diff --git a/agent/context_compressor.py b/agent/context_compressor.py
index edbc89b7..c91c0c15 100644
--- a/agent/context_compressor.py
+++ b/agent/context_compressor.py
@@ -992,8 +992,8 @@ The user has requested that this compaction PRIORITISE preserving all informatio
     def _get_tool_call_id(tc) -> str:
         """Extract the call ID from a tool_call entry (dict or SimpleNamespace)."""
         if isinstance(tc, dict):
-            return tc.get("id", "")
-        return getattr(tc, "id", "") or ""
+            return tc.get("call_id", "") or tc.get("id", "") or ""
+        return getattr(tc, "call_id", "") or getattr(tc, "id", "") or ""
 
     def _sanitize_tool_pairs(self, messages: List[Dict[str, Any]]) -> List[Dict[str, Any]]:
         """Fix orphaned tool_call / tool_result pairs after compression.
diff --git a/run_agent.py b/run_agent.py
index f09568c2..2645a14a 100644
--- a/run_agent.py
+++ b/run_agent.py
@@ -4982,8 +4982,8 @@ class AIAgent:
     def _get_tool_call_id_static(tc) -> str:
         """Extract call ID from a tool_call entry (dict or object)."""
         if isinstance(tc, dict):
-            return tc.get("id", "") or ""
-        return getattr(tc, "id", "") or ""
+            return tc.get("call_id", "") or tc.get("id", "") or ""
+        return getattr(tc, "call_id", "") or getattr(tc, "id", "") or ""
 
     _VALID_API_ROLES = frozenset({"system", "user", "assistant", "tool", "function", "developer"})
 
@@ -10013,6 +10013,13 @@ class AIAgent:
                 for idx, pfm in enumerate(self.prefill_messages):
                     api_messages.insert(sys_offset + idx, pfm.copy())
 
+            # Same safety net as the main loop: repair tool-call/result
+            # pairing before asking for a final summary.  Compression and
+            # session resume can leave a tool result whose parent assistant
+            # tool_call was summarized away; Responses API rejects that as
+            # "No tool call found for function call output".
+            api_messages = self._sanitize_api_messages(api_messages)
+
             # Same safety net as the main loop: drop thinking-only assistant
             # turns so Anthropic-family providers don't 400 the summary call.
             api_messages = self._drop_thinking_only_and_merge_users(api_messages)
diff --git a/tests/agent/test_context_compressor.py b/tests/agent/test_context_compressor.py
index 5225fa6e..8f5d6c4d 100644
--- a/tests/agent/test_context_compressor.py
+++ b/tests/agent/test_context_compressor.py
@@ -640,6 +640,30 @@ class TestCompressWithClient:
                 for tc in msg["tool_calls"]:
                     assert tc["id"] in answered_ids
 
+    def test_sanitizer_matches_responses_call_id_when_id_differs(self, compressor):
+        msgs = [
+            {
+                "role": "assistant",
+                "content": "",
+                "tool_calls": [
+                    {
+                        "id": "fc_123",
+                        "call_id": "call_123",
+                        "response_item_id": "fc_123",
+                        "type": "function",
+                        "function": {"name": "search_files", "arguments": "{}"},
+                    }
+                ],
+            },
+            {"role": "tool", "tool_call_id": "call_123", "content": "result"},
+        ]
+
+        sanitized = compressor._sanitize_tool_pairs(msgs)
+
+        assert [m.get("tool_call_id") for m in sanitized if m.get("role") == "tool"] == [
+            "call_123"
+        ]
+
     def test_summary_role_avoids_consecutive_user_messages(self):
         """Summary role should alternate with the last head message to avoid consecutive same-role messages."""
         mock_client = MagicMock()
diff --git a/tests/run_agent/test_run_agent.py b/tests/run_agent/test_run_agent.py
index 5585eea4..03cef830 100644
--- a/tests/run_agent/test_run_agent.py
+++ b/tests/run_agent/test_run_agent.py
@@ -2181,6 +2181,73 @@ class TestHandleMaxIterations:
         kwargs = agent.client.chat.completions.create.call_args.kwargs
         assert "reasoning" not in kwargs.get("extra_body", {})
 
+    def test_codex_summary_sanitizes_orphan_tool_results(self, agent):
+        agent.api_mode = "codex_responses"
+        agent.provider = "openai-codex"
+        agent.base_url = "https://chatgpt.com/backend-api/codex"
+        agent._base_url_lower = agent.base_url.lower()
+        agent._base_url_hostname = "chatgpt.com"
+        agent.model = "gpt-5.5"
+        agent._cached_system_prompt = "You are helpful."
+        captured = {}
+
+        def fake_run_codex_stream(kwargs):
+            captured.update(kwargs)
+            return SimpleNamespace(
+                status="completed",
+                output=[
+                    SimpleNamespace(
+                        type="message",
+                        status="completed",
+                        content=[SimpleNamespace(type="output_text", text="Summary")],
+                    )
+                ],
+            )
+
+        messages = [
+            {"role": "user", "content": "do stuff"},
+            {
+                "role": "tool",
+                "tool_call_id": "call_orphan",
+                "content": "orphaned result from compressed history",
+            },
+        ]
+
+        with patch.object(agent, "_run_codex_stream", side_effect=fake_run_codex_stream):
+            result = agent._handle_max_iterations(messages, 90)
+
+        assert result == "Summary"
+        input_items = captured["input"]
+        assert not any(
+            item.get("type") == "function_call_output"
+            and item.get("call_id") == "call_orphan"
+            for item in input_items
+        )
+
+    def test_api_sanitizer_matches_responses_call_id_when_id_differs(self, agent):
+        messages = [
+            {
+                "role": "assistant",
+                "content": "",
+                "tool_calls": [
+                    {
+                        "id": "fc_123",
+                        "call_id": "call_123",
+                        "response_item_id": "fc_123",
+                        "type": "function",
+                        "function": {"name": "web_search", "arguments": "{}"},
+                    }
+                ],
+            },
+            {"role": "tool", "tool_call_id": "call_123", "content": "result"},
+        ]
+
+        sanitized = agent._sanitize_api_messages(messages)
+
+        assert [m.get("tool_call_id") for m in sanitized if m.get("role") == "tool"] == [
+            "call_123"
+        ]
+
 
 class TestRunConversation:
     """Tests for the main run_conversation method.