diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4bee1cd..0e70682 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -6,6 +6,10 @@ on:
   pull_request:
   workflow_dispatch:
 
+concurrency: # Cancel stale PR builds (but not push builds)
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}
+  cancel-in-progress: true
+
 jobs:
   build:
     strategy:
@@ -30,7 +34,7 @@ jobs:
             shell: bash
           - target:
               os: macos
-            builder: macos-10.15
+            builder: macos-12
             shell: bash
           - target:
               os: windows
@@ -43,17 +47,12 @@ jobs:
 
     name: '${{ matrix.target.os }}-${{ matrix.target.cpu }} (Nim ${{ matrix.branch }})'
     runs-on: ${{ matrix.builder }}
-    continue-on-error: ${{ matrix.branch == 'version-1-6' || matrix.branch == 'devel' }}
+    continue-on-error: ${{ matrix.branch == 'devel' }}
     steps:
-      - name: Cancel Previous Runs
-        uses: styfle/cancel-workflow-action@0.5.0
-        with:
-          access_token: ${{ github.token }}
-
       - name: Checkout
         uses: actions/checkout@v2
 
-      - name: Install dependencies (Linux i386)
+      - name: Install build dependencies (Linux i386)
         if: runner.os == 'Linux' && matrix.target.cpu == 'i386'
         run: |
           sudo dpkg --add-architecture i386
@@ -99,23 +98,23 @@ jobs:
         id: windows-dlls-cache
         uses: actions/cache@v2
         with:
-          path: external/dlls
-          key: 'dlls'
+          path: external/dlls-${{ matrix.target.cpu }}
+          key: 'dlls-${{ matrix.target.cpu }}'
 
-      - name: Install DLL dependencies (Windows)
+      - name: Install DLLs dependencies (Windows)
         if: >
           steps.windows-dlls-cache.outputs.cache-hit != 'true' &&
           runner.os == 'Windows'
         run: |
-          mkdir external
+          mkdir -p external
           curl -L "https://nim-lang.org/download/windeps.zip" -o external/windeps.zip
-          7z x external/windeps.zip -oexternal/dlls
+          7z x -y external/windeps.zip -oexternal/dlls-${{ matrix.target.cpu }}
 
       - name: Path to cached dependencies (Windows)
         if: >
           runner.os == 'Windows'
         run: |
-          echo '${{ github.workspace }}'"/external/dlls" >> $GITHUB_PATH
+          echo "${{ github.workspace }}/external/dlls-${{ matrix.target.cpu }}" >> $GITHUB_PATH
 
       - name: Derive environment variables
         run: |
@@ -154,5 +153,8 @@ jobs:
 
       - name: Run tests
         run: |
-          env TEST_LANG=c nimble test
-          env TEST_LANG=cpp nimble test
+          nim --version
+          nimble --version
+          nimble install -y --depsOnly
+          env NIMLANG=c nimble test
+          env NIMLANG=cpp nimble test
diff --git a/taskpools.nimble b/taskpools.nimble
index 2aef402..1328ce8 100644
--- a/taskpools.nimble
+++ b/taskpools.nimble
@@ -1,49 +1,50 @@
 mode = ScriptMode.Verbose
 
 packageName   = "taskpools"
-version       = "0.0.3"
+version       = "0.0.4"
 author        = "Status Research & Development GmbH"
 description   = "lightweight, energy-efficient, easily auditable threadpool"
 license       = "MIT"
+skipDirs      = @["tests"]
 
-### Dependencies
 requires "nim >= 1.2.12"
 
-proc test(flags, path: string) =
-  if not dirExists "build":
-    mkDir "build"
-  # Note: we compile in release mode. This still have stacktraces
-  #       but is much faster than -d:debug
+let nimc = getEnv("NIMC", "nim") # Which nim compiler to use
+let lang = getEnv("NIMLANG", "c") # Which backend (c/cpp/js)
+let flags = getEnv("NIMFLAGS", "") # Extra flags for the compiler
+let verbose = getEnv("V", "") notin ["", "0"]
 
