+
+    /// Get or create a Model for the given name.
+    pub fn get_or_create_model(&self, model_name: &str) -> Arc<Model> {
+        self.models
+            .entry(model_name.to_string())
+            .or_insert_with(|| Arc::new(Model::new(model_name.to_string())))
+            .clone()
     }
-            };
-            if let Some(is_valid) = maybe_valid_checksum.map(|valid_checksum| {
-                tracing::debug!(
-                    model_name,
-                    valid_checksum,
-                    candidate_checksum,
-                    "is_valid_checksum: check case"
-                );
-                valid_checksum == candidate_checksum
-            }) {
-                results.push(is_valid)
+
+    /// Get an existing Model, if it exists.
+    pub fn get_model(&self, model_name: &str) -> Option<Arc<Model>> {
+        self.models
+            .get(model_name)
+            .map(|entry| entry.value().clone())
     }
+
+    /// Remove a Model if it has no remaining WorkerSets.
+    /// Uses atomic remove_if to avoid TOCTOU race between checking is_empty and removing.
+    pub fn remove_model_if_empty(&self, model_name: &str) {
+        if self
+            .models
+            .remove_if(model_name, |_, model| model.is_empty())
+            .is_some()
+        {
+            tracing::info!(model_name, "Removed empty model from manager");
         }
-        if results.is_empty() {
-            None
-        } else {
-            // The checksum is valid if it is correct for all the ModelType in the bitflag.
-            Some(results.into_iter().all(|x| x))
     }
+
+    /// Add a WorkerSet to a Model. Creates the Model if it doesn't exist.
+    /// Returns `Err` if the WorkerSet's checksum doesn't match the model's canonical checksum.
+    pub fn add_worker_set(
+        &self,
+        model_name: &str,
+        namespace: &str,
+        worker_set: WorkerSet,
+    ) -> Result<(), ModelManagerError> {
+        let model = self.get_or_create_model(model_name);
+        model.add_worker_set(namespace.to_string(), Arc::new(worker_set))
+    }
+
+    /// Remove a WorkerSet from a Model. Removes the Model if it becomes empty.
+    pub fn remove_worker_set(&self, model_name: &str, namespace: &str) -> Option<Arc<WorkerSet>> {
+        let model = self.models.get(model_name)?;
+        let removed = model.remove_worker_set(namespace);
+        drop(model);
+        self.remove_model_if_empty(model_name);
+        removed
     }
 
+    // -- Checksum validation --
+
+    /// Check if a candidate checksum is valid for a model.
+    /// Returns `Some(true)` if it matches the model's canonical checksum, `Some(false)` if it
+    /// doesn't match, or `None` if the model doesn't exist or has no canonical checksum yet.
+    pub fn is_valid_checksum(&self, model_name: &str, candidate_checksum: &str) -> Option<bool> {
+        let model = self.models.get(model_name)?;
+        model.is_valid_checksum(candidate_checksum)
+    }
+
+    // -- Model cards --
+
     pub fn get_model_cards(&self) -> Vec<ModelDeploymentCard> {
         self.cards.iter().map(|r| r.value().clone()).collect()
     }
 
+    /// Save a ModelDeploymentCard from an instance's key so we can fetch it later when the key is
+    /// deleted.
+    pub fn save_model_card(&self, key: &str, card: ModelDeploymentCard) -> anyhow::Result<()> {
+        self.cards.insert(key.to_string(), card);
+        Ok(())
+    }
+
+    /// Remove and return model card for this instance's key. We do this when the instance stops.
+    pub fn remove_model_card(&self, key: &str) -> Option<ModelDeploymentCard> {
+        self.cards.remove(key).map(|(_, v)| v)
+    }
+
+    // -- Engine accessors (delegate through Model → WorkerSet) --
+
     /// Check if a decode model (chat or completions) is registered
     pub fn has_decode_model(&self, model: &str) -> bool {
-        self.chat_completion_engines.read().contains(model)
-            || self.completion_engines.read().contains(model)
+        self.models
+            .get(model)
+            .is_some_and(|m| m.has_decode_engine())
     }
 
     /// Check if a prefill model is registered
     pub fn has_prefill_model(&self, model: &str) -> bool {
-        self.prefill_engines.read().contains(model)
+        self.models.get(model).is_some_and(|m| m.has_prefill())
     }
 
     /// Check if any model (decode or prefill) is registered.
-    /// Note: For registration skip-checks, use has_decode_model() or has_prefill_model() instead.
     pub fn has_model_any(&self, model: &str) -> bool {
         self.has_decode_model(model) || self.has_prefill_model(model)
     }
 
     pub fn model_display_names(&self) -> HashSet<String> {
-        self.list_chat_completions_models()
-            .into_iter()
-            .chain(self.list_completions_models())
-            .chain(self.list_embeddings_models())
-            .chain(self.list_images_models())
-            .chain(self.list_videos_models())
-            .chain(self.list_tensor_models())
-            .chain(self.list_prefill_models())
-            .collect()
+        let mut names = HashSet::new();
+        for entry in self.models.iter() {
+            let model = entry.value();
+            if model.has_chat_engine()
+                || model.has_completions_engine()
+                || model.has_embeddings_engine()
+                || model.has_images_engine()
+                || model.has_tensor_engine()
+                || model.has_videos_engine()
+                || model.has_prefill()
+            {
+                names.insert(entry.key().clone());
+            }
+        }
+        names
     }
 
     pub fn list_chat_completions_models(&self) -> Vec<String> {
-        self.chat_completion_engines.read().list()
+        self.models
+            .iter()
+            .filter(|entry| entry.value().has_chat_engine())
+            .map(|entry| entry.key().clone())
+            .collect()
     }
 
     pub fn list_completions_models(&self) -> Vec<String> {
-        self.completion_engines.read().list()
+        self.models
+            .iter()
+            .filter(|entry| entry.value().has_completions_engine())
+            .map(|entry| entry.key().clone())
+            .collect()
     }
 
     pub fn list_embeddings_models(&self) -> Vec<String> {
-        self.embeddings_engines.read().list()
+        self.models
+            .iter()
+            .filter(|entry| entry.value().has_embeddings_engine())
+            .map(|entry| entry.key().clone())
+            .collect()
     }
 
     pub fn list_tensor_models(&self) -> Vec<String> {
-        self.tensor_engines.read().list()
+        self.models
+            .iter()
+            .filter(|entry| entry.value().has_tensor_engine())
+            .map(|entry| entry.key().clone())
+            .collect()
+    }
+
+    pub fn list_images_models(&self) -> Vec<String> {
+        self.models
+            .iter()
+            .filter(|entry| entry.value().has_images_engine())
+            .map(|entry| entry.key().clone())
+            .collect()
+    }
+
+    pub fn list_videos_models(&self) -> Vec<String> {
+        self.models
+            .iter()
+            .filter(|entry| entry.value().has_videos_engine())
+            .map(|entry| entry.key().clone())
+            .collect()
     }
 
     pub fn list_prefill_models(&self) -> Vec<String> {
-        self.prefill_engines.read().list()
+        self.models
+            .iter()
+            .filter(|entry| entry.value().has_prefill())
+            .map(|entry| entry.key().clone())
+            .collect()
     }
 
-    pub fn list_images_models(&self) -> Vec<String> {
-        self.images_engines.read().list()
+    pub fn get_embeddings_engine(
+        &self,
+        model: &str,
+    ) -> Result<OpenAIEmbeddingsStreamingEngine, ModelManagerError> {
+        self.models
+            .get(model)
+            .ok_or_else(|| ModelManagerError::ModelNotFound(model.to_string()))?
+            .get_embeddings_engine()
     }
 
-    pub fn list_videos_models(&self) -> Vec<String> {
-        self.videos_engines.read().list()
+    pub fn get_completions_engine(
+        &self,
+        model: &str,
+    ) -> Result<OpenAICompletionsStreamingEngine, ModelManagerError> {
+        self.models
+            .get(model)
+            .ok_or_else(|| ModelManagerError::ModelNotFound(model.to_string()))?
+            .get_completions_engine()
     }
 
-    pub fn add_completions_model(
+    pub fn get_chat_completions_engine(
         &self,
         model: &str,
-        card_checksum: &str,
-        engine: OpenAICompletionsStreamingEngine,
-    ) -> Result<(), ModelManagerError> {
-        let mut clients = self.completion_engines.write();
-        clients.add(model, card_checksum, engine)
+    ) -> Result<OpenAIChatCompletionsStreamingEngine, ModelManagerError> {
+        self.models
+            .get(model)
+            .ok_or_else(|| ModelManagerError::ModelNotFound(model.to_string()))?
+            .get_chat_engine()
     }
 
+    pub fn get_tensor_engine(
+        &self,
+        model: &str,
+    ) -> Result<TensorStreamingEngine, ModelManagerError> {
+        self.models
+            .get(model)
+            .ok_or_else(|| ModelManagerError::ModelNotFound(model.to_string()))?
+            .get_tensor_engine()
+    }
+
+    pub fn get_images_engine(
+        &self,
+        model: &str,
+    ) -> Result<OpenAIImagesStreamingEngine, ModelManagerError> {
+        self.models
+            .get(model)
+            .ok_or_else(|| ModelManagerError::ModelNotFound(model.to_string()))?
+            .get_images_engine()
+    }
+
+    pub fn get_videos_engine(
+        &self,
+        model: &str,
+    ) -> Result<OpenAIVideosStreamingEngine, ModelManagerError> {
+        self.models
+            .get(model)
+            .ok_or_else(|| ModelManagerError::ModelNotFound(model.to_string()))?
+            .get_videos_engine()
+    }
+
+    // -- Combined engine + parsing options (atomically from one WorkerSet) --
+
+    pub fn get_chat_completions_engine_with_parsing(
+        &self,
+        model: &str,
+    ) -> Result<
+        (
+            OpenAIChatCompletionsStreamingEngine,
+            crate::protocols::openai::ParsingOptions,
+        ),
+        ModelManagerError,
+    > {
+        self.models
+            .get(model)
+            .ok_or_else(|| ModelManagerError::ModelNotFound(model.to_string()))?
+            .get_chat_engine_with_parsing()
+    }
+
+    pub fn get_completions_engine_with_parsing(
+        &self,
+        model: &str,
+    ) -> Result<
+        (
+            OpenAICompletionsStreamingEngine,
+            crate::protocols::openai::ParsingOptions,
+        ),
+        ModelManagerError,
+    > {
+        self.models
+            .get(model)
+            .ok_or_else(|| ModelManagerError::ModelNotFound(model.to_string()))?
+            .get_completions_engine_with_parsing()
+    }
+
+    // -- Convenience methods for in-process models (http.rs, grpc.rs) --
+    // These create a WorkerSet with a default namespace for local models.
+    // TODO: These methods use ModelDeploymentCard::default() for the WorkerSet, which means
+    // parsing_options() returns defaults (no tool_call_parser/reasoning_parser). Pass the real
+    // MDC from callers so ParsingOptions reflect the model's actual configuration.
+
     pub fn add_chat_completions_model(
         &self,
         model: &str,
         card_checksum: &str,
         engine: OpenAIChatCompletionsStreamingEngine,
     ) -> Result<(), ModelManagerError> {
-        let mut clients = self.chat_completion_engines.write();
-        clients.add(model, card_checksum, engine)
+        let model_entry = self.get_or_create_model(model);
+        if model_entry.has_chat_engine() {
+            return Err(ModelManagerError::ModelAlreadyExists(model.to_string()));
+        }
+        let namespace = format!("__local_chat_{}", model);
+        let mut ws = WorkerSet::new(
+            namespace.clone(),
+            card_checksum.to_string(),
+            ModelDeploymentCard::default(),
+        );
+        ws.chat_engine = Some(engine);
+        model_entry.add_worker_set(namespace, Arc::new(ws))?;
+        Ok(())
+    }
+
+    pub fn add_completions_model(
+        &self,
+        model: &str,
+        card_checksum: &str,
+        engine: OpenAICompletionsStreamingEngine,
+    ) -> Result<(), ModelManagerError> {
+        let model_entry = self.get_or_create_model(model);
+        if model_entry.has_completions_engine() {
+            return Err(ModelManagerError::ModelAlreadyExists(model.to_string()));
+        }
+        let namespace = format!("__local_completions_{}", model);
+        let mut ws = WorkerSet::new(
+            namespace.clone(),
+            card_checksum.to_string(),
+            ModelDeploymentCard::default(),
+        );
+        ws.completions_engine = Some(engine);
+        model_entry.add_worker_set(namespace, Arc::new(ws))?;
+        Ok(())
     }
 
