diff --git a/.travis.yml b/.travis.yml
index 20f5ae3..4cc0ac9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -60,6 +60,8 @@ matrix:
 
   allow_failures:
     - python: "nightly"
+    - os: osx
+      env: TOXENV=py27
 
 install:
   - pip install --upgrade setuptools
diff --git a/dwave/cloud/client.py b/dwave/cloud/client.py
index 2605872..ec06111 100644
--- a/dwave/cloud/client.py
+++ b/dwave/cloud/client.py
@@ -161,6 +161,7 @@ class Client(object):
     _SUBMISSION_THREAD_COUNT = 5
     _UPLOAD_PROBLEM_THREAD_COUNT = 1
     _UPLOAD_PART_THREAD_COUNT = 10
+    _ENCODE_PROBLEM_THREAD_COUNT = _UPLOAD_PROBLEM_THREAD_COUNT
     _CANCEL_THREAD_COUNT = 1
     _POLL_THREAD_COUNT = 2
     _LOAD_THREAD_COUNT = 5
@@ -481,6 +482,9 @@ class Client(object):
         self._upload_part_executor = \
             PriorityThreadPoolExecutor(self._UPLOAD_PART_THREAD_COUNT)
 
+        self._encode_problem_executor = \
+            ThreadPoolExecutor(self._ENCODE_PROBLEM_THREAD_COUNT)
+
         dispatch_event(
             'after_client_init', obj=self, args=args, return_value=None)
 
@@ -549,6 +553,8 @@ class Client(object):
         self._upload_problem_executor.shutdown()
         logger.debug("Shutting down problem part upload executor")
         self._upload_part_executor.shutdown()
+        logger.debug("Shutting down problem encoder executor")
+        self._encode_problem_executor.shutdown()
 
         # Send kill-task to all worker threads
         # Note: threads can't be 'killed' in Python, they have to die by
@@ -1072,6 +1078,38 @@ class Client(object):
         Note:
             This method is always run inside of a daemon thread.
         """
+
+        def task_done():
+            self._submission_queue.task_done()
+
+        def filter_ready(item):
+            """Pass-through ready (encoded) problems, re-enqueue ones for which
+            the encoding is in progress, and fail the ones for which encoding
+            failed.
+            """
+
+            # body is a `concurrent.futures.Future`, so make sure
+            # it's ready for submitting
+            if item.body.done():
+                exc = item.body.exception()
+                if exc:
+                    # encoding failed, submit should fail as well
+                    logger.info("Problem encoding prior to submit "
+                                "failed with: %r", exc)
+                    item.future._set_error(exc)
+                    task_done()
+
+                else:
+                    # problem ready for submit
+                    return [item]
+
+            else:
+                # body not ready, return the item to queue
+                self._submission_queue.put(item)
+                task_done()
+
+            return []
+
         session = self.create_session()
         try:
             while True:
@@ -1083,19 +1121,25 @@ class Client(object):
                 item = self._submission_queue.get()
 
                 if item is None:
+                    task_done()
                     break
 
-                ready_problems = [item]
+                ready_problems = filter_ready(item)
                 while len(ready_problems) < self._SUBMIT_BATCH_SIZE:
                     try:
-                        ready_problems.append(self._submission_queue.get_nowait())
+                        item = self._submission_queue.get_nowait()
                     except queue.Empty:
                         break
 
+                    ready_problems.extend(filter_ready(item))
+
+                if not ready_problems:
+                    continue
+
                 # Submit the problems
                 logger.debug("Submitting %d problems", len(ready_problems))
-                body = '[' + ','.join(mess.body for mess in ready_problems) + ']'
                 try:
+                    body = '[' + ','.join(mess.body.result() for mess in ready_problems) + ']'
                     try:
                         response = session.post('problems/', body)
                         localtime_of_response = epochnow()
@@ -1115,14 +1159,14 @@ class Client(object):
 
                     for mess in ready_problems:
                         mess.future._set_error(exception, sys.exc_info())
-                        self._submission_queue.task_done()
+                        task_done()
                     continue
 
