output metafile in dev

Author: nicktrn

packages/cli-v3/src/dev/devSession.ts

@@ -24,7 +24,8 @@ import { clearTmpDirs, EphemeralDirectory, getTmpDir } from "../utilities/tempDi
 import { startDevOutput } from "./devOutput.js";
 import { startWorkerRuntime } from "./devSupervisor.js";
 import { startMcpServer, stopMcpServer } from "./mcpServer.js";
-import { aiHelpLink } from "../utilities/cliOutput.js";
+import { writeJSONFile } from "../utilities/fileSystem.js";
+import { join } from "node:path";
 
 export type DevSessionOptions = {
   name: string | undefined;
@@ -105,6 +106,11 @@ export async function startDevSession({
 
     logger.debug("Created build manifest from bundle", { buildManifest });
 
+    await writeJSONFile(
+      join(workerDir?.path ?? destination.path, "metafile.json"),
+      bundle.metafile
+    );
+
     buildManifest = await notifyExtensionOnBuildComplete(buildContext, buildManifest);
 
     try {