Add support for global uv python pin (#12115)

These changes add support for

```
uv python pin 3.12 --global 
```

This adds the specified version to a `.python-version` file in the
user-level config directory. uv will now use the user-level version as a
fallback if no version is found in the project directory or its
ancestors.

Closes #4972

Cargo.lock

@@ -4579,6 +4579,7 @@ dependencies = [
  "uv-client",
  "uv-configuration",
  "uv-console",
+ "uv-dirs",
  "uv-dispatch",
  "uv-distribution",
  "uv-distribution-filename",

crates/uv-cli/src/lib.rs

@@ -4676,6 +4676,19 @@ pub struct PythonPinArgs {
     /// `requires-python` constraint.
     #[arg(long, alias = "no-workspace")]
     pub no_project: bool,
+
+    /// Update the global Python version pin.
+    ///
+    /// Writes the pinned Python version to a `.python-version` file in the uv user configuration
+    /// directory: `XDG_CONFIG_HOME/uv` on Linux/macOS and `%APPDATA%/uv` on Windows.
+    ///
+    /// When a local Python version pin is not found in the working directory or an ancestor
+    /// directory, this version will be used instead.
+    ///
+    /// Unlike local version pins, this version is used as the default for commands that mutate
+    /// global state, like `uv tool install`.
+    #[arg(long)]
+    pub global: bool,
 }
 
 #[derive(Args)]

crates/uv-dirs/src/lib.rs

@@ -103,6 +103,13 @@ pub fn user_config_dir() -> Option<PathBuf> {
         .ok()
 }
 
+pub fn user_uv_config_dir() -> Option<PathBuf> {
+    user_config_dir().map(|mut path| {
+        path.push("uv");
+        path
+    })
+}
+
 #[cfg(not(windows))]
 fn locate_system_config_xdg(value: Option<&str>) -> Option<PathBuf> {
     // On Linux and macOS, read the `XDG_CONFIG_DIRS` environment variable.

crates/uv-pypi-types/src/conflicts.rs

@@ -149,8 +149,6 @@ impl Conflicts {
         }
 
         let Ok(topo_nodes) = toposort(&graph, None) else {
-            // FIXME: If we hit a cycle, we are currently bailing and waiting for
-            // more detailed cycle detection downstream. Is this what we want?
             return;
         };
         // Propagate canonical items through the graph and populate substitutions.

crates/uv-python/src/version_files.rs

@@ -4,6 +4,7 @@ use std::path::{Path, PathBuf};
 use fs_err as fs;
 use itertools::Itertools;
 use tracing::debug;
+use uv_dirs::user_uv_config_dir;
 use uv_fs::Simplified;
 
 use crate::PythonRequest;
@@ -69,7 +70,13 @@ impl PythonVersionFile {
         options: &DiscoveryOptions<'_>,
     ) -> Result<Option<Self>, std::io::Error> {
         let Some(path) = Self::find_nearest(working_directory, options) else {
-            return Ok(None);
+            // Not found in directory or its ancestors. Looking in user-level config.
+            return Ok(match user_uv_config_dir() {
+                Some(user_dir) => Self::discover_user_config(user_dir, options)
+                    .await?
+                    .or(None),
+                None => None,
+            });
         };
 
         if options.no_config {
@@ -84,6 +91,22 @@ impl PythonVersionFile {
         Self::try_from_path(path).await
     }
 
+    pub async fn discover_user_config(
+        user_config_working_directory: impl AsRef<Path>,
+        options: &DiscoveryOptions<'_>,
+    ) -> Result<Option<Self>, std::io::Error> {
+        if !options.no_config {
+            if let Some(path) =
+                Self::find_in_directory(user_config_working_directory.as_ref(), options)
+                    .into_iter()
+                    .find(|path| path.is_file())
+            {
+                return Self::try_from_path(path).await;
+            }
+        }
+        Ok(None)
+    }
+
     fn find_nearest(path: impl AsRef<Path>, options: &DiscoveryOptions<'_>) -> Option<PathBuf> {
         path.as_ref()
             .ancestors()

crates/uv-static/src/env_vars.rs

@@ -347,6 +347,12 @@ impl EnvVars {
     /// Path to system-level configuration directory on Windows systems.
     pub const SYSTEMDRIVE: &'static str = "SYSTEMDRIVE";
 
