diff --git a/docs/roadmap/implementation.md b/docs/roadmap/implementation.md
index db5c08c..cd9de0e 100644
--- a/docs/roadmap/implementation.md
+++ b/docs/roadmap/implementation.md
@@ -145,7 +145,7 @@ During every stage:
 
 ## Stage 1 — Shared Release Library And Asset Builder
 
-**Status: Pending**
+**Status: Completed**
 
 ### Goal
 
diff --git a/internal/releasecheck/assets_test.go b/internal/releasecheck/assets_test.go
new file mode 100644
index 0000000..8be989c
--- /dev/null
+++ b/internal/releasecheck/assets_test.go
@@ -0,0 +1,167 @@
+package releasecheck
+
+import (
+	"bytes"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"sort"
+	"strings"
+	"testing"
+)
+
+func TestAssetBuilderRejectsUnsafeDestinations(t *testing.T) {
+	repoRoot := releaseCheckRepoRoot(t)
+	builder := filepath.Join(repoRoot, "scripts", "build-release-assets.sh")
+	nonempty := t.TempDir()
+	if err := os.WriteFile(filepath.Join(nonempty, "existing"), []byte("x"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	notDirectory := filepath.Join(t.TempDir(), "not-a-directory")
+	if err := os.WriteFile(notDirectory, []byte("x"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	linkTarget := t.TempDir()
+	symlink := filepath.Join(t.TempDir(), "linked-output")
+	if err := os.Symlink(linkTarget, symlink); err != nil {
+		t.Fatal(err)
+	}
+
+	for _, args := range [][]string{
+		nil,
+		{"v1.2", t.TempDir()},
+		{"1.2.3", t.TempDir()},
+		{"v01.2.3", t.TempDir()},
+		{"v1.02.3", t.TempDir()},
+		{"v1.2.03", t.TempDir()},
+		{"v1.2.3-rc.1", t.TempDir()},
+		{"v1.2.3+build", t.TempDir()},
+		{"v1.2.3", "relative-output"},
+		{"v1.2.3", "/"},
+		{"v1.2.3", repoRoot},
+		{"v1.2.3", nonempty},
+		{"v1.2.3", notDirectory},
+		{"v1.2.3", symlink},
+	} {
+		command := exec.Command("sh", append([]string{builder}, args...)...)
+		command.Dir = t.TempDir()
+		output, err := command.CombinedOutput()
+		if err == nil {
+			t.Fatalf("asset builder %q succeeded", args)
+		}
+		if !strings.Contains(string(output), "build-release-assets:") {
+			t.Fatalf("asset builder %q output = %q", args, output)
+		}
+	}
+}
+
+func TestAssetBuilderBuildsNamedAssetsAndChecksEmbeddedVersion(t *testing.T) {
+	repoRoot := releaseCheckRepoRoot(t)
+	builder := filepath.Join(repoRoot, "scripts", "build-release-assets.sh")
+	binDir := t.TempDir()
+	writeFakeGo(t, filepath.Join(binDir, "go"))
+	outputDir := filepath.Join(t.TempDir(), "assets")
+
+	command := exec.Command("sh", builder, "v1.2.3", outputDir)
+	command.Dir = t.TempDir()
+	command.Env = append(os.Environ(), "PATH="+binDir+string(os.PathListSeparator)+os.Getenv("PATH"))
+	output, err := command.CombinedOutput()
+	if err != nil {
+		t.Fatalf("asset builder error = %v\n%s", err, output)
+	}
+	entries, err := os.ReadDir(outputDir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := make([]string, 0, len(entries))
+	for _, entry := range entries {
+		got = append(got, entry.Name())
+	}
+	sort.Strings(got)
+	want := []string{
+		"narratio-v1.2.3-darwin-amd64",
+		"narratio-v1.2.3-darwin-arm64",
+		"narratio-v1.2.3-linux-amd64",
+		"narratio-v1.2.3-linux-arm64",
+		"narratio-v1.2.3-windows-amd64.exe",
+		"narratio-v1.2.3-windows-arm64.exe",
+	}
+	if !slicesEqual(got, want) {
+		t.Fatalf("asset names = %#v, want %#v", got, want)
+	}
+	version := exec.Command(filepath.Join(outputDir, "narratio-v1.2.3-linux-amd64"), "version")
+	var versionOutput bytes.Buffer
+	version.Stdout = &versionOutput
+	if err := version.Run(); err != nil {
+		t.Fatal(err)
+	}
+	if got := versionOutput.String(); got != "narratio v1.2.3\n" {
+		t.Fatalf("embedded version output = %q", got)
+	}
+}
+
+func releaseCheckRepoRoot(t *testing.T) string {
+	t.Helper()
+	_, file, _, ok := runtime.Caller(0)
+	if !ok {
+		t.Fatal("runtime.Caller() failed")
+	}
+	return filepath.Clean(filepath.Join(filepath.Dir(file), "..", ".."))
