code-mode standalone: extract protocol and add host crate (#27724)

This is phase 1 of a 4 phase stack:
1. **Add protocol and host crates for new IPC code mode implementation**
2. Create the new standalone binary
3. Create a new IPC `CodeModeSessionProvider` to use new binary
4. Remove v8 from core and only use IPC provider


## Add protocol and host crates for new IPC code mode implementation
Establish a clean process boundary without changing the existing
in-process behavior.

- Add the codex-code-mode-protocol crate for shared session, runtime,
response, and tool-definition types.
- Move protocol-facing code out of the V8-backed implementation.
- Add a buildable codex-code-mode-host crate as the foundation for the
standalone process.
- Keep the existing in-process runtime as the active implementation.

codex-rs/code-mode/src/lib.rs

@@ -1,46 +1,7 @@
-mod description;
-mod response;
 mod runtime;
 mod service;
 
-pub use description::CODE_MODE_PRAGMA_PREFIX;
-pub use description::CodeModeToolKind;
-pub use description::ToolDefinition;
-pub use description::ToolNamespaceDescription;
-pub use description::augment_tool_definition;
-pub use description::build_exec_tool_description;
-pub use description::build_wait_tool_description;
-pub use description::is_code_mode_nested_tool;
-pub use description::normalize_code_mode_identifier;
-pub use description::parse_exec_source;
-pub use description::render_code_mode_sample;
-pub use description::render_json_schema_to_typescript;
-pub use response::DEFAULT_IMAGE_DETAIL;
-pub use response::FunctionCallOutputContentItem;
-pub use response::ImageDetail;
-pub use runtime::CodeModeNestedToolCall;
-pub use runtime::DEFAULT_EXEC_YIELD_TIME_MS;
-pub use runtime::DEFAULT_MAX_OUTPUT_TOKENS_PER_EXEC_CALL;
-pub use runtime::DEFAULT_WAIT_YIELD_TIME_MS;
-pub use runtime::ExecuteRequest;
-pub use runtime::ExecuteToPendingOutcome;
-pub use runtime::RuntimeResponse;
-pub use runtime::WaitOutcome;
-pub use runtime::WaitRequest;
-pub use runtime::WaitToPendingOutcome;
-pub use runtime::WaitToPendingRequest;
-pub use service::CellId;
+pub use codex_code_mode_protocol::*;
 pub use service::CodeModeService;
-pub use service::CodeModeSession;
-pub use service::CodeModeSessionDelegate;
-pub use service::CodeModeSessionProvider;
-pub use service::CodeModeSessionProviderFuture;
-pub use service::CodeModeSessionResultFuture;
 pub use service::InProcessCodeModeSessionProvider;
 pub use service::NoopCodeModeSessionDelegate;
-pub use service::NotificationFuture;
-pub use service::StartedCell;
-pub use service::ToolInvocationFuture;
-
-pub const PUBLIC_TOOL_NAME: &str = "exec";
-pub const WAIT_TOOL_NAME: &str = "wait";

codex-rs/code-mode/src/response.rs

@@ -1,26 +0,0 @@
-use serde::Deserialize;
-use serde::Serialize;
-
-#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq)]
-#[serde(rename_all = "lowercase")]
-pub enum ImageDetail {
-    Auto,
-    Low,
-    High,
-    Original,
-}
-
-pub const DEFAULT_IMAGE_DETAIL: ImageDetail = ImageDetail::High;
-
-#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
-#[serde(tag = "type", rename_all = "snake_case")]
-pub enum FunctionCallOutputContentItem {
-    InputText {
-        text: String,
-    },
-    InputImage {
-        image_url: String,
-        #[serde(default, skip_serializing_if = "Option::is_none")]
-        detail: Option<ImageDetail>,
-    },
-}

codex-rs/code-mode/src/runtime/callbacks.rs

@@ -1,4 +1,4 @@
-use crate::response::FunctionCallOutputContentItem;
+use codex_code_mode_protocol::FunctionCallOutputContentItem;
 
 use super::EXIT_SENTINEL;
 use super::RuntimeEvent;

codex-rs/code-mode/src/runtime/mod.rs

@@ -9,125 +9,17 @@ use std::sync::OnceLock;
 use std::sync::mpsc as std_mpsc;
 use std::thread;
 
+use codex_code_mode_protocol::CodeModeToolKind;
+use codex_code_mode_protocol::EnabledToolMetadata;
+use codex_code_mode_protocol::ExecuteRequest;
+use codex_code_mode_protocol::FunctionCallOutputContentItem;
+use codex_code_mode_protocol::enabled_tool_metadata;
 use codex_protocol::ToolName;
-use serde::Serialize;
 use serde_json::Value as JsonValue;
 use tokio::sync::mpsc;
 
