Add code_mode experimental feature (#13418)

A much narrower and more isolated (no node features) version of js_repl

codex-rs/core/src/tools/handlers/code_mode.rs

@@ -0,0 +1,55 @@
+use async_trait::async_trait;
+
+use crate::features::Feature;
+use crate::function_tool::FunctionCallError;
+use crate::tools::code_mode;
+use crate::tools::context::ContentToolOutput;
+use crate::tools::context::ToolInvocation;
+use crate::tools::context::ToolOutputBox;
+use crate::tools::context::ToolPayload;
+use crate::tools::registry::ToolHandler;
+use crate::tools::registry::ToolKind;
+
+pub struct CodeModeHandler;
+
+#[async_trait]
+impl ToolHandler for CodeModeHandler {
+    fn kind(&self) -> ToolKind {
+        ToolKind::Function
+    }
+
+    fn matches_kind(&self, payload: &ToolPayload) -> bool {
+        matches!(payload, ToolPayload::Custom { .. })
+    }
+
+    async fn handle(&self, invocation: ToolInvocation) -> Result<ToolOutputBox, FunctionCallError> {
+        let ToolInvocation {
+            session,
+            turn,
+            tracker,
+            payload,
+            ..
+        } = invocation;
+
+        if !session.features().enabled(Feature::CodeMode) {
+            return Err(FunctionCallError::RespondToModel(
+                "code_mode is disabled by feature flag".to_string(),
+            ));
+        }
+
+        let code = match payload {
+            ToolPayload::Custom { input } => input,
+            _ => {
+                return Err(FunctionCallError::RespondToModel(
+                    "code_mode expects raw JavaScript source text".to_string(),
+                ));
+            }
+        };
+
+        let content_items = code_mode::execute(session, turn, tracker, code).await?;
+        Ok(Box::new(ContentToolOutput {
+            content: content_items,
+            success: Some(true),
+        }))
+    }
+}

codex-rs/core/src/tools/handlers/mod.rs

@@ -1,6 +1,7 @@
 pub(crate) mod agent_jobs;
 pub mod apply_patch;
 mod artifacts;
+mod code_mode;
 mod dynamic;
 mod grep_files;
 mod js_repl;
@@ -32,6 +33,7 @@ use crate::sandboxing::merge_permission_profiles;
 use crate::sandboxing::normalize_additional_permissions;
 pub use apply_patch::ApplyPatchHandler;
 pub use artifacts::ArtifactsHandler;
+pub use code_mode::CodeModeHandler;
 use codex_protocol::models::PermissionProfile;
 use codex_protocol::protocol::AskForApproval;
 pub use dynamic::DynamicToolHandler;