diff --git a/Cargo.lock b/Cargo.lock
index 0603214c9..9c5bb0528 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -5450,7 +5450,6 @@ dependencies = [
  "uv-static",
  "uv-types",
  "uv-warnings",
- "uv-workspace",
  "walkdir",
 ]
 
diff --git a/crates/uv-bench/benches/uv.rs b/crates/uv-bench/benches/uv.rs
index df19354f6..b1958db90 100644
--- a/crates/uv-bench/benches/uv.rs
+++ b/crates/uv-bench/benches/uv.rs
@@ -91,7 +91,9 @@ mod resolver {
     };
     use uv_dispatch::{BuildDispatch, SharedState};
     use uv_distribution::DistributionDatabase;
-    use uv_distribution_types::{DependencyMetadata, IndexLocations, RequiresPython};
+    use uv_distribution_types::{
+        DependencyMetadata, ExtraBuildRequires, IndexLocations, RequiresPython,
+    };
     use uv_install_wheel::LinkMode;
     use uv_pep440::Version;
     use uv_pep508::{MarkerEnvironment, MarkerEnvironmentBuilder};
@@ -141,7 +143,7 @@ mod resolver {
         universal: bool,
     ) -> Result<ResolverOutput> {
         let build_isolation = BuildIsolation::default();
-        let extra_build_requires = uv_distribution::ExtraBuildRequires::default();
+        let extra_build_requires = ExtraBuildRequires::default();
         let build_options = BuildOptions::default();
         let concurrency = Concurrency::default();
         let config_settings = ConfigSettings::default();
diff --git a/crates/uv-build-frontend/src/lib.rs b/crates/uv-build-frontend/src/lib.rs
index 58cf441ab..cfa6a5f9e 100644
--- a/crates/uv-build-frontend/src/lib.rs
+++ b/crates/uv-build-frontend/src/lib.rs
@@ -32,7 +32,7 @@ use uv_cache_key::cache_digest;
 use uv_configuration::Preview;
 use uv_configuration::{BuildKind, BuildOutput, ConfigSettings, SourceStrategy};
 use uv_distribution::BuildRequires;
-use uv_distribution_types::{IndexLocations, Requirement, Resolution};
+use uv_distribution_types::{ExtraBuildRequires, IndexLocations, Requirement, Resolution};
 use uv_fs::LockedFile;
 use uv_fs::{PythonExt, Simplified};
 use uv_pep440::Version;
@@ -43,7 +43,6 @@ use uv_static::EnvVars;
 use uv_types::{AnyErrorBuild, BuildContext, BuildIsolation, BuildStack, SourceBuildTrait};
 use uv_warnings::warn_user_once;
 use uv_workspace::WorkspaceCache;
-use uv_workspace::pyproject::ExtraBuildDependencies;
 
 pub use crate::error::{Error, MissingHeaderCause};
 
@@ -283,7 +282,7 @@ impl SourceBuild {
         workspace_cache: &WorkspaceCache,
         config_settings: ConfigSettings,
         build_isolation: BuildIsolation<'_>,
-        extra_build_dependencies: &ExtraBuildDependencies,
+        extra_build_requires: &ExtraBuildRequires,
         build_stack: &BuildStack,
         build_kind: BuildKind,
         mut environment_variables: FxHashMap<OsString, OsString>,
@@ -326,10 +325,9 @@ impl SourceBuild {
 
         let extra_build_dependencies: Vec<Requirement> = package_name
             .as_ref()
-            .and_then(|name| extra_build_dependencies.get(name).cloned())
+            .and_then(|name| extra_build_requires.get(name).cloned())
             .unwrap_or_default()
             .into_iter()
-            .map(Requirement::from)
             .collect();
 
         // Create a virtual environment, or install into the shared environment if requested.
diff --git a/crates/uv-dispatch/src/lib.rs b/crates/uv-dispatch/src/lib.rs
index 0205ca969..e381c895e 100644
--- a/crates/uv-dispatch/src/lib.rs
+++ b/crates/uv-dispatch/src/lib.rs
@@ -22,11 +22,11 @@ use uv_configuration::{
 };
 use uv_configuration::{BuildOutput, Concurrency};
 use uv_distribution::DistributionDatabase;
-use uv_distribution::ExtraBuildRequires;
 use uv_distribution_filename::DistFilename;
 use uv_distribution_types::{
-    CachedDist, DependencyMetadata, Identifier, IndexCapabilities, IndexLocations,
-    IsBuildBackendError, Name, Requirement, Resolution, SourceDist, VersionOrUrlRef,
+    CachedDist, DependencyMetadata, ExtraBuildRequires, Identifier, IndexCapabilities,
+    IndexLocations, IsBuildBackendError, Name, Requirement, Resolution, SourceDist,
+    VersionOrUrlRef,
 };
 use uv_git::GitResolver;
 use uv_installer::{Installer, Plan, Planner, Preparer, SitePackages};
@@ -223,8 +223,8 @@ impl BuildContext for BuildDispatch<'_> {
         &self.workspace_cache
     }
 
-    fn extra_build_dependencies(&self) -> &uv_workspace::pyproject::ExtraBuildDependencies {
-        &self.extra_build_requires.extra_build_dependencies
+    fn extra_build_requires(&self) -> &ExtraBuildRequires {
+        self.extra_build_requires
     }
 
     async fn resolve<'data>(
@@ -311,7 +311,7 @@ impl BuildContext for BuildDispatch<'_> {
             self.index_locations,
             self.config_settings,
             self.config_settings_package,
-            self.extra_build_dependencies(),
+            self.extra_build_requires(),
             self.cache(),
             venv,
             tags,
@@ -461,7 +461,7 @@ impl BuildContext for BuildDispatch<'_> {
             self.workspace_cache(),
             config_settings,
             self.build_isolation,
-            self.extra_build_dependencies(),
+            self.extra_build_requires(),
             &build_stack,
             build_kind,
             self.build_extra_env_vars.clone(),
diff --git a/crates/uv-distribution-filename/src/extension.rs b/crates/uv-distribution-filename/src/extension.rs
index 747afc41b..233dfa9a1 100644
--- a/crates/uv-distribution-filename/src/extension.rs
+++ b/crates/uv-distribution-filename/src/extension.rs
@@ -55,6 +55,14 @@ impl DistExtension {
                 .map_err(|_| ExtensionError::Dist),
         }
     }
+
+    /// Return the name for the extension.
+    pub fn name(&self) -> &'static str {
+        match self {
+            Self::Wheel => "whl",
+            Self::Source(ext) => ext.name(),
+        }
+    }
 }
 
 impl SourceDistExtension {
diff --git a/crates/uv-distribution-types/src/build_requires.rs b/crates/uv-distribution-types/src/build_requires.rs
new file mode 100644
index 000000000..2ec1a164e
--- /dev/null
+++ b/crates/uv-distribution-types/src/build_requires.rs
@@ -0,0 +1,38 @@
+use std::collections::BTreeMap;
+
+use uv_normalize::PackageName;
+
+use crate::Requirement;
+
+/// Lowered extra build dependencies with source resolution applied.
+#[derive(Debug, Clone, Default)]
+pub struct ExtraBuildRequires(BTreeMap<PackageName, Vec<Requirement>>);
+
+impl std::ops::Deref for ExtraBuildRequires {
+    type Target = BTreeMap<PackageName, Vec<Requirement>>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl std::ops::DerefMut for ExtraBuildRequires {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+impl IntoIterator for ExtraBuildRequires {
+    type Item = (PackageName, Vec<Requirement>);
+    type IntoIter = std::collections::btree_map::IntoIter<PackageName, Vec<Requirement>>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.into_iter()
+    }
+}
+
+impl FromIterator<(PackageName, Vec<Requirement>)> for ExtraBuildRequires {
+    fn from_iter<T: IntoIterator<Item = (PackageName, Vec<Requirement>)>>(iter: T) -> Self {
+        Self(iter.into_iter().collect())
+    }
+}
diff --git a/crates/uv-distribution-types/src/lib.rs b/crates/uv-distribution-types/src/lib.rs
index 0b25669b0..98cea2582 100644
--- a/crates/uv-distribution-types/src/lib.rs
+++ b/crates/uv-distribution-types/src/lib.rs
@@ -54,6 +54,7 @@ use uv_redacted::DisplaySafeUrl;
 
 pub use crate::annotation::*;
 pub use crate::any::*;
+pub use crate::build_requires::*;
 pub use crate::buildable::*;
 pub use crate::cached::*;
 pub use crate::dependency_metadata::*;
@@ -82,6 +83,7 @@ pub use crate::traits::*;
 
 mod annotation;
 mod any;
+mod build_requires;
 mod buildable;
 mod cached;
 mod dependency_metadata;
diff --git a/crates/uv-distribution-types/src/requirement.rs b/crates/uv-distribution-types/src/requirement.rs
index 104cf396c..49507aadf 100644
--- a/crates/uv-distribution-types/src/requirement.rs
+++ b/crates/uv-distribution-types/src/requirement.rs
@@ -4,7 +4,7 @@ use std::path::Path;
 use std::str::FromStr;
 
 use thiserror::Error;
-
+use uv_cache_key::{CacheKey, CacheKeyHasher};
 use uv_distribution_filename::DistExtension;
 use uv_fs::{CWD, PortablePath, PortablePathBuf, relative_to};
 use uv_git_types::{GitOid, GitReference, GitUrl, GitUrlParseError, OidParseError};
@@ -365,6 +365,107 @@ impl Display for Requirement {
     }
 }
 
+impl CacheKey for Requirement {
+    fn cache_key(&self, state: &mut CacheKeyHasher) {
+        self.name.as_str().cache_key(state);
+
+        self.groups.len().cache_key(state);
+        for group in &self.groups {
+            group.as_str().cache_key(state);
+        }
+
+        self.extras.len().cache_key(state);
+        for extra in &self.extras {
+            extra.as_str().cache_key(state);
+        }
+
+        if let Some(marker) = self.marker.contents() {
+            1u8.cache_key(state);
+            marker.to_string().cache_key(state);
+        } else {
+            0u8.cache_key(state);
+        }
+
+        match &self.source {
+            RequirementSource::Registry {
+                specifier,
+                index,
+                conflict: _,
+            } => {
+                0u8.cache_key(state);
+                specifier.len().cache_key(state);
+                for spec in specifier.iter() {
+                    spec.operator().as_str().cache_key(state);
+                    spec.version().cache_key(state);
+                }
+                if let Some(index) = index {
+                    1u8.cache_key(state);
+                    index.url.cache_key(state);
+                } else {
+                    0u8.cache_key(state);
+                }
+                // `conflict` is intentionally omitted
+            }
+            RequirementSource::Url {
+                location,
+                subdirectory,
+                ext,
+                url,
+            } => {
+                1u8.cache_key(state);
+                location.cache_key(state);
+                if let Some(subdirectory) = subdirectory {
+                    1u8.cache_key(state);
+                    subdirectory.display().to_string().cache_key(state);
+                } else {
+                    0u8.cache_key(state);
+                }
+                ext.name().cache_key(state);
+                url.cache_key(state);
+            }
+            RequirementSource::Git {
+                git,
+                subdirectory,
+                url,
+            } => {
+                2u8.cache_key(state);
+                git.to_string().cache_key(state);
+                if let Some(subdirectory) = subdirectory {
+                    1u8.cache_key(state);
+                    subdirectory.display().to_string().cache_key(state);
+                } else {
+                    0u8.cache_key(state);
+                }
+                url.cache_key(state);
+            }
+            RequirementSource::Path {
+                install_path,
+                ext,
+                url,
+            } => {
+                3u8.cache_key(state);
+                install_path.cache_key(state);
+                ext.name().cache_key(state);
+                url.cache_key(state);
+            }
+            RequirementSource::Directory {
+                install_path,
+                editable,
+                r#virtual,
+                url,
+            } => {
+                4u8.cache_key(state);
+                install_path.cache_key(state);
+                editable.cache_key(state);
+                r#virtual.cache_key(state);
+                url.cache_key(state);
+            }
+        }
+
+        // `origin` is intentionally omitted
+    }
+}
+
 /// The different locations with can install a distribution from: Version specifier (from an index),
 /// HTTP(S) URL, git repository, and path.
 ///
diff --git a/crates/uv-distribution/src/index/built_wheel_index.rs b/crates/uv-distribution/src/index/built_wheel_index.rs
index d877c2509..321199772 100644
--- a/crates/uv-distribution/src/index/built_wheel_index.rs
+++ b/crates/uv-distribution/src/index/built_wheel_index.rs
@@ -5,12 +5,12 @@ use uv_cache_info::CacheInfo;
 use uv_cache_key::cache_digest;
 use uv_configuration::{ConfigSettings, PackageConfigSettings};
 use uv_distribution_types::{
-    DirectUrlSourceDist, DirectorySourceDist, GitSourceDist, Hashed, PathSourceDist,
+    DirectUrlSourceDist, DirectorySourceDist, ExtraBuildRequires, GitSourceDist, Hashed,
+    PathSourceDist, Requirement,
 };
 use uv_normalize::PackageName;
 use uv_platform_tags::Tags;
 use uv_types::HashStrategy;
-use uv_workspace::pyproject::ExtraBuildDependencies;
 
 use crate::Error;
 use crate::index::cached_wheel::CachedWheel;
@@ -24,7 +24,7 @@ pub struct BuiltWheelIndex<'a> {
     hasher: &'a HashStrategy,
     config_settings: &'a ConfigSettings,
     config_settings_package: &'a PackageConfigSettings,
-    extra_build_dependencies: &'a ExtraBuildDependencies,
+    extra_build_requires: &'a ExtraBuildRequires,
 }
 
 impl<'a> BuiltWheelIndex<'a> {
@@ -35,7 +35,7 @@ impl<'a> BuiltWheelIndex<'a> {
         hasher: &'a HashStrategy,
         config_settings: &'a ConfigSettings,
         config_settings_package: &'a PackageConfigSettings,
-        extra_build_dependencies: &'a ExtraBuildDependencies,
+        extra_build_requires: &'a ExtraBuildRequires,
     ) -> Self {
         Self {
             cache,
@@ -43,7 +43,7 @@ impl<'a> BuiltWheelIndex<'a> {
             hasher,
             config_settings,
             config_settings_package,
-            extra_build_dependencies,
+            extra_build_requires,
         }
     }
 
