Add supports_parallel_tool_calls flag to included mcps

codex-rs/cli/src/mcp_cmd.rs

@@ -299,6 +299,7 @@ async fn run_add(config_overrides: &CliConfigOverrides, add_args: AddArgs) -> Re
         transport: transport.clone(),
         enabled: true,
         required: false,
+        supports_parallel_tool_calls: false,
         disabled_reason: None,
         startup_timeout_sec: None,
         tool_timeout_sec: None,

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

@@ -272,6 +272,7 @@ fn codex_apps_mcp_server_config(config: &McpConfig, auth: Option<&CodexAuth>) ->
         },
         enabled: true,
         required: false,
+        supports_parallel_tool_calls: false,
         disabled_reason: None,
         startup_timeout_sec: Some(Duration::from_secs(30)),
         tool_timeout_sec: None,

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

@@ -195,6 +195,7 @@ async fn effective_mcp_servers_preserve_user_servers_and_add_codex_apps() {
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,
@@ -216,6 +217,7 @@ async fn effective_mcp_servers_preserve_user_servers_and_add_codex_apps() {
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,

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

@@ -121,6 +121,7 @@ fn mcp_dependency_to_server_config(
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,
@@ -147,6 +148,7 @@ fn mcp_dependency_to_server_config(
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,

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

@@ -41,6 +41,7 @@ fn collect_missing_respects_canonical_installed_key() {
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,
@@ -91,6 +92,7 @@ fn collect_missing_dedupes_by_canonical_key_but_preserves_original_name() {
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,

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

@@ -757,6 +757,7 @@ fn mcp_init_error_display_prompts_for_github_pat() {
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,
@@ -806,6 +807,7 @@ fn mcp_init_error_display_reports_generic_errors() {
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,

codex-rs/config/src/mcp_edit.rs

@@ -177,6 +177,9 @@ fn serialize_mcp_server(config: &McpServerConfig) -> TomlItem {
     if config.required {
         entry["required"] = value(true);
     }
+    if config.supports_parallel_tool_calls {
+        entry["supports_parallel_tool_calls"] = value(true);
+    }
     if let Some(timeout) = config.startup_timeout_sec {
         entry["startup_timeout_sec"] = value(timeout.as_secs_f64());
     }

codex-rs/config/src/mcp_edit_tests.rs

@@ -24,6 +24,7 @@ async fn replace_mcp_servers_serializes_per_tool_approval_overrides() -> anyhow:
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: true,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,
@@ -59,6 +60,7 @@ async fn replace_mcp_servers_serializes_per_tool_approval_overrides() -> anyhow:
         serialized,
         r#"[mcp_servers.docs]
 command = "docs-server"
+supports_parallel_tool_calls = true
 
 [mcp_servers.docs.tools]
 

codex-rs/config/src/mcp_types.rs

@@ -69,6 +69,10 @@ pub struct McpServerConfig {
     #[serde(default, skip_serializing_if = "std::ops::Not::not")]
     pub required: bool,
 
+    /// When `true`, every tool from this server is advertised as safe for parallel tool calls.
+    #[serde(default, skip_serializing_if = "std::ops::Not::not")]
+    pub supports_parallel_tool_calls: bool,
+
     /// Reason this server was disabled after applying requirements.
     #[serde(skip)]
     pub disabled_reason: Option<McpServerDisabledReason>,
@@ -146,6 +150,8 @@ pub struct RawMcpServerConfig {
     #[serde(default)]
     pub required: Option<bool>,
     #[serde(default)]
+    pub supports_parallel_tool_calls: Option<bool>,
+    #[serde(default)]
     pub enabled_tools: Option<Vec<String>>,
     #[serde(default)]
     pub disabled_tools: Option<Vec<String>>,
@@ -180,6 +186,7 @@ impl TryFrom<RawMcpServerConfig> for McpServerConfig {
             tool_timeout_sec,
             enabled,
             required,
+            supports_parallel_tool_calls,
             enabled_tools,
             disabled_tools,
             scopes,
@@ -243,6 +250,7 @@ impl TryFrom<RawMcpServerConfig> for McpServerConfig {
             tool_timeout_sec,
             enabled: enabled.unwrap_or_else(default_enabled),
             required: required.unwrap_or_default(),
+            supports_parallel_tool_calls: supports_parallel_tool_calls.unwrap_or_default(),
             disabled_reason: None,
             enabled_tools,
             disabled_tools,

codex-rs/config/src/mcp_types_tests.rs

@@ -245,6 +245,38 @@ fn deserialize_server_config_with_tool_filters() {
     assert_eq!(cfg.disabled_tools, Some(vec!["blocked".to_string()]));
 }
 
