Enable supports_parallel_tool_calls for gpt-5 models

codex-rs/core/src/model_family.rs

@@ -177,6 +177,7 @@ pub fn find_family_for_model(slug: &str) -> Option<ModelFamily> {
             base_instructions: GPT_5_CODEX_INSTRUCTIONS.to_string(),
             apply_patch_tool_type: Some(ApplyPatchToolType::Freeform),
             support_verbosity: false,
+            supports_parallel_tool_calls: true,
         )
     } else if slug.starts_with("gpt-5.1") {
         model_family!(
@@ -187,6 +188,7 @@ pub fn find_family_for_model(slug: &str) -> Option<ModelFamily> {
             default_verbosity: Some(Verbosity::Low),
             base_instructions: GPT_5_1_INSTRUCTIONS.to_string(),
             default_reasoning_effort: Some(ReasoningEffort::Medium),
+            supports_parallel_tool_calls: true,
         )
     } else if slug.starts_with("gpt-5") {
         model_family!(