feat: add nick name to sub-agents (#12320)

Adding random nick name to sub-agents. Used for UX

At the same time, also storing and wiring the role of the sub-agent

codex-rs/protocol/src/protocol.rs

@@ -1861,6 +1861,10 @@ pub enum SubAgentSource {
     ThreadSpawn {
         parent_thread_id: ThreadId,
         depth: i32,
+        #[serde(default)]
+        agent_nickname: Option<String>,
+        #[serde(default, alias = "agent_type")]
+        agent_role: Option<String>,
     },
     MemoryConsolidation,
     Other(String),
@@ -1879,6 +1883,26 @@ impl fmt::Display for SessionSource {
     }
 }
 
+impl SessionSource {
+    pub fn get_nickname(&self) -> Option<String> {
+        match self {
+            SessionSource::SubAgent(SubAgentSource::ThreadSpawn { agent_nickname, .. }) => {
+                agent_nickname.clone()
+            }
+            _ => None,
+        }
+    }
+
+    pub fn get_agent_role(&self) -> Option<String> {
+        match self {
+            SessionSource::SubAgent(SubAgentSource::ThreadSpawn { agent_role, .. }) => {
+                agent_role.clone()
+            }
+            _ => None,
+        }
+    }
+}
+
 impl fmt::Display for SubAgentSource {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
@@ -1888,6 +1912,7 @@ impl fmt::Display for SubAgentSource {
             SubAgentSource::ThreadSpawn {
                 parent_thread_id,
                 depth,
+                ..
             } => {
                 write!(f, "thread_spawn_{parent_thread_id}_d{depth}")
             }
@@ -1912,6 +1937,12 @@ pub struct SessionMeta {
     pub cli_version: String,
     #[serde(default)]
     pub source: SessionSource,
+    /// Optional random unique nickname assigned to an AgentControl-spawned sub-agent.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub agent_nickname: Option<String>,
+    /// Optional role (agent_role) assigned to an AgentControl-spawned sub-agent.
+    #[serde(default, alias = "agent_type", skip_serializing_if = "Option::is_none")]
+    pub agent_role: Option<String>,
     pub model_provider: Option<String>,
     /// base_instructions for the session. This *should* always be present when creating a new session,
     /// but may be missing for older sessions. If not present, fall back to rendering the base_instructions
@@ -1931,6 +1962,8 @@ impl Default for SessionMeta {
             originator: String::new(),
             cli_version: String::new(),
             source: SessionSource::default(),
+            agent_nickname: None,
+            agent_role: None,
             model_provider: None,
             base_instructions: None,
             dynamic_tools: None,