diff --git a/codex-rs/core/src/exec.rs b/codex-rs/core/src/exec.rs
index a5a88ee9..5301f022 100644
--- a/codex-rs/core/src/exec.rs
+++ b/codex-rs/core/src/exec.rs
@@ -22,8 +22,8 @@ use crate::error::Result;
 use crate::error::SandboxErr;
 use crate::protocol::Event;
 use crate::protocol::EventMsg;
-use crate::protocol::ExecCommandStderrDeltaEvent;
-use crate::protocol::ExecCommandStdoutDeltaEvent;
+use crate::protocol::ExecCommandOutputDeltaEvent;
+use crate::protocol::ExecOutputStream;
 use crate::protocol::SandboxPolicy;
 use crate::seatbelt::spawn_command_under_seatbelt;
 use crate::spawn::StdioPolicy;
@@ -359,17 +359,15 @@ async fn read_capped<R: AsyncRead + Unpin + Send + 'static>(
 
         if let Some(stream) = &stream {
             let chunk = tmp[..n].to_vec();
-            let msg = if is_stderr {
-                EventMsg::ExecCommandStderrDelta(ExecCommandStderrDeltaEvent {
-                    call_id: stream.call_id.clone(),
-                    chunk: ByteBuf::from(chunk),
-                })
-            } else {
-                EventMsg::ExecCommandStdoutDelta(ExecCommandStdoutDeltaEvent {
-                    call_id: stream.call_id.clone(),
-                    chunk: ByteBuf::from(chunk),
-                })
-            };
+            let msg = EventMsg::ExecCommandOutputDelta(ExecCommandOutputDeltaEvent {
+                call_id: stream.call_id.clone(),
+                stream: if is_stderr {
+                    ExecOutputStream::Stderr
+                } else {
+                    ExecOutputStream::Stdout
+                },
+                chunk: ByteBuf::from(chunk),
+            });
             let event = Event {
                 id: stream.sub_id.clone(),
                 msg,
diff --git a/codex-rs/core/src/protocol.rs b/codex-rs/core/src/protocol.rs
index 8d26eda9..3be0c92c 100644
--- a/codex-rs/core/src/protocol.rs
+++ b/codex-rs/core/src/protocol.rs
@@ -324,11 +324,8 @@ pub enum EventMsg {
     /// Notification that the server is about to execute a command.
     ExecCommandBegin(ExecCommandBeginEvent),
 
-    /// Incremental chunk of stdout from a running command.
-    ExecCommandStdoutDelta(ExecCommandStdoutDeltaEvent),
-
-    /// Incremental chunk of stderr from a running command.
-    ExecCommandStderrDelta(ExecCommandStderrDeltaEvent),
+    /// Incremental chunk of output from a running command.
+    ExecCommandOutputDelta(ExecCommandOutputDeltaEvent),
 
     ExecCommandEnd(ExecCommandEndEvent),
 
@@ -484,19 +481,19 @@ pub struct ExecCommandEndEvent {
 }
 
 #[derive(Debug, Clone, Deserialize, Serialize)]
-pub struct ExecCommandStdoutDeltaEvent {
-    /// Identifier for the ExecCommandBegin that produced this chunk.
-    pub call_id: String,
-    /// Raw stdout bytes (may not be valid UTF-8).
-    #[serde(with = "serde_bytes")]
-    pub chunk: ByteBuf,
+#[serde(rename_all = "snake_case")]
+pub enum ExecOutputStream {
+    Stdout,
+    Stderr,
 }
 
 #[derive(Debug, Clone, Deserialize, Serialize)]
-pub struct ExecCommandStderrDeltaEvent {
+pub struct ExecCommandOutputDeltaEvent {
     /// Identifier for the ExecCommandBegin that produced this chunk.
     pub call_id: String,
-    /// Raw stderr bytes (may not be valid UTF-8).
+    /// Which stream produced this chunk.
+    pub stream: ExecOutputStream,
+    /// Raw bytes from the stream (may not be valid UTF-8).
     #[serde(with = "serde_bytes")]
     pub chunk: ByteBuf,
 }
diff --git a/codex-rs/core/tests/exec_stream_events.rs b/codex-rs/core/tests/exec_stream_events.rs
index 059b69a0..50f6888f 100644
--- a/codex-rs/core/tests/exec_stream_events.rs
+++ b/codex-rs/core/tests/exec_stream_events.rs
@@ -11,15 +11,19 @@ use codex_core::exec::StdoutStream;
 use codex_core::exec::process_exec_tool_call;
 use codex_core::protocol::Event;
 use codex_core::protocol::EventMsg;
-use codex_core::protocol::ExecCommandStderrDeltaEvent;
-use codex_core::protocol::ExecCommandStdoutDeltaEvent;
+use codex_core::protocol::ExecCommandOutputDeltaEvent;
+use codex_core::protocol::ExecOutputStream;
 use codex_core::protocol::SandboxPolicy;
 use tokio::sync::Notify;
 
