diff --git a/crates/turborepo-lib/src/commands/config.rs b/crates/turborepo-lib/src/commands/config.rs
index 76b7b6cb5ffd6..b8b617465a081 100644
--- a/crates/turborepo-lib/src/commands/config.rs
+++ b/crates/turborepo-lib/src/commands/config.rs
@@ -1,7 +1,7 @@
 use camino::Utf8Path;
 use serde::Serialize;
 use turbopath::AbsoluteSystemPathBuf;
-use turborepo_repository::{cargo::CargoContributor, package_graph::PackageGraph};
+use turborepo_repository::package_graph::PackageGraph;
 use turborepo_types::{EnvMode, UIMode};
 
 use crate::{
@@ -46,7 +46,7 @@ pub async fn run(repo_root: AbsoluteSystemPathBuf, args: Args) -> Result<(), cli
     let mut builder = PackageGraph::builder_optional(&repo_root, root_package_json)
         .with_allow_no_package_manager(config.allow_no_package_manager());
     if cargo_enabled {
-        builder = builder.with_contributor(CargoContributor::new(repo_root.clone()));
+        builder = builder.with_cargo();
     }
     let package_graph = builder.build().await?;
 
diff --git a/crates/turborepo-lib/src/commands/daemon.rs b/crates/turborepo-lib/src/commands/daemon.rs
index 47624b61419bc..7401865f4dbcd 100644
--- a/crates/turborepo-lib/src/commands/daemon.rs
+++ b/crates/turborepo-lib/src/commands/daemon.rs
@@ -346,16 +346,6 @@ pub async fn daemon_server(
         {
             let cargo_enabled = crate::run::builder::cargo_enabled(&base.opts().future_flags);
             move |args| {
-                // Mirror the run builder: the daemon-side watcher must see
-                // the same package set a run would.
-                let mut extra_contributors: Vec<
-                    std::sync::Arc<dyn turborepo_repository::toolchain::RepositoryContributor>,
-                > = Vec::new();
-                if cargo_enabled {
-                    extra_contributors.push(turborepo_repository::cargo::CargoContributor::new(
-                        args.repo_root.clone(),
-                    ));
-                }
                 PackageChangesWatcher::new(
                     args.repo_root,
                     args.file_events,
@@ -363,7 +353,7 @@ pub async fn daemon_server(
                     args.custom_turbo_json_path,
                     false,
                     args.allow_no_package_manager,
-                    extra_contributors,
+                    cargo_enabled,
                 )
             }
         },
diff --git a/crates/turborepo-lib/src/commands/get_mfe_port.rs b/crates/turborepo-lib/src/commands/get_mfe_port.rs
index fbdf796fd5395..82cd974dfb620 100644
--- a/crates/turborepo-lib/src/commands/get_mfe_port.rs
+++ b/crates/turborepo-lib/src/commands/get_mfe_port.rs
@@ -4,7 +4,7 @@ use thiserror::Error;
 use turbopath::{AbsoluteSystemPath, AbsoluteSystemPathBuf};
 use turborepo_microfrontends::TurborepoMfeConfig;
 use turborepo_repository::{
-    cargo::{CargoContributor, CARGO_TOML},
+    cargo::CARGO_TOML,
     package_graph::{PackageGraph, PackageGraphNodeKind, PackageName, PackageNode},
     package_json::PackageJson,
     toolchain::ToolchainId,
@@ -71,7 +71,7 @@ async fn build_package_graph(base: &CommandBase) -> Result<PackageGraph, Error>
         .with_single_package_mode(base.opts().run_opts.single_package)
         .with_allow_no_package_manager(base.opts().repo_opts.allow_no_package_manager);
     if cargo_enabled {
-        builder = builder.with_contributor(CargoContributor::new(repo_root.to_owned()));
+        builder = builder.with_cargo();
     }
 
