diff --git a/apps/server/scripts/cli.ts b/apps/server/scripts/cli.ts
index 319440a7ec24..a2292fbf9a7d 100644
--- a/apps/server/scripts/cli.ts
+++ b/apps/server/scripts/cli.ts
@@ -19,6 +19,7 @@ import {
   ServerCliDevelopmentIconTargetMissingError,
   ServerCliExecutableImportError,
 } from "./cliErrors.ts";
+import { publishPlatformsThenLauncher } from "./publishOrder.ts";
 
 const RepoRoot = Effect.service(Path.Path).pipe(
   Effect.flatMap((path) => path.fromFileUrl(new URL("../../..", import.meta.url))),
@@ -212,7 +213,7 @@ const publishCmd = Command.make(
       if (config.provenance) args.push("--provenance");
       if (config.dryRun) args.push("--dry-run");
 
-      for (const tarball of [...platformTarballs, launcherTarball]) {
+      const publish = Effect.fn("publish")(function* (tarball: string) {
         const spawnCommand = yield* resolveSpawnCommand("npm", [...args, tarball]);
         yield* Effect.log(`[cli] npm ${args.join(" ")} ${path.basename(tarball)}`);
         yield* runCommand(
@@ -223,7 +224,10 @@ const publishCmd = Command.make(
             shell: spawnCommand.shell,
           }),
         );
-      }
+      });
+
+      // Each publish takes about 17s, so the platform packages go at once.
+      yield* publishPlatformsThenLauncher({ platformTarballs, launcherTarball, publish });
     }),
 ).pipe(
   Command.withDescription(
diff --git a/apps/server/scripts/publishOrder.test.ts b/apps/server/scripts/publishOrder.test.ts
new file mode 100644
index 000000000000..3951511eec83
--- /dev/null
+++ b/apps/server/scripts/publishOrder.test.ts
@@ -0,0 +1,58 @@
+import { assert, it } from "@effect/vitest";
+import * as Effect from "effect/Effect";
+import * as Exit from "effect/Exit";
+import * as Latch from "effect/Latch";
+
+import { publishPlatformsThenLauncher } from "./publishOrder.ts";
+
+const platformTarballs = ["a.tgz", "b.tgz", "c.tgz"];
+const launcherTarball = "t3.tgz";
+
+// A fake publish that records when each upload starts and ends. Platform
+// uploads only end once every platform upload has started, so they have to
+// run at the same time. `failing` fails as soon as it starts.
+const fakePublish = Effect.fn("fakePublish")(function* (failing?: string) {
+  const events: Array<string> = [];
+  const allStarted = yield* Latch.make();
+  let started = 0;
+  const publish = (tarball: string) =>
+    Effect.gen(function* () {
+      events.push(`start ${tarball}`);
+      if (tarball === launcherTarball) return;
+      started += 1;
+      if (started === platformTarballs.length) yield* allStarted.open;
+      if (tarball === failing) return yield* Effect.fail(`${tarball} failed`);
+      yield* allStarted.await;
+      events.push(`end ${tarball}`);
+    });
+  return { events, publish };
+});
+
+it.effect("publishes the platform packages at once and the launcher last", () =>
+  Effect.gen(function* () {
+    const { events, publish } = yield* fakePublish();
+
+    yield* publishPlatformsThenLauncher({ platformTarballs, launcherTarball, publish });
+
+    assert.deepStrictEqual(events.slice(0, 3).toSorted(), [
+      "start a.tgz",
+      "start b.tgz",
+      "start c.tgz",
+    ]);
+    assert.strictEqual(events.at(-1), `start ${launcherTarball}`);
+  }),
+);
+
+it.effect("finishes the other uploads and skips the launcher when one fails", () =>
+  Effect.gen(function* () {
+    const { events, publish } = yield* fakePublish("b.tgz");
+
+    const exit = yield* Effect.exit(
+      publishPlatformsThenLauncher({ platformTarballs, launcherTarball, publish }),
+    );
+
+    assert.deepStrictEqual(exit, Exit.fail("b.tgz failed"));
+    assert.includeMembers(events, ["end a.tgz", "end c.tgz"]);
+    assert.notInclude(events, `start ${launcherTarball}`);
+  }),
+);
diff --git a/apps/server/scripts/publishOrder.ts b/apps/server/scripts/publishOrder.ts
new file mode 100644
index 000000000000..b53fbebdc736
--- /dev/null
+++ b/apps/server/scripts/publishOrder.ts
@@ -0,0 +1,26 @@
+import * as Effect from "effect/Effect";
+import * as Result from "effect/Result";
+
+/**
+ * Publishes every platform package at once, then the launcher, which must
+ * never be installable before the executables it points to. When one platform
+ * fails, the other uploads still finish rather than being interrupted: npm
+ * never accepts the same version twice, and an interrupted upload may already
+ * be live. The launcher is then skipped and the first failure is returned.
+ */
+export const publishPlatformsThenLauncher = <E, R>(input: {
+  readonly platformTarballs: ReadonlyArray<string>;
+  readonly launcherTarball: string;
+  readonly publish: (tarball: string) => Effect.Effect<void, E, R>;
+}) =>
+  Effect.gen(function* () {
+    const results = yield* Effect.all(input.platformTarballs.map(input.publish), {
+      concurrency: "unbounded",
+      mode: "result",
+    });
+    const failed = results.find(Result.isFailure);
+    if (failed) {
+      return yield* Effect.fail(failed.failure);
+    }
+    yield* input.publish(input.launcherTarball);
+  });
diff --git a/scripts/build-npm-platform-packages.ts b/scripts/build-npm-platform-packages.ts
index 6a134d99e2c5..4f56f5b449e6 100644
--- a/scripts/build-npm-platform-packages.ts
+++ b/scripts/build-npm-platform-packages.ts
@@ -429,24 +429,22 @@ export const buildNpmPlatformPackages = Effect.fn("buildNpmPlatformPackages")(fu
   yield* fs.makeDirectory(path.join(input.outputDir, NPM_PLATFORM_PACKAGE_SCOPE), {
     recursive: true,
   });
-  const outputs: Array<NpmPackageOutput> = [];
-  for (const { key, archive } of archives) {
-    outputs.push(
-      yield* stagePlatformPackage({
-        key,
-        archive,
-        outputDir: input.outputDir,
-        version: input.version,
-      }),
-    );
-  }
-  outputs.push(
+  // Each archive stages in its own scratch dir, so all of them unpack and
+  // compress at once. Sequentially this took about 45s for five archives.
+  const platformOutputs = yield* Effect.forEach(
+    archives,
+    ({ key, archive }) =>
+      stagePlatformPackage({ key, archive, outputDir: input.outputDir, version: input.version }),
+    { concurrency: "unbounded" },
+  );
+  const outputs = [
+    ...platformOutputs,
     yield* stageLauncherPackage({
       outputDir: input.outputDir,
       version: input.version,
       platformKeys: archives.map((entry) => entry.key),
     }),
-  );
+  ];
 
   for (const output of outputs) {
     yield* Effect.log(`[npm-packages] Wrote ${output.packageDir} and ${output.tarball}`);