refactor(router): refactor random/RR/LL/pow-of-2 as builtin plugins

Cargo.toml

@@ -62,7 +62,7 @@ repository = "https://github.com/ai-dynamo/dynamo.git"
 keywords = ["llm", "genai", "inference", "nvidia", "distributed"]
 
 [workspace.dependencies]
-dynamo-custom-policy-builtin = { path = "lib/router-plugins/builtin", version = "1.7.0" }
+dynamo-router-policies = { path = "lib/router-plugins/builtin", version = "1.7.0" }
 dynamo-generate-format-catalog = { path = "lib/generate-format-catalog", version = "1.7.0" }
 # Published separately by https://github.com/ai-dynamo/aisimulate.
 aisimulate-core = { version = "=0.13.0-dev.202610290000000087" }

deploy/inference-gateway/ext-proc/Cargo.toml

@@ -16,7 +16,7 @@ name = "dynamo-ext-proc"
 path = "src/bin/dynamo-ext-proc.rs"
 
 [dependencies]
-dynamo-custom-policy-builtin = { workspace = true }
+dynamo-router-policies = { workspace = true }
 async-trait = { workspace = true }
 dynamo-kv-router = { workspace = true, features = [
     "metrics",

deploy/inference-gateway/ext-proc/src/peer_discovery.rs

@@ -283,7 +283,7 @@ mod tests {
             SelectionServiceBuilder::new(
                 kv_router_config_from_dynamo_env(),
                 WorkerType::Aggregated,
-                dynamo_custom_policy_builtin::default_registry(),
+                dynamo_router_policies::default_registry(),
             )
             .indexer_threads(1)
             .replica_sync(listener_port, Vec::new())

deploy/inference-gateway/ext-proc/src/selector.rs

@@ -113,7 +113,7 @@ impl Selector {
         let mut builder = SelectionServiceBuilder::new(
             kv_router_config,
             WorkerType::Aggregated,
-            policy_registry.with_default_factory(dynamo_custom_policy_builtin::default_factory()),
+            dynamo_router_policies::with_defaults(policy_registry),
         )
         .indexer_threads(cfg.selector_threads);
         if let Some(peer_replication) = peer_replication {

docs/fern/pages/reference/general/releases/deprecations.mdx

@@ -53,6 +53,10 @@ Upgrading? Pick the version you run today to see the dependency migration and th
 
   > **Migrate:** Replace `WorkerInputs::OCCUPANCY` with `WorkerInputs::ACTIVE_REQUESTS` in custom worker-selection policies.
 
+<span className="dynref-badge dynref-badge--blue">Behavioral</span> **Your own Rust code that constructs a round-robin, random or least-loaded `PushRouter` must pass the router-mode plugins** ([#17713](https://github.com/ai-dynamo/dynamo/pull/17713)). Without them, the router fails to build.
+
+  > **Migrate:** CLI, Python and Kubernetes deployments need no change. If your Rust code creates a `PushRouter` in one of these modes, replace `PushRouter::from_client(client, RouterMode::RoundRobin)` with `PushRouter::from_client_with_options(client, RouterMode::RoundRobin, dynamo_llm::kv_router::plugins::push_router_options())`. If your code depends only on `dynamo-runtime`, add `dynamo-llm`, or implement `InstanceSelector`.
+
 <a id="v160"></a>
 
 ## v1.6.0 - Oct 22, 2026

lib/bindings/python/Cargo.toml

@@ -99,7 +99,7 @@ uuid = { version = "1.18.1" }
 
 # kv-indexer / slot-tracker / shared kv-router types
 dynamo-kv-router = { path = "../../kv-router" }
-dynamo-custom-policy-builtin = { path = "../../router-plugins/builtin" }
+dynamo-router-policies = { path = "../../router-plugins/builtin" }
 dynamo-worker-selection-policy-catalog = { path = "../../router-plugins/catalog", optional = true }
 # The replaceable /generate format catalog; custom images point this name at their own.
 dynamo-generate-format-catalog = { path = "../../generate-format-catalog" }

lib/bindings/python/rust/lib.rs

@@ -492,10 +492,10 @@ pub(crate) fn linked_worker_selection_policy_registry() -> RouterPluginRegistry
 