                 # Pass on the information
                 for submission, res in zip(ready_problems, message):
                     submission.future._set_clock_diff(response, localtime_of_response)
                     self._handle_problem_status(res, submission.future)
-                    self._submission_queue.task_done()
+                    task_done()
 
                 # this is equivalent to a yield to scheduler in other threading libraries
                 time.sleep(0)
diff --git a/dwave/cloud/concurrency.py b/dwave/cloud/concurrency.py
index fb39b97..b0a2676 100644
--- a/dwave/cloud/concurrency.py
+++ b/dwave/cloud/concurrency.py
@@ -111,3 +111,21 @@ class PriorityThreadPoolExecutor(concurrent.futures.ThreadPoolExecutor):
     def __init__(self, *args, **kwargs):
         super(PriorityThreadPoolExecutor, self).__init__(*args, **kwargs)
         self._work_queue = _PrioritizingQueue()
+
+
+class Present(concurrent.futures.Future):
+    """Already resolved :class:`~concurrent.futures.Future` object.
+
+    Users should treat this class as just another
+    :class:`~concurrent.futures.Future`, the difference being an implementation
+    detail: :class:`Present` is "resolved" at construction time.
+    """
+
+    def __init__(self, result=None, exception=None):
+        super(Present, self).__init__()
+        if result is not None:
+            self.set_result(result)
+        elif exception is not None:
+            self.set_exception(exception)
+        else:
+            raise ValueError("can't provide both 'result' and 'exception'")
diff --git a/dwave/cloud/solver.py b/dwave/cloud/solver.py
index d153453..43e9611 100644
--- a/dwave/cloud/solver.py
+++ b/dwave/cloud/solver.py
@@ -35,12 +35,15 @@ import logging
 import warnings
 from collections import Mapping
 
+import six
+
 from dwave.cloud.exceptions import *
 from dwave.cloud.coders import (
     encode_problem_as_qp, encode_problem_as_bq,
     decode_qp_numpy, decode_qp, decode_bq)
 from dwave.cloud.utils import uniform_iterator, reformat_qubo_as_ising
 from dwave.cloud.computation import Future
+from dwave.cloud.concurrency import Present
 from dwave.cloud.events import dispatch_event
 
 # Use numpy if available for fast encoding/decoding
@@ -300,6 +303,40 @@ class UnstructuredSolver(BaseSolver):
         bqm = dimod.BinaryQuadraticModel.from_qubo(qubo)
         return self.sample_bqm(bqm, **params)
 
+    def _encode_any_problem_as_bqm_ref(self, problem, params):
+        """Encode `problem` for submitting in `bqm-ref` format. Upload the
+        problem if it's not already uploaded.
+
+        Args:
+            problem (:class:`~dimod.BinaryQuadraticModel`/str):
+                A binary quadratic model, or a reference to one (Problem ID).
+
+            params (dict):
+                Parameters for the sampling method, solver-specific.
+
+        Returns:
+            str:
+                JSON-encoded problem submit body
+
+        """
+
+        if isinstance(problem, six.string_types):
+            problem_id = problem
+        else:
+            logger.debug("To encode the problem for submit via 'bqm-ref', "
+                         "we need to upload it first.")
+            problem_id = self.upload_bqm(problem).result()
+
+        body = json.dumps({
+            'solver': self.id,
+            'data': encode_problem_as_bq(problem_id),
+            'type': 'bqm',
+            'params': params
+        })
+        logger.trace("Sampling request encoded as: %s", body)
+
+        return body
+
     def sample_bqm(self, bqm, **params):
         """Sample from the specified :term:`BQM`.
 
