From 069bfd6545f618a1c5d3c617908ea82ad4556e8e Mon Sep 17 00:00:00 2001
From: Teknium <127238744+teknium1@users.noreply.github.com>
Date: Sat, 13 Jun 2026 14:08:11 -0700
Subject: [PATCH] fix(agent): keep Codex reasoning replay on Codex path

---
 agent/agent_runtime_helpers.py | 10 +++++++++-
 agent/conversation_loop.py     |  5 ++++-
 run_agent.py                   | 15 ++++++++++++---
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/agent/agent_runtime_helpers.py b/agent/agent_runtime_helpers.py
index ea71cb93946..cae1a685a53 100644
--- a/agent/agent_runtime_helpers.py
+++ b/agent/agent_runtime_helpers.py
@@ -881,6 +881,8 @@ def try_recover_primary_transport(
 
 def drop_thinking_only_and_merge_users(
     messages: List[Dict[str, Any]],
+    *,
+    drop_codex_reasoning_items: bool = True,
 ) -> List[Dict[str, Any]]:
     """Drop thinking-only assistant turns; merge any adjacent user messages left behind.
 
@@ -902,7 +904,13 @@ def drop_thinking_only_and_merge_users(
         return messages
 
     # Pass 1: drop thinking-only assistant turns.
-    kept = [m for m in messages if not _ra().AIAgent._is_thinking_only_assistant(m)]
+    kept = [
+        m for m in messages
+        if not _ra().AIAgent._is_thinking_only_assistant(
+            m,
+            drop_codex_reasoning_items=drop_codex_reasoning_items,
+        )
+    ]
     dropped = len(messages) - len(kept)
     if dropped == 0:
         return messages
diff --git a/agent/conversation_loop.py b/agent/conversation_loop.py
index 05d19772d9c..1d8384aa8a7 100644
--- a/agent/conversation_loop.py
+++ b/agent/conversation_loop.py
@@ -707,7 +707,10 @@ def run_conversation(
         # a thinking-only turn. Runs on the per-call copy only — the
         # stored conversation history keeps the reasoning block for the
         # UI transcript and session persistence.
-        api_messages = agent._drop_thinking_only_and_merge_users(api_messages)
+        api_messages = agent._drop_thinking_only_and_merge_users(
+            api_messages,
+            drop_codex_reasoning_items=agent.api_mode != "codex_responses",
+        )
 
         # Normalize message whitespace and tool-call JSON for consistent
         # prefix matching.  Ensures bit-perfect prefixes across turns,
diff --git a/run_agent.py b/run_agent.py
index b793f0e6b5d..ffcf2abf171 100644
--- a/run_agent.py
+++ b/run_agent.py
@@ -3246,7 +3246,11 @@ class AIAgent:
         return sanitize_api_messages(messages)
 
     @staticmethod
-    def _is_thinking_only_assistant(msg: Dict[str, Any]) -> bool:
+    def _is_thinking_only_assistant(
+        msg: Dict[str, Any],
+        *,
+        drop_codex_reasoning_items: bool = True,
+    ) -> bool:
         """Return True if ``msg`` is an assistant turn whose only payload is reasoning.
 
         "Thinking-only" means the model emitted reasoning (``reasoning`` or
@@ -3302,7 +3306,7 @@ class AIAgent:
         # thinking-only; empty/junk lists should fall through to the generic
         # empty-turn handling instead of being dropped here.
         codex_items = msg.get("codex_reasoning_items")
-        if isinstance(codex_items, list):
+        if drop_codex_reasoning_items and isinstance(codex_items, list):
             return any(
                 isinstance(item, dict) and item.get("type") == "reasoning"
                 for item in codex_items
@@ -3312,10 +3316,15 @@ class AIAgent:
     @staticmethod
     def _drop_thinking_only_and_merge_users(
         messages: List[Dict[str, Any]],
+        *,
+        drop_codex_reasoning_items: bool = True,
     ) -> List[Dict[str, Any]]:
         """Forwarder — see ``agent.agent_runtime_helpers.drop_thinking_only_and_merge_users``."""
         from agent.agent_runtime_helpers import drop_thinking_only_and_merge_users
-        return drop_thinking_only_and_merge_users(messages)
+        return drop_thinking_only_and_merge_users(
+            messages,
+            drop_codex_reasoning_items=drop_codex_reasoning_items,
+        )
 
     @staticmethod
     def _cap_delegate_task_calls(tool_calls: list) -> list: