From 79a875ba541164dd63316279eed6178bd143c2c9 Mon Sep 17 00:00:00 2001
From: Charlie Marsh <charlie.r.marsh@gmail.com>
Date: Sat, 24 Aug 2024 11:46:31 -0400
Subject: [PATCH] Add support for virtual projects

---
 crates/uv-cli/src/lib.rs               |   9 +-
 crates/uv-settings/src/settings.rs     |   4 +
 crates/uv-workspace/src/pyproject.rs   |  34 +
 crates/uv-workspace/src/workspace.rs   |   6 +-
 crates/uv/src/commands/project/init.rs | 126 ++--
 crates/uv/src/commands/project/sync.rs |  35 +
 crates/uv/tests/common/mod.rs          |   5 +-
 crates/uv/tests/edit.rs                | 330 ++++++++-
 crates/uv/tests/init.rs                |  74 +-
 crates/uv/tests/lock.rs                | 904 ++++++++++++++++++++++++-
 crates/uv/tests/run.rs                 |  92 ++-
 crates/uv/tests/sync.rs                |  64 +-
 crates/uv/tests/workspace.rs           | 105 ++-
 docs/reference/cli.md                  |   6 +-
 docs/reference/settings.md             |  25 +
 uv.schema.json                         |   7 +
 16 files changed, 1680 insertions(+), 146 deletions(-)

diff --git a/crates/uv-cli/src/lib.rs b/crates/uv-cli/src/lib.rs
index b68666f2c04ae..ea67833743f9a 100644
--- a/crates/uv-cli/src/lib.rs
+++ b/crates/uv-cli/src/lib.rs
@@ -2099,11 +2099,12 @@ pub struct InitArgs {
     #[arg(long)]
     pub name: Option<PackageName>,
 
-    /// Create a virtual workspace instead of a project.
+    /// Create a virtual project, rather than a package.
     ///
-    /// A virtual workspace does not define project dependencies and cannot be
-    /// published. Instead, workspace members declare project dependencies.
-    /// Development dependencies may still be declared.
+    /// A virtual project is a project that is not intended to be built as a Python package,
+    /// such as a project that only contains scripts or other application code.
+    ///
+    /// Virtual projects themselves are not installed into the Python environment.
     #[arg(long)]
     pub r#virtual: bool,
 
diff --git a/crates/uv-settings/src/settings.rs b/crates/uv-settings/src/settings.rs
index 273a1d8c0d6d2..005ab499680e1 100644
--- a/crates/uv-settings/src/settings.rs
+++ b/crates/uv-settings/src/settings.rs
@@ -70,6 +70,10 @@ pub struct Options {
     #[serde(default, skip_serializing)]
     #[cfg_attr(feature = "schemars", schemars(skip))]
     managed: serde::de::IgnoredAny,
+
+    #[serde(default, skip_serializing)]
+    #[cfg_attr(feature = "schemars", schemars(skip))]
+    r#virtual: serde::de::IgnoredAny,
 }
 
 impl Options {
diff --git a/crates/uv-workspace/src/pyproject.rs b/crates/uv-workspace/src/pyproject.rs
index c2eaee29652f2..fb093be226cbe 100644
--- a/crates/uv-workspace/src/pyproject.rs
+++ b/crates/uv-workspace/src/pyproject.rs
@@ -33,6 +33,10 @@ pub struct PyProjectToml {
     /// The raw unserialized document.
     #[serde(skip)]
     pub raw: String,
+
+    /// Used to determine whether a `build-system` is present.
+    #[serde(default, skip_serializing)]
+    build_system: Option<serde::de::IgnoredAny>,
 }
 
 impl PyProjectToml {
@@ -41,6 +45,27 @@ impl PyProjectToml {
         let pyproject = toml::from_str(&raw)?;
         Ok(PyProjectToml { raw, ..pyproject })
     }
+
+    /// Returns `true` if the project should be considered "virtual".
+    pub fn is_virtual(&self) -> bool {
+        // A project is virtual if `virtual = true` is set...
+        if self
+            .tool
+            .as_ref()
+            .and_then(|tool| tool.uv.as_ref())
+            .and_then(|uv| uv.r#virtual)
+            == Some(true)
+        {
+            return true;
+        }
+
+        // Or if `build-system` is not present.
+        if self.build_system.is_none() {
+            return true;
+        }
+
+        false
+    }
 }
 
 // Ignore raw document in comparison.
@@ -100,6 +125,15 @@ pub struct ToolUv {
         "#
     )]
     pub managed: Option<bool>,
+    /// Whether the project should be considered "virtual".
+    #[option(
+        default = r#"true"#,
+        value_type = "bool",
+        example = r#"
+            virtual = false
+        "#
+    )]
+    pub r#virtual: Option<bool>,
     /// The project's development dependencies. Development dependencies will be installed by
     /// default in `uv run` and `uv sync`, but will not appear in the project's published metadata.
     #[cfg_attr(
diff --git a/crates/uv-workspace/src/workspace.rs b/crates/uv-workspace/src/workspace.rs
index 4e8f3d34aa097..afeabacf0b8de 100644
--- a/crates/uv-workspace/src/workspace.rs
+++ b/crates/uv-workspace/src/workspace.rs
@@ -1339,7 +1339,7 @@ impl VirtualProject {
         }
     }
 
-    /// Return the [`PackageName`] of the project, if it's not a virtual workspace.
+    /// Return the [`PackageName`] of the project, if it's not a virtual workspace root.
     pub fn project_name(&self) -> Option<&PackageName> {
         match self {
             VirtualProject::Project(project) => Some(project.project_name()),
@@ -1347,7 +1347,7 @@ impl VirtualProject {
         }
     }
 
-    /// Returns `true` if the project is a virtual workspace.
+    /// Returns `true` if the project is a virtual workspace root.
     pub fn is_virtual(&self) -> bool {
         matches!(self, VirtualProject::Virtual(_))
     }
@@ -1535,6 +1535,7 @@ mod tests {
                         "exclude": null
                       },
                       "managed": null,
+                      "virtual": null,
                       "dev-dependencies": null,
                       "environments": null,
                       "override-dependencies": null,
@@ -1607,6 +1608,7 @@ mod tests {
                         "exclude": null
                       },
                       "managed": null,
+                      "virtual": null,
                       "dev-dependencies": null,
                       "environments": null,
                       "override-dependencies": null,
diff --git a/crates/uv/src/commands/project/init.rs b/crates/uv/src/commands/project/init.rs
index 7180d9157b3a6..914abc1ac440b 100644
--- a/crates/uv/src/commands/project/init.rs
+++ b/crates/uv/src/commands/project/init.rs
@@ -15,7 +15,7 @@ use uv_python::{
 };
 use uv_resolver::RequiresPython;
 use uv_workspace::pyproject_mut::{DependencyTarget, PyProjectTomlMut};
-use uv_workspace::{check_nested_workspaces, DiscoveryOptions, Workspace, WorkspaceError};
+use uv_workspace::{DiscoveryOptions, Workspace, WorkspaceError};
 
 use crate::commands::project::find_requires_python;
 use crate::commands::reporters::PythonDownloadReporter;
@@ -69,24 +69,21 @@ pub(crate) async fn init(
         }
     };
 
-    if r#virtual {
-        init_virtual_workspace(&path, no_workspace)?;
-    } else {
-        init_project(
-            &path,
-            &name,
-            no_readme,
-            python,
-            no_workspace,
-            python_preference,
-            python_downloads,
-            connectivity,
-            native_tls,
-            cache,
-            printer,
-        )
-        .await?;
-    }
+    init_project(
+        &path,
+        &name,
+        r#virtual,
+        no_readme,
+        python,
+        no_workspace,
+        python_preference,
+        python_downloads,
+        connectivity,
+        native_tls,
+        cache,
+        printer,
+    )
+    .await?;
 
     // Create the `README.md` if it does not already exist.
     if !no_readme {
@@ -126,29 +123,12 @@ pub(crate) async fn init(
     Ok(ExitStatus::Success)
 }
 
-/// Initialize a virtual workspace at the given path.
-fn init_virtual_workspace(path: &Path, no_workspace: bool) -> Result<()> {
-    // Ensure that we aren't creating a nested workspace.
-    if !no_workspace {
-        check_nested_workspaces(path, &DiscoveryOptions::default());
-    }
-
-    // Create the `pyproject.toml`.
-    let pyproject = indoc::indoc! {r"
-        [tool.uv.workspace]
-        members = []
-    "};
-
-    fs_err::create_dir_all(path)?;
-    fs_err::write(path.join("pyproject.toml"), pyproject)?;
-
-    Ok(())
-}
-
 /// Initialize a project (and, implicitly, a workspace root) at the given path.
+#[allow(clippy::fn_params_excessive_bools)]
 async fn init_project(
     path: &Path,
     name: &PackageName,
+    r#virtual: bool,
     no_readme: bool,
     python: Option<String>,
     no_workspace: bool,
@@ -265,38 +245,56 @@ async fn init_project(
         RequiresPython::greater_than_equal_version(&interpreter.python_minor_version())
     };
 