+    /// Path to user-level configuration directory on Windows systems.
+    pub const APPDATA: &'static str = "APPDATA";
+
+    /// Path to root directory of user's profile on Windows systems.
+    pub const USERPROFILE: &'static str = "USERPROFILE";
+
     /// Path to user-level configuration directory on Unix systems.
     pub const XDG_CONFIG_HOME: &'static str = "XDG_CONFIG_HOME";
 

crates/uv/Cargo.toml

@@ -24,6 +24,7 @@ uv-cli = { workspace = true }
 uv-client = { workspace = true }
 uv-configuration = { workspace = true }
 uv-console = { workspace = true }
+uv-dirs = { workspace = true }
 uv-dispatch = { workspace = true }
 uv-distribution = { workspace = true }
 uv-distribution-filename = { workspace = true }

crates/uv/src/commands/python/pin.rs

@@ -7,6 +7,7 @@ use owo_colors::OwoColorize;
 use tracing::debug;
 
 use uv_cache::Cache;
+use uv_dirs::user_uv_config_dir;
 use uv_fs::Simplified;
 use uv_python::{
     EnvironmentPreference, PythonInstallation, PythonPreference, PythonRequest, PythonVersionFile,
@@ -25,6 +26,7 @@ pub(crate) async fn pin(
     resolved: bool,
     python_preference: PythonPreference,
     no_project: bool,
+    global: bool,
     cache: &Cache,
     printer: Printer,
 ) -> Result<ExitStatus> {
@@ -43,8 +45,16 @@ pub(crate) async fn pin(
         }
     };
 
-    let version_file =
-        PythonVersionFile::discover(project_dir, &VersionFileDiscoveryOptions::default()).await;
+    let version_file = if global {
+        if let Some(path) = user_uv_config_dir() {
+            PythonVersionFile::discover_user_config(path, &VersionFileDiscoveryOptions::default())
+                .await
+        } else {
+            Ok(None)
+        }
+    } else {
+        PythonVersionFile::discover(project_dir, &VersionFileDiscoveryOptions::default()).await
+    };
 
     let Some(request) = request else {
         // Display the current pinned Python version
@@ -130,8 +140,16 @@ pub(crate) async fn pin(
 
     let existing = version_file.ok().flatten();
     // TODO(zanieb): Allow updating the discovered version file with an `--update` flag.
-    let new = PythonVersionFile::new(project_dir.join(PYTHON_VERSION_FILENAME))
-        .with_versions(vec![request]);
+    let new = if global {
+        let Some(config_dir) = user_uv_config_dir() else {
+            return Err(anyhow::anyhow!("No user-level config directory found."));
+        };
+        PythonVersionFile::new(config_dir.join(PYTHON_VERSION_FILENAME))
+            .with_versions(vec![request])
+    } else {
+        PythonVersionFile::new(project_dir.join(PYTHON_VERSION_FILENAME))
+            .with_versions(vec![request])
+    };
 
     new.write().await?;
 

crates/uv/src/lib.rs

@@ -1257,6 +1257,7 @@ async fn run(mut cli: Cli) -> Result<ExitStatus> {
                 args.resolved,
                 globals.python_preference,
                 args.no_project,
+                args.global,
                 &cache,
                 printer,
             )

crates/uv/src/settings.rs

@@ -979,6 +979,7 @@ pub(crate) struct PythonPinSettings {
     pub(crate) request: Option<String>,
     pub(crate) resolved: bool,
     pub(crate) no_project: bool,
+    pub(crate) global: bool,
 }
 
 impl PythonPinSettings {
@@ -990,12 +991,14 @@ impl PythonPinSettings {
             no_resolved,
             resolved,
             no_project,
+            global,
         } = args;
 