     pub fn add_embeddings_model(
@@ -233,8 +415,19 @@ impl ModelManager {
         card_checksum: &str,
         engine: OpenAIEmbeddingsStreamingEngine,
     ) -> Result<(), ModelManagerError> {
-        let mut clients = self.embeddings_engines.write();
-        clients.add(model, card_checksum, engine)
+        let model_entry = self.get_or_create_model(model);
+        if model_entry.has_embeddings_engine() {
+            return Err(ModelManagerError::ModelAlreadyExists(model.to_string()));
+        }
+        let namespace = format!("__local_embeddings_{}", model);
+        let mut ws = WorkerSet::new(
+            namespace.clone(),
+            card_checksum.to_string(),
+            ModelDeploymentCard::default(),
+        );
+        ws.embeddings_engine = Some(engine);
+        model_entry.add_worker_set(namespace, Arc::new(ws))?;
+        Ok(())
     }
 
     pub fn add_tensor_model(
@@ -243,8 +436,19 @@ impl ModelManager {
         card_checksum: &str,
         engine: TensorStreamingEngine,
     ) -> Result<(), ModelManagerError> {
-        let mut clients = self.tensor_engines.write();
-        clients.add(model, card_checksum, engine)
+        let model_entry = self.get_or_create_model(model);
+        if model_entry.has_tensor_engine() {
+            return Err(ModelManagerError::ModelAlreadyExists(model.to_string()));
+        }
+        let namespace = format!("__local_tensor_{}", model);
+        let mut ws = WorkerSet::new(
+            namespace.clone(),
+            card_checksum.to_string(),
+            ModelDeploymentCard::default(),
+        );
+        ws.tensor_engine = Some(engine);
+        model_entry.add_worker_set(namespace, Arc::new(ws))?;
+        Ok(())
     }
 
     pub fn add_images_model(
@@ -253,8 +457,19 @@ impl ModelManager {
         card_checksum: &str,
         engine: OpenAIImagesStreamingEngine,
     ) -> Result<(), ModelManagerError> {
-        let mut clients = self.images_engines.write();
-        clients.add(model, card_checksum, engine)
+        let model_entry = self.get_or_create_model(model);
+        if model_entry.has_images_engine() {
+            return Err(ModelManagerError::ModelAlreadyExists(model.to_string()));
+        }
+        let namespace = format!("__local_images_{}", model);
+        let mut ws = WorkerSet::new(
+            namespace.clone(),
+            card_checksum.to_string(),
+            ModelDeploymentCard::default(),
+        );
+        ws.images_engine = Some(engine);
+        model_entry.add_worker_set(namespace, Arc::new(ws))?;
+        Ok(())
     }
 
     pub fn add_videos_model(
@@ -263,8 +478,19 @@ impl ModelManager {
         card_checksum: &str,
         engine: OpenAIVideosStreamingEngine,
     ) -> Result<(), ModelManagerError> {
-        let mut clients = self.videos_engines.write();
-        clients.add(model, card_checksum, engine)
+        let model_entry = self.get_or_create_model(model);
+        if model_entry.has_videos_engine() {
+            return Err(ModelManagerError::ModelAlreadyExists(model.to_string()));
+        }
+        let namespace = format!("__local_videos_{}", model);
+        let mut ws = WorkerSet::new(
+            namespace.clone(),
+            card_checksum.to_string(),
+            ModelDeploymentCard::default(),
+        );
+        ws.videos_engine = Some(engine);
+        model_entry.add_worker_set(namespace, Arc::new(ws))?;
+        Ok(())
     }
 
     pub fn add_prefill_model(
@@ -272,122 +498,74 @@ impl ModelManager {
         model: &str,
         card_checksum: &str,
     ) -> Result<(), ModelManagerError> {
-        let mut clients = self.prefill_engines.write();
-        clients.add(model, card_checksum, ())
-    }
-
-    pub fn remove_completions_model(&self, model: &str) -> Result<(), ModelManagerError> {
-        let mut clients = self.completion_engines.write();
-        clients.remove(model)
-    }
-
-    pub fn remove_chat_completions_model(&self, model: &str) -> Result<(), ModelManagerError> {
-        let mut clients = self.chat_completion_engines.write();
-        clients.remove(model)
-    }
-
-    pub fn remove_embeddings_model(&self, model: &str) -> Result<(), ModelManagerError> {
-        let mut clients = self.embeddings_engines.write();
-        clients.remove(model)
-    }
-
-    pub fn remove_tensor_model(&self, model: &str) -> Result<(), ModelManagerError> {
-        let mut clients = self.tensor_engines.write();
-        clients.remove(model)
+        let model_entry = self.get_or_create_model(model);
+        if model_entry.has_prefill() {
+            return Err(ModelManagerError::ModelAlreadyExists(model.to_string()));
         }
-
-    pub fn remove_images_model(&self, model: &str) -> Result<(), ModelManagerError> {
-        let mut clients = self.images_engines.write();
-        clients.remove(model)
+        let namespace = format!("__local_prefill_{}", model);
+        let ws = WorkerSet::new(
+            namespace.clone(),
+            card_checksum.to_string(),
+            ModelDeploymentCard::default(),
+        );
+        model_entry.add_worker_set(namespace, Arc::new(ws))?;
+        Ok(())
     }
 
-    pub fn remove_videos_model(&self, model: &str) -> Result<(), ModelManagerError> {
-        let mut clients = self.videos_engines.write();
-        clients.remove(model)
-    }
+    // -- Model removal --
 
-    pub fn remove_prefill_model(&self, model: &str) -> Result<(), ModelManagerError> {
-        let mut clients = self.prefill_engines.write();
-        clients.remove(model)
+    /// Remove a model entirely (all its WorkerSets).
+    /// Returns the removed Model, or None if not found.
+    pub fn remove_model(&self, model: &str) -> Option<Arc<Model>> {
+        self.models.remove(model).map(|(_, m)| m)
     }
 
-    pub fn get_embeddings_engine(
-        &self,
-        model: &str,
-    ) -> Result<OpenAIEmbeddingsStreamingEngine, ModelManagerError> {
-        self.embeddings_engines
-            .read()
-            .get(model)
-            .cloned()
-            .ok_or(ModelManagerError::ModelNotFound(model.to_string()))
-    }
+    // Per-type remove methods for in-process models (used by Python bindings).
+    // These remove the specific synthetic WorkerSet created by the corresponding add_*_model method.
 
-    pub fn get_completions_engine(
-        &self,
-        model: &str,
-    ) -> Result<OpenAICompletionsStreamingEngine, ModelManagerError> {
-        self.completion_engines
-            .read()
-            .get(model)
-            .cloned()
-            .ok_or(ModelManagerError::ModelNotFound(model.to_string()))
+    pub fn remove_chat_completions_model(&self, model: &str) -> Result<(), ModelManagerError> {
+        let namespace = format!("__local_chat_{}", model);
+        self.remove_worker_set(model, &namespace)
+            .map(|_| ())
+            .ok_or_else(|| ModelManagerError::ModelNotFound(model.to_string()))
     }
 
-    pub fn get_chat_completions_engine(
-        &self,
-        model: &str,
-    ) -> Result<OpenAIChatCompletionsStreamingEngine, ModelManagerError> {
-        self.chat_completion_engines
-            .read()
-            .get(model)
-            .cloned()
-            .ok_or(ModelManagerError::ModelNotFound(model.to_string()))
+    pub fn remove_completions_model(&self, model: &str) -> Result<(), ModelManagerError> {
+        let namespace = format!("__local_completions_{}", model);
+        self.remove_worker_set(model, &namespace)
+            .map(|_| ())
+            .ok_or_else(|| ModelManagerError::ModelNotFound(model.to_string()))
     }
 
-    pub fn get_tensor_engine(
-        &self,
-        model: &str,
-    ) -> Result<TensorStreamingEngine, ModelManagerError> {
-        self.tensor_engines
-            .read()
-            .get(model)
-            .cloned()
-            .ok_or(ModelManagerError::ModelNotFound(model.to_string()))
+    pub fn remove_tensor_model(&self, model: &str) -> Result<(), ModelManagerError> {
+        let namespace = format!("__local_tensor_{}", model);
+        self.remove_worker_set(model, &namespace)
+            .map(|_| ())
+            .ok_or_else(|| ModelManagerError::ModelNotFound(model.to_string()))
     }
 
-    pub fn get_images_engine(
-        &self,
-        model: &str,
-    ) -> Result<OpenAIImagesStreamingEngine, ModelManagerError> {
-        self.images_engines
-            .read()
-            .get(model)
-            .cloned()
-            .ok_or(ModelManagerError::ModelNotFound(model.to_string()))
+    pub fn remove_embeddings_model(&self, model: &str) -> Result<(), ModelManagerError> {
+        let namespace = format!("__local_embeddings_{}", model);
+        self.remove_worker_set(model, &namespace)
+            .map(|_| ())
+            .ok_or_else(|| ModelManagerError::ModelNotFound(model.to_string()))
     }
 
-    pub fn get_videos_engine(
-        &self,
-        model: &str,
-    ) -> Result<OpenAIVideosStreamingEngine, ModelManagerError> {
-        self.videos_engines
-            .read()
-            .get(model)
-            .cloned()
-            .ok_or(ModelManagerError::ModelNotFound(model.to_string()))
+    pub fn remove_images_model(&self, model: &str) -> Result<(), ModelManagerError> {
+        let namespace = format!("__local_images_{}", model);
+        self.remove_worker_set(model, &namespace)
+            .map(|_| ())
+            .ok_or_else(|| ModelManagerError::ModelNotFound(model.to_string()))
     }
 
-    /// Save a ModelDeploymentCard from an instance's key so we can fetch it later when the key is
-    /// deleted.
-    pub fn save_model_card(&self, key: &str, card: ModelDeploymentCard) -> anyhow::Result<()> {
-        self.cards.insert(key.to_string(), card);
-        Ok(())
+    pub fn remove_videos_model(&self, model: &str) -> Result<(), ModelManagerError> {
+        let namespace = format!("__local_videos_{}", model);
+        self.remove_worker_set(model, &namespace)
+            .map(|_| ())
+            .ok_or_else(|| ModelManagerError::ModelNotFound(model.to_string()))
     }
 
-    /// Remove and return model card for this instance's key. We do this when the instance stops.
-    pub fn remove_model_card(&self, key: &str) -> Option<ModelDeploymentCard> {
-        self.cards.remove(key).map(|(_, v)| v)
-    }
+    // -- KV Router creation --
 
     pub async fn kv_chooser_for(
         &self,
@@ -396,25 +574,9 @@ impl ModelManager {
         kv_router_config: Option<KvRouterConfig>,
         worker_type: &'static str,
     ) -> anyhow::Result<Arc<KvRouter>> {
-        let endpoint_id = endpoint.id();
-
-        if let Some(kv_chooser) = self.get_kv_chooser(&endpoint_id) {
-            // Check if the existing router has a different block size
-            if kv_chooser.block_size() != kv_cache_block_size {
-                tracing::warn!(
-                    endpoint = %endpoint_id,
-                    existing_block_size = %kv_chooser.block_size(),
-                    requested_block_size = %kv_cache_block_size,
-                    "KV Router block size mismatch! Endpoint is requesting a different kv_cache_block_size than the existing router. \
-                     This will cause routing to fail silently. Consider using the same block size or restarting the router."
-                );
-            }
-            return Ok(kv_chooser);
-        }
-
         let client = endpoint.client().await?;
 
