diff --git a/plugins/_oauth/helpers/codex.py b/plugins/_oauth/helpers/codex.py
index ad32cd271..824e19a92 100644
--- a/plugins/_oauth/helpers/codex.py
+++ b/plugins/_oauth/helpers/codex.py
@@ -35,7 +35,7 @@ except ImportError:
 AUTH_FILENAME = "auth.json"
 ACCESS_EXPIRY_MARGIN = timedelta(minutes=5)
 REFRESH_INTERVAL = timedelta(minutes=55)
-FALLBACK_CODEX_VERSION = "0.124.0"
+DEFAULT_CODEX_MODEL = "gpt-5.5"
 OAUTH_ERROR_KEYS = ("error_description", "error")
 DEVICE_CODE_TIMEOUT_SECONDS = 15 * 60
 WINDOWS_LOCK_RETRY_SECONDS = 0.05
@@ -590,9 +590,11 @@ def fetch_models() -> list[str]:
     if configured:
         return configured
 
+    client_version = resolve_codex_version()
+    params = {"client_version": client_version} if client_version else None
     response = request_codex(
         "/models",
-        params={"client_version": resolve_codex_version()},
+        params=params,
     )
     if not response.ok:
         raise RuntimeError(upstream_error_message(response, "Failed to load Codex models."))
@@ -772,7 +774,7 @@ def chat_messages_to_response_body(body: dict[str, Any]) -> dict[str, Any]:
         )
 
     response_body: dict[str, Any] = {
-        "model": body.get("model") or "gpt-5.2",
+        "model": body.get("model") or DEFAULT_CODEX_MODEL,
         "input": response_input,
         "instructions": "\n\n".join(instructions),
         "store": False,
@@ -980,7 +982,7 @@ def resolve_codex_version() -> str:
             return version
     except Exception:
         pass
-    return FALLBACK_CODEX_VERSION
+    return ""
 
 
 def resolve_auth_file_candidates() -> list[Path]:
diff --git a/plugins/_oauth/helpers/providers/codex.py b/plugins/_oauth/helpers/providers/codex.py
index 7a2eb7218..d619927da 100644
--- a/plugins/_oauth/helpers/providers/codex.py
+++ b/plugins/_oauth/helpers/providers/codex.py
@@ -20,7 +20,7 @@ from plugins._oauth.helpers.state import (
 )
 
 
-CODEX_DEFAULT_MODELS = ["gpt-5.2-codex", "gpt-5.2"]
+CODEX_DEFAULT_MODEL = "gpt-5.5"
 CODEX_FALLBACK_CONFIG = {
     "enabled": True,
     "models": [],
@@ -35,7 +35,7 @@ class CodexOAuthProvider:
 
     def metadata(self) -> OAuthProviderMetadata:
         cfg = _codex_config()
-        models = cfg["models"] or CODEX_DEFAULT_MODELS
+        models = list(cfg["models"])
         return OAuthProviderMetadata(
             provider_id=CODEX_PROVIDER_ID,
             display_name="Codex/ChatGPT",
@@ -43,7 +43,7 @@ class CodexOAuthProvider:
             model_provider_id=CODEX_PROVIDER_ID,
             icon="openai",
             auth_flow="device_code",
-            default_model=models[0] if models else "gpt-5.2-codex",
+            default_model=models[0] if models else CODEX_DEFAULT_MODEL,
             default_models=models,
             proxy_base_path=cfg["proxy_base_path"],
             callback_path=cfg["callback_path"],
diff --git a/plugins/_oauth/helpers/providers/github_copilot.py b/plugins/_oauth/helpers/providers/github_copilot.py
index 2adbc411f..bf60db627 100644
--- a/plugins/_oauth/helpers/providers/github_copilot.py
+++ b/plugins/_oauth/helpers/providers/github_copilot.py
@@ -35,7 +35,6 @@ COPILOT_HEADERS = {
     "Copilot-Integration-Id": "vscode-chat",
 }
 CURATED_MODELS = [
-    "gpt-5.2-codex",
     "gpt-5.2",
     "claude-sonnet-4.5",
     "claude-opus-4.5",
@@ -203,7 +202,7 @@ class GitHubCopilotOAuthProvider:
             model_provider_id=GITHUB_COPILOT_PROVIDER_ID,
             icon="github",
             auth_flow="device_code",
-            default_model="gpt-5.2-codex",
+            default_model=CURATED_MODELS[0],
             default_models=list(CURATED_MODELS),
             proxy_base_path="/oauth/github-copilot",
             supports_enterprise_domain=True,
diff --git a/tests/test_oauth_codex.py b/tests/test_oauth_codex.py
index 4a2fb31e6..89c0a6e17 100644
--- a/tests/test_oauth_codex.py
+++ b/tests/test_oauth_codex.py
@@ -15,6 +15,7 @@ import yaml
 sys.path.insert(0, str(Path(__file__).resolve().parents[1]))
 from plugins._oauth.helpers import codex
 from plugins._oauth.helpers import routes
+from plugins._oauth.helpers.providers import codex as codex_provider
 from plugins._oauth.extensions.python._functions.models.get_api_key.end import (
     _20_oauth_account_dummy_key as oauth_dummy_key,
 )
@@ -90,6 +91,52 @@ def test_chat_messages_to_response_body_extracts_instructions():
     assert body["reasoning"] == {"effort": "high"}
 
 
+def test_chat_messages_to_response_body_uses_current_codex_default_model():
+    body = codex.chat_messages_to_response_body(
+        {
+            "messages": [
+                {"role": "user", "content": "Hello"},
+            ],
+        }
+    )
+
+    assert body["model"] == "gpt-5.5"
+
+
+def test_codex_provider_metadata_uses_upstream_models_only_by_default(monkeypatch):
+    monkeypatch.setattr(
+        codex_provider,
+        "_codex_config",
+        lambda: {
+            "models": [],
+            "proxy_base_path": "/oauth/codex",
+            "callback_path": "/auth/callback",
+        },
+    )
+
+    metadata = codex_provider.CodexOAuthProvider().metadata()
+
+    assert metadata.default_model == "gpt-5.5"
+    assert metadata.default_models == []
+
+
+def test_codex_fetch_models_omits_fake_client_version(monkeypatch):
+    calls = []
+
+    class FakeResponse:
+        ok = True
+
+        def json(self):
+            return {"models": [{"slug": "upstream-model"}]}
+
+    monkeypatch.setattr(codex, "codex_config", lambda: {"models": []})
+    monkeypatch.setattr(codex, "resolve_codex_version", lambda: "")
+    monkeypatch.setattr(codex, "request_codex", lambda path, params=None: calls.append((path, params)) or FakeResponse())
+
+    assert codex.fetch_models() == ["upstream-model"]
+    assert calls == [("/models", None)]
+
+
 def test_chat_messages_to_response_body_preserves_image_parts_for_responses():
     data_url = "data:image/png;base64,abcd"
 
diff --git a/tests/test_oauth_github_copilot.py b/tests/test_oauth_github_copilot.py
index 2382f8c87..6af8dea08 100644
--- a/tests/test_oauth_github_copilot.py
+++ b/tests/test_oauth_github_copilot.py
@@ -120,7 +120,7 @@ def test_models_returns_curated_list_without_network(monkeypatch):
 
     models = provider.models()
 
-    assert models[:3] == ["gpt-5.2-codex", "gpt-5.2", "claude-sonnet-4.5"]
+    assert models[:3] == ["gpt-5.2", "claude-sonnet-4.5", "claude-opus-4.5"]
     assert "grok-code-fast-1" in models