         Self {
             request,
             resolved: flag(resolved, no_resolved).unwrap_or(false),
             no_project,
+            global,
         }
     }
 }

crates/uv/tests/it/common/mod.rs

@@ -89,6 +89,7 @@ pub struct TestContext {
     pub cache_dir: ChildPath,
     pub python_dir: ChildPath,
     pub home_dir: ChildPath,
+    pub user_config_dir: ChildPath,
     pub bin_dir: ChildPath,
     pub venv: ChildPath,
     pub workspace_root: PathBuf,
@@ -357,6 +358,12 @@ impl TestContext {
         let home_dir = ChildPath::new(root.path()).child("home");
         fs_err::create_dir_all(&home_dir).expect("Failed to create test home directory");
 
+        let user_config_dir = if cfg!(windows) {
+            ChildPath::new(home_dir.path())
+        } else {
+            ChildPath::new(home_dir.path()).child(".config")
+        };
+
         // Canonicalize the temp dir for consistent snapshot behavior
         let canonical_temp_dir = temp_dir.canonicalize().unwrap();
         let venv = ChildPath::new(canonical_temp_dir.join(".venv"));
@@ -472,6 +479,18 @@ impl TestContext {
                 .into_iter()
                 .map(|pattern| (pattern, "[PYTHON_DIR]/".to_string())),
         );
+        let mut uv_user_config_dir = PathBuf::from(user_config_dir.path());
+        uv_user_config_dir.push("uv");
+        filters.extend(
+            Self::path_patterns(&uv_user_config_dir)
+                .into_iter()
+                .map(|pattern| (pattern, "[UV_USER_CONFIG_DIR]/".to_string())),
+        );
+        filters.extend(
+            Self::path_patterns(&user_config_dir)
+                .into_iter()
+                .map(|pattern| (pattern, "[USER_CONFIG_DIR]/".to_string())),
+        );
         filters.extend(
             Self::path_patterns(&home_dir)
                 .into_iter()
@@ -532,6 +551,7 @@ impl TestContext {
             cache_dir,
             python_dir,
             home_dir,
+            user_config_dir,
             bin_dir,
             venv,
             workspace_root,
@@ -606,6 +626,8 @@ impl TestContext {
             .env(EnvVars::COLUMNS, "100")
             .env(EnvVars::PATH, path)
             .env(EnvVars::HOME, self.home_dir.as_os_str())
+            .env(EnvVars::APPDATA, self.home_dir.as_os_str())
+            .env(EnvVars::USERPROFILE, self.home_dir.as_os_str())
             .env(EnvVars::UV_PYTHON_INSTALL_DIR, "")
             // Installations are not allowed by default; see `Self::with_managed_python_dirs`
             .env(EnvVars::UV_PYTHON_DOWNLOADS, "never")
@@ -616,6 +638,7 @@ impl TestContext {
             .env(EnvVars::UV_TEST_NO_CLI_PROGRESS, "1")
             .env_remove(EnvVars::UV_CACHE_DIR)
             .env_remove(EnvVars::UV_TOOL_BIN_DIR)
+            .env_remove(EnvVars::XDG_CONFIG_HOME)
             .current_dir(self.temp_dir.path());
 
         for (key, value) in &self.extra_env {

crates/uv/tests/it/python_pin.rs

@@ -1,6 +1,8 @@
+use std::path::PathBuf;
+
 use crate::common::{uv_snapshot, TestContext};
 use anyhow::Result;
-use assert_fs::fixture::{FileWriteStr, PathChild};
+use assert_fs::fixture::{FileWriteStr, PathChild, PathCreateDir};
 use insta::assert_snapshot;
 use uv_python::{
     platform::{Arch, Os},
@@ -198,6 +200,134 @@ fn python_pin() {
     }
 }
 
