diff --git a/CLAUDE.md b/CLAUDE.md
index 5968670..e3a5fa9 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -94,8 +94,8 @@ This ensures consistent tooling versions across the team without system-wide ins
 
 ## Platform Requirements
 
-Linux x86_64 only (currently). Requires:
-- Modern libc for Go binaries
+Linux or macOS on x86_64. Requires:
+- Modern libc for Go binaries (Linux)
 - docker compose (for full stack)
 - fd, shellcheck, shfmt (for development)
 
diff --git a/README.md b/README.md
index 5b94767..ce4ffce 100644
--- a/README.md
+++ b/README.md
@@ -44,9 +44,8 @@ Different situations require different getting started docs.
 
 ## Requirements
 
-To run diachron, you currently need to have a Linux box running x86_64 with a
-new enough libc to run golang binaries.  Support for other platforms will come
-eventually.
+To run diachron, you need Linux or macOS on x86_64.  Linux requires a new
+enough libc to run golang binaries.
 
 To run a more complete system, you also need to have docker compose installed.
 
diff --git a/framework/platform b/framework/platform
new file mode 100644
index 0000000..35f429a
--- /dev/null
+++ b/framework/platform
@@ -0,0 +1,26 @@
+# shellcheck shell=bash
+
+# Detect platform (OS and architecture)
+
+os=$(uname -s | tr '[:upper:]' '[:lower:]')
+arch=$(uname -m)
+
+case "$os" in
+    linux) platform_os=linux ;;
+    darwin) platform_os=darwin ;;
+    *) echo "Unsupported OS: $os" >&2; exit 1 ;;
+esac
+
+case "$arch" in
+    x86_64) platform_arch=x86_64 ;;
+    *) echo "Unsupported architecture: $arch" >&2; exit 1 ;;
+esac
+
+platform="${platform_os}_${platform_arch}"
+
+# Platform-specific checksum command
+if [ "$platform_os" = "darwin" ]; then
+    sha256_check() { shasum -a 256 -c -; }
+else
+    sha256_check() { sha256sum -c -; }
+fi
diff --git a/framework/shims/node.common b/framework/shims/node.common
index 3745766..ef55172 100644
--- a/framework/shims/node.common
+++ b/framework/shims/node.common
@@ -7,6 +7,15 @@ project_root="$node_common_DIR/../.."
 # shellcheck source=../versions
 source "$node_common_DIR"/../versions
 
+# shellcheck source=../platform
+source "$node_common_DIR"/../platform
+
+# Get platform-specific node directory
+nodejs_dirname_var="nodejs_dirname_${platform}"
+nodejs_dirname="${!nodejs_dirname_var}"
+nodejs_dist_dir="framework/binaries/$nodejs_dirname"
+nodejs_bin_dir="$nodejs_dist_dir/bin"
+
 nodejs_binary_dir="$project_root/$nodejs_bin_dir"
 
 # This might be too restrictive.  Or not restrictive enough.
diff --git a/framework/versions b/framework/versions
index de9fbd4..4fd1a9d 100644
--- a/framework/versions
+++ b/framework/versions
@@ -2,18 +2,25 @@
 
 # This file belongs to the framework.  You are not expected to modify it.
 
+nodejs_version=v24.12.0
+
 # https://nodejs.org/dist
 nodejs_binary_linux_x86_64=https://nodejs.org/dist/v24.12.0/node-v24.12.0-linux-x64.tar.xz
 nodejs_checksum_linux_x86_64=bdebee276e58d0ef5448f3d5ac12c67daa963dd5e0a9bb621a53d1cefbc852fd
-nodejs_dist_dir=framework/binaries/node-v22.15.1-linux-x64
-nodejs_bin_dir="$nodejs_dist_dir/bin"
+nodejs_dirname_linux_x86_64=node-v24.12.0-linux-x64
+
+nodejs_binary_darwin_x86_64=https://nodejs.org/dist/v24.12.0/node-v24.12.0-darwin-x64.tar.xz
+nodejs_checksum_darwin_x86_64=1e4d54f706e0a3613d6415ffe2ccdfd4095d3483971dbbaa4ff909fac5fc211c
+nodejs_dirname_darwin_x86_64=node-v24.12.0-darwin-x64
 
 caddy_binary_linux_x86_64=fixme
 caddy_checksum_linux_x86_64=fixmetoo
 
 # https://github.com/pnpm/pnpm/releases
 pnpm_binary_linux_x86_64=https://github.com/pnpm/pnpm/releases/download/v10.28.0/pnpm-linux-x64
-pnpm_checksum_linux_x86_64=sha256:348e863d17a62411a65f900e8d91395acabae9e9237653ccc3c36cb385965f28
+pnpm_checksum_linux_x86_64=348e863d17a62411a65f900e8d91395acabae9e9237653ccc3c36cb385965f28
 
