From eec3b1e235ff59582acd1bb37fe3ad7df2adbe3b Mon Sep 17 00:00:00 2001
From: daveaitel-openai <daveaitel@openai.com>
Date: Sat, 28 Feb 2026 08:54:08 -0500
Subject: [PATCH] Speed up subagent startup (#12935)

## Summary
- skip online model refresh for subagent sessions
- avoid rollout flushes during subagent startup
- keep /models refresh for non-subagent sessions

## Testing
- cargo test -p codex-core --test all
suite::models_etag_responses::refresh_models_on_models_etag_mismatch_and_avoid_duplicate_models_fetch
- cargo test -p codex-core --test all
suite::remote_models::remote_models_long_model_slug_is_sent_with_high_reasoning
- cargo test -p codex-core --test all
suite::model_switching::model_switch_to_smaller_model_updates_token_context_window
- cargo test -p codex-core --test all
suite::compact::pre_sampling_compact_runs_on_switch_to_smaller_context_model
- cargo test -p codex-core --test all
suite::compact::pre_sampling_compact_runs_after_resume_and_switch_to_smaller_model
- cargo test -p codex-core --test all
suite::personality::remote_model_friendly_personality_instructions_with_feature

---------

Co-authored-by: Codex <noreply@openai.com>
---
 codex-rs/core/src/codex.rs | 39 ++++++++++++++++++++++++++++----------
 1 file changed, 29 insertions(+), 10 deletions(-)

diff --git a/codex-rs/core/src/codex.rs b/codex-rs/core/src/codex.rs
index 38dde09a0..deb8b3603 100644
--- a/codex-rs/core/src/codex.rs
+++ b/codex-rs/core/src/codex.rs
@@ -371,14 +371,20 @@ impl Codex {
             .map_err(|err| CodexErr::Fatal(format!("failed to load rules: {err}")))?;
 
         let config = Arc::new(config);
-        let _ = models_manager
-            .list_models(crate::models_manager::manager::RefreshStrategy::OnlineIfUncached)
-            .await;
-        let model = models_manager
-            .get_default_model(
-                &config.model,
-                crate::models_manager::manager::RefreshStrategy::OnlineIfUncached,
+        let refresh_strategy = match session_source {
+            SessionSource::SubAgent(_) => crate::models_manager::manager::RefreshStrategy::Offline,
+            _ => crate::models_manager::manager::RefreshStrategy::OnlineIfUncached,
+        };
+        if config.model.is_none()
+            || !matches!(
+                refresh_strategy,
+                crate::models_manager::manager::RefreshStrategy::Offline
             )
+        {
+            let _ = models_manager.list_models(refresh_strategy).await;
+        }
+        let model = models_manager
+            .get_default_model(&config.model, refresh_strategy)
             .await;
 
         // Resolve base instructions for the session. Priority order:
@@ -1727,6 +1733,13 @@ impl Session {
     async fn record_initial_history(&self, conversation_history: InitialHistory) {
         let turn_context = self.new_default_turn().await;
         self.clear_mcp_tool_selection().await;
+        let is_subagent = {
+            let state = self.state.lock().await;
+            matches!(
+                state.session_configuration.session_source,
+                SessionSource::SubAgent(_)
+            )
+        };
         match conversation_history {
             InitialHistory::New => {
                 // Build and record initial items (user instructions + environment context)
@@ -1741,7 +1754,9 @@ impl Session {
                 }
                 self.set_previous_model(None).await;
                 // Ensure initial items are visible to immediate readers (e.g., tests, forks).
-                self.flush_rollout().await;
+                if !is_subagent {
+                    self.flush_rollout().await;
+                }
             }
             InitialHistory::Resumed(resumed_history) => {
                 let rollout_items = resumed_history.history;
@@ -1792,7 +1807,9 @@ impl Session {
 
                 // Defer seeding the session's initial context until the first turn starts so
                 // turn/start overrides can be merged before we write to the rollout.
-                self.flush_rollout().await;
+                if !is_subagent {
+                    self.flush_rollout().await;
+                }
             }
             InitialHistory::Forked(rollout_items) => {
                 let restored_tool_selection =
@@ -1838,7 +1855,9 @@ impl Session {
                 self.ensure_rollout_materialized().await;
 
                 // Flush after seeding history and any persisted rollout copy.
-                self.flush_rollout().await;
+                if !is_subagent {
+                    self.flush_rollout().await;
+                }
             }
         }
     }