diff --git a/codex-rs/Cargo.lock b/codex-rs/Cargo.lock
index 139ae3985f..bb5c8a6ba5 100644
--- a/codex-rs/Cargo.lock
+++ b/codex-rs/Cargo.lock
@@ -2490,6 +2490,16 @@ dependencies = [
  "v8",
 ]
 
+[[package]]
+name = "codex-code-mode-client"
+version = "0.0.0"
+dependencies = [
+ "codex-code-mode-protocol",
+ "tokio",
+ "tokio-util",
+ "tracing",
+]
+
 [[package]]
 name = "codex-code-mode-host"
 version = "0.0.0"
diff --git a/codex-rs/Cargo.toml b/codex-rs/Cargo.toml
index 8ce5126823..9b6e4e95a9 100644
--- a/codex-rs/Cargo.toml
+++ b/codex-rs/Cargo.toml
@@ -21,6 +21,7 @@ members = [
     "install-context",
     "codex-backend-openapi-models",
     "code-mode",
+    "code-mode-client",
     "code-mode-host",
     "code-mode-protocol",
     "codex-home",
@@ -160,6 +161,7 @@ codex-cloud-config = { path = "cloud-config" }
 codex-cloud-tasks-client = { path = "cloud-tasks-client" }
 codex-cloud-tasks-mock-client = { path = "cloud-tasks-mock-client" }
 codex-code-mode = { path = "code-mode" }
+codex-code-mode-client = { path = "code-mode-client" }
 codex-code-mode-protocol = { path = "code-mode-protocol" }
 codex-home = { path = "codex-home" }
 codex-config = { path = "config" }
diff --git a/codex-rs/code-mode-client/BUILD.bazel b/codex-rs/code-mode-client/BUILD.bazel
new file mode 100644
index 0000000000..071598cc2c
--- /dev/null
+++ b/codex-rs/code-mode-client/BUILD.bazel
@@ -0,0 +1,6 @@
+load("//:defs.bzl", "codex_rust_crate")
+
+codex_rust_crate(
+    name = "code-mode-client",
+    crate_name = "codex_code_mode_client",
+)
diff --git a/codex-rs/code-mode-client/Cargo.toml b/codex-rs/code-mode-client/Cargo.toml
new file mode 100644
index 0000000000..585c6ca261
--- /dev/null
+++ b/codex-rs/code-mode-client/Cargo.toml
@@ -0,0 +1,19 @@
+[package]
+edition.workspace = true
+license.workspace = true
+name = "codex-code-mode-client"
+version.workspace = true
+
+[lib]
+doctest = false
+name = "codex_code_mode_client"
+path = "src/lib.rs"
+
+[lints]
+workspace = true
+
+[dependencies]
+codex-code-mode-protocol = { workspace = true }
+tokio = { workspace = true, features = ["io-std", "io-util", "process", "rt", "sync"] }
+tokio-util = { workspace = true, features = ["rt"] }
+tracing = { workspace = true }
diff --git a/codex-rs/code-mode-client/src/connection.rs b/codex-rs/code-mode-client/src/connection.rs
new file mode 100644
index 0000000000..4419c3be4f
--- /dev/null
+++ b/codex-rs/code-mode-client/src/connection.rs
@@ -0,0 +1,416 @@
+use std::collections::HashMap;
+use std::process::Stdio;
+use std::sync::Arc;
+use std::sync::Weak;
+use std::sync::atomic::AtomicBool;
+use std::sync::atomic::AtomicU64;
+use std::sync::atomic::Ordering;
+
+use codex_code_mode_protocol::CodeModeSessionDelegate;
+use codex_code_mode_protocol::ExecuteRequest;
+use codex_code_mode_protocol::StartedCell;
+use codex_code_mode_protocol::wire::ClientMessage;
+use codex_code_mode_protocol::wire::DelegateRequest;
+use codex_code_mode_protocol::wire::DelegateRequestId;
+use codex_code_mode_protocol::wire::DelegateResponse;
+use codex_code_mode_protocol::wire::HostMessage;
+use codex_code_mode_protocol::wire::HostRequest;
+use codex_code_mode_protocol::wire::HostResponse;
+use codex_code_mode_protocol::wire::RequestId;
+use codex_code_mode_protocol::wire::SessionId;
+use codex_code_mode_protocol::wire::read_frame;
+use codex_code_mode_protocol::wire::write_frame;
+use tokio::io::AsyncBufReadExt;
+use tokio::io::BufReader;
+use tokio::process::Command;
+use tokio::sync::Mutex;
+use tokio::sync::mpsc;
+use tokio::sync::oneshot;
+use tokio_util::sync::CancellationToken;
+use tracing::debug;
+use tracing::warn;
+
+use crate::CodeModeHostCommand;
+
+const IPC_CHANNEL_CAPACITY: usize = 128;
+
+pub(super) struct Connection {
+    state: Arc<ConnectionState>,
+    cancellation: CancellationToken,
+}
+
+impl Connection {
+    pub(super) async fn spawn(command: &CodeModeHostCommand) -> Result<Self, String> {
+        let mut child = host_process(command)
+            .stdin(Stdio::piped())
+            .stdout(Stdio::piped())
+            .stderr(Stdio::piped())
+            .kill_on_drop(true)
+            .spawn()
+            .map_err(|err| {
+                format!(
+                    "failed to spawn code-mode host {}: {err}",
