diff --git a/AGENTS.md b/AGENTS.md
index 043db2c2d..52b8c6fa3 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -28,6 +28,9 @@ It captures practical rules that prevent avoidable CI and PR churn.
 - In docs Markdown, keep `<!--codeinclude-->` blocks tight with no blank lines between the markers and the include line, or the rendered snippet will contain blank lines between code lines.
 - Tests should verify observable behavior changes, not only internal/config state.
   - Example: for a security option, assert a real secure/insecure behavior difference.
+- Tests should not pull container images that the test suite does not already pull.
+  - Every extra image increases how long the tests take to run and how much storage they need.
+  - Reuse an image the tests already use, for example `cristianrgreco/testcontainer:1.1.14` in `packages/testcontainers`, or the module's own image.
 - When adding a regression test for a bug fix, follow a red-green-refactor workflow.
   - Run the focused test against the pre-fix implementation and confirm it fails for the expected reason.
   - Apply the implementation change, rerun the same test, and confirm it passes.
diff --git a/biome.json b/biome.json
index d4cafe1fe..e1744c9a7 100644
--- a/biome.json
+++ b/biome.json
@@ -25,6 +25,9 @@
       "preset": "recommended",
       "correctness": {
         "noUndeclaredDependencies": "error"
+      },
+      "nursery": {
+        "noFloatingPromises": "error"
       }
     }
   },
diff --git a/packages/modules/nats/src/nats-container.test.ts b/packages/modules/nats/src/nats-container.test.ts
index 5714572e1..39800661c 100644
--- a/packages/modules/nats/src/nats-container.test.ts
+++ b/packages/modules/nats/src/nats-container.test.ts
@@ -18,16 +18,18 @@ describe("NatsContainer", { timeout: 180_000 }, () => {
 
     const sub = nc.subscribe(SUBJECT);
 
-    (async () => {
+    const received = (async () => {
+      const messages: string[] = [];
       for await (const m of sub) {
-        const actual = TD.decode(m.data);
-        expect(actual).toEqual(PAYLOAD);
+        messages.push(TD.decode(m.data));
       }
-    })().then();
+      return messages;
+    })();
 
     nc.publish(SUBJECT, TE.encode(PAYLOAD));
 
     await nc.drain();
+    expect(await received).toEqual([PAYLOAD]);
     await nc.close();
     // }
   });
diff --git a/packages/testcontainers/smoke-test.js b/packages/testcontainers/smoke-test.js
index 0da0d1d0f..021310b93 100644
--- a/packages/testcontainers/smoke-test.js
+++ b/packages/testcontainers/smoke-test.js
@@ -1,7 +1,12 @@
 const { GenericContainer } = require("./build/index");
 
-(async () => {
-  const container = await new GenericContainer("alpine:3.12").withCommand(["sleep", "infinity"]).start();
+void (async () => {
+  try {
+    const container = await new GenericContainer("alpine:3.12").withCommand(["sleep", "infinity"]).start();
 
-  await container.stop();
+    await container.stop();
+  } catch (err) {
+    console.error(err);
+    process.exit(1);
+  }
 })();
diff --git a/packages/testcontainers/src/generic-container/generic-container-dockerfile.test.ts b/packages/testcontainers/src/generic-container/generic-container-dockerfile.test.ts
index a747bf0c1..37ae3e42f 100644
--- a/packages/testcontainers/src/generic-container/generic-container-dockerfile.test.ts
+++ b/packages/testcontainers/src/generic-container/generic-container-dockerfile.test.ts
@@ -86,7 +86,7 @@ describe("GenericContainer Dockerfile", { timeout: 180_000 }, () => {
       await using dockerEventStream = await getDockerEventStream();
       const dockerPullEventPromise = waitForDockerEvent(dockerEventStream.events, "pull");
       let hasResolved = false;
-      dockerPullEventPromise.then(() => (hasResolved = true));
+      void dockerPullEventPromise.then(() => (hasResolved = true));
       await containerSpec.build();
 
       expect(hasResolved).toBeFalsy();
diff --git a/packages/testcontainers/src/generic-container/generic-container.ts b/packages/testcontainers/src/generic-container/generic-container.ts
index c44793ff7..7d74006c1 100644
--- a/packages/testcontainers/src/generic-container/generic-container.ts
+++ b/packages/testcontainers/src/generic-container/generic-container.ts
@@ -206,8 +206,10 @@ export class GenericContainer implements TestContainer {
 
     if (this.filesToCopy.length > 0 || this.directoriesToCopy.length > 0 || this.contentsToCopy.length > 0) {
       const archive = await this.createArchiveToCopyToContainer();
-      archive.finalize();
-      await client.container.putArchive(container, archive, "/", this.copyToContainerOptions);
+      await Promise.all([
+        archive.finalize(),
+        client.container.putArchive(container, archive, "/", this.copyToContainerOptions),
+      ]);
     }
 
     for (const archive of this.archivesToCopy) {
diff --git a/packages/testcontainers/src/generic-container/started-generic-container.ts b/packages/testcontainers/src/generic-container/started-generic-container.ts
index e68e7018b..3abceb934 100644
--- a/packages/testcontainers/src/generic-container/started-generic-container.ts
+++ b/packages/testcontainers/src/generic-container/started-generic-container.ts
@@ -204,8 +204,7 @@ export class StartedGenericContainer implements StartedTestContainer {
     filesToCopyWithStats.forEach(({ source, target, mode, stats }) => {
       tar.file(source, { name: target, mode, stats });
     });
-    tar.finalize();
-    await client.container.putArchive(this.container, tar, "/");
+    await Promise.all([tar.finalize(), client.container.putArchive(this.container, tar, "/")]);
     log.debug(`Copied files to container`, { containerId: this.container.id });
   }
 
@@ -216,8 +215,7 @@ export class StartedGenericContainer implements StartedTestContainer {
     directoriesToCopy.forEach(({ source, target }) => {
       tar.directory(source, target);
     });
-    tar.finalize();
-    await client.container.putArchive(this.container, tar, "/");
+    await Promise.all([tar.finalize(), client.container.putArchive(this.container, tar, "/")]);
     log.debug(`Copied directories to container`, { containerId: this.container.id });
   }
 
@@ -228,8 +226,7 @@ export class StartedGenericContainer implements StartedTestContainer {
     contentsToCopy.forEach(({ content, target, mode }) => {
       tar.append(content, { name: target, mode: mode });
     });
-    tar.finalize();
-    await client.container.putArchive(this.container, tar, "/");
+    await Promise.all([tar.finalize(), client.container.putArchive(this.container, tar, "/")]);
     log.debug(`Copied content to container`, { containerId: this.container.id });
   }