diff --git a/.ci/scripts/setup-vulkan-linux-deps.sh b/.ci/scripts/setup-vulkan-linux-deps.sh
index debe610a18a..c1981d5050b 100755
--- a/.ci/scripts/setup-vulkan-linux-deps.sh
+++ b/.ci/scripts/setup-vulkan-linux-deps.sh
@@ -67,35 +67,37 @@ install_vulkan_loader() {
   # libvulkan.so.1 (the Khronos loader that volk dlopen()s at runtime) is not part
   # of the NVIDIA driver and is absent from the CUDA builder image; vulkan-tools
   # provides vulkaninfo for the device sanity check. Both ship as native el8 RPMs.
+  # The NVIDIA ICD also needs EGL and X11 client libraries on headless runners.
   if command -v dnf >/dev/null 2>&1; then
-    _maybe_sudo dnf install -y vulkan-loader vulkan-tools
+    _maybe_sudo dnf install -y vulkan-loader vulkan-tools libglvnd-egl libX11 libXext
   fi
 }
 
 _find_nvidia_vulkan_library() {
-  # NVIDIA implements its Vulkan ICD inside libGLX_nvidia.so.0. The NVIDIA
-  # container runtime mounts this library into the container (it is pulled from
-  # the driver's ldcache when NVIDIA_DRIVER_CAPABILITIES includes graphics/all),
-  # so prefer ldconfig and fall back to the usual mount locations.
-  local lib cand
-  lib="$(ldconfig -p 2>/dev/null | awk '/libGLX_nvidia\.so\.0/ {print $NF; exit}')"
-  if [ -z "${lib}" ]; then
-    for cand in /usr/lib64/libGLX_nvidia.so.0 \
-        /usr/lib/x86_64-linux-gnu/libGLX_nvidia.so.0 \
-        /usr/lib/libGLX_nvidia.so.0; do
+  # NVIDIA provides EGL and GLX Vulkan ICDs. Prefer EGL on headless runners;
+  # the GLX entry point can fail to initialize without an X server.
+  local soname lib cand
+  for soname in libEGL_nvidia.so.0 libGLX_nvidia.so.0; do
+    lib="$(ldconfig -p 2>/dev/null | awk -v name="${soname}" '$1 == name {print $NF; exit}')"
+    if [ -n "${lib}" ]; then
+      printf '%s' "${lib}"
+      return
+    fi
+    for cand in "/usr/lib64/${soname}" \
+        "/usr/lib/x86_64-linux-gnu/${soname}" \
+        "/usr/lib/${soname}"; do
       if [ -e "${cand}" ]; then
-        lib="${cand}"
-        break
+        printf '%s' "${cand}"
+        return
       fi
     done
-  fi
-  printf '%s' "${lib}"
+  done
 }
 
 _vulkan_has_real_device() {
   # True if the loader enumerates a hardware GPU. vulkaninfo can exit non-zero
   # for unrelated reasons (no display/WSI), so key off the reported deviceType.
-  command -v vulkaninfo >/dev/null 2>&1 || return 0
+  command -v vulkaninfo >/dev/null 2>&1 || return 1
   vulkaninfo --summary 2>/dev/null |
     grep -qE 'PHYSICAL_DEVICE_TYPE_(DISCRETE|INTEGRATED|VIRTUAL)_GPU'
 }
@@ -131,25 +133,24 @@ JSON
       echo "Real NVIDIA GPU selected; pinned Vulkan ICD to ${nvidia_lib}"
       return
     fi
-    echo "WARNING: ${nvidia_lib} present but no GPU enumerated; using SwiftShader."
-    # Surface why the NVIDIA driver did not enumerate (e.g. a missing dependency
-    # of libGLX_nvidia, or no render node) so the fallback is diagnosable in CI.
+    echo "ERROR: ${nvidia_lib} present but no GPU enumerated."
+    # Surface missing ICD dependencies and device-enumeration errors.
+    ldd "${nvidia_lib}" || true
     if command -v vulkaninfo >/dev/null 2>&1; then
       echo "--- NVIDIA Vulkan ICD diagnostic ---"
       VK_LOADER_DEBUG=warn vulkaninfo --summary 2>&1 | head -40 || true
       echo "--- end diagnostic ---"
     fi
-    unset VK_ICD_FILENAMES
   else
-    echo "WARNING: no NVIDIA Vulkan driver library found; using SwiftShader."
+    echo "ERROR: no NVIDIA Vulkan driver library found."
   fi
-  install_swiftshader
+  return 1
 }
 
 VULKAN_SDK_VERSION="1.4.321.1"
 
