diff --git a/.github/workflows/dist.yml b/.github/workflows/dist.yml
new file mode 100644
index 00000000..79868957
--- /dev/null
+++ b/.github/workflows/dist.yml
@@ -0,0 +1,51 @@
+name: Dist
+
+on:
+  push:
+    branches: [ release, next ]
+  pull_request:
+    branches: [ release, next ]
+
+jobs:
+  linux-dist:
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - run: tool/cross --target-x86_64-unknown-linux-musl --target-x86_64-unknown-linux-gnu --target-x86_64-apple-darwin --target-armv7-unknown-linux-musleabihf --target-armv7-unknown-linux-gnueabihf --target-aarch64-unknown-linux-musl --target-aarch64-unknown-linux-gnu
+      - uses: actions/upload-artifact@v4
+        with:
+          name: x86_64-unknown-linux-musl
+          path: out/x86_64-unknown-linux-musl
+      - uses: actions/upload-artifact@v4
+        with:
+          name: x86_64-unknown-linux-gnu
+          path: out/x86_64-unknown-linux-gnu
+      - uses: actions/upload-artifact@v4
+        with:
+          name: armv7-unknown-linux-musleabihf
+          path: out/armv7-unknown-linux-musleabihf
+      - uses: actions/upload-artifact@v4
+        with:
+          name: armv7-unknown-linux-gnueabihf
+          path: out/armv7-unknown-linux-gnueabihf
+      - uses: actions/upload-artifact@v4
+        with:
+          name: aarch64-unknown-linux-musl
+          path: out/aarch64-unknown-linux-musl
+      - uses: actions/upload-artifact@v4
+        with:
+          name: aarch64-unknown-linux-gnu
+          path: out/aarch64-unknown-linux-gnu
+  macos-dist:
+    runs-on: macos-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - run: tool/cross --target-aarch64-apple-darwin
+      - uses: actions/upload-artifact@v4
+        with:
+          name: aarch64-apple-darwin
+          path: out/aarch64-apple-darwin
diff --git a/tool/cross b/tool/cross
new file mode 100755
index 00000000..06232738
--- /dev/null
+++ b/tool/cross
@@ -0,0 +1,110 @@
+#! /usr/bin/env bash
+set -e
+cd "$(dirname "$0")/.."
+version=$(cat .version)
+verbose=$(echo "$@" | grep -q -- --verbose && echo true || echo false)
+linux-cross() {
+  while read -r triple toolchain_name
+  do
+    crossc() {
+      (
+        img=wlinkmeyer/$(uname -m)-cross
+        [ "$verbose" = true ] && set -x
+        docker run -v "$PWD:/src" --rm "$img" \
+          "${toolchain_name}-g++" \
+            --sysroot "/etc/sysroots/$triple" \
+            -I "/usr/include/$toolchain_name" \
+            -I "/etc/sysroots/$triple/usr/include" \
+            -I "/etc/sysroots/$triple/usr/include/c++/12" \
+            -I "/etc/sysroots/$triple/usr/include/$toolchain_name" \
+            -I "/etc/sysroots/$triple/usr/include/$toolchain_name/c++/12" \
+            -I /src/watcher-c/include \
+            -I /src/include \
+            -std=c++17 \
+            -fno-exceptions \
+            -fno-rtti \
+            -fexpensive-optimizations \
+            -fno-omit-frame-pointer \
+            -fstrict-enums \
+            -fstrict-overflow \
+            -fstrict-aliasing \
+            -fstack-protector-strong \
+            -Os \
+            $@
+      )
+    }
+    build() {
+      if [ -e "$1" ]
+      then echo "[$triple] Exists: $1"
+      else
+        [ -d "$(dirname "$1")" ] || mkdir -p "$(dirname "$1")"
+        crossc -o "/src/$1" "${@:2}"
+        sudo chown "$USER" "$1"
+        echo -n "[$triple] Built: " ; file "$1"
+      fi
+    }
+    echo "$@" | grep -q -- --target && { echo "$@" | grep -q -- "--target-$triple" || continue ; }