+pnpm_binary_darwin_x86_64=https://github.com/pnpm/pnpm/releases/download/v10.28.0/pnpm-macos-x64
+pnpm_checksum_darwin_x86_64=99431e91d721169c2050d5e46abefc6f0d23c49e635a5964dcb573d9fe89975a
 
 golangci_lint=v2.7.2-alpine
\ No newline at end of file
diff --git a/sync.sh b/sync.sh
index 40d102e..4a750e9 100755
--- a/sync.sh
+++ b/sync.sh
@@ -9,6 +9,26 @@ DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 # shellcheck source=framework/versions
 source "$DIR/framework/versions"
 
+# shellcheck source=framework/platform
+source "$DIR/framework/platform"
+
+# Get platform-specific variables
+nodejs_binary_var="nodejs_binary_${platform}"
+nodejs_checksum_var="nodejs_checksum_${platform}"
+nodejs_dirname_var="nodejs_dirname_${platform}"
+nodejs_binary="${!nodejs_binary_var}"
+nodejs_checksum="${!nodejs_checksum_var}"
+nodejs_dirname="${!nodejs_dirname_var}"
+
+pnpm_binary_var="pnpm_binary_${platform}"
+pnpm_checksum_var="pnpm_checksum_${platform}"
+pnpm_binary_url="${!pnpm_binary_var}"
+pnpm_checksum="${!pnpm_checksum_var}"
+
+# Set up paths for shims to use
+nodejs_dist_dir="framework/binaries/$nodejs_dirname"
+nodejs_bin_dir="$nodejs_dist_dir/bin"
+
 # Ensure correct node version is installed
 node_installed_checksum_file="$DIR/framework/binaries/.node.checksum"
 node_installed_checksum=""
@@ -16,19 +36,19 @@ if [ -f "$node_installed_checksum_file" ]; then
     node_installed_checksum=$(cat "$node_installed_checksum_file")
 fi
 
-if [ "$node_installed_checksum" != "$nodejs_checksum_linux_x86_64" ]; then
-    echo "Downloading Node.js..."
+if [ "$node_installed_checksum" != "$nodejs_checksum" ]; then
+    echo "Downloading Node.js for $platform..."
     node_archive="$DIR/framework/downloads/node.tar.xz"
-    curl -fsSL "$nodejs_binary_linux_x86_64" -o "$node_archive"
+    curl -fsSL "$nodejs_binary" -o "$node_archive"
 
     echo "Verifying checksum..."
-    echo "$nodejs_checksum_linux_x86_64  $node_archive" | sha256sum -c -
+    echo "$nodejs_checksum  $node_archive" | sha256_check
 
     echo "Extracting Node.js..."
     tar -xf "$node_archive" -C "$DIR/framework/binaries"
     rm "$node_archive"
 
-    echo "$nodejs_checksum_linux_x86_64" >"$node_installed_checksum_file"
+    echo "$nodejs_checksum" >"$node_installed_checksum_file"
 fi
 
 # Ensure correct pnpm version is installed
@@ -39,15 +59,12 @@ if [ -f "$pnpm_installed_checksum_file" ]; then
     pnpm_installed_checksum=$(cat "$pnpm_installed_checksum_file")
 fi
 
-# pnpm checksum includes "sha256:" prefix, strip it for sha256sum
-pnpm_checksum="${pnpm_checksum_linux_x86_64#sha256:}"
-
 if [ "$pnpm_installed_checksum" != "$pnpm_checksum" ]; then
-    echo "Downloading pnpm..."
-    curl -fsSL "$pnpm_binary_linux_x86_64" -o "$pnpm_binary"
+    echo "Downloading pnpm for $platform..."
+    curl -fsSL "$pnpm_binary_url" -o "$pnpm_binary"
 
     echo "Verifying checksum..."
-    echo "$pnpm_checksum  $pnpm_binary" | sha256sum -c -
+    echo "$pnpm_checksum  $pnpm_binary" | sha256_check
 
     chmod +x "$pnpm_binary"