feat: add root thread id

codex-rs/codex-api/README.md

@@ -14,7 +14,7 @@ The public interface of this crate is intentionally small and uniform:
 - **Responses endpoint**
   - Input:
     - `ResponsesApiRequest` for the request body (`model`, `instructions`, `input`, `tools`, `parallel_tool_calls`, reasoning/text controls).
-    - `ResponsesOptions` for transport/header concerns (`conversation_id`, `session_source`, `extra_headers`, `compression`, `turn_state`).
+    - `ResponsesOptions` for transport/header concerns (`session_id`, `thread_id`, `session_source`, `extra_headers`, `compression`, `turn_state`).
   - Output: a `ResponseStream` of `ResponseEvent` (both re-exported from `common`).
 
 - **Compaction endpoint**

codex-rs/codex-api/src/endpoint/responses.rs

@@ -6,7 +6,7 @@ use crate::error::ApiError;
 use crate::provider::Provider;
 use crate::requests::Compression;
 use crate::requests::attach_item_ids;
-use crate::requests::headers::build_conversation_headers;
+use crate::requests::headers::build_session_headers;
 use crate::requests::headers::insert_header;
 use crate::requests::headers::subagent_header;
 use crate::sse::spawn_response_stream;
@@ -30,7 +30,8 @@ pub struct ResponsesClient<T: HttpTransport> {
 
 #[derive(Default)]
 pub struct ResponsesOptions {
-    pub conversation_id: Option<String>,
+    pub session_id: Option<String>,
+    pub thread_id: Option<String>,
     pub session_source: Option<SessionSource>,
     pub extra_headers: HeaderMap,
     pub compression: Compression,
@@ -72,7 +73,8 @@ impl<T: HttpTransport> ResponsesClient<T> {
         options: ResponsesOptions,
     ) -> Result<ResponseStream, ApiError> {
         let ResponsesOptions {
-            conversation_id,
+            session_id,
+            thread_id,
             session_source,
             extra_headers,
             compression,
@@ -86,10 +88,10 @@ impl<T: HttpTransport> ResponsesClient<T> {
         }
 
         let mut headers = extra_headers;
-        if let Some(ref conv_id) = conversation_id {
-            insert_header(&mut headers, "x-client-request-id", conv_id);
+        if let Some(ref thread_id) = thread_id {
+            insert_header(&mut headers, "x-client-request-id", thread_id);
         }
-        headers.extend(build_conversation_headers(conversation_id));
+        headers.extend(build_session_headers(session_id, thread_id));
         if let Some(subagent) = subagent_header(&session_source) {
             insert_header(&mut headers, "x-openai-subagent", &subagent);
         }

codex-rs/codex-api/src/lib.rs

@@ -10,7 +10,7 @@ pub(crate) mod requests;
 pub(crate) mod sse;
 pub(crate) mod telemetry;
 
-pub use crate::requests::headers::build_conversation_headers;
+pub use crate::requests::headers::build_session_headers;
 pub use codex_client::RequestTelemetry;
 pub use codex_client::ReqwestTransport;
 pub use codex_client::TransportError;

codex-rs/codex-api/src/requests/headers.rs

@@ -2,11 +2,14 @@ use codex_protocol::protocol::SessionSource;
 use http::HeaderMap;
 use http::HeaderValue;
 
-pub fn build_conversation_headers(conversation_id: Option<String>) -> HeaderMap {
+pub fn build_session_headers(session_id: Option<String>, thread_id: Option<String>) -> HeaderMap {
     let mut headers = HeaderMap::new();
-    if let Some(id) = conversation_id {
+    if let Some(id) = session_id {
         insert_header(&mut headers, "session_id", &id);
     }
+    if let Some(id) = thread_id {
+        insert_header(&mut headers, "thread_id", &id);
+    }
     headers
 }
 

codex-rs/codex-api/tests/clients.rs

@@ -445,7 +445,8 @@ async fn azure_default_store_attaches_ids_and_headers() -> Result<()> {
         .stream_request(
             request,
             ResponsesOptions {
-                conversation_id: Some("sess_123".into()),
+                session_id: Some("sess_123".into()),
+                thread_id: Some("thread_456".into()),
                 session_source: Some(SessionSource::SubAgent(SubAgentSource::Review)),
                 extra_headers,
                 compression: Compression::None,
@@ -462,6 +463,10 @@ async fn azure_default_store_attaches_ids_and_headers() -> Result<()> {
         req.headers.get("session_id").and_then(|v| v.to_str().ok()),
         Some("sess_123")
     );
+    assert_eq!(
+        req.headers.get("thread_id").and_then(|v| v.to_str().ok()),
+        Some("thread_456")
+    );
     assert_eq!(
         req.headers
             .get("x-openai-subagent")