@@ -74,7 +74,7 @@ impl<'a> BuiltWheelIndex<'a> {
 
         // If there are build settings, we need to scope to a cache shard.
         let config_settings = self.config_settings_for(&source_dist.name);
-        let extra_build_deps = self.extra_build_dependencies_for(&source_dist.name);
+        let extra_build_deps = self.extra_build_requires_for(&source_dist.name);
         let cache_shard = if config_settings.is_empty() && extra_build_deps.is_empty() {
             cache_shard
         } else {
@@ -113,7 +113,7 @@ impl<'a> BuiltWheelIndex<'a> {
 
         // If there are build settings, we need to scope to a cache shard.
         let config_settings = self.config_settings_for(&source_dist.name);
-        let extra_build_deps = self.extra_build_dependencies_for(&source_dist.name);
+        let extra_build_deps = self.extra_build_requires_for(&source_dist.name);
         let cache_shard = if config_settings.is_empty() && extra_build_deps.is_empty() {
             cache_shard
         } else {
@@ -163,7 +163,7 @@ impl<'a> BuiltWheelIndex<'a> {
 
         // If there are build settings, we need to scope to a cache shard.
         let config_settings = self.config_settings_for(&source_dist.name);
-        let extra_build_deps = self.extra_build_dependencies_for(&source_dist.name);
+        let extra_build_deps = self.extra_build_requires_for(&source_dist.name);
         let cache_shard = if config_settings.is_empty() && extra_build_deps.is_empty() {
             cache_shard
         } else {
@@ -191,7 +191,7 @@ impl<'a> BuiltWheelIndex<'a> {
 
         // If there are build settings, we need to scope to a cache shard.
         let config_settings = self.config_settings_for(&source_dist.name);
-        let extra_build_deps = self.extra_build_dependencies_for(&source_dist.name);
+        let extra_build_deps = self.extra_build_requires_for(&source_dist.name);
         let cache_shard = if config_settings.is_empty() && extra_build_deps.is_empty() {
             cache_shard
         } else {
@@ -268,11 +268,8 @@ impl<'a> BuiltWheelIndex<'a> {
     }
 
     /// Determine the extra build dependencies for the given package name.
-    fn extra_build_dependencies_for(
-        &self,
-        name: &PackageName,
-    ) -> &[uv_pep508::Requirement<uv_pypi_types::VerbatimParsedUrl>] {
-        self.extra_build_dependencies
+    fn extra_build_requires_for(&self, name: &PackageName) -> &[Requirement] {
+        self.extra_build_requires
             .get(name)
             .map(Vec::as_slice)
             .unwrap_or(&[])
diff --git a/crates/uv-distribution/src/lib.rs b/crates/uv-distribution/src/lib.rs
index 6371d58af..6ffb2d6d8 100644
--- a/crates/uv-distribution/src/lib.rs
+++ b/crates/uv-distribution/src/lib.rs
@@ -3,8 +3,9 @@ pub use download::LocalWheel;
 pub use error::Error;
 pub use index::{BuiltWheelIndex, RegistryWheelIndex};
 pub use metadata::{
-    ArchiveMetadata, BuildRequires, ExtraBuildRequires, FlatRequiresDist, LoweredRequirement,
-    LoweringError, Metadata, MetadataError, RequiresDist, SourcedDependencyGroups,
+    ArchiveMetadata, BuildRequires, FlatRequiresDist, LoweredExtraBuildDependencies,
+    LoweredRequirement, LoweringError, Metadata, MetadataError, RequiresDist,
+    SourcedDependencyGroups,
 };
 pub use reporter::Reporter;
 pub use source::prune;
diff --git a/crates/uv-distribution/src/metadata/build_requires.rs b/crates/uv-distribution/src/metadata/build_requires.rs
index 9aa14bd9e..3913d292c 100644
--- a/crates/uv-distribution/src/metadata/build_requires.rs
+++ b/crates/uv-distribution/src/metadata/build_requires.rs
@@ -2,9 +2,8 @@ use std::collections::BTreeMap;
 use std::path::Path;
 
 use uv_configuration::SourceStrategy;
-use uv_distribution_types::{IndexLocations, Requirement};
+use uv_distribution_types::{ExtraBuildRequires, IndexLocations, Requirement};
 use uv_normalize::PackageName;
-use uv_pypi_types::VerbatimParsedUrl;
 use uv_workspace::pyproject::{ExtraBuildDependencies, ToolUvSources};
 use uv_workspace::{
     DiscoveryOptions, MemberDiscovery, ProjectWorkspace, Workspace, WorkspaceCache,
@@ -205,14 +204,20 @@ impl BuildRequires {
     }
 }
 
-/// Lowered extra build dependencies with source resolution applied.
+/// Lowered extra build dependencies.
+///
+/// This is a wrapper around [`ExtraBuildRequires`] that provides methods to lower
+/// [`ExtraBuildDependencies`] from a workspace context or from already lowered dependencies.
 #[derive(Debug, Clone, Default)]
-pub struct ExtraBuildRequires {
-    pub extra_build_dependencies: ExtraBuildDependencies,
-}
+pub struct LoweredExtraBuildDependencies(ExtraBuildRequires);
 
-impl ExtraBuildRequires {
-    /// Lower extra build dependencies from a workspace, applying source resolution.
+impl LoweredExtraBuildDependencies {
+    /// Return the [`ExtraBuildRequires`] that this was lowered into.
+    pub fn into_inner(self) -> ExtraBuildRequires {
+        self.0
+    }
+
+    /// Create from a workspace, lowering the extra build dependencies.
     pub fn from_workspace(
         extra_build_dependencies: ExtraBuildDependencies,
         workspace: &Workspace,
@@ -241,9 +246,9 @@ impl ExtraBuildRequires {
                     .unwrap_or(&empty_sources);
 
                 // Lower each package's extra build dependencies
-                let mut result = ExtraBuildDependencies::default();
+                let mut build_requires = ExtraBuildRequires::default();
                 for (package_name, requirements) in extra_build_dependencies {
-                    let lowered: Vec<uv_pep508::Requirement<VerbatimParsedUrl>> = requirements
+                    let lowered: Vec<Requirement> = requirements
                         .into_iter()
                         .flat_map(|requirement| {
                             let requirement_name = requirement.name.clone();
@@ -263,7 +268,7 @@ impl ExtraBuildRequires {
                             )
                             .map(
                                 move |requirement| match requirement {
-                                    Ok(requirement) => Ok(requirement.into_inner().into()),
+                                    Ok(requirement) => Ok(requirement.into_inner()),
                                     Err(err) => Err(MetadataError::LoweringError(
                                         requirement_name.clone(),
                                         Box::new(err),
@@ -272,25 +277,41 @@ impl ExtraBuildRequires {
                             )
                         })
                         .collect::<Result<Vec<_>, _>>()?;
-                    result.insert(package_name, lowered);
+                    build_requires.insert(package_name, lowered);
                 }
-                Ok(Self {
-                    extra_build_dependencies: result,
-                })
-            }
-            SourceStrategy::Disabled => {
-                // Without source resolution, just return the dependencies as-is
-                Ok(Self {
-                    extra_build_dependencies,
-                })
+                Ok(Self(build_requires))
             }
+            SourceStrategy::Disabled => Ok(Self(
+                extra_build_dependencies
+                    .into_iter()
+                    .map(|(name, requirements)| {
+                        (
+                            name,
+                            requirements.into_iter().map(Requirement::from).collect(),
+                        )
+                    })
+                    .collect(),
+            )),
         }
     }
 
