Add environment provider snapshot (#20058)

## Summary
- Change `EnvironmentProvider` to return concrete `Environment`
instances instead of `EnvironmentConfigurations`.
- Make `DefaultEnvironmentProvider` provide the provider-visible `local`
environment plus optional `remote` environment from
`CODEX_EXEC_SERVER_URL`.
- Keep `EnvironmentManager` as the concrete cache while exposing its own
explicit local environment for `local_environment()` fallback paths.

## Validation
- `just fmt`
- `git diff --check`

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/core/src/connectors.rs

@@ -201,7 +201,7 @@ pub async fn list_accessible_connectors_from_mcp_tools_with_options_and_status(
         config.codex_linux_sandbox_exe.clone(),
     )?;
     let environment_manager =
-        EnvironmentManager::new(EnvironmentManagerArgs::from_env(local_runtime_paths));
+        EnvironmentManager::new(EnvironmentManagerArgs::new(local_runtime_paths)).await;
     list_accessible_connectors_from_mcp_tools_with_environment_manager(
         config,
         force_refetch,

codex-rs/core/src/environment_selection.rs

@@ -61,7 +61,6 @@ pub(crate) fn selected_primary_environment(
 
 #[cfg(test)]
 mod tests {
-    use codex_exec_server::EnvironmentManagerArgs;
     use codex_exec_server::ExecServerRuntimePaths;
     use codex_exec_server::REMOTE_ENVIRONMENT_ID;
     use codex_protocol::protocol::TurnEnvironmentSelection;
@@ -81,10 +80,11 @@ mod tests {
     #[tokio::test]
     async fn default_thread_environment_selections_use_manager_default_id() {
         let cwd = AbsolutePathBuf::current_dir().expect("cwd");
-        let manager = EnvironmentManager::new(EnvironmentManagerArgs {
-            exec_server_url: Some("ws://127.0.0.1:8765".to_string()),
-            local_runtime_paths: test_runtime_paths(),
-        });
+        let manager = EnvironmentManager::create_for_tests(
+            Some("ws://127.0.0.1:8765".to_string()),
+            test_runtime_paths(),
+        )
+        .await;
 
         assert_eq!(
             default_thread_environment_selections(&manager, &cwd),
@@ -98,10 +98,7 @@ mod tests {
     #[tokio::test]
     async fn default_thread_environment_selections_empty_when_default_disabled() {
         let cwd = AbsolutePathBuf::current_dir().expect("cwd");
-        let manager = EnvironmentManager::new(EnvironmentManagerArgs {
-            exec_server_url: Some("none".to_string()),
-            local_runtime_paths: test_runtime_paths(),
-        });
+        let manager = EnvironmentManager::disabled_for_tests(test_runtime_paths());
 
         assert_eq!(
             default_thread_environment_selections(&manager, &cwd),

codex-rs/core/src/prompt_debug.rs

@@ -45,9 +45,7 @@ pub async fn build_prompt_input(
                 .features
                 .enabled(Feature::DefaultModeRequestUserInput),
         },
-        Arc::new(EnvironmentManager::new(EnvironmentManagerArgs::from_env(
-            local_runtime_paths,
-        ))),
+        Arc::new(EnvironmentManager::new(EnvironmentManagerArgs::new(local_runtime_paths)).await),
         /*analytics_events_client*/ None,
     );
     let thread = thread_manager.start_thread(config).await?;

codex-rs/core/src/thread_manager_tests.rs

@@ -47,20 +47,6 @@ fn assistant_msg(text: &str) -> ResponseItem {
     }
 }
 
-fn disabled_environment_manager_for_tests() -> Arc<codex_exec_server::EnvironmentManager> {
-    let runtime_paths = codex_exec_server::ExecServerRuntimePaths::new(
-        std::env::current_exe().expect("current exe path"),
-        /*codex_linux_sandbox_exe*/ None,
-    )
-    .expect("runtime paths");
-    Arc::new(codex_exec_server::EnvironmentManager::new(
-        codex_exec_server::EnvironmentManagerArgs {
-            exec_server_url: Some("none".to_string()),
-            local_runtime_paths: runtime_paths,
-        },
-    ))
-}
-
 fn contextual_user_interrupted_marker() -> ResponseItem {
     interrupted_turn_history_marker(InterruptedTurnHistoryMarker::ContextualUser)
         .expect("contextual-user interrupted marker should be enabled")
@@ -307,11 +293,23 @@ async fn start_thread_accepts_explicit_environment_when_default_environment_is_d
     config.cwd = config.codex_home.abs();
     std::fs::create_dir_all(&config.codex_home).expect("create codex home");
 
+    let runtime_paths = codex_exec_server::ExecServerRuntimePaths::new(
+        std::env::current_exe().expect("current exe path"),
+        /*codex_linux_sandbox_exe*/ None,
+    )
+    .expect("runtime paths");
+    let environment_manager = Arc::new(
+        codex_exec_server::EnvironmentManager::create_for_tests(
+            Some("none".to_string()),
+            runtime_paths,
+        )
+        .await,
+    );
     let manager = ThreadManager::with_models_provider_and_home_for_tests(
         CodexAuth::from_api_key("dummy"),
         config.model_provider.clone(),
         config.codex_home.to_path_buf(),
-        disabled_environment_manager_for_tests(),
+        environment_manager,
     );
 
     let thread = manager