-    // Create the `pyproject.toml`.
-    let pyproject = indoc::formatdoc! {r#"
-        [project]
-        name = "{name}"
-        version = "0.1.0"
-        description = "Add your description here"{readme}
-        requires-python = "{requires_python}"
-        dependencies = []
+    if r#virtual {
+        // Create the `pyproject.toml`, but omit `[build-system]`.
+        let pyproject = indoc::formatdoc! {r#"
+            [project]
+            name = "{name}"
+            version = "0.1.0"
+            description = "Add your description here"{readme}
+            requires-python = "{requires_python}"
+            dependencies = []
+            "#,
+            readme = if no_readme { "" } else { "\nreadme = \"README.md\"" },
+            requires_python = requires_python.specifiers(),
+        };
 
-        [build-system]
-        requires = ["hatchling"]
-        build-backend = "hatchling.build"
-        "#,
-        readme = if no_readme { "" } else { "\nreadme = \"README.md\"" },
-        requires_python = requires_python.specifiers(),
-    };
+        fs_err::create_dir_all(path)?;
+        fs_err::write(path.join("pyproject.toml"), pyproject)?;
+    } else {
+        // Create the `pyproject.toml`.
+        let pyproject = indoc::formatdoc! {r#"
+            [project]
+            name = "{name}"
+            version = "0.1.0"
+            description = "Add your description here"{readme}
+            requires-python = "{requires_python}"
+            dependencies = []
+
+            [build-system]
+            requires = ["hatchling"]
+            build-backend = "hatchling.build"
+            "#,
+            readme = if no_readme { "" } else { "\nreadme = \"README.md\"" },
+            requires_python = requires_python.specifiers(),
+        };
 
-    fs_err::create_dir_all(path)?;
-    fs_err::write(path.join("pyproject.toml"), pyproject)?;
+        fs_err::create_dir_all(path)?;
+        fs_err::write(path.join("pyproject.toml"), pyproject)?;
 
-    // Create `src/{name}/__init__.py`, if it doesn't exist already.
-    let src_dir = path.join("src").join(&*name.as_dist_info_name());
-    let init_py = src_dir.join("__init__.py");
-    if !init_py.try_exists()? {
-        fs_err::create_dir_all(&src_dir)?;
-        fs_err::write(
-            init_py,
-            indoc::formatdoc! {r#"
+        // Create `src/{name}/__init__.py`, if it doesn't exist already.
+        let src_dir = path.join("src").join(&*name.as_dist_info_name());
+        let init_py = src_dir.join("__init__.py");
+        if !init_py.try_exists()? {
+            fs_err::create_dir_all(&src_dir)?;
+            fs_err::write(
+                init_py,
+                indoc::formatdoc! {r#"
             def hello() -> str:
                 return "Hello from {name}!"
             "#},
-        )?;
+            )?;
+        }
     }
 
     if let Some(workspace) = workspace {
diff --git a/crates/uv/src/commands/project/sync.rs b/crates/uv/src/commands/project/sync.rs
index ef97e30fe3029..c42954ec55257 100644
--- a/crates/uv/src/commands/project/sync.rs
+++ b/crates/uv/src/commands/project/sync.rs
@@ -1,5 +1,8 @@
 use anyhow::{Context, Result};
 use itertools::Itertools;
+use rustc_hash::FxHashSet;
+
+use distribution_types::Name;
 use pep508_rs::MarkerTree;
 use uv_auth::store_credentials_from_url;
 use uv_cache::Cache;
@@ -195,6 +198,9 @@ pub(super) async fn do_sync(
     // Read the lockfile.
     let resolution = lock.to_resolution(project, &markers, tags, extras, &dev)?;
 
+    // Always skip virtual projects, which shouldn't be built or installed.
+    let resolution = apply_no_virtual_project(resolution, project);
+
     // Filter resolution based on install-specific options.
     let resolution = install_options.filter_resolution(resolution, project);
 
@@ -289,3 +295,32 @@ pub(super) async fn do_sync(
 
     Ok(())
 }
+
+/// Filter out any virtual workspace members.
+fn apply_no_virtual_project(
+    resolution: distribution_types::Resolution,
+    project: &VirtualProject,
+) -> distribution_types::Resolution {
+    let VirtualProject::Project(project) = project else {
+        // If the project is _only_ a virtual workspace root, we don't need to filter it out.
+        return resolution;
+    };
+
+    let virtual_members = project
+        .workspace()
+        .packages()
+        .iter()
+        .filter_map(|(name, package)| {
+            // A project is virtual if it's explicitly marked as virtual, _or_ if it's missing a
+            // build system.
+            if package.pyproject_toml().is_virtual() {
+                Some(name)
+            } else {
+                None
+            }
+        })
+        .collect::<FxHashSet<_>>();
+
+    // Remove any virtual members from the resolution.
+    resolution.filter(|dist| !virtual_members.contains(dist.name()))
+}
diff --git a/crates/uv/tests/common/mod.rs b/crates/uv/tests/common/mod.rs
index d8e4f8daa7d88..ec187573b3189 100644
--- a/crates/uv/tests/common/mod.rs
+++ b/crates/uv/tests/common/mod.rs
@@ -1110,8 +1110,9 @@ pub fn make_project(dir: &Path, name: &str, body: &str) -> anyhow::Result<()> {
         {body}
 
         [build-system]
-        requires = ["flit_core>=3.8,<4"]
-        build-backend = "flit_core.buildapi"
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         "#
     };
     fs_err::create_dir_all(dir)?;
diff --git a/crates/uv/tests/edit.rs b/crates/uv/tests/edit.rs
index c8425aa140c2a..fd1d411c35a39 100644
--- a/crates/uv/tests/edit.rs
+++ b/crates/uv/tests/edit.rs
@@ -20,9 +20,12 @@ fn add_registry() -> Result<()> {
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.add(&["anyio==3.7.0"]), @r###"
@@ -50,11 +53,14 @@ fn add_registry() -> Result<()> {
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = [
             "anyio==3.7.0",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -143,6 +149,10 @@ fn add_git() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.lock(), @r###"
@@ -212,6 +222,10 @@ fn add_git() -> Result<()> {
             "uv-public-pypackage",
         ]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         uv-public-pypackage = { git = "https://github.com/astral-test/uv-public-pypackage", tag = "0.0.1" }
         "###
@@ -313,6 +327,10 @@ fn add_git_private_source() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.add(&[&format!("uv-private-pypackage @ git+https://{token}@github.com/astral-test/uv-private-pypackage")]), @r###"
@@ -343,6 +361,10 @@ fn add_git_private_source() -> Result<()> {
             "uv-private-pypackage",
         ]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         uv-private-pypackage = { git = "https://github.com/astral-test/uv-private-pypackage" }
         "###
@@ -409,6 +431,10 @@ fn add_git_private_raw() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.add(&[&format!("uv-private-pypackage @ git+https://{token}@github.com/astral-test/uv-private-pypackage")]).arg("--raw-sources"), @r###"
@@ -443,6 +469,10 @@ fn add_git_private_raw() -> Result<()> {
         dependencies = [
             "uv-private-pypackage @ git+https://***@github.com/astral-test/uv-private-pypackage",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -504,6 +534,10 @@ fn add_git_error() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.lock(), @r###"
@@ -562,6 +596,10 @@ fn add_git_raw() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.lock(), @r###"
@@ -617,6 +655,10 @@ fn add_git_raw() -> Result<()> {
             "anyio==3.7.0",
             "uv-public-pypackage @ git+https://github.com/astral-test/uv-public-pypackage@0.0.1",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -714,6 +756,10 @@ fn add_git_implicit() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.lock(), @r###"
@@ -770,6 +816,10 @@ fn add_raw_error() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     // Provide a tag without a Git source.
@@ -800,9 +850,12 @@ fn add_unnamed() -> Result<()> {
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.add(&["git+https://github.com/astral-test/uv-public-pypackage"]).arg("--tag=0.0.1"), @r###"
@@ -828,12 +881,15 @@ fn add_unnamed() -> Result<()> {
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = [
             "uv-public-pypackage",
         ]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         uv-public-pypackage = { git = "https://github.com/astral-test/uv-public-pypackage", tag = "0.0.1" }
         "###
@@ -897,6 +953,10 @@ fn add_remove_dev() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.add(&["anyio==3.7.0"]).arg("--dev"), @r###"
@@ -927,6 +987,10 @@ fn add_remove_dev() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = []
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         dev-dependencies = [
             "anyio==3.7.0",
@@ -1049,6 +1113,10 @@ fn add_remove_dev() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = []
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         dev-dependencies = []
         "###
@@ -1101,6 +1169,10 @@ fn add_remove_optional() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.add(&["anyio==3.7.0"]).arg("--optional=io"), @r###"
@@ -1135,6 +1207,10 @@ fn add_remove_optional() -> Result<()> {
         io = [
             "anyio==3.7.0",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -1254,6 +1330,10 @@ fn add_remove_optional() -> Result<()> {
 
