Add MCP server experimental environment config

Introduce an experimental MCP server environment string and thread the optional value through config serialization, schema generation, and existing config fixtures.

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

Author: aibrahim-oai

codex-rs/cli/src/mcp_cmd.rs

@@ -297,6 +297,7 @@ async fn run_add(config_overrides: &CliConfigOverrides, add_args: AddArgs) -> Re
 
     let new_entry = McpServerConfig {
         transport: transport.clone(),
+        experimental_environment: None,
         enabled: true,
         required: false,
         supports_parallel_tool_calls: false,

codex-rs/codex-mcp/src/mcp/mod.rs

@@ -269,6 +269,7 @@ fn codex_apps_mcp_server_config(config: &McpConfig, auth: Option<&CodexAuth>) ->
             http_headers,
             env_http_headers: None,
         },
+        experimental_environment: None,
         enabled: true,
         required: false,
         supports_parallel_tool_calls: false,

codex-rs/codex-mcp/src/mcp/mod_tests.rs

@@ -193,6 +193,7 @@ async fn effective_mcp_servers_preserve_user_servers_and_add_codex_apps() {
                 http_headers: None,
                 env_http_headers: None,
             },
+            experimental_environment: None,
             enabled: true,
             required: false,
             supports_parallel_tool_calls: false,
@@ -215,6 +216,7 @@ async fn effective_mcp_servers_preserve_user_servers_and_add_codex_apps() {
                 http_headers: None,
                 env_http_headers: None,
             },
+            experimental_environment: None,
             enabled: true,
             required: false,
             supports_parallel_tool_calls: false,

codex-rs/codex-mcp/src/mcp/skill_dependencies.rs

@@ -119,6 +119,7 @@ fn mcp_dependency_to_server_config(
                 http_headers: None,
                 env_http_headers: None,
             },
+            experimental_environment: None,
             enabled: true,
             required: false,
             supports_parallel_tool_calls: false,
@@ -146,6 +147,7 @@ fn mcp_dependency_to_server_config(
                 env_vars: Vec::new(),
                 cwd: None,
             },
+            experimental_environment: None,
             enabled: true,
             required: false,
             supports_parallel_tool_calls: false,

codex-rs/codex-mcp/src/mcp/skill_dependencies_tests.rs

@@ -39,6 +39,7 @@ fn collect_missing_respects_canonical_installed_key() {
                 http_headers: None,
                 env_http_headers: None,
             },
+            experimental_environment: None,
             enabled: true,
             required: false,
             supports_parallel_tool_calls: false,
@@ -90,6 +91,7 @@ fn collect_missing_dedupes_by_canonical_key_but_preserves_original_name() {
                 http_headers: None,
                 env_http_headers: None,
             },
+            experimental_environment: None,
             enabled: true,
             required: false,
             supports_parallel_tool_calls: false,

codex-rs/codex-mcp/src/mcp_connection_manager_tests.rs

@@ -792,6 +792,7 @@ fn mcp_init_error_display_prompts_for_github_pat() {
                 http_headers: None,
                 env_http_headers: None,
             },
+            experimental_environment: None,
             enabled: true,
             required: false,
             supports_parallel_tool_calls: false,
@@ -842,6 +843,7 @@ fn mcp_init_error_display_reports_generic_errors() {
                 http_headers: None,
                 env_http_headers: None,
             },
+            experimental_environment: None,
             enabled: true,
             required: false,
             supports_parallel_tool_calls: false,

codex-rs/config/src/mcp_edit.rs

@@ -174,6 +174,9 @@ fn serialize_mcp_server(config: &McpServerConfig) -> TomlItem {
     if !config.enabled {
         entry["enabled"] = value(false);
     }
+    if let Some(environment) = &config.experimental_environment {
+        entry["experimental_environment"] = value(environment.clone());
+    }
     if config.required {
         entry["required"] = value(true);
     }

codex-rs/config/src/mcp_edit_tests.rs

@@ -22,6 +22,7 @@ async fn replace_mcp_servers_serializes_per_tool_approval_overrides() -> anyhow:
                 env_vars: Vec::new(),
                 cwd: None,
             },
+            experimental_environment: None,
             enabled: true,
             required: false,
             supports_parallel_tool_calls: true,

codex-rs/config/src/mcp_types.rs

@@ -61,6 +61,10 @@ pub struct McpServerConfig {
     #[serde(flatten)]
     pub transport: McpServerTransportConfig,
 
+    /// Experimental environment selector for where Codex should start this MCP server.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub experimental_environment: Option<String>,
+
     /// When `false`, Codex skips initializing this MCP server.
     #[serde(default = "default_enabled")]
     pub enabled: bool,
@@ -139,6 +143,8 @@ pub struct RawMcpServerConfig {
 
     // shared
     #[serde(default)]
+    pub experimental_environment: Option<String>,
+    #[serde(default)]
     pub startup_timeout_sec: Option<f64>,
     #[serde(default)]
     pub startup_timeout_ms: Option<u64>,
@@ -181,6 +187,7 @@ impl TryFrom<RawMcpServerConfig> for McpServerConfig {
             url,
             bearer_token,
             bearer_token_env_var,
+            experimental_environment,
             startup_timeout_sec,
             startup_timeout_ms,
             tool_timeout_sec,
@@ -246,6 +253,7 @@ impl TryFrom<RawMcpServerConfig> for McpServerConfig {
 
         Ok(Self {
             transport,
+            experimental_environment,
             startup_timeout_sec,
             tool_timeout_sec,
             enabled: enabled.unwrap_or_else(default_enabled),

codex-rs/config/src/mcp_types_tests.rs

@@ -297,6 +297,7 @@ fn deserialize_ignores_unknown_server_fields() {
                 env_vars: Vec::new(),
                 cwd: None,
             },
+            experimental_environment: None,
             enabled: true,
             required: false,
             supports_parallel_tool_calls: false,