Studio: spoof-aware Codex availability probe + autouse fixture

When ``UNSLOTH_CODEX_SPOOF=1`` is exported (the credit-free dev / CI
path the previous commit added), the in-process spoof IS the Codex
SDK and a real ``codex`` CLI is irrelevant. The status endpoint at
``/api/codex/status`` used to gate ``installed`` on the real CLI +
real SDK only, which made the frontend hide the Codex provider in
the connections dropdown even when the spoof was active. Now both
``_sdk_importable`` and ``probe_codex_availability`` short-circuit on
``codex_spoof.is_spoof_enabled()`` so the provider becomes visible
under the spoof. ``installed=True``, ``cli_path="<spoof>"``,
``logged_in=True``, ``version="spoof"`` -- a sentinel that lets devs
read off "yes I am under the spoof" at a glance.

Real production code path (no spoof flag) is unchanged: still gates
on bool(cli_path) AND sdk_ok the same as round 6.

Tests: added an autouse fixture in ``test_codex_provider.py`` that
clears ``UNSLOTH_CODEX_SPOOF`` before every test so the existing
availability / import gating tests are not polluted when a dev runs
the suite with the flag exported. The spoof-targeted tests still
call ``monkeypatch.setenv(...)`` to flip it back on inside their own
scope. 69/69 pass with and without the env flag.

studio/backend/core/inference/codex_availability.py

@@ -146,7 +146,19 @@ def _sdk_importable() -> bool:
     Probes both ``openai_codex`` (the canonical upstream package name
     at ``openai/codex/sdk/python``) and ``codex_app_server`` (the Rust
     crate name, kept as a forward-compat alias).
+
+    When ``UNSLOTH_CODEX_SPOOF=1`` is set we report importable=True so
+    the frontend exposes the Codex provider in dev / CI without a real
+    SDK install. The spoof module gets swapped into ``sys.modules`` on
+    first ``_import_codex`` call, so any downstream consumer that
+    actually imports also succeeds.
     """
+    try:
+        from core.inference import codex_spoof
+        if codex_spoof.is_spoof_enabled():
+            return True
+    except Exception:
+        pass
     for name in _SDK_MODULE_NAMES:
         try:
             if importlib.util.find_spec(name) is not None:
@@ -338,17 +350,28 @@ async def probe_codex_availability() -> dict[str, Any]:
     cli_path = _which_codex()
     sdk_ok = _sdk_importable()
 
+    # Spoof mode also fakes the CLI half of the install signal so the
+    # frontend stops hiding the Codex provider in dev / CI. ``installed``
+    # gates on the spoof being explicitly opted in, so production hosts
+    # without the flag still see the real CLI / SDK gating intact.
+    spoof_active = False
+    try:
+        from core.inference import codex_spoof
+        spoof_active = codex_spoof.is_spoof_enabled()
+    except Exception:
+        pass
+
     payload: dict[str, Any] = {
         # Gate on BOTH because the login flow shells out to `codex`.
         # Round 5 briefly set this to `sdk_ok` alone, but round 6
         # caught that the login route would then fail with
         # `codex CLI not found on PATH` after the user clicked
         # Sign in, leaving them with an unusable provider row.
-        "installed": bool(cli_path) and sdk_ok,
-        "cli_path": cli_path,
+        "installed": (bool(cli_path) and sdk_ok) or spoof_active,
+        "cli_path": cli_path or ("<spoof>" if spoof_active else None),
         "sdk_importable": sdk_ok,
-        "logged_in": False,
-        "version": None,
+        "logged_in": spoof_active,
+        "version": "spoof" if spoof_active else None,
         "supported_models": list(_DEFAULT_SUPPORTED_MODELS),
     }
 

studio/backend/tests/test_codex_provider.py

@@ -34,6 +34,18 @@ from typing import Any
 import pytest
 
 
+@pytest.fixture(autouse = True)
+def _no_spoof_by_default(monkeypatch):
+    """Tests in this file assume the real-SDK gating path unless they
+    explicitly re-enable the spoof. The dev environment sometimes has
+    UNSLOTH_CODEX_SPOOF=1 exported for the live UI; clearing it here
+    keeps the existing availability + import tests deterministic.
+    Tests that exercise the spoof use ``monkeypatch.setenv(...)`` to
+    flip it back on inside their own scope.
+    """
+    monkeypatch.delenv("UNSLOTH_CODEX_SPOOF", raising = False)
+
+
 _backend = os.path.join(os.path.dirname(__file__), "..")
 if _backend not in sys.path:
     sys.path.insert(0, _backend)