diff --git a/run_agent.py b/run_agent.py
index 7d9d5a2c..155c6f8c 100644
--- a/run_agent.py
+++ b/run_agent.py
@@ -1596,6 +1596,11 @@ class AIAgent:
                     item_id = item.get("id")
                     if isinstance(item_id, str) and item_id:
                         reasoning_item["id"] = item_id
+                    summary = item.get("summary")
+                    if isinstance(summary, list):
+                        reasoning_item["summary"] = summary
+                    else:
+                        reasoning_item["summary"] = []
                     normalized.append(reasoning_item)
                 continue
 
@@ -1828,6 +1833,15 @@ class AIAgent:
                     item_id = getattr(item, "id", None)
                     if isinstance(item_id, str) and item_id:
                         raw_item["id"] = item_id
+                    # Capture summary — required by the API when replaying reasoning items
+                    summary = getattr(item, "summary", None)
+                    if isinstance(summary, list):
+                        raw_summary = []
+                        for part in summary:
+                            text = getattr(part, "text", None)
+                            if isinstance(text, str):
+                                raw_summary.append({"type": "summary_text", "text": text})
+                        raw_item["summary"] = raw_summary
                     reasoning_items_raw.append(raw_item)
             elif item_type == "function_call":
                 if item_status in {"queued", "in_progress", "incomplete"}:
diff --git a/tests/test_provider_parity.py b/tests/test_provider_parity.py
index 5b8508e6..00fc4dd9 100644
--- a/tests/test_provider_parity.py
+++ b/tests/test_provider_parity.py
@@ -539,7 +539,8 @@ class TestCodexReasoningPreflight:
                             base_url="https://chatgpt.com/backend-api/codex")
         raw_input = [
             {"role": "user", "content": "hello"},
-            {"type": "reasoning", "encrypted_content": "abc123encrypted", "id": "r_001"},
+            {"type": "reasoning", "encrypted_content": "abc123encrypted", "id": "r_001",
+             "summary": [{"type": "summary_text", "text": "Thinking about it"}]},
             {"role": "assistant", "content": "hi there"},
         ]
         normalized = agent._preflight_codex_input_items(raw_input)
@@ -547,6 +548,7 @@ class TestCodexReasoningPreflight:
         assert len(reasoning_items) == 1
         assert reasoning_items[0]["encrypted_content"] == "abc123encrypted"
         assert reasoning_items[0]["id"] == "r_001"
+        assert reasoning_items[0]["summary"] == [{"type": "summary_text", "text": "Thinking about it"}]
 
     def test_reasoning_item_without_id(self, monkeypatch):
         agent = _make_agent(monkeypatch, "openai-codex", api_mode="codex_responses",
@@ -557,6 +559,7 @@ class TestCodexReasoningPreflight:
         normalized = agent._preflight_codex_input_items(raw_input)
         assert len(normalized) == 1
         assert "id" not in normalized[0]
+        assert normalized[0]["summary"] == []  # default empty summary
 
     def test_reasoning_item_empty_encrypted_skipped(self, monkeypatch):
         agent = _make_agent(monkeypatch, "openai-codex", api_mode="codex_responses",