+    echo "$@" | grep -q -- --clean && rm -rf "out/$triple"
+    build "out/$triple/libwatcher-c.so" -shared -fPIC /src/watcher-c/src/watcher-c.cpp
+    build "out/$triple/watcher" /src/src/wtr/watcher/main.cpp
+    build "out/$triple/tw" /src/src/wtr/tiny_watcher/main.cpp
+    [ -e "out/$triple/libwatcher-c.so.$version" ] || cp "out/$triple/libwatcher-c.so" "out/$triple/libwatcher-c.so.$version"
+    [ -f "out/$triple/watcher.hpp" ] || cp include/wtr/watcher.hpp "out/$triple/watcher.hpp"
+    python3 tool/shasum.py "out/$triple" mk
+  done <<EOF
+  aarch64-unknown-linux-gnu aarch64-linux-gnu
+  armv7-unknown-linux-gnueabihf arm-linux-gnueabihf
+  x86_64-unknown-linux-gnu x86_64-linux-gnu
+  aarch64-unknown-linux-musl aarch64-linux-musl
+  armv7-unknown-linux-musleabihf arm-linux-musleabihf
+  x86_64-unknown-linux-musl x86_64-linux-musl
+EOF
+}
+macos-cross() {
+  case "$(uname -m)" in
+    arm64) triple=aarch64-apple-darwin ;;
+    *) echo "Unsupported architecture: $(uname -m)" ; exit 1 ;;
+  esac
+  cc() {
+    (
+      [ "$verbose" = true ] && set -x
+      c++ \
+        -target "$triple" \
+        -I watcher-c/include \
+        -I include \
+        -std=c++17 \
+        -fno-exceptions \
+        -fno-rtti \
+        -fno-omit-frame-pointer \
+        -fstrict-enums \
+        -fstrict-overflow \
+        -fstrict-aliasing \
+        -fstack-protector-strong \
+        -Os \
+        -framework CoreFoundation \
+        -framework CoreServices \
+        $@
+    )
+  }
+  build() {
+    if [ -e "$1" ]
+    then echo "[$triple] Exists: $1"
+    else
+      [ -d "$(dirname "$1")" ] || mkdir -p "$(dirname "$1")"
+      cc -o "$1" "${@:2}"
+      echo -n "[$triple] Built: " ; file "$1"
+    fi
+  }
+  echo "$@" | grep -q -- --target && { echo "$@" | grep -q -- "--target-$triple" || return ; }
+  echo "$@" | grep -q -- --clean && rm -rf "out/$triple"
+  build "out/$triple/libwatcher-c.so" -shared -fPIC watcher-c/src/watcher-c.cpp
+  build "out/$triple/watcher" src/wtr/watcher/main.cpp
+  build "out/$triple/tw" src/wtr/tiny_watcher/main.cpp
+  [ -e "out/$triple/libwatcher-c.so.$version" ] || cp "out/$triple/libwatcher-c.so" "out/$triple/libwatcher-c.so.$version"
+  [ -f "out/$triple/watcher.hpp" ] || cp include/wtr/watcher.hpp "out/$triple/watcher.hpp"
+  python3 tool/shasum.py "out/$triple" mk
+}
+linux-cross "$@"
+if uname | grep -q Darwin
+then macos-cross "$@"
+fi
diff --git a/tool/shasum.py b/tool/shasum.py
index d8db4e92..505fdc59 100644
--- a/tool/shasum.py
+++ b/tool/shasum.py
@@ -23,14 +23,22 @@ def sha256sum_tree(path) -> dict:
     """
     Similar to mk_dot_sha256sums, but returns a mapping of
     file paths to their shasums, not file path.sha256sum to shasums.
+    Skips already existing .sha256sum files, and files that already
+    have .sha256sum counterparts.
     """
     if os.path.isfile(path):
-        return {path: sha256sum(path)}
-    tree = {}
-    for root, dirs, files in os.walk(path):
-        for p in dirs + files:
-            tree.update(sha256sum_tree(os.path.join(root, p)))
-    return tree
+        if path.endswith(".sha256sum"):
+            return {}
+        elif os.path.exists(f"{path}.sha256sum"):
+            return {}
+        else:
+            return {path: sha256sum(path)}
+    else:
+        tree = {}
+        for root, dirs, files in os.walk(path):
+            for p in dirs + files:
+                tree.update(sha256sum_tree(os.path.join(root, p)))
+        return tree
 
 
 def mk_dot_sha256sums(path) -> None: