diff --git a/crates/turborepo-lib/src/query/external_package.rs b/crates/turborepo-lib/src/query/external_package.rs
index f4cd438a45a86..05d7af00cc20a 100644
--- a/crates/turborepo-lib/src/query/external_package.rs
+++ b/crates/turborepo-lib/src/query/external_package.rs
@@ -2,6 +2,7 @@ use std::sync::Arc;
 
 use async_graphql::Object;
 
+use super::{package::Package, Array, Error};
 use crate::run::Run;
 
 #[derive(Clone)]
@@ -30,4 +31,20 @@ impl ExternalPackage {
     async fn name(&self) -> String {
         self.human_name().to_string()
     }
+
+    async fn internal_dependants(&self) -> Result<Array<Package>, Error> {
+        let Some(names) = self
+            .run
+            .pkg_dep_graph()
+            .internal_dependencies_for_external_dependency(&self.package)
+        else {
+            return Ok(Array::from(Vec::new()));
+        };
+        let mut packages = names
+            .iter()
+            .map(|name| Package::new(self.run.clone(), name.as_package_name().clone()))
+            .collect::<Result<Array<_>, Error>>()?;
+        packages.sort_by(|a, b| a.get_name().cmp(b.get_name()));
+        Ok(packages)
+    }
 }
diff --git a/crates/turborepo-lib/src/query/mod.rs b/crates/turborepo-lib/src/query/mod.rs
index 34bdf06103037..a45ed9efd3aa3 100644
--- a/crates/turborepo-lib/src/query/mod.rs
+++ b/crates/turborepo-lib/src/query/mod.rs
@@ -616,6 +616,18 @@ impl RepositoryQuery {
 
         Ok(packages)
     }
+
+    async fn external_dependencies(&self) -> Result<Array<ExternalPackage>, Error> {
+        let mut packages = self
+            .run
+            .pkg_dep_graph()
+            .external_to_internal()
+            .keys()
+            .map(|pkg| ExternalPackage::new(self.run.clone(), pkg.clone()))
+            .collect::<Array<_>>();
+        packages.sort_by_key(|pkg| pkg.human_name());
+        Ok(packages)
+    }
 }
 
 pub async fn graphiql() -> impl IntoResponse {
diff --git a/crates/turborepo-repository/src/package_graph/builder.rs b/crates/turborepo-repository/src/package_graph/builder.rs
index 5be2c2945a8b9..d18b7c160bbc6 100644
--- a/crates/turborepo-repository/src/package_graph/builder.rs
+++ b/crates/turborepo-repository/src/package_graph/builder.rs
@@ -341,6 +341,7 @@ impl<'a, T: PackageDiscovery> BuildState<'a, ResolvedPackageManager, T> {
             lockfile,
             package_manager,
             repo_root: repo_root.to_owned(),
+            external_to_internal: std::sync::OnceLock::new(),
         })
     }
 }
@@ -539,6 +540,7 @@ impl<T: PackageDiscovery> BuildState<'_, ResolvedLockfile, T> {
             package_manager,
             lockfile,
             repo_root: repo_root.to_owned(),
+            external_to_internal: std::sync::OnceLock::new(),
         })
     }
 }
diff --git a/crates/turborepo-repository/src/package_graph/mod.rs b/crates/turborepo-repository/src/package_graph/mod.rs
index 446332aef78dc..e49e603678ced 100644
--- a/crates/turborepo-repository/src/package_graph/mod.rs
+++ b/crates/turborepo-repository/src/package_graph/mod.rs
@@ -1,6 +1,7 @@
 use std::{
     collections::{BTreeMap, HashMap, HashSet},
     fmt,
+    sync::OnceLock,
 };
 
 use itertools::Itertools;
@@ -34,6 +35,7 @@ pub struct PackageGraph {
     package_manager: PackageManager,
     lockfile: Option<Box<dyn Lockfile>>,
     repo_root: AbsoluteSystemPathBuf,
+    external_to_internal: OnceLock<HashMap<turborepo_lockfiles::Package, HashSet<PackageNode>>>,
 }
 
 /// The WorkspacePackage.
@@ -555,6 +557,63 @@ impl PackageGraph {
         }))
     }
 
+    pub fn internal_dependencies_for_external_dependency(
+        &self,
+        external_package: &turborepo_lockfiles::Package,
+    ) -> Option<&HashSet<PackageNode>> {
+        // In order to answer this once we have to calculate the info for every external
+        // package so we store the results
+        let map = self
+            .external_to_internal
+            .get_or_init(|| self.external_to_internal());
+        map.get(external_package)
+    }
+
+    // Gotta come up with a better name
+    pub fn external_to_internal(
+        &self,
+    ) -> HashMap<turborepo_lockfiles::Package, HashSet<PackageNode>> {
+        // TODO: provide size hint from Lockfile trait
+        let mut map: HashMap<turborepo_lockfiles::Package, HashSet<PackageNode>> = HashMap::new();
+        // First find which packages directly depend on each external package
+        for (pkg, info) in self.packages.iter() {
+            for dep in info.transitive_dependencies.as_ref().into_iter().flatten() {
+                let rdeps = map.entry(dep.clone()).or_default();
+                rdeps.insert(PackageNode::Workspace(pkg.clone()));
+            }
+        }
+        // Now trace through all ancestors of the direct dependants
+        let root_internal_dependencies = self
+            .root_internal_dependencies()
+            .into_iter()
+            .cloned()
+            .collect::<HashSet<_>>();
+        let root_external_dependencies =
+            self.transitive_external_dependencies(Some(&PackageName::Root));
+        for (external_pkg, rdeps) in map.iter_mut() {
+            // If one of the reverse dependencies of this external package is a root
+            // dependency, everything depends on this
+            if root_external_dependencies.contains(external_pkg)
+                || !root_internal_dependencies.is_disjoint(rdeps)
+            {
+                rdeps.extend(self.graph.node_weights().cloned());
+            } else {
+                let transitive_rdeps = turborepo_graph_utils::transitive_closure(
+                    &self.graph,
+                    rdeps.iter().map(|node| {
+                        *self
+                            .node_lookup
+                            .get(node)
+                            .expect("all nodes should have an index")
+                    }),
+                    petgraph::Direction::Incoming,
+                );
+                rdeps.extend(transitive_rdeps.into_iter().cloned());
+            }
+        }
+        map
+    }
+
     // Returns a map of package name and version for external dependencies
     #[allow(dead_code)]
     fn external_dependencies(