diff --git a/src/cli/install.rs b/src/cli/install.rs
index eaedb7400..16757ff69 100644
--- a/src/cli/install.rs
+++ b/src/cli/install.rs
@@ -1,6 +1,5 @@
 use crate::config::ConfigCli;
 use crate::environment::get_up_to_date_prefix;
-use crate::project::manifest::EnvironmentName;
 use crate::Project;
 use clap::Parser;
 use indexmap::IndexMap;
@@ -26,10 +25,7 @@ pub struct Args {
 pub async fn execute(args: Args) -> miette::Result<()> {
     let project =
         Project::load_or_else_discover(args.manifest_path.as_deref())?.with_cli_config(args.config);
-    let environment_name = EnvironmentName::from_arg_or_env_var(args.environment);
-    let environment = project
-        .environment(&environment_name)
-        .ok_or_else(|| miette::miette!("unknown environment '{environment_name}'"))?;
+    let environment = project.environment_from_name_or_env_var(args.environment)?;
 
     get_up_to_date_prefix(
         &environment,
diff --git a/src/cli/list.rs b/src/cli/list.rs
index 77b693bca..8e5f3f553 100644
--- a/src/cli/list.rs
+++ b/src/cli/list.rs
@@ -12,7 +12,6 @@ use serde::Serialize;
 use uv_distribution::RegistryWheelIndex;
 
 use crate::lock_file::{UpdateLockFileOptions, UvResolutionContext};
-use crate::project::manifest::EnvironmentName;
 use crate::pypi_tags::{get_pypi_tags, is_python_record};
 use crate::Project;
 
@@ -107,10 +106,7 @@ where
 
 pub async fn execute(args: Args) -> miette::Result<()> {
     let project = Project::load_or_else_discover(args.manifest_path.as_deref())?;
-    let environment_name = EnvironmentName::from_arg_or_env_var(args.environment);
-    let environment = project
-        .environment(&environment_name)
-        .ok_or_else(|| miette::miette!("unknown environment '{environment_name}'"))?;
+    let environment = project.environment_from_name_or_env_var(args.environment)?;
 
     let lock_file = project
         .up_to_date_lock_file(UpdateLockFileOptions {
@@ -209,8 +205,8 @@ pub async fn execute(args: Args) -> miette::Result<()> {
         // print packages as json
         json_packages(&packages_to_output, args.json_pretty);
     } else {
-        if !environment_name.is_default() {
-            eprintln!("Environment: {}", environment_name.fancy_display());
+        if !environment.is_default() {
+            eprintln!("Environment: {}", environment.name().fancy_display());
         }
 
         // print packages as table
diff --git a/src/cli/shell.rs b/src/cli/shell.rs
index f70fbd1da..ac4b4e81d 100644
--- a/src/cli/shell.rs
+++ b/src/cli/shell.rs
@@ -203,14 +203,11 @@ async fn start_nu_shell(
 pub async fn execute(args: Args) -> miette::Result<()> {
     let project =
         Project::load_or_else_discover(args.manifest_path.as_deref())?.with_cli_config(args.config);
-    let environment_name = EnvironmentName::from_arg_or_env_var(args.environment);
-    let environment = project
-        .environment(&environment_name)
-        .ok_or_else(|| miette::miette!("unknown environment '{environment_name}'"))?;
+    let environment = project.environment_from_name_or_env_var(args.environment)?;
 
     verify_current_platform_has_required_virtual_packages(&environment).into_diagnostic()?;
 
-    let prompt_name = match environment_name {
+    let prompt_name = match environment.name() {
         EnvironmentName::Default => project.name().to_string(),
         EnvironmentName::Named(name) => format!("{}:{}", project.name(), name),
     };
diff --git a/src/cli/task.rs b/src/cli/task.rs
index cb33688ac..089bda46e 100644
--- a/src/cli/task.rs
+++ b/src/cli/task.rs
@@ -1,10 +1,9 @@
-use crate::project::manifest::{EnvironmentName, FeatureName};
+use crate::project::manifest::FeatureName;
 use crate::task::{quote, Alias, CmdArgs, Execute, Task, TaskName};
 use crate::Project;
 use clap::Parser;
 use indexmap::IndexMap;
 use itertools::Itertools;
-use miette::miette;
 use rattler_conda_types::Platform;
 use std::error::Error;
 use std::path::PathBuf;
@@ -274,10 +273,8 @@ pub fn execute(args: Args) -> miette::Result<()> {
             );
         }
         Operation::List(args) => {
-            let env = EnvironmentName::from_arg_or_env_var(args.environment);
-            let tasks = project
-                .environment(&env)
-                .ok_or(miette!("Environment `{}` not found in project", env))?
+            let environment = project.environment_from_name_or_env_var(args.environment)?;
+            let tasks = environment
                 .tasks(Some(Platform::current()), true)?
                 .into_keys()
                 .collect_vec();
diff --git a/src/cli/tree.rs b/src/cli/tree.rs
index 3c1e9433c..c156c212d 100644
--- a/src/cli/tree.rs
+++ b/src/cli/tree.rs
@@ -7,7 +7,6 @@ use itertools::Itertools;
 use rattler_conda_types::Platform;
 