+                    command.program.display()
+                )
+            })?;
+        let stdin = child
+            .stdin
+            .take()
+            .ok_or_else(|| "spawned code-mode host has no stdin".to_string())?;
+        let stdout = child
+            .stdout
+            .take()
+            .ok_or_else(|| "spawned code-mode host has no stdout".to_string())?;
+        let stderr = child.stderr.take();
+        let (outgoing_tx, mut outgoing_rx) = mpsc::channel(IPC_CHANNEL_CAPACITY);
+        let cancellation = CancellationToken::new();
+        let state = Arc::new(ConnectionState::new(outgoing_tx));
+
+        let writer_state = Arc::downgrade(&state);
+        let writer_cancellation = cancellation.clone();
+        tokio::spawn(async move {
+            let mut stdin = stdin;
+            loop {
+                tokio::select! {
+                    _ = writer_cancellation.cancelled() => break,
+                    message = outgoing_rx.recv() => {
+                        let Some(message) = message else {
+                            break;
+                        };
+                        if let Err(err) = write_frame(&mut stdin, &message).await {
+                            warn!("failed to write code-mode host message: {err}");
+                            if let Some(state) = writer_state.upgrade() {
+                                state
+                                    .fail(format!("failed to write code-mode host message: {err}"))
+                                    .await;
+                            }
+                            break;
+                        }
+                    }
+                }
+            }
+        });
+
+        let reader_state = Arc::downgrade(&state);
+        let reader_cancellation = cancellation.clone();
+        tokio::spawn(async move {
+            drive_reader(stdout, reader_state, reader_cancellation).await;
+        });
+
+        if let Some(stderr) = stderr {
+            tokio::spawn(async move {
+                let mut lines = BufReader::new(stderr).lines();
+                loop {
+                    match lines.next_line().await {
+                        Ok(Some(line)) => debug!("code-mode host stderr: {line}"),
+                        Ok(None) => break,
+                        Err(err) => {
+                            warn!("failed to read code-mode host stderr: {err}");
+                            break;
+                        }
+                    }
+                }
+            });
+        }
+
+        let supervisor_state = Arc::downgrade(&state);
+        let supervisor_cancellation = cancellation.clone();
+        tokio::spawn(async move {
+            tokio::select! {
+                result = child.wait() => {
+                    let reason = match result {
+                        Ok(status) => format!("code-mode host exited with status {status}"),
+                        Err(err) => format!("failed waiting for code-mode host: {err}"),
+                    };
+                    if let Some(state) = supervisor_state.upgrade() {
+                        state.fail(reason).await;
+                    }
+                }
+                _ = supervisor_cancellation.cancelled() => {
+                    let _ = child.start_kill();
+                    let _ = child.wait().await;
+                }
+            }
+        });
+
+        Ok(Self {
+            state,
+            cancellation,
+        })
+    }
+
+    pub(super) fn is_alive(&self) -> bool {
+        self.state.alive.load(Ordering::Acquire)
+    }
+
+    pub(super) async fn request(&self, request: HostRequest) -> Result<HostResponse, String> {
+        let id = self.state.next_request_id.fetch_add(1, Ordering::Relaxed);
+        let (response_tx, response_rx) = oneshot::channel();
+        self.state.pending.lock().await.insert(id, response_tx);
+        if let Err(err) = self
+            .state
+            .send(ClientMessage::Request { id, request })
+            .await
+        {
+            self.state.pending.lock().await.remove(&id);
+            return Err(err);
+        }
+        response_rx
+            .await
+            .map_err(|_| self.state.failure_message())?
