Use ConversationId instead of raw Uuids (#3282)

We're trying to migrate from `session_id: Uuid` to `conversation_id:
ConversationId`. Not only does this give us more type safety but it
unifies our terminology across Codex and with the implementation of
session resuming, a conversation (which can span multiple sessions) is
more appropriate.

I started this impl on https://github.com/openai/codex/pull/3219 as part
of getting resume working in the extension but it's big enough that it
should be broken out.

codex-rs/core/tests/chat_completions_payload.rs

@@ -11,11 +11,11 @@ use codex_core::ReasoningItemContent;
 use codex_core::ResponseItem;
 use codex_core::WireApi;
 use codex_core::spawn::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR;
+use codex_protocol::mcp_protocol::ConversationId;
 use core_test_support::load_default_config_for_test;
 use futures::StreamExt;
 use serde_json::Value;
 use tempfile::TempDir;
-use uuid::Uuid;
 use wiremock::Mock;
 use wiremock::MockServer;
 use wiremock::ResponseTemplate;
@@ -76,7 +76,7 @@ async fn run_request(input: Vec<ResponseItem>) -> Value {
         provider,
         effort,
         summary,
-        Uuid::new_v4(),
+        ConversationId::new(),
     );
 
     let mut prompt = Prompt::default();

codex-rs/core/tests/chat_completions_sse.rs

@@ -8,10 +8,10 @@ use codex_core::ResponseEvent;
 use codex_core::ResponseItem;
 use codex_core::WireApi;
 use codex_core::spawn::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR;
+use codex_protocol::mcp_protocol::ConversationId;
 use core_test_support::load_default_config_for_test;
 use futures::StreamExt;
 use tempfile::TempDir;
-use uuid::Uuid;
 use wiremock::Mock;
 use wiremock::MockServer;
 use wiremock::ResponseTemplate;
@@ -69,7 +69,7 @@ async fn run_stream(sse_body: &str) -> Vec<ResponseEvent> {
         provider,
         effort,
         summary,
-        Uuid::new_v4(),
+        ConversationId::new(),
     );
 
     let mut prompt = Prompt::default();

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

@@ -242,7 +242,7 @@ async fn resume_includes_initial_messages_and_sends_prior_items() {
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-async fn includes_session_id_and_model_headers_in_request() {
+async fn includes_conversation_id_and_model_headers_in_request() {
     if std::env::var(CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR).is_ok() {
         println!(
             "Skipping test because it cannot execute when network is disabled in a Codex sandbox."
@@ -299,12 +299,12 @@ async fn includes_session_id_and_model_headers_in_request() {
 
     // get request from the server
     let request = &server.received_requests().await.unwrap()[0];
-    let request_session_id = request.headers.get("session_id").unwrap();
+    let request_conversation_id = request.headers.get("conversation_id").unwrap();
     let request_authorization = request.headers.get("authorization").unwrap();
     let request_originator = request.headers.get("originator").unwrap();
 
     assert_eq!(
-        request_session_id.to_str().unwrap(),
+        request_conversation_id.to_str().unwrap(),
         conversation_id.to_string()
     );
     assert_eq!(request_originator.to_str().unwrap(), "codex_cli_rs");
@@ -477,14 +477,14 @@ async fn chatgpt_auth_sends_correct_request() {
 
     // get request from the server
     let request = &server.received_requests().await.unwrap()[0];
-    let request_session_id = request.headers.get("session_id").unwrap();
+    let request_conversation_id = request.headers.get("conversation_id").unwrap();
     let request_authorization = request.headers.get("authorization").unwrap();
     let request_originator = request.headers.get("originator").unwrap();
     let request_chatgpt_account_id = request.headers.get("chatgpt-account-id").unwrap();
     let request_body = request.body_json::<serde_json::Value>().unwrap();
 
     assert_eq!(
-        request_session_id.to_str().unwrap(),
+        request_conversation_id.to_str().unwrap(),
         conversation_id.to_string()
     );
     assert_eq!(request_originator.to_str().unwrap(), "codex_cli_rs");