     Ok(builder.build().await?)
diff --git a/crates/turborepo-lib/src/commands/prune.rs b/crates/turborepo-lib/src/commands/prune.rs
index 6a97230a8f297..9fb263134a51d 100644
--- a/crates/turborepo-lib/src/commands/prune.rs
+++ b/crates/turborepo-lib/src/commands/prune.rs
@@ -532,9 +532,7 @@ impl<'a> Prune<'a> {
         let mut graph_builder = PackageGraph::builder_optional(&base.repo_root, root_package_json)
             .with_allow_no_package_manager(allow_missing_package_manager);
         if cargo_enabled {
-            graph_builder = graph_builder.with_contributor(
-                turborepo_repository::cargo::CargoContributor::new(base.repo_root.clone()),
-            );
+            graph_builder = graph_builder.with_cargo();
         }
         let package_graph = graph_builder.build().await?;
 
diff --git a/crates/turborepo-lib/src/devtools.rs b/crates/turborepo-lib/src/devtools.rs
index 0364ad7f0200e..bd4fb92687889 100644
--- a/crates/turborepo-lib/src/devtools.rs
+++ b/crates/turborepo-lib/src/devtools.rs
@@ -11,10 +11,7 @@ use turborepo_devtools::{
     package_graph_to_data, GraphData, GraphEdge, RepositoryGraphBuilder, TaskGraphData,
     TaskGraphError, TaskNode,
 };
-use turborepo_repository::{
-    cargo::CargoContributor,
-    package_graph::{PackageGraph, PackageGraphBuilder, PackageName},
-};
+use turborepo_repository::package_graph::{PackageGraph, PackageGraphBuilder, PackageName};
 use turborepo_task_id::TaskName;
 
 use crate::{
@@ -69,7 +66,7 @@ impl ProperTaskGraphBuilder {
             .with_single_package_mode(opts.run_opts.single_package)
             .with_allow_no_package_manager(opts.repo_opts.allow_no_package_manager);
         if cargo_enabled(&opts.future_flags) {
-            builder = builder.with_contributor(CargoContributor::new(self.repo_root.clone()));
+            builder = builder.with_cargo();
         }
 
         builder
diff --git a/crates/turborepo-lib/src/engine/mod.rs b/crates/turborepo-lib/src/engine/mod.rs
index d1a256177c01c..5d2a8243f3ccf 100644
--- a/crates/turborepo-lib/src/engine/mod.rs
+++ b/crates/turborepo-lib/src/engine/mod.rs
@@ -380,9 +380,7 @@ mod test {
             .with_package_discovery(DummyDiscovery(
                 turbopath::AbsoluteSystemPathBuf::try_from(tmp.path()).unwrap(),
             ))
-            .with_contributor(turborepo_repository::cargo::CargoContributor::new(
-                root.to_owned(),
-            ))
+            .with_cargo()
             .build()
             .await
             .unwrap();
diff --git a/crates/turborepo-lib/src/microfrontends.rs b/crates/turborepo-lib/src/microfrontends.rs
index 14a098de861d8..bb7a6c8a49675 100644
--- a/crates/turborepo-lib/src/microfrontends.rs
+++ b/crates/turborepo-lib/src/microfrontends.rs
@@ -583,8 +583,7 @@ mod test {
     use turbopath::AbsoluteSystemPathBuf;
     use turborepo_microfrontends::MICROFRONTENDS_PACKAGE;
     use turborepo_repository::{
-        cargo::CargoContributor, package_graph::PackageGraph, package_json::PackageJson,
-        package_manager::PackageManager,
+        package_graph::PackageGraph, package_json::PackageJson, package_manager::PackageManager,
     };
 
     use super::*;
@@ -657,7 +656,7 @@ mod test {
         write_mfe_config(&root, "aggregate");
 
         let graph = PackageGraph::builder_optional(&root, None)
-            .with_contributor(CargoContributor::new(root.clone()))
+            .with_cargo()
             .build()
             .await
             .unwrap();
diff --git a/crates/turborepo-lib/src/package_changes_watcher.rs b/crates/turborepo-lib/src/package_changes_watcher.rs
index f2f1929199efd..a346dd2862710 100644
--- a/crates/turborepo-lib/src/package_changes_watcher.rs
+++ b/crates/turborepo-lib/src/package_changes_watcher.rs
@@ -24,7 +24,7 @@ use turborepo_repository::{
     },
     package_graph::{PackageGraph, PackageName, WorkspacePackage},
     package_json::{self, PackageJson},
-    toolchain::{RepositoryContributor, WatchSpec},
+    toolchain::WatchSpec,
 };
 use turborepo_scm::GitHashes;
 