+}
+
+func writeFakeGo(t *testing.T, path string) {
+	t.Helper()
+	const fake = `#!/bin/sh
+set -eu
+
+if [ "$1" = env ]; then
+  case $2 in
+    GOOS) printf '%s\n' linux ;;
+    GOARCH) printf '%s\n' amd64 ;;
+    *) exit 1 ;;
+  esac
+  exit 0
+fi
+
+output=
+version=
+while [ "$#" -gt 0 ]; do
+  case $1 in
+    -o)
+      shift
+      output=$1
+      ;;
+    -ldflags)
+      shift
+      case $1 in
+        *gitea.maximumdirect.net/eric/narratio/internal/buildinfo.Version=*)
+          version=${1##*=}
+          ;;
+      esac
+      ;;
+  esac
+  shift
+done
+
+[ -n "$output" ]
+[ -n "$version" ]
+printf '#!/bin/sh\nprintf "narratio %%s\\n" "%s"\n' "$version" > "$output"
+chmod +x "$output"
+`
+	if err := os.WriteFile(path, []byte(fake), 0o755); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func slicesEqual(left, right []string) bool {
+	if len(left) != len(right) {
+		return false
+	}
+	for index := range left {
+		if left[index] != right[index] {
+			return false
+		}
+	}
+	return true
+}
diff --git a/scripts/build-release-assets.sh b/scripts/build-release-assets.sh
new file mode 100755
index 0000000..d55476f
--- /dev/null
+++ b/scripts/build-release-assets.sh
@@ -0,0 +1,93 @@
+#!/bin/sh
+set -eu
+
+script_dir=$(CDPATH= cd "$(dirname "$0")" && pwd -P)
+# shellcheck source=release-lib.sh
+. "$script_dir/release-lib.sh"
+
+tool_name=build-release-assets
+
+if [ "$#" -ne 2 ]; then
+	narratio_release_fail "$tool_name" 'usage: scripts/build-release-assets.sh VERSION OUTPUT_DIR'
+fi
+
+release_version=$1
+output_dir=$2
+if ! narratio_release_validate_version "$release_version"; then
+	narratio_release_fail "$tool_name" "invalid stable version: $release_version"
+fi
+
+case $output_dir in
+	/*) ;;
+	*) narratio_release_fail "$tool_name" "output directory must be absolute: $output_dir" ;;
+esac
+
+repo_root=$(narratio_release_repo_root "$0") || narratio_release_fail "$tool_name" 'cannot locate repository root'
+if ! cd "$repo_root"; then
+	narratio_release_fail "$tool_name" "cannot enter repository root: $repo_root"
+fi
+if [ "$output_dir" = / ]; then
+	narratio_release_fail "$tool_name" 'output directory must not be /'
+fi
+if [ -L "$output_dir" ]; then
+	narratio_release_fail "$tool_name" "output directory must not be a symlink: $output_dir"
+fi
+if [ -e "$output_dir" ]; then
+	if [ ! -d "$output_dir" ]; then
+		narratio_release_fail "$tool_name" "output path must be a directory: $output_dir"
+	fi
+	resolved_output_dir=$(CDPATH= cd "$output_dir" && pwd -P) || narratio_release_fail "$tool_name" "cannot access output directory: $output_dir"
+	if [ "$resolved_output_dir" = "$repo_root" ]; then
+		narratio_release_fail "$tool_name" 'output directory must not be the repository root'
+	fi
+	for existing_entry in "$output_dir"/* "$output_dir"/.[!.]* "$output_dir"/..?*; do
