feat: add post-compaction sub-agent infos

codex-rs/core/src/agent/control.rs

@@ -5,6 +5,7 @@ use crate::error::CodexErr;
 use crate::error::Result as CodexResult;
 use crate::find_thread_path_by_id_str;
 use crate::rollout::RolloutRecorder;
+use crate::session_prefix::format_subagent_context_line;
 use crate::session_prefix::format_subagent_notification_message;
 use crate::state_db;
 use crate::thread_manager::ThreadManagerState;
@@ -343,6 +344,40 @@ impl AgentControl {
         thread.total_token_usage().await
     }
 
+    pub(crate) async fn format_environment_context_subagents(
+        &self,
+        parent_thread_id: ThreadId,
+    ) -> String {
+        let Ok(state) = self.upgrade() else {
+            return String::new();
+        };
+
+        let mut agents = Vec::new();
+        for thread_id in state.list_thread_ids().await {
+            let Ok(thread) = state.get_thread(thread_id).await else {
+                continue;
+            };
+            let snapshot = thread.config_snapshot().await;
+            let SessionSource::SubAgent(SubAgentSource::ThreadSpawn {
+                parent_thread_id: agent_parent_thread_id,
+                agent_nickname,
+                ..
+            }) = snapshot.session_source
+            else {
+                continue;
+            };
+            if agent_parent_thread_id != parent_thread_id {
+                continue;
+            }
+            agents.push(format_subagent_context_line(
+                &thread_id.to_string(),
+                agent_nickname.as_deref(),
+            ));
+        }
+        agents.sort();
+        agents.join("\n")
+    }
+
     /// Starts a detached watcher for sub-agents spawned from another thread.
     ///
     /// This is only enabled for `SubAgentSource::ThreadSpawn`, where a parent thread exists and

codex-rs/core/src/codex.rs

@@ -3090,8 +3090,15 @@ impl Session {
                 .serialize_to_text(),
             );
         }
+        let subagents = self
+            .services
+            .agent_control
+            .format_environment_context_subagents(self.conversation_id)
+            .await;
         contextual_user_sections.push(
-            EnvironmentContext::from_turn_context(turn_context, shell.as_ref()).serialize_to_xml(),
+            EnvironmentContext::from_turn_context(turn_context, shell.as_ref())
+                .with_subagents(subagents)
+                .serialize_to_xml(),
         );
 
         let mut items = Vec::with_capacity(2);

codex-rs/core/src/compact_remote.rs

@@ -105,7 +105,6 @@ async fn run_remote_compact_task_inner_impl(
             "trimmed history items before remote compaction"
         );
     }
-
     // Required to keep `/undo` available after compaction
     let ghost_snapshots: Vec<ResponseItem> = history
         .raw_items()

codex-rs/core/src/environment_context.rs

@@ -14,6 +14,7 @@ pub(crate) struct EnvironmentContext {
     pub cwd: Option<PathBuf>,
     pub shell: Shell,
     pub network: Option<NetworkContext>,
+    pub subagents: Option<String>,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, Default)]
@@ -23,11 +24,17 @@ pub(crate) struct NetworkContext {
 }
 
 impl EnvironmentContext {
-    pub fn new(cwd: Option<PathBuf>, shell: Shell, network: Option<NetworkContext>) -> Self {
+    pub fn new(
+        cwd: Option<PathBuf>,
+        shell: Shell,
+        network: Option<NetworkContext>,
+        subagents: Option<String>,
+    ) -> Self {
         Self {
             cwd,
             shell,
             network,
+            subagents,
         }
     }
 
