Refresh Codex OAuth model defaults

Stop seeding stale Codex OAuth model metadata so connected accounts use the upstream /models response instead of the retired gpt-5.2-codex default.

Use gpt-5.5 as the Codex proxy fallback model, omit the fake legacy client version when Codex CLI is unavailable, and remove the stale Copilot fallback entry.

Add focused OAuth regressions for the current default model, upstream model-list behavior, and Copilot fallback ordering.

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]:

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"],

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,