@@ -317,21 +354,19 @@ class UnstructuredSolver(BaseSolver):
         Note:
             To use this method, dimod package has to be installed.
         """
-        # encode the request
-        body = json.dumps({
-            'solver': self.id,
-            'data': encode_problem_as_bq(bqm),
-            'type': 'bqm',
-            'params': params
-        })
-        logger.trace("Encoded sample request: %s", body)
 
-        future = Future(solver=self, id_=None, return_matrix=self.return_matrix)
+        # encode the request (body as future)
+        body = self.client._encode_problem_executor.submit(
+            self._encode_any_problem_as_bqm_ref,
+            problem=bqm, params=params)
+
+        # computation future holds a reference to the remote job
+        computation = Future(solver=self, id_=None, return_matrix=self.return_matrix)
 
         logger.debug("Submitting new problem to: %s", self.id)
-        self.client._submit(body, future)
+        self.client._submit(body, computation)
 
-        return future
+        return computation
 
     def upload_bqm(self, bqm):
         """Upload the specified :term:`BQM` to SAPI, returning a Problem ID
@@ -631,22 +666,23 @@ class StructuredSolver(BaseSolver):
         # transform some of the parameters in-place
         self._format_params(type_, combined_params)
 
-        body = json.dumps({
+        body_data = json.dumps({
             'solver': self.id,
             'data': encode_problem_as_qp(self, linear, quadratic),
             'type': type_,
             'params': combined_params
         })
-        logger.trace("Encoded sample request: %s", body)
+        logger.trace("Encoded sample request: %s", body_data)
 
-        future = Future(solver=self, id_=None, return_matrix=self.return_matrix)
+        body = Present(result=body_data)
+        computation = Future(solver=self, id_=None, return_matrix=self.return_matrix)
 
         logger.debug("Submitting new problem to: %s", self.id)
-        self.client._submit(body, future)
+        self.client._submit(body, computation)
 
-        dispatch_event('after_sample', obj=self, args=args, return_value=future)
+        dispatch_event('after_sample', obj=self, args=args, return_value=computation)
 
-        return future
+        return computation
 
     def _format_params(self, type_, params):
         """Reformat some of the parameters for sapi."""

diff --git a/tests/test_mock_unstructured_submission.py b/tests/test_mock_unstructured_submission.py
index 0b9a002..22c958a 100644
--- a/tests/test_mock_unstructured_submission.py
+++ b/tests/test_mock_unstructured_submission.py
@@ -23,6 +23,7 @@ import numpy
 from dwave.cloud.client import Client
 from dwave.cloud.solver import UnstructuredSolver
 from dwave.cloud.testing import mock
+from dwave.cloud.concurrency import Present
 
 
 def unstructured_solver_data():
@@ -74,42 +75,111 @@ class TestUnstructuredSolver(unittest.TestCase):
         # use a global mocked session, so we can modify it on-fly
         session = mock.Mock()
 
