diff --git a/docker/Dockerfile.studio b/docker/Dockerfile.studio
index 40dfbcd69f..fc77902f15 100644
--- a/docker/Dockerfile.studio
+++ b/docker/Dockerfile.studio
@@ -101,6 +101,12 @@ RUN set -eux \
  && UNSLOTH_STUDIO_HOME="${UNSLOTH_STUDIO_HOME}" \
     UNSLOTH_TORCH_INDEX_FAMILY="${TORCH_FAMILY}" \
     bash install.sh --local \
+    # Fail loud if the Studio venv torch missed the pinned CUDA family (an
+    # install.sh that ignores UNSLOTH_TORCH_INDEX_FAMILY falls back to
+    # nvidia-smi probing, which cannot work at build time and lands on cu126
+    # wheels with no sm_100/sm_120 kernels). metadata check only: importing
+    # torch needs native libs, which QEMU arm64 builds cannot load.
+ && "${UNSLOTH_STUDIO_HOME}/unsloth_studio/bin/python" -c "from importlib.metadata import version; v = version('torch'); assert v.endswith('+${TORCH_FAMILY}'), 'Studio venv torch ' + v + ' does not match ${TORCH_FAMILY}'; print('Studio venv torch', v)" \
  && rm -rf "${UNSLOTH_STUDIO_HOME}/src/.git" /root/.cache \
  && if [ "${TARGETARCH:-amd64}" = "arm64" ]; then \
         for NVRTC_DIR in "${UNSLOTH_STUDIO_HOME}"/unsloth_studio/lib/python*/site-packages/nvidia/cuda_nvrtc/lib; do \
diff --git a/studio/install_python_stack.py b/studio/install_python_stack.py
index e540aac305..8f7c2d2c5a 100644
--- a/studio/install_python_stack.py
+++ b/studio/install_python_stack.py
@@ -816,6 +816,12 @@ def _detect_cuda_torch_index_url() -> str:
     Defaults to cu126 when nvidia-smi is missing or the version is unreadable
     (e.g. NVIDIA detected only via the /proc/driver/nvidia/gpus fallback).
     """
+    # Explicit override (parity with install.sh / install.ps1):
+    # UNSLOTH_TORCH_INDEX_FAMILY=cu128|cu130|cu126|cpu|... pins the wheel
+    # index when probing is wrong or impossible (no GPU at build time, CI).
+    family = os.environ.get("UNSLOTH_TORCH_INDEX_FAMILY")
+    if family:
+        return f"{_PYTORCH_WHL_BASE}/{family}"
     exe = shutil.which("nvidia-smi")
     if not exe and os.path.isfile("/usr/bin/nvidia-smi"):
         exe = "/usr/bin/nvidia-smi"