-        // Register router via discovery mechanism
+        // Register router via discovery mechanism.
         let discovery = endpoint.component().drt().discovery();
         let instance_id = discovery.instance_id();
 
@@ -433,7 +595,7 @@ impl ModelManager {
 
         discovery.register(discovery_spec).await?;
 
-        // Get or create runtime config watcher for this endpoint
+        // Get of create runtime config watcher for this endpoint
         let workers_with_configs = self.get_or_create_runtime_config_watcher(endpoint).await?;
 
         let selector = Box::new(DefaultWorkerSelector::new(kv_router_config));
@@ -447,28 +609,35 @@ impl ModelManager {
             worker_type,
         )
         .await?;
-        let new_kv_chooser = Arc::new(chooser);
-        self.kv_choosers.insert(endpoint_id, new_kv_chooser.clone());
-        Ok(new_kv_chooser)
+        Ok(Arc::new(chooser))
     }
 
-    fn get_kv_chooser(&self, id: &EndpointId) -> Option<Arc<KvRouter>> {
-        self.kv_choosers.get(id).map(|r| r.value().clone())
+    // -- Prefill router coordination --
+    // Keyed by "model_name:namespace" so each namespace's decode WorkerSet gets its own
+    // prefill router activated by same-namespace prefill workers.
+
+    /// Build a key for a (model, namespace) pair. Used for prefill router activators
+    /// and registration guards.
+    pub(crate) fn model_namespace_key(model_name: &str, namespace: &str) -> String {
+        format!("{}:{}", model_name, namespace)
     }
 
-    /// Register a prefill router for a decode model. Returns a receiver that will be
-    /// activated when the corresponding prefill model is discovered.
-    /// Returns None if the decode model was already registered.
+    /// Register a prefill router for a decode WorkerSet. Returns a receiver that will be
+    /// activated when the corresponding prefill model in the same namespace is discovered.
+    /// Returns None if a decode WorkerSet in this namespace was already registered.
     pub fn register_prefill_router(
         &self,
-        model_name: String,
+        model_name: &str,
+        namespace: &str,
     ) -> Option<oneshot::Receiver<Endpoint>> {
-        match self.prefill_router_activators.remove(&model_name) {
+        let key = Self::model_namespace_key(model_name, namespace);
+        match self.prefill_router_activators.remove(&key) {
             Some((_, PrefillActivationState::PrefillReady(rx))) => {
                 // Prefill endpoint already arrived - rx will immediately resolve
                 tracing::debug!(
                     model_name = %model_name,
-                    "Prefill endpoint already available, returning receiver with endpoint"
+                    namespace = %namespace,
+                    "Prefill endpoint already available for namespace, returning receiver"
                 );
                 Some(rx)
             }
@@ -476,7 +645,8 @@ impl ModelManager {
                 // Decode already registered - this shouldn't happen, restore state and return None
                 tracing::error!(
                     model_name = %model_name,
-                    "Decode model already registered for this prefill router"
+                    namespace = %namespace,
+                    "Decode WorkerSet already registered for this prefill router"
                 );
                 self.prefill_router_activators
                     .insert(key, PrefillActivationState::DecodeWaiting(tx));
@@ -485,13 +655,12 @@ impl ModelManager {
             None => {
                 // New registration: create tx/rx pair, store sender and return receiver
                 let (tx, rx) = oneshot::channel();
-                self.prefill_router_activators.insert(
-                    model_name.clone(),
-                    PrefillActivationState::DecodeWaiting(tx),
-                );
+                self.prefill_router_activators
+                    .insert(key, PrefillActivationState::DecodeWaiting(tx));
                 tracing::debug!(
                     model_name = %model_name,
-                    "No prefill endpoint available yet, storing sender for future activation"
+                    namespace = %namespace,
+                    "No prefill endpoint for namespace yet, storing sender for future activation"
                 );
                 Some(rx)
             }
@@ -499,114 +668,106 @@ impl ModelManager {
     }
 
     /// Activate a prefill router by sending the endpoint through the oneshot channel.
-    /// If no decode model has registered yet, stores the endpoint for future retrieval.
+    /// The namespace must match the decode WorkerSet's namespace.
     pub fn activate_prefill_router(
         &self,
         model_name: &str,
+        namespace: &str,
         endpoint: Endpoint,
     ) -> anyhow::Result<()> {
-        match self.prefill_router_activators.remove(model_name) {
+        let key = Self::model_namespace_key(model_name, namespace);
+        match self.prefill_router_activators.remove(&key) {
             Some((_, PrefillActivationState::DecodeWaiting(sender))) => {
-                // Decode model already registered
                 sender.send(endpoint).map_err(|_| {
                     anyhow::anyhow!(
-                        "Failed to send endpoint to prefill router activator for model: {}",
-                        model_name
+                        "Failed to send endpoint to prefill router activator for {}:{}",
+                        model_name,
+                        namespace
                     )
                 })?;
-
                 tracing::info!(
                     model_name = %model_name,
-                    "Activated prefill router for already-registered decode model"
+                    namespace = %namespace,
+                    "Activated prefill router for decode WorkerSet"
                 );
-
                 Ok(())
             }
             Some((_, PrefillActivationState::PrefillReady(_))) => {
-                // Prefill already activated - this shouldn't happen
-                anyhow::bail!("Prefill router for model {} already activated", model_name);
+                anyhow::bail!(
+                    "Prefill router for {}:{} already activated",
+                    model_name,
+                    namespace
+                );
             }
             None => {
-                // Decode model not registered yet - create pair and immediately send endpoint
                 let (tx, rx) = oneshot::channel();
-
                 tx.send(endpoint).map_err(|_| {
-                    anyhow::anyhow!("Failed to send endpoint for prefill model: {}", model_name)
+                    anyhow::anyhow!(
+                        "Failed to send endpoint for prefill model {}:{}",
+                        model_name,
+                        namespace
+                    )
                 })?;
-
-                // Store the receiver for when decode model registers
-                self.prefill_router_activators.insert(
-                    model_name.to_string(),
-                    PrefillActivationState::PrefillReady(rx),
-                );
-
+                self.prefill_router_activators
+                    .insert(key, PrefillActivationState::PrefillReady(rx));
                 tracing::info!(
                     model_name = %model_name,
-                    "Stored prefill endpoint for future decode model registration"
+                    namespace = %namespace,
+                    "Stored prefill endpoint for future decode WorkerSet registration"
                 );
-
                 Ok(())
             }
         }
     }
 
-    pub fn get_model_tool_call_parser(&self, model: &str) -> Option<String> {
-        self.cards
-            .iter()
-            .find(|r| r.value().display_name == model)
-            .and_then(|r| r.value().runtime_config.tool_call_parser.clone())
+    /// Remove the prefill router activator for a (model, namespace) pair.
+    /// Called when a WorkerSet is removed to prevent stale activators.
+    pub fn remove_prefill_activator(&self, model_name: &str, namespace: &str) {
+        let key = Self::model_namespace_key(model_name, namespace);
+        if self.prefill_router_activators.remove(&key).is_some() {
+            tracing::debug!(
+                model_name = %model_name,
+                namespace = %namespace,
+                "Cleaned up prefill router activator for removed WorkerSet"
+            );
         }
-
-    pub fn get_model_reasoning_parser(&self, model: &str) -> Option<String> {
-        self.cards
-            .iter()
-            .find(|r| r.value().display_name == model)
-            .and_then(|r| r.value().runtime_config.reasoning_parser.clone())
     }
 
-    /// Creates parsing options with tool call parser and reasoning parser for the specified model.
-    pub fn get_parsing_options(&self, model: &str) -> crate::protocols::openai::ParsingOptions {
-        let tool_call_parser = self.get_model_tool_call_parser(model);
-        let reasoning_parser = self.get_model_reasoning_parser(model);
-
-        crate::protocols::openai::ParsingOptions::new(tool_call_parser, reasoning_parser)
-    }
+    // -- Worker monitoring --
 
     /// Gets or sets the load threshold config for a model's worker monitor.
-    /// Pass `Some(config)` to update, `None` to get. Returns `None` if no monitor exists.
+    /// Checks across all WorkerSets for the model.
     pub fn load_threshold_config(
         &self,
         model: &str,
         config: Option<&LoadThresholdConfig>,
     ) -> Option<LoadThresholdConfig> {
-        let monitor = self.worker_monitors.get(model)?;
-        if let Some(cfg) = config {
-            monitor.set_load_threshold_config(cfg);
-        }
-        Some(monitor.load_threshold_config())
+        let model_entry = self.models.get(model)?;
+        model_entry.load_threshold_config(config)
     }
 
-    /// Gets an existing worker monitor for a model, if one exists.
-    pub fn get_worker_monitor(&self, model: &str) -> Option<KvWorkerMonitor> {
-        self.worker_monitors.get(model).map(|m| m.clone())
-    }
-
-    /// Gets or creates a worker monitor for a model. Updates thresholds if monitor exists.
-    pub fn get_or_create_worker_monitor(
+    /// Gets an existing worker monitor for a specific namespace of a model.
+    pub fn get_worker_monitor_for_namespace(
         &self,
         model: &str,
-        client: Client,
-        config: LoadThresholdConfig,
-    ) -> KvWorkerMonitor {
-        if let Some(existing) = self.worker_monitors.get(model) {
-            existing.set_load_threshold_config(&config);
-            return existing.clone();
+        namespace: &str,
+    ) -> Option<KvWorkerMonitor> {
+        let model_entry = self.models.get(model)?;
+        model_entry.get_worker_monitor_for_namespace(namespace)
+    }
+
+    /// Lists all models with worker monitors configured.
+    pub fn list_busy_thresholds(&self) -> Vec<(String, LoadThresholdConfig)> {
+        let mut result = Vec::new();
+        for entry in self.models.iter() {
+            if let Some(config) = entry.value().load_threshold_config(None) {
+                result.push((entry.key().clone(), config));
             }
-        let monitor = KvWorkerMonitor::new(client, config);
-        self.worker_monitors
-            .insert(model.to_string(), monitor.clone());
-        monitor
         }
+        result
+    }
+
+    // -- Runtime configs --
 
     /// Get or create a runtime config watcher for an endpoint.
     /// Spawns a background task that joins instance availability and config discovery.
@@ -617,7 +778,6 @@ impl ModelManager {
     ) -> anyhow::Result<RuntimeConfigWatch> {
         let endpoint_id = endpoint.id();
 
-        // Fast path: return existing if present
         if let Some(existing) = self.runtime_configs.get(&endpoint_id) {
             return Ok(existing.clone());
         }
@@ -638,7 +798,6 @@ impl ModelManager {
     }
 
     /// Get disaggregated endpoint for a specific worker.
-    /// Used by PrefillRouter for bootstrap info - works for ANY routing mode.
     pub fn get_disaggregated_endpoint(
         &self,
         endpoint_id: &EndpointId,
@@ -648,79 +807,348 @@ impl ModelManager {
         let configs = rx.borrow();
         configs.get(&worker_id)?.disaggregated_endpoint.clone()
     }
+}
 
-    /// Lists all models with worker monitors configured.
-    pub fn list_busy_thresholds(&self) -> Vec<(String, LoadThresholdConfig)> {
-        self.worker_monitors
-            .iter()
-            .map(|entry| (entry.key().clone(), entry.value().load_threshold_config()))
-            .collect()
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::model_card::ModelDeploymentCard;
+
+    fn make_worker_set(namespace: &str, mdcsum: &str) -> WorkerSet {
+        WorkerSet::new(
+            namespace.to_string(),
+            mdcsum.to_string(),
+            ModelDeploymentCard::default(),
+        )
     }
-}
 