 # The no-argument default installs SwiftShader so the existing CPU-runner CI is
-# unchanged. Pass "real-gpu" to prefer a real system ICD when one is present.
+# unchanged. Pass "real-gpu" to require a real system ICD.
 case "${1:-swiftshader}" in
   real-gpu)
     # Do not download the LunarG SDK here: its prebuilt glslc cannot run on the
diff --git a/.ci/scripts/test_backend.sh b/.ci/scripts/test_backend.sh
index 068d5adb260..8bfe33333a8 100755
--- a/.ci/scripts/test_backend.sh
+++ b/.ci/scripts/test_backend.sh
@@ -54,15 +54,8 @@ if [[ "$FLOW" == *qnn* ]]; then
 fi
 
 if [[ "$FLOW" == *vulkan* ]]; then
-    # Setup the Vulkan SDK and select an ICD: use the real system GPU ICD when one
-    # is present (real-GPU runner), otherwise fall back to SwiftShader (CPU
-    # runner). The Vulkan loader searches both standard ICD directories.
-    if ls /etc/vulkan/icd.d/*.json /usr/share/vulkan/icd.d/*.json \
-        >/dev/null 2>&1; then
-        source .ci/scripts/setup-vulkan-linux-deps.sh "real-gpu"
-    else
-        source .ci/scripts/setup-vulkan-linux-deps.sh "swiftshader"
-    fi
+    # CPU runners can have Mesa ICDs installed without a usable hardware GPU.
+    source .ci/scripts/setup-vulkan-linux-deps.sh "swiftshader"
 
     EXTRA_BUILD_ARGS+=" -DEXECUTORCH_BUILD_VULKAN=ON"
 fi
diff --git a/.github/workflows/pull.yml b/.github/workflows/pull.yml
index 2f91799b9a4..a70a824f223 100644
--- a/.github/workflows/pull.yml
+++ b/.github/workflows/pull.yml
@@ -1682,6 +1682,7 @@ jobs:
         # route in the future.
         python -m unittest backends/vulkan/test/test_vulkan_delegate.py -k "*pt2e*"
         python -m unittest backends/vulkan/test/test_vulkan_delegate.py -k "*torchao*"
+        python -m unittest backends/vulkan/test/test_vulkan_graph_builder.py
 
   test-coreml-bc-macos:
     needs: [changed-files, run-decision]
diff --git a/.github/workflows/vulkan.yml b/.github/workflows/vulkan.yml
index 2514a8d582c..dd3de1f33fb 100644
--- a/.github/workflows/vulkan.yml
+++ b/.github/workflows/vulkan.yml
@@ -70,10 +70,7 @@ jobs:
         # not run, so setup-vulkan-linux-deps.sh sources those from conda-forge and
         # the system package manager instead. The NVIDIA container runtime mounts
         # the driver's Vulkan library but not its ICD manifest, so the script
-        # synthesizes one and pins the loader to it; if no NVIDIA library is found
-        # it falls back to SwiftShader.
-        # NOTE: first-run check - inspect the vulkaninfo output below to confirm a
-        # real NVIDIA device is selected (not llvmpipe/SwiftShader).
+        # synthesizes one and requires the loader to enumerate a hardware GPU.
         source .ci/scripts/setup-vulkan-linux-deps.sh real-gpu
         vulkaninfo --summary || true
 
@@ -100,23 +97,16 @@ jobs:
 
         # Operator coverage (mirrors test-vulkan-operators-linux, on real hardware).
         # The custom-op prototyping binaries are GPU microbenchmarks that rely on
-        # GPU timestamp queries; they need a real device and crash on the
-        # SwiftShader software fallback. Always build them (compile coverage), but
-        # only run them when a real GPU was selected (setup-vulkan-linux-deps.sh
-        # exports ETVK_USING_SWIFTSHADER when it falls back to SwiftShader).
+        # GPU timestamp queries, so they require the hardware selected above.
         PYTHON_EXECUTABLE=python bash backends/vulkan/test/custom_ops/build_and_run.sh
-        if [ -z "${ETVK_USING_SWIFTSHADER:-}" ]; then
-          ./cmake-out/backends/vulkan/test/custom_ops/test_add
-          ./cmake-out/backends/vulkan/test/custom_ops/test_q8csw_linear
-          ./cmake-out/backends/vulkan/test/custom_ops/test_q8csw_conv2d
-          ./cmake-out/backends/vulkan/test/custom_ops/test_q4gsw_linear
-          ./cmake-out/backends/vulkan/test/custom_ops/test_choose_qparams_per_row
-          ./cmake-out/backends/vulkan/test/custom_ops/test_q8ta_qdq
-          ./cmake-out/backends/vulkan/test/custom_ops/test_q8ta_clone
-          ./cmake-out/backends/vulkan/test/custom_ops/test_q8ta_binary
-        else
-          echo "SwiftShader fallback active: built custom-op benchmarks but skipping execution (they require real-GPU timestamp queries)."
-        fi
+        ./cmake-out/backends/vulkan/test/custom_ops/test_add
+        ./cmake-out/backends/vulkan/test/custom_ops/test_q8csw_linear
+        ./cmake-out/backends/vulkan/test/custom_ops/test_q8csw_conv2d
+        ./cmake-out/backends/vulkan/test/custom_ops/test_q4gsw_linear
+        ./cmake-out/backends/vulkan/test/custom_ops/test_choose_qparams_per_row
+        ./cmake-out/backends/vulkan/test/custom_ops/test_q8ta_qdq
+        ./cmake-out/backends/vulkan/test/custom_ops/test_q8ta_clone
+        ./cmake-out/backends/vulkan/test/custom_ops/test_q8ta_binary
 