-    /// Create from pre-lowered dependencies (for non-workspace contexts).
-    pub fn from_lowered(extra_build_dependencies: ExtraBuildDependencies) -> Self {
-        Self {
-            extra_build_dependencies,
-        }
+    /// Create from lowered dependencies (for non-workspace contexts, like scripts).
+    pub fn from_lowered(extra_build_dependencies: ExtraBuildRequires) -> Self {
+        Self(extra_build_dependencies)
+    }
+
+    /// Create from unlowered dependencies (e.g., for contexts in the pip CLI).
+    pub fn from_non_lowered(extra_build_dependencies: ExtraBuildDependencies) -> Self {
+        Self(
+            extra_build_dependencies
+                .into_iter()
+                .map(|(name, requirements)| {
+                    (
+                        name,
+                        requirements.into_iter().map(Requirement::from).collect(),
+                    )
+                })
+                .collect(),
+        )
     }
 }
diff --git a/crates/uv-distribution/src/metadata/mod.rs b/crates/uv-distribution/src/metadata/mod.rs
index 3375f9fe2..5deb37c03 100644
--- a/crates/uv-distribution/src/metadata/mod.rs
+++ b/crates/uv-distribution/src/metadata/mod.rs
@@ -11,7 +11,7 @@ use uv_pypi_types::{HashDigests, ResolutionMetadata};
 use uv_workspace::dependency_groups::DependencyGroupError;
 use uv_workspace::{WorkspaceCache, WorkspaceError};
 
-pub use crate::metadata::build_requires::{BuildRequires, ExtraBuildRequires};
+pub use crate::metadata::build_requires::{BuildRequires, LoweredExtraBuildDependencies};
 pub use crate::metadata::dependency_groups::SourcedDependencyGroups;
 pub use crate::metadata::lowering::LoweredRequirement;
 pub use crate::metadata::lowering::LoweringError;
diff --git a/crates/uv-distribution/src/source/mod.rs b/crates/uv-distribution/src/source/mod.rs
index d516c6d0d..05d25be42 100644
--- a/crates/uv-distribution/src/source/mod.rs
+++ b/crates/uv-distribution/src/source/mod.rs
@@ -33,7 +33,7 @@ use uv_configuration::{BuildKind, BuildOutput, ConfigSettings, SourceStrategy};
 use uv_distribution_filename::{SourceDistExtension, WheelFilename};
 use uv_distribution_types::{
     BuildableSource, DirectorySourceUrl, GitSourceUrl, HashPolicy, Hashed, IndexUrl, PathSourceUrl,
-    SourceDist, SourceUrl,
+    Requirement, SourceDist, SourceUrl,
 };
 use uv_extract::hash::Hasher;
 use uv_fs::{rename_with_retry, write_atomic};
@@ -405,13 +405,10 @@ impl<'a, T: BuildContext> SourceDistributionBuilder<'a, T> {
     }
 
     /// Determine the extra build dependencies for the given package name.
-    fn extra_build_dependencies_for(
-        &self,
-        name: Option<&PackageName>,
-    ) -> &[uv_pep508::Requirement<uv_pypi_types::VerbatimParsedUrl>] {
+    fn extra_build_dependencies_for(&self, name: Option<&PackageName>) -> &[Requirement] {
         name.and_then(|name| {
             self.build_context
-                .extra_build_dependencies()
+                .extra_build_requires()
                 .get(name)
                 .map(Vec::as_slice)
         })
diff --git a/crates/uv-installer/Cargo.toml b/crates/uv-installer/Cargo.toml
index d0f43e770..a78dec23b 100644
--- a/crates/uv-installer/Cargo.toml
+++ b/crates/uv-installer/Cargo.toml
@@ -35,7 +35,6 @@ uv-redacted = { workspace = true }
 uv-static = { workspace = true }
 uv-types = { workspace = true }
 uv-warnings = { workspace = true }
-uv-workspace = { workspace = true }
 
 anyhow = { workspace = true }
 async-channel = { workspace = true }
diff --git a/crates/uv-installer/src/plan.rs b/crates/uv-installer/src/plan.rs
index ddabf3386..a604d8152 100644
--- a/crates/uv-installer/src/plan.rs
+++ b/crates/uv-installer/src/plan.rs
@@ -10,15 +10,14 @@ use uv_distribution::{
     BuiltWheelIndex, HttpArchivePointer, LocalArchivePointer, RegistryWheelIndex,
 };
 use uv_distribution_types::{
-    BuiltDist, CachedDirectUrlDist, CachedDist, Dist, Error, Hashed, IndexLocations, InstalledDist,
-    Name, RequirementSource, Resolution, ResolvedDist, SourceDist,
+    BuiltDist, CachedDirectUrlDist, CachedDist, Dist, Error, ExtraBuildRequires, Hashed,
+    IndexLocations, InstalledDist, Name, RequirementSource, Resolution, ResolvedDist, SourceDist,
 };
 use uv_fs::Simplified;
 use uv_platform_tags::Tags;
 use uv_pypi_types::VerbatimParsedUrl;
 use uv_python::PythonEnvironment;
 use uv_types::HashStrategy;
-use uv_workspace::pyproject::ExtraBuildDependencies;
 
 use crate::SitePackages;
 use crate::satisfies::RequirementSatisfaction;
@@ -55,7 +54,7 @@ impl<'a> Planner<'a> {
         index_locations: &IndexLocations,
         config_settings: &ConfigSettings,
         config_settings_package: &PackageConfigSettings,
-        extra_build_dependencies: &ExtraBuildDependencies,
+        extra_build_requires: &ExtraBuildRequires,
         cache: &Cache,
         venv: &PythonEnvironment,
         tags: &Tags,
@@ -69,7 +68,7 @@ impl<'a> Planner<'a> {
             hasher,
             config_settings,
             config_settings_package,
-            extra_build_dependencies,
+            extra_build_requires,
         );
 
         let mut cached = vec![];
diff --git a/crates/uv-normalize/src/group_name.rs b/crates/uv-normalize/src/group_name.rs
index e0a2b7c1f..e39044ad7 100644
--- a/crates/uv-normalize/src/group_name.rs
+++ b/crates/uv-normalize/src/group_name.rs
@@ -29,6 +29,11 @@ impl GroupName {
     pub fn from_owned(name: String) -> Result<Self, InvalidNameError> {
         validate_and_normalize_ref(&name).map(Self)
     }
+
+    /// Return the underlying group name as a string.
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
 }
 
 impl FromStr for GroupName {
diff --git a/crates/uv-types/src/traits.rs b/crates/uv-types/src/traits.rs
index 6966c850a..f6e51d929 100644
--- a/crates/uv-types/src/traits.rs
+++ b/crates/uv-types/src/traits.rs
@@ -12,14 +12,13 @@ use uv_configuration::{
 };
 use uv_distribution_filename::DistFilename;
 use uv_distribution_types::{
-    CachedDist, DependencyMetadata, DistributionId, IndexCapabilities, IndexLocations,
-    InstalledDist, IsBuildBackendError, Requirement, Resolution, SourceDist,
+    CachedDist, DependencyMetadata, DistributionId, ExtraBuildRequires, IndexCapabilities,
+    IndexLocations, InstalledDist, IsBuildBackendError, Requirement, Resolution, SourceDist,
 };
 use uv_git::GitResolver;
 use uv_pep508::PackageName;
 use uv_python::{Interpreter, PythonEnvironment};
 use uv_workspace::WorkspaceCache;
-use uv_workspace::pyproject::ExtraBuildDependencies;
 
 use crate::BuildArena;
 