@@ -38,9 +45,10 @@ impl EnvironmentContext {
         let EnvironmentContext {
             cwd,
             network,
+            subagents,
             shell: _,
         } = other;
-        self.cwd == *cwd && self.network == *network
+        self.cwd == *cwd && self.network == *network && self.subagents == *subagents
     }
 
     pub fn diff_from_turn_context_item(
@@ -60,14 +68,15 @@ impl EnvironmentContext {
         } else {
             before_network
         };
-        EnvironmentContext::new(cwd, shell.clone(), network)
+        EnvironmentContext::new(cwd, shell.clone(), network, None)
     }
 
     pub fn from_turn_context(turn_context: &TurnContext, shell: &Shell) -> Self {
         Self::new(
             Some(turn_context.cwd.clone()),
             shell.clone(),
             Self::network_from_turn_context(turn_context),
+            None,
         )
     }
 
@@ -76,9 +85,17 @@ impl EnvironmentContext {
             Some(turn_context_item.cwd.clone()),
             shell.clone(),
             Self::network_from_turn_context_item(turn_context_item),
+            None,
         )
     }
 
+    pub fn with_subagents(mut self, subagents: String) -> Self {
+        if !subagents.is_empty() {
+            self.subagents = Some(subagents);
+        }
+        self
+    }
+
     fn network_from_turn_context(turn_context: &TurnContext) -> Option<NetworkContext> {
         let network = turn_context
             .config
@@ -142,6 +159,11 @@ impl EnvironmentContext {
                 // lines.push("  <network enabled=\"false\" />".to_string());
             }
         }
+        if let Some(subagents) = self.subagents {
+            lines.push("  <subagents>".to_string());
+            lines.extend(subagents.lines().map(|line| format!("    {line}")));
+            lines.push("  </subagents>".to_string());
+        }
         ENVIRONMENT_CONTEXT_FRAGMENT.wrap(lines.join("\n"))
     }
 }
@@ -171,7 +193,7 @@ mod tests {
     #[test]
     fn serialize_workspace_write_environment_context() {
         let cwd = test_path_buf("/repo");
-        let context = EnvironmentContext::new(Some(cwd.clone()), fake_shell(), None);
+        let context = EnvironmentContext::new(Some(cwd.clone()), fake_shell(), None, None);
 
         let expected = format!(
             r#"<environment_context>
@@ -190,8 +212,12 @@ mod tests {
             allowed_domains: vec!["api.example.com".to_string(), "*.openai.com".to_string()],
             denied_domains: vec!["blocked.example.com".to_string()],
         };
-        let context =
-            EnvironmentContext::new(Some(test_path_buf("/repo")), fake_shell(), Some(network));
+        let context = EnvironmentContext::new(
+            Some(test_path_buf("/repo")),
+            fake_shell(),
+            Some(network),
+            None,
+        );
 
         let expected = format!(
             r#"<environment_context>
@@ -211,7 +237,7 @@ mod tests {
 
     #[test]
     fn serialize_read_only_environment_context() {
-        let context = EnvironmentContext::new(None, fake_shell(), None);
+        let context = EnvironmentContext::new(None, fake_shell(), None, None);
 
         let expected = r#"<environment_context>
   <shell>bash</shell>
@@ -222,7 +248,7 @@ mod tests {
 
     #[test]
     fn serialize_external_sandbox_environment_context() {
-        let context = EnvironmentContext::new(None, fake_shell(), None);
+        let context = EnvironmentContext::new(None, fake_shell(), None, None);
 
         let expected = r#"<environment_context>
   <shell>bash</shell>
@@ -233,7 +259,7 @@ mod tests {
 
     #[test]
     fn serialize_external_sandbox_with_restricted_network_environment_context() {
-        let context = EnvironmentContext::new(None, fake_shell(), None);
+        let context = EnvironmentContext::new(None, fake_shell(), None, None);
 
         let expected = r#"<environment_context>
   <shell>bash</shell>
@@ -244,7 +270,7 @@ mod tests {
 
     #[test]
     fn serialize_full_access_environment_context() {
-        let context = EnvironmentContext::new(None, fake_shell(), None);
+        let context = EnvironmentContext::new(None, fake_shell(), None, None);
 
         let expected = r#"<environment_context>
   <shell>bash</shell>
@@ -255,23 +281,29 @@ mod tests {
 