         [project.optional-dependencies]
         io = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -1310,6 +1390,10 @@ fn add_remove_workspace() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     let pyproject_toml = context.temp_dir.child("child2/pyproject.toml");
@@ -1319,6 +1403,10 @@ fn add_remove_workspace() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     // Adding a workspace package with a mismatched source should error.
@@ -1374,6 +1462,10 @@ fn add_remove_workspace() -> Result<()> {
             "child2",
         ]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         child2 = { workspace = true }
         "###
@@ -1457,6 +1549,10 @@ fn add_remove_workspace() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = []
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         "###
         );
@@ -1525,6 +1621,10 @@ fn add_workspace_editable() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     let pyproject_toml = context.temp_dir.child("child2/pyproject.toml");
@@ -1534,6 +1634,10 @@ fn add_workspace_editable() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     let child1 = context.temp_dir.join("child1");
@@ -1568,6 +1672,10 @@ fn add_workspace_editable() -> Result<()> {
             "child2",
         ]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         child2 = { workspace = true }
         "###
@@ -1743,9 +1851,11 @@ fn update() -> Result<()> {
         name = "project"
         version = "0.1.0"
         requires-python = ">=3.12"
-        dependencies = [
-            "requests==2.31.0"
-        ]
+        dependencies = ["requests==2.31.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.lock(), @r###"
@@ -1801,6 +1911,10 @@ fn update() -> Result<()> {
         dependencies = [
             "requests[security]==2.31.0",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -1836,6 +1950,10 @@ fn update() -> Result<()> {
             "requests[security]==2.31.0",
             "requests[socks,use-chardet-on-py3]>=2.31.0 ; python_full_version >= '3.8'",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -1873,6 +1991,10 @@ fn update() -> Result<()> {
             "requests[socks,use-chardet-on-py3]>=2.31.0 ; python_full_version >= '3.8'",
         ]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         requests = { git = "https://github.com/psf/requests", tag = "v2.32.3" }
         "###
@@ -2021,9 +2143,11 @@ fn add_update_marker() -> Result<()> {
         name = "project"
         version = "0.1.0"
         requires-python = ">=3.8"
-        dependencies = [
-            "requests>=2.30; python_version >= '3.11'"
-        ]
+        dependencies = ["requests>=2.30; python_version >= '3.11'"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     uv_snapshot!(context.filters(), context.lock(), @r###"
     success: true
@@ -2080,6 +2204,10 @@ fn add_update_marker() -> Result<()> {
             "requests>=2.30; python_version >= '3.11'",
             "requests>=2.0,<2.29 ; python_full_version < '3.11'",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -2114,6 +2242,10 @@ fn add_update_marker() -> Result<()> {
             "requests>=2.30; python_version >= '3.11'",
             "requests>=2.0,<2.20 ; python_full_version < '3.11'",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -2153,6 +2285,10 @@ fn add_update_marker() -> Result<()> {
             "requests>=2.0,<2.20 ; python_full_version < '3.11'",
             "requests>=2.31 ; python_full_version >= '3.12' and sys_platform == 'win32'",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -2190,6 +2326,10 @@ fn add_update_marker() -> Result<()> {
             "requests>=2.31 ; python_full_version >= '3.12' and sys_platform == 'win32'",
             "requests>=2.10 ; sys_platform == 'win32'",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -2226,6 +2366,10 @@ fn add_update_marker() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.8"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -2247,6 +2391,10 @@ fn update_source_replace_url() -> Result<()> {
         dependencies = [
             "requests[security] @ https://files.pythonhosted.org/packages/f9/9b/335f9764261e915ed497fcdeb11df5dfd6f7bf257d4a6a2a686d80da4d54/requests-2.32.3-py3-none-any.whl"
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     // Change the source. The existing URL should be removed.
@@ -2282,6 +2430,10 @@ fn update_source_replace_url() -> Result<()> {
             "requests[security]",
         ]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         requests = { git = "https://github.com/psf/requests", tag = "v2.32.3" }
         "###
@@ -2302,9 +2454,11 @@ fn add_inexact() -> Result<()> {
         name = "project"
         version = "0.1.0"
         requires-python = ">=3.12"
-        dependencies = [
-            "anyio == 3.7.0",
-        ]
+        dependencies = ["anyio == 3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.lock(), @r###"
@@ -2337,6 +2491,10 @@ fn add_inexact() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.add(&["iniconfig==2.0.0"]), @r###"
@@ -2367,6 +2525,10 @@ fn add_inexact() -> Result<()> {
         dependencies = [
             "iniconfig==2.0.0",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -2445,6 +2607,10 @@ fn remove_registry() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.lock(), @r###"
@@ -2498,6 +2664,10 @@ fn remove_registry() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -2545,11 +2715,12 @@ fn add_preserves_indentation_in_pyproject_toml() -> Result<()> {
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
-        dependencies = [
-          "anyio==3.7.0"
-        ]
+        dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.add(&["requests==2.31.0"]), @r###"
@@ -2581,12 +2752,15 @@ fn add_preserves_indentation_in_pyproject_toml() -> Result<()> {
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = [
-          "anyio==3.7.0",
-          "requests==2.31.0",
+            "anyio==3.7.0",
+            "requests==2.31.0",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -2602,9 +2776,12 @@ fn add_puts_default_indentation_in_pyproject_toml_if_not_observed() -> Result<()
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.add(&["requests==2.31.0"]), @r###"
@@ -2636,12 +2813,15 @@ fn add_puts_default_indentation_in_pyproject_toml_if_not_observed() -> Result<()
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = [
             "anyio==3.7.0",
             "requests==2.31.0",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -2658,9 +2838,12 @@ fn add_frozen() -> Result<()> {
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.add(&["anyio==3.7.0"]).arg("--frozen"), @r###"
@@ -2681,11 +2864,14 @@ fn add_frozen() -> Result<()> {
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = [
             "anyio==3.7.0",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -2705,9 +2891,12 @@ fn add_no_sync() -> Result<()> {
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.add(&["anyio==3.7.0"]).arg("--no-sync"), @r###"
@@ -2729,11 +2918,14 @@ fn add_no_sync() -> Result<()> {
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = [
             "anyio==3.7.0",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -2821,9 +3013,12 @@ fn add_error() -> Result<()> {
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.add(&["xyz"]), @r###"
@@ -2863,6 +3058,10 @@ fn add_lower_bound() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     // Adding `anyio` should include a lower-bound.
@@ -2895,6 +3094,10 @@ fn add_lower_bound() -> Result<()> {
         dependencies = [
             "anyio>=4.3.0",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -2914,6 +3117,10 @@ fn add_lower_bound_existing() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     // Adding `anyio` should _not_ set a lower-bound, since it's already present (even if
@@ -2947,6 +3154,10 @@ fn add_lower_bound_existing() -> Result<()> {
         dependencies = [
             "anyio",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -2966,6 +3177,10 @@ fn add_lower_bound_raw() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     // Adding `anyio` should _not_ set a lower-bound when using `--raw-sources`.
@@ -2998,6 +3213,10 @@ fn add_lower_bound_raw() -> Result<()> {
         dependencies = [
             "anyio",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -3017,6 +3236,10 @@ fn add_lower_bound_dev() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     // Adding `anyio` should include a lower-bound.
@@ -3048,6 +3271,10 @@ fn add_lower_bound_dev() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = []
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         dev-dependencies = [
             "anyio>=4.3.0",
@@ -3071,6 +3298,10 @@ fn add_lower_bound_optional() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     // Adding `anyio` should include a lower-bound.
@@ -3106,6 +3337,10 @@ fn add_lower_bound_optional() -> Result<()> {
         io = [
             "anyio>=4.3.0",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -3185,6 +3420,10 @@ fn add_lower_bound_local() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     // Adding `torch` should include a lower-bound, but no local segment.
@@ -3215,6 +3454,10 @@ fn add_lower_bound_local() -> Result<()> {
         dependencies = [
             "local-simple-a>=1.2.3",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -3359,9 +3602,12 @@ fn add_repeat() -> Result<()> {
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     uv_snapshot!(context.filters(), context.add(&["anyio"]), @r###"
@@ -3389,11 +3635,14 @@ fn add_repeat() -> Result<()> {
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = [
             "anyio>=4.3.0",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -3418,11 +3667,14 @@ fn add_repeat() -> Result<()> {
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = [
             "anyio>=4.3.0",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
@@ -3440,9 +3692,12 @@ fn add_requirements_file() -> Result<()> {
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     let requirements_txt = context.temp_dir.child("requirements.txt");
@@ -3481,13 +3736,16 @@ fn add_requirements_file() -> Result<()> {
         [project]
         name = "project"
         version = "0.1.0"
-        # ...
         requires-python = ">=3.12"
         dependencies = [
             "flask==2.3.2",
             "anyio",
         ]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         anyio = { git = "https://github.com/agronholm/anyio.git", rev = "4.4.0" }
         "###
@@ -3985,6 +4243,10 @@ fn fail_to_add_revert_project() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     // Adding `pytorch==1.0.2` should produce an error
@@ -4032,6 +4294,10 @@ fn fail_to_add_revert_project() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "###
         );
     });
diff --git a/crates/uv/tests/init.rs b/crates/uv/tests/init.rs
index e36c417cac4f1..bb5cb58aa8568 100644
--- a/crates/uv/tests/init.rs
+++ b/crates/uv/tests/init.rs
@@ -882,9 +882,9 @@ fn init_explicit_workspace() -> Result<()> {
     Ok(())
 }
 