@@ -104,8 +103,8 @@ pub trait BuildContext {
     /// Workspace discovery caching.
     fn workspace_cache(&self) -> &WorkspaceCache;
 
-    /// Get the extra build dependencies.
-    fn extra_build_dependencies(&self) -> &ExtraBuildDependencies;
+    /// Get the extra build requirements.
+    fn extra_build_requires(&self) -> &ExtraBuildRequires;
 
     /// Resolve the given requirements into a ready-to-install set of package versions.
     fn resolve<'a>(
diff --git a/crates/uv/src/commands/build_frontend.rs b/crates/uv/src/commands/build_frontend.rs
index 7ec57e1d6..baaba8b75 100644
--- a/crates/uv/src/commands/build_frontend.rs
+++ b/crates/uv/src/commands/build_frontend.rs
@@ -19,6 +19,7 @@ use uv_configuration::{
     PackageConfigSettings, Preview, SourceStrategy,
 };
 use uv_dispatch::{BuildDispatch, SharedState};
+use uv_distribution::LoweredExtraBuildDependencies;
 use uv_distribution_filename::{
     DistFilename, SourceDistExtension, SourceDistFilename, WheelFilename,
 };
@@ -563,9 +564,11 @@ async fn build_package(
     let state = SharedState::default();
     let workspace_cache = WorkspaceCache::default();
 
-    // Create a build dispatch.
     let extra_build_requires =
-        uv_distribution::ExtraBuildRequires::from_lowered(extra_build_dependencies.clone());
+        LoweredExtraBuildDependencies::from_non_lowered(extra_build_dependencies.clone())
+            .into_inner();
+
+    // Create a build dispatch.
     let build_dispatch = BuildDispatch::new(
         &client,
         cache,
diff --git a/crates/uv/src/commands/pip/compile.rs b/crates/uv/src/commands/pip/compile.rs
index 26ae9f11c..48bba2532 100644
--- a/crates/uv/src/commands/pip/compile.rs
+++ b/crates/uv/src/commands/pip/compile.rs
@@ -19,6 +19,7 @@ use uv_configuration::{
 };
 use uv_configuration::{KeyringProviderType, TargetTriple};
 use uv_dispatch::{BuildDispatch, SharedState};
+use uv_distribution::LoweredExtraBuildDependencies;
 use uv_distribution_types::{
     DependencyMetadata, HashGeneration, Index, IndexLocations, NameRequirementSpecification,
     Origin, Requirement, RequiresPython, UnresolvedRequirementSpecification, Verbatim,
@@ -480,8 +481,12 @@ pub(crate) async fn pip_compile(
             .map(|constraint| constraint.requirement.clone()),
     );
 
+    // Lower the extra build dependencies, if any.
     let extra_build_requires =
-        uv_distribution::ExtraBuildRequires::from_lowered(extra_build_dependencies.clone());
+        LoweredExtraBuildDependencies::from_non_lowered(extra_build_dependencies.clone())
+            .into_inner();
+
+    // Create a build dispatch.
     let build_dispatch = BuildDispatch::new(
         &client,
         &cache,
diff --git a/crates/uv/src/commands/pip/install.rs b/crates/uv/src/commands/pip/install.rs
index 6a9ccbd9c..e5b69dbe9 100644
--- a/crates/uv/src/commands/pip/install.rs
+++ b/crates/uv/src/commands/pip/install.rs
@@ -15,6 +15,7 @@ use uv_configuration::{
 };
 use uv_configuration::{KeyringProviderType, TargetTriple};
 use uv_dispatch::{BuildDispatch, SharedState};
+use uv_distribution::LoweredExtraBuildDependencies;
 use uv_distribution_types::{
     DependencyMetadata, Index, IndexLocations, NameRequirementSpecification, Origin, Requirement,
     Resolution, UnresolvedRequirementSpecification,
@@ -423,9 +424,12 @@ pub(crate) async fn pip_install(
     // Initialize any shared state.
     let state = SharedState::default();
 
-    // Create a build dispatch.
+    // Lower the extra build dependencies, if any.
     let extra_build_requires =
-        uv_distribution::ExtraBuildRequires::from_lowered(extra_build_dependencies.clone());
+        LoweredExtraBuildDependencies::from_non_lowered(extra_build_dependencies.clone())
+            .into_inner();
+
+    // Create a build dispatch.
     let build_dispatch = BuildDispatch::new(
         &client,
         &cache,
diff --git a/crates/uv/src/commands/pip/operations.rs b/crates/uv/src/commands/pip/operations.rs
index f3ddcf671..680eca490 100644
--- a/crates/uv/src/commands/pip/operations.rs
+++ b/crates/uv/src/commands/pip/operations.rs
@@ -464,7 +464,7 @@ pub(crate) async fn install(
             build_dispatch.locations(),
             build_dispatch.config_settings(),
             build_dispatch.config_settings_package(),
-            build_dispatch.extra_build_dependencies(),
+            build_dispatch.extra_build_requires(),
             cache,
             venv,
             tags,
diff --git a/crates/uv/src/commands/pip/sync.rs b/crates/uv/src/commands/pip/sync.rs
index 70451faad..411d1a0ba 100644
--- a/crates/uv/src/commands/pip/sync.rs
+++ b/crates/uv/src/commands/pip/sync.rs
@@ -14,6 +14,7 @@ use uv_configuration::{
 };
 use uv_configuration::{KeyringProviderType, TargetTriple};
 use uv_dispatch::{BuildDispatch, SharedState};
+use uv_distribution::LoweredExtraBuildDependencies;
 use uv_distribution_types::{DependencyMetadata, Index, IndexLocations, Origin, Resolution};
 use uv_fs::Simplified;
 use uv_install_wheel::LinkMode;
@@ -358,9 +359,12 @@ pub(crate) async fn pip_sync(
     // Initialize any shared state.
     let state = SharedState::default();
 
-    // Create a build dispatch.
+    // Lower the extra build dependencies, if any.
     let extra_build_requires =
-        uv_distribution::ExtraBuildRequires::from_lowered(extra_build_dependencies.clone());
+        LoweredExtraBuildDependencies::from_non_lowered(extra_build_dependencies.clone())
+            .into_inner();
+
+    // Create a build dispatch.
     let build_dispatch = BuildDispatch::new(
         &client,
         &cache,
diff --git a/crates/uv/src/commands/project/add.rs b/crates/uv/src/commands/project/add.rs
index dbbc5a77b..fce4cce6a 100644
--- a/crates/uv/src/commands/project/add.rs
+++ b/crates/uv/src/commands/project/add.rs
@@ -22,7 +22,7 @@ use uv_configuration::{
     PreviewFeatures, SourceStrategy,
 };
 use uv_dispatch::BuildDispatch;
-use uv_distribution::DistributionDatabase;
+use uv_distribution::{DistributionDatabase, LoweredExtraBuildDependencies};
 use uv_distribution_types::{
     Index, IndexName, IndexUrl, IndexUrls, NameRequirementSpecification, Requirement,
     RequirementSource, UnresolvedRequirement, VersionId,
@@ -436,19 +436,22 @@ pub(crate) async fn add(
                 FlatIndex::from_entries(entries, None, &hasher, &settings.resolver.build_options)
             };
 
