Add join key for MAv2 inter-agent messages

codex-rs/core/src/compact_tests.rs

@@ -238,6 +238,7 @@ fn build_compacted_history_preserves_user_message_metadata() {
             message: "first user message".to_string(),
             metadata: Some(ResponseItemMetadata {
                 turn_id: Some("turn-1".to_string()),
+                ..Default::default()
             }),
         }],
         "summary text",

codex-rs/core/src/context_manager/history_tests.rs

@@ -1049,6 +1049,7 @@ fn record_items_truncates_function_call_output_content() {
         },
         metadata: Some(ResponseItemMetadata {
             turn_id: Some("turn-1".to_string()),
+            ..Default::default()
         }),
     };
 

codex-rs/core/src/session/tests.rs

@@ -1606,6 +1606,7 @@ async fn reconstruct_history_uses_replacement_history_verbatim() {
         phase: None,
         metadata: Some(ResponseItemMetadata {
             turn_id: Some("compact-turn".to_string()),
+            ..Default::default()
         }),
     };
     let replacement_history = vec![

codex-rs/core/src/tools/handlers/multi_agents_tests.rs

@@ -1195,6 +1195,11 @@ async fn multi_agent_v2_spawn_returns_path_and_send_message_accepts_relative_pat
                         && communication.other_recipients.is_empty()
                         && communication.content.is_empty()
                         && communication.encrypted_content.as_deref() == Some("encrypted-spawn-message")
+                        && communication
+                            .metadata
+                            .as_ref()
+                            .and_then(|metadata| metadata.source_call_id.as_deref())
+                            == Some("call-1")
                         && communication.trigger_turn
             )
     }));
@@ -1222,6 +1227,11 @@ async fn multi_agent_v2_spawn_returns_path_and_send_message_accepts_relative_pat
                         && communication.other_recipients.is_empty()
                         && communication.content.is_empty()
                         && communication.encrypted_content.as_deref() == Some("encrypted-send-message")
+                        && communication
+                            .metadata
+                            .as_ref()
+                            .and_then(|metadata| metadata.source_call_id.as_deref())
+                            == Some("call-1")
                         && !communication.trigger_turn
             )
     }));
@@ -2027,6 +2037,23 @@ async fn multi_agent_v2_followup_task_completion_notifies_parent_on_every_turn()
         .await
         .expect("followup_task should succeed");
 
+    assert!(manager.captured_ops().iter().any(|(id, op)| {
+        *id == agent_id
+            && matches!(
+                op,
+                Op::InterAgentCommunication { communication }
+                    if communication.author == AgentPath::root()
+                        && communication.recipient == worker_path
+                        && communication.encrypted_content.as_deref() == Some("continue")
+                        && communication
+                            .metadata
+                            .as_ref()
+                            .and_then(|metadata| metadata.source_call_id.as_deref())
+                            == Some("call-1")
+                        && communication.trigger_turn
+            )
+    }));
+
     let second_turn = thread.codex.session.new_default_turn().await;
     thread
         .codex

codex-rs/core/src/tools/handlers/multi_agents_v2/message_tool.rs

@@ -6,6 +6,7 @@
 use super::*;
 use crate::tools::context::FunctionToolOutput;
 use crate::turn_timing::now_unix_timestamp_ms;
+use codex_protocol::models::ResponseItemMetadata;
 use codex_protocol::protocol::InterAgentCommunication;
 
 #[derive(Clone, Copy, PartialEq, Eq)]
@@ -99,8 +100,12 @@ pub(crate) async fn handle_message_string_tool(
         .session_source
         .get_agent_path()
         .unwrap_or_else(AgentPath::root);
-    let communication =
+    let mut communication =
         communication_from_tool_message(author, receiver_agent_path.clone(), message);
+    communication
+        .metadata
+        .get_or_insert_with(ResponseItemMetadata::default)
+        .source_call_id = Some(call_id.clone());
     let result = session
         .services
         .agent_control

codex-rs/core/src/tools/handlers/multi_agents_v2/spawn.rs

@@ -8,6 +8,7 @@ use crate::tools::handlers::multi_agents_spec::SpawnAgentToolOptions;
 use crate::tools::handlers::multi_agents_spec::create_spawn_agent_tool_v2;
 use crate::turn_timing::now_unix_timestamp_ms;
 use codex_protocol::AgentPath;
+use codex_protocol::models::ResponseItemMetadata;
 use codex_protocol::protocol::Op;
 use codex_tools::ToolSpec;
 
@@ -117,8 +118,12 @@ async fn handle_spawn_agent(
                         .session_source
                         .get_agent_path()
                         .unwrap_or_else(AgentPath::root);
-                    let communication =
+                    let mut communication =
                         communication_from_tool_message(author, new_agent_path.clone(), message);
+                    communication
+                        .metadata
+                        .get_or_insert_with(ResponseItemMetadata::default)
+                        .source_call_id = Some(call_id.clone());
                     Op::InterAgentCommunication { communication }
                 }
                 initial_operation => initial_operation,

codex-rs/core/tests/suite/subagent_notifications.rs

@@ -1088,6 +1088,9 @@ async fn encrypted_multi_agent_v2_spawn_sends_agent_message_to_child() -> Result
             "type": "agent_message",
             "author": "/root",
             "recipient": "/root/worker",
+            "metadata": {
+                "source_call_id": SPAWN_CALL_ID,
+            },
             "content": [
                 {
                     "type": "input_text",

codex-rs/protocol/src/models.rs

@@ -909,6 +909,9 @@ pub struct ResponseItemMetadata {
     #[serde(default, skip_serializing_if = "Option::is_none")]
     #[ts(optional)]
     pub turn_id: Option<String>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    #[ts(optional)]
+    pub source_call_id: Option<String>,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, JsonSchema, TS)]
@@ -2072,6 +2075,7 @@ mod tests {
     fn response_item_metadata(turn_id: &str) -> ResponseItemMetadata {
         ResponseItemMetadata {
             turn_id: Some(turn_id.to_string()),
+            ..Default::default()
         }
     }