perf: cache startup package metadata

src/cli/startup-metadata.ts

@@ -3,6 +3,7 @@ import path from "node:path";
 import { fileURLToPath } from "node:url";
 
 const STARTUP_METADATA_FILE = "cli-startup-metadata.json";
+const startupMetadataByPath = new Map<string, Record<string, unknown> | null>();
 
 function resolveStartupMetadataPathCandidates(moduleUrl: string): string[] {
   const moduleDir = path.dirname(fileURLToPath(moduleUrl));
@@ -14,10 +15,20 @@ function resolveStartupMetadataPathCandidates(moduleUrl: string): string[] {
 
 export function readCliStartupMetadata(moduleUrl: string): Record<string, unknown> | null {
   for (const metadataPath of resolveStartupMetadataPathCandidates(moduleUrl)) {
+    const cached = startupMetadataByPath.get(metadataPath);
+    if (cached !== undefined) {
+      if (cached) {
+        return cached;
+      }
+      continue;
+    }
     try {
-      return JSON.parse(fs.readFileSync(metadataPath, "utf8")) as Record<string, unknown>;
+      const parsed = JSON.parse(fs.readFileSync(metadataPath, "utf8")) as Record<string, unknown>;
+      startupMetadataByPath.set(metadataPath, parsed);
+      return parsed;
     } catch {
       // Try the next bundled/source layout before falling back to dynamic startup work.
+      startupMetadataByPath.set(metadataPath, null);
     }
   }
   return null;
@@ -25,4 +36,7 @@ export function readCliStartupMetadata(moduleUrl: string): Record<string, unknow
 
 export const __testing = {
   resolveStartupMetadataPathCandidates,
+  clearStartupMetadataCache(): void {
+    startupMetadataByPath.clear();
+  },
 };