amd: raise the installer bitsandbytes fallback floors to 0.50.0

install.sh

@@ -259,8 +259,10 @@ run_install_cmd_retry() {
 
 # Install bitsandbytes on AMD ROCm hosts. Uses the continuous-release_main
 # wheel for the ROCm 4-bit GEMV fix (bnb PR #1887, post-0.49.2); bnb <= 0.49.2
-# NaNs at decode shape on every AMD GPU. Falls back to PyPI >=0.49.1 if the
-# pre-release URL is unreachable. Drop the pin once bnb 0.50+ ships on PyPI.
+# NaNs at decode shape on every AMD GPU. Falls back to PyPI >=0.50.0 if the
+# pre-release URL is unreachable: 0.50.0 (2026-07-24) is the first PyPI release
+# carrying that fix, and its manylinux x86_64 wheel ships the same
+# libbitsandbytes_rocm{64,70,71,714,72}.so set as the pre-release.
 _install_bnb_rocm() {
     _label="$1"
     _venv_py="$2"
@@ -277,7 +279,8 @@ _install_bnb_rocm() {
     esac
     # uv rejects the continuous-release_main bitsandbytes wheel because the
     # filename version (1.33.7rc0) does not match the embedded metadata version
-    # (0.50.0.dev0). pip accepts the mismatch, so bootstrap pip and use it.
+    # (0.50.x.dev0, whatever main is at). pip accepts the mismatch, so bootstrap
+    # pip and use it.
     if ! "$_venv_py" -m pip --version >/dev/null 2>&1; then
         if ! run_maybe_quiet "$_venv_py" -m ensurepip --upgrade; then
             run_maybe_quiet uv pip install --python "$_venv_py" pip || \
@@ -304,7 +307,7 @@ _install_bnb_rocm() {
         substep "[WARN] bnb pre-release install failed; falling back to PyPI (4-bit decode broken on ROCm)" "$C_WARN"
     fi
     run_install_cmd "$_label (pypi fallback)" "$_venv_py" -m pip install \
-        --force-reinstall --no-cache-dir --no-deps "bitsandbytes>=0.49.1"
+        --force-reinstall --no-cache-dir --no-deps "bitsandbytes>=0.50.0"
 }
 
 if [ "$_next_is_package" = true ]; then

studio/install_python_stack.py

@@ -390,7 +390,8 @@ _GFX_TO_AMD_INDEX_ARCH: dict[str, str] = {
 
 # bitsandbytes continuous-release_main wheels with the ROCm 4-bit GEMV fix
 # (bnb PR #1887, post-0.49.2). bnb <= 0.49.2 NaNs at decode shape on every
-# AMD GPU. Drop the pin once bnb 0.50+ ships on PyPI.
+# AMD GPU. PyPI 0.50.0 (2026-07-24) is the first release carrying that fix, so
+# _BNB_ROCM_PYPI_FALLBACK below is a safe floor when these URLs are unreachable.
 _BNB_ROCM_PRERELEASE_URLS: dict[str, str] = {
     "x86_64": (
         "https://github.com/bitsandbytes-foundation/bitsandbytes/releases/"
@@ -411,7 +412,8 @@ _BNB_ROCM_PRERELEASE_URLS: dict[str, str] = {
         "bitsandbytes-1.33.7.preview-py3-none-win_amd64.whl"
     ),
 }
-_BNB_ROCM_PYPI_FALLBACK = "bitsandbytes>=0.49.1"
+# Keep in step with the install.sh fallback (and the amd extra, once it lands here).
+_BNB_ROCM_PYPI_FALLBACK = "bitsandbytes>=0.50.0"
 
 
 def _bnb_rocm_prerelease_url() -> str | None:
@@ -1182,7 +1184,7 @@ def _install_bnb_windows_rocm() -> bool:
 
     The continuous-release wheel is intentionally mismatched: the filename
     encodes 1.33.7.preview (parsed as 1.33.7rc0 by PEP 440) while the wheel
-    metadata reports 0.50.0.dev0. uv rejects this filename/metadata mismatch,
+    metadata reports 0.50.x.dev0. uv rejects this filename/metadata mismatch,
     and bypassing it with UV_SKIP_WHEEL_FILENAME_CHECK still leaves uv mangling
     the bitsandbytes install. Per the AMD install guide
     (https://unsloth.ai/docs/get-started/install/amd/amd-hackathon) the wheel

tests/python/test_cross_platform_parity.py

@@ -818,3 +818,49 @@ class TestPipNoIndexScrubParity:
         text = SETUP_PS1.read_text(encoding = "utf-8")
         assert "'PIP_NO_INDEX'" in text
         assert "'PIP_INDEX_URL'" in text
+
+
+class TestAmdBnbFloorParity:
+    """bitsandbytes <= 0.49.2 NaNs at 4-bit decode shape on every AMD GPU; the ROCm
+    4-bit GEMV fix (bnb #1887) first ships on PyPI in 0.50.0. The install.sh PyPI
+    fallback and the Studio stack fallback are the two ways a supported AMD flow
+    resolves bitsandbytes when the pre-release wheel URL is unreachable, so neither
+    may float back into the broken range."""
+
+    FLOOR = "0.50.0"
+    PYPROJECT = REPO_ROOT / "pyproject.toml"
+
+    def test_install_sh_pypi_fallback_floor(self):
+        text = INSTALL_SH.read_text(encoding = "utf-8")
+        assert f'"bitsandbytes>={self.FLOOR}"' in text, (
+            f"install.sh _install_bnb_rocm PyPI fallback must floor at {self.FLOOR}"
+        )
+
+    def test_stack_py_pypi_fallback_floor(self):
+        text = STACK_PY.read_text(encoding = "utf-8")
+        assert f'_BNB_ROCM_PYPI_FALLBACK = "bitsandbytes>={self.FLOOR}"' in text, (
+            f"install_python_stack.py PyPI fallback must floor at {self.FLOOR}"
+        )
+
+    def test_amd_extra_floor_when_present(self):
+        """The amd extra is not on this branch yet (#7278). Assert it only once it is,
+        so the extra and the two installer fallbacks cannot drift apart later."""
+        text = self.PYPROJECT.read_text(encoding = "utf-8")
+        amd = re.search(r"^amd = \[(.*?)^\]", text, re.S | re.M)
+        if amd is None:
+            pytest.skip("pyproject.toml has no amd extra on this branch")
+        specs = re.findall(r'"(bitsandbytes[^"]*)"', amd.group(1))
+        assert specs, "the amd extra must pin bitsandbytes"
+        for spec in specs:
+            assert spec.startswith(f"bitsandbytes>={self.FLOOR}"), (
+                f"amd extra bitsandbytes floor must be >={self.FLOOR}, got {spec!r}"
+            )
+
+    def test_no_installer_still_allows_the_broken_range(self):
+        for path in (INSTALL_SH, INSTALL_PS1, SETUP_PS1, STACK_PY, self.PYPROJECT):
+            text = path.read_text(encoding = "utf-8")
+            for line in text.splitlines():
+                if "bitsandbytes>=0.49" in line and not line.lstrip().startswith(("#", "//")):
+                    raise AssertionError(
+                        f"{path.name} still floors bitsandbytes in the broken ROCm range: {line.strip()!r}"
+                    )