+    }
+
+    pub(super) async fn execute(
+        &self,
+        session_id: SessionId,
+        request: ExecuteRequest,
+    ) -> Result<StartedCell, String> {
+        let id = self.state.next_request_id.fetch_add(1, Ordering::Relaxed);
+        let (response_tx, response_rx) = oneshot::channel();
+        let (initial_tx, initial_rx) = oneshot::channel();
+        self.state.pending.lock().await.insert(id, response_tx);
+        self.state
+            .initial_responses
+            .lock()
+            .await
+            .insert(id, initial_tx);
+        if let Err(err) = self
+            .state
+            .send(ClientMessage::Request {
+                id,
+                request: HostRequest::Execute {
+                    session_id,
+                    request,
+                },
+            })
+            .await
+        {
+            self.state.pending.lock().await.remove(&id);
+            self.state.initial_responses.lock().await.remove(&id);
+            return Err(err);
+        }
+        let response = match response_rx.await {
+            Ok(Ok(response)) => response,
+            Ok(Err(err)) => {
+                self.state.initial_responses.lock().await.remove(&id);
+                return Err(err);
+            }
+            Err(_) => {
+                self.state.initial_responses.lock().await.remove(&id);
+                return Err(self.state.failure_message());
+            }
+        };
+        match response {
+            HostResponse::ExecutionStarted { cell_id } => {
+                Ok(StartedCell::from_result_receiver(cell_id, initial_rx))
+            }
+            _ => {
+                self.state.initial_responses.lock().await.remove(&id);
+                Err("code-mode host returned an invalid execute response".to_string())
+            }
+        }
+    }
+
+    pub(super) async fn register_delegate(
+        &self,
+        session_id: SessionId,
+        delegate: Arc<dyn CodeModeSessionDelegate>,
+    ) {
+        self.state
+            .delegates
+            .lock()
+            .await
+            .insert(session_id, delegate);
+    }
+
+    pub(super) async fn remove_delegate(&self, session_id: SessionId) {
+        self.state.delegates.lock().await.remove(&session_id);
+    }
+}
+
+impl Drop for Connection {
+    fn drop(&mut self) {
+        self.cancellation.cancel();
+    }
+}
+
+struct ConnectionState {
+    outgoing_tx: mpsc::Sender<ClientMessage>,
+    pending: Mutex<HashMap<RequestId, oneshot::Sender<Result<HostResponse, String>>>>,
+    initial_responses: Mutex<
+        HashMap<
+            RequestId,
+            oneshot::Sender<Result<codex_code_mode_protocol::RuntimeResponse, String>>,
+        >,
+    >,
+    delegates: Mutex<HashMap<SessionId, Arc<dyn CodeModeSessionDelegate>>>,
+    delegate_cancellations: Mutex<HashMap<DelegateRequestId, CancellationToken>>,
+    next_request_id: AtomicU64,
+    alive: AtomicBool,
+    failure: std::sync::Mutex<Option<String>>,
+}
+
+impl ConnectionState {
+    fn new(outgoing_tx: mpsc::Sender<ClientMessage>) -> Self {
+        Self {
+            outgoing_tx,
+            pending: Mutex::new(HashMap::new()),
+            initial_responses: Mutex::new(HashMap::new()),
+            delegates: Mutex::new(HashMap::new()),
+            delegate_cancellations: Mutex::new(HashMap::new()),
+            next_request_id: AtomicU64::new(1),
+            alive: AtomicBool::new(true),
+            failure: std::sync::Mutex::new(None),
+        }
+    }
+
+    async fn send(&self, message: ClientMessage) -> Result<(), String> {
+        if !self.alive.load(Ordering::Acquire) {
+            return Err(self.failure_message());
+        }
+        self.outgoing_tx
+            .send(message)
+            .await
+            .map_err(|_| self.failure_message())
+    }
+
+    fn failure_message(&self) -> String {
+        self.failure
+            .lock()
+            .ok()
+            .and_then(|failure| failure.clone())
+            .unwrap_or_else(|| "code-mode host connection closed".to_string())
+    }
+
+    async fn fail(&self, reason: String) {
+        if !self.alive.swap(false, Ordering::AcqRel) {
+            return;
+        }
+        warn!(%reason, "code-mode host connection failed");
+        if let Ok(mut failure) = self.failure.lock() {
+            *failure = Some(reason.clone());
+        }
+        for (_, sender) in self.pending.lock().await.drain() {
+            let _ = sender.send(Err(reason.clone()));
+        }
