diff --git a/test/privy/integration/jwt_exchange_test.rb b/test/privy/integration/jwt_exchange_test.rb
index 18e66a7..e0cd9b3 100644
--- a/test/privy/integration/jwt_exchange_test.rb
+++ b/test/privy/integration/jwt_exchange_test.rb
@@ -6,6 +6,10 @@ class Privy::Test::Integration::JwtExchangeTest < Privy::Test::IntegrationTest
   def setup
     super
     skip("JWT_AUTH_SK not set") unless ENV["JWT_AUTH_SK"] && !ENV["JWT_AUTH_SK"].empty?
+
+    # /wallets/authenticate (which jwt_exchange wraps) rejects JWTs for users
+    # that don't own any wallet. Ensure the freshly-minted user has one.
+    create_user_owned_wallet
   end
 
   def test_exchange_jwt_returns_authorization_key
diff --git a/test/privy/integration/services/wallets_test.rb b/test/privy/integration/services/wallets_test.rb
index adc0638..0391e8e 100644
--- a/test/privy/integration/services/wallets_test.rb
+++ b/test/privy/integration/services/wallets_test.rb
@@ -203,8 +203,7 @@ def test_raw_sign_on_p256_owned_wallet_returns_signature
   def test_raw_sign_on_user_owned_wallet_returns_signature
     skip("JWT_AUTH_SK not set") unless ENV["JWT_AUTH_SK"] && !ENV["JWT_AUTH_SK"].empty?
 
-    user = client.users.get_by_custom_auth_id(custom_user_id: jwt_auth_subject)
-    wallet = client.wallets.create(wallet_create_params: {chain_type: :tron, owner: {user_id: user.id}})
+    wallet = create_user_owned_wallet(chain_type: :tron)
     jwt = generate_test_jwt
 
     ctx = Privy::Authorization::AuthorizationContext.build(user_jwts: [jwt])
diff --git a/test/privy/integration/support/jwt_helpers.rb b/test/privy/integration/support/jwt_helpers.rb
index 248342e..4861e5c 100644
--- a/test/privy/integration/support/jwt_helpers.rb
+++ b/test/privy/integration/support/jwt_helpers.rb
@@ -2,16 +2,26 @@
 
 require "openssl"
 require "jwt"
+require "securerandom"
 
 module Privy
   module Test
     module Integration
       module JwtHelpers
+        # A unique custom-auth subject per test instance. Memoized so the JWT
+        # `sub` claim and the user's custom_auth_id stay in lockstep within one
+        # test, while Minitest's per-test instance gives us a fresh value across
+        # tests and runs. This avoids accumulating wallets under a single shared
+        # user (which trips the per-user wallet limit on staging).
         def jwt_auth_subject
-          ENV.fetch("JWT_AUTH_SUBJECT", "java-sdk-sub-id")
+          @jwt_auth_subject ||= "ruby-sdk-test-#{SecureRandom.uuid}"
         end
 
         def generate_test_jwt
+          # Ensure the Privy user exists before handing out a JWT for them; the
+          # API endpoints that accept these JWTs (e.g. /wallets/authenticate)
+          # 404 when the subject has never been linked to a user.
+          jwt_auth_user
           raw = ENV.fetch("JWT_AUTH_SK")
           pem = raw.gsub('\n', "\n").gsub("\r", "").strip
           private_key = OpenSSL::PKey::RSA.new(pem)
@@ -19,9 +29,18 @@ def generate_test_jwt
           JWT.encode(payload, private_key, "RS256", {typ: "JWT"})
         end
 
-        def create_user_owned_wallet
-          user = client.users.get_by_custom_auth_id(custom_user_id: jwt_auth_subject)
-          client.wallets.create(wallet_create_params: {chain_type: :ethereum, owner: {user_id: user.id}})
+        # Lazily creates a Privy user backed by a fresh custom-auth subject and
+        # returns it. Subsequent calls within the same test return the same user.
+        def jwt_auth_user
+          @jwt_auth_user ||= client.users.create(
+            linked_accounts: [{type: :custom_auth, custom_user_id: jwt_auth_subject}]
+          )
+        end
+
+        def create_user_owned_wallet(chain_type: :ethereum)
+          client.wallets.create(
+            wallet_create_params: {chain_type: chain_type, owner: {user_id: jwt_auth_user.id}}
+          )
         end
       end
     end