allow toml pass preview features in list

crates/uv-settings/src/lib.rs

@@ -297,6 +297,7 @@ fn warn_uv_toml_masked_fields(options: &Options) {
                 no_cache,
                 cache_dir,
                 preview,
+                preview_features,
                 python_preference,
                 python_downloads,
                 concurrent_downloads,
@@ -389,6 +390,9 @@ fn warn_uv_toml_masked_fields(options: &Options) {
     if preview.is_some() {
         masked_fields.push("preview");
     }
+    if preview_features.is_some() {
+        masked_fields.push("preview-features");
+    }
     if python_preference.is_some() {
         masked_fields.push("python-preference");
     }

crates/uv-settings/src/settings.rs

@@ -257,6 +257,17 @@ pub struct GlobalOptions {
         "#
     )]
     pub preview: Option<bool>,
+    /// Enable experimental preview features.
+    /// Preview features may change without warning.
+    /// Use comma-separated values or pass multiple times to enable multiple features.
+    #[option(
+        default = "[]",
+        value_type = "list[str]",
+        example = r#"
+            preview-features = ["json-output", "format"]
+        "#
+    )]
+    pub preview_features: Option<Vec<String>>,
     /// Whether to prefer using Python installations that are already present on the system, or
     /// those that are downloaded and installed by uv.
     #[option(
@@ -2050,6 +2061,7 @@ pub struct OptionsWire {
     no_cache: Option<bool>,
     cache_dir: Option<PathBuf>,
     preview: Option<bool>,
+    preview_features: Option<Vec<String>>,
     python_preference: Option<PythonPreference>,
     python_downloads: Option<PythonDownloads>,
     concurrent_downloads: Option<NonZeroUsize>,
@@ -2144,6 +2156,7 @@ impl From<OptionsWire> for Options {
             no_cache,
             cache_dir,
             preview,
+            preview_features,
             python_preference,
             python_downloads,
             python_install_mirror,
@@ -2215,6 +2228,7 @@ impl From<OptionsWire> for Options {
                 no_cache,
                 cache_dir,
                 preview,
+                preview_features,
                 python_preference,
                 python_downloads,
                 concurrent_downloads,

crates/uv/src/settings.rs

@@ -137,13 +137,48 @@ impl GlobalSettings {
                     .unwrap_or_else(Concurrency::threads),
             },
             show_settings: args.show_settings,
-            preview: Preview::from_args(
-                flag(args.preview, args.no_preview, "preview")
-                    .combine(workspace.and_then(|workspace| workspace.globals.preview))
-                    .unwrap_or(false),
-                args.no_preview,
-                &args.preview_features,
-            ),
+            preview: {
+                // Start with command line features (highest precedence)
+                let mut all_preview_features = args.preview_features.clone();
+
+                // Add environment variable features if no command line features were specified
+                if all_preview_features.is_empty() {
+                    if let Ok(env_value) = std::env::var(EnvVars::UV_PREVIEW_FEATURES) {
+                        let env_features = env_value
+                            .split(',')
+                            .map(|feature| feature.trim().to_string())
+                            .filter(|feature| !feature.is_empty())
+                            .collect::<Vec<_>>();
+
+                        for feature in env_features {
+                            if let Ok(parsed) = feature.parse::<uv_preview::PreviewFeatures>() {
+                                all_preview_features.push(parsed);
+                            }
+                        }
+                    }
+                }
+
+                // Add configuration features if no command line or environment features were specified
+                if all_preview_features.is_empty() {
+                    if let Some(config_features) =
+                        workspace.and_then(|workspace| workspace.globals.preview_features.as_ref())
+                    {
+                        for feature in config_features {
+                            if let Ok(parsed) = feature.parse::<uv_preview::PreviewFeatures>() {
+                                all_preview_features.push(parsed);
+                            }
+                        }
+                    }
+                }
+
+                Preview::from_args(
+                    flag(args.preview, args.no_preview, "preview")
+                        .combine(workspace.and_then(|workspace| workspace.globals.preview))
+                        .unwrap_or(false),
+                    args.no_preview,
+                    &all_preview_features,
+                )
+            },
             python_preference,
             python_downloads: flag(
                 args.allow_python_downloads,

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

@@ -144,6 +144,66 @@ impl TestContext {
         self
     }
 
+    /// Set the "concurrent builds" for all commands in this context.
+    pub fn with_concurrent_builds(mut self, concurrent_builds: &str) -> Self {
+        self.extra_env.push((
+            EnvVars::UV_CONCURRENT_BUILDS.into(),
+            concurrent_builds.into(),
+        ));
+        self
+    }
+
+    /// Set the "concurrent downloads" for all commands in this context.
+    pub fn with_concurrent_downloads(mut self, concurrent_downloads: &str) -> Self {
+        self.extra_env.push((
+            EnvVars::UV_CONCURRENT_DOWNLOADS.into(),
+            concurrent_downloads.into(),
+        ));
+        self
+    }
+
+    /// Set the "link mode" for all commands in this context.
+    pub fn with_link_mode(mut self, link_mode: &str) -> Self {
+        self.extra_env
+            .push((EnvVars::UV_LINK_MODE.into(), link_mode.into()));
+        self
+    }
+
+    /// Set the "http retries" for all commands in this context.
+    pub fn with_http_retries(mut self, http_retries: &str) -> Self {
+        self.extra_env
+            .push((EnvVars::UV_HTTP_RETRIES.into(), http_retries.into()));
+        self
+    }
+
+    /// Set the "color" preference for all commands in this context.
+    pub fn with_color(mut self, color: &str) -> Self {
+        // Color is controlled by NO_COLOR, FORCE_COLOR, and CLICOLOR_FORCE environment variables
+        // See: crates/uv/src/settings.rs GlobalSettings::resolve
+        match color.to_lowercase().as_str() {
+            "never" => {
+                self.extra_env.push((EnvVars::NO_COLOR.into(), "1".into()));
+            }
+            "always" => {
+                self.extra_env
+                    .push((EnvVars::FORCE_COLOR.into(), "1".into()));
+            }
+            "auto" => {
+                // Auto is the default behavior, but we explicitly remove color-related env vars
+                // to ensure consistent behavior across environments
+                self.extra_env.push((EnvVars::NO_COLOR.into(), "".into()));
+                self.extra_env
+                    .push((EnvVars::FORCE_COLOR.into(), "".into()));
+                self.extra_env
+                    .push((EnvVars::CLICOLOR_FORCE.into(), "".into()));
+            }
+            _ => {
+                panic!("Invalid color value: {color}. Use 'never', 'always', or 'auto'");
+            }
+        }
+        self
+    }
+
     /// Add extra standard filtering for messages like "Resolved 10 packages" which
     /// can differ between platforms.
     ///