+        self.initial_responses.lock().await.clear();
+        for (_, cancellation) in self.delegate_cancellations.lock().await.drain() {
+            cancellation.cancel();
+        }
+    }
+}
+
+async fn drive_reader(
+    mut stdout: tokio::process::ChildStdout,
+    state: Weak<ConnectionState>,
+    cancellation: CancellationToken,
+) {
+    loop {
+        let message = tokio::select! {
+            _ = cancellation.cancelled() => return,
+            result = read_frame::<_, HostMessage>(&mut stdout) => result,
+        };
+        match message {
+            Ok(Some(message)) => {
+                let Some(state) = state.upgrade() else {
+                    return;
+                };
+                handle_host_message(state, message).await;
+            }
+            Ok(None) => {
+                if let Some(state) = state.upgrade() {
+                    state
+                        .fail("code-mode host closed its stdout".to_string())
+                        .await;
+                }
+                return;
+            }
+            Err(err) => {
+                if let Some(state) = state.upgrade() {
+                    state
+                        .fail(format!("failed to read code-mode host message: {err}"))
+                        .await;
+                }
+                return;
+            }
+        }
+    }
+}
+
+async fn handle_host_message(state: Arc<ConnectionState>, message: HostMessage) {
+    match message {
+        HostMessage::Response { id, response } => {
+            if let Some(sender) = state.pending.lock().await.remove(&id) {
+                let _ = sender.send(response);
+            }
+        }
+        HostMessage::InitialResponse { id, response } => {
+            if let Some(sender) = state.initial_responses.lock().await.remove(&id) {
+                let _ = sender.send(response);
+            }
+        }
+        HostMessage::DelegateRequest {
+            id,
+            session_id,
+            request,
+        } => {
+            let delegate = state.delegates.lock().await.get(&session_id).cloned();
+            let Some(delegate) = delegate else {
+                let _ = state
+                    .send(ClientMessage::DelegateResponse {
+                        id,
+                        response: Err(format!("unknown code-mode session {session_id}")),
+                    })
+                    .await;
+                return;
+            };
+            let cancellation = CancellationToken::new();
+            state
+                .delegate_cancellations
+                .lock()
+                .await
+                .insert(id, cancellation.clone());
+            tokio::spawn(async move {
+                let response = match request {
+                    DelegateRequest::InvokeTool(invocation) => delegate
+                        .invoke_tool(invocation, cancellation)
+                        .await
+                        .map(DelegateResponse::ToolResult),
+                    DelegateRequest::Notify {
+                        call_id,
+                        cell_id,
+                        text,
+                    } => delegate
+                        .notify(call_id, cell_id, text, cancellation)
+                        .await
+                        .map(|()| DelegateResponse::NotificationDelivered),
+                };
+                state.delegate_cancellations.lock().await.remove(&id);
+                let _ = state
+                    .send(ClientMessage::DelegateResponse { id, response })
+                    .await;
+            });
+        }
+        HostMessage::CancelDelegateRequest { id } => {
+            if let Some(cancellation) = state.delegate_cancellations.lock().await.remove(&id) {
+                cancellation.cancel();
+            }
+        }
+        HostMessage::CellClosed {
+            session_id,
+            cell_id,
+        } => {
+            if let Some(delegate) = state.delegates.lock().await.get(&session_id).cloned() {
+                delegate.cell_closed(&cell_id);
+            }
+        }
+    }
+}
+
+fn host_process(command: &CodeModeHostCommand) -> Command {
+    let mut process = Command::new(&command.program);
+    process.args(&command.args);
+    #[cfg(unix)]
+    process.process_group(0);
+    process
+}
diff --git a/codex-rs/code-mode-client/src/lib.rs b/codex-rs/code-mode-client/src/lib.rs
new file mode 100644
index 0000000000..f08cc803f4
--- /dev/null
+++ b/codex-rs/code-mode-client/src/lib.rs
@@ -0,0 +1,235 @@
+use std::path::PathBuf;