@@ -70,7 +70,7 @@ impl PackageChangesWatcher {
         custom_turbo_json_path: Option<AbsoluteSystemPathBuf>,
         single_package: bool,
         allow_no_package_manager: bool,
-        extra_contributors: Vec<Arc<dyn RepositoryContributor>>,
+        cargo_enabled: bool,
     ) -> Self {
         let (exit_tx, exit_rx) = oneshot::channel();
         let (package_change_events_tx, package_change_events_rx) =
@@ -83,7 +83,7 @@ impl PackageChangesWatcher {
             custom_turbo_json_path,
             single_package,
             allow_no_package_manager,
-            extra_contributors,
+            cargo_enabled,
         );
 
         let _handle = tokio::spawn(subscriber.watch(exit_rx));
@@ -134,10 +134,8 @@ struct Subscriber {
     custom_turbo_json_path: Option<AbsoluteSystemPathBuf>,
     single_package: bool,
     allow_no_package_manager: bool,
-    /// Toolchains registered in addition to JavaScript (e.g. Cargo when
-    /// futureFlags.experimentalCargoWorkspaces is enabled), mirroring the
-    /// run builder so the watcher sees the same package graph a run would.
-    extra_contributors: Vec<Arc<dyn RepositoryContributor>>,
+    /// Mirrors the run builder so the watcher observes the same Cargo scopes.
+    cargo_enabled: bool,
 }
 
 fn is_in_git_folder(path: &AnchoredSystemPath) -> bool {
@@ -372,7 +370,7 @@ impl Subscriber {
         custom_turbo_json_path: Option<AbsoluteSystemPathBuf>,
         single_package: bool,
         allow_no_package_manager: bool,
-        extra_contributors: Vec<Arc<dyn RepositoryContributor>>,
+        cargo_enabled: bool,
     ) -> Self {
         // Try to canonicalize the custom path to match what the file watcher reports
         let normalized_custom_path = custom_turbo_json_path.map(|path| {
@@ -424,16 +422,12 @@ impl Subscriber {
             custom_turbo_json_path: normalized_custom_path,
             single_package,
             allow_no_package_manager,
-            extra_contributors,
+            cargo_enabled,
         }
     }
 
     async fn initialize_repo_state(&self) -> Option<RepoState> {
-        let cargo_registered = self
-            .extra_contributors
-            .iter()
-            .any(|toolchain| toolchain.id() == turborepo_repository::toolchain::ToolchainId::RUST);
-        let allow_missing_for_cargo = cargo_registered
+        let allow_missing_for_cargo = self.cargo_enabled
             && self
                 .repo_root
                 .join_component(turborepo_repository::cargo::CARGO_TOML)
@@ -453,8 +447,8 @@ impl Subscriber {
             PackageGraph::builder_optional(&self.repo_root, root_package_json.clone())
                 .with_single_package_mode(self.single_package)
                 .with_allow_no_package_manager(self.allow_no_package_manager);
-        for toolchain in &self.extra_contributors {
-            builder = builder.with_contributor(toolchain.clone());
+        if self.cargo_enabled {
+            builder = builder.with_cargo();
         }
         let Ok(pkg_dep_graph) = builder.build().await else {
             tracing::debug!("package graph not available, package watcher not available");
@@ -886,11 +880,10 @@ mod test {
         hash_watcher::HashWatcher, NotifyError, OptionalWatch, WatchEventSender, WatchSource,
     };
     use turborepo_repository::{
-        cargo::CargoContributor,
         change_mapper::{ChangeMapper, GlobalDepsPackageChangeMapper, PackageChanges},
         package_graph::{PackageGraph, PackageGraphBuilder, PackageName, PackageTaskContextKind},
         package_json::PackageJson,
-        toolchain::{RepositoryContributor, WatchSpec},
+        toolchain::WatchSpec,
     };
     use turborepo_scm::{GitHashes, SCM};
 
