feat: introduce GetConversationSummary RPC

codex-rs/app-server/src/codex_message_processor.rs

@@ -21,6 +21,8 @@ use codex_app_server_protocol::ExecOneOffCommandResponse;
 use codex_app_server_protocol::FuzzyFileSearchParams;
 use codex_app_server_protocol::FuzzyFileSearchResponse;
 use codex_app_server_protocol::GetAccountRateLimitsResponse;
+use codex_app_server_protocol::GetConversationSummaryParams;
+use codex_app_server_protocol::GetConversationSummaryResponse;
 use codex_app_server_protocol::GetUserAgentResponse;
 use codex_app_server_protocol::GetUserSavedConfigResponse;
 use codex_app_server_protocol::GitDiffToRemoteResponse;
@@ -87,6 +89,7 @@ use codex_core::protocol::EventMsg;
 use codex_core::protocol::ExecApprovalRequestEvent;
 use codex_core::protocol::Op;
 use codex_core::protocol::ReviewDecision;
+use codex_core::read_head_for_summary;
 use codex_feedback::CodexFeedback;
 use codex_login::ServerOptions as LoginServerOptions;
 use codex_login::ShutdownHandle;
@@ -101,6 +104,8 @@ use codex_protocol::user_input::UserInput as CoreInputItem;
 use codex_utils_json_to_toml::json_to_toml;
 use std::collections::HashMap;
 use std::ffi::OsStr;
+use std::io::Error as IoError;
+use std::path::Path;
 use std::path::PathBuf;
 use std::sync::Arc;
 use std::sync::atomic::AtomicBool;
@@ -176,6 +181,9 @@ impl CodexMessageProcessor {
                 // created before processing any subsequent messages.
                 self.process_new_conversation(request_id, params).await;
             }
+            ClientRequest::GetConversationSummary { request_id, params } => {
+                self.get_conversation_summary(request_id, params).await;
+            }
             ClientRequest::ListConversations { request_id, params } => {
                 self.handle_list_conversations(request_id, params).await;
             }
@@ -822,6 +830,39 @@ impl CodexMessageProcessor {
         }
     }
 
+    async fn get_conversation_summary(
+        &self,
+        request_id: RequestId,
+        params: GetConversationSummaryParams,
+    ) {
+        let GetConversationSummaryParams { rollout_path } = params;
+        let path = if rollout_path.is_relative() {
+            self.config.codex_home.join(&rollout_path)
+        } else {
+            rollout_path.clone()
+        };
+        let fallback_provider = self.config.model_provider_id.as_str();
+
+        match read_summary_from_rollout(&path, fallback_provider).await {
+            Ok(summary) => {
+                let response = GetConversationSummaryResponse { summary };
+                self.outgoing.send_response(request_id, response).await;
+            }
+            Err(err) => {
+                let error = JSONRPCErrorError {
+                    code: INTERNAL_ERROR_CODE,
+                    message: format!(
+                        "failed to load conversation summary from {}: {}",
+                        path.display(),
+                        err
+                    ),
+                    data: None,
+                };
+                self.outgoing.send_error(request_id, error).await;
+            }
+        }
+    }
+
     async fn handle_list_conversations(
         &self,
         request_id: RequestId,
@@ -1724,6 +1765,50 @@ async fn on_exec_approval_response(
     }
 }
 
+async fn read_summary_from_rollout(
+    path: &Path,
+    fallback_provider: &str,
+) -> std::io::Result<ConversationSummary> {
+    let head = read_head_for_summary(path).await?;
+
+    let Some(first) = head.first() else {
+        return Err(IoError::other(format!(
+            "rollout at {} is empty",
+            path.display()
+        )));
+    };
+
+    let session_meta = serde_json::from_value::<SessionMeta>(first.clone()).map_err(|_| {
+        IoError::other(format!(
+            "rollout at {} does not start with session metadata",
+            path.display()
+        ))
+    })?;
+
+    if let Some(summary) =
+        extract_conversation_summary(path.to_path_buf(), &head, fallback_provider)
+    {
+        return Ok(summary);
+    }
+
+    let timestamp = if session_meta.timestamp.is_empty() {
+        None
+    } else {
+        Some(session_meta.timestamp.clone())
+    };
+    let model_provider = session_meta
+        .model_provider
+        .unwrap_or_else(|| fallback_provider.to_string());
+
+    Ok(ConversationSummary {
+        conversation_id: session_meta.id,
+        timestamp,
+        path: path.to_path_buf(),
+        preview: String::new(),
+        model_provider,
+    })
+}
+
 fn extract_conversation_summary(
     path: PathBuf,
     head: &[serde_json::Value],
@@ -1772,6 +1857,7 @@ mod tests {
     use anyhow::Result;
     use pretty_assertions::assert_eq;
     use serde_json::json;
+    use tempfile::TempDir;
 
     #[test]
     fn extract_conversation_summary_prefers_plain_user_messages() -> Result<()> {
@@ -1810,14 +1896,59 @@ mod tests {
         let summary =
             extract_conversation_summary(path.clone(), &head, "test-provider").expect("summary");
 
-        assert_eq!(summary.conversation_id, conversation_id);
-        assert_eq!(
-            summary.timestamp,
-            Some("2025-09-05T16:53:11.850Z".to_string())
-        );
-        assert_eq!(summary.path, path);
-        assert_eq!(summary.preview, "Count to 5");
-        assert_eq!(summary.model_provider, "test-provider");
+        let expected = ConversationSummary {
+            conversation_id,
+            timestamp,
+            path,
+            preview: "Count to 5".to_string(),
+            model_provider: "test-provider".to_string(),
+        };
+
+        assert_eq!(summary, expected);
+        Ok(())
+    }
+
+    #[tokio::test]
+    async fn read_summary_from_rollout_returns_empty_preview_when_no_user_message() -> Result<()> {
+        use codex_protocol::protocol::RolloutItem;
+        use codex_protocol::protocol::RolloutLine;
+        use codex_protocol::protocol::SessionMetaLine;
+        use std::fs;
+
+        let temp_dir = TempDir::new()?;
+        let path = temp_dir.path().join("rollout.jsonl");
+
+        let conversation_id = ConversationId::from_string("bfd12a78-5900-467b-9bc5-d3d35df08191")?;
+        let timestamp = "2025-09-05T16:53:11.850Z".to_string();
+
+        let session_meta = SessionMeta {
+            id: conversation_id,
+            timestamp: timestamp.clone(),
+            model_provider: None,
+            ..SessionMeta::default()
+        };
+
+        let line = RolloutLine {
+            timestamp: timestamp.clone(),
+            item: RolloutItem::SessionMeta(SessionMetaLine {
+                meta: session_meta.clone(),
+                git: None,
+            }),
+        };
+
+        fs::write(&path, format!("{}\n", serde_json::to_string(&line)?))?;
+
+        let summary = read_summary_from_rollout(path.as_path(), "fallback").await?;
+
+        let expected = ConversationSummary {
+            conversation_id,
+            timestamp: Some(timestamp),
+            path: path.clone(),
+            preview: String::new(),
+            model_provider: "fallback".to_string(),
+        };
+
+        assert_eq!(summary, expected);
         Ok(())
     }
 }