+use std::sync::Arc;
+use std::sync::atomic::AtomicBool;
+use std::sync::atomic::Ordering;
+
+use codex_code_mode_protocol::CellId;
+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::ExecuteRequest;
+use codex_code_mode_protocol::StartedCell;
+use codex_code_mode_protocol::WaitOutcome;
+use codex_code_mode_protocol::WaitRequest;
+use codex_code_mode_protocol::wire::HostRequest;
+use codex_code_mode_protocol::wire::HostResponse;
+use codex_code_mode_protocol::wire::SessionId;
+use tokio::sync::Semaphore;
+
+const CODE_MODE_HOST_PATH_ENV: &str = "CODEX_CODE_MODE_HOST_PATH";
+
+mod connection;
+
+use connection::Connection;
+
+#[derive(Clone, Debug)]
+pub struct CodeModeHostCommand {
+    pub program: PathBuf,
+    pub args: Vec<String>,
+}
+
+impl Default for CodeModeHostCommand {
+    fn default() -> Self {
+        Self {
+            program: default_host_program(),
+            args: Vec::new(),
+        }
+    }
+}
+
+pub struct IpcCodeModeSessionProvider {
+    command: CodeModeHostCommand,
+    connection: std::sync::Mutex<Option<Arc<Connection>>>,
+    spawn_permit: Semaphore,
+}
+
+impl Default for IpcCodeModeSessionProvider {
+    fn default() -> Self {
+        Self::new(CodeModeHostCommand::default())
+    }
+}
+
+impl IpcCodeModeSessionProvider {
+    pub fn new(command: CodeModeHostCommand) -> Self {
+        Self {
+            command,
+            connection: std::sync::Mutex::new(None),
+            spawn_permit: Semaphore::new(/*permits*/ 1),
+        }
+    }
+
+    async fn connection(&self) -> Result<Arc<Connection>, String> {
+        if let Some(connection) = {
+            let current = self
+                .connection
+                .lock()
+                .map_err(|_| "code-mode host connection lock poisoned".to_string())?;
+            current
+                .as_ref()
+                .filter(|connection| connection.is_alive())
+                .cloned()
+        } {
+            return Ok(connection);
+        }
+
+        let _spawn_permit = self
+            .spawn_permit
+            .acquire()
+            .await
+            .map_err(|_| "code-mode host spawn coordinator closed".to_string())?;
+        if let Some(connection) = {
+            let current = self
+                .connection
+                .lock()
+                .map_err(|_| "code-mode host connection lock poisoned".to_string())?;
+            current
+                .as_ref()
+                .filter(|connection| connection.is_alive())
+                .cloned()
+        } {
+            return Ok(connection);
+        }
+        let connection = Arc::new(Connection::spawn(&self.command).await?);
+        *self
+            .connection
+            .lock()
+            .map_err(|_| "code-mode host connection lock poisoned".to_string())? =
+            Some(Arc::clone(&connection));
+        Ok(connection)
+    }
+}
+
+impl CodeModeSessionProvider for IpcCodeModeSessionProvider {
+    fn create_session<'a>(
+        &'a self,
+        delegate: Arc<dyn CodeModeSessionDelegate>,
+    ) -> CodeModeSessionProviderFuture<'a> {
+        Box::pin(async move {
+            let connection = self.connection().await?;
+            let response = connection.request(HostRequest::CreateSession).await?;
+            let HostResponse::SessionCreated { session_id } = response else {
+                return Err(
+                    "code-mode host returned an invalid create-session response".to_string()
+                );
+            };
+            connection.register_delegate(session_id, delegate).await;
+            let session: Arc<dyn CodeModeSession> = Arc::new(IpcCodeModeSession {
+                connection,
+                session_id,
+                shutdown: AtomicBool::new(false),
+            });
+            Ok(session)
+        })
+    }
+}
+
+struct IpcCodeModeSession {
+    connection: Arc<Connection>,
+    session_id: SessionId,
+    shutdown: AtomicBool,
+}
+
+impl CodeModeSession for IpcCodeModeSession {
+    fn is_alive(&self) -> bool {
+        !self.shutdown.load(Ordering::Acquire) && self.connection.is_alive()
+    }
+
+    fn execute<'a>(
+        &'a self,
+        request: ExecuteRequest,
+    ) -> CodeModeSessionResultFuture<'a, StartedCell> {
+        Box::pin(async move {
+            self.ensure_active()?;
+            self.connection.execute(self.session_id, request).await
+        })
+    }
+
+    fn wait<'a>(&'a self, request: WaitRequest) -> CodeModeSessionResultFuture<'a, WaitOutcome> {
+        Box::pin(async move {