-            // Create a build dispatch.
+            // Lower the extra build dependencies, if any.
             let extra_build_requires = if let AddTarget::Project(project, _) = &target {
-                uv_distribution::ExtraBuildRequires::from_workspace(
+                LoweredExtraBuildDependencies::from_workspace(
                     settings.resolver.extra_build_dependencies.clone(),
                     project.workspace(),
                     &settings.resolver.index_locations,
                     settings.resolver.sources,
                 )?
             } else {
-                uv_distribution::ExtraBuildRequires::from_lowered(
+                LoweredExtraBuildDependencies::from_non_lowered(
                     settings.resolver.extra_build_dependencies.clone(),
                 )
-            };
+            }
+            .into_inner();
+
+            // Create a build dispatch.
             let build_dispatch = BuildDispatch::new(
                 &client,
                 cache,
diff --git a/crates/uv/src/commands/project/lock.rs b/crates/uv/src/commands/project/lock.rs
index ad45d126b..fa71b5f62 100644
--- a/crates/uv/src/commands/project/lock.rs
+++ b/crates/uv/src/commands/project/lock.rs
@@ -16,7 +16,7 @@ use uv_configuration::{
     PreviewFeatures, Reinstall, Upgrade,
 };
 use uv_dispatch::BuildDispatch;
-use uv_distribution::DistributionDatabase;
+use uv_distribution::{DistributionDatabase, LoweredExtraBuildDependencies};
 use uv_distribution_types::{
     DependencyMetadata, HashGeneration, Index, IndexLocations, NameRequirementSpecification,
     Requirement, RequiresPython, UnresolvedRequirementSpecification,
@@ -673,9 +673,9 @@ async fn do_lock(
         FlatIndex::from_entries(entries, None, &hasher, build_options)
     };
 
-    // Create a build dispatch.
+    // Lower the extra build dependencies.
     let extra_build_requires = match &target {
-        LockTarget::Workspace(workspace) => uv_distribution::ExtraBuildRequires::from_workspace(
+        LockTarget::Workspace(workspace) => LoweredExtraBuildDependencies::from_workspace(
             extra_build_dependencies.clone(),
             workspace,
             index_locations,
@@ -685,7 +685,10 @@ async fn do_lock(
             // Try to get extra build dependencies from the script metadata
             script_extra_build_requires((*script).into(), settings)?
         }
-    };
+    }
+    .into_inner();
+
+    // Create a build dispatch.
     let build_dispatch = BuildDispatch::new(
         &client,
         cache,
diff --git a/crates/uv/src/commands/project/mod.rs b/crates/uv/src/commands/project/mod.rs
index 9458919c8..2c799dfe2 100644
--- a/crates/uv/src/commands/project/mod.rs
+++ b/crates/uv/src/commands/project/mod.rs
@@ -16,9 +16,9 @@ use uv_configuration::{
     PreviewFeatures, Reinstall, Upgrade,
 };
 use uv_dispatch::{BuildDispatch, SharedState};
-use uv_distribution::{DistributionDatabase, LoweredRequirement};
+use uv_distribution::{DistributionDatabase, LoweredExtraBuildDependencies, LoweredRequirement};
 use uv_distribution_types::{
-    Index, Requirement, RequiresPython, Resolution, UnresolvedRequirement,
+    ExtraBuildRequires, Index, Requirement, RequiresPython, Resolution, UnresolvedRequirement,
     UnresolvedRequirementSpecification,
 };
 use uv_fs::{CWD, LockedFile, Simplified};
@@ -46,7 +46,6 @@ use uv_types::{BuildIsolation, EmptyInstalledPackages, HashStrategy};
 use uv_virtualenv::remove_virtualenv;
 use uv_warnings::{warn_user, warn_user_once};
 use uv_workspace::dependency_groups::DependencyGroupError;
-use uv_workspace::pyproject::ExtraBuildDependencies;
 use uv_workspace::pyproject::PyProjectToml;
 use uv_workspace::{RequiresPythonSources, Workspace, WorkspaceCache};
 
@@ -1741,9 +1740,12 @@ pub(crate) async fn resolve_names(
     let build_constraints = Constraints::default();
     let build_hasher = HashStrategy::default();
 
-    // Create a build dispatch.
+    // Lower the extra build dependencies, if any.
     let extra_build_requires =
-        uv_distribution::ExtraBuildRequires::from_lowered(extra_build_dependencies.clone());
+        LoweredExtraBuildDependencies::from_non_lowered(extra_build_dependencies.clone())
+            .into_inner();
+
+    // Create a build dispatch.
     let build_dispatch = BuildDispatch::new(
         &client,
         cache,
@@ -1953,9 +1955,12 @@ pub(crate) async fn resolve_environment(
 
     let workspace_cache = WorkspaceCache::default();
 
-    // Create a build dispatch.
+    // Lower the extra build dependencies, if any.
     let extra_build_requires =
-        uv_distribution::ExtraBuildRequires::from_lowered(extra_build_dependencies.clone());
+        LoweredExtraBuildDependencies::from_non_lowered(extra_build_dependencies.clone())
+            .into_inner();
+
+    // Create a build dispatch.
     let resolve_dispatch = BuildDispatch::new(
         &client,
         cache,
@@ -2095,9 +2100,12 @@ pub(crate) async fn sync_environment(
         FlatIndex::from_entries(entries, Some(tags), &hasher, build_options)
     };
 
-    // Create a build dispatch.
+    // Lower the extra build dependencies, if any.
     let extra_build_requires =
-        uv_distribution::ExtraBuildRequires::from_lowered(extra_build_dependencies.clone());
+        LoweredExtraBuildDependencies::from_non_lowered(extra_build_dependencies.clone())
+            .into_inner();
+
+    // Create a build dispatch.
     let build_dispatch = BuildDispatch::new(
         &client,
         cache,
@@ -2174,7 +2182,7 @@ pub(crate) async fn update_environment(
     spec: RequirementsSpecification,
     modifications: Modifications,
     build_constraints: Constraints,
-    extra_build_requires: uv_distribution::ExtraBuildRequires,
+    extra_build_requires: ExtraBuildRequires,
     settings: &ResolverInstallerSettings,
     network_settings: &NetworkSettings,
     state: &SharedState,
@@ -2618,7 +2626,7 @@ pub(crate) fn script_specification(
 pub(crate) fn script_extra_build_requires(
     script: Pep723ItemRef<'_>,
     settings: &ResolverSettings,
-) -> Result<uv_distribution::ExtraBuildRequires, ProjectError> {
+) -> Result<LoweredExtraBuildDependencies, ProjectError> {
     let script_dir = script.directory()?;
     let script_indexes = script.indexes(settings.sources);
     let script_sources = script.sources(settings.sources);
@@ -2633,8 +2641,8 @@ pub(crate) fn script_extra_build_requires(
         .and_then(|uv| uv.extra_build_dependencies.as_ref())
         .unwrap_or(&empty);
 