@@ -982,7 +975,7 @@ mod test {
     fn test_subscriber(
         repo_root: &AbsoluteSystemPathBuf,
         single_package: bool,
-        extra_contributors: Vec<Arc<dyn RepositoryContributor>>,
+        cargo_enabled: bool,
     ) -> Subscriber {
         let (_file_events_tx, file_events) = WatchSource::channel_for_root(repo_root.as_std_path());
         let (_discovery_tx, discovery_rx) = watch::channel(None);
@@ -1000,15 +993,15 @@ mod test {
             None,
             single_package,
             false,
-            extra_contributors,
+            cargo_enabled,
         )
     }
 
     async fn initialize_test_state(
         repo_root: &AbsoluteSystemPathBuf,
-        extra_contributors: Vec<Arc<dyn RepositoryContributor>>,
+        cargo_enabled: bool,
     ) -> Option<super::RepoState> {
-        test_subscriber(repo_root, false, extra_contributors)
+        test_subscriber(repo_root, false, cargo_enabled)
             .initialize_repo_state()
             .await
     }
@@ -1031,10 +1024,9 @@ mod test {
             .create_with_contents(b"{\"tasks\":{\"build\":{}}}")
             .unwrap();
 
-        let state =
-            initialize_test_state(&repo_root, vec![CargoContributor::new(repo_root.clone())])
-                .await
-                .expect("native toolchain permits an absent root package.json");
+        let state = initialize_test_state(&repo_root, true)
+            .await
+            .expect("Cargo permits an absent root package.json");
         assert!(!state.pkg_dep_graph.has_root_javascript_scope());
         assert!(state.root_turbo_json.is_some());
         assert_eq!(state.pkg_dep_graph.active_watch_spec(), cargo_watch_spec());
@@ -1076,10 +1068,9 @@ mod test {
             .create_with_contents(br#"{"name":"web"}"#)
             .unwrap();
 
-        let state =
-            initialize_test_state(&repo_root, vec![CargoContributor::new(repo_root.clone())])
-                .await
-                .expect("mixed graph initializes");
+        let state = initialize_test_state(&repo_root, true)
+            .await
+            .expect("mixed graph initializes");
         let names: HashSet<_> = hash_scopes(&state.pkg_dep_graph)
             .map(|scope| scope.name)
             .collect();
@@ -1097,18 +1088,16 @@ mod test {
         let tmp = tempfile::tempdir().unwrap();
         let repo_root = canonical_temp_root(&tmp);
         assert!(
-            initialize_test_state(&repo_root, vec![CargoContributor::new(repo_root.clone())])
-                .await
-                .is_none(),
+            initialize_test_state(&repo_root, true).await.is_none(),
             "registered Cargo without a root Cargo.toml must not permit a missing package.json"
         );
 
         write_cargo_workspace(&repo_root);
-        let subscriber = test_subscriber(
-            &repo_root,
-            true,
-            vec![CargoContributor::new(repo_root.clone())],
+        assert!(
+            initialize_test_state(&repo_root, false).await.is_none(),
+            "a Cargo manifest must not bypass the disabled feature"
         );
+        let subscriber = test_subscriber(&repo_root, true, true);
         let state = subscriber
             .initialize_repo_state()
             .await
@@ -1142,22 +1131,14 @@ mod test {
             .create_with_contents(b"{")
             .unwrap();
         assert!(load_root_package_json(&repo_root, true).is_err());
-        assert!(
-            initialize_test_state(&repo_root, vec![CargoContributor::new(repo_root.clone())])
-                .await
-                .is_none()
-        );
+        assert!(initialize_test_state(&repo_root, true).await.is_none());
 
         repo_root.join_component("package.json").remove().unwrap();
         repo_root
             .join_component("Cargo.toml")
             .create_with_contents(b"[workspace")
             .unwrap();
-        assert!(
-            initialize_test_state(&repo_root, vec![CargoContributor::new(repo_root.clone())])
-                .await
-                .is_none()
-        );
+        assert!(initialize_test_state(&repo_root, true).await.is_none());
     }
 
     #[test]
@@ -1200,11 +1181,7 @@ mod test {
             .unwrap();
         write_cargo_workspace(&repo_root);
 
-        let subscriber = test_subscriber(
-            &repo_root,
-            true,
-            vec![CargoContributor::new(repo_root.clone())],
-        );
+        let subscriber = test_subscriber(&repo_root, true, true);
         assert_eq!(
             *subscriber
                 .watch_spec
@@ -1839,7 +1816,7 @@ mod test {
             None,
             single_package,
             allow_no_package_manager,
-            Vec::new(),
+            false,
         );
 
