diff --git a/install.sh b/install.sh
index b77fa37020..146a64e692 100755
--- a/install.sh
+++ b/install.sh
@@ -261,6 +261,20 @@ run_install_cmd_retry() {
 # shape on every AMD GPU; the fix (bnb #1887) is in the continuous-release_main
 # wheel used below and first ships on PyPI in 0.50.0, hence the fallback floor.
 _BNB_ROCM_PYPI_FALLBACK="bitsandbytes>=0.50.0"
+# bitsandbytes ships no ROCm binary in its aarch64 wheel at any version: the PyPI
+# 0.50.0 and continuous-release_main aarch64 wheels both carry only
+# libbitsandbytes_cpu.so plus CUDA variants. So neither install path below gives
+# aarch64 a 4-bit backend, and the messages must not claim one. Cf. gfx906.
+_bnb_rocm_arch_has_binary() {
+    case "$_ARCH" in
+        aarch64|arm64) return 1 ;;
+        *) return 0 ;;
+    esac
+}
+_warn_bnb_no_rocm_binary() {
+    _bnb_rocm_arch_has_binary && return 0
+    substep "[WARN] aarch64: bitsandbytes ships no ROCm kernels on this arch; 4-bit QLoRA needs a source build -- https://docs.unsloth.ai/get-started/install-and-update/amd" "$C_WARN"
+}
 _install_bnb_rocm() {
     _label="$1"
     _venv_py="$2"
@@ -292,6 +306,7 @@ _install_bnb_rocm() {
             --retries 8 --timeout 90 \
             "$_bnb_whl_url" >"$_bnb_log" 2>&1; then
             rm -f "$_bnb_log"
+            _warn_bnb_no_rocm_binary
             return 0
         fi
         _bnb_rc=$?
@@ -300,10 +315,17 @@ _install_bnb_rocm() {
         fi
         rm -f "$_bnb_log"
         step "warning" "$_label (pre-release) failed (exit code $_bnb_rc)" "$C_WARN" >&2
-        substep "[WARN] bnb pre-release install failed; falling back to PyPI $_BNB_ROCM_PYPI_FALLBACK, which carries the ROCm 4-bit fix" "$C_WARN"
+        if _bnb_rocm_arch_has_binary; then
+            substep "[WARN] bnb pre-release install failed; falling back to PyPI $_BNB_ROCM_PYPI_FALLBACK, which carries the ROCm 4-bit fix" "$C_WARN"
+        else
+            substep "[WARN] bnb pre-release install failed; falling back to PyPI $_BNB_ROCM_PYPI_FALLBACK" "$C_WARN"
+        fi
     fi
     run_install_cmd "$_label (pypi fallback)" "$_venv_py" -m pip install \
         --force-reinstall --no-cache-dir --no-deps "$_BNB_ROCM_PYPI_FALLBACK"
+    _bnb_pypi_rc=$?
+    _warn_bnb_no_rocm_binary
+    return $_bnb_pypi_rc
 }
 
 if [ "$_next_is_package" = true ]; then
diff --git a/studio/install_python_stack.py b/studio/install_python_stack.py
index 981ab651c8..533cb9b793 100644
--- a/studio/install_python_stack.py
+++ b/studio/install_python_stack.py
@@ -424,6 +424,16 @@ def _bnb_rocm_prerelease_url() -> str | None:
     return _BNB_ROCM_PRERELEASE_URLS.get(arch)
 
 
+def _bnb_rocm_arch_has_binary() -> bool:
+    """False on aarch64: bitsandbytes ships no ROCm kernels there at any version.
+    The PyPI 0.50.0 and continuous-release_main aarch64 wheels both carry only
+    libbitsandbytes_cpu.so plus CUDA variants, so neither install path gives
+    aarch64 a 4-bit backend and neither message may claim one.
+    """
+    arch = platform.machine().lower()
+    return {"amd64": "x86_64", "arm64": "aarch64"}.get(arch, arch) != "aarch64"
+
+
 def _amd_smi_env() -> dict[str, str] | None:
     """On Windows, env with __COMPAT_LAYER=RunAsInvoker; None elsewhere.
     NB: RunAsInvoker doesn't stop amd-smi's runtime elevation (its manifest is
@@ -2021,10 +2031,15 @@ def _ensure_rocm_torch() -> None:
                 force_pip = True,
             )
             if not _bnb_installed:
+                _fallback_note = (
+                    ", which carries the ROCm 4-bit fix"
+                    if _bnb_rocm_arch_has_binary()
+                    else ""
+                )
                 print(
                     _red(
                         "   bnb pre-release install failed; falling back to PyPI "
-                        f"{_BNB_ROCM_PYPI_FALLBACK}, which carries the ROCm 4-bit fix"
+                        f"{_BNB_ROCM_PYPI_FALLBACK}{_fallback_note}"
                     )
                 )
         if not _bnb_installed:
@@ -2036,6 +2051,14 @@ def _ensure_rocm_torch() -> None:
                 _BNB_ROCM_PYPI_FALLBACK,
                 constrain = False,
             )
+        if not _bnb_rocm_arch_has_binary():
+            print(
+                _red(
+                    "   aarch64: bitsandbytes ships no ROCm kernels on this arch; "
+                    "4-bit QLoRA needs a source build -- "
+                    "https://docs.unsloth.ai/get-started/install-and-update/amd"
+                )
+            )
 
 
 # _uv_safe_path is imported from backend.utils.uv_path_safety (shared with mlx_repair).
diff --git a/tests/python/test_cross_platform_parity.py b/tests/python/test_cross_platform_parity.py
index 9a183d2b4e..ef8926454f 100644
--- a/tests/python/test_cross_platform_parity.py
+++ b/tests/python/test_cross_platform_parity.py
@@ -876,3 +876,21 @@ class TestAmdBnbFloorParity:
             assert (
                 "4-bit decode will be broken on ROCm" not in text
             ), f"{path.name} still reports the repaired PyPI fallback as broken"
+
+    def test_aarch64_is_not_told_it_has_a_rocm_backend(self):
+        """bitsandbytes ships no ROCm kernels in its aarch64 wheel at any version, so
+        neither installer may hand aarch64 the x86_64 "carries the ROCm 4-bit fix"
+        message, and both must warn that 4-bit needs a source build there."""
+        sh = INSTALL_SH.read_text(encoding = "utf-8")
+        assert "_bnb_rocm_arch_has_binary()" in sh
+        assert "_warn_bnb_no_rocm_binary()" in sh
+        assert (
+            sh.count("_warn_bnb_no_rocm_binary\n") >= 2
+        ), "install.sh must warn on aarch64 after both the pre-release and the fallback install"
+        py = STACK_PY.read_text(encoding = "utf-8")
+        assert "def _bnb_rocm_arch_has_binary(" in py
+        assert "_bnb_rocm_arch_has_binary()" in py
+        for text, name in ((sh, "install.sh"), (py, "install_python_stack.py")):
+            assert (
+                "4-bit QLoRA needs a source build" in text
+            ), f"{name} must tell aarch64 users 4-bit needs a source build"