-    // Lower the extra build dependencies
-    let mut extra_build_dependencies = ExtraBuildDependencies::default();
+    // Lower the extra build dependencies.
+    let mut extra_build_requires = ExtraBuildRequires::default();
     for (name, requirements) in script_extra_build_dependencies {
         let lowered_requirements: Vec<_> = requirements
             .iter()
@@ -2647,14 +2655,14 @@ pub(crate) fn script_extra_build_requires(
                     script_indexes,
                     &settings.index_locations,
                 )
-                .map_ok(|req| req.into_inner().into())
+                .map_ok(uv_distribution::LoweredRequirement::into_inner)
             })
             .collect::<Result<Vec<_>, _>>()?;
-        extra_build_dependencies.insert(name.clone(), lowered_requirements);
+        extra_build_requires.insert(name.clone(), lowered_requirements);
     }
 
-    Ok(uv_distribution::ExtraBuildRequires::from_lowered(
-        extra_build_dependencies,
+    Ok(LoweredExtraBuildDependencies::from_lowered(
+        extra_build_requires,
     ))
 }
 
diff --git a/crates/uv/src/commands/project/run.rs b/crates/uv/src/commands/project/run.rs
index 594a5c28a..9cbfd16fb 100644
--- a/crates/uv/src/commands/project/run.rs
+++ b/crates/uv/src/commands/project/run.rs
@@ -360,7 +360,7 @@ hint: If you are running a script with `{}` in the shebang, you may need to incl
             // Install the script requirements, if necessary. Otherwise, use an isolated environment.
             if let Some(spec) = script_specification((&script).into(), &settings.resolver)? {
                 let script_extra_build_requires =
-                    script_extra_build_requires((&script).into(), &settings.resolver)?;
+                    script_extra_build_requires((&script).into(), &settings.resolver)?.into_inner();
                 let environment = ScriptEnvironment::get_or_init(
                     (&script).into(),
                     python.as_deref().map(PythonRequest::parse),
diff --git a/crates/uv/src/commands/project/sync.rs b/crates/uv/src/commands/project/sync.rs
index 88cf221b6..3d7a1011a 100644
--- a/crates/uv/src/commands/project/sync.rs
+++ b/crates/uv/src/commands/project/sync.rs
@@ -17,6 +17,7 @@ use uv_configuration::{
     Preview, PreviewFeatures, TargetTriple, Upgrade,
 };
 use uv_dispatch::BuildDispatch;
+use uv_distribution::LoweredExtraBuildDependencies;
 use uv_distribution_types::{
     DirectorySourceDist, Dist, Index, Requirement, Resolution, ResolvedDist, SourceDist,
 };
@@ -227,7 +228,7 @@ pub(crate) async fn sync(
             // Parse the requirements from the script.
             let spec = script_specification(script.into(), &settings.resolver)?.unwrap_or_default();
             let script_extra_build_requires =
-                script_extra_build_requires(script.into(), &settings.resolver)?;
+                script_extra_build_requires(script.into(), &settings.resolver)?.into_inner();
 
             // Parse the build constraints from the script.
             let build_constraints = script
@@ -602,12 +603,12 @@ pub(super) async fn do_sync(
         );
     }
 
-    // Lower the extra build dependencies with source resolution
+    // Lower the extra build dependencies with source resolution.
     let extra_build_requires = match &target {
         InstallTarget::Workspace { workspace, .. }
         | InstallTarget::Project { workspace, .. }
         | InstallTarget::NonProjectWorkspace { workspace, .. } => {
-            uv_distribution::ExtraBuildRequires::from_workspace(
+            LoweredExtraBuildDependencies::from_workspace(
                 extra_build_dependencies.clone(),
                 workspace,
                 index_locations,
@@ -637,7 +638,8 @@ pub(super) async fn do_sync(
             };
             script_extra_build_requires((*script).into(), &resolver_settings)?
         }
-    };
+    }
+    .into_inner();
 
     let client_builder = BaseClientBuilder::new()
         .retries_from_env()?
diff --git a/crates/uv/src/commands/tool/install.rs b/crates/uv/src/commands/tool/install.rs
index 4917934c4..b191d0e1e 100644
--- a/crates/uv/src/commands/tool/install.rs
+++ b/crates/uv/src/commands/tool/install.rs
@@ -10,7 +10,7 @@ use uv_cache_info::Timestamp;
 use uv_client::BaseClientBuilder;
 use uv_configuration::{Concurrency, Constraints, DryRun, Preview, Reinstall, Upgrade};
 use uv_distribution_types::{
-    NameRequirementSpecification, Requirement, RequirementSource,
+    ExtraBuildRequires, NameRequirementSpecification, Requirement, RequirementSource,
     UnresolvedRequirementSpecification,
 };
 use uv_normalize::PackageName;
@@ -23,7 +23,7 @@ use uv_requirements::{RequirementsSource, RequirementsSpecification};
 use uv_settings::{PythonInstallMirrors, ResolverInstallerOptions, ToolOptions};
 use uv_tool::InstalledTools;
 use uv_warnings::warn_user;
-use uv_workspace::{WorkspaceCache, pyproject::ExtraBuildDependencies};
+use uv_workspace::WorkspaceCache;
 
 use crate::commands::ExitStatus;
 use crate::commands::pip::loggers::{DefaultInstallLogger, DefaultResolveLogger};
@@ -444,7 +444,7 @@ pub(crate) async fn install(
             spec,
             Modifications::Exact,
             Constraints::from_requirements(build_constraints.iter().cloned()),
-            uv_distribution::ExtraBuildRequires::from_lowered(ExtraBuildDependencies::default()),
+            ExtraBuildRequires::default(),
             &settings,
             &network_settings,
             &state,
diff --git a/crates/uv/src/commands/tool/upgrade.rs b/crates/uv/src/commands/tool/upgrade.rs
index 5e46a4a9d..4c62e15d6 100644
--- a/crates/uv/src/commands/tool/upgrade.rs
+++ b/crates/uv/src/commands/tool/upgrade.rs
@@ -9,7 +9,7 @@ use tracing::{debug, trace};
 use uv_cache::Cache;
 use uv_client::BaseClientBuilder;
 use uv_configuration::{Concurrency, Constraints, DryRun, Preview};
-use uv_distribution_types::Requirement;
+use uv_distribution_types::{ExtraBuildRequires, Requirement};
 use uv_fs::CWD;
 use uv_normalize::PackageName;
 use uv_python::{
@@ -20,7 +20,7 @@ use uv_requirements::RequirementsSpecification;
 use uv_settings::{Combine, PythonInstallMirrors, ResolverInstallerOptions, ToolOptions};
 use uv_tool::InstalledTools;
 use uv_warnings::write_error_chain;
-use uv_workspace::{WorkspaceCache, pyproject::ExtraBuildDependencies};
+use uv_workspace::WorkspaceCache;
 