         PYTHON_EXECUTABLE=python bash backends/vulkan/test/scripts/test_op.sh --build
 
diff --git a/backends/vulkan/serialization/vulkan_graph_builder.py b/backends/vulkan/serialization/vulkan_graph_builder.py
index 3de60966422..8703d391ce0 100644
--- a/backends/vulkan/serialization/vulkan_graph_builder.py
+++ b/backends/vulkan/serialization/vulkan_graph_builder.py
@@ -231,13 +231,7 @@ def create_null_value(self) -> int:
         return new_id
 
     def get_or_create_scalar_value(self, scalar: _ScalarType) -> int:
-        scalar_key = scalar
-        # Since Python considers 1 and True to be "equivalent" (as well as 0 and False)
-        # to distinguish entries in the dictionary, if scalar is bool then convert it
-        # to a string representation to use as a key for the dictionary
-        if isinstance(scalar, bool):
-            scalar_key = str(scalar)
-
+        scalar_key = (type(scalar), repr(scalar))
         if scalar_key in self.const_scalar_to_value_ids:
             return self.const_scalar_to_value_ids[scalar_key]
 
diff --git a/backends/vulkan/test/targets.bzl b/backends/vulkan/test/targets.bzl
index 77e74f9c8fc..5734e733195 100644
--- a/backends/vulkan/test/targets.bzl
+++ b/backends/vulkan/test/targets.bzl
@@ -29,6 +29,17 @@ def define_common_targets(is_fbcode = False):
             ],
         )
 
+        python_unittest(
+            name = "test_vulkan_graph_builder",
+            srcs = ["test_vulkan_graph_builder.py"],
+            deps = [
+                "//caffe2:torch",
+                "//executorch/backends/vulkan/serialization:lib",
+                "//executorch/backends/vulkan:vulkan_preprocess",
+                "//executorch/exir:lib",
+            ],
+        )
+
         python_unittest(
             name = "test_vulkan_passes",
             srcs = [
diff --git a/backends/vulkan/test/test_vulkan_graph_builder.py b/backends/vulkan/test/test_vulkan_graph_builder.py
index 65afc3a2542..c180308e77a 100644
--- a/backends/vulkan/test/test_vulkan_graph_builder.py
+++ b/backends/vulkan/test/test_vulkan_graph_builder.py
@@ -8,12 +8,40 @@
 
 import torch
 from executorch.backends.vulkan.serialization.vulkan_graph_builder import VkGraphBuilder
+from executorch.backends.vulkan.serialization.vulkan_graph_schema import (
+    Bool,
+    Double,
+    Int,
+)
 from executorch.backends.vulkan.vulkan_preprocess import apply_passes
 from executorch.exir import to_edge
 from executorch.exir.backend.utils import DelegateMappingBuilder
 from executorch.exir.passes import SpecPropPass
 
 
+class TestVkGraphBuilderScalarTensor(unittest.TestCase):
+    def test_scalar_cache_preserves_types_and_signed_zero(self):
+        program = torch.export.export(torch.nn.Identity(), (torch.ones(1),))
+        builder = VkGraphBuilder(
+            program, DelegateMappingBuilder(generated_identifiers=True)
+        )
+        scalars = (1.0, 1, True, 0.0, -0.0, 0, False)
+        expected = (
+            Double(1.0),
+            Int(1),
+            Bool(True),
+            Double(0.0),
+            Double(-0.0),
+            Int(0),
+            Bool(False),
+        )
+        ids = [builder.get_or_create_scalar_value(value) for value in scalars]
+        self.assertEqual(len(set(ids)), len(scalars))
+        for value, value_id, serialized in zip(scalars, ids, expected):
+            self.assertEqual(builder.get_or_create_scalar_value(value), value_id)
+            self.assertEqual(repr(builder.values[value_id].value), repr(serialized))
+
+
 class TestVkGraphBuilderInputIds(unittest.TestCase):
     """The serialized input list has to match the delegate call's arguments.