     #[test]
     fn equals_except_shell_compares_cwd() {
-        let context1 = EnvironmentContext::new(Some(PathBuf::from("/repo")), fake_shell(), None);
-        let context2 = EnvironmentContext::new(Some(PathBuf::from("/repo")), fake_shell(), None);
+        let context1 =
+            EnvironmentContext::new(Some(PathBuf::from("/repo")), fake_shell(), None, None);
+        let context2 =
+            EnvironmentContext::new(Some(PathBuf::from("/repo")), fake_shell(), None, None);
         assert!(context1.equals_except_shell(&context2));
     }
 
     #[test]
     fn equals_except_shell_ignores_sandbox_policy() {
-        let context1 = EnvironmentContext::new(Some(PathBuf::from("/repo")), fake_shell(), None);
-        let context2 = EnvironmentContext::new(Some(PathBuf::from("/repo")), fake_shell(), None);
+        let context1 =
+            EnvironmentContext::new(Some(PathBuf::from("/repo")), fake_shell(), None, None);
+        let context2 =
+            EnvironmentContext::new(Some(PathBuf::from("/repo")), fake_shell(), None, None);
 
         assert!(context1.equals_except_shell(&context2));
     }
 
     #[test]
     fn equals_except_shell_compares_cwd_differences() {
-        let context1 = EnvironmentContext::new(Some(PathBuf::from("/repo1")), fake_shell(), None);
-        let context2 = EnvironmentContext::new(Some(PathBuf::from("/repo2")), fake_shell(), None);
+        let context1 =
+            EnvironmentContext::new(Some(PathBuf::from("/repo1")), fake_shell(), None, None);
+        let context2 =
+            EnvironmentContext::new(Some(PathBuf::from("/repo2")), fake_shell(), None, None);
 
         assert!(!context1.equals_except_shell(&context2));
     }
@@ -286,6 +318,7 @@ mod tests {
                 shell_snapshot: crate::shell::empty_shell_snapshot_receiver(),
             },
             None,
+            None,
         );
         let context2 = EnvironmentContext::new(
             Some(PathBuf::from("/repo")),
@@ -295,8 +328,33 @@ mod tests {
                 shell_snapshot: crate::shell::empty_shell_snapshot_receiver(),
             },
             None,
+            None,
         );
 
         assert!(context1.equals_except_shell(&context2));
     }
+
+    #[test]
+    fn serialize_environment_context_with_subagents() {
+        let context = EnvironmentContext::new(
+            Some(test_path_buf("/repo")),
+            fake_shell(),
+            None,
+            Some("- agent-1: atlas\n- agent-2".to_string()),
+        );
+
+        let expected = format!(
+            r#"<environment_context>
+  <cwd>{}</cwd>
+  <shell>bash</shell>
+  <subagents>
+    - agent-1: atlas
+    - agent-2
+  </subagents>
+</environment_context>"#,
+            test_path_buf("/repo").display()
+        );
+
+        assert_eq!(context.serialize_to_xml(), expected);
+    }
 }

codex-rs/core/src/session_prefix.rs

@@ -12,3 +12,10 @@ pub(crate) fn format_subagent_notification_message(agent_id: &str, status: &Agen
     .to_string();
     SUBAGENT_NOTIFICATION_FRAGMENT.wrap(payload_json)
 }
+
+pub(crate) fn format_subagent_context_line(agent_id: &str, agent_nickname: Option<&str>) -> String {
+    match agent_nickname.filter(|nickname| !nickname.is_empty()) {
+        Some(agent_nickname) => format!("- {agent_id}: {agent_nickname}"),
+        None => format!("- {agent_id}"),
+    }
+}

