diff --git a/crates/xmtp_cryptography/src/basic_credential.rs b/crates/xmtp_cryptography/src/basic_credential.rs
index ee8c8b458c..f40e5eb0a8 100644
--- a/crates/xmtp_cryptography/src/basic_credential.rs
+++ b/crates/xmtp_cryptography/src/basic_credential.rs
@@ -328,12 +328,15 @@ mod tests {
 
     #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test::wasm_bindgen_test)]
     #[cfg_attr(not(target_arch = "wasm32"), test)]
-    fn secret_key_can_not_be_exposed() {
-        let keypair = XmtpInstallationCredential::new();
-        let secret = keypair.0.as_ref();
+    fn test_from_raw_mismatched_public_key() {
+        // Generate two different keypairs using the existing API
+        let keypair_a = SignatureKeyPair::new(SignatureScheme::ED25519).unwrap();
+        let keypair_b = SignatureKeyPair::new(SignatureScheme::ED25519).unwrap();
+
+        let private_key_a = keypair_a.private().to_vec();
+        let public_key_b = keypair_b.public().to_vec();
 
-        assert_ne!(keypair.public_bytes(), secret.as_bytes());
-        assert_ne!(keypair.public_slice(), secret.as_bytes());
-        assert_ne!(keypair.verifying_key().as_bytes(), &secret.to_bytes());
+        let result = XmtpInstallationCredential::from_raw(&private_key_a, &public_key_b);
+        assert!(result.is_err());
     }
 }
diff --git a/sdks/js/browser-sdk/test/DeviceSync.test.ts b/sdks/js/browser-sdk/test/DeviceSync.test.ts
index 5f59f9e386..e9cfcf369d 100644
--- a/sdks/js/browser-sdk/test/DeviceSync.test.ts
+++ b/sdks/js/browser-sdk/test/DeviceSync.test.ts
@@ -2,7 +2,12 @@ import { ConsentEntityType, ConsentState } from "@xmtp/wasm-bindings";
 import { describe, expect, it } from "vitest";
 import { HistorySyncUrls } from "@/constants";
 import { uuid } from "@/utils/uuid";
-import { createRegisteredClient, createSigner, sleep } from "@test/helpers";
+import {
+  createRegisteredClient,
+  createSigner,
+  sleep,
+  waitFor,
+} from "@test/helpers";
 
 describe("DeviceSync", () => {
   it("should sync consent across installations", async () => {
@@ -130,11 +135,6 @@ describe("DeviceSync", () => {
     const messagesBefore = await group2Before!.messages();
     expect(messagesBefore.length).toBe(2);
 
-    await sleep(1000);
-    await alix.syncAllDeviceSyncGroups();
-    await sleep(1000);
-    await alix2.syncAllDeviceSyncGroups();
-
     // list available archives - may fail in some environments
     try {
       const archives = await alix2.listAvailableArchives(7);
@@ -143,7 +143,23 @@ describe("DeviceSync", () => {
       // listAvailableArchives may not be fully supported in all test environments
     }
 
-    await alix2.processSyncArchive("123");
+    // The archive payload propagates to alix2 over the network asynchronously,
+    // so a single device-sync pass can race ahead of delivery and leave
+    // processSyncArchive unable to find the payload (DeviceSyncError::MissingPayload).
+    // Re-sync the device-sync groups and retry until the pinned payload arrives.
+    await waitFor(
+      async () => {
+        await alix.syncAllDeviceSyncGroups();
+        await alix2.syncAllDeviceSyncGroups();
+        try {
+          await alix2.processSyncArchive("123");
+          return true;
+        } catch {
+          return false;
+        }
+      },
+      { timeout: 30000, interval: 1000 },
+    );
     await sleep(1000);
     await alix2.conversations.syncAll();
 
diff --git a/sdks/js/browser-sdk/test/Preferences.test.ts b/sdks/js/browser-sdk/test/Preferences.test.ts
index 13186d5e75..41c8f323b3 100644
--- a/sdks/js/browser-sdk/test/Preferences.test.ts
+++ b/sdks/js/browser-sdk/test/Preferences.test.ts
@@ -10,6 +10,7 @@ import {
   createRegisteredClient,
   createSigner,
   sleep,
+  waitFor,
 } from "@test/helpers";
 
 describe("Preferences", () => {
@@ -205,20 +206,34 @@ describe("Preferences", () => {
     });
 
     await client3.conversations.syncAll();
-    await sleep(1000);
-    await client1.conversations.syncAll();
-    await sleep(1000);
     await client2.conversations.syncAll();
-    await sleep(1000);
-
-    setTimeout(() => {
-      void stream.end();
-    }, 100);
 
+    // Collect updates concurrently while the preference changes propagate.
     const preferences: UserPreferenceUpdate[] = [];
-    for await (const update of stream) {
-      preferences.push(...update);
+    const collecting = (async () => {
+      for await (const update of stream) {
+        preferences.push(...update);
+      }
+    })();
+
+    // Four updates are expected: two consent updates (the group and the
+    // inbox-id consent changes) and two HMAC-key updates (one per new
+    // installation). These propagate over the network asynchronously, so
+    // re-sync until the stream has observed all of them rather than racing a
+    // fixed delay, which can cut off the last update and yield only 3.
+    try {
+      await waitFor(
+        async () => {
+          await client1.conversations.syncAll();
+          return preferences.length >= 4;
+        },
+        { timeout: 30000, interval: 1000 },
+      );
+    } finally {
+      await stream.end();
+      await collecting;
     }
+
     expect(preferences.length).toBe(4);
     const consentUpdate1 = preferences[0] as Extract<
       UserPreferenceUpdate,
diff --git a/sdks/js/browser-sdk/test/helpers.ts b/sdks/js/browser-sdk/test/helpers.ts
index 840521c118..2da91e98db 100644
--- a/sdks/js/browser-sdk/test/helpers.ts
+++ b/sdks/js/browser-sdk/test/helpers.ts
@@ -23,11 +23,11 @@ export const sleep = (ms: number) =>
   new Promise((resolve) => setTimeout(resolve, ms));
 
 export const waitFor = async (
-  condition: () => boolean,
+  condition: () => boolean | Promise<boolean>,
   { timeout = 2000, interval = 10 } = {},
 ) => {
   const start = Date.now();
-  while (!condition()) {
+  while (!(await condition())) {
     if (Date.now() - start > timeout) {
       throw new Error(`waitFor timed out after ${timeout}ms`);
     }