diff --git a/parser/Makefile.toml b/parser/Makefile.toml
index 09d1a3b..403e892 100644
--- a/parser/Makefile.toml
+++ b/parser/Makefile.toml
@@ -39,12 +39,11 @@
     "cargo build -Z unstable-options --target ${TARGET} ${CARGO_OPTIONS} --artifact-dir target/cpp/${CONFIGURATION}",
     "cp target/cpp/${CONFIGURATION}/libmilo_parser.a ../dist/cpp/${CONFIGURATION}/libmilo.a",
     "cp target/headers/milo.h ../dist/cpp/${CONFIGURATION}",
-    "node ../scripts/postbuild-cpp.js	${CONFIGURATION}",
   ]
 
 [tasks."cpp:headers"]
-  command = "cbindgen"
-  args    = ["--quiet", "--output", "target/headers/milo.h"]
+  command = "bash"
+  args    = ["../scripts/postbuild-cpp.sh", "target/headers/milo.h"]
 
 [tasks."wasm:release"]
   env      = { CONFIGURATION = "release", CARGO_BUILD_OPTIONS = "-Z unstable-options -Z build-std=std,panic_abort", CARGO_OPTIONS = "--release", RUSTFLAGS_BASE = "-Z unstable-options -C panic=immediate-abort", WASMPACK_OPTIONS = "--release" }
diff --git a/scripts/postbuild-cpp.js b/scripts/postbuild-cpp.js
deleted file mode 100644
index 5e62d66..0000000
--- a/scripts/postbuild-cpp.js
+++ /dev/null
@@ -1,44 +0,0 @@
-import { readFile, writeFile } from 'node:fs/promises'
-import { getBuildInfo } from './buildinfo.js'
-
-async function prependVersionAndMethodMap () {
-  const headerMatcher = 'namespace milo_parser {'
-
-  const {
-    version: { raw, major, minor, patch, prerelease },
-    constants
-  } = await getBuildInfo()
-
-  // Create the method map, required by Node.js
-  const methods = Object.entries(constants)
-    .filter(p => p[0].startsWith('METHOD_'))
-    .map(([k, v]) => [k.replace('METHOD_', ''), v])
-
-  const updatedHeader = `
-#define MILO_VERSION "${raw}"
-#define MILO_VERSION_MAJOR ${major}
-#define MILO_VERSION_MINOR ${minor}
-#define MILO_VERSION_PATCH ${patch}
-#define MILO_VERSION_PRERELEASE "${prerelease}"
-
-#define MILO_METHODS_MAP(EACH) \\
-${methods.map(([v, i]) => `  EACH(${i}, ${v}, ${v}) \\`).join('\n')}
-
-namespace milo_parser {
-
-struct Parser;
-`.trim()
-
-  // Replace the header with the new code
-  return header.replace(/\n{3,}/g, '\n\n').replace(headerMatcher, updatedHeader)
-}
-
-// Read the file
-const headerPath = new URL(`../dist/cpp/${process.argv[2]}/milo.h`, import.meta.url)
-let header = await readFile(headerPath, 'utf-8')
-
-// Apply modifications
-header = await prependVersionAndMethodMap(header)
-
-// Write the updated file
-await writeFile(headerPath, header, 'utf-8')
diff --git a/scripts/postbuild-cpp.sh b/scripts/postbuild-cpp.sh
new file mode 100755
index 0000000..7d213a3
--- /dev/null
+++ b/scripts/postbuild-cpp.sh
@@ -0,0 +1,73 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+if [ $# -lt 1 ]; then
+  echo "Usage: postbuild-cpp.sh <output-header-path>" >&2
+  exit 1
+fi
+
+OUTPUT_FILE="$1"
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+ROOT_DIR="$(cd "$SCRIPT_DIR/.." && pwd)"
+
+mkdir -p "$(dirname "$OUTPUT_FILE")"
+TMPFILE=$(mktemp)
+trap 'rm -f "$TMPFILE"' EXIT
+
+# Run cbindgen from the parser directory so cargo finds its vendored config.
+# RUSTC_BOOTSTRAP=1 allows stable rustc to accept -Zunpretty=expanded, which
+# cbindgen needs for [parse.expand] to resolve proc-macro-generated types.
+(cd "$ROOT_DIR/parser" && RUSTC_BOOTSTRAP=1 cbindgen --quiet --output "$TMPFILE")
+
+# Extract version from parser/Cargo.toml
+VERSION=$(grep -m1 '^\s*version\s*=' "$ROOT_DIR/parser/Cargo.toml" | sed 's/.*"\([^"]*\)".*/\1/')
+if [ -z "$VERSION" ]; then
+  echo "Error: Cannot find parser version in parser/Cargo.toml" >&2
+  exit 1
+fi
+
+# Parse semver components
+MAJOR="${VERSION%%.*}"
+REST="${VERSION#*.}"
+MINOR="${REST%%.*}"
+REST="${REST#*.}"
+if [[ "$REST" == *-* ]]; then
+  PATCH="${REST%%-*}"
+  PRERELEASE="${REST#*-}"
+else
+  PATCH="$REST"
+  PRERELEASE=""
+fi
+
+# Read methods from YAML (skip comments, blank lines, and document start marker)
+mapfile -t METHODS < <(grep '^- ' "$ROOT_DIR/macros/constants/methods.yml" | sed 's/^- //' | tr '-' '_')
+
+# Build the replacement block
+REPLACEMENT=$(
+  printf '#define MILO_VERSION "%s"\n' "$VERSION"
+  printf '#define MILO_VERSION_MAJOR %s\n' "$MAJOR"
+  printf '#define MILO_VERSION_MINOR %s\n' "$MINOR"
+  printf '#define MILO_VERSION_PATCH %s\n' "$PATCH"
+  printf '#define MILO_VERSION_PRERELEASE "%s"\n' "$PRERELEASE"
+  printf '\n'
+  printf '#define MILO_METHODS_MAP(EACH) \\\\\n'
+  for i in "${!METHODS[@]}"; do
+    printf '  EACH(%d, %s, %s) \\\\\n' "$i" "${METHODS[$i]}" "${METHODS[$i]}"
+  done
+  printf '\n'
+  printf 'namespace milo_parser {\n'
+  printf '\n'
+  printf 'struct Parser;'
+)
+
+# Replace "namespace milo_parser {" with the preamble, then collapse 3+ blank lines to 1
+awk -v replacement="$REPLACEMENT" '
+  /^namespace milo_parser \{$/ && !replaced {
+    print replacement
+    replaced = 1
+    next
+  }
+  { print }
+' "$TMPFILE" \
+| awk '/^$/ { blank++; if (blank <= 1) print; next } { blank = 0; print }' \
+> "$OUTPUT_FILE"