-/// Run `uv init` from within a virtual workspace.
+/// Run `uv init --virtual` to create a virtual project.
 #[test]
-fn init_virtual_workspace() -> Result<()> {
+fn init_virtual_project() -> Result<()> {
     let context = TestContext::new("3.12");
 
     let child = context.temp_dir.child("foo");
@@ -907,12 +907,67 @@ fn init_virtual_workspace() -> Result<()> {
     }, {
         assert_snapshot!(
             pyproject, @r###"
+        [project]
+        name = "foo"
+        version = "0.1.0"
+        description = "Add your description here"
+        readme = "README.md"
+        requires-python = ">=3.12"
+        dependencies = []
+        "###
+        );
+    });
+
+    uv_snapshot!(context.filters(), context.init().current_dir(&child).arg("bar"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Adding `bar` as member of workspace `[TEMP_DIR]/foo`
+    Initialized project `bar` at `[TEMP_DIR]/foo/bar`
+    "###);
+
+    let pyproject = fs_err::read_to_string(pyproject_toml)?;
+    insta::with_settings!({
+        filters => context.filters(),
+    }, {
+        assert_snapshot!(
+            pyproject, @r###"
+        [project]
+        name = "foo"
+        version = "0.1.0"
+        description = "Add your description here"
+        readme = "README.md"
+        requires-python = ">=3.12"
+        dependencies = []
+
         [tool.uv.workspace]
-        members = []
+        members = ["bar"]
         "###
         );
     });
 
+    Ok(())
+}
+
+/// Run `uv init` from within a virtual workspace.
+#[test]
+fn init_virtual_workspace() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let child = context.temp_dir.child("foo");
+    child.create_dir_all()?;
+
+    // Create a virtual workspace.
+    let pyproject_toml = child.child("pyproject.toml");
+    pyproject_toml.write_str(indoc! {
+        r"
+        [tool.uv.workspace]
+        members = []
+        ",
+    })?;
+
     uv_snapshot!(context.filters(), context.init().current_dir(&child).arg("bar"), @r###"
     success: true
     exit_code: 0
@@ -957,7 +1012,7 @@ fn init_nested_virtual_workspace() -> Result<()> {
     ----- stdout -----
 
     ----- stderr -----
-    warning: Nested workspaces are not supported, but outer workspace (`[TEMP_DIR]/`) includes `[TEMP_DIR]/foo`
+    Adding `foo` as member of workspace `[TEMP_DIR]/`
     Initialized workspace `foo` at `[TEMP_DIR]/foo`
     "###);
 
@@ -967,8 +1022,13 @@ fn init_nested_virtual_workspace() -> Result<()> {
     }, {
         assert_snapshot!(
             pyproject, @r###"
-        [tool.uv.workspace]
-        members = []
+        [project]
+        name = "foo"
+        version = "0.1.0"
+        description = "Add your description here"
+        readme = "README.md"
+        requires-python = ">=3.12"
+        dependencies = []
         "###
         );
     });
@@ -980,7 +1040,7 @@ fn init_nested_virtual_workspace() -> Result<()> {
         assert_snapshot!(
             workspace, @r###"
         [tool.uv.workspace]
-        members = []
+        members = ["foo"]
         "###
         );
     });
diff --git a/crates/uv/tests/lock.rs b/crates/uv/tests/lock.rs
index 38080386a8551..5018cdcce9595 100644
--- a/crates/uv/tests/lock.rs
+++ b/crates/uv/tests/lock.rs
@@ -28,6 +28,10 @@ fn lock_wheel_registry() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -150,6 +154,10 @@ fn lock_sdist_registry() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["source-distribution==0.0.1"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -233,6 +241,10 @@ fn lock_sdist_git() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["uv-public-pypackage"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         uv-public-pypackage = { git = "https://github.com/astral-test/uv-public-pypackage", tag = "0.0.1" }
         "#,
@@ -323,6 +335,10 @@ fn lock_sdist_git() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["uv-public-pypackage"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         uv-public-pypackage = { git = "https://github.com/astral-test/uv-public-pypackage", rev = "0dacfd662c64cb4ceb16e6cf65a157a8b715b979" }
         "#,
@@ -379,6 +395,10 @@ fn lock_sdist_git() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["uv-public-pypackage"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         uv-public-pypackage = { git = "https://github.com/astral-test/uv-public-pypackage", rev = "b270df1a2fb5d012294e9aaf05e7e0bab1e6a389" }
         "#,
@@ -435,6 +455,10 @@ fn lock_sdist_git() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["uv-public-pypackage"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         uv-public-pypackage = { git = "https://github.com/astral-test/uv-public-pypackage", tag = "0.0.2" }
         "#,
@@ -498,6 +522,10 @@ fn lock_sdist_git_subdirectory() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["example-pkg-a @ git+https://github.com/pypa/sample-namespace-packages.git@df7530eeb8fa0cb7dbb8ecb28363e8e36bfa2f45#subdirectory=pkg_resources/pkg_a"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -582,6 +610,10 @@ fn lock_sdist_git_pep508() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["uv-public-pypackage @ git+https://github.com/astral-test/uv-public-pypackage.git@0.0.1"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -645,6 +677,10 @@ fn lock_sdist_git_pep508() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["uv-public-pypackage @ git+https://github.com/astral-test/uv-public-pypackage.git@0dacfd662c64cb4ceb16e6cf65a157a8b715b979"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -698,6 +734,10 @@ fn lock_sdist_git_pep508() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["uv-public-pypackage @ git+https://github.com/astral-test/uv-public-pypackage.git@b270df1a2fb5d012294e9aaf05e7e0bab1e6a389"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -751,6 +791,10 @@ fn lock_sdist_git_pep508() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["uv-public-pypackage @ git+https://github.com/astral-test/uv-public-pypackage.git@0.0.2"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -813,6 +857,10 @@ fn lock_sdist_git_short_rev() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["uv-public-pypackage"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         uv-public-pypackage = { git = "https://github.com/astral-test/uv-public-pypackage", rev = "0dacfd6" }
         "#,
@@ -909,6 +957,10 @@ fn lock_wheel_url() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio @ https://files.pythonhosted.org/packages/14/fd/2f20c40b45e4fb4324834aea24bd4afdf1143390242c0b33774da0e2e34f/anyio-4.3.0-py3-none-any.whl"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -1052,6 +1104,10 @@ fn lock_sdist_url() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio @ https://files.pythonhosted.org/packages/db/4d/3970183622f0330d3c23d9b8a5f52e365e50381fd484d08e3285104333d3/anyio-4.3.0.tar.gz"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -1183,6 +1239,10 @@ fn lock_project_extra() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [project.optional-dependencies]
         test = ["iniconfig"]
         "#,
@@ -1325,6 +1385,10 @@ fn lock_project_with_overrides() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["flask==3.0.0"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         override-dependencies = ["werkzeug==2.3.8"]
         "#,
@@ -1371,7 +1435,7 @@ fn lock_project_with_overrides() -> Result<()> {
     Ok(())
 }
 
-/// Lock a project with a uv.tool.constraint-dependencies.
+/// Lock a project with `uv.tool.constraint-dependencies`.
 #[test]
 fn lock_project_with_constraints() -> Result<()> {
     let context = TestContext::new("3.12");
@@ -1385,6 +1449,10 @@ fn lock_project_with_constraints() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         constraint-dependencies = ["idna<3.4"]
         "#,
@@ -1440,6 +1508,10 @@ fn lock_dependency_extra() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["flask[dotenv]"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -1636,6 +1708,10 @@ fn lock_conditional_dependency_extra() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.7"
         dependencies = ["requests", "requests[socks] ; python_version < '3.10'"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -1918,6 +1994,10 @@ fn lock_dependency_non_existent_extra() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["flask[foo]"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -2100,6 +2180,10 @@ fn lock_upgrade_log() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["markupsafe<2", "iniconfig"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -2177,6 +2261,10 @@ fn lock_upgrade_log() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["markupsafe", "typing-extensions"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -2268,6 +2356,10 @@ fn lock_upgrade_log_multi_version() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["markupsafe<2 ; sys_platform != 'win32'", "markupsafe==2.0.0 ; sys_platform == 'win32'"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -2351,6 +2443,10 @@ fn lock_upgrade_log_multi_version() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["markupsafe"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -2426,6 +2522,10 @@ fn lock_preference() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig<2"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -2482,6 +2582,10 @@ fn lock_preference() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -2597,6 +2701,10 @@ fn lock_git_sha() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["uv-public-pypackage @ git+https://github.com/astral-test/uv-public-pypackage@main"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -2636,6 +2744,10 @@ fn lock_git_sha() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["uv-public-pypackage @ git+https://github.com/astral-test/uv-public-pypackage@main"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -2712,6 +2824,10 @@ fn lock_requires_python() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.7"
         dependencies = ["pygls>=1.1.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -2748,6 +2864,10 @@ fn lock_requires_python() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.7"
         dependencies = ["pygls"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -2899,6 +3019,10 @@ fn lock_requires_python() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.7.9"
         dependencies = ["pygls"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -3040,6 +3164,10 @@ fn lock_requires_python() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["pygls"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -3180,6 +3308,10 @@ fn lock_requires_python_wheels() -> Result<()> {
         version = "0.1.0"
         requires-python = "==3.12.*"
         dependencies = ["frozenlist"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -3263,6 +3395,10 @@ fn lock_requires_python_wheels() -> Result<()> {
         version = "0.1.0"
         requires-python = "==3.11.*"
         dependencies = ["frozenlist"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -3372,6 +3508,10 @@ fn lock_requires_python_star() -> Result<()> {
         version = "0.1.0"
         requires-python = "==3.11.*"
         dependencies = ["linehaul"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -3494,6 +3634,10 @@ fn lock_requires_python_pre() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.11b1"
         dependencies = ["linehaul"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -3614,6 +3758,10 @@ fn lock_requires_python_unbounded() -> Result<()> {
         version = "0.1.0"
         requires-python = "<=3.12"
         dependencies = ["iniconfig"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -3815,6 +3963,10 @@ fn lock_dev() -> Result<()> {
 
