diff --git a/lib/gooddata/models/user_filters/user_filter_builder.rb b/lib/gooddata/models/user_filters/user_filter_builder.rb
index ac139bb81..e0f42838d 100644
--- a/lib/gooddata/models/user_filters/user_filter_builder.rb
+++ b/lib/gooddata/models/user_filters/user_filter_builder.rb
@@ -22,6 +22,19 @@ module UserFilterBuilder
     @all_domain_users = {}
     @mutex = Mutex.new
 
+    # Caps on error entries embedded in a raised exception's message (and logged).
+    # Domain-wide syncs can produce one entry per user/value across a whole domain,
+    # and a single entry can embed large value lists; stringifying the raw
+    # collection exhausts the JRuby heap (GRIF-951).
+    MAX_ERRORS_IN_MESSAGE = 10
+    MAX_ERROR_ENTRY_CHARS = 1_000
+
+    # Renders a bounded sample of an error collection for logs and exception
+    # messages: caps both the number of entries and each entry's rendered size.
+    def self.bounded_error_sample(errors)
+      errors.take(MAX_ERRORS_IN_MESSAGE).map { |e| e.inspect.slice(0, MAX_ERROR_ENTRY_CHARS) }
+    end
+
     # Main Entry function. Gets values and processes them to get filters
     # that are suitable for other function to process.
     # Values can be read from file or provided inline as an array.
@@ -488,7 +501,9 @@ def self.execute_mufs(user_filters, options = {})
         errors = errors.map do |e|
           e.merge(pid: project.pid)
         end
-        fail GoodData::FilterMaqlizationError, errors
+        sample = bounded_error_sample(errors)
+        GoodData.logger.error("Maqlizing MUFs failed with #{errors.size} error(s). First #{sample.size}: #{sample.pretty_inspect}")
+        fail GoodData::FilterMaqlizationError, "Maqlizing MUFs resulted in #{errors.size} error(s). First #{sample.size}: #{sample}"
       end
 
       filters = user_filters.map { |data| client.create(MandatoryUserFilter, data, project: project) }
@@ -542,7 +557,11 @@ def self.execute_mufs(user_filters, options = {})
         end
         project_log_formatter.log_user_filter_results(create_results, to_create)
         create_errors = create_results.select { |r| r[:status] == :failed }
-        fail "Creating MUFs resulted in errors: #{create_errors}" if create_errors.any?
+        if create_errors.any?
+          sample = bounded_error_sample(create_errors)
+          GoodData.logger.error("Creating MUFs failed with #{create_errors.size} error(s). First #{sample.size}: #{sample.pretty_inspect}")
+          fail "Creating MUFs resulted in errors, count: #{create_errors.size}, first #{sample.size}: #{sample}"
+        end
       end
 
       if to_delete.empty?
@@ -575,7 +594,11 @@ def self.execute_mufs(user_filters, options = {})
 
           project_log_formatter.log_user_filter_results(delete_results, to_delete)
           delete_errors = delete_results.select { |r| r[:status] == :failed } if delete_results
-          fail "Deleting MUFs resulted in errors: #{delete_errors}" if delete_errors&.any?
+          if delete_errors&.any?
+            sample = bounded_error_sample(delete_errors)
+            GoodData.logger.error("Deleting MUFs failed with #{delete_errors.size} error(s). First #{sample.size}: #{sample.pretty_inspect}")
+            fail "Deleting MUFs resulted in errors, count: #{delete_errors.size}, first #{sample.size}: #{sample}"
+          end
         end
       end
 
@@ -643,7 +666,11 @@ def self.execute(user_filters, project_filters, klass, options = {})
                                maqlify_filters(filters, users, options.merge(users_cache: users_cache, users_must_exist: users_must_exist))
                              end
 
-      fail GoodData::FilterMaqlizationError, errors if !ignore_missing_values && !errors.empty?
+      if !ignore_missing_values && !errors.empty?
+        sample = bounded_error_sample(errors)
+        GoodData.logger.error("Maqlizing variables failed with #{errors.size} error(s). First #{sample.size}: #{sample.pretty_inspect}")
+        fail GoodData::FilterMaqlizationError, "Maqlizing variables resulted in #{errors.size} error(s). First #{sample.size}: #{sample}"
+      end
       filters = user_filters.map { |data| client.create(klass, data, project: project) }
       resolve_user_filters(filters, project_filters)
     end
diff --git a/spec/unit/models/user_filters/user_filter_builder_spec.rb b/spec/unit/models/user_filters/user_filter_builder_spec.rb
index 3452b66ac..cf3b975dc 100644
--- a/spec/unit/models/user_filters/user_filter_builder_spec.rb
+++ b/spec/unit/models/user_filters/user_filter_builder_spec.rb
@@ -199,5 +199,26 @@
         expect { subject.execute_mufs(filter_definitions, options) }.to raise_error(/Creating MUFs resulted in errors/)
       end
     end
+
+    context 'when creating MUFs results in a large number of errors' do
+      let(:failed_users) do
+        Array.new(500) { |i| { 'login' => "user#{i}@example.com", 'detail' => 'x' * 1_000 } }
+      end
+
+      before do
+        allow(client).to receive(:post)
+          .and_return 'userFiltersUpdateResult' => { 'failed' => failed_users }
+      end
+
+      it 'raises an error with a message bounded to the first few errors' do
+        expect { subject.execute_mufs(filter_definitions, options) }.to raise_error do |error|
+          expect(error.message).to match(/Creating MUFs resulted in errors, count: 500, first 10/)
+          expect(error.message).to include('user0@example.com')
+          expect(error.message).to include('user9@example.com')
+          expect(error.message).not_to include('user10@example.com')
+          expect(error.message.size).to be < 15_000
+        end
+      end
+    end
   end
 end