-pub struct ModelEngines<E> {
-    /// Optional default model name
-    default: Option<String>,
-    engines: HashMap<String, E>,
-    /// Key: Model name, value: Checksum of the ModelDeploymentCard. New instances must have the
-    /// same card.
-    checksums: HashMap<String, String>,
-}
+    // -- CRUD delegation tests --
 
-impl<E> Default for ModelEngines<E> {
-    fn default() -> Self {
-        Self {
-            default: None,
-            engines: HashMap::new(),
-            checksums: HashMap::new(),
+    #[test]
+    fn test_add_and_get_worker_set() {
+        let mm = ModelManager::new();
+        let ws = make_worker_set("ns1", "abc");
+        mm.add_worker_set("llama", "ns1", ws).unwrap();
+
+        let model = mm.get_model("llama");
+        assert!(model.is_some());
+        let model = model.unwrap();
+        assert!(model.has_worker_set("ns1"));
+        assert_eq!(model.worker_set_count(), 1);
     }
+
+    #[test]
+    fn test_add_worker_set_creates_model() {
+        let mm = ModelManager::new();
+        assert!(mm.get_model("llama").is_none());
+
+        mm.add_worker_set("llama", "ns1", make_worker_set("ns1", "abc"))
+            .unwrap();
+        assert!(mm.get_model("llama").is_some());
     }
-}
 
-impl<E> ModelEngines<E> {
-    #[allow(dead_code)]
-    fn set_default(&mut self, model: &str) {
-        self.default = Some(model.to_string());
+    #[test]
+    fn test_remove_worker_set_removes_empty_model() {
+        let mm = ModelManager::new();
+        mm.add_worker_set("llama", "ns1", make_worker_set("ns1", "abc"))
+            .unwrap();
+        assert!(mm.get_model("llama").is_some());
+
+        let removed = mm.remove_worker_set("llama", "ns1");
+        assert!(removed.is_some());
+        assert_eq!(removed.unwrap().namespace(), "ns1");
+
+        // Model should be auto-removed since it's now empty
+        assert!(mm.get_model("llama").is_none());
     }
 
-    #[allow(dead_code)]
-    fn clear_default(&mut self) {
-        self.default = None;
+    #[test]
+    fn test_remove_worker_set_keeps_model_with_remaining() {
+        let mm = ModelManager::new();
+        mm.add_worker_set("llama", "ns1", make_worker_set("ns1", "abc"))
+            .unwrap();
+        mm.add_worker_set("llama", "ns2", make_worker_set("ns2", "abc"))
+            .unwrap();
+
+        mm.remove_worker_set("llama", "ns1");
+
+        // Model should still exist with ns2
+        let model = mm.get_model("llama").unwrap();
+        assert!(!model.has_worker_set("ns1"));
+        assert!(model.has_worker_set("ns2"));
+        assert_eq!(model.worker_set_count(), 1);
     }
 
-    fn add(&mut self, model: &str, checksum: &str, engine: E) -> Result<(), ModelManagerError> {
-        if self.engines.contains_key(model) {
-            return Err(ModelManagerError::ModelAlreadyExists(model.to_string()));
+    #[test]
+    fn test_remove_worker_set_nonexistent_model() {
+        let mm = ModelManager::new();
+        assert!(mm.remove_worker_set("llama", "ns1").is_none());
     }
-        self.engines.insert(model.to_string(), engine);
-        self.checksums
-            .insert(model.to_string(), checksum.to_string());
-        Ok(())
+
+    #[test]
+    fn test_remove_worker_set_nonexistent_namespace() {
+        let mm = ModelManager::new();
+        mm.add_worker_set("llama", "ns1", make_worker_set("ns1", "abc"))
+            .unwrap();
+        assert!(mm.remove_worker_set("llama", "ns2").is_none());
+
+        // Model should still exist (ns1 still there)
+        assert!(mm.get_model("llama").is_some());
     }
 
-    fn remove(&mut self, model: &str) -> Result<(), ModelManagerError> {
-        if self.engines.remove(model).is_none() {
-            return Err(ModelManagerError::ModelNotFound(model.to_string()));
+    #[test]
+    fn test_remove_model_if_empty_noop_when_not_empty() {
+        let mm = ModelManager::new();
+        mm.add_worker_set("llama", "ns1", make_worker_set("ns1", "abc"))
+            .unwrap();
+
+        mm.remove_model_if_empty("llama");
+        assert!(mm.get_model("llama").is_some()); // Still has ns1
     }
-        let _ = self.checksums.remove(model);
-        Ok(())
+
+    #[test]
+    fn test_remove_model_if_empty_noop_when_missing() {
+        let mm = ModelManager::new();
+        mm.remove_model_if_empty("nonexistent"); // Should not panic
     }
 
-    fn get(&self, model: &str) -> Option<&E> {
-        self.engines.get(model)
+    #[test]
+    fn test_remove_model() {
+        let mm = ModelManager::new();
+        mm.add_worker_set("llama", "ns1", make_worker_set("ns1", "abc"))
+            .unwrap();
+        mm.add_worker_set("llama", "ns2", make_worker_set("ns2", "abc"))
+            .unwrap();
+
+        let removed = mm.remove_model("llama");
+        assert!(removed.is_some());
+        assert!(mm.get_model("llama").is_none());
     }
 
-    fn contains(&self, model: &str) -> bool {
-        self.engines.contains_key(model)
+    #[test]
+    fn test_get_or_create_model_idempotent() {
+        let mm = ModelManager::new();
+        let m1 = mm.get_or_create_model("llama");
+        let m2 = mm.get_or_create_model("llama");
+        // Both should point to the same Model (same Arc)
+        assert!(Arc::ptr_eq(&m1, &m2));
     }
 
-    pub fn list(&self) -> Vec<String> {
-        self.engines.keys().map(|k| k.to_owned()).collect()
+    // -- Checksum validation tests --
+
+    #[test]
+    fn test_is_valid_checksum_match() {
+        let mm = ModelManager::new();
+        mm.add_worker_set("llama", "ns1", make_worker_set("ns1", "abc123"))
+            .unwrap();
+
+        assert_eq!(mm.is_valid_checksum("llama", "abc123"), Some(true));
+    }
+
+    #[test]
+    fn test_is_valid_checksum_mismatch() {
+        let mm = ModelManager::new();
+        mm.add_worker_set("llama", "ns1", make_worker_set("ns1", "abc123"))
+            .unwrap();
+
+        assert_eq!(mm.is_valid_checksum("llama", "wrong"), Some(false));
     }
 
-    /// Returns a newly allocated String for called convenience. All the places I use
-    /// this I need a String.
-    pub fn checksum(&self, model: &str) -> Option<String> {
-        self.checksums.get(model).map(|s| s.to_string())
+    #[test]
+    fn test_is_valid_checksum_no_canonical_yet() {
+        let mm = ModelManager::new();
+        mm.add_worker_set("llama", "ns1", make_worker_set("ns1", "abc123"))
+            .unwrap();
+
+        // Canonical is set, so even for a "new namespace" scenario the checksum is checked
+        assert_eq!(mm.is_valid_checksum("llama", "abc123"), Some(true));
+        assert_eq!(mm.is_valid_checksum("llama", "xyz"), Some(false));
+    }
+
+    #[test]
+    fn test_is_valid_checksum_missing_model() {
+        let mm = ModelManager::new();
+        assert_eq!(mm.is_valid_checksum("nonexistent", "abc"), None);
+    }
+
+    #[test]
+    fn test_is_valid_checksum_cross_namespace_enforcement() {
+        let mm = ModelManager::new();
+        mm.add_worker_set("llama", "ns1", make_worker_set("ns1", "checksum_a"))
+            .unwrap();
+
+        // A different namespace with a different checksum should be rejected at the model level
+        assert_eq!(mm.is_valid_checksum("llama", "checksum_b"), Some(false));
+
+        // Same checksum is accepted
+        assert_eq!(mm.is_valid_checksum("llama", "checksum_a"), Some(true));
+    }
+
+    // -- Model listing and filtering tests --
+
+    #[test]
+    fn test_has_decode_model() {
+        let mm = ModelManager::new();
+
+        // No model → false
+        assert!(!mm.has_decode_model("llama"));
+
+        // Prefill-only set (no engines) → false
+        mm.add_worker_set("llama", "ns1", make_worker_set("ns1", "abc"))
+            .unwrap();
+        assert!(!mm.has_decode_model("llama"));
+    }
+
+    #[test]
+    fn test_has_prefill_model() {
+        let mm = ModelManager::new();
+
+        // Prefill set = no engines
+        mm.add_worker_set("llama", "ns1", make_worker_set("ns1", "abc"))
+            .unwrap();
+        assert!(mm.has_prefill_model("llama"));
+    }
+
+    #[test]
+    fn test_has_model_any() {
+        let mm = ModelManager::new();
+        assert!(!mm.has_model_any("llama"));
+
+        mm.add_worker_set("llama", "ns1", make_worker_set("ns1", "abc"))
+            .unwrap();
+        assert!(mm.has_model_any("llama")); // has prefill
+    }
+
+    #[test]
+    fn test_model_display_names_includes_prefill() {
+        let mm = ModelManager::new();
+        mm.add_worker_set("llama", "ns1", make_worker_set("ns1", "abc"))
+            .unwrap();
+
+        let names = mm.model_display_names();
+        assert!(names.contains("llama"));
+    }
+
+    #[test]
+    fn test_model_display_names_empty() {
+        let mm = ModelManager::new();
+        assert!(mm.model_display_names().is_empty());
+    }
+
+    #[test]
+    fn test_list_prefill_models() {
+        let mm = ModelManager::new();
+        mm.add_worker_set("llama", "ns1", make_worker_set("ns1", "abc"))
+            .unwrap();
+        mm.add_worker_set("gpt", "ns1", make_worker_set("ns1", "def"))
+            .unwrap();
+
+        let prefill = mm.list_prefill_models();
+        assert_eq!(prefill.len(), 2);
+        assert!(prefill.contains(&"llama".to_string()));
+        assert!(prefill.contains(&"gpt".to_string()));
+    }
+
+    // -- Model card tests --
+
+    #[test]
+    fn test_save_and_remove_model_card() {
+        let mm = ModelManager::new();
+        let card = ModelDeploymentCard::default();
+        mm.save_model_card("instance/key/1", card.clone()).unwrap();
+
+        let cards = mm.get_model_cards();
+        assert_eq!(cards.len(), 1);
+
+        let removed = mm.remove_model_card("instance/key/1");
+        assert!(removed.is_some());
+        assert!(mm.get_model_cards().is_empty());
+    }
+
+    #[test]
+    fn test_remove_model_card_nonexistent() {
+        let mm = ModelManager::new();
+        assert!(mm.remove_model_card("nonexistent").is_none());
+    }
+
+    // -- Prefill router rendezvous tests --
+    // Note: activate_prefill_router requires an Endpoint (needs DistributedRuntime),
+    // so we test the registration state machine and cleanup only.
+
+    #[test]
+    fn test_prefill_router_register_new() {
+        let mm = ModelManager::new();
+
+        // First registration for a (model, namespace) returns Some(rx)
+        let rx = mm.register_prefill_router("llama", "ns1");
+        assert!(rx.is_some());
+    }
+
+    #[test]
+    fn test_prefill_router_double_register_returns_none() {
+        let mm = ModelManager::new();
+
+        let rx1 = mm.register_prefill_router("llama", "ns1");
+        assert!(rx1.is_some());
+
+        // Second registration for the same (model, namespace) returns None
+        let rx2 = mm.register_prefill_router("llama", "ns1");
+        assert!(rx2.is_none());
+    }
+
+    #[test]
+    fn test_prefill_router_different_namespaces_independent() {
+        let mm = ModelManager::new();
+
+        // Different namespaces should be independent
+        let rx1 = mm.register_prefill_router("llama", "ns1");
+        let rx2 = mm.register_prefill_router("llama", "ns2");
+        assert!(rx1.is_some());
+        assert!(rx2.is_some());
+    }
+
+    #[test]
+    fn test_prefill_router_different_models_independent() {
+        let mm = ModelManager::new();
+
+        // Different models should be independent
+        let rx1 = mm.register_prefill_router("llama", "ns1");
+        let rx2 = mm.register_prefill_router("gpt", "ns1");
+        assert!(rx1.is_some());
+        assert!(rx2.is_some());
+    }
+
+    #[test]
+    fn test_prefill_router_remove_allows_reregister() {
+        let mm = ModelManager::new();
+
+        let rx = mm.register_prefill_router("llama", "ns1");
+        assert!(rx.is_some());
+
+        // Remove the activator
+        mm.remove_prefill_activator("llama", "ns1");
+
+        // Should be able to register again
+        let rx2 = mm.register_prefill_router("llama", "ns1");
+        assert!(rx2.is_some());
+    }
+
+    #[test]
+    fn test_prefill_router_remove_nonexistent_noop() {
+        let mm = ModelManager::new();
+        // Should not panic
+        mm.remove_prefill_activator("llama", "ns1");
+    }
+
+    #[test]
+    fn test_model_namespace_key_format() {
+        assert_eq!(
+            ModelManager::model_namespace_key("llama", "ns1"),
+            "llama:ns1"
+        );
+        assert_eq!(
+            ModelManager::model_namespace_key("gpt-4", "default-abc"),
+            "gpt-4:default-abc"
+        );
     }
 }

