feat: add lightweight application updates

server/update.ts

@@ -43,6 +43,16 @@ export type ReleaseMetadata = {
   assets: ReleaseAsset[];
 };
 
+const APPLICATION_UPDATE_ASSET = /\.update-([a-f0-9]{64})\.tar\.gz$/i;
+
+export function applicationUpdateRuntimeHash(assetName: string): string | undefined {
+  return APPLICATION_UPDATE_ASSET.exec(assetName)?.[1]?.toLowerCase();
+}
+
+export function runtimeHashFromLockfile(lockfile: string | Buffer): string {
+  return createHash("sha256").update(lockfile).digest("hex");
+}
+
 export type UrlPolicy = {
   /** Host names or HTTPS URLs which are allowed for requests. */
   allowedHosts?: readonly string[] | undefined;
@@ -379,7 +389,7 @@ export async function fetchReleaseBytes(
   }
 }
 
-export function selectReleaseAsset(release: ReleaseMetadata, platform = detectPlatform()): ReleaseAsset | undefined {
+export function selectReleaseAsset(release: ReleaseMetadata, platform = detectPlatform(), runtimeHash?: string): ReleaseAsset | undefined {
   const platformCandidates = release.assets.filter((asset) => {
     const name = asset.name.toLowerCase();
     return platform.aliases.filter((alias) => alias.toLowerCase().includes(platform.arch.toLowerCase())).some((alias) => name.includes(alias.toLowerCase()));
@@ -398,7 +408,15 @@ export function selectReleaseAsset(release: ReleaseMetadata, platform = detectPl
     const target = platform.target.toLowerCase();
     return Number(b.name.toLowerCase().includes(target)) - Number(a.name.toLowerCase().includes(target));
   });
-  return candidates[0];
+  const normalizedRuntimeHash = runtimeHash?.trim().toLowerCase();
+  if (normalizedRuntimeHash && /^[a-f0-9]{64}$/.test(normalizedRuntimeHash)) {
+    const applicationUpdate = candidates.find((asset) => applicationUpdateRuntimeHash(asset.name) === normalizedRuntimeHash);
+    if (applicationUpdate) return applicationUpdate;
+  }
+  // Older clients choose the first matching asset. Releases therefore keep
+  // the traditional full archive first, while current clients explicitly
+  // opt into a compatible application-only asset.
+  return candidates.find((asset) => !applicationUpdateRuntimeHash(asset.name));
 }
 
 export function sanitizeAssetName(value: string): string {