From 4d39a603d197a6ad2da483430446b96a1a9b0aea Mon Sep 17 00:00:00 2001
From: kyssta-exe <kyssta-exe@users.noreply.github.com>
Date: Tue, 16 Jun 2026 18:32:27 +0000
Subject: [PATCH] fix(codex): restore session_id/x-client-request-id HTTP
 headers for cache routing (#47335)

---
 agent/transports/codex.py                     | 26 ++++++++++++++++---
 .../agent/transports/test_codex_transport.py  | 25 +++++++++++++++---
 2 files changed, 44 insertions(+), 7 deletions(-)

diff --git a/agent/transports/codex.py b/agent/transports/codex.py
index 1d24ac3355a7..eaf6160ae1d3 100644
--- a/agent/transports/codex.py
+++ b/agent/transports/codex.py
@@ -218,10 +218,28 @@ class ResponsesApiTransport(ProviderTransport):
             kwargs.pop("timeout", None)
 
         if is_codex_backend:
-            # chatgpt.com/backend-api/codex rejects body-level
-            # ``extra_headers`` with HTTP 400. Correlation/cache routing for
-            # this backend must not be sent through the Responses payload.
-            kwargs.pop("extra_headers", None)
+            # The Codex backend rejects body-level ``extra_headers`` with
+            # HTTP 400, but the OpenAI SDK's ``extra_headers`` kwarg maps
+            # to actual HTTP request headers (not body fields).  We need
+            # these headers for cache-scope routing so prompt cache hits
+            # remain high.  Send session_id / x-client-request-id as HTTP
+            # headers while keeping ``prompt_cache_key`` in the body for
+            # standard OpenAI routing as a belt-and-braces fallback.
+            cache_scope_id = str(session_id or "").strip()
+            if cache_scope_id:
+                existing_extra_headers = kwargs.get("extra_headers")
+                merged_extra_headers: Dict[str, str] = {}
+                if isinstance(existing_extra_headers, dict):
+                    merged_extra_headers.update(
+                        {
+                            str(key): str(value)
+                            for key, value in existing_extra_headers.items()
+                            if key and value is not None
+                        }
+                    )
+                merged_extra_headers["session_id"] = cache_scope_id
+                merged_extra_headers["x-client-request-id"] = cache_scope_id
+                kwargs["extra_headers"] = merged_extra_headers
 
         max_tokens = params.get("max_tokens")
         if max_tokens is not None and not is_codex_backend:
diff --git a/tests/agent/transports/test_codex_transport.py b/tests/agent/transports/test_codex_transport.py
index e028f4344462..9355a7869649 100644
--- a/tests/agent/transports/test_codex_transport.py
+++ b/tests/agent/transports/test_codex_transport.py
@@ -155,7 +155,9 @@ class TestCodexBuildKwargs:
         )
         assert "max_output_tokens" not in kw
 
-    def test_codex_backend_does_not_set_extra_headers(self, transport):
+    def test_codex_backend_sets_cache_routing_headers(self, transport):
+        """Codex backend sends session_id / x-client-request-id as HTTP
+        headers (via extra_headers) for cache-scope routing."""
         messages = [{"role": "user", "content": "Hi"}]
 
         kw = transport.build_kwargs(
@@ -166,9 +168,23 @@ class TestCodexBuildKwargs:
             is_codex_backend=True,
         )
 
+        headers = kw.get("extra_headers", {})
+        assert headers.get("session_id") == "conv-codex-1"
+        assert headers.get("x-client-request-id") == "conv-codex-1"
+
+    def test_codex_backend_no_headers_without_session_id(self, transport):
+        messages = [{"role": "user", "content": "Hi"}]
+
+        kw = transport.build_kwargs(
+            model="gpt-5.4",
+            messages=messages,
+            tools=[],
+            is_codex_backend=True,
+        )
+
         assert "extra_headers" not in kw
 
-    def test_codex_backend_strips_caller_extra_headers(self, transport):
+    def test_codex_backend_preserves_caller_extra_headers(self, transport):
         messages = [{"role": "user", "content": "Hi"}]
 
         kw = transport.build_kwargs(
@@ -180,7 +196,10 @@ class TestCodexBuildKwargs:
             request_overrides={"extra_headers": {"x-test": "1"}},
         )
 
-        assert "extra_headers" not in kw
+        headers = kw.get("extra_headers", {})
+        assert headers.get("x-test") == "1"
+        assert headers.get("session_id") == "conv-codex-1"
+        assert headers.get("x-client-request-id") == "conv-codex-1"
 
     def test_non_codex_responses_preserves_caller_extra_headers(self, transport):
         messages = [{"role": "user", "content": "Hi"}]