-use crate::description::CodeModeToolKind;
-use crate::description::EnabledToolMetadata;
-use crate::description::ToolDefinition;
-use crate::description::enabled_tool_metadata;
-use crate::response::FunctionCallOutputContentItem;
-use crate::service::CellId;
-
-pub const DEFAULT_EXEC_YIELD_TIME_MS: u64 = 10_000;
-pub const DEFAULT_WAIT_YIELD_TIME_MS: u64 = 10_000;
-pub const DEFAULT_MAX_OUTPUT_TOKENS_PER_EXEC_CALL: usize = 10_000;
 const EXIT_SENTINEL: &str = "__codex_code_mode_exit__";
 
-#[derive(Clone, Debug)]
-pub struct ExecuteRequest {
-    pub tool_call_id: String,
-    pub enabled_tools: Vec<ToolDefinition>,
-    pub source: String,
-    pub yield_time_ms: Option<u64>,
-    pub max_output_tokens: Option<usize>,
-}
-
-#[derive(Clone, Debug)]
-pub struct WaitRequest {
-    pub cell_id: CellId,
-    pub yield_time_ms: u64,
-}
-
-#[derive(Clone, Debug)]
-pub struct WaitToPendingRequest {
-    pub cell_id: CellId,
-}
-
-/// Result of waiting on a code-mode cell.
-///
-/// The wrapped `RuntimeResponse` is the model-facing wait result. The enum
-/// variant carries the extra lifecycle provenance that `RuntimeResponse` cannot:
-/// a failed real cell and a missing-cell wait both use
-/// `RuntimeResponse::Result { error_text: Some(..), .. }`, but only the former
-/// should be treated as a code-cell lifecycle event.
-#[derive(Debug, PartialEq)]
-pub enum WaitOutcome {
-    /// The requested code cell was live when the wait command was accepted.
-    LiveCell(RuntimeResponse),
-    /// The requested code cell was not live.
-    MissingCell(RuntimeResponse),
-}
-
-/// Result of executing a code-mode cell until it either completes or reaches a
-/// quiescent pending state.
-#[derive(Debug, PartialEq)]
-pub enum ExecuteToPendingOutcome {
-    /// The cell is waiting for more runtime input after draining the runtime
-    /// input queue that was ready at the pending boundary.
-    Pending {
-        cell_id: CellId,
-        content_items: Vec<FunctionCallOutputContentItem>,
-        /// Runtime tool-call ids emitted before this paused execution frontier
-        /// sealed. Hosts can use these ids to drain their tool-call transport
-        /// before surfacing the pending boundary to callers.
-        pending_tool_call_ids: Vec<String>,
-    },
-    /// The cell reached a terminal runtime response before going pending.
-    Completed(RuntimeResponse),
-}
-
-/// Result of resuming a live code-mode cell until it completes or becomes
-/// quiescent again.
-#[derive(Debug, PartialEq)]
-pub enum WaitToPendingOutcome {
-    /// The requested code cell was live when the wait command was accepted.
-    LiveCell(ExecuteToPendingOutcome),
-    /// The requested code cell was not live.
-    MissingCell(RuntimeResponse),
-}
-
-impl From<WaitOutcome> for RuntimeResponse {
-    fn from(outcome: WaitOutcome) -> Self {
-        match outcome {
-            WaitOutcome::LiveCell(response) | WaitOutcome::MissingCell(response) => response,
-        }
-    }
-}
-
-#[derive(Debug, PartialEq, Serialize)]
-pub enum RuntimeResponse {
-    Yielded {
-        cell_id: CellId,
-        content_items: Vec<FunctionCallOutputContentItem>,
-    },
-    Terminated {
-        cell_id: CellId,
-        content_items: Vec<FunctionCallOutputContentItem>,
-    },
-    Result {
-        cell_id: CellId,
-        content_items: Vec<FunctionCallOutputContentItem>,
-        error_text: Option<String>,
-    },
-}
-
-/// Nested tool request emitted by one code-mode cell.
-///
-/// Code mode owns the per-cell runtime id. Hosts should preserve it for
-/// provenance/debugging, but should still assign their own runtime tool call id
-/// if their tool-call graph requires globally unique ids.
-#[derive(Debug)]
-pub struct CodeModeNestedToolCall {
-    pub cell_id: CellId,
-    pub runtime_tool_call_id: String,
-    pub tool_name: ToolName,
-    pub tool_kind: CodeModeToolKind,
-    pub input: Option<JsonValue>,
-}
-
 #[derive(Debug)]
 pub(crate) enum RuntimeCommand {
     ToolResponse { id: String, result: JsonValue },
@@ -326,12 +218,9 @@ fn run_runtime(
     }
 