 use crate::lock_file::UpdateLockFileOptions;
-use crate::project::manifest::EnvironmentName;
 use crate::Project;
 
 /// Show a tree of project dependencies
@@ -70,10 +69,7 @@ static UTF8_SYMBOLS: Symbols = Symbols {
 
 pub async fn execute(args: Args) -> miette::Result<()> {
     let project = Project::load_or_else_discover(args.manifest_path.as_deref())?;
-    let environment_name = EnvironmentName::from_arg_or_env_var(args.environment);
-    let environment = project
-        .environment(&environment_name)
-        .ok_or_else(|| miette::miette!("unknown environment '{environment_name}'"))?;
+    let environment = project.environment_from_name_or_env_var(args.environment)?;
     let lock_file = project
         .up_to_date_lock_file(UpdateLockFileOptions {
             lock_file_usage: args.lock_file_usage.into(),
@@ -92,8 +88,8 @@ pub async fn execute(args: Args) -> miette::Result<()> {
 
     let direct_deps = direct_dependencies(&environment, &platform, &dep_map);
 
-    if !environment_name.is_default() {
-        eprintln!("Environment: {}", environment_name.fancy_display());
+    if !environment.is_default() {
+        eprintln!("Environment: {}", environment.name().fancy_display());
     }
 
     if args.invert {
diff --git a/src/project/manifest/environment.rs b/src/project/manifest/environment.rs
index cf1c53e89..680e14a8b 100644
--- a/src/project/manifest/environment.rs
+++ b/src/project/manifest/environment.rs
@@ -46,18 +46,20 @@ impl EnvironmentName {
 
     /// Tries to read the environment name from an argument, then it will try
     /// to read from an environment variable, otherwise it will fall back to default
-    pub fn from_arg_or_env_var(arg_name: Option<String>) -> Self {
+    pub fn from_arg_or_env_var(
+        arg_name: Option<String>,
+    ) -> Result<Self, ParseEnvironmentNameError> {
         if let Some(arg_name) = arg_name {
-            return EnvironmentName::Named(arg_name);
+            return EnvironmentName::from_str(&arg_name);
         } else if std::env::var("PIXI_IN_SHELL").is_ok() {
             if let Ok(env_var_name) = std::env::var("PIXI_ENVIRONMENT_NAME") {
                 if env_var_name == consts::DEFAULT_ENVIRONMENT_NAME {
-                    return EnvironmentName::Default;
+                    return Ok(EnvironmentName::Default);
                 }
-                return EnvironmentName::Named(env_var_name);
+                return Ok(EnvironmentName::Named(env_var_name));
             }
         }
-        EnvironmentName::Default
+        Ok(EnvironmentName::Default)
     }
 }
 
diff --git a/src/project/mod.rs b/src/project/mod.rs
index f00fad482..a75431dcc 100644
--- a/src/project/mod.rs
+++ b/src/project/mod.rs
@@ -333,6 +333,16 @@ impl Project {
             .collect()
     }
 
+    /// Returns an environment in this project based on a name or an environment variable.
+    pub fn environment_from_name_or_env_var(
+        &self,
+        name: Option<String>,
+    ) -> miette::Result<Environment> {
+        let environment_name = EnvironmentName::from_arg_or_env_var(name).into_diagnostic()?;
+        self.environment(&environment_name)
+            .ok_or_else(|| miette::miette!("unknown environment '{environment_name}'"))
+    }
+
     /// Returns all the solve groups in the project.
     pub fn solve_groups(&self) -> Vec<SolveGroup> {
         self.manifest