+#[test]
+fn deserialize_server_config_with_parallel_tool_calls() {
+    let cfg: McpServerConfig = toml::from_str(
+        r#"
+            command = "echo"
+            supports_parallel_tool_calls = true
+        "#,
+    )
+    .expect("should deserialize supports_parallel_tool_calls");
+
+    assert!(cfg.supports_parallel_tool_calls);
+}
+
+#[test]
+fn serialize_round_trips_server_config_with_parallel_tool_calls() {
+    let cfg: McpServerConfig = toml::from_str(
+        r#"
+            command = "echo"
+            supports_parallel_tool_calls = true
+            tool_timeout_sec = 2.0
+        "#,
+    )
+    .expect("should deserialize supports_parallel_tool_calls");
+
+    let serialized = toml::to_string(&cfg).expect("should serialize MCP config");
+    assert!(serialized.contains("supports_parallel_tool_calls = true"));
+
+    let round_tripped: McpServerConfig =
+        toml::from_str(&serialized).expect("should deserialize serialized MCP config");
+    assert_eq!(round_tripped, cfg);
+}
+
 #[test]
 fn deserialize_ignores_unknown_server_fields() {
     let cfg: McpServerConfig = toml::from_str(
@@ -267,6 +299,7 @@ fn deserialize_ignores_unknown_server_fields() {
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,

codex-rs/core/config.schema.json

@@ -1522,6 +1522,10 @@
           "format": "double",
           "type": "number"
         },
+        "supports_parallel_tool_calls": {
+          "default": null,
+          "type": "boolean"
+        },
         "tool_timeout_sec": {
           "default": null,
           "format": "double",

codex-rs/core/src/codex.rs

@@ -7127,11 +7127,24 @@ pub(crate) async fn built_tools(
     );
     let direct_mcp_tools = has_mcp_servers.then_some(mcp_tool_exposure.direct_tools);
 
+    let parallel_mcp_server_names = turn_context
+        .config
+        .mcp_servers
+        .get()
+        .iter()
+        .filter_map(|(server_name, server_config)| {
+            server_config
+                .supports_parallel_tool_calls
+                .then_some(server_name.clone())
+        })
+        .collect::<HashSet<_>>();
+
     Ok(Arc::new(ToolRouter::from_config(
         &turn_context.tools_config,
         ToolRouterParams {
-            deferred_mcp_tools: mcp_tool_exposure.deferred_tools,
             mcp_tools: direct_mcp_tools,
+            deferred_mcp_tools: mcp_tool_exposure.deferred_tools,
+            parallel_mcp_server_names,
             discoverable_tools,
             dynamic_tools: turn_context.dynamic_tools.as_slice(),
         },

codex-rs/core/src/codex_tests.rs

@@ -312,6 +312,7 @@ fn test_tool_runtime(session: Arc<Session>, turn_context: Arc<TurnContext>) -> T
         crate::tools::router::ToolRouterParams {
             mcp_tools: None,
             deferred_mcp_tools: None,
+            parallel_mcp_server_names: HashSet::new(),
             discoverable_tools: None,
             dynamic_tools: turn_context.dynamic_tools.as_slice(),
         },
@@ -5353,6 +5354,7 @@ async fn fatal_tool_error_stops_turn_and_reports_error() {
         crate::tools::router::ToolRouterParams {
             deferred_mcp_tools,
             mcp_tools: Some(tools),
+            parallel_mcp_server_names: HashSet::new(),
             discoverable_tools: None,
             dynamic_tools: turn_context.dynamic_tools.as_slice(),
         },