+		if [ -e "$existing_entry" ] || [ -L "$existing_entry" ]; then
+			narratio_release_fail "$tool_name" "output directory must be empty: $output_dir"
+		fi
+	done
+else
+	if ! mkdir "$output_dir"; then
+		narratio_release_fail "$tool_name" "cannot create output directory: $output_dir"
+	fi
+fi
+
+temporary_smoke_binary=
+cleanup_temporary_smoke_binary() {
+	if [ -n "$temporary_smoke_binary" ]; then
+		rm -f "$temporary_smoke_binary"
+	fi
+}
+trap cleanup_temporary_smoke_binary 0 HUP INT TERM
+
+build_flags="-s -w -X gitea.maximumdirect.net/eric/narratio/internal/buildinfo.Version=$release_version"
+host_os=$(go env GOOS)
+host_arch=$(go env GOARCH)
+host_asset=
+
+for target in linux/amd64 linux/arm64 darwin/amd64 darwin/arm64 windows/amd64 windows/arm64; do
+	target_os=${target%%/*}
+	target_arch=${target#*/}
+	suffix=
+	if [ "$target_os" = windows ]; then
+		suffix=.exe
+	fi
+	asset_path="$output_dir/narratio-$release_version-$target_os-$target_arch$suffix"
+	CGO_ENABLED=0 GOOS="$target_os" GOARCH="$target_arch" go build -trimpath -ldflags "$build_flags" -o "$asset_path" ./cmd/narratio
+	if [ "$target_os" = "$host_os" ] && [ "$target_arch" = "$host_arch" ]; then
+		host_asset=$asset_path
+	fi
+done
+
+if [ -z "$host_asset" ]; then
+	temporary_smoke_binary="$output_dir/.narratio-release-version-smoke"
+	CGO_ENABLED=0 go build -trimpath -ldflags "$build_flags" -o "$temporary_smoke_binary" ./cmd/narratio
+	host_asset=$temporary_smoke_binary
+fi
+
+reported_version=$("$host_asset" version)
+if [ "$reported_version" != "narratio $release_version" ]; then
+	narratio_release_fail "$tool_name" "release binary reported unexpected version: $reported_version"
+fi
+
+cleanup_temporary_smoke_binary
+temporary_smoke_binary=
diff --git a/scripts/release-lib.sh b/scripts/release-lib.sh
new file mode 100755
index 0000000..0501c80
--- /dev/null
+++ b/scripts/release-lib.sh
@@ -0,0 +1,46 @@
+#!/bin/sh
+
+# Shared helpers for Narratio's checked-in release scripts. This file is
+# intentionally source-only and has no effect when loaded.
+
+narratio_release_fail() {
+	tool_name=$1
+	shift
+	printf '%s: %s\n' "$tool_name" "$*" >&2
+	exit 1
+}
+
+narratio_release_validate_version() {
+	version=$1
+	case $version in
+		v*.*.*) ;;
+		*) return 1 ;;
+	esac
+	components=${version#v}
+	if [ "$components" = "$version" ]; then
+		return 1
+	fi
+
+	previous_ifs=$IFS
+	IFS=.
+	set -- $components
+	IFS=$previous_ifs
+	if [ "$#" -ne 3 ]; then
+		return 1
+	fi
+	for component in "$@"; do
+		case $component in
+			0 | [1-9]*) ;;
+			*) return 1 ;;
+		esac
+		case $component in
+			*[!0-9]*) return 1 ;;
+		esac
+	done
+}
+
+narratio_release_repo_root() (
+	script_path=$1
+	script_dir=$(CDPATH= cd "$(dirname "$script_path")" && pwd -P) || return 1
+	CDPATH= cd "$script_dir/.." && pwd -P
+)