openai · fjord-oai · Feb 11, 2026 · Feb 2, 2026
diff --git a/.codespellrc b/.codespellrc
@@ -1,6 +1,6 @@
 [codespell]
 # Ref: https://github.com/codespell-project/codespell#using-a-config-file
-skip = .git*,vendor,*-lock.yaml,*.lock,.codespellrc,*test.ts,*.jsonl,frame*.txt,*.snap,*.snap.new
+skip = .git*,vendor,*-lock.yaml,*.lock,.codespellrc,*test.ts,*.jsonl,frame*.txt,*.snap,*.snap.new,*meriyah.umd.min.js
 check-hidden = true
 ignore-regex = ^\s*"image/\S+": ".*|\b(afterAll)\b
 ignore-words-list = ratatui,ser,iTerm,iterm2,iterm
diff --git a/NOTICE b/NOTICE
@@ -4,3 +4,6 @@ Copyright 2025 OpenAI
 This project includes code derived from [Ratatui](https://github.com/ratatui/ratatui), licensed under the MIT license.
 Copyright (c) 2016-2022 Florian Dehau
 Copyright (c) 2023-2025 The Ratatui Developers
+
+This project includes Meriyah parser assets from [meriyah](https://github.com/meriyah/meriyah), licensed under the ISC license.
+Copyright (c) 2019 and later, KFlash and others.
diff --git a/codex-rs/BUILD.bazel b/codex-rs/BUILD.bazel
@@ -1 +1,3 @@
-
+exports_files([
+    "node-version.txt",
+])
diff --git a/codex-rs/core/BUILD.bazel b/codex-rs/core/BUILD.bazel
@@ -11,7 +11,9 @@ codex_rust_crate(
             "Cargo.toml",
         ],
         allow_empty = True,
-    ),
+    ) + [
+        "//codex-rs:node-version.txt",
+    ],
     integration_compile_data_extra = [
         "//codex-rs/apply-patch:apply_patch_tool_instructions.md",
         "models.json",

diff --git a/codex-rs/core/config.schema.json b/codex-rs/core/config.schema.json
@@ -221,6 +221,9 @@
             "include_apply_patch_tool": {
               "type": "boolean"
             },
+            "js_repl": {
+              "type": "boolean"
+            },
             "memory_tool": {
               "type": "boolean"
             },
@@ -290,6 +293,9 @@
         "include_apply_patch_tool": {
           "type": "boolean"
         },
+        "js_repl_node_path": {
+          "$ref": "#/definitions/AbsolutePathBuf"
+        },
         "model": {
           "type": "string"
         },
@@ -1275,6 +1281,9 @@
         "include_apply_patch_tool": {
           "type": "boolean"
         },
+        "js_repl": {
+          "type": "boolean"
+        },
         "memory_tool": {
           "type": "boolean"
         },
@@ -1397,6 +1406,14 @@
       "description": "System instructions.",
       "type": "string"
     },
+    "js_repl_node_path": {
+      "allOf": [
+        {
+          "$ref": "#/definitions/AbsolutePathBuf"
+        }
+      ],
+      "description": "Optional absolute path to the Node runtime used by `js_repl`."
+    },
     "log_dir": {
       "allOf": [
         {

diff --git a/codex-rs/core/src/codex.rs b/codex-rs/core/src/codex.rs
@@ -220,6 +220,7 @@ use crate::tasks::SessionTask;
 use crate::tasks::SessionTaskContext;
 use crate::tools::ToolRouter;
 use crate::tools::context::SharedTurnDiffTracker;
+use crate::tools::js_repl::JsReplHandle;
 use crate::tools::parallel::ToolCallRuntime;
 use crate::tools::sandboxing::ApprovalStore;
 use crate::tools::spec::ToolsConfig;
@@ -510,6 +511,7 @@ pub(crate) struct Session {
     pending_mcp_server_refresh_config: Mutex<Option<McpServerRefreshConfig>>,
     pub(crate) active_turn: Mutex<Option<ActiveTurn>>,
     pub(crate) services: SessionServices,
+    js_repl: Arc<JsReplHandle>,
     next_internal_sub_id: AtomicU64,
 }
 
@@ -549,6 +551,7 @@ pub(crate) struct TurnContext {
     pub(crate) codex_linux_sandbox_exe: Option<PathBuf>,
     pub(crate) tool_call_gate: Arc<ReadinessFlag>,
     pub(crate) truncation_policy: TruncationPolicy,
+    pub(crate) js_repl: Arc<JsReplHandle>,
     pub(crate) dynamic_tools: Vec<DynamicToolSpec>,
     turn_metadata_header: OnceCell<Option<String>>,
 }
@@ -809,6 +812,7 @@ impl Session {
         model_info: ModelInfo,
         network: Option<NetworkProxy>,
         sub_id: String,
+        js_repl: Arc<JsReplHandle>,
     ) -> TurnContext {
         let reasoning_effort = session_configuration.collaboration_mode.reasoning_effort();
         let reasoning_summary = session_configuration.model_reasoning_summary;
@@ -857,6 +861,7 @@ impl Session {
             codex_linux_sandbox_exe: per_turn_config.codex_linux_sandbox_exe.clone(),
             tool_call_gate: Arc::new(ReadinessFlag::new()),
             truncation_policy: model_info.truncation_policy.into(),
+            js_repl,
             dynamic_tools: session_configuration.dynamic_tools.clone(),
             turn_metadata_header: OnceCell::new(),
         }
@@ -1123,6 +1128,10 @@ impl Session {
                 Self::build_model_client_beta_features_header(config.as_ref()),
             ),
         };
+        let js_repl = Arc::new(JsReplHandle::with_node_path(
+            config.js_repl_node_path.clone(),
+            config.codex_home.clone(),
+        ));
 