codex-rs/core/src/config/config_tests.rs

@@ -83,6 +83,7 @@ fn stdio_mcp(command: &str) -> McpServerConfig {
         },
         enabled: true,
         required: false,
+        supports_parallel_tool_calls: false,
         disabled_reason: None,
         startup_timeout_sec: None,
         tool_timeout_sec: None,
@@ -104,6 +105,7 @@ fn http_mcp(url: &str) -> McpServerConfig {
         },
         enabled: true,
         required: false,
+        supports_parallel_tool_calls: false,
         disabled_reason: None,
         startup_timeout_sec: None,
         tool_timeout_sec: None,
@@ -2011,6 +2013,7 @@ async fn replace_mcp_servers_round_trips_entries() -> anyhow::Result<()> {
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: Some(Duration::from_secs(3)),
             tool_timeout_sec: Some(Duration::from_secs(5)),
@@ -2257,6 +2260,7 @@ async fn replace_mcp_servers_serializes_env_sorted() -> anyhow::Result<()> {
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,
@@ -2330,6 +2334,7 @@ async fn replace_mcp_servers_serializes_env_vars() -> anyhow::Result<()> {
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,
@@ -2383,6 +2388,7 @@ async fn replace_mcp_servers_serializes_cwd() -> anyhow::Result<()> {
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,
@@ -2434,6 +2440,7 @@ async fn replace_mcp_servers_streamable_http_serializes_bearer_token() -> anyhow
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: Some(Duration::from_secs(2)),
             tool_timeout_sec: None,
@@ -2501,6 +2508,7 @@ async fn replace_mcp_servers_streamable_http_serializes_custom_headers() -> anyh
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: Some(Duration::from_secs(2)),
             tool_timeout_sec: None,
@@ -2580,6 +2588,7 @@ async fn replace_mcp_servers_streamable_http_removes_optional_sections() -> anyh
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: Some(Duration::from_secs(2)),
             tool_timeout_sec: None,
@@ -2612,6 +2621,7 @@ async fn replace_mcp_servers_streamable_http_removes_optional_sections() -> anyh
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,
@@ -2679,6 +2689,7 @@ async fn replace_mcp_servers_streamable_http_isolates_headers_between_servers()
                 },
                 enabled: true,
                 required: false,
+                supports_parallel_tool_calls: false,
                 disabled_reason: None,
                 startup_timeout_sec: Some(Duration::from_secs(2)),
                 tool_timeout_sec: None,
@@ -2701,6 +2712,7 @@ async fn replace_mcp_servers_streamable_http_isolates_headers_between_servers()
                 },
                 enabled: true,
                 required: false,
+                supports_parallel_tool_calls: false,
                 disabled_reason: None,
                 startup_timeout_sec: None,
                 tool_timeout_sec: None,
@@ -2786,6 +2798,7 @@ async fn replace_mcp_servers_serializes_disabled_flag() -> anyhow::Result<()> {
             },
             enabled: false,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,
@@ -2833,6 +2846,7 @@ async fn replace_mcp_servers_serializes_required_flag() -> anyhow::Result<()> {
             },
             enabled: true,
             required: true,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,
@@ -2880,6 +2894,7 @@ async fn replace_mcp_servers_serializes_tool_filters() -> anyhow::Result<()> {
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,
@@ -2931,6 +2946,7 @@ async fn replace_mcp_servers_streamable_http_serializes_oauth_resource() -> anyh
             },
             enabled: true,
             required: false,
+            supports_parallel_tool_calls: false,
             disabled_reason: None,
             startup_timeout_sec: None,
             tool_timeout_sec: None,

codex-rs/core/src/config/edit.rs

@@ -225,6 +225,9 @@ mod document_helpers {
         if config.required {
             entry["required"] = value(true);
         }
+        if config.supports_parallel_tool_calls {
+            entry["supports_parallel_tool_calls"] = value(true);
+        }
         if let Some(timeout) = config.startup_timeout_sec {
             entry["startup_timeout_sec"] = value(timeout.as_secs_f64());
         }