+            self.ensure_active()?;
+            let response = self
+                .connection
+                .request(HostRequest::Wait {
+                    session_id: self.session_id,
+                    request,
+                })
+                .await?;
+            match response {
+                HostResponse::WaitCompleted { outcome } => Ok(outcome),
+                _ => Err("code-mode host returned an invalid wait response".to_string()),
+            }
+        })
+    }
+
+    fn terminate<'a>(&'a self, cell_id: CellId) -> CodeModeSessionResultFuture<'a, WaitOutcome> {
+        Box::pin(async move {
+            self.ensure_active()?;
+            let response = self
+                .connection
+                .request(HostRequest::Terminate {
+                    session_id: self.session_id,
+                    cell_id,
+                })
+                .await?;
+            match response {
+                HostResponse::WaitCompleted { outcome } => Ok(outcome),
+                _ => Err("code-mode host returned an invalid terminate response".to_string()),
+            }
+        })
+    }
+
+    fn shutdown<'a>(&'a self) -> CodeModeSessionResultFuture<'a, ()> {
+        Box::pin(async move {
+            if self.shutdown.swap(true, Ordering::AcqRel) {
+                return Ok(());
+            }
+            let result = self
+                .connection
+                .request(HostRequest::ShutdownSession {
+                    session_id: self.session_id,
+                })
+                .await;
+            self.connection.remove_delegate(self.session_id).await;
+            match result? {
+                HostResponse::SessionShutdown => Ok(()),
+                _ => Err("code-mode host returned an invalid shutdown response".to_string()),
+            }
+        })
+    }
+}
+
+impl IpcCodeModeSession {
+    fn ensure_active(&self) -> Result<(), String> {
+        if self.shutdown.load(Ordering::Acquire) {
+            Err("code mode session is shutting down".to_string())
+        } else {
+            Ok(())
+        }
+    }
+}
+
+fn default_host_program() -> PathBuf {
+    if let Some(path) = std::env::var_os(CODE_MODE_HOST_PATH_ENV) {
+        return PathBuf::from(path);
+    }
+    let executable_name = if cfg!(windows) {
+        "codex-code-mode-host.exe"
+    } else {
+        "codex-code-mode-host"
+    };
+    if let Ok(current_exe) = std::env::current_exe()
+        && let Some(parent) = current_exe.parent()
+    {
+        let sibling = parent.join(executable_name);
+        if sibling.is_file() {
+            return sibling;
+        }
+    }
+    PathBuf::from(executable_name)
+}
+
+#[cfg(test)]
+#[path = "tests.rs"]
+mod tests;
diff --git a/codex-rs/code-mode-client/src/tests.rs b/codex-rs/code-mode-client/src/tests.rs
new file mode 100644
index 0000000000..3b38f03fc3
--- /dev/null
+++ b/codex-rs/code-mode-client/src/tests.rs
@@ -0,0 +1,53 @@
+use std::path::PathBuf;
+use std::sync::Arc;
+
+use codex_code_mode_protocol::CellId;
+use codex_code_mode_protocol::CodeModeNestedToolCall;
+use codex_code_mode_protocol::CodeModeSessionDelegate;
+use codex_code_mode_protocol::CodeModeSessionProvider;
+use codex_code_mode_protocol::NotificationFuture;
+use codex_code_mode_protocol::ToolInvocationFuture;
+use tokio_util::sync::CancellationToken;
+
+use super::CodeModeHostCommand;
+use super::IpcCodeModeSessionProvider;
+
+struct TestDelegate;
+
+impl CodeModeSessionDelegate for TestDelegate {
+    fn invoke_tool<'a>(
+        &'a self,
+        _invocation: CodeModeNestedToolCall,
+        _cancellation_token: CancellationToken,
+    ) -> ToolInvocationFuture<'a> {
+        Box::pin(async { Err("unexpected tool invocation".to_string()) })
+    }
+
+    fn notify<'a>(
+        &'a self,
+        _call_id: String,
+        _cell_id: CellId,
+        _text: String,
+        _cancellation_token: CancellationToken,
+    ) -> NotificationFuture<'a> {
+        Box::pin(async { Ok(()) })
+    }
+
+    fn cell_closed(&self, _cell_id: &CellId) {}
+}
+
+#[tokio::test]
+async fn create_session_reports_host_spawn_errors() {
+    let provider = IpcCodeModeSessionProvider::new(CodeModeHostCommand {
+        program: PathBuf::from("codex-code-mode-host-does-not-exist"),
+        args: Vec::new(),
+    });
+
+    let error = provider
+        .create_session(Arc::new(TestDelegate))
+        .await
+        .err()
+        .expect("session creation should fail");
+
+    assert!(error.contains("failed to spawn code-mode host"));
+}