Add --exact flag to uv run

crates/uv-cli/src/lib.rs

@@ -2718,6 +2718,17 @@ pub struct RunArgs {
     #[arg(long)]
     pub no_editable: bool,
 
+    /// Do not remove extraneous packages present in the environment.
+    #[arg(long, overrides_with("exact"), alias = "no-exact", hide = true)]
+    pub inexact: bool,
+
+    /// Perform an exact sync, removing extraneous packages.
+    ///
+    /// When enabled, uv will remove any extraneous packages from the environment.
+    /// By default, `uv run` will make the minimum necessary changes to satisfy the requirements.
+    #[arg(long, overrides_with("inexact"))]
+    pub exact: bool,
+
     /// Load environment variables from a `.env` file.
     ///
     /// Can be provided multiple times, with subsequent files overriding values defined in

crates/uv/src/commands/project/run.rs

@@ -74,6 +74,7 @@ pub(crate) async fn run(
     extras: ExtrasSpecification,
     dev: DevGroupsSpecification,
     editable: EditableMode,
+    modifications: Modifications,
     python: Option<String>,
     install_mirrors: PythonInstallMirrors,
     settings: ResolverInstallerSettings,
@@ -705,7 +706,7 @@ pub(crate) async fn run(
                     &dev.with_defaults(defaults),
                     editable,
                     install_options,
-                    Modifications::Sufficient,
+                    modifications,
                     settings.as_ref().into(),
                     if show_resolution {
                         Box::new(DefaultInstallLogger)

crates/uv/src/lib.rs

@@ -1414,6 +1414,7 @@ async fn run_project(
                 args.extras,
                 args.dev,
                 args.editable,
+                args.modifications,
                 args.python,
                 args.install_mirrors,
                 args.settings,

crates/uv/src/settings.rs

@@ -262,6 +262,7 @@ pub(crate) struct RunSettings {
     pub(crate) extras: ExtrasSpecification,
     pub(crate) dev: DevGroupsSpecification,
     pub(crate) editable: EditableMode,
+    pub(crate) modifications: Modifications,
     pub(crate) with: Vec<String>,
     pub(crate) with_editable: Vec<String>,
     pub(crate) with_requirements: Vec<PathBuf>,
@@ -297,6 +298,8 @@ impl RunSettings {
             module: _,
             only_dev,
             no_editable,
+            inexact,
+            exact,
             script: _,
             gui_script: _,
             command: _,
@@ -336,6 +339,11 @@ impl RunSettings {
                 dev, no_dev, only_dev, group, no_group, only_group, all_groups,
             ),
             editable: EditableMode::from_args(no_editable),
+            modifications: if flag(exact, inexact).unwrap_or(false) {
+                Modifications::Exact
+            } else {
+                Modifications::Sufficient
+            },
             with: with
                 .into_iter()
                 .flat_map(CommaSeparatedRequirements::into_iter)

crates/uv/tests/it/run.rs

@@ -196,7 +196,8 @@ fn run_args() -> Result<()> {
     Ok(())
 }
 
-/// Run without specifying any argunments.
+/// Run without specifying any arguments.
+///
 /// This should list the available scripts.
 #[test]
 fn run_no_args() -> Result<()> {
@@ -807,6 +808,75 @@ fn run_managed_false() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn run_exact() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(indoc! { r#"
+        [project]
+        name = "foo"
+        version = "1.0.0"
+        requires-python = ">=3.8"
+        dependencies = ["iniconfig"]
+        "#
+    })?;
+
+    uv_snapshot!(context.filters(), context.run().arg("python").arg("-c").arg("import iniconfig"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 2 packages in [TIME]
+    Prepared 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + iniconfig==2.0.0
+    "###);
+
+    // Remove `iniconfig`.
+    pyproject_toml.write_str(indoc! { r#"
+        [project]
+        name = "foo"
+        version = "1.0.0"
+        requires-python = ">=3.8"
+        dependencies = ["anyio"]
+        "#
+    })?;
+
+    // By default, `uv run` uses inexact semantics, so both `iniconfig` and `anyio` should still be available.
+    uv_snapshot!(context.filters(), context.run().arg("python").arg("-c").arg("import iniconfig; import anyio"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 6 packages in [TIME]
+    Prepared 3 packages in [TIME]
+    Installed 3 packages in [TIME]
+     + anyio==4.3.0
+     + idna==3.6
+     + sniffio==1.3.1
+    "###);
+
+    // But under `--exact`, `iniconfig` should not be available.
+    uv_snapshot!(context.filters(), context.run().arg("--exact").arg("python").arg("-c").arg("import iniconfig"), @r###"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 6 packages in [TIME]
+    Uninstalled 1 package in [TIME]
+     - iniconfig==2.0.0
+    Traceback (most recent call last):
+      File "<string>", line 1, in <module>
+    ModuleNotFoundError: No module named 'iniconfig'
+    "###);
+
+    Ok(())
+}
+
 #[test]
 fn run_with() -> Result<()> {
     let context = TestContext::new("3.12");

docs/reference/cli.md

@@ -148,6 +148,10 @@ uv run [OPTIONS] [COMMAND]
 <p>Can be provided multiple times, with subsequent files overriding values defined in previous files.</p>
 
 <p>May also be set with the <code>UV_ENV_FILE</code> environment variable.</p>
+</dd><dt><code>--exact</code></dt><dd><p>Perform an exact sync, removing extraneous packages.</p>
+
+<p>When enabled, uv will remove any extraneous packages from the environment. By default, <code>uv run</code> will make the minimum necessary changes to satisfy the requirements.</p>
+
 </dd><dt><code>--exclude-newer</code> <i>exclude-newer</i></dt><dd><p>Limit candidate packages to those that were uploaded prior to the given date.</p>
 
 <p>Accepts both RFC 3339 timestamps (e.g., <code>2006-12-02T02:07:43Z</code>) and local dates in the same format (e.g., <code>2006-12-02</code>) in your system&#8217;s configured time zone.</p>