         [tool.uv]
         dev-dependencies = ["typing-extensions @ https://files.pythonhosted.org/packages/26/9f/ad63fc0248c5379346306f8668cda6e2e2e9c95e01216d2b8ffd9ff037d0/typing_extensions-4.12.2-py3-none-any.whl"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -3929,6 +4081,10 @@ fn lock_conditional_unconditional() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig", "iniconfig ; python_version < '3.12'"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -4006,6 +4162,10 @@ fn lock_multiple_markers() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig ; implementation_name == 'cpython'", "iniconfig ; python_version < '3.12'"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -4088,8 +4248,8 @@ fn lock_relative_and_absolute_paths() -> Result<()> {
         c = {{ path = '{}' }}
 
         [build-system]
-        requires = ["hatchling"]
-        build-backend = "hatchling.build"
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
         context.temp_dir.join("c").display()
     })?;
@@ -4106,8 +4266,9 @@ fn lock_relative_and_absolute_paths() -> Result<()> {
         license = {text = "MIT"}
 
         [build-system]
-        requires = ["hatchling"]
-        build-backend = "hatchling.build"
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
     "#})?;
     context.temp_dir.child("b/b/__init__.py").touch()?;
     context
@@ -4122,8 +4283,9 @@ fn lock_relative_and_absolute_paths() -> Result<()> {
         license = {text = "MIT"}
 
         [build-system]
-        requires = ["hatchling"]
-        build-backend = "hatchling.build"
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
     "#})?;
     context.temp_dir.child("c/c/__init__.py").touch()?;
 
@@ -4203,6 +4365,10 @@ fn lock_cycles() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["testtools==2.3.0", "fixtures==3.0.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -4406,6 +4572,11 @@ fn lock_new_extras() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["requests==2.31.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
     "#,
     )?;
 
@@ -4529,6 +4700,11 @@ fn lock_new_extras() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["requests[socks]==2.31.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
     "#,
     )?;
 
@@ -4677,6 +4853,10 @@ fn lock_invalid_hash() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -4773,6 +4953,10 @@ fn lock_resolution_mode() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio>=3"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -4951,6 +5135,10 @@ fn lock_requires_python_no_wheels() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["dearpygui==1.9.1"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -4983,6 +5171,10 @@ fn lock_same_version_multiple_urls() -> Result<()> {
         version = "0.0.1"
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -4996,6 +5188,10 @@ fn lock_same_version_multiple_urls() -> Result<()> {
         version = "0.0.1"
         requires-python = ">=3.12"
         dependencies = ["anyio==3.0.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -5168,6 +5364,10 @@ fn lock_unsafe_lowest() -> Result<()> {
         [project.optional-dependencies]
         dev = ["iniconfig"]
         all = ["project[dev]"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -5207,6 +5407,10 @@ fn lock_exclusion() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = []
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.workspace]
         members = []
         exclude = ["child"]
@@ -5225,6 +5429,10 @@ fn lock_exclusion() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["project"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         project = { path = ".." }
         "#,
@@ -5305,6 +5513,10 @@ fn lock_dev_transitive() -> Result<()> {
 
         [tool.uv]
         dev-dependencies = ["anyio"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -5320,6 +5532,10 @@ fn lock_dev_transitive() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["foo", "baz", "iniconfig>1"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         foo = { path = "../foo" }
         baz = { workspace = true }
@@ -5341,6 +5557,10 @@ fn lock_dev_transitive() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = []
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         dev-dependencies = ["typing-extensions>4"]
         "#,
@@ -5464,6 +5684,10 @@ fn lock_redact_https() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -5610,6 +5834,10 @@ fn lock_redact_https() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["iniconfig"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         index-url = "https://public:heron@pypi-proxy.fly.dev/basic-auth/simple"
         "#,
@@ -5652,6 +5880,10 @@ fn lock_redact_git() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["uv-private-pypackage @ git+https://{token}@github.com/astral-test/uv-private-pypackage"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
         token = token,
     })?;
@@ -5737,6 +5969,10 @@ fn lock_relative_index() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["iniconfig"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         index-url = "https://pypi-proxy.fly.dev/relative/simple"
         "#,
@@ -5826,6 +6062,11 @@ fn lock_no_sources() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         anyio = { path = "./anyio" }
         "#,
@@ -5842,6 +6083,10 @@ fn lock_no_sources() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -6010,6 +6255,10 @@ fn lock_migrate() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -6152,6 +6401,10 @@ fn lock_upgrade_package() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio<=2", "idna<=3"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -6246,6 +6499,10 @@ fn lock_upgrade_package() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio", "idna"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -6428,6 +6685,10 @@ fn lock_upgrade_drop_fork_markers() -> Result<()> {
     version = "0.1.0"
     requires-python = ">=3.12"
     dependencies = ["fork-upgrade-foo==1"]
+
+    [build-system]
+        requires = ["flit_core>=3.8,<4"]
+        build-backend = "flit_core.buildapi"
     "#;
 
     let pyproject_toml = context.temp_dir.child("pyproject.toml");
@@ -6470,6 +6731,10 @@ fn lock_warn_missing_transitive_lower_bounds() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["pytest>8"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -6522,6 +6787,10 @@ fn lock_find_links_local_wheel() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["tqdm==1000.0.0"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         find-links = ["{}"]
         "#,
@@ -6636,6 +6905,10 @@ fn lock_find_links_local_sdist() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["tqdm==999.0.0"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         find-links = ["{}"]
         "#,
@@ -6727,6 +7000,10 @@ fn lock_find_links_http_wheel() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["packaging==23.2"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         find-links = ["{}"]
         no-build-package = ["packaging"]
@@ -6818,6 +7095,10 @@ fn lock_find_links_http_sdist() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["packaging==23.2"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         find-links = ["{}"]
         no-binary-package = ["packaging"]
@@ -6944,6 +7225,10 @@ fn lock_local_index() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["tqdm"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         extra-index-url = ["{}"]
         "#,
@@ -7040,6 +7325,10 @@ fn lock_sources_url() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["workspace @ https://github.com/user-attachments/files/16592193/workspace.zip"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -7175,6 +7464,10 @@ fn lock_sources_archive() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["workspace @ {}"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
         Url::from_file_path(&workspace_archive).unwrap(),
     })?;
@@ -7425,6 +7718,10 @@ fn lock_editable() -> Result<()> {
         dependencies = ["library"]
         requires-python = ">=3.12"
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         library = { path = "./library" }
 
@@ -7441,6 +7738,10 @@ fn lock_editable() -> Result<()> {
         version = "0.1.0"
         dependencies = ["library"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         library = { path = "../../library" }
     "#})?;
@@ -7532,6 +7833,10 @@ fn lock_editable() -> Result<()> {
         version = "0.1.0"
         dependencies = ["library"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         library = { path = "../../library", editable = true }
     "#})?;
@@ -7635,6 +7940,10 @@ fn lock_mixed_extras() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["leaf1", "workspace2"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [project.optional-dependencies]
         async = ["typing-extensions>=4"]
 
@@ -7657,6 +7966,10 @@ fn lock_mixed_extras() -> Result<()> {
 
         [project.optional-dependencies]
         async = ["iniconfig>=2"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     leaf1.child("src/__init__.py").touch()?;
 
@@ -7669,6 +7982,10 @@ fn lock_mixed_extras() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["leaf2"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         leaf2 = { workspace = true }
 
@@ -7687,6 +8004,10 @@ fn lock_mixed_extras() -> Result<()> {
 
         [project.optional-dependencies]
         async = ["packaging>=24"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     leaf2.child("src/__init__.py").touch()?;
 
@@ -7855,6 +8176,10 @@ fn lock_transitive_extra() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["leaf"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [project.optional-dependencies]
         async = ["typing-extensions>=4", "leaf[async]"]
 
@@ -7877,6 +8202,10 @@ fn lock_transitive_extra() -> Result<()> {
 
         [project.optional-dependencies]
         async = ["iniconfig>=2"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     leaf.child("src/__init__.py").touch()?;
 
@@ -8060,9 +8389,11 @@ fn lock_mismatched_versions() -> Result<()> {
         name = "project"
         version = "0.1.0"
         requires-python = ">=3.12"
-        dependencies = [
-            "uv-public-pypackage==0.0.2",
-        ]
+        dependencies = ["uv-public-pypackage==0.0.2"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
 
         [tool.uv.sources]
         uv-public-pypackage = { git = "https://github.com/astral-test/uv-public-pypackage", tag = "0.0.1" }
@@ -8153,6 +8484,10 @@ fn unconditional_overlapping_marker_disjoint_version_constraints() -> Result<()>
             "datasets < 2.19",
             "datasets >= 2.19 ; python_version > '3.10'"
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -8182,6 +8517,10 @@ fn lock_change_index() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -8304,6 +8643,10 @@ fn lock_remove_member() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio>3"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -8316,6 +8659,10 @@ fn lock_remove_member() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["leaf"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.workspace]
         members = ["leaf"]
 