 fn collect_stdout_events(rx: Receiver<Event>) -> Vec<u8> {
     let mut out = Vec::new();
     while let Ok(ev) = rx.try_recv() {
-        if let EventMsg::ExecCommandStdoutDelta(ExecCommandStdoutDeltaEvent { chunk, .. }) = ev.msg
+        if let EventMsg::ExecCommandOutputDelta(ExecCommandOutputDeltaEvent {
+            stream: ExecOutputStream::Stdout,
+            chunk,
+            ..
+        }) = ev.msg
         {
             out.extend_from_slice(&chunk);
         }
@@ -126,7 +130,11 @@ async fn test_exec_stderr_stream_events_echo() {
     // Collect only stderr delta events
     let mut err = Vec::new();
     while let Ok(ev) = rx.try_recv() {
-        if let EventMsg::ExecCommandStderrDelta(ExecCommandStderrDeltaEvent { chunk, .. }) = ev.msg
+        if let EventMsg::ExecCommandOutputDelta(ExecCommandOutputDeltaEvent {
+            stream: ExecOutputStream::Stderr,
+            chunk,
+            ..
+        }) = ev.msg
         {
             err.extend_from_slice(&chunk);
         }
diff --git a/codex-rs/exec/src/event_processor_with_human_output.rs b/codex-rs/exec/src/event_processor_with_human_output.rs
index 05643c62..7393ab72 100644
--- a/codex-rs/exec/src/event_processor_with_human_output.rs
+++ b/codex-rs/exec/src/event_processor_with_human_output.rs
@@ -239,8 +239,7 @@ impl EventProcessor for EventProcessorWithHumanOutput {
                     cwd.to_string_lossy(),
                 );
             }
-            EventMsg::ExecCommandStdoutDelta(_) => {}
-            EventMsg::ExecCommandStderrDelta(_) => {}
+            EventMsg::ExecCommandOutputDelta(_) => {}
             EventMsg::ExecCommandEnd(ExecCommandEndEvent {
                 call_id,
                 stdout,
diff --git a/codex-rs/mcp-server/src/codex_tool_runner.rs b/codex-rs/mcp-server/src/codex_tool_runner.rs
index 94d47f74..d489ffe0 100644
--- a/codex-rs/mcp-server/src/codex_tool_runner.rs
+++ b/codex-rs/mcp-server/src/codex_tool_runner.rs
@@ -258,8 +258,7 @@ async fn run_codex_tool_session_inner(
                     | EventMsg::McpToolCallBegin(_)
                     | EventMsg::McpToolCallEnd(_)
                     | EventMsg::ExecCommandBegin(_)
-                    | EventMsg::ExecCommandStdoutDelta(_)
-                    | EventMsg::ExecCommandStderrDelta(_)
+                    | EventMsg::ExecCommandOutputDelta(_)
                     | EventMsg::ExecCommandEnd(_)
                     | EventMsg::BackgroundEvent(_)
                     | EventMsg::PatchApplyBegin(_)
diff --git a/codex-rs/tui/src/chatwidget.rs b/codex-rs/tui/src/chatwidget.rs
index d6454c82..374a4b56 100644
--- a/codex-rs/tui/src/chatwidget.rs
+++ b/codex-rs/tui/src/chatwidget.rs
@@ -374,7 +374,7 @@ impl ChatWidget<'_> {
                 );
                 self.add_to_history(HistoryCell::new_active_exec_command(command));
             }
-            EventMsg::ExecCommandStdoutDelta(_) => {}
+            EventMsg::ExecCommandOutputDelta(_) => {}
             EventMsg::PatchApplyBegin(PatchApplyBeginEvent {
                 call_id: _,
                 auto_approved,