companion: drive your real Chrome via an extension, not Playwright

extension/build.ts

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+/**
+ * Build script for the Zero Companion MV3 extension.
+ *
+ * Bundles `src/worker.ts` into a single classic service-worker script and emits
+ * a generated module the `zero` CLI bundles in — `zero/src/companion/
+ * extension-assets.ts` — mapping each extension filename to its contents. At
+ * runtime `bridge-engine.ts` writes those files (plus a per-run `bridge.json`)
+ * into `~/.zero/extension/`, which `zero browser connect` hands to Chrome via
+ * `--load-extension`. Embedding the built extension in the CLI bundle keeps it
+ * self-contained — no assumptions about the installer's on-disk layout.
+ *
+ * Run with `bun build.ts` (preferred) or via esbuild fallback.
+ */
+import { mkdir, readFile, writeFile } from "node:fs/promises";
+import { dirname, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const root = __dirname;
+const manifestPath = resolve(root, "manifest.json");
+const workerEntry = resolve(root, "src/worker.ts");
+const assetsOut = resolve(root, "..", "zero", "src", "companion", "extension-assets.ts");
+
+async function bundleWorker(): Promise<string> {
+  if (typeof (globalThis as any).Bun !== "undefined") {
+    const Bun = (globalThis as any).Bun;
+    const out = await Bun.build({
+      entrypoints: [workerEntry],
+      target: "browser",
+      format: "iife",
+      minify: false,
+    });
+    if (!out.success) throw new AggregateError(out.logs, "worker bundle failed");
+    return await out.outputs[0].text();
+  }
+  const esbuild = await import("esbuild");
+  const res = await esbuild.build({
+    entryPoints: [workerEntry],
+    bundle: true,
+    write: false,
+    platform: "browser",
+    target: "chrome116",
+    format: "iife",
+  });
+  return res.outputFiles![0]!.text;
+}
+
+const workerJs = await bundleWorker();
+const manifestJson = await readFile(manifestPath, "utf8");
+
+const assets: Record<string, string> = {
+  "manifest.json": manifestJson,
+  "worker.js": workerJs,
+};
+
+const banner = "// AUTO-GENERATED by extension/build.ts — do not edit by hand.\n" +
+  "// Run `cd extension && bun build.ts` to regenerate.\n";
+const body = `export const EXTENSION_ASSETS: Record<string, string> = ${JSON.stringify(assets, null, 2)};\n`;
+
+await mkdir(dirname(assetsOut), { recursive: true });
+await writeFile(assetsOut, banner + body);
+console.log(`extension: built worker (${workerJs.length} bytes) → ${assetsOut}`);

extension/manifest.json

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+{
+  "manifest_version": 3,
+  "name": "Zero Companion",
+  "version": "1.0.0",
+  "description": "Lets the Zero agent drive a tab in your real Chrome — your logins, your session, no separate browser.",
+  "permissions": ["debugger", "tabs", "scripting", "activeTab", "alarms"],
+  "host_permissions": ["<all_urls>"],
+  "background": {
+    "service_worker": "worker.js"
+  }
+}