@@ -8497,6 +8844,10 @@ fn lock_add_member() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = []
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.workspace]
         members = []
         "#,
@@ -8551,6 +8902,10 @@ fn lock_add_member() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio>3"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -8563,6 +8918,10 @@ fn lock_add_member() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = []
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.workspace]
         members = ["leaf"]
         "#,
@@ -8706,6 +9065,10 @@ fn lock_redundant_add_member() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["anyio"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.workspace]
         members = []
         "#,
@@ -8797,6 +9160,10 @@ fn lock_redundant_add_member() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["anyio", "idna"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.workspace]
         members = []
         "#,
@@ -8903,6 +9270,10 @@ fn lock_new_constraints() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -8992,6 +9363,10 @@ fn lock_new_constraints() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["anyio"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         constraint-dependencies = [
             "anyio < 4.3",
@@ -9097,6 +9472,10 @@ fn lock_remove_member_virtual() -> Result<()> {
         r#"
         [tool.uv.workspace]
         members = ["leaf"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -9109,6 +9488,10 @@ fn lock_remove_member_virtual() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio>3"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -9261,6 +9644,10 @@ fn lock_rename_project() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -9327,6 +9714,10 @@ fn lock_rename_project() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -9405,6 +9796,10 @@ fn lock_missing_metadata() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -9543,6 +9938,10 @@ fn lock_reorder() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio", "iniconfig"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -9644,6 +10043,10 @@ fn lock_reorder() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig", "anyio"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -9672,6 +10075,10 @@ fn lock_narrowed_python_version() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.7"
         dependencies = ["iniconfig"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -9683,6 +10090,11 @@ fn lock_narrowed_python_version() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.7"
         dependencies = ["dependency ; python_version < '3.9'", "dependency ; python_version > '3.10'"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         dependency = { path = "./dependency" }
         "#,
@@ -9787,8 +10199,8 @@ fn lock_exclude_unnecessary_python_forks() -> Result<()> {
             "anyio ; python_version > '3.10'"
         ]
         [build-system]
-        requires = ["hatchling"]
-        build-backend = "hatchling.build"
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -9893,6 +10305,10 @@ fn lock_constrained_environment() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["black"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         environments = "platform_system != 'Windows'"
         "#,
@@ -10037,6 +10453,10 @@ fn lock_constrained_environment() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["black"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         environments = ["platform_system != 'Windows'"]
         "#,
@@ -10061,6 +10481,10 @@ fn lock_constrained_environment() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["black"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -10209,6 +10633,10 @@ fn lock_overlapping_environment() -> Result<()> {
         requires-python = ">=3.8"
         dependencies = ["black"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         environments = ["platform_system != 'Windows'", "python_version > '3.10'"]
         "#,
@@ -10429,9 +10857,7 @@ fn lock_virtual_conditional() -> Result<()> {
         members = []
 
         [tool.uv]
-        dev-dependencies = [
-            "anyio > 3 ; sys_platform == 'linux'",
-        ]
+        dev-dependencies = ["anyio > 3 ; sys_platform == 'linux'"]
         "#,
     )?;
 
@@ -10531,10 +10957,12 @@ fn lock_dropped_dev_extra() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
-        dev-dependencies = [
-            "coverage[toml]"
-        ]
+        dev-dependencies = ["coverage[toml]"]
         "#,
     )?;
 
@@ -10647,6 +11075,10 @@ fn lock_trailing_slash() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         index-url = "https://pypi.org/simple/"
         "#,
@@ -10757,3 +11189,439 @@ fn lock_trailing_slash() -> Result<()> {
 
     Ok(())
 }
+
+/// Lock a project with `virtual = true`.
+#[test]
+fn lock_explicit_virtual_project() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = ["black"]
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+        [tool.uv]
+        virtual = true
+        dev-dependencies = [
+            "anyio"
+        ]
+        "#,
+    )?;
+
+    uv_snapshot!(context.filters(), context.lock(), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 11 packages in [TIME]
+    "###);
+
+    let lock = fs_err::read_to_string(context.temp_dir.join("uv.lock")).unwrap();
+
+    insta::with_settings!({
+        filters => context.filters(),
+    }, {
+        assert_snapshot!(
+            lock, @r###"
+        version = 1
+        requires-python = ">=3.12"
+
+        [options]
+        exclude-newer = "2024-03-25T00:00:00Z"
+
+        [[package]]
+        name = "anyio"
+        version = "4.3.0"
+        source = { registry = "https://pypi.org/simple" }
+        dependencies = [
+            { name = "idna" },
+            { name = "sniffio" },
+        ]
+        sdist = { url = "https://files.pythonhosted.org/packages/db/4d/3970183622f0330d3c23d9b8a5f52e365e50381fd484d08e3285104333d3/anyio-4.3.0.tar.gz", hash = "sha256:f75253795a87df48568485fd18cdd2a3fa5c4f7c5be8e5e36637733fce06fed6", size = 159642 }
+        wheels = [
+            { url = "https://files.pythonhosted.org/packages/14/fd/2f20c40b45e4fb4324834aea24bd4afdf1143390242c0b33774da0e2e34f/anyio-4.3.0-py3-none-any.whl", hash = "sha256:048e05d0f6caeed70d731f3db756d35dcc1f35747c8c403364a8332c630441b8", size = 85584 },
+        ]
+
+        [[package]]
+        name = "black"
+        version = "24.3.0"
+        source = { registry = "https://pypi.org/simple" }
+        dependencies = [
+            { name = "click" },
+            { name = "mypy-extensions" },
+            { name = "packaging" },
+            { name = "pathspec" },
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+        [[package]]
+        name = "project"
+        version = "0.1.0"
+        source = { editable = "." }
+        dependencies = [
+            { name = "black" },
+        ]
+
+        [package.dev-dependencies]
+        dev = [
+            { name = "anyio" },
+        ]
+
+        [package.metadata]
+        requires-dist = [{ name = "black" }]
+
+        [package.metadata.requires-dev]
+        dev = [{ name = "anyio" }]
+
+        [[package]]
+        name = "sniffio"
+        version = "1.3.1"
+        source = { registry = "https://pypi.org/simple" }
+        sdist = { url = "https://files.pythonhosted.org/packages/a2/87/a6771e1546d97e7e041b6ae58d80074f81b7d5121207425c964ddf5cfdbd/sniffio-1.3.1.tar.gz", hash = "sha256:f4324edc670a0f49750a81b895f35c3adb843cca46f0530f79fc1babb23789dc", size = 20372 }
+        wheels = [
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+        ]
+        "###
+        );
+    });
+
+    // Re-run with `--locked`.
+    uv_snapshot!(context.filters(), context.lock().arg("--locked"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 11 packages in [TIME]
+    "###);
+
+    // Re-run with `--offline`. We shouldn't need a network connection to validate an
+    // already-correct lockfile with immutable metadata.
+    uv_snapshot!(context.filters(), context.lock().arg("--locked").arg("--offline").arg("--no-cache"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 11 packages in [TIME]
+    "###);
+
+    // Install from the lockfile. The virtual project should _not_ be installed.
+    uv_snapshot!(context.filters(), context.sync().arg("--frozen"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Prepared 9 packages in [TIME]
+    Installed 9 packages in [TIME]
+     + anyio==4.3.0
+     + black==24.3.0
+     + click==8.1.7
+     + idna==3.6
+     + mypy-extensions==1.0.0
+     + packaging==24.0
+     + pathspec==0.12.1
+     + platformdirs==4.2.0
+     + sniffio==1.3.1
+    "###);
+
+    Ok(())
+}
+
+/// Lock a project that is implicitly virtual (by way of omitting `build-system`0>
+#[test]
+fn lock_implicit_virtual_project() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = ["black"]
+        [tool.uv]
+        dev-dependencies = [
+            "anyio"
+        ]
+        "#,
+    )?;
+
+    uv_snapshot!(context.filters(), context.lock(), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 11 packages in [TIME]
+    "###);
+
+    let lock = fs_err::read_to_string(context.temp_dir.join("uv.lock")).unwrap();
+
+    insta::with_settings!({
+        filters => context.filters(),
+    }, {
+        assert_snapshot!(
+            lock, @r###"
+        version = 1
+        requires-python = ">=3.12"
+
+        [options]
+        exclude-newer = "2024-03-25T00:00:00Z"
+
+        [[package]]
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+        version = "4.3.0"
+        source = { registry = "https://pypi.org/simple" }
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+        sdist = { url = "https://files.pythonhosted.org/packages/96/dc/c1d911bf5bb0fdc58cc05010e9f3efe3b67970cef779ba7fbc3183b987a8/platformdirs-4.2.0.tar.gz", hash = "sha256:ef0cc731df711022c174543cb70a9b5bd22e5a9337c8624ef2c2ceb8ddad8768", size = 20055 }
+        wheels = [
+            { url = "https://files.pythonhosted.org/packages/55/72/4898c44ee9ea6f43396fbc23d9bfaf3d06e01b83698bdf2e4c919deceb7c/platformdirs-4.2.0-py3-none-any.whl", hash = "sha256:0614df2a2f37e1a662acbd8e2b25b92ccf8632929bc6d43467e17fe89c75e068", size = 17717 },
+        ]
+
+        [[package]]
+        name = "project"
+        version = "0.1.0"
+        source = { editable = "." }
+        dependencies = [
+            { name = "black" },
+        ]
+
+        [package.dev-dependencies]
+        dev = [
+            { name = "anyio" },
+        ]
+
+        [package.metadata]
+        requires-dist = [{ name = "black" }]
+
+        [package.metadata.requires-dev]
+        dev = [{ name = "anyio" }]
+
+        [[package]]
+        name = "sniffio"
+        version = "1.3.1"
+        source = { registry = "https://pypi.org/simple" }
+        sdist = { url = "https://files.pythonhosted.org/packages/a2/87/a6771e1546d97e7e041b6ae58d80074f81b7d5121207425c964ddf5cfdbd/sniffio-1.3.1.tar.gz", hash = "sha256:f4324edc670a0f49750a81b895f35c3adb843cca46f0530f79fc1babb23789dc", size = 20372 }
+        wheels = [
+            { url = "https://files.pythonhosted.org/packages/e9/44/75a9c9421471a6c4805dbf2356f7c181a29c1879239abab1ea2cc8f38b40/sniffio-1.3.1-py3-none-any.whl", hash = "sha256:2f6da418d1f1e0fddd844478f41680e794e6051915791a034ff65e5f100525a2", size = 10235 },
+        ]
+        "###
+        );
+    });
+
+    // Re-run with `--locked`.
+    uv_snapshot!(context.filters(), context.lock().arg("--locked"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 11 packages in [TIME]
+    "###);
+
+    // Re-run with `--offline`. We shouldn't need a network connection to validate an
+    // already-correct lockfile with immutable metadata.
+    uv_snapshot!(context.filters(), context.lock().arg("--locked").arg("--offline").arg("--no-cache"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 11 packages in [TIME]
+    "###);
+
+    // Install from the lockfile. The virtual project should _not_ be installed.
+    uv_snapshot!(context.filters(), context.sync().arg("--frozen"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Prepared 9 packages in [TIME]
+    Installed 9 packages in [TIME]
+     + anyio==4.3.0
+     + black==24.3.0
+     + click==8.1.7
+     + idna==3.6
+     + mypy-extensions==1.0.0
+     + packaging==24.0
+     + pathspec==0.12.1
+     + platformdirs==4.2.0
+     + sniffio==1.3.1
+    "###);
+
+    Ok(())
+}
diff --git a/crates/uv/tests/run.rs b/crates/uv/tests/run.rs
index d6e04fa99f016..6e0f59858d691 100644
--- a/crates/uv/tests/run.rs
+++ b/crates/uv/tests/run.rs
@@ -27,6 +27,10 @@ fn run_with_python_version() -> Result<()> {
           "anyio==3.6.0 ; python_version == '3.11'",
           "anyio==3.7.0 ; python_version == '3.12'",
         ]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#
     })?;
     let test_script = context.temp_dir.child("main.py");
@@ -146,6 +150,10 @@ fn run_args() -> Result<()> {
         version = "1.0.0"
         requires-python = ">=3.8"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#
     })?;
 