 #[cfg(feature = "custom-policy")]
 fn register_core_with_router_plugins(m: &Bound<'_, PyModule>) -> PyResult<()> {
-    let mut registry = dynamo_kv_router::plugins::RouterPluginRegistry::default();
+    let mut registry = dynamo_router_policies::default_registry();
     // The policies Dynamo ships register first, so a replaced catalog that reuses one of their
     // type names fails here instead of silently overriding it.
-    dynamo_custom_policy_builtin::register(&mut registry)
+    dynamo_router_policies::register(&mut registry)
         .map_err(|error| PyRuntimeError::new_err(error.to_string()))?;
     dynamo_worker_selection_policy_catalog::register(&mut registry)
         .map_err(|error| PyRuntimeError::new_err(error.to_string()))?;
@@ -1934,9 +1934,10 @@ impl Endpoint {
         crate::future_into_py(py, async move {
             let client = inner.client().await.map_err(to_pyerr)?;
             let push_router =
-                rs::pipeline::PushRouter::<rmpv::Value, RsAnnotated<rmpv::Value>>::from_client(
+                rs::pipeline::PushRouter::<rmpv::Value, RsAnnotated<rmpv::Value>>::from_client_with_options(
                     client,
                     router_mode.into(),
+                    dynamo_llm::kv_router::plugins::push_router_options(),
                 )
                 .await
                 .map_err(to_pyerr)?;

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

@@ -285,7 +285,7 @@ impl KvRouterConfig {
                  selects worker-selection policy instance {instance:?} for {worker_type}"
             )));
         }
-        dynamo_custom_policy_builtin::startup_policy_parameters(&self.inner, role)
+        dynamo_router_policies::startup_policy_parameters(&self.inner, role)
             .into_iter()
             .map(|(name, value)| match value.as_f64() {
                 Some(value) => Ok((name, value)),
@@ -985,7 +985,7 @@ mod plugin_input_tests {
     #[test]
     fn explicit_policy_retains_frontend_restrictions() {
         let plugins = RouterPlugins::default()
-            .with_worker_selection(dynamo_custom_policy_builtin::default_factory());
+            .with_worker_selection(dynamo_router_policies::default_factory());
         assert!(validate_router_plugin_input(&plugins, &Input::Http, true).is_ok());
         assert_eq!(
             validate_router_plugin_input(&plugins, &Input::Http, false),

lib/kv-router/src/plugins/registry.rs

@@ -311,6 +311,27 @@ impl RouterPluginRegistry {
         })
     }
 
+    /// Build the factory for one registered policy type with default parameters, as a routing
+    /// mode names it (for example `round-robin`) without a policy file.
+    pub fn resolve_type(
+        &self,
+        policy_type: &str,
+    ) -> Result<WorkerSelectionPolicyFactory, WorkerSelectionPolicyRegistryError> {
+        let provider = self.providers.get(policy_type).ok_or_else(|| {
+            WorkerSelectionPolicyRegistryError::UnknownType {
+                name: policy_type.to_owned(),
+                available: self.available_policy_types(),
+            }
+        })?;
+        provider(&WorkerSelectionPolicyParameters::new(
+            serde_yaml::Value::Mapping(Default::default()),
+        ))
+        .map_err(|source| WorkerSelectionPolicyRegistryError::Provider {
+            policy_type: policy_type.to_owned(),
+            source,
+        })
+    }
+
     fn available_policy_types(&self) -> String {
         let mut available = self.providers.keys().cloned().collect::<Vec<_>>();
         available.sort_unstable();

lib/kv-router/src/plugins/worker_selection/context.rs

@@ -25,6 +25,7 @@ pub struct WorkerSelectionContext<'a> {
     pub(crate) track_prefill_tokens: bool,
     pub(crate) pinned_worker: Option<WorkerWithDpRank>,
     pub(crate) router_temperature_override: Option<f64>,
+    pub(crate) preview: bool,
 }
 
 impl WorkerSelectionContext<'_> {
@@ -90,4 +91,15 @@ impl WorkerSelectionContext<'_> {
     pub fn router_temperature_override(&self) -> Option<f64> {
         self.router_temperature_override
     }
+
+    /// Whether this selection only previews a worker, as a peek does, without routing the
+    /// request to it. A picker that keeps state between selections, such as a rotation
+    /// cursor, should read that state without advancing it. Always `false` when the router
+    /// routes with KV state.
+    // TODO(v1.8): document once custom pickers can run on the hosted path; until then only the
+    // builtin router-mode plugins receive previews.
+    #[doc(hidden)]
+    pub fn is_preview(&self) -> bool {
+        self.preview
+    }
 }