diff --git a/codex-rs/core/src/session/turn.rs b/codex-rs/core/src/session/turn.rs
index 9d4e7d1e82..13e61c3b89 100644
--- a/codex-rs/core/src/session/turn.rs
+++ b/codex-rs/core/src/session/turn.rs
@@ -87,6 +87,7 @@ use codex_protocol::models::ContentItem;
 use codex_protocol::models::MessagePhase;
 use codex_protocol::models::ResponseInputItem;
 use codex_protocol::models::ResponseItem;
+use codex_protocol::openai_models::ToolMode;
 use codex_protocol::protocol::AgentMessageContentDeltaEvent;
 use codex_protocol::protocol::AgentReasoningSectionBreakEvent;
 use codex_protocol::protocol::CodexErrorInfo;
@@ -948,10 +949,15 @@ pub(crate) fn build_prompt(
     turn_context: &TurnContext,
     base_instructions: BaseInstructions,
 ) -> Prompt {
+    let tool_mode_supports_parallel_calls = match turn_context.tool_mode {
+        ToolMode::Direct => true,
+        ToolMode::CodeMode | ToolMode::CodeModeOnly => false,
+    };
     Prompt {
         input,
         tools: router.model_visible_specs(),
-        parallel_tool_calls: turn_context.model_info.supports_parallel_tool_calls,
+        parallel_tool_calls: turn_context.model_info.supports_parallel_tool_calls
+            && tool_mode_supports_parallel_calls,
         base_instructions,
         personality: turn_context.personality,
         output_schema: turn_context.final_output_json_schema.clone(),
diff --git a/codex-rs/core/tests/suite/model_runtime_selectors.rs b/codex-rs/core/tests/suite/model_runtime_selectors.rs
index 15ed519af7..843371cbe4 100644
--- a/codex-rs/core/tests/suite/model_runtime_selectors.rs
+++ b/codex-rs/core/tests/suite/model_runtime_selectors.rs
@@ -147,6 +147,7 @@ async fn remote_tool_mode_selector_overrides_feature_flags() -> Result<()> {
     skip_if_no_network!(Ok(()));
 
     let mut direct_model = remote_model("test-tool-mode-direct");
+    direct_model.supports_parallel_tool_calls = true;
     direct_model.tool_mode = Some(ToolMode::Direct);
     let direct_body = response_body_for_remote_model(direct_model, |config| {
         config
@@ -163,8 +164,10 @@ async fn remote_tool_mode_selector_overrides_feature_flags() -> Result<()> {
                 && name != codex_code_mode::WAIT_TOOL_NAME),
         "direct mode should override enabled code mode flags: {direct_tools:?}"
     );
+    assert_eq!(direct_body["parallel_tool_calls"], true);
 
     let mut code_mode_only_model = remote_model("test-tool-mode-code-mode-only");
+    code_mode_only_model.supports_parallel_tool_calls = true;
     code_mode_only_model.tool_mode = Some(ToolMode::CodeModeOnly);
     code_mode_only_model.input_modalities = vec![InputModality::Text, InputModality::Image];
     let code_mode_only_body = response_body_for_remote_model(code_mode_only_model, |_| {}).await?;
@@ -179,6 +182,18 @@ async fn remote_tool_mode_selector_overrides_feature_flags() -> Result<()> {
             "image_generation".to_string(),
         ]
     );
+    assert_eq!(code_mode_only_body["parallel_tool_calls"], false);
+
+    let mut local_code_mode_model = remote_model("test-tool-mode-local-code-mode");
+    local_code_mode_model.supports_parallel_tool_calls = true;
+    let local_code_mode_body = response_body_for_remote_model(local_code_mode_model, |config| {
+        config
+            .features
+            .enable(Feature::CodeMode)
+            .expect("test config should allow feature update");
+    })
+    .await?;
+    assert_eq!(local_code_mode_body["parallel_tool_calls"], false);
 
     Ok(())
 }