@@ -201,6 +209,10 @@ fn run_pep723_script() -> Result<()> {
         version = "1.0.0"
         requires-python = ">=3.8"
         dependencies = ["anyio"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#
     })?;
 
@@ -363,6 +375,10 @@ fn run_pythonw_script() -> Result<()> {
         version = "1.0.0"
         requires-python = ">=3.8"
         dependencies = ["anyio"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#
     })?;
 
@@ -473,6 +489,10 @@ fn run_managed_false() -> Result<()> {
         requires-python = ">=3.8"
         dependencies = ["anyio"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         managed = false
         "#
@@ -501,6 +521,10 @@ fn run_with() -> Result<()> {
         version = "1.0.0"
         requires-python = ">=3.8"
         dependencies = ["anyio", "sniffio==1.3.1"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#
     })?;
 
@@ -597,6 +621,10 @@ fn run_with_editable() -> Result<()> {
         version = "1.0.0"
         requires-python = ">=3.8"
         dependencies = ["anyio", "sniffio==1.3.1"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#
     })?;
 
@@ -660,6 +688,10 @@ fn run_with_editable() -> Result<()> {
         requires-python = ">=3.8"
         dependencies = ["anyio", "sniffio==1.3.1"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         anyio = { path = "./src/anyio_local", editable = true }
         "#
@@ -719,6 +751,10 @@ fn run_locked() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -745,6 +781,10 @@ fn run_locked() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -797,6 +837,10 @@ fn run_frozen() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -820,6 +864,10 @@ fn run_frozen() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -853,6 +901,10 @@ fn run_empty_requirements_txt() -> Result<()> {
         version = "1.0.0"
         requires-python = ">=3.8"
         dependencies = ["anyio", "sniffio==1.3.1"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#
     })?;
 
@@ -909,6 +961,10 @@ fn run_requirements_txt() -> Result<()> {
         version = "1.0.0"
         requires-python = ">=3.8"
         dependencies = ["anyio", "sniffio==1.3.1"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#
     })?;
 
@@ -1024,6 +1080,10 @@ fn run_requirements_txt_arguments() -> Result<()> {
         version = "1.0.0"
         requires-python = ">=3.8"
         dependencies = ["typing_extensions"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#
     })?;
 
@@ -1069,15 +1129,15 @@ fn run_editable() -> Result<()> {
 
     let pyproject_toml = context.temp_dir.child("pyproject.toml");
     pyproject_toml.write_str(indoc! { r#"
-        [build-system]
-        requires = ["hatchling"]
-        build-backend = "hatchling.build"
-
         [project]
         name = "foo"
         version = "1.0.0"
         requires-python = ">=3.8"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#
     })?;
 
@@ -1136,6 +1196,10 @@ fn run_from_directory() -> Result<()> {
 
         [project.scripts]
         main = "main:main"
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#
     })?;
     let main_script = project_dir.child("main.py");
@@ -1180,6 +1244,10 @@ fn run_without_output() -> Result<()> {
         version = "1.0.0"
         requires-python = ">=3.8"
         dependencies = ["anyio", "sniffio==1.3.1"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#
     })?;
 
@@ -1219,15 +1287,15 @@ fn run_isolated_python_version() -> Result<()> {
 
     let pyproject_toml = context.temp_dir.child("pyproject.toml");
     pyproject_toml.write_str(indoc! { r#"
-        [build-system]
-        requires = ["hatchling"]
-        build-backend = "hatchling.build"
-
         [project]
         name = "foo"
         version = "1.0.0"
         requires-python = ">=3.8"
         dependencies = ["anyio"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#
     })?;
 
@@ -1318,15 +1386,15 @@ fn run_no_project() -> Result<()> {
 
     let pyproject_toml = context.temp_dir.child("pyproject.toml");
     pyproject_toml.write_str(indoc! { r#"
-        [build-system]
-        requires = ["hatchling"]
-        build-backend = "hatchling.build"
-
         [project]
         name = "foo"
         version = "1.0.0"
         requires-python = ">=3.8"
         dependencies = ["anyio"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#
     })?;
 
diff --git a/crates/uv/tests/sync.rs b/crates/uv/tests/sync.rs
index 28752eead06b9..ffc8e114a5a5c 100644
--- a/crates/uv/tests/sync.rs
+++ b/crates/uv/tests/sync.rs
@@ -21,6 +21,10 @@ fn sync() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -55,6 +59,10 @@ fn locked() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -81,6 +89,10 @@ fn locked() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -115,6 +127,10 @@ fn frozen() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -138,6 +154,10 @@ fn frozen() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -212,6 +232,10 @@ fn package() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["child", "anyio>3"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         child = { workspace = true }
 
@@ -237,6 +261,10 @@ fn package() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig>1"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -312,6 +340,10 @@ fn mixed_requires_python() -> Result<()> {
         name = "bird-feeder"
         version = "0.1.0"
         requires-python = ">=3.8"
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -381,6 +413,10 @@ fn virtual_workspace_dev_dependencies() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["iniconfig>1"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -441,6 +477,10 @@ fn sync_build_isolation() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["source-distribution @ https://files.pythonhosted.org/packages/10/1f/57aa4cce1b1abf6b433106676e15f9fa2c92ed2bd4cf77c3b50a9e9ac773/source_distribution-0.0.1.tar.gz"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -877,6 +917,10 @@ fn sync_environment() -> Result<()> {
         requires-python = ">=3.10"
         dependencies = ["iniconfig"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         environments = ["python_version < '3.11'"]
         "#,
@@ -916,6 +960,10 @@ fn read_metadata_statically_over_the_cache() -> Result<()> {
         requires-python = ">=3.12"
         # Python string sorting is the other way round.
         dependencies = ["anyio>=4,<5"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -945,6 +993,10 @@ fn no_install_project() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
@@ -996,6 +1048,10 @@ fn no_install_workspace() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0", "child"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.workspace]
         members = ["child"]
 
@@ -1015,8 +1071,8 @@ fn no_install_workspace() -> Result<()> {
         dependencies = ["iniconfig>1"]
 
