diff --git a/.github/actions/nvcc-toolchain/install-cuda.ps1 b/.github/actions/nvcc-toolchain/install-cuda.ps1
index a0732e154..f98b2b40d 100644
--- a/.github/actions/nvcc-toolchain/install-cuda.ps1
+++ b/.github/actions/nvcc-toolchain/install-cuda.ps1
@@ -21,9 +21,19 @@ $mmbVersionTag = "${major}.${minor}.${build}"
 # mm = major minor
 $mmVersionTag = "${major}.${minor}"
 
-# `cuda_${mmbVersionTag}_windows_network.exe` name only valid back to CUDA v11.5.1.
-# Before that it was named `cuda_${mmbVersionTag}_win10_network.exe`.
 $cudaVersionUrl = "https://developer.download.nvidia.com/compute/cuda/${mmbVersionTag}/network_installers/cuda_${mmbVersionTag}_windows_network.exe"
+
+###
+# `cuda_${mmbVersionTag}_windows_network.exe` name only valid back to CUDA v11.5.1.
+# Before that it was named `cuda_${mmbVersionTag}_win10_network.exe`:
+# * https://developer.download.nvidia.com/compute/cuda/11.5.1/network_installers/cuda_11.5.1_windows_network.exe
+# * https://developer.download.nvidia.com/compute/cuda/11.5.0/network_installers/cuda_11.5.0_win10_network.exe
+###
+
+if ([version]$mmbVersionTag -le "11.5.0") {
+    $cudaVersionUrl = "https://developer.download.nvidia.com/compute/cuda/${mmbVersionTag}/network_installers/cuda_${mmbVersionTag}_win10_network.exe"
+}
+
 $cudaComponents =
     "nvcc_$mmVersionTag",
     "curand_$mmVersionTag",
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c03bc2bee..bd8650ba0 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -66,6 +66,10 @@ jobs:
       matrix:
         include:
           - os: ubuntu-20.04
+            # Oldest tested CUDA Toolkit version. Older CTKs might work, but they're
+            # difficult to test without Ubuntu18.04 GHA runners or containerized jobs.
+            cuda: "11.1"
+            extra_desc: cuda11.1
             # Oldest supported version, keep in sync with README.md
             rustc: "1.75.0"
           - os: ubuntu-22.04
@@ -97,11 +101,11 @@ jobs:
           # # M1 CPU
           - os: macos-14
           - os: windows-2019
-            cuda: "11.8"
+            cuda: "11.1"
             # Oldest supported version, keep in sync with README.md
             rustc: "1.75.0"
             extra_args: --no-fail-fast
-            extra_desc: cuda11.8
+            extra_desc: cuda11.1
           - os: windows-2019
             cuda: "11.8"
             rustc: nightly
@@ -152,7 +156,14 @@ jobs:
             sudo apt remove -y gcc-14 g++-14
             sudo apt autoremove -y
           fi
-          sudo apt install -y --no-install-recommends clang gcc
+          # Ubuntu20.04's clang-10 is too old for CTK 11+, so install clang-12 instead
+          if test "${{ matrix.os }}" = "ubuntu-20.04" && test -n "${{ matrix.cuda }}"; then
+            sudo apt install -y --no-install-recommends gcc clang-12
+            sudo ln -sf $(which clang-12) /usr/bin/clang
+            sudo ln -sf $(which clang++-12) /usr/bin/clang++
+          else
+            sudo apt install -y --no-install-recommends gcc clang
+          fi
           echo 'gcc version:'
           gcc --version
           echo 'clang version:'
diff --git a/src/compiler/nvcc.rs b/src/compiler/nvcc.rs
index 9087dca3d..5da0a53a4 100644
--- a/src/compiler/nvcc.rs
+++ b/src/compiler/nvcc.rs
@@ -837,7 +837,7 @@ where
         } {
             if log_enabled!(log::Level::Trace) {
                 trace!(
-                    "[{}]: transformed nvcc command: {:?}",
+                    "[{}]: transformed nvcc command: \"{}\"",
                     output_file_name.to_string_lossy(),
                     [
                         &[format!("cd {} &&", dir.to_string_lossy()).to_string()],
@@ -1032,7 +1032,8 @@ fn fold_env_vars_or_split_into_exe_and_args(
         let line = line
             .replace("\"\"", "\"")
             .replace(r"\\?\", "")
-            .replace('\\', "/");
+            .replace('\\', "/")
+            .replace(r"//?/", "");
         match host_compiler {
             NvccHostCompiler::Msvc => line.replace(" -E ", " -P ").replace(" > ", " -Fi"),
             _ => line,
@@ -1202,14 +1203,12 @@ where
 
         if log_enabled!(log::Level::Trace) {
             trace!(
-                "[{}]: run_commands_sequential cwd={:?}, cmd={:?}",
+                "[{}]: run_commands_sequential cwd={:?}, cmd=\"{}\"",
                 output_file_name.to_string_lossy(),
                 cwd,
                 [
                     vec![exe.clone().into_os_string().into_string().unwrap()],
-                    args.iter()
-                        .map(|x| shlex::try_quote(x).unwrap().to_string())
-                        .collect::<Vec<_>>()
+                    args.to_vec()
                 ]
                 .concat()
                 .join(" ")