         let prewarm_model_info = models_manager
             .get_model_info(session_configuration.collaboration_mode.model(), &config)
@@ -1150,6 +1159,7 @@ impl Session {
             pending_mcp_server_refresh_config: Mutex::new(None),
             active_turn: Mutex::new(None),
             services,
+            js_repl,
             next_internal_sub_id: AtomicU64::new(0),
         });
 
@@ -1598,6 +1608,7 @@ impl Session {
                 .as_ref()
                 .map(StartedNetworkProxy::proxy),
             sub_id,
+            Arc::clone(&self.js_repl),
         );
 
         if let Some(final_schema) = final_output_json_schema {
@@ -3766,6 +3777,7 @@ async fn spawn_review_thread(
         final_output_json_schema: None,
         codex_linux_sandbox_exe: parent_turn_context.codex_linux_sandbox_exe.clone(),
         tool_call_gate: Arc::new(ReadinessFlag::new()),
+        js_repl: Arc::clone(&sess.js_repl),
         dynamic_tools: parent_turn_context.dynamic_tools.clone(),
         truncation_policy: model_info.truncation_policy.into(),
         turn_metadata_header: parent_turn_context.turn_metadata_header.clone(),
@@ -4253,11 +4265,13 @@ async fn run_sampling_request(
 
     let model_supports_parallel = turn_context.model_info.supports_parallel_tool_calls;
 
+    let tools =
+        crate::tools::spec::filter_tools_for_model(router.specs(), &turn_context.tools_config);
     let base_instructions = sess.get_base_instructions().await;
 
     let prompt = Prompt {
         input,
-        tools: router.specs(),
+        tools,
         parallel_tool_calls: model_supports_parallel,
         base_instructions,
         personality: turn_context.personality,
@@ -5280,9 +5294,9 @@ mod tests {
         ];
 
         let (session, _turn_context) = make_session_and_context().await;
+        let config = test_config();
 
         for test_case in test_cases {
-            let config = test_config();
             let model_info = model_info_for_slug(test_case.slug, &config);
             if test_case.expects_apply_patch_instructions {
                 assert_eq!(
@@ -6298,6 +6312,10 @@ mod tests {
                 Session::build_model_client_beta_features_header(config.as_ref()),
             ),
         };
+        let js_repl = Arc::new(JsReplHandle::with_node_path(
+            config.js_repl_node_path.clone(),
+            config.codex_home.clone(),
+        ));
 
         let turn_context = Session::make_turn_context(
             Some(Arc::clone(&auth_manager)),
@@ -6308,6 +6326,7 @@ mod tests {
             model_info,
             None,
             "turn_id".to_string(),
+            Arc::clone(&js_repl),
         );
 
         let session = Session {
@@ -6319,6 +6338,7 @@ mod tests {
             pending_mcp_server_refresh_config: Mutex::new(None),
             active_turn: Mutex::new(None),
             services,
+            js_repl,
             next_internal_sub_id: AtomicU64::new(0),
         };
 
@@ -6435,6 +6455,10 @@ mod tests {
                 Session::build_model_client_beta_features_header(config.as_ref()),
             ),
         };
+        let js_repl = Arc::new(JsReplHandle::with_node_path(
+            config.js_repl_node_path.clone(),
+            config.codex_home.clone(),
+        ));
 
         let turn_context = Arc::new(Session::make_turn_context(
             Some(Arc::clone(&auth_manager)),
@@ -6445,6 +6469,7 @@ mod tests {
             model_info,
             None,
             "turn_id".to_string(),
+            Arc::clone(&js_repl),
         ));
 
         let session = Arc::new(Session {
@@ -6456,6 +6481,7 @@ mod tests {
             pending_mcp_server_refresh_config: Mutex::new(None),
             active_turn: Mutex::new(None),
             services,
+            js_repl,
             next_internal_sub_id: AtomicU64::new(0),
         });
 

diff --git a/codex-rs/core/src/config/mod.rs b/codex-rs/core/src/config/mod.rs
@@ -305,6 +305,9 @@ pub struct Config {
     /// When this program is invoked, arg0 will be set to `codex-linux-sandbox`.
     pub codex_linux_sandbox_exe: Option<PathBuf>,
 