         [build-system]
-        requires = ["hatchling"]
-        build-backend = "hatchling.build"
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
     child
@@ -1073,6 +1129,10 @@ fn no_install_package() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
         "#,
     )?;
 
diff --git a/crates/uv/tests/workspace.rs b/crates/uv/tests/workspace.rs
index b3607331d2795..7f452ba05a6f8 100644
--- a/crates/uv/tests/workspace.rs
+++ b/crates/uv/tests/workspace.rs
@@ -965,6 +965,10 @@ fn workspace_inherit_sources() -> Result<()> {
         dependencies = []
         requires-python = ">=3.12"
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.workspace]
         members = ["packages/*"]
     "#})?;
@@ -977,6 +981,10 @@ fn workspace_inherit_sources() -> Result<()> {
         name = "leaf"
         version = "0.1.0"
         dependencies = ["library"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     leaf.child("src/__init__.py").touch()?;
 
@@ -987,6 +995,10 @@ fn workspace_inherit_sources() -> Result<()> {
         name = "library"
         version = "0.1.0"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     library.child("src/__init__.py").touch()?;
 
@@ -1013,6 +1025,10 @@ fn workspace_inherit_sources() -> Result<()> {
         version = "0.1.0"
         dependencies = ["library"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         library = { path = "../../../library", editable = true }
     "#})?;
@@ -1036,6 +1052,10 @@ fn workspace_inherit_sources() -> Result<()> {
         name = "leaf"
         version = "0.1.0"
         dependencies = ["library"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
 
     // Update the root to include the source.
@@ -1046,6 +1066,10 @@ fn workspace_inherit_sources() -> Result<()> {
         dependencies = []
         requires-python = ">=3.12"
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         library = { path = "../library", editable = true }
 
@@ -1117,6 +1141,10 @@ fn workspace_inherit_sources() -> Result<()> {
         dependencies = []
         requires-python = ">=3.12"
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         library = { path = "../library", editable = true }
 
@@ -1131,9 +1159,12 @@ fn workspace_inherit_sources() -> Result<()> {
         version = "0.1.0"
         dependencies = ["library"]
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.sources]
         application = { path = "../application", editable = true }
-
     "#})?;
 
     // Resolving should succeed; the member should still use the root's source, despite defining
@@ -1167,6 +1198,10 @@ fn workspace_unsatisfiable_member_dependencies() -> Result<()> {
         dependencies = []
         requires-python = ">=3.12"
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.workspace]
         members = ["packages/*"]
     "#})?;
@@ -1179,6 +1214,10 @@ fn workspace_unsatisfiable_member_dependencies() -> Result<()> {
         name = "leaf"
         version = "0.1.0"
         dependencies = ["httpx>9999"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     leaf.child("src/__init__.py").touch()?;
 
@@ -1215,6 +1254,10 @@ fn workspace_unsatisfiable_member_dependencies_conflicting() -> Result<()> {
         dependencies = []
         requires-python = ">=3.12"
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.workspace]
         members = ["packages/*"]
     "#})?;
@@ -1227,6 +1270,10 @@ fn workspace_unsatisfiable_member_dependencies_conflicting() -> Result<()> {
         name = "foo"
         version = "0.1.0"
         dependencies = ["anyio==4.1.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     foo.child("src/__init__.py").touch()?;
     let bar = workspace.child("packages").child("bar");
@@ -1235,6 +1282,10 @@ fn workspace_unsatisfiable_member_dependencies_conflicting() -> Result<()> {
         name = "bar"
         version = "0.1.0"
         dependencies = ["anyio==4.2.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     bar.child("src/__init__.py").touch()?;
 
@@ -1271,6 +1322,10 @@ fn workspace_unsatisfiable_member_dependencies_conflicting_threeway() -> Result<
         dependencies = []
         requires-python = ">=3.12"
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.workspace]
         members = ["packages/*"]
     "#})?;
@@ -1283,6 +1338,10 @@ fn workspace_unsatisfiable_member_dependencies_conflicting_threeway() -> Result<
         name = "red"
         version = "0.1.0"
         dependencies = ["anyio==4.1.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     red.child("src/__init__.py").touch()?;
     let knot = workspace.child("packages").child("knot");
@@ -1291,6 +1350,10 @@ fn workspace_unsatisfiable_member_dependencies_conflicting_threeway() -> Result<
         name = "knot"
         version = "0.1.0"
         dependencies = ["anyio==4.2.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     knot.child("src/__init__.py").touch()?;
 
@@ -1302,6 +1365,10 @@ fn workspace_unsatisfiable_member_dependencies_conflicting_threeway() -> Result<
         name = "bird"
         version = "0.1.0"
         dependencies = ["anyio==4.3.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     bird.child("src/__init__.py").touch()?;
 
@@ -1338,6 +1405,10 @@ fn workspace_unsatisfiable_member_dependencies_conflicting_extra() -> Result<()>
         dependencies = []
         requires-python = ">=3.12"
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.workspace]
         members = ["packages/*"]
     "#})?;
@@ -1350,6 +1421,10 @@ fn workspace_unsatisfiable_member_dependencies_conflicting_extra() -> Result<()>
         name = "foo"
         version = "0.1.0"
         dependencies = ["anyio==4.1.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     foo.child("src/__init__.py").touch()?;
     let bar = workspace.child("packages").child("bar");
@@ -1360,6 +1435,10 @@ fn workspace_unsatisfiable_member_dependencies_conflicting_extra() -> Result<()>
 
         [project.optional-dependencies]
         some_extra = ["anyio==4.2.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     bar.child("src/__init__.py").touch()?;
 
@@ -1396,6 +1475,10 @@ fn workspace_unsatisfiable_member_dependencies_conflicting_dev() -> Result<()> {
         dependencies = []
         requires-python = ">=3.12"
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.workspace]
         members = ["packages/*"]
     "#})?;
@@ -1408,6 +1491,10 @@ fn workspace_unsatisfiable_member_dependencies_conflicting_dev() -> Result<()> {
         name = "foo"
         version = "0.1.0"
         dependencies = ["anyio==4.1.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     foo.child("src/__init__.py").touch()?;
     let bar = workspace.child("packages").child("bar");
@@ -1416,6 +1503,10 @@ fn workspace_unsatisfiable_member_dependencies_conflicting_dev() -> Result<()> {
         name = "bar"
         version = "0.1.0"
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv]
         dev-dependencies = ["anyio==4.2.0"]
     "#})?;
@@ -1455,6 +1546,10 @@ fn workspace_member_name_shadows_dependencies() -> Result<()> {
         dependencies = []
         requires-python = ">=3.12"
 
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
+
         [tool.uv.workspace]
         members = ["packages/*"]
     "#})?;
@@ -1467,6 +1562,10 @@ fn workspace_member_name_shadows_dependencies() -> Result<()> {
         name = "foo"
         version = "0.1.0"
         dependencies = ["anyio==4.1.0"]
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     foo.child("src/__init__.py").touch()?;
 
@@ -1477,6 +1576,10 @@ fn workspace_member_name_shadows_dependencies() -> Result<()> {
         name = "anyio"
         version = "0.1.0"
         dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42", "wheel"]
+        build-backend = "setuptools.build_meta"
     "#})?;
     anyio.child("src/__init__.py").touch()?;
 
diff --git a/docs/reference/cli.md b/docs/reference/cli.md
index 7d9644f6fc652..f05390cbe24e5 100644
--- a/docs/reference/cli.md
+++ b/docs/reference/cli.md
@@ -455,9 +455,11 @@ uv init [OPTIONS] [PATH]
 
 </dd><dt><code>--version</code>, <code>-V</code></dt><dd><p>Display the uv version</p>
 
-</dd><dt><code>--virtual</code></dt><dd><p>Create a virtual workspace instead of a project.</p>
+</dd><dt><code>--virtual</code></dt><dd><p>Create a virtual project, rather than a package.</p>
 
-<p>A virtual workspace does not define project dependencies and cannot be published. Instead, workspace members declare project dependencies. Development dependencies may still be declared.</p>
+<p>A virtual project is a project that is not intended to be built as a Python package, such as a project that only contains scripts or other application code.</p>
+
+<p>Virtual projects themselves are not installed into the Python environment.</p>
 
 </dd></dl>
 
diff --git a/docs/reference/settings.md b/docs/reference/settings.md
index fc9b11a629f55..9b8e599d9149b 100644
--- a/docs/reference/settings.md
+++ b/docs/reference/settings.md
@@ -1010,6 +1010,31 @@ those that are downloaded and installed by uv.
 
 ---
 
+#### [`r#virtual`](#r#virtual) {: #r#virtual }
+
+Whether the project should be considered "virtual".
+
+**Default value**: `true`
+
+**Type**: `bool`
+
+**Example usage**:
+
+=== "pyproject.toml"
+
+    ```toml
+    [tool.uv]
+    virtual = false
+    ```
+=== "uv.toml"
+
+    ```toml
+    
+    virtual = false
+    ```
+
+---
+
 #### [`reinstall`](#reinstall) {: #reinstall }
 
 Reinstall all packages, regardless of whether they're already installed. Implies `refresh`.
diff --git a/uv.schema.json b/uv.schema.json
index 2ba30d6e9d5ff..6518136176dc1 100644
--- a/uv.schema.json
+++ b/uv.schema.json
@@ -379,6 +379,13 @@
         "$ref": "#/definitions/Requirement"
       }
     },
+    "virtual": {
+      "description": "Whether the project should be considered \"virtual\".",
+      "type": [
+        "boolean",
+        "null"
+      ]
+    },
     "workspace": {
       "description": "The workspace definition for the project, if any.",
       "anyOf": [