lib/llm/src/discovery/watcher.rs

@@ -24,7 +24,7 @@ use dynamo_runtime::{
 
 use crate::{
     backend::Backend,
-    discovery::WORKER_TYPE_DECODE,
+    discovery::{KvWorkerMonitor, WORKER_TYPE_DECODE, WorkerSet},
     entrypoint::{self, ChatEngineFactoryCallback, RouterConfig},
     http::service::metrics::Metrics,
     kv_router::PrefillRouter,
@@ -47,7 +47,17 @@ use crate::{
 };
 
 use super::ModelManager;
-use crate::namespace::is_global_namespace;
+use crate::namespace::NamespaceFilter;
+
+/// Constructs the WorkerSet storage key. Prefill and decode workers in the same
+/// namespace get different keys so they don't block each other's registration.
+fn worker_set_key(namespace: &str, model_type: ModelType) -> String {
+    if model_type.supports_prefill() {
+        format!("{}:prefill", namespace)
+    } else {
+        namespace.to_string()
+    }
+}
 
 #[derive(Debug, Clone)]
 pub enum ModelUpdate {
@@ -64,7 +74,8 @@ pub struct ModelWatcher {
     model_update_tx: Option<Sender<ModelUpdate>>,
     chat_engine_factory: Option<ChatEngineFactoryCallback>,
     metrics: Arc<Metrics>,
-    registering_models: DashSet<String>,
+    /// Guards against concurrent pipeline construction for the same (model, namespace).
+    registering_worker_sets: DashSet<String>,
 }
 
 const ALL_MODEL_TYPES: &[ModelType] = &[
@@ -78,6 +89,27 @@ const ALL_MODEL_TYPES: &[ModelType] = &[
     ModelType::Prefill,
 ];
 
+/// Returns true if no models in the manager support the given model type.
+fn is_model_type_list_empty(manager: &ModelManager, model_type: ModelType) -> bool {
+    if model_type == ModelType::Chat {
+        manager.list_chat_completions_models().is_empty()
+    } else if model_type == ModelType::Completions {
+        manager.list_completions_models().is_empty()
+    } else if model_type == ModelType::Embedding {
+        manager.list_embeddings_models().is_empty()
+    } else if model_type == ModelType::Images {
+        manager.list_images_models().is_empty()
+    } else if model_type == ModelType::Videos {
+        manager.list_videos_models().is_empty()
+    } else if model_type == ModelType::TensorBased {
+        manager.list_tensor_models().is_empty()
+    } else if model_type == ModelType::Prefill {
+        manager.list_prefill_models().is_empty()
+    } else {
+        true
+    }
+}
+
 impl ModelWatcher {
     pub fn new(
         runtime: DistributedRuntime,
@@ -96,7 +128,7 @@ impl ModelWatcher {
             model_update_tx: None,
             chat_engine_factory,
             metrics,
-            registering_models: DashSet::new(),
+            registering_worker_sets: DashSet::new(),
         }
     }
 
@@ -119,10 +151,8 @@ impl ModelWatcher {
     pub async fn watch(
         &self,
         mut discovery_stream: DiscoveryStream,
-        target_namespace: Option<&str>,
+        namespace_filter: NamespaceFilter,
     ) {
-        let global_namespace = target_namespace.is_none_or(is_global_namespace);
-
         while let Some(result) = discovery_stream.next().await {
             let event = match result {
                 Ok(event) => event,
@@ -168,28 +198,27 @@ impl ModelWatcher {
                         }
                     };
 
-                    // Filter by namespace if target_namespace is specified
-                    if !global_namespace
-                        && let Some(target_ns) = target_namespace
-                        && mcid.namespace != target_ns
-                    {
+                    // Filter by namespace using the configured filter
+                    if !namespace_filter.matches(&mcid.namespace) {
                         tracing::debug!(
                             model_namespace = mcid.namespace,
-                            target_namespace = target_ns,
-                            "Skipping model from different namespace"
+                            namespace_filter = ?namespace_filter,
+                            "Skipping model due to namespace filter"
                         );
                         continue;
                     }
 
-                    // If we already have a worker for this model, and the ModelDeploymentCard
-                    // cards don't match, alert, and don't add the new instance
-                    let can_add =
-                        self.manager
-                            .is_valid_checksum(card.model_type, card.name(), card.mdcsum());
+                    // If we already have a WorkerSet for this model and the checksums
+                    // don't match, reject the new worker. All WorkerSets of a model
+                    // must share the same checksum.
+                    let can_add = self.manager.is_valid_checksum(card.name(), card.mdcsum());
                     if can_add.is_some_and(|is_valid| !is_valid) {
                         tracing::error!(
                             model_name = card.name(),
-                            "Checksum for new model does not match existing model."
+                            namespace = mcid.namespace,
+                            "Checksum for new worker does not match model's canonical checksum. \
+                             All WorkerSets must share the same checksum. \
+                             Drain all old workers before deploying a new version."
                         );
 
                         // TODO: mark that instance down in clients
@@ -199,7 +228,6 @@ impl ModelWatcher {
                         // needs more testing).
                         // The `PushRouter` is in `ModelMananger` (`self.manager` here), but inside
                         // interface `AsyncEngine` which only has a `generate` method.
-
                         continue;
                     }
 
@@ -235,7 +263,7 @@ impl ModelWatcher {
                     };
 
                     match self
-                        .handle_delete(model_card_instance_id, target_namespace, global_namespace)
+                        .handle_delete(model_card_instance_id, &namespace_filter)
                         .await
                     {
                         Ok(Some(model_name)) => {
@@ -253,13 +281,12 @@ impl ModelWatcher {
         }
     }
 
-    /// If the last instance running this model has gone delete it.
-    /// Returns the name of the model we just deleted, if any.
+    /// Handle a worker removal. Cleans up per-namespace WorkerSets and the Model itself
+    /// when no instances remain. Returns the model name if the entire Model was removed.
     async fn handle_delete(
         &self,
         mcid: &ModelCardInstanceId,
-        target_namespace: Option<&str>,
-        is_global_namespace: bool,
+        namespace_filter: &NamespaceFilter,
     ) -> anyhow::Result<Option<String>> {
         let key = mcid.to_path();
         let card = match self.manager.remove_model_card(&key) {
@@ -269,89 +296,55 @@ impl ModelWatcher {
             }
         };
         let model_name = card.name().to_string();
+        let worker_namespace = &mcid.namespace;
+        let worker_component = &mcid.component;
+        let ws_key = worker_set_key(&mcid.namespace, card.model_type);
+
+        // Query discovery for all remaining instances of this model
         let active_instances = self
-            .cards_for_model(&model_name, target_namespace, is_global_namespace)
+            .cards_for_model_with_endpoints(&model_name, namespace_filter)
             .await
             .with_context(|| model_name.clone())?;
+
+        // Check if instances of the SAME component remain in this namespace.
+        // In disaggregated deployments, prefill and decode are different components
+        // in the same namespace, so we must check at the component level to avoid
+        // removing one type's WorkerSet while the other still has workers.
+        let component_has_instances = active_instances.iter().any(|(eid, _)| {
+            eid.namespace == *worker_namespace && eid.component == *worker_component
+        });
+
+        if !component_has_instances {
+            // No more workers of this component in this namespace — remove its WorkerSet
+            if let Some(_removed_ws) = self.manager.remove_worker_set(&model_name, &ws_key) {
+                // remove_prefill_activator uses deployment namespace (not ws_key)
+                self.manager
+                    .remove_prefill_activator(&model_name, worker_namespace);
+                tracing::info!(
+                    model_name,
+                    namespace = %worker_namespace,
+                    "Removed WorkerSet (no remaining instances in namespace)"
+                );
+            }
+        }
+
+        // Check if the Model still has instances in any namespace
         if !active_instances.is_empty() {
             tracing::debug!(
                 model_name,
-                target_namespace = ?target_namespace,
                 active_instance_count = active_instances.len(),
-                "Model has other active instances, not removing"
+                "Model has other active instances in other namespaces"
             );
             return Ok(None);
         }
 
-        // Ignore the errors because model could be either type
-        let chat_model_remove_err = self.manager.remove_chat_completions_model(&model_name);
-        let completions_model_remove_err = self.manager.remove_completions_model(&model_name);
-        let embeddings_model_remove_err = self.manager.remove_embeddings_model(&model_name);
-        let images_model_remove_err = self.manager.remove_images_model(&model_name);
-        let videos_model_remove_err = self.manager.remove_videos_model(&model_name);
-        let tensor_model_remove_err = self.manager.remove_tensor_model(&model_name);
-        let prefill_model_remove_err = self.manager.remove_prefill_model(&model_name);
-
-        let mut chat_model_removed = false;
-        let mut completions_model_removed = false;
-        let mut embeddings_model_removed = false;
-        let mut images_model_removed = false;
-        let mut videos_model_removed = false;
-        let mut tensor_model_removed = false;
-        let mut prefill_model_removed = false;
-
-        if chat_model_remove_err.is_ok() && self.manager.list_chat_completions_models().is_empty() {
-            chat_model_removed = true;
-        }
-        if completions_model_remove_err.is_ok() && self.manager.list_completions_models().is_empty()
-        {
-            completions_model_removed = true;
-        }
-        if embeddings_model_remove_err.is_ok() && self.manager.list_embeddings_models().is_empty() {
-            embeddings_model_removed = true;
-        }
-        if images_model_remove_err.is_ok() && self.manager.list_images_models().is_empty() {
-            images_model_removed = true;
-        }
-        if videos_model_remove_err.is_ok() && self.manager.list_videos_models().is_empty() {
-            videos_model_removed = true;
-        }
-        if tensor_model_remove_err.is_ok() && self.manager.list_tensor_models().is_empty() {
-            tensor_model_removed = true;
-        }
-        if prefill_model_remove_err.is_ok() && self.manager.list_prefill_models().is_empty() {
-            prefill_model_removed = true;
-        }
+        // No instances remain anywhere — remove the entire Model
+        let _ = self.manager.remove_model(&model_name);
 
