diff --git a/.github/workflows/testing.yml b/.github/workflows/testing.yml
index 586558d9..4af89fdb 100644
--- a/.github/workflows/testing.yml
+++ b/.github/workflows/testing.yml
@@ -24,7 +24,7 @@ jobs:
         path: /tmp/cicache
     - name: 'Prepare Docker Image'
       run: |
-        echo -e ' prefix=/ \n CC=clang \n CXX=clang++ \n CLANG_TIDY=clang-tidy ' > config-defaults.mk
+        echo -e ' prefix=/\n CC=clang \n CXX=clang++ \n CLANG_TIDY=clang-tidy ' > config-defaults.mk
         misc/cirun -u 1000 misc/version.sh
     - name: 'Build Dist Assets'
       run: |
@@ -54,11 +54,13 @@ jobs:
         path: /tmp/cicache
     - name: 'Prepare Docker Image'
       run: |
-        echo -e ' prefix=/ \n CC=clang \n CXX=clang++ \n CLANG_TIDY=clang-tidy ' > config-defaults.mk
+        # Test the most recent g++ via Arch
+        echo -e ' prefix=/\n' > config-defaults.mk
         misc/cirun -u 1000 misc/version.sh
     - name: 'Run X11 GUI Tests'
       run: |
-        $CIMAKE -j`nproc` all check
+        $CIMAKE GCC_COLORS="" -j`nproc` all
+        $CIMAKE -j`nproc` check
         $CIMAKE x11test-v
     # Artifact upload from x11test
     - uses: actions/upload-artifact@v3.1.3
@@ -82,7 +84,7 @@ jobs:
         path: /tmp/cicache
     - name: 'Prepare Docker Image'
       run: |
-        echo -e ' prefix=/ \n CC=clang \n CXX=clang++ \n CLANG_TIDY=clang-tidy ' > config-defaults.mk
+        echo -e ' prefix=/\n CC=clang \n CXX=clang++ \n CLANG_TIDY=clang-tidy ' > config-defaults.mk
         misc/cirun -u 1000 misc/version.sh
     - name: 'Make all check'
       run: |
diff --git a/Makefile.mk b/Makefile.mk
index fc73e891..5cefef53 100644
--- a/Makefile.mk
+++ b/Makefile.mk
@@ -84,6 +84,9 @@ pkgdir		 ?= $(pkgprefix)/anklang-$(version_major)-$(version_minor)
 pkgsharedir	 ?= $(pkgdir)/share
 .config.defaults += prefix bindir sharedir mandir docdir libdir pkgprefix pkgdir
 pkgdocdir	 ?= $(pkgdir)/doc
+ifneq (1,$(words [$(prefix)])) # guard against `prefix := / / ` etc which will confuse `rm -rf`
+$(error Variable `prefix` must expand to a single directory name, current value: `prefix:=$(prefix)`)
+endif
 
 # == Target Collections ==
 ALL_TARGETS	::=
diff --git a/external/websocketpp b/external/websocketpp
index 56123c87..b9aeec6e 160000
--- a/external/websocketpp
+++ b/external/websocketpp
@@ -1 +1 @@
-Subproject commit 56123c87598f8b1dd471be83ca841ceae07f95ba
+Subproject commit b9aeec6eaf3d5610503439b4fae3581d9aff08e8
diff --git a/misc/Dockerfile.arch b/misc/Dockerfile.arch
index dd32bfbb..1ea7a9f3 100644
--- a/misc/Dockerfile.arch
+++ b/misc/Dockerfile.arch
@@ -24,11 +24,14 @@ RUN pacman -Sy --noconfirm archlinux-keyring && pacman-key --init && pacman-key
 # Castxml is not provided by pacman
 RUN cd /tmp && git clone https://github.com/CastXML/CastXML.git && cd CastXML && cmake . && make -j && sudo make install
 
+# Provide a fast JS package manager
+RUN npm install -g pnpm@latest
+
 # Become non-root
 RUN groupadd --gid 1000 builder \
   && useradd --uid 1000 --gid 1000 --create-home --shell /bin/bash builder \
   && echo "builder ALL=(ALL) NOPASSWD:ALL" > /etc/sudoers.d/builder
 USER builder
 
-# docker build -f misc/Dockerfile.arch -t anklang-arch misc/
-# docker run -ti --rm -v $PWD:/anklang -w /anklang anklang-arch
+# docker build -t arch:latest -f misc/Dockerfile.arch misc
+# docker run -i -t --rm -v $PWD:/anklang -w /anklang arch:latest
diff --git a/misc/Dockerfile.focal b/misc/Dockerfile.focal
index 5826d769..d72c6471 100644
--- a/misc/Dockerfile.focal
+++ b/misc/Dockerfile.focal
@@ -80,6 +80,9 @@ RUN : \
   && apt-get install -y nodejs \
   && apt-get clean
 
+# Provide a fast JS package manager
+RUN npm install -g bun@latest
+
 # Build stripped down Fluidsynth version without drivers (not needed atm)
 RUN exit 0 && \
   mkdir -p /tmp/fluid/build && cd /tmp/fluid/ && \
diff --git a/misc/cirun b/misc/cirun
index 6076814b..cc074575 100755
--- a/misc/cirun
+++ b/misc/cirun
@@ -46,12 +46,12 @@ echo -n `git rev-parse HEAD`"    " && git describe 2>/dev/null || git describe -
 
 # Build Docker image
 # docker build -t $CITAG -f misc/Dockerfile.CIDIST misc
-docker buildx >/dev/null 2>&1 || die "missing docker-buildx-plugin"
 (
   DOCKER_IMAGES=$(docker images --format "|{{.ID}}|{{.Repository}}:{{.Tag}}|") # buffer image list to avoid SIGPIPE
   test -n "${CITAG:-}" || die "missing docker image, CITAG is unset"
   grep -q "|$CITAG:latest|" <<< "$DOCKER_IMAGES" || {
     echo "$SCRIPTNAME: need to build docker image: $CITAG:latest"
+    docker buildx >/dev/null 2>&1 || die "missing docker-buildx-plugin"
     # determine Dockerfile
     DOCKERFILE="./Dockerfile.$CITAG"
     test -r "$DOCKERFILE" ||