+// If there is no project-level `.python-version` file, respect the global pin.
+#[test]
+fn python_pin_global_if_no_local() -> Result<()> {
+    let context: TestContext = TestContext::new_with_versions(&["3.11", "3.12"]);
+    let uv = context.user_config_dir.child("uv");
+    uv.create_dir_all()?;
+
+    // Without arguments, we attempt to read the current pin (which does not exist yet)
+    uv_snapshot!(context.filters(), context.python_pin(), @r###"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: No pinned Python version found
+    "###);
+
+    // Given an argument, we globally pin to that version
+    uv_snapshot!(context.filters(), context.python_pin().arg("3.11").arg("--global"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    Pinned `[UV_USER_CONFIG_DIR]/.python-version` to `3.11`
+
+    ----- stderr -----
+    ");
+
+    // If no local pin, use global.
+    uv_snapshot!(context.filters(), context.python_pin(), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    3.11
+
+    ----- stderr -----
+    "###);
+
+    Ok(())
+}
+
+// If there is a project-level `.python-version` file, it takes precedence over
+// the global pin.
+#[test]
+fn python_pin_global_use_local_if_available() -> Result<()> {
+    let context: TestContext = TestContext::new_with_versions(&["3.11", "3.12"]);
+    let uv = context.user_config_dir.child("uv");
+    uv.create_dir_all()?;
+
+    // Given an argument, we globally pin to that version
+    uv_snapshot!(context.filters(), context.python_pin().arg("3.12").arg("--global"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    Pinned `[UV_USER_CONFIG_DIR]/.python-version` to `3.12`
+
+    ----- stderr -----
+    ");
+
+    // With no local, we get the global pin
+    uv_snapshot!(context.filters(), context.python_pin(), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    3.12
+
+    ----- stderr -----
+    "###);
+
+    let mut global_version_path = PathBuf::from(uv.path());
+    global_version_path.push(PYTHON_VERSION_FILENAME);
+    let global_python_version = context.read(&global_version_path);
+    insta::with_settings!({
+        filters => context.filters(),
+    }, {
+        assert_snapshot!(global_python_version, @r###"
+        3.12
+        "###);
+    });
+
+    // Request Python 3.11 for local .python-version
+    uv_snapshot!(context.filters(), context.python_pin().arg("3.11"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    Pinned `.python-version` to `3.11`
+
+    ----- stderr -----
+    "###);
+
+    // Local should override global
+    uv_snapshot!(context.filters(), context.python_pin(), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    3.11
+
+    ----- stderr -----
+    "###);
+
+    // We should still be able to check global pin
+    uv_snapshot!(context.filters(), context.python_pin().arg("--global"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    3.12
+
+    ----- stderr -----
+    "###);
+
+    // Local .python-version exists and has the right version.
+    let local_python_version = context.read(PYTHON_VERSION_FILENAME);
+    assert_snapshot!(local_python_version, @r###"
+    3.11
+    "###);
+
+    // Global .python-version still exists and has the right version.
+    let global_python_version = context.read(&global_version_path);
+    insta::with_settings!({
+        filters => context.filters(),
+    }, {
+        assert_snapshot!(global_python_version, @r###"
+        3.12
+        "###);
+    });
+
+    Ok(())
+}
+
 /// We do not need a Python interpreter to pin without `--resolved`
 /// (skip on Windows because the snapshot is different and the behavior is not platform dependent)
 #[cfg(unix)]

crates/uv/tests/it/show_settings.rs

@@ -2387,7 +2387,6 @@ fn resolve_top_level() -> anyhow::Result<()> {
     ignore = "Configuration tests are not yet supported on Windows"
 )]
 fn resolve_user_configuration() -> anyhow::Result<()> {
-    // Create a temporary directory to store the user configuration.
     let xdg = assert_fs::TempDir::new().expect("Failed to create temp dir");
     let uv = xdg.child("uv");
     let config = uv.child("uv.toml");
@@ -3618,6 +3617,7 @@ fn invalid_conflicts() -> anyhow::Result<()> {
 #[test]
 fn valid_conflicts() -> anyhow::Result<()> {
     let context = TestContext::new("3.12");
+    let xdg = assert_fs::TempDir::new().expect("Failed to create temp dir");
     let pyproject = context.temp_dir.child("pyproject.toml");
 