+    /// Optional absolute path to the Node runtime used by `js_repl`.
+    pub js_repl_node_path: Option<PathBuf>,
+
     /// Value to use for `reasoning.effort` when making a request using the
     /// Responses API.
     pub model_reasoning_effort: Option<ReasoningEffort>,
@@ -936,6 +939,9 @@ pub struct ConfigToml {
     /// Token budget applied when storing tool/function outputs in the context manager.
     pub tool_output_token_limit: Option<usize>,
 
+    /// Optional absolute path to the Node runtime used by `js_repl`.
+    pub js_repl_node_path: Option<AbsolutePathBuf>,
+
     /// Profile to use from the `profiles` map.
     pub profile: Option<String>,
 
@@ -1277,6 +1283,7 @@ pub struct ConfigOverrides {
     pub model_provider: Option<String>,
     pub config_profile: Option<String>,
     pub codex_linux_sandbox_exe: Option<PathBuf>,
+    pub js_repl_node_path: Option<PathBuf>,
     pub base_instructions: Option<String>,
     pub developer_instructions: Option<String>,
     pub personality: Option<Personality>,
@@ -1403,6 +1410,7 @@ impl Config {
             model_provider,
             config_profile: config_profile_key,
             codex_linux_sandbox_exe,
+            js_repl_node_path: js_repl_node_path_override,
             base_instructions,
             developer_instructions,
             personality,
@@ -1634,6 +1642,9 @@ impl Config {
             "experimental compact prompt file",
         )?;
         let compact_prompt = compact_prompt.or(file_compact_prompt);
+        let js_repl_node_path = js_repl_node_path_override
+            .or(config_profile.js_repl_node_path.map(Into::into))
+            .or(cfg.js_repl_node_path.map(Into::into));
 
         let review_model = override_review_model.or(cfg.review_model);
 
@@ -1751,6 +1762,7 @@ impl Config {
             ephemeral: ephemeral.unwrap_or_default(),
             file_opener: cfg.file_opener.unwrap_or(UriBasedFileOpener::VsCode),
             codex_linux_sandbox_exe,
+            js_repl_node_path,
 
             hide_agent_reasoning: cfg.hide_agent_reasoning.unwrap_or(false),
             show_raw_agent_reasoning: cfg
@@ -4048,6 +4060,7 @@ model_verbosity = "high"
                 ephemeral: false,
                 file_opener: UriBasedFileOpener::VsCode,
                 codex_linux_sandbox_exe: None,
+                js_repl_node_path: None,
                 hide_agent_reasoning: false,
                 show_raw_agent_reasoning: false,
                 model_reasoning_effort: Some(ReasoningEffort::High),
@@ -4154,6 +4167,7 @@ model_verbosity = "high"
             ephemeral: false,
             file_opener: UriBasedFileOpener::VsCode,
             codex_linux_sandbox_exe: None,
+            js_repl_node_path: None,
             hide_agent_reasoning: false,
             show_raw_agent_reasoning: false,
             model_reasoning_effort: None,
@@ -4258,6 +4272,7 @@ model_verbosity = "high"
             ephemeral: false,
             file_opener: UriBasedFileOpener::VsCode,
             codex_linux_sandbox_exe: None,
+            js_repl_node_path: None,
             hide_agent_reasoning: false,
             show_raw_agent_reasoning: false,
             model_reasoning_effort: None,
@@ -4348,6 +4363,7 @@ model_verbosity = "high"
             ephemeral: false,
             file_opener: UriBasedFileOpener::VsCode,
             codex_linux_sandbox_exe: None,
+            js_repl_node_path: None,
             hide_agent_reasoning: false,
             show_raw_agent_reasoning: false,
             model_reasoning_effort: Some(ReasoningEffort::High),

diff --git a/codex-rs/core/src/config/profile.rs b/codex-rs/core/src/config/profile.rs
@@ -29,6 +29,7 @@ pub struct ConfigProfile {
     pub chatgpt_base_url: Option<String>,
     /// Optional path to a file containing model instructions.
     pub model_instructions_file: Option<AbsolutePathBuf>,
+    pub js_repl_node_path: Option<AbsolutePathBuf>,
     /// Deprecated: ignored. Use `model_instructions_file`.
     #[schemars(skip)]
     pub experimental_instructions_file: Option<AbsolutePathBuf>,

diff --git a/codex-rs/core/src/features.rs b/codex-rs/core/src/features.rs
@@ -78,6 +78,8 @@ pub enum Feature {
     ShellTool,
 
     // Experimental
+    /// Enable JavaScript REPL tools backed by a persistent Node kernel.
+    JsRepl,
     /// Use the single unified PTY-backed exec tool.
     UnifiedExec,
     /// Include the freeform apply_patch tool.
@@ -422,6 +424,12 @@ pub const FEATURES: &[FeatureSpec] = &[
         stage: Stage::Stable,
         default_enabled: true,
     },
+    FeatureSpec {
+        id: Feature::JsRepl,
+        key: "js_repl",
+        stage: Stage::UnderDevelopment,
+        default_enabled: false,
+    },
     FeatureSpec {
         id: Feature::WebSearchRequest,
         key: "web_search_request",