     let mut pending_promise = pending_promise;
-    loop {
-        let Some(command) = next_runtime_command(&event_tx, &command_rx, &control_rx, pending_mode)
-        else {
-            break;
-        };
-
+    while let Some(command) =
+        next_runtime_command(&event_tx, &command_rx, &control_rx, pending_mode)
+    {
         match command {
             RuntimeCommand::Terminate => break,
             RuntimeCommand::ToolResponse { id, result } => {

codex-rs/code-mode/src/runtime/value.rs

@@ -1,8 +1,8 @@
 use serde_json::Value as JsonValue;
 
-use crate::response::DEFAULT_IMAGE_DETAIL;
-use crate::response::FunctionCallOutputContentItem;
-use crate::response::ImageDetail;
+use codex_code_mode_protocol::DEFAULT_IMAGE_DETAIL;
+use codex_code_mode_protocol::FunctionCallOutputContentItem;
+use codex_code_mode_protocol::ImageDetail;
 
 const IMAGE_HELPER_EXPECTS_MESSAGE: &str = "image expects a non-empty image URL string, an object with image_url and optional detail, or a raw MCP image block";
 const CODEX_IMAGE_DETAIL_META_KEY: &str = "codex/imageDetail";

codex-rs/code-mode/src/service.rs

@@ -1,15 +1,29 @@
 use std::collections::HashMap;
-use std::fmt;
-use std::future::Future;
-use std::pin::Pin;
 use std::sync::Arc;
 use std::sync::atomic::AtomicBool;
 use std::sync::atomic::AtomicU64;
 use std::sync::atomic::Ordering;
 use std::time::Duration;
 
-use serde::Deserialize;
-use serde::Serialize;
+use codex_code_mode_protocol::CellId;
+use codex_code_mode_protocol::CodeModeNestedToolCall;
+use codex_code_mode_protocol::CodeModeSession;
+use codex_code_mode_protocol::CodeModeSessionDelegate;
+use codex_code_mode_protocol::CodeModeSessionProvider;
+use codex_code_mode_protocol::CodeModeSessionProviderFuture;
+use codex_code_mode_protocol::CodeModeSessionResultFuture;
+use codex_code_mode_protocol::DEFAULT_EXEC_YIELD_TIME_MS;
+use codex_code_mode_protocol::ExecuteRequest;
+use codex_code_mode_protocol::ExecuteToPendingOutcome;
+use codex_code_mode_protocol::FunctionCallOutputContentItem;
+use codex_code_mode_protocol::NotificationFuture;
+use codex_code_mode_protocol::RuntimeResponse;
+use codex_code_mode_protocol::StartedCell;
+use codex_code_mode_protocol::ToolInvocationFuture;
+use codex_code_mode_protocol::WaitOutcome;
+use codex_code_mode_protocol::WaitRequest;
+use codex_code_mode_protocol::WaitToPendingOutcome;
+use codex_code_mode_protocol::WaitToPendingRequest;
 use serde_json::Value as JsonValue;
 use tokio::sync::Mutex;
 use tokio::sync::mpsc;
@@ -18,88 +32,12 @@ use tokio::task::JoinSet;
 use tokio_util::sync::CancellationToken;
 use tracing::warn;
 
-use crate::FunctionCallOutputContentItem;
-use crate::runtime::CodeModeNestedToolCall;
-use crate::runtime::DEFAULT_EXEC_YIELD_TIME_MS;
-use crate::runtime::ExecuteRequest;
-use crate::runtime::ExecuteToPendingOutcome;
 use crate::runtime::PendingRuntimeMode;
 use crate::runtime::RuntimeCommand;
 use crate::runtime::RuntimeControlCommand;
 use crate::runtime::RuntimeEvent;
-use crate::runtime::RuntimeResponse;
-use crate::runtime::WaitOutcome;
-use crate::runtime::WaitRequest;
-use crate::runtime::WaitToPendingOutcome;
-use crate::runtime::WaitToPendingRequest;
 use crate::runtime::spawn_runtime;
 