-        if !chat_model_removed
-            && !completions_model_removed
-            && !embeddings_model_removed
-            && !images_model_removed
-            && !videos_model_removed
-            && !tensor_model_removed
-            && !prefill_model_removed
-        {
-            tracing::debug!(
-                "No updates to send for model {}: chat_model_removed: {}, completions_model_removed: {}, embeddings_model_removed: {}, images_model_removed: {}, videos_model_removed: {}, tensor_model_removed: {}, prefill_model_removed: {}",
-                model_name,
-                chat_model_removed,
-                completions_model_removed,
-                embeddings_model_removed,
-                images_model_removed,
-                videos_model_removed,
-                tensor_model_removed,
-                prefill_model_removed
-            );
-        } else {
+        if let Some(tx) = &self.model_update_tx {
             for model_type in ALL_MODEL_TYPES {
-                if ((chat_model_removed && *model_type == ModelType::Chat)
-                    || (completions_model_removed && *model_type == ModelType::Completions)
-                    || (embeddings_model_removed && *model_type == ModelType::Embedding)
-                    || (images_model_removed && *model_type == ModelType::Images)
-                    || (videos_model_removed && *model_type == ModelType::Videos)
-                    || (tensor_model_removed && *model_type == ModelType::TensorBased)
-                    || (prefill_model_removed && *model_type == ModelType::Prefill))
-                    && let Some(tx) = &self.model_update_tx
+                if card.model_type.intersects(*model_type)
+                    && is_model_type_list_empty(&self.manager, *model_type)
                 {
                     tx.send(ModelUpdate::Removed(card.clone())).await.ok();
                 }
@@ -368,54 +361,52 @@ impl ModelWatcher {
         mcid: &ModelCardInstanceId,
         card: &mut ModelDeploymentCard,
     ) -> anyhow::Result<()> {
-        // Check if model is already registered before downloading config.
-        // This prevents duplicate HuggingFace API calls when multiple workers register
-        // the same model.
-        // Prefill and decode models are tracked separately, so registering one
-        // doesn't block the other (they can arrive in any order).
-        let already_registered = if card.model_type.supports_prefill() {
-            self.manager.has_prefill_model(card.name())
-        } else {
-            self.manager.has_decode_model(card.name())
-        };
+        // Check if this specific (model, namespace, type) WorkerSet already exists.
+        // If so, this is just another worker joining an existing set — no pipeline build needed.
+        let model_name = card.name().to_string();
+        let namespace = mcid.namespace.clone();
+        let ws_key = worker_set_key(&namespace, card.model_type);
 
-        if already_registered {
+        if let Some(model) = self.manager.get_model(&model_name)
+            && model.has_worker_set(&ws_key)
+        {
             self.manager
                 .save_model_card(&mcid.to_path(), card.clone())?;
             tracing::debug!(
                 model_name = card.name(),
-                namespace = mcid.namespace,
-                model_type = %card.model_type,
-                "Model already registered, skipping config download"
+                namespace = namespace,
+                "Worker joined existing WorkerSet, skipping pipeline build"
             );
             return Ok(());
         }
 
-        // Use registering_models set to prevent concurrent registrations.
-        let model_key = card.name().to_string();
-        if !self.registering_models.insert(model_key.clone()) {
+        // Guard against concurrent pipeline construction for the same (model, namespace, type)
+        let registration_key = ModelManager::model_namespace_key(&model_name, &ws_key);
+        if !self
+            .registering_worker_sets
+            .insert(registration_key.clone())
+        {
             self.manager
                 .save_model_card(&mcid.to_path(), card.clone())?;
             tracing::debug!(
                 model_name = card.name(),
-                namespace = mcid.namespace,
-                "Model registration in progress by another worker, skipping"
+                namespace = namespace,
+                "WorkerSet registration in progress, skipping"
             );
             return Ok(());
         }
 
-        // We acquired the registration lock. Use a helper to ensure cleanup on all exit paths.
-        let result = self.do_model_registration(mcid, card).await;
+        let result = self.do_worker_set_registration(mcid, card).await;
 
-        // Always remove from registering set, whether success or failure
-        self.registering_models.remove(&model_key);
+        // Always remove from registering set
+        self.registering_worker_sets.remove(&registration_key);
 
         result
     }
 
-    /// Inner function that performs the actual model registration.
-    /// Called by handle_put after acquiring the registration lock.
-    async fn do_model_registration(
+    /// Build a complete WorkerSet with all engines for this (model, namespace)
+    /// and add it to the Model.
+    async fn do_worker_set_registration(
         &self,
         mcid: &ModelCardInstanceId,
         card: &mut ModelDeploymentCard,
@@ -428,7 +419,12 @@ impl ModelWatcher {
             .component(&mcid.component)?;
         let endpoint = component.endpoint(&mcid.endpoint);
         let client = endpoint.client().await?;
-        tracing::debug!(model_name = card.name(), "adding model");
+        let instance_watcher = client.instance_avail_watcher();
+        tracing::debug!(
+            model_name = card.name(),
+            namespace = mcid.namespace,
+            "building worker set pipeline"
+        );
         self.manager
             .save_model_card(&mcid.to_path(), card.clone())?;
 
@@ -437,6 +433,12 @@ impl ModelWatcher {
         }
 
         let checksum = card.mdcsum();
+        let namespace = mcid.namespace.clone();
+        let ws_key = worker_set_key(&namespace, card.model_type);
+
+        // Build the WorkerSet with all applicable engines
+        let mut worker_set = WorkerSet::new(namespace.clone(), checksum.to_string(), card.clone());
+        worker_set.set_instance_watcher(instance_watcher);
 
         if card.model_input == ModelInput::Tokens
             && (card.model_type.supports_chat() || card.model_type.supports_completions())
@@ -477,7 +479,7 @@ impl ModelWatcher {
             let model_name = card.name().to_string();
             let prefill_chooser = self
                 .manager
-                .register_prefill_router(model_name.clone())
+                .register_prefill_router(&model_name, &namespace)
                 .map(|rx| {
                     // Create prefill-specific config with track_active_blocks disabled
                     let mut prefill_config = self.router_config.kv_router_config;
@@ -490,20 +492,24 @@ impl ModelWatcher {
                         card.kv_cache_block_size,
                         Some(prefill_config),
                         self.router_config.enforce_disagg,
-                        model_name.clone(), // Pass model name for worker monitor lookup
+                        model_name.clone(),
+                        namespace.clone(),
                     )
                 });
 
-            // Get or create the worker monitor for this model.
-            // Always create the monitor for Prometheus metrics (active_decode_blocks, active_prefill_tokens,
+            // Create a new worker monitor for this WorkerSet. Each WorkerSet gets its own
+            // monitor (1-to-1) since each monitor is scoped to this WorkerSet's Client/namespace.
+            // The monitor tracks Prometheus metrics (active_decode_blocks, active_prefill_tokens,
             // worker TTFT/ITL cleanup). The thresholds control busy detection behavior only.
-            // LoadThresholdConfig allows dynamic threshold updates via the ModelManager.
-            let worker_monitor = Some(self.manager.get_or_create_worker_monitor(
-                card.name(),
+            let worker_monitor = Some(KvWorkerMonitor::new(
                 client.clone(),
                 self.router_config.load_threshold_config.clone(),
             ));
 
+            // Store KV router and worker monitor on the WorkerSet
+            worker_set.kv_router = kv_chooser.clone();
+            worker_set.worker_monitor = worker_monitor.clone();
+
             // Add chat engine only if the model supports chat
             if card.model_type.supports_chat() {
                 let factory_engine = if let Some(ref factory) = self.chat_engine_factory {
@@ -537,9 +543,7 @@ impl ModelWatcher {
                     .await
                     .context("build_routed_pipeline")?
                 };
-                self.manager
-                    .add_chat_completions_model(card.name(), checksum, chat_engine)
-                    .context("add_chat_completions_model")?;
+                worker_set.chat_engine = Some(chat_engine);
                 tracing::info!("Chat completions is ready");
             }
 
@@ -572,9 +576,7 @@ impl ModelWatcher {
                 )
                 .await
                 .context("build_routed_pipeline_with_preprocessor")?;
-                self.manager
-                    .add_completions_model(card.name(), checksum, completions_engine)
-                    .context("add_completions_model")?;
+                worker_set.completions_engine = Some(completions_engine);
                 tracing::info!("Completions is ready");
             }
         } else if card.model_input == ModelInput::Text && card.model_type.supports_embedding() {
@@ -586,9 +588,7 @@ impl ModelWatcher {
                 client, self.router_config.router_mode, None, None
             )
             .await?;
-            let engine = Arc::new(push_router);
-            self.manager
-                .add_embeddings_model(card.name(), checksum, engine)?;
+            worker_set.embeddings_engine = Some(Arc::new(push_router));
         }
         // Case: Text + (Images, Audio, Videos)
         // Must come before the plain Text+Chat / Text+Completions branches because
@@ -599,8 +599,7 @@ impl ModelWatcher {
                 || card.model_type.supports_audios()
                 || card.model_type.supports_videos())
         {
-            // Image Models can support chat completions (vllm omni way)
-            // So register chat_completions model as well
+            // Image/Audio/Video models can also support chat completions (vLLM omni way)
             if card.model_type.supports_chat() {
                 let chat_router = PushRouter::<
                     NvCreateChatCompletionRequest,
@@ -612,14 +611,9 @@ impl ModelWatcher {
                     None,
                 )
                 .await?;
-                self.manager.add_chat_completions_model(
-                    card.name(),
-                    checksum,
-                    Arc::new(chat_router),
-                )?;
+                worker_set.chat_engine = Some(Arc::new(chat_router));
             }
 
-            // This is ModelType::Images : registers /v1/images/* endpoints
             if card.model_type.supports_images() {
                 let images_router = PushRouter::<
                     NvCreateImageRequest,
@@ -628,11 +622,9 @@ impl ModelWatcher {
                     client.clone(), self.router_config.router_mode, None, None
                 )
                 .await?;
-                self.manager
-                    .add_images_model(card.name(), checksum, Arc::new(images_router))?;
+                worker_set.images_engine = Some(Arc::new(images_router));
             }
 
-            // This is ModelType::Videos : registers /v1/videos/* endpoints
             if card.model_type.supports_videos() {
                 let videos_router = PushRouter::<
                     NvCreateVideoRequest,
@@ -641,8 +633,7 @@ impl ModelWatcher {
                     client.clone(), self.router_config.router_mode, None, None
                 )
                 .await?;
-                self.manager
-                    .add_videos_model(card.name(), checksum, Arc::new(videos_router))?;
+                worker_set.videos_engine = Some(Arc::new(videos_router));
             }
 
             // TODO: add audio models support
@@ -655,9 +646,7 @@ impl ModelWatcher {
                 client, self.router_config.router_mode, None, None
             )
             .await?;
-            let engine = Arc::new(push_router);
-            self.manager
-                .add_chat_completions_model(card.name(), checksum, engine)?;
+            worker_set.chat_engine = Some(Arc::new(push_router));
         } else if card.model_input == ModelInput::Text && card.model_type.supports_completions() {
             // Case: Text + Completions
             let push_router = PushRouter::<
@@ -667,12 +656,9 @@ impl ModelWatcher {
                 client, self.router_config.router_mode, None, None
             )
             .await?;
-            let engine = Arc::new(push_router);
-            self.manager
-                .add_completions_model(card.name(), checksum, engine)?;
+            worker_set.completions_engine = Some(Arc::new(push_router));
         } else if card.model_input == ModelInput::Tokens && card.model_type.supports_embedding() {
             // Case 4: Tokens + Embeddings
-
             // Create preprocessing pipeline similar to Backend
             let frontend = SegmentSource::<
                 SingleIn<NvCreateEmbeddingRequest>,
@@ -702,8 +688,7 @@ impl ModelWatcher {
                 .link(preprocessor.backward_edge())?
                 .link(frontend)?;
 
-            self.manager
-                .add_embeddings_model(card.name(), checksum, embedding_engine)?;
+            worker_set.embeddings_engine = Some(embedding_engine);
         } else if card.model_input == ModelInput::Tensor && card.model_type.supports_tensor() {
             // Case 6: Tensor + TensorBased (non-LLM)
             // No KV cache concepts - not an LLM model
@@ -714,9 +699,7 @@ impl ModelWatcher {
                 client, self.router_config.router_mode, None, None
             )
             .await?;
-            let engine = Arc::new(push_router);
-            self.manager
-                .add_tensor_model(card.name(), checksum, engine)?;
+            worker_set.tensor_engine = Some(Arc::new(push_router));
         } else if card.model_type.supports_prefill() {
             // Case 6: Prefill
             // Guardrail: Verify model_input is Tokens
@@ -732,13 +715,18 @@ impl ModelWatcher {
                 "Prefill model detected, registering and activating prefill router"
             );
 