     // Write in `pyproject.toml` schema.
@@ -3632,7 +3632,8 @@ fn valid_conflicts() -> anyhow::Result<()> {
             [{extra = "x1"}, {extra = "x2"}],
         ]
     "#})?;
-    uv_snapshot!(context.filters(), add_shared_args(context.lock(), context.temp_dir.path()), @r###"
+    uv_snapshot!(context.filters(), add_shared_args(context.lock(), context.temp_dir.path())
+        .env("XDG_CONFIG_HOME", xdg.path()), @r###"
     success: true
     exit_code: 0
     ----- stdout -----

crates/uv/tests/it/tool_install.rs

@@ -175,6 +175,111 @@ fn tool_install() {
     });
 }
 
+#[test]
+fn tool_install_with_global_python() -> Result<()> {
+    let context = TestContext::new_with_versions(&["3.11", "3.12"])
+        .with_filtered_counts()
+        .with_filtered_exe_suffix();
+    let tool_dir = context.temp_dir.child("tools");
+    let bin_dir = context.temp_dir.child("bin");
+    let uv = context.user_config_dir.child("uv");
+    let versions = uv.child(".python-version");
+    versions.write_str("3.11")?;
+
+    // Install a tool
+    uv_snapshot!(context.filters(), context.tool_install()
+        .arg("flask")
+        .env(EnvVars::UV_TOOL_DIR, tool_dir.as_os_str())
+        .env(EnvVars::XDG_BIN_HOME, bin_dir.as_os_str())
+        .env(EnvVars::PATH, bin_dir.as_os_str()), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved [N] packages in [TIME]
+    Prepared [N] packages in [TIME]
+    Installed [N] packages in [TIME]
+     + blinker==1.7.0
+     + click==8.1.7
+     + flask==3.0.2
+     + itsdangerous==2.1.2
+     + jinja2==3.1.3
+     + markupsafe==2.1.5
+     + werkzeug==3.0.1
+    Installed 1 executable: flask
+    "###);
+
+    tool_dir.child("flask").assert(predicate::path::is_dir());
+    assert!(bin_dir
+        .child(format!("flask{}", std::env::consts::EXE_SUFFIX))
+        .exists());
+
+    uv_snapshot!(context.filters(), Command::new("flask").arg("--version").env(EnvVars::PATH, bin_dir.as_os_str()), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    Python 3.11.[X]
+    Flask 3.0.2
+    Werkzeug 3.0.1
+
+    ----- stderr -----
+    "###);
+
+    // Change global version
+    uv_snapshot!(context.filters(), context.python_pin().arg("3.12").arg("--global"),
+        @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    Updated `[UV_USER_CONFIG_DIR]/.python-version` from `3.11` -> `3.12`
+
+    ----- stderr -----
+    "
+    );
+
+    // Install flask again
+    uv_snapshot!(context.filters(), context.tool_install()
+        .arg("flask")
+        .arg("--reinstall")
+        .env(EnvVars::UV_TOOL_DIR, tool_dir.as_os_str())
+        .env(EnvVars::XDG_BIN_HOME, bin_dir.as_os_str())
+        .env(EnvVars::PATH, bin_dir.as_os_str()), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved [N] packages in [TIME]
+    Prepared [N] packages in [TIME]
+    Uninstalled [N] packages in [TIME]
+    Installed [N] packages in [TIME]
+     ~ blinker==1.7.0
+     ~ click==8.1.7
+     ~ flask==3.0.2
+     ~ itsdangerous==2.1.2
+     ~ jinja2==3.1.3
+     ~ markupsafe==2.1.5
+     ~ werkzeug==3.0.1
+    Installed 1 executable: flask
+    ");
+
+    // Currently, when reinstalling a tool we use the original version the tool
+    // was installed with, not the most up-to-date global version
+    uv_snapshot!(context.filters(), Command::new("flask").arg("--version").env(EnvVars::PATH, bin_dir.as_os_str()), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    Python 3.11.[X]
+    Flask 3.0.2
+    Werkzeug 3.0.1
+
+    ----- stderr -----
+    "###);
+
+    Ok(())
+}
+
 #[test]
 fn tool_install_with_editable() -> Result<()> {
     let context = TestContext::new("3.12")
@@ -1471,7 +1576,7 @@ fn tool_install_uninstallable() {
         .arg("pyenv")
         .env(EnvVars::UV_TOOL_DIR, tool_dir.as_os_str())
         .env(EnvVars::XDG_BIN_HOME, bin_dir.as_os_str())
-        .env(EnvVars::PATH, bin_dir.as_os_str()), @r###"
+        .env(EnvVars::PATH, bin_dir.as_os_str()), @r"
     success: false
     exit_code: 1
     ----- stdout -----
@@ -1499,7 +1604,7 @@ fn tool_install_uninstallable() {
 
