Include originating item IDs in MCP request metadata (#40866)

## What changed

- Add the originating Responses item ID to MCP tool request metadata as
  `_meta.itemId`.
- Preserve the initiating `exec` item ID across code-mode cells so nested MCP
  calls carry the same origin.

## Testing

- Cover metadata generation for direct and code-mode MCP tool calls.

GitOrigin-RevId: 1161cac64f1cc3a6d4dac4368e63804bd9d2c417

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

@@ -7,6 +7,7 @@ use codex_code_mode::CodeModeNestedToolCall;
 use codex_code_mode::CodeModeSessionDelegate;
 use codex_code_mode::NotificationFuture;
 use codex_code_mode::ToolInvocationFuture;
+use codex_protocol::ResponseItemId;
 use codex_protocol::models::FunctionCallOutputPayload;
 use codex_protocol::models::ResponseItem;
 use serde_json::Value as JsonValue;
@@ -24,7 +25,13 @@ use crate::tools::parallel::ToolCallRuntime;
 pub(super) struct CodeModeDispatchBroker {
     dispatch_tx: async_channel::Sender<DispatchMessage>,
     dispatch_rx: async_channel::Receiver<DispatchMessage>,
-    dispatch_gates: Arc<Mutex<HashMap<CellId, watch::Sender<bool>>>>,
+    dispatch_gates: Arc<Mutex<HashMap<CellId, CellDispatchGate>>>,
+}
+
+struct CellDispatchGate {
+    ready: watch::Sender<bool>,
+    // Keep the original exec item when later waits resume this cell.
+    originating_item_id: Option<ResponseItemId>,
 }
 
 impl CodeModeDispatchBroker {
@@ -37,8 +44,34 @@ impl CodeModeDispatchBroker {
         }
     }
 
-    pub(super) fn mark_cell_ready_for_dispatch(&self, cell_id: &CellId) {
-        dispatch_gate(&self.dispatch_gates, cell_id).send_replace(true);
+    pub(super) fn mark_cell_ready_for_dispatch(
+        &self,
+        cell_id: &CellId,
+        originating_item_id: Option<ResponseItemId>,
+    ) {
+        let ready = {
+            let mut dispatch_gates = self
+                .dispatch_gates
+                .lock()
+                .unwrap_or_else(std::sync::PoisonError::into_inner);
+            let gate = dispatch_gates
+                .entry(cell_id.clone())
+                .or_insert_with(|| CellDispatchGate {
+                    ready: watch::channel(false).0,
+                    originating_item_id: None,
+                });
+            gate.originating_item_id = originating_item_id;
+            gate.ready.clone()
+        };
+        ready.send_replace(true);
+    }
+
+    pub(super) fn cell_originating_item_id(&self, cell_id: &CellId) -> Option<ResponseItemId> {
+        self.dispatch_gates
+            .lock()
+            .unwrap_or_else(std::sync::PoisonError::into_inner)
+            .get(cell_id)
+            .and_then(|gate| gate.originating_item_id.clone())
     }
 
     pub(super) fn close_cell(&self, cell_id: &CellId) {
@@ -135,7 +168,7 @@ impl CodeModeDispatchBroker {
 }
 
 fn dispatch_gate(
-    dispatch_gates: &Mutex<HashMap<CellId, watch::Sender<bool>>>,
+    dispatch_gates: &Mutex<HashMap<CellId, CellDispatchGate>>,
     cell_id: &CellId,
 ) -> watch::Sender<bool> {
     let mut dispatch_gates = match dispatch_gates.lock() {
@@ -144,12 +177,16 @@ fn dispatch_gate(
     };
     dispatch_gates
         .entry(cell_id.clone())
-        .or_insert_with(|| watch::channel(false).0)
+        .or_insert_with(|| CellDispatchGate {
+            ready: watch::channel(false).0,
+            originating_item_id: None,
+        })
+        .ready
         .clone()
 }
 
 fn remove_dispatch_gate(
-    dispatch_gates: &Mutex<HashMap<CellId, watch::Sender<bool>>>,
+    dispatch_gates: &Mutex<HashMap<CellId, CellDispatchGate>>,
     cell_id: &CellId,
 ) {
     let mut dispatch_gates = match dispatch_gates.lock() {
@@ -160,7 +197,7 @@ fn remove_dispatch_gate(
 }
 
 async fn wait_until_cell_ready_for_dispatch(
-    dispatch_gates: &Mutex<HashMap<CellId, watch::Sender<bool>>>,
+    dispatch_gates: &Mutex<HashMap<CellId, CellDispatchGate>>,
     cell_id: &CellId,
     cancellation_token: &CancellationToken,
 ) -> bool {

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

@@ -35,6 +35,7 @@ impl CodeModeExecuteHandler {
         session: std::sync::Arc<crate::session::session::Session>,
         turn: std::sync::Arc<crate::session::turn_context::TurnContext>,
         call_id: String,
+        originating_item_id: Option<codex_protocol::ResponseItemId>,
         code: String,
         telemetry: &mut CodeModeToolCallGuard,
     ) -> Result<FunctionToolOutput, FunctionCallError> {
@@ -103,7 +104,7 @@ impl CodeModeExecuteHandler {
         exec.session
             .services
             .code_mode_service
-            .mark_cell_ready_for_dispatch(&cell_id);
+            .mark_cell_ready_for_dispatch(&cell_id, originating_item_id);
         let response = started_cell
             .initial_response()
             .await
@@ -155,6 +156,7 @@ impl CodeModeExecuteHandler {
         &self,
         invocation: ToolInvocation,
     ) -> Result<Box<dyn crate::tools::context::ToolOutput>, FunctionCallError> {
+        let originating_item_id = invocation.originating_item_id().await;
         let ToolInvocation {
             session,
             turn,
@@ -174,7 +176,14 @@ impl CodeModeExecuteHandler {
         );
         let result = match payload {
             ToolPayload::Custom { input } if is_exec_tool_name(&tool_name) => self
-                .execute(session, turn, call_id, input, &mut telemetry)
+                .execute(
+                    session,
+                    turn,
+                    call_id,
+                    originating_item_id,
+                    input,
+                    &mut telemetry,
+                )
                 .await
                 .map(boxed_tool_output),
             _ => Err(FunctionCallError::RespondToModel(format!(

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

@@ -176,8 +176,20 @@ impl CodeModeService {
         }
     }
 
-    pub(crate) fn mark_cell_ready_for_dispatch(&self, cell_id: &codex_code_mode::CellId) {
-        self.dispatch_broker.mark_cell_ready_for_dispatch(cell_id);
+    pub(crate) fn mark_cell_ready_for_dispatch(
+        &self,
+        cell_id: &codex_code_mode::CellId,
+        originating_item_id: Option<codex_protocol::ResponseItemId>,
+    ) {
+        self.dispatch_broker
+            .mark_cell_ready_for_dispatch(cell_id, originating_item_id);
+    }
+
+    pub(crate) fn cell_originating_item_id(
+        &self,
+        cell_id: &codex_code_mode::CellId,
+    ) -> Option<codex_protocol::ResponseItemId> {
+        self.dispatch_broker.cell_originating_item_id(cell_id)
     }
 
     pub(crate) fn finish_cell_dispatch(&self, cell_id: &CellId) {