         TestWatcherHandle {
diff --git a/crates/turborepo-lib/src/run/builder.rs b/crates/turborepo-lib/src/run/builder.rs
index 3be6c335b72dc..08b6343b14dec 100644
--- a/crates/turborepo-lib/src/run/builder.rs
+++ b/crates/turborepo-lib/src/run/builder.rs
@@ -571,9 +571,7 @@ impl RunBuilder {
                         turborepo_task_hash::hash_sorted_closures,
                     ));
             if cargo_enabled(&self.opts.future_flags) {
-                builder = builder.with_contributor(
-                    turborepo_repository::cargo::CargoContributor::new(self.repo_root.to_owned()),
-                );
+                builder = builder.with_cargo();
             }
 
             let graph = builder
diff --git a/crates/turborepo-lib/src/run/watch.rs b/crates/turborepo-lib/src/run/watch.rs
index 2a3a87ae67a49..7f1011f18167d 100644
--- a/crates/turborepo-lib/src/run/watch.rs
+++ b/crates/turborepo-lib/src/run/watch.rs
@@ -300,16 +300,8 @@ impl WatchClient {
             source,
             scm,
         ));
-        // The watcher builds its own package graph; register the same
-        // toolchains a run would so it watches the same package set.
-        let mut extra_contributors: Vec<
-            std::sync::Arc<dyn turborepo_repository::toolchain::RepositoryContributor>,
-        > = Vec::new();
-        if crate::run::builder::cargo_enabled(&base.opts().future_flags) {
-            extra_contributors.push(turborepo_repository::cargo::CargoContributor::new(
-                base.repo_root.clone(),
-            ));
-        }
+        // The watcher builds its own graph and must enable the same ecosystems.
+        let cargo_enabled = crate::run::builder::cargo_enabled(&base.opts().future_flags);
         let package_changes_watcher = PackageChangesWatcher::new(
             base.repo_root.clone(),
             watcher.source(),
@@ -317,7 +309,7 @@ impl WatchClient {
             custom_turbo_json_path,
             base.opts().run_opts.single_package,
             base.opts().repo_opts.allow_no_package_manager,
-            extra_contributors,
+            cargo_enabled,
         );
 
         // Subscribe before building the Run so we don't miss the initial
diff --git a/crates/turborepo-repository/src/cargo.rs b/crates/turborepo-repository/src/cargo.rs
index fa0075992aa9b..78e54a9edd0ff 100644
--- a/crates/turborepo-repository/src/cargo.rs
+++ b/crates/turborepo-repository/src/cargo.rs
@@ -1297,12 +1297,12 @@ impl PruneDomain for CargoPruneKnowledge {
 /// The Cargo repository contributor. Registered during graph construction when
 /// `futureFlags.experimentalCargoWorkspaces` is enabled and the repository
 /// root contains a `Cargo.toml`.
-pub struct CargoContributor {
+pub(crate) struct CargoContributor {
     repo_root: AbsoluteSystemPathBuf,
 }
 
 impl CargoContributor {
-    pub fn new(repo_root: AbsoluteSystemPathBuf) -> Arc<Self> {
+    pub(crate) fn new(repo_root: AbsoluteSystemPathBuf) -> Arc<Self> {
         Arc::new(Self { repo_root })
     }
 }
diff --git a/crates/turborepo-repository/src/package_graph/builder.rs b/crates/turborepo-repository/src/package_graph/builder.rs
index 65f48409d941e..31f0a6c03dbda 100644
--- a/crates/turborepo-repository/src/package_graph/builder.rs
+++ b/crates/turborepo-repository/src/package_graph/builder.rs
@@ -300,6 +300,12 @@ impl<'a, P> PackageGraphBuilder<'a, P> {
         self
     }
 