-            // Register prefill model for tracking (no engine needed, just lifecycle)
+            // Prefill sets have no engines — we add the WorkerSet first for tracking,
+            // then activate the prefill router.
             self.manager
-                .add_prefill_model(card.name(), checksum)
-                .context("add_prefill_model")?;
+                .add_worker_set(card.name(), &ws_key, worker_set)?;
 
-            // Activate the prefill router with the endpoint for this prefill model
-            let Ok(()) = self.manager.activate_prefill_router(card.name(), endpoint) else {
+            // Note: activate_prefill_router is keyed by deployment namespace (not ws_key)
+            // because it coordinates between decode and prefill WorkerSets that share
+            // the same deployment namespace but have different ws_keys ("ns" vs "ns:prefill").
+            let Ok(()) = self
+                .manager
+                .activate_prefill_router(card.name(), &namespace, endpoint)
+            else {
                 tracing::warn!(
                     model_name = card.name(),
                     "Failed to activate prefill router - prefill model may already be activated"
@@ -750,6 +738,8 @@ impl ModelWatcher {
                 model_name = card.name(),
                 "Prefill model registered and router activated successfully"
             );
+
+            return Ok(());
         } else {
             // Reject unsupported combinations
             anyhow::bail!(
@@ -760,6 +750,10 @@ impl ModelWatcher {
             );
         }
 
+        // Add the completed WorkerSet to the Model
+        self.manager
+            .add_worker_set(card.name(), &ws_key, worker_set)?;
+
         Ok(())
     }
 
@@ -772,7 +766,6 @@ impl ModelWatcher {
         for instance in instances {
             match instance.deserialize_model::<ModelDeploymentCard>() {
                 Ok(card) => {
-                    // Extract EndpointId from the instance
                     let endpoint_id = match &instance {
                         dynamo_runtime::discovery::DiscoveryInstance::Model {
                             namespace,
@@ -805,19 +798,101 @@ impl ModelWatcher {
     pub async fn cards_for_model(
         &self,
         model_name: &str,
-        target_namespace: Option<&str>,
-        is_global_namespace: bool,
+        namespace_filter: &NamespaceFilter,
     ) -> anyhow::Result<Vec<ModelDeploymentCard>> {
+        Ok(self
+            .cards_for_model_with_endpoints(model_name, namespace_filter)
+            .await?
+            .into_iter()
+            .map(|(_, card)| card)
+            .collect())
+    }
+
+    /// Like `cards_for_model` but also returns the EndpointId for each card,
+    /// allowing callers to filter by namespace.
+    async fn cards_for_model_with_endpoints(
+        &self,
+        model_name: &str,
+        namespace_filter: &NamespaceFilter,
+    ) -> anyhow::Result<Vec<(EndpointId, ModelDeploymentCard)>> {
         let mut all = self.all_cards().await?;
         all.retain(|(endpoint_id, card)| {
             let matches_name = card.name() == model_name;
-            let matches_namespace = match (is_global_namespace, target_namespace) {
-                (true, _) => true,
-                (false, None) => true,
-                (false, Some(target_ns)) => endpoint_id.namespace == target_ns,
-            };
+            let matches_namespace = namespace_filter.matches(&endpoint_id.namespace);
             matches_name && matches_namespace
         });
-        Ok(all.into_iter().map(|(_eid, card)| card).collect())
+        Ok(all)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::discovery::WorkerSet;
+    use crate::model_card::ModelDeploymentCard;
+
+    fn make_worker_set(namespace: &str) -> WorkerSet {
+        WorkerSet::new(
+            namespace.to_string(),
+            "test-checksum".to_string(),
+            ModelDeploymentCard::default(),
+        )
+    }
+
+    #[test]
+    fn test_is_model_type_list_empty_on_empty_manager() {
+        let mm = ModelManager::new();
+        assert!(is_model_type_list_empty(&mm, ModelType::Chat));
+        assert!(is_model_type_list_empty(&mm, ModelType::Completions));
+        assert!(is_model_type_list_empty(&mm, ModelType::Embedding));
+        assert!(is_model_type_list_empty(&mm, ModelType::Images));
+        assert!(is_model_type_list_empty(&mm, ModelType::Videos));
+        assert!(is_model_type_list_empty(&mm, ModelType::TensorBased));
+        assert!(is_model_type_list_empty(&mm, ModelType::Prefill));
+    }
+
+    #[test]
+    fn test_is_model_type_list_empty_prefill_present() {
+        let mm = ModelManager::new();
+        // A WorkerSet with no engines is treated as a prefill set
+        mm.add_worker_set("model-a", "ns1", make_worker_set("ns1"))
+            .unwrap();
+
+        assert!(!is_model_type_list_empty(&mm, ModelType::Prefill));
+        // Other types should still be empty since the WorkerSet has no engines
+        assert!(is_model_type_list_empty(&mm, ModelType::Chat));
+        assert!(is_model_type_list_empty(&mm, ModelType::Completions));
+        assert!(is_model_type_list_empty(&mm, ModelType::Embedding));
+        assert!(is_model_type_list_empty(&mm, ModelType::Images));
+        assert!(is_model_type_list_empty(&mm, ModelType::Videos));
+        assert!(is_model_type_list_empty(&mm, ModelType::TensorBased));
+    }
+
+    #[test]
+    fn test_is_model_type_list_empty_after_removal() {
+        let mm = ModelManager::new();
+        mm.add_worker_set("model-a", "ns1", make_worker_set("ns1"))
+            .unwrap();
+        assert!(!is_model_type_list_empty(&mm, ModelType::Prefill));
+
+        mm.remove_model("model-a");
+        assert!(is_model_type_list_empty(&mm, ModelType::Prefill));
+    }
+
+    #[test]
+    fn test_is_model_type_list_not_empty_when_other_model_remains() {
+        let mm = ModelManager::new();
+        mm.add_worker_set("model-a", "ns1", make_worker_set("ns1"))
+            .unwrap();
+        mm.add_worker_set("model-b", "ns1", make_worker_set("ns1"))
+            .unwrap();
+
+        // Remove one model — other still provides prefill
+        mm.remove_model("model-a");
+        assert!(!is_model_type_list_empty(&mm, ModelType::Prefill));
+
+        // Remove the last model — now empty
+        mm.remove_model("model-b");
+        assert!(is_model_type_list_empty(&mm, ModelType::Prefill));
     }
 }

lib/llm/src/discovery/worker_set.rs

+// SPDX-FileCopyrightText: Copyright (c) 2024-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+//! A WorkerSet represents a group of workers deployed from the same configuration,
+//! identified by their shared namespace. Each WorkerSet owns a complete pipeline
+//! (engines, KV router, prefill router) built from its specific ModelDeploymentCard.
+
+use std::sync::Arc;
+
+use tokio::sync::watch;
+
+use crate::{
+    discovery::KvWorkerMonitor,
+    kv_router::KvRouter,
+    model_card::ModelDeploymentCard,
+    types::{
+        generic::tensor::TensorStreamingEngine,
+        openai::{
+            chat_completions::OpenAIChatCompletionsStreamingEngine,
+            completions::OpenAICompletionsStreamingEngine,
+            embeddings::OpenAIEmbeddingsStreamingEngine, images::OpenAIImagesStreamingEngine,
+            videos::OpenAIVideosStreamingEngine,
+        },
+    },
+};
+
+/// A set of workers from the same namespace/configuration with their own pipeline.
+pub struct WorkerSet {
+    /// Full namespace (e.g., "ns-abc12345")
+    namespace: String,
+
+    /// MDC checksum for this set's configuration
+    mdcsum: String,
+
+    /// The model deployment card used to build this set's pipeline
+    card: ModelDeploymentCard,
+
+    // Engines — each WorkerSet owns its own pipelines
+    pub(crate) chat_engine: Option<OpenAIChatCompletionsStreamingEngine>,
+    pub(crate) completions_engine: Option<OpenAICompletionsStreamingEngine>,
+    pub(crate) embeddings_engine: Option<OpenAIEmbeddingsStreamingEngine>,
+    pub(crate) images_engine: Option<OpenAIImagesStreamingEngine>,
+    pub(crate) videos_engine: Option<OpenAIVideosStreamingEngine>,
+    pub(crate) tensor_engine: Option<TensorStreamingEngine>,
+
+    /// KV router for this set's workers (if KV mode)
+    pub(crate) kv_router: Option<Arc<KvRouter>>,
+
+    /// Worker monitor for load-based rejection
+    pub(crate) worker_monitor: Option<KvWorkerMonitor>,
+
+    /// Watcher for available instance IDs (from the Client's discovery watch).
+    /// None for in-process models (http/grpc) which don't have a discovery client.
+    instance_count_rx: Option<watch::Receiver<Vec<u64>>>,
+}
+
+impl WorkerSet {
+    pub fn new(namespace: String, mdcsum: String, card: ModelDeploymentCard) -> Self {
+        Self {
+            namespace,
+            mdcsum,
+            card,
+            chat_engine: None,
+            completions_engine: None,
+            embeddings_engine: None,
+            images_engine: None,
+            videos_engine: None,
+            tensor_engine: None,
+            kv_router: None,
+            worker_monitor: None,
+            instance_count_rx: None,
+        }
+    }
+
+    pub fn namespace(&self) -> &str {
+        &self.namespace
+    }
+
+    pub fn mdcsum(&self) -> &str {
+        &self.mdcsum
+    }
+
+    pub fn card(&self) -> &ModelDeploymentCard {
+        &self.card
+    }
+
+    pub fn has_chat_engine(&self) -> bool {
+        self.chat_engine.is_some()
+    }
+
+    pub fn has_completions_engine(&self) -> bool {
+        self.completions_engine.is_some()
+    }
+
+    pub fn has_embeddings_engine(&self) -> bool {
+        self.embeddings_engine.is_some()
+    }
+
+    pub fn has_images_engine(&self) -> bool {
+        self.images_engine.is_some()
+    }
+
+    pub fn has_videos_engine(&self) -> bool {
+        self.videos_engine.is_some()
+    }
+
+    pub fn has_tensor_engine(&self) -> bool {
+        self.tensor_engine.is_some()
+    }
+
+    /// Whether this set has any decode engine (chat or completions)
+    pub fn has_decode_engine(&self) -> bool {
+        self.has_chat_engine() || self.has_completions_engine()
+    }
+
+    /// Whether this set tracks a prefill model (no engine, just lifecycle)
+    pub fn is_prefill_set(&self) -> bool {
+        !self.has_decode_engine()
+            && !self.has_embeddings_engine()
+            && !self.has_images_engine()
+            && !self.has_videos_engine()
+            && !self.has_tensor_engine()
+    }
+
+    /// Build ParsingOptions from this WorkerSet's card configuration.
+    pub fn parsing_options(&self) -> crate::protocols::openai::ParsingOptions {
+        crate::protocols::openai::ParsingOptions::new(
+            self.card.runtime_config.tool_call_parser.clone(),
+            self.card.runtime_config.reasoning_parser.clone(),
+        )
+    }
+
+    /// Number of active workers in this set, derived from the Client's discovery watcher.
+    /// Returns 1 for in-process models (no watcher) since they always have one local worker.
+    pub fn worker_count(&self) -> usize {
+        match &self.instance_count_rx {
+            Some(rx) => rx.borrow().len(),
+            None => 1,
+        }
+    }
+
+    /// Store the instance watcher from the Client's discovery system.
+    /// Must be called before the WorkerSet is wrapped in Arc.
+    pub fn set_instance_watcher(&mut self, rx: watch::Receiver<Vec<u64>>) {
+        self.instance_count_rx = Some(rx);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::model_card::ModelDeploymentCard;
+
+    fn make_worker_set(namespace: &str, mdcsum: &str) -> WorkerSet {
+        WorkerSet::new(
+            namespace.to_string(),
+            mdcsum.to_string(),
+            ModelDeploymentCard::default(),
+        )
+    }
+
+    #[test]
+    fn test_worker_set_basics() {
+        let ws = make_worker_set("ns1", "abc123");
+        assert_eq!(ws.namespace(), "ns1");
+        assert_eq!(ws.mdcsum(), "abc123");
+    }
+
+    #[test]
+    fn test_no_engines_by_default() {
+        let ws = make_worker_set("ns1", "abc123");
+        assert!(!ws.has_chat_engine());
+        assert!(!ws.has_completions_engine());
+        assert!(!ws.has_embeddings_engine());
+        assert!(!ws.has_images_engine());
+        assert!(!ws.has_tensor_engine());
+        assert!(!ws.has_decode_engine());
+        assert!(ws.is_prefill_set());
+    }
+
+    #[test]
+    fn test_worker_count_without_watcher() {
+        // In-process models have no discovery watcher; worker_count defaults to 1
+        let ws = make_worker_set("ns1", "abc");
+        assert_eq!(ws.worker_count(), 1);
+    }
+
+    #[test]
+    fn test_worker_count_with_watcher() {
+        let mut ws = make_worker_set("ns1", "abc");
+
+        // Simulate a discovery watcher with 3 workers
+        let (tx, rx) = watch::channel(vec![1, 2, 3]);
+        ws.set_instance_watcher(rx);
+        assert_eq!(ws.worker_count(), 3);
+
+        // Workers leave → count drops
+        tx.send(vec![1]).unwrap();
+        assert_eq!(ws.worker_count(), 1);
+
+        // All workers gone → count is 0
+        tx.send(vec![]).unwrap();
+        assert_eq!(ws.worker_count(), 0);
+    }
+
+    #[test]
+    fn test_worker_count_with_empty_watcher() {
+        // Discovery watcher starts empty (no workers have joined yet)
+        let mut ws = make_worker_set("ns1", "abc");
+        let (_tx, rx) = watch::channel::<Vec<u64>>(vec![]);
+        ws.set_instance_watcher(rx);
+        assert_eq!(ws.worker_count(), 0);
+    }
+
+    #[test]
+    fn test_worker_count_updates_on_join() {
+        let mut ws = make_worker_set("ns1", "abc");
+        let (tx, rx) = watch::channel::<Vec<u64>>(vec![]);
+        ws.set_instance_watcher(rx);
+        assert_eq!(ws.worker_count(), 0);
+
+        // Workers join one by one
+        tx.send(vec![100]).unwrap();
+        assert_eq!(ws.worker_count(), 1);
+
+        tx.send(vec![100, 200]).unwrap();
+        assert_eq!(ws.worker_count(), 2);
+
+        tx.send(vec![100, 200, 300]).unwrap();
+        assert_eq!(ws.worker_count(), 3);
+    }
+}