 use crate::commands::pip::loggers::{
     DefaultInstallLogger, SummaryResolveLogger, UpgradeInstallLogger,
@@ -339,7 +339,7 @@ async fn upgrade_tool(
             spec,
             Modifications::Exact,
             build_constraints,
-            uv_distribution::ExtraBuildRequires::from_lowered(ExtraBuildDependencies::default()),
+            ExtraBuildRequires::default(),
             &settings,
             network_settings,
             &state,
diff --git a/crates/uv/src/commands/venv.rs b/crates/uv/src/commands/venv.rs
index 9bfa9d24d..1f48d5cfd 100644
--- a/crates/uv/src/commands/venv.rs
+++ b/crates/uv/src/commands/venv.rs
@@ -15,8 +15,8 @@ use uv_configuration::{
     SourceStrategy,
 };
 use uv_dispatch::{BuildDispatch, SharedState};
-use uv_distribution_types::Requirement;
 use uv_distribution_types::{DependencyMetadata, Index, IndexLocations};
+use uv_distribution_types::{ExtraBuildRequires, Requirement};
 use uv_fs::Simplified;
 use uv_install_wheel::LinkMode;
 use uv_normalize::DefaultGroups;
@@ -29,7 +29,6 @@ use uv_shell::{Shell, shlex_posix, shlex_windows};
 use uv_types::{AnyErrorBuild, BuildContext, BuildIsolation, BuildStack, HashStrategy};
 use uv_virtualenv::OnExisting;
 use uv_warnings::warn_user;
-use uv_workspace::pyproject::ExtraBuildDependencies;
 use uv_workspace::{DiscoveryOptions, VirtualProject, WorkspaceCache, WorkspaceError};
 
 use crate::commands::ExitStatus;
@@ -267,8 +266,7 @@ pub(crate) async fn venv(
 
         // Do not allow builds
         let build_options = BuildOptions::new(NoBinary::None, NoBuild::All);
-        let extra_build_requires =
-            uv_distribution::ExtraBuildRequires::from_lowered(ExtraBuildDependencies::default());
+        let extra_build_requires = ExtraBuildRequires::default();
         // Prep the build context.
         let build_dispatch = BuildDispatch::new(
             &client,
diff --git a/crates/uv/tests/it/sync.rs b/crates/uv/tests/it/sync.rs
index cb17c7fff..1e46314d4 100644
--- a/crates/uv/tests/it/sync.rs
+++ b/crates/uv/tests/it/sync.rs
@@ -2091,6 +2091,160 @@ fn sync_extra_build_dependencies_sources() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn sync_extra_build_dependencies_index() -> Result<()> {
+    let context = TestContext::new("3.12").with_filtered_counts();
+
+    // Write a test package that arbitrarily requires `anyio` at build time
+    let child = context.temp_dir.child("child");
+    child.create_dir_all()?;
+    let child_pyproject_toml = child.child("pyproject.toml");
+    child_pyproject_toml.write_str(indoc! {r#"
+        [project]
+        name = "child"
+        version = "0.1.0"
+        requires-python = ">=3.9"
+
+        [build-system]
+        requires = ["hatchling", "anyio"]
+        backend-path = ["."]
+        build-backend = "build_backend"
+    "#})?;
+
+    // Create a build backend that checks for a specific version of anyio
+    let build_backend = child.child("build_backend.py");
+    build_backend.write_str(indoc! {r#"
+        import os
+        import sys
+        from hatchling.build import *
+
+        expected_version = os.environ.get("EXPECTED_ANYIO_VERSION", "")
+        if not expected_version:
+            print("`EXPECTED_ANYIO_VERSION` not set", file=sys.stderr)
+            sys.exit(1)
+
+        try:
+            import anyio
+        except ModuleNotFoundError:
+            print("Missing `anyio` module", file=sys.stderr)
+            sys.exit(1)
+
+        from importlib.metadata import version
+        anyio_version = version("anyio")
+
+        if not anyio_version.startswith(expected_version):
+            print(f"Expected `anyio` version {expected_version} but got {anyio_version}", file=sys.stderr)
+            sys.exit(1)
+
+        print(f"Found expected `anyio` version {anyio_version}", file=sys.stderr)
+    "#})?;
+    child.child("src/child/__init__.py").touch()?;
+
+    let parent = &context.temp_dir;
+    let pyproject_toml = parent.child("pyproject.toml");
+    pyproject_toml.write_str(indoc! {r#"
+        [project]
+        name = "parent"
+        version = "0.1.0"
+        requires-python = ">=3.9"
+        dependencies = ["child"]
+
+        [tool.uv.sources]
+        child = { path = "child" }
+    "#})?;
+
+    // Ensure our build backend is checking the version correctly
+    uv_snapshot!(context.filters(), context.sync().env("EXPECTED_ANYIO_VERSION", "3.0"), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved [N] packages in [TIME]
+      × Failed to build `child @ file://[TEMP_DIR]/child`
+      ├─▶ The build backend returned an error
+      ╰─▶ Call to `build_backend.build_wheel` failed (exit status: 1)
+
+          [stderr]
+          Expected `anyio` version 3.0 but got 4.3.0
+
+          hint: This usually indicates a problem with the package or the build environment.
+      help: `child` was included because `parent` (v0.1.0) depends on `child`
+    ");
+
+    // Ensure that we're resolving to `4.3.0`, the "latest" on PyPI.
+    uv_snapshot!(context.filters(), context.sync().env("EXPECTED_ANYIO_VERSION", "4.3"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved [N] packages in [TIME]
+    Prepared [N] packages in [TIME]
+    Installed [N] packages in [TIME]
+     + child==0.1.0 (from file://[TEMP_DIR]/child)
+    ");
+
+    // Pin `anyio` to the Test PyPI.
+    pyproject_toml.write_str(indoc! {r#"
+        [project]
+        name = "parent"
+        version = "0.1.0"
+        requires-python = ">=3.9"
+        dependencies = ["child"]
+
+        [tool.uv.sources]
+        child = { path = "child" }
+        anyio = { index = "test" }
+
+        [tool.uv.extra-build-dependencies]
+        child = ["anyio"]
+
+        [[tool.uv.index]]
+        url = "https://test.pypi.org/simple"
+        name = "test"
+        explicit = true
+    "#})?;
+
+    // The child should be rebuilt with `3.5` on reinstall, the "latest" on Test PyPI.
+    uv_snapshot!(context.filters(), context.sync()
+        .arg("--reinstall-package").arg("child").env("EXPECTED_ANYIO_VERSION", "4.3"), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+
+    ----- stderr -----
+    warning: The `extra-build-dependencies` option is experimental and may change without warning. Pass `--preview-features extra-build-dependencies` to disable this warning.
+    Resolved [N] packages in [TIME]
+      × Failed to build `child @ file://[TEMP_DIR]/child`
+      ├─▶ The build backend returned an error
+      ╰─▶ Call to `build_backend.build_wheel` failed (exit status: 1)
+
+          [stderr]
+          Expected `anyio` version 4.3 but got 3.5.0
+
+          hint: This usually indicates a problem with the package or the build environment.
+      help: `child` was included because `parent` (v0.1.0) depends on `child`
+    ");
+
+    uv_snapshot!(context.filters(), context.sync()
+        .arg("--reinstall-package").arg("child").env("EXPECTED_ANYIO_VERSION", "3.5"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    warning: The `extra-build-dependencies` option is experimental and may change without warning. Pass `--preview-features extra-build-dependencies` to disable this warning.
+    Resolved [N] packages in [TIME]
+    Prepared [N] packages in [TIME]
+    Uninstalled [N] packages in [TIME]
+    Installed [N] packages in [TIME]
+     ~ child==0.1.0 (from file://[TEMP_DIR]/child)
+    ");
+
+    Ok(())
+}
+
 #[test]
 fn sync_extra_build_dependencies_sources_from_child() -> Result<()> {
     let context = TestContext::new("3.12").with_filtered_counts();