Enable it for gpt-5-codex and fix tests

codex-rs/core/src/model_family.rs

@@ -127,6 +127,7 @@ pub fn find_family_for_model(mut slug: &str) -> Option<ModelFamily> {
 
     // Internal models.
     } else if slug.starts_with("codex-") {
+        tracing::info!("Internal model selected. Used for experimental features");
         model_family!(
             slug, slug,
             supports_reasoning_summaries: true,
@@ -145,6 +146,8 @@ pub fn find_family_for_model(mut slug: &str) -> Option<ModelFamily> {
             reasoning_summary_format: ReasoningSummaryFormat::Experimental,
             base_instructions: GPT_5_CODEX_INSTRUCTIONS.to_string(),
             apply_patch_tool_type: Some(ApplyPatchToolType::Freeform),
+            experimental_supported_tools: vec!["read_file".to_string()],
+            supports_parallel_tool_calls: true,
         )
     } else if slug.starts_with("gpt-5") {
         model_family!(

codex-rs/core/src/tools/parallel.rs

@@ -76,7 +76,7 @@ impl ToolCallRuntime {
         &mut self,
         output: &mut [ProcessedResponseItem],
     ) -> Result<(), CodexErr> {
-        if self.pending_calls.len() > 0 {
+        if !self.pending_calls.is_empty() {
             tracing::info!(
                 "Resolving {} tool calls: {:?}",
                 self.pending_calls.len(),

codex-rs/core/src/tools/spec.rs

@@ -1039,6 +1039,7 @@ mod tests {
             &[
                 "unified_exec",
                 "apply_patch",
+                "read_file",
                 "web_search",
                 "view_image",
                 "dash/search",
@@ -1046,7 +1047,7 @@ mod tests {
         );
 
         assert_eq!(
-            tools[4].spec,
+            tools[5].spec,
             ToolSpec::Function(ResponsesApiTool {
                 name: "dash/search".to_string(),
                 parameters: JsonSchema::Object {
@@ -1106,13 +1107,14 @@ mod tests {
             &[
                 "unified_exec",
                 "apply_patch",
+                "read_file",
                 "web_search",
                 "view_image",
                 "dash/paginate",
             ],
         );
         assert_eq!(
-            tools[4].spec,
+            tools[5].spec,
             ToolSpec::Function(ResponsesApiTool {
                 name: "dash/paginate".to_string(),
                 parameters: JsonSchema::Object {
@@ -1170,13 +1172,14 @@ mod tests {
             &[
                 "unified_exec",
                 "apply_patch",
+                "read_file",
                 "web_search",
                 "view_image",
                 "dash/tags",
             ],
         );
         assert_eq!(
-            tools[4].spec,
+            tools[5].spec,
             ToolSpec::Function(ResponsesApiTool {
                 name: "dash/tags".to_string(),
                 parameters: JsonSchema::Object {
@@ -1237,13 +1240,14 @@ mod tests {
             &[
                 "unified_exec",
                 "apply_patch",
+                "read_file",
                 "web_search",
                 "view_image",
                 "dash/value",
             ],
         );
         assert_eq!(
-            tools[4].spec,
+            tools[5].spec,
             ToolSpec::Function(ResponsesApiTool {
                 name: "dash/value".to_string(),
                 parameters: JsonSchema::Object {
@@ -1341,6 +1345,7 @@ mod tests {
             &[
                 "unified_exec",
                 "apply_patch",
+                "read_file",
                 "web_search",
                 "view_image",
                 "test_server/do_something_cool",
@@ -1348,7 +1353,7 @@ mod tests {
         );
 
         assert_eq!(
-            tools[4].spec,
+            tools[5].spec,
             ToolSpec::Function(ResponsesApiTool {
                 name: "test_server/do_something_cool".to_string(),
                 parameters: JsonSchema::Object {

codex-rs/core/tests/suite/compact_resume_fork.rs

@@ -51,6 +51,8 @@ async fn compact_resume_and_fork_preserve_model_history_view() {
         return;
     }
 
+    let is_windows = cfg!(target_os = "windows");
+
     // 1. Arrange mocked SSE responses for the initial compact/resume/fork flow.
     let server = MockServer::start().await;
     mount_initial_flow(&server).await;
@@ -171,7 +173,7 @@ async fn compact_resume_and_fork_preserve_model_history_view() {
       ],
       "tools": tool_calls,
       "tool_choice": "auto",
-      "parallel_tool_calls": false,
+      "parallel_tool_calls": !is_windows,
       "reasoning": {
         "summary": "auto"
       },
@@ -240,7 +242,7 @@ async fn compact_resume_and_fork_preserve_model_history_view() {
       ],
       "tools": [],
       "tool_choice": "auto",
-      "parallel_tool_calls": false,
+      "parallel_tool_calls": !is_windows,
       "reasoning": {
         "summary": "auto"
       },
@@ -305,7 +307,7 @@ SUMMARY_ONLY_CONTEXT"
       ],
       "tools": tool_calls,
       "tool_choice": "auto",
-      "parallel_tool_calls": false,
+      "parallel_tool_calls": !is_windows,
       "reasoning": {
         "summary": "auto"
       },
@@ -390,7 +392,7 @@ SUMMARY_ONLY_CONTEXT"
       ],
       "tools": tool_calls,
       "tool_choice": "auto",
-      "parallel_tool_calls": false,
+      "parallel_tool_calls": !is_windows,
       "reasoning": {
         "summary": "auto"
       },
@@ -475,7 +477,7 @@ SUMMARY_ONLY_CONTEXT"
       ],
       "tools": tool_calls,
       "tool_choice": "auto",
-      "parallel_tool_calls": false,
+      "parallel_tool_calls": !is_windows,
       "reasoning": {
         "summary": "auto"
       },

codex-rs/core/tests/suite/model_tools.rs

@@ -125,7 +125,11 @@ async fn model_selects_expected_tools() {
     let gpt5_codex_tools = collect_tool_identifiers_for_model("gpt-5-codex").await;
     assert_eq!(
         gpt5_codex_tools,
-        vec!["shell".to_string(), "apply_patch".to_string(),],
+        vec![
+            "shell".to_string(),
+            "apply_patch".to_string(),
+            "read_file".to_string()
+        ],
         "gpt-5-codex should expose the apply_patch tool",
     );
 }

codex-rs/core/tests/suite/prompt_caching.rs

@@ -225,7 +225,13 @@ async fn prompt_tools_are_consistent_across_requests() {
         ("gpt-5", vec!["shell", "update_plan", "view_image"]),
         (
             "gpt-5-codex",
-            vec!["shell", "update_plan", "apply_patch", "view_image"],
+            vec![
+                "shell",
+                "update_plan",
+                "apply_patch",
+                "read_file",
+                "view_image",
+            ],
         ),
     ]);
     let expected_tools_names = tools_by_model