+    /// Enable Cargo repository contribution for this graph generation.
+    pub fn with_cargo(self) -> Self {
+        let repo_root = self.repo_root.to_owned();
+        self.with_contributor(crate::cargo::CargoContributor::new(repo_root))
+    }
+
     /// Set the package discovery strategy to use. Note that whatever strategy
     /// selected here will be wrapped in a `CachingPackageDiscovery` to
     /// prevent unnecessary work during building.
diff --git a/crates/turborepo-repository/src/package_graph/mod.rs b/crates/turborepo-repository/src/package_graph/mod.rs
index 2a5daf66be2a2..7eab50f47cc72 100644
--- a/crates/turborepo-repository/src/package_graph/mod.rs
+++ b/crates/turborepo-repository/src/package_graph/mod.rs
@@ -2840,7 +2840,7 @@ version = "0.1.0"
                 map
             }))
             .with_lockfile(Some(Box::new(MockLockfile {})))
-            .with_contributor(crate::cargo::CargoContributor::new(root.clone()))
+            .with_cargo()
             .build()
             .await
             .unwrap();
@@ -3044,7 +3044,7 @@ version = "0.1.0"
         write_cargo_workspace_fixture(&root);
 
         let mut pkg_graph = PackageGraph::builder_optional(&root, None)
-            .with_contributor(crate::cargo::CargoContributor::new(root.clone()))
+            .with_cargo()
             .build()
             .await
             .unwrap();
@@ -3287,7 +3287,7 @@ version = "0.1.0"
             map
         }))
         .with_lockfile(Some(Box::new(MockLockfile {})))
-        .with_contributor(crate::cargo::CargoContributor::new(root.clone()))
+        .with_cargo()
         .build()
         .await;
 
diff --git a/crates/turborepo-run-cache/src/lib.rs b/crates/turborepo-run-cache/src/lib.rs
index 089c8e32db2c2..d80550303d7cf 100644
--- a/crates/turborepo-run-cache/src/lib.rs
+++ b/crates/turborepo-run-cache/src/lib.rs
@@ -957,7 +957,6 @@ mod test {
     use turborepo_cache::{AsyncCache, CacheActions, CacheConfig, CacheOpts, LazyScmState};
     use turborepo_log::{LogSink, Logger, OutputChannel, grouping::GroupingLayer};
     use turborepo_repository::{
-        cargo::CargoContributor,
         package_graph::{PackageGraph, PackageName},
         package_json::PackageJson,
     };
@@ -1038,7 +1037,7 @@ mod test {
             )
             .unwrap();
         PackageGraph::builder_optional(repo_root, None)
-            .with_contributor(CargoContributor::new(repo_root.clone()))
+            .with_cargo()
             .build()
             .await
             .unwrap()
diff --git a/crates/turborepo-task-hash/src/lib.rs b/crates/turborepo-task-hash/src/lib.rs
index 3e3c87d5c25ca..6739be138b4d8 100644
--- a/crates/turborepo-task-hash/src/lib.rs
+++ b/crates/turborepo-task-hash/src/lib.rs
@@ -1078,7 +1078,6 @@ mod test {
     use tempfile::tempdir;
     use turbopath::AbsoluteSystemPathBuf;
     use turborepo_repository::{
-        cargo::CargoContributor,
         package_graph::{PackageGraph, PackageTaskContextKind},
         package_json::PackageJson,
     };
@@ -1173,7 +1172,7 @@ mod test {
             .unwrap();
 
         PackageGraph::builder_optional(repo_root, None)
-            .with_contributor(CargoContributor::new(repo_root.clone()))
+            .with_cargo()
             .with_closure_hasher(Arc::new(hash_sorted_closures))
             .build()
             .await
diff --git a/crates/turborepo/ARCHITECTURE.md b/crates/turborepo/ARCHITECTURE.md
index ef4654aabeddc..13cf34998f983 100644
--- a/crates/turborepo/ARCHITECTURE.md
+++ b/crates/turborepo/ARCHITECTURE.md
@@ -304,6 +304,11 @@ JavaScript is the first production producer. Machinery that predates the
 abstraction (package-manager resolution for dependency splitting and the JS
 lockfile closure phase) remains documented debt.
 
+Production callers enable Cargo through `PackageGraphBuilder::with_cargo`
+rather than constructing or retaining contributor objects. Run, watch, daemon,
+prune, query, hashing, and cache paths carry only the feature decision; each
+graph generation creates and drops its own Cargo contributor.
+
 Contract-derived I/O receives the same task-scoped arguments as execution plus
 a narrow, platform-aware startup-environment projection keyed by toolchain.
 Dependency tasks do not inherit arguments for a different requested task, each