 
           hint: This usually indicates a problem with the package or the build environment.
-    "###);
+    ");
 
     // Ensure the tool environment is not created.
     tool_dir.child("pyenv").assert(predicate::path::missing());

docs/concepts/python-versions.md

@@ -52,16 +52,20 @@ This behavior can be
 ### Python version files
 
 The `.python-version` file can be used to create a default Python version request. uv searches for a
-`.python-version` file in the working directory and each of its parents. Any of the request formats
-described above can be used, though use of a version number is recommended for interoperability with
-other tools.
+`.python-version` file in the working directory and each of its parents. If none is found, uv will
+check the user-level configuration directory. Any of the request formats described above can be
+used, though use of a version number is recommended for interoperability with other tools.
 
 A `.python-version` file can be created in the current directory with the
 [`uv python pin`](../reference/cli.md/#uv-python-pin) command.
 
+A global `.python-version` file can be created in the user configuration directory with the
+[`uv python pin --global`](../reference/cli.md/#uv-python-pin) command.
+
 Discovery of `.python-version` files can be disabled with `--no-config`.
 
-uv will not search for `.python-version` files beyond project or workspace boundaries.
+uv will not search for `.python-version` files beyond project or workspace boundaries (with the
+exception of the user configuration directory).
 
 ## Installing a Python version
 

docs/configuration/environment.md

@@ -407,6 +407,10 @@ Used for trusted publishing via `uv publish`. Contains the oidc token url.
 
 General proxy for all network requests.
 
+### `APPDATA`
+
+Path to user-level configuration directory on Windows systems.
+
 ### `BASH_VERSION`
 
 Used to detect Bash shell usage.
@@ -567,6 +571,10 @@ Path to system-level configuration directory on Windows systems.
 
 Use to create the tracing durations file via the `tracing-durations-export` feature.
 
+### `USERPROFILE`
+
+Path to root directory of user's profile on Windows systems.
+
 ### `UV`
 
 The path to the binary that was used to invoke uv.

docs/reference/cli.md

@@ -5186,6 +5186,14 @@ uv python pin [OPTIONS] [REQUEST]
 
 <p>See <code>--project</code> to only change the project root directory.</p>
 
+</dd><dt id="uv-python-pin--global"><a href="#uv-python-pin--global"><code>--global</code></a></dt><dd><p>Update the global Python version pin.</p>
+
+<p>Writes the pinned Python version to a <code>.python-version</code> file in the uv user configuration directory: <code>XDG_CONFIG_HOME/uv</code> on Linux/macOS and <code>%APPDATA%/uv</code> on Windows.</p>
+
+<p>When a local Python version pin is not found in the working directory or an ancestor directory, this version will be used instead.</p>
+
+<p>Unlike local version pins, this version is used as the default for commands that mutate global state, like <code>uv tool install</code>.</p>
+
 </dd><dt id="uv-python-pin--help"><a href="#uv-python-pin--help"><code>--help</code></a>, <code>-h</code></dt><dd><p>Display the concise help for this command</p>
 
 </dd><dt id="uv-python-pin--native-tls"><a href="#uv-python-pin--native-tls"><code>--native-tls</code></a></dt><dd><p>Whether to load TLS certificates from the platform&#8217;s native certificate store.</p>