diff --git a/install.sh b/install.sh
index 548e6f702a..8e30264df0 100755
--- a/install.sh
+++ b/install.sh
@@ -1985,6 +1985,21 @@ _has_usable_nvidia_gpu() {
 get_torch_index_url() {
     _base="${UNSLOTH_PYTORCH_MIRROR:-https://download.pytorch.org/whl}"
     _base="${_base%/}"
+    # Explicit override -- skip ALL GPU probing when the caller pins the wheel
+    # index. Headless / container / CI builds (and anyone cross-installing for a
+    # different target) must not let the build host's GPU -- or the lack of one --
+    # decide the wheel family. This is the same "tell the build, don't ask the
+    # hardware" approach the Docker base image and vLLM/SGLang's Dockerfiles take.
+    # UNSLOTH_TORCH_INDEX_URL wins (full URL, verbatim); UNSLOTH_TORCH_INDEX_FAMILY
+    # is the convenience form (cpu, cu124, cu126, cu128, cu130, rocm6.4, ...)
+    # appended to the mirror base so UNSLOTH_PYTORCH_MIRROR is still honoured.
+    if [ -n "${UNSLOTH_TORCH_INDEX_URL:-}" ]; then
+        echo "${UNSLOTH_TORCH_INDEX_URL%/}"; return
+    fi
+    if [ -n "${UNSLOTH_TORCH_INDEX_FAMILY:-}" ]; then
+        _family="${UNSLOTH_TORCH_INDEX_FAMILY#/}"
+        echo "$_base/${_family%/}"; return
+    fi
     # macOS: always CPU (no CUDA support)
     case "$(uname -s)" in Darwin) echo "$_base/cpu"; return ;; esac
     # Try nvidia-smi -- require the binary to actually list a usable GPU.
diff --git a/studio/install_python_stack.py b/studio/install_python_stack.py
index 9060b57542..222cfacb72 100644
--- a/studio/install_python_stack.py
+++ b/studio/install_python_stack.py
@@ -933,11 +933,20 @@ def _detect_cuda_torch_index_url() -> str:
 
     Mirrors install.sh::get_torch_index_url's CUDA ladder so `studio update`
     repairs to the same wheel family a fresh `curl | sh` install would pick.
-    Probes nvidia-smi (PATH, then /usr/bin/nvidia-smi) and parses both the
-    legacy "CUDA Version:" and the newer "CUDA UMD Version:" spellings.
-    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).
+    Honours the same explicit overrides first (UNSLOTH_TORCH_INDEX_URL /
+    UNSLOTH_TORCH_INDEX_FAMILY) so a headless / container / CI install never lets
+    the host GPU decide the wheel family. Otherwise probes nvidia-smi (PATH, then
+    /usr/bin/nvidia-smi) and parses both the legacy "CUDA Version:" and the newer
+    "CUDA UMD Version:" spellings. 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).
     """
+    _override_url = os.environ.get("UNSLOTH_TORCH_INDEX_URL", "").strip()
+    if _override_url:
+        return _override_url.rstrip("/")
+    _override_family = os.environ.get("UNSLOTH_TORCH_INDEX_FAMILY", "").strip()
+    if _override_family:
+        return f"{_PYTORCH_WHL_BASE}/{_override_family.strip('/')}"
     exe = shutil.which("nvidia-smi")
     if not exe and os.path.isfile("/usr/bin/nvidia-smi"):
         exe = "/usr/bin/nvidia-smi"
diff --git a/tests/sh/test_get_torch_index_url.sh b/tests/sh/test_get_torch_index_url.sh
index 6656142625..b9d0c5e5a1 100755
--- a/tests/sh/test_get_torch_index_url.sh
+++ b/tests/sh/test_get_torch_index_url.sh
@@ -379,6 +379,42 @@ _result=$(run_func "$_dir" " -1 ")
 assert_eq "CVD=' -1 ' hides NVIDIA -> cpu" "https://download.pytorch.org/whl/cpu" "$_result"
 rm -rf "$_dir"
 
+# --- explicit overrides (headless / container / CI; no GPU probing) ----------
+# 39) UNSLOTH_TORCH_INDEX_FAMILY pins the family with no GPU present -> that
+#     family (not the cpu fallback detection would pick).
+_result=$(UNSLOTH_TORCH_INDEX_FAMILY="cu128" run_func "none")
+assert_eq "family override (no GPU) -> cu128" "https://download.pytorch.org/whl/cu128" "$_result"
+
+# 40) Family override wins over a real detection: a host whose nvidia-smi reports
+#     12.6 still gets cu128. This is the exact Docker-build case (the builder sees
+#     the host driver but must publish a cu128 image).
+_dir=$(make_mock_smi "12.6")
+_result=$(UNSLOTH_TORCH_INDEX_FAMILY="cu128" run_func "$_dir")
+assert_eq "family override beats detected 12.6 -> cu128" "https://download.pytorch.org/whl/cu128" "$_result"
+rm -rf "$_dir"
+
+# 41) UNSLOTH_TORCH_INDEX_URL is used verbatim and wins over detection.
+_dir=$(make_mock_smi "12.6")
+_result=$(UNSLOTH_TORCH_INDEX_URL="https://mirror.example.com/whl/cu999" run_func "$_dir")
+assert_eq "url override beats detection -> verbatim" "https://mirror.example.com/whl/cu999" "$_result"
+rm -rf "$_dir"
+
+# 42) Family override is appended to UNSLOTH_PYTORCH_MIRROR (mirror still honoured).
+_result=$(UNSLOTH_PYTORCH_MIRROR="https://mirror.example.com/whl" UNSLOTH_TORCH_INDEX_FAMILY="cu128" run_func "none")
+assert_eq "mirror + family override -> mirror/cu128" "https://mirror.example.com/whl/cu128" "$_result"
+
+# 43) Trailing slash in UNSLOTH_TORCH_INDEX_URL is stripped.
+_result=$(UNSLOTH_TORCH_INDEX_URL="https://mirror.example.com/whl/cu128/" run_func "none")
+assert_eq "url override trailing slash stripped" "https://mirror.example.com/whl/cu128" "$_result"
+
+# 44) URL override takes precedence over family override.
+_result=$(UNSLOTH_TORCH_INDEX_URL="https://mirror.example.com/whl/cu130" UNSLOTH_TORCH_INDEX_FAMILY="cu128" run_func "none")
+assert_eq "url override beats family override -> url" "https://mirror.example.com/whl/cu130" "$_result"
+
+# 45) An empty override is ignored (falls through to normal detection).
+_result=$(UNSLOTH_TORCH_INDEX_FAMILY="" UNSLOTH_TORCH_INDEX_URL="" run_func "none")
+assert_eq "empty overrides ignored -> detected cpu" "https://download.pytorch.org/whl/cpu" "$_result"
+
 rm -f "$_FUNC_FILE"
 rm -rf "$_FAKE_SMI_DIR"
 rm -rf "$_TOOLS_DIR"