-pub type CodeModeSessionResultFuture<'a, T> =
-    Pin<Box<dyn Future<Output = Result<T, String>> + Send + 'a>>;
-pub type CodeModeSessionProviderFuture<'a> =
-    CodeModeSessionResultFuture<'a, Arc<dyn CodeModeSession>>;
-pub type ToolInvocationFuture<'a> =
-    Pin<Box<dyn Future<Output = Result<JsonValue, String>> + Send + 'a>>;
-pub type NotificationFuture<'a> = Pin<Box<dyn Future<Output = Result<(), String>> + Send + 'a>>;
-
-#[derive(Clone, Debug, Deserialize, Eq, Hash, PartialEq, Serialize)]
-pub struct CellId(String);
-
-impl CellId {
-    pub fn new(value: String) -> Self {
-        Self(value)
-    }
-
-    pub fn as_str(&self) -> &str {
-        &self.0
-    }
-}
-
-impl AsRef<str> for CellId {
-    fn as_ref(&self) -> &str {
-        self.as_str()
-    }
-}
-
-impl fmt::Display for CellId {
-    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
-        formatter.write_str(self.as_str())
-    }
-}
-
-pub struct StartedCell {
-    pub cell_id: CellId,
-    initial_response_rx: oneshot::Receiver<RuntimeResponse>,
-}
-
-impl StartedCell {
-    pub async fn initial_response(self) -> Result<RuntimeResponse, String> {
-        self.initial_response_rx
-            .await
-            .map_err(|_| "exec runtime ended unexpectedly".to_string())
-    }
-}
-
-/// Host callbacks used by a code-mode session while cells are executing.
-pub trait CodeModeSessionDelegate: Send + Sync {
-    fn invoke_tool<'a>(
-        &'a self,
-        invocation: CodeModeNestedToolCall,
-        cancellation_token: CancellationToken,
-    ) -> ToolInvocationFuture<'a>;
-
-    fn notify<'a>(
-        &'a self,
-        call_id: String,
-        cell_id: CellId,
-        text: String,
-        cancellation_token: CancellationToken,
-    ) -> NotificationFuture<'a>;
-
-    /// Releases delegate state associated with a cell after it reaches a terminal state.
-    fn cell_closed(&self, cell_id: &CellId);
-}
-
 pub struct NoopCodeModeSessionDelegate;
 
 impl CodeModeSessionDelegate for NoopCodeModeSessionDelegate {
@@ -127,35 +65,6 @@ impl CodeModeSessionDelegate for NoopCodeModeSessionDelegate {
     fn cell_closed(&self, _cell_id: &CellId) {}
 }
 
-/// A durable code-mode session owned by one Codex thread.
-///
-/// Cells executed in the same session share stored values. Separate sessions
-/// must keep those values isolated. Implementations may execute cells
-/// in-process or remotely.
-pub trait CodeModeSession: Send + Sync {
-    fn execute<'a>(
-        &'a self,
-        request: ExecuteRequest,
-    ) -> CodeModeSessionResultFuture<'a, StartedCell>;
-
-    fn wait<'a>(&'a self, request: WaitRequest) -> CodeModeSessionResultFuture<'a, WaitOutcome>;
-
-    fn terminate<'a>(&'a self, cell_id: CellId) -> CodeModeSessionResultFuture<'a, WaitOutcome>;
-
-    fn shutdown<'a>(&'a self) -> CodeModeSessionResultFuture<'a, ()>;
-}
-
-/// Creates code-mode sessions for one Codex thread.
-///
-/// Providers choose where a session executes and receive the host delegate that
-/// the session should use for nested tool calls and notifications.
-pub trait CodeModeSessionProvider: Send + Sync {
-    fn create_session<'a>(
-        &'a self,
-        delegate: Arc<dyn CodeModeSessionDelegate>,
-    ) -> CodeModeSessionProviderFuture<'a>;
-}
-
 #[derive(Default)]
 pub struct InProcessCodeModeSessionProvider;
 
@@ -233,10 +142,7 @@ impl CodeModeService {
         )
         .await?;
 
-        Ok(StartedCell {
-            cell_id,
-            initial_response_rx: response_rx,
-        })
+        Ok(StartedCell::new(cell_id, response_rx))
     }
 
     pub async fn execute_to_pending(
@@ -432,6 +338,10 @@ impl Drop for CodeModeService {
 }
 
 impl CodeModeSession for CodeModeService {
+    fn is_alive(&self) -> bool {
+        !self.inner.shutting_down.load(Ordering::Acquire)
+    }
+
     fn execute<'a>(
         &'a self,
         request: ExecuteRequest,
@@ -876,10 +786,10 @@ mod tests {
     use super::WaitToPendingRequest;
     use super::run_cell_control;
     use crate::CodeModeToolKind;
+    use crate::ExecuteRequest;
+    use crate::ExecuteToPendingOutcome;
     use crate::FunctionCallOutputContentItem;
     use crate::ToolDefinition;
-    use crate::runtime::ExecuteRequest;
-    use crate::runtime::ExecuteToPendingOutcome;
     use crate::runtime::RuntimeEvent;
     use crate::runtime::spawn_runtime;