-  # Compilation language is controlled by TEST_LANG
-  let lang = getEnv("TEST_LANG", "c")
+let styleCheckStyle = if (NimMajor, NimMinor) < (1, 6): "hint" else: "error"
+let cfg =
+  " --styleCheck:usages --styleCheck:" & styleCheckStyle &
+  (if verbose: "" else: " --verbosity:0 --hints:off") &
+  " --skipParentCfg --skipUserCfg --outdir:build --nimcache:build/nimcache -f" &
+  " --stacktrace:on --linetrace:on" &
+  " --threads:on"
 
-  echo "\n========================================================================================"
-  echo "Running [ ", lang, " ", flags, " ] ", path
-  echo "========================================================================================"
-  exec "nim " & lang & " -d:TP_Asserts " & getEnv("NIMFLAGS") & " " & flags &
-    " --verbosity:0 --warnings:off --threads:on -d:release" &
-    " --stacktrace:on --linetrace:on --outdir:build -r --skipParentCfg --skipUserCfg" &
-    " --styleCheck:usages --styleCheck:hint" &
-    " --hint[XDeclaredButNotUsed]:off --hint[Processing]:off " & path
+proc build(args, path: string) =
+  exec nimc & " " & lang & " " & cfg & " " & flags & " " & args & " " & path
+
+proc run(args, path: string) =
+  build args & " -r", path
 
 task test, "Run Taskpools tests":
   # Internal data structures
-  test "", "taskpools/channels_spsc_single.nim"
-  test "", "taskpools/sparsesets.nim"
+  run "", "taskpools/channels_spsc_single.nim"
+  run "", "taskpools/sparsesets.nim"
 
   # Examples
-  test "", "examples/e01_simple_tasks.nim"
-  test "", "examples/e02_parallel_pi.nim"
+  run "", "examples/e01_simple_tasks.nim"
+  run "", "examples/e02_parallel_pi.nim"
 
   # Benchmarks
-  test "", "benchmarks/dfs/taskpool_dfs.nim"
-  test "", "benchmarks/heat/taskpool_heat.nim"
-  test "", "benchmarks/nqueens/taskpool_nqueens.nim"
+  run "", "benchmarks/dfs/taskpool_dfs.nim"
+  run "", "benchmarks/heat/taskpool_heat.nim"
+  run "", "benchmarks/nqueens/taskpool_nqueens.nim"
 
   when not defined(windows):
-    test "", "benchmarks/single_task_producer/taskpool_spc.nim"
-    test "", "benchmarks/bouncing_producer_consumer/taskpool_bpc.nim"
+    run "", "benchmarks/single_task_producer/taskpool_spc.nim"
+    run "", "benchmarks/bouncing_producer_consumer/taskpool_bpc.nim"
 
   # TODO - generics in macro issue
-  # test "", "benchmarks/matmul_cache_oblivious/taskpool_matmul_co.nim"
+  # run "", "benchmarks/matmul_cache_oblivious/taskpool_matmul_co.nim"
diff --git a/taskpools/chase_lev_deques.nim b/taskpools/chase_lev_deques.nim
index 10897d4..f0e3d52 100644
--- a/taskpools/chase_lev_deques.nim
+++ b/taskpools/chase_lev_deques.nim
@@ -37,7 +37,7 @@
 
 import
   system/ansi_c,
-  std/[locks, typetraits, atomics],
+  std/atomics,
   ./instrumentation/[contracts, loggers],
   ./primitives/allocs
 
diff --git a/taskpools/flowvars.nim b/taskpools/flowvars.nim
index 1e55ad0..ec2eef2 100644
--- a/taskpools/flowvars.nim
+++ b/taskpools/flowvars.nim
@@ -6,7 +6,6 @@
 # at your option. This file may not be copied, modified, or distributed except according to those terms.
 
 import
-  system/ansi_c,
   std/os,
   ./instrumentation/contracts,
   ./channels_spsc_single,