codex-rs/core/src/thread_manager.rs

@@ -252,7 +252,7 @@ impl ThreadManager {
     }
 
     pub async fn list_thread_ids(&self) -> Vec<ThreadId> {
-        self.state.threads.read().await.keys().copied().collect()
+        self.state.list_thread_ids().await
     }
 
     pub async fn refresh_mcp_servers(&self, refresh_config: McpServerRefreshConfig) {
@@ -412,6 +412,10 @@ impl ThreadManager {
 }
 
 impl ThreadManagerState {
+    pub(crate) async fn list_thread_ids(&self) -> Vec<ThreadId> {
+        self.threads.read().await.keys().copied().collect()
+    }
+
     /// Fetch a thread by ID or return ThreadNotFound.
     pub(crate) async fn get_thread(&self, thread_id: ThreadId) -> CodexResult<Arc<CodexThread>> {
         let threads = self.threads.read().await;

codex-rs/core/tests/common/context_snapshot.rs

@@ -238,15 +238,34 @@ fn canonicalize_snapshot_text(text: &str) -> String {
         return "<AGENTS_MD>".to_string();
     }
     if text.starts_with("<environment_context>") {
+        let subagent_count = text
+            .split_once("<subagents>")
+            .and_then(|(_, rest)| rest.split_once("</subagents>"))
+            .map(|(subagents, _)| {
+                subagents
+                    .lines()
+                    .filter(|line| line.trim_start().starts_with("- "))
+                    .count()
+            })
+            .unwrap_or(0);
+        let subagents_suffix = if subagent_count > 0 {
+            format!(":subagents={subagent_count}")
+        } else {
+            String::new()
+        };
         if let (Some(cwd_start), Some(cwd_end)) = (text.find("<cwd>"), text.find("</cwd>")) {
             let cwd = &text[cwd_start + "<cwd>".len()..cwd_end];
             return if cwd.ends_with("PRETURN_CONTEXT_DIFF_CWD") {
-                "<ENVIRONMENT_CONTEXT:cwd=PRETURN_CONTEXT_DIFF_CWD>".to_string()
+                format!("<ENVIRONMENT_CONTEXT:cwd=PRETURN_CONTEXT_DIFF_CWD{subagents_suffix}>")
             } else {
-                "<ENVIRONMENT_CONTEXT:cwd=<CWD>>".to_string()
+                format!("<ENVIRONMENT_CONTEXT:cwd=<CWD>{subagents_suffix}>")
             };
         }
-        return "<ENVIRONMENT_CONTEXT>".to_string();
+        return if subagent_count > 0 {
+            format!("<ENVIRONMENT_CONTEXT{subagents_suffix}>")
+        } else {
+            "<ENVIRONMENT_CONTEXT>".to_string()
+        };
     }
     if text.starts_with("You are performing a CONTEXT CHECKPOINT COMPACTION.") {
         return "<SUMMARIZATION_PROMPT>".to_string();
@@ -308,6 +327,28 @@ mod tests {
         assert_eq!(rendered, "00:message/user:<AGENTS_MD>");
     }
 
+    #[test]
+    fn redacted_text_mode_normalizes_environment_context_with_subagents() {
+        let items = vec![json!({
+            "type": "message",
+            "role": "user",
+            "content": [{
+                "type": "input_text",
+                "text": "<environment_context>\n  <cwd>/tmp/example</cwd>\n  <shell>bash</shell>\n  <subagents>\n    - agent-1: atlas\n    - agent-2\n  </subagents>\n</environment_context>"
+            }]
+        })];
+
+        let rendered = format_response_items_snapshot(
+            &items,
+            &ContextSnapshotOptions::default().render_mode(ContextSnapshotRenderMode::RedactedText),
+        );
+
+        assert_eq!(
+            rendered,
+            "00:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>:subagents=2>"
+        );
+    }
+
     #[test]
     fn image_only_message_is_rendered_as_non_text_span() {
         let items = vec![json!({