lib/llm/src/entrypoint/input/common.rs

@@ -12,6 +12,7 @@ use crate::{
     kv_router::{DirectRoutingRouter, KvPushRouter, KvRouter, PrefillRouter},
     migration::Migration,
     model_card::ModelDeploymentCard,
+    namespace::NamespaceFilter,
     preprocessor::{OpenAIPreprocessor, prompt::PromptFormatter},
     protocols::common::llm_backend::{BackendOutput, LLMEngineOutput, PreprocessedRequest},
     request_template::RequestTemplate,
@@ -82,8 +83,14 @@ pub async fn prepare_engine(
                 )
                 .await?;
             let inner_watch_obj = watch_obj.clone();
+            let namespace_filter = NamespaceFilter::from_namespace_and_prefix(
+                local_model.namespace(),
+                local_model.namespace_prefix(),
+            );
             let _watcher_task = tokio::spawn(async move {
-                inner_watch_obj.watch(discovery_stream, None).await;
+                inner_watch_obj
+                    .watch(discovery_stream, namespace_filter)
+                    .await;
             });
             tracing::info!("Waiting for remote model..");
 

lib/llm/src/entrypoint/input/grpc.rs

@@ -9,7 +9,7 @@ use crate::{
     entrypoint::{EngineConfig, RouterConfig, input::common},
     grpc::service::kserve,
     http::service::metrics::Metrics,
-    namespace::is_global_namespace,
+    namespace::NamespaceFilter,
     types::openai::{
         chat_completions::{NvCreateChatCompletionRequest, NvCreateChatCompletionStreamResponse},
         completions::{NvCreateCompletionRequest, NvCreateCompletionResponse},
@@ -38,18 +38,16 @@ pub async fn run(
             let router_config = model.router_config();
             let migration_limit = model.migration_limit();
             // Listen for models registering themselves, add them to gRPC service
-            let namespace = model.namespace().unwrap_or("");
-            let target_namespace = if is_global_namespace(namespace) {
-                None
-            } else {
-                Some(namespace.to_string())
-            };
+            let namespace_filter = NamespaceFilter::from_namespace_and_prefix(
+                model.namespace(),
+                model.namespace_prefix(),
+            );
             run_watcher(
                 distributed_runtime.clone(),
                 grpc_service.state().manager_clone(),
                 router_config.clone(),
                 migration_limit,
-                target_namespace,
+                namespace_filter,
             )
             .await?;
             grpc_service
@@ -113,7 +111,7 @@ async fn run_watcher(
     model_manager: Arc<ModelManager>,
     router_config: RouterConfig,
     migration_limit: u32,
-    target_namespace: Option<String>,
+    namespace_filter: NamespaceFilter,
 ) -> anyhow::Result<()> {
     // Create metrics for migration tracking (not exposed via /metrics in gRPC mode)
     let metrics = Arc::new(Metrics::new());
@@ -140,9 +138,7 @@ async fn run_watcher(
 
     // Pass the discovery stream to the watcher
     let _watcher_task = tokio::spawn(async move {
-        watch_obj
-            .watch(discovery_stream, target_namespace.as_deref())
-            .await;
+        watch_obj.watch(discovery_stream, namespace_filter).await;
     });
 
     Ok(())

lib/llm/src/entrypoint/input/http.rs

@@ -9,7 +9,7 @@ use crate::{
     engines::StreamingEngineAdapter,
     entrypoint::{ChatEngineFactoryCallback, EngineConfig, RouterConfig, input::common},
     http::service::service_v2::{self, HttpService},
-    namespace::is_global_namespace,
+    namespace::NamespaceFilter,
     types::openai::{
         chat_completions::{NvCreateChatCompletionRequest, NvCreateChatCompletionStreamResponse},
         completions::{NvCreateCompletionRequest, NvCreateCompletionResponse},
@@ -66,20 +66,17 @@ pub async fn run(
             let router_config = model.router_config();
             let migration_limit = model.migration_limit();
             // Listen for models registering themselves, add them to HTTP service
-            // Check if we should filter by namespace (based on the local model's namespace)
-            // Get namespace from the model, fallback to endpoint_id namespace if not set
-            let namespace = model.namespace().unwrap_or("");
-            let target_namespace = if is_global_namespace(namespace) {
-                None
-            } else {
-                Some(namespace.to_string())
-            };
+            // Create namespace filter from model configuration
+            let namespace_filter = NamespaceFilter::from_namespace_and_prefix(
+                model.namespace(),
+                model.namespace_prefix(),
+            );
             run_watcher(
                 distributed_runtime.clone(),
                 http_service.state().manager_clone(),
                 router_config.clone(),
                 migration_limit,
-                target_namespace,
+                namespace_filter,
                 Arc::new(http_service.clone()),
                 http_service.state().metrics_clone(),
                 chat_engine_factory.clone(),
@@ -157,7 +154,7 @@ async fn run_watcher(
     model_manager: Arc<ModelManager>,
     router_config: RouterConfig,
     migration_limit: u32,
-    target_namespace: Option<String>,
+    namespace_filter: NamespaceFilter,
     http_service: Arc<HttpService>,
     metrics: Arc<crate::http::service::metrics::Metrics>,
     chat_engine_factory: Option<ChatEngineFactoryCallback>,
@@ -193,9 +190,7 @@ async fn run_watcher(
 
     // Pass the discovery stream to the watcher
     let _watcher_task = tokio::spawn(async move {
-        watch_obj
-            .watch(discovery_stream, target_namespace.as_deref())
-            .await;
+        watch_obj.watch(discovery_stream, namespace_filter).await;
     });
 
     Ok(())

lib/llm/src/grpc/service/kserve.rs

@@ -377,10 +377,8 @@ impl GrpcInferenceService for KserveService {
             }
         }
 
-        let model = completion_request.inner.model.clone();
-        let parsing_options = self.state.manager.get_parsing_options(&model);
-
-        let stream = completion_response_stream(self.state_clone(), completion_request).await?;
+        let (stream, parsing_options) =
+            completion_response_stream(self.state_clone(), completion_request).await?;
 
         let completion_response =
             NvCreateCompletionResponse::from_annotated_stream(stream, parsing_options)
@@ -494,12 +492,9 @@ impl GrpcInferenceService for KserveService {
                     }
                 }
 
-                let model = completion_request.inner.model.clone();
-                let parsing_options = state.manager.get_parsing_options(&model);
-
                 let streaming = completion_request.inner.stream.unwrap_or(false);
 
-                let stream = completion_response_stream(state.clone(), completion_request).await?;
+                let (stream, parsing_options) = completion_response_stream(state.clone(), completion_request).await?;
 
                 if streaming {
                     pin_mut!(stream);

lib/llm/src/grpc/service/openai.rs

@@ -9,6 +9,7 @@ use dynamo_runtime::{
 use futures::{Stream, StreamExt, stream};
 use std::sync::Arc;
 
+use crate::protocols::openai::ParsingOptions;
 use crate::protocols::openai::completions::{
     NvCreateCompletionRequest, NvCreateCompletionResponse,
 };
@@ -43,7 +44,13 @@ pub const ANNOTATION_REQUEST_ID: &str = "request_id";
 pub async fn completion_response_stream(
     state: Arc<kserve::State>,
     request: NvCreateCompletionRequest,
-) -> Result<impl Stream<Item = Annotated<NvCreateCompletionResponse>>, Status> {
+) -> Result<
+    (
+        impl Stream<Item = Annotated<NvCreateCompletionResponse>>,
+        ParsingOptions,
+    ),
+    Status,
+> {
     // create the context for the request
     // [WIP] from request id.
     let request_id = get_or_create_request_id(request.inner.user.as_deref());
@@ -66,9 +73,9 @@ pub async fn completion_response_stream(
     let model = &request.inner.model;
 
     // todo - error handling should be more robust
-    let engine = state
+    let (engine, parsing_options) = state
         .manager()
-        .get_completions_engine(model)
+        .get_completions_engine_with_parsing(model)
         .map_err(|_| Status::not_found("model not found"))?;
 
     let http_queue_guard = state.metrics_clone().create_http_queue_guard(model);
@@ -130,7 +137,7 @@ pub async fn completion_response_stream(
     // without need to be cancelled.
     connection_handle.disarm();
 
-    Ok(stream)
+    Ok((stream, parsing_options))
 }
 
 /// This method will consume an AsyncEngineStream and monitor for disconnects or context cancellation.

lib/llm/src/http/service/anthropic.rs

@@ -194,9 +194,9 @@ async fn anthropic_messages(
 
     tracing::trace!("Getting chat completions engine for model: {}", model);
 
-    let engine = state
+    let (engine, parsing_options) = state
         .manager()
-        .get_chat_completions_engine(&model)
+        .get_chat_completions_engine_with_parsing(&model)
         .map_err(|_| {
             anthropic_error(
                 StatusCode::NOT_FOUND,
@@ -205,8 +205,6 @@ async fn anthropic_messages(
             )
         })?;
 
-    let parsing_options = state.manager().get_parsing_options(&model);
-
     let mut response_collector = state.metrics_clone().create_response_collector(&model);
 
     tracing::trace!("Issuing generate call for Anthropic messages");