+        # upload is now part of submit, so we need to mock it
+        mock_problem_id = 'mock-problem-id'
+        def mock_upload(self, bqm):
+            return Present(result=mock_problem_id)
+
         # construct a functional solver by mocking client and api response data
         with mock.patch.object(Client, 'create_session', lambda self: session):
             with Client('endpoint', 'token') as client:
-                solver = UnstructuredSolver(client, unstructured_solver_data())
-
-                # direct bqm sampling
-                ss = dimod.ExactSolver().sample(bqm)
-                session.post = lambda path, _: choose_reply(
-                    path, {'problems/': complete_reply(ss)})
-
-                fut = solver.sample_bqm(bqm)
-                numpy.testing.assert_array_equal(fut.sampleset, ss)
-                numpy.testing.assert_array_equal(fut.samples, ss.record.sample)
-                numpy.testing.assert_array_equal(fut.energies, ss.record.energy)
-                numpy.testing.assert_array_equal(fut.occurrences, ss.record.num_occurrences)
-
-                # ising sampling
-                lin, quad, _ = bqm.to_ising()
-                ss = dimod.ExactSolver().sample_ising(lin, quad)
-                session.post = lambda path, _: choose_reply(
-                    path, {'problems/': complete_reply(ss)})
-
-                fut = solver.sample_ising(lin, quad)
-                numpy.testing.assert_array_equal(fut.sampleset, ss)
-                numpy.testing.assert_array_equal(fut.samples, ss.record.sample)
-                numpy.testing.assert_array_equal(fut.energies, ss.record.energy)
-                numpy.testing.assert_array_equal(fut.occurrences, ss.record.num_occurrences)
-
-                # qubo sampling
-                qubo, _ = bqm.to_qubo()
-                ss = dimod.ExactSolver().sample_qubo(qubo)
-                session.post = lambda path, _: choose_reply(
-                    path, {'problems/': complete_reply(ss)})
-
-                fut = solver.sample_qubo(qubo)
-                numpy.testing.assert_array_equal(fut.sampleset, ss)
-                numpy.testing.assert_array_equal(fut.samples, ss.record.sample)
-                numpy.testing.assert_array_equal(fut.energies, ss.record.energy)
-                numpy.testing.assert_array_equal(fut.occurrences, ss.record.num_occurrences)
+                with mock.patch.object(UnstructuredSolver, 'upload_bqm', mock_upload):
+                    solver = UnstructuredSolver(client, unstructured_solver_data())
+
+                    # direct bqm sampling
+                    ss = dimod.ExactSolver().sample(bqm)
+                    session.post = lambda path, _: choose_reply(
+                        path, {'problems/': complete_reply(ss)})
+
+                    fut = solver.sample_bqm(bqm)
+                    numpy.testing.assert_array_equal(fut.sampleset, ss)
+                    numpy.testing.assert_array_equal(fut.samples, ss.record.sample)
+                    numpy.testing.assert_array_equal(fut.energies, ss.record.energy)
+                    numpy.testing.assert_array_equal(fut.occurrences, ss.record.num_occurrences)
+
+                    # submit of pre-uploaded bqm problem
+                    fut = solver.sample_bqm(mock_problem_id)
+                    numpy.testing.assert_array_equal(fut.sampleset, ss)
+                    numpy.testing.assert_array_equal(fut.samples, ss.record.sample)
+                    numpy.testing.assert_array_equal(fut.energies, ss.record.energy)
+                    numpy.testing.assert_array_equal(fut.occurrences, ss.record.num_occurrences)
+
+                    # ising sampling
+                    lin, quad, _ = bqm.to_ising()
+                    ss = dimod.ExactSolver().sample_ising(lin, quad)
+                    session.post = lambda path, _: choose_reply(
+                        path, {'problems/': complete_reply(ss)})
+
+                    fut = solver.sample_ising(lin, quad)
+                    numpy.testing.assert_array_equal(fut.sampleset, ss)
+                    numpy.testing.assert_array_equal(fut.samples, ss.record.sample)
+                    numpy.testing.assert_array_equal(fut.energies, ss.record.energy)
+                    numpy.testing.assert_array_equal(fut.occurrences, ss.record.num_occurrences)
+
+                    # qubo sampling
+                    qubo, _ = bqm.to_qubo()
+                    ss = dimod.ExactSolver().sample_qubo(qubo)
+                    session.post = lambda path, _: choose_reply(
+                        path, {'problems/': complete_reply(ss)})
+
+                    fut = solver.sample_qubo(qubo)
+                    numpy.testing.assert_array_equal(fut.sampleset, ss)
+                    numpy.testing.assert_array_equal(fut.samples, ss.record.sample)
+                    numpy.testing.assert_array_equal(fut.energies, ss.record.energy)
+                    numpy.testing.assert_array_equal(fut.occurrences, ss.record.num_occurrences)
+
+    def test_upload_failure(self):
+        """Submit should gracefully fail if upload as part of submit fails."""
+
+        # build a test problem
+        bqm = dimod.BQM.from_ising({}, {'ab': 1})
+
+        # use a global mocked session, so we can modify it on-fly
+        session = mock.Mock()
+
+        # upload is now part of submit, so we need to mock it
+        mock_upload_exc = ValueError('error')
+        def mock_upload(self, bqm):
+            return Present(exception=mock_upload_exc)
+
+        # construct a functional solver by mocking client and api response data
+        with mock.patch.object(Client, 'create_session', lambda self: session):
+            with Client('endpoint', 'token') as client:
+                with mock.patch.object(UnstructuredSolver, 'upload_bqm', mock_upload):
+                    solver = UnstructuredSolver(client, unstructured_solver_data())
+
+                    # direct bqm sampling
+                    ss = dimod.ExactSolver().sample(bqm)
+                    session.post = lambda path, _: choose_reply(
+                        path, {'problems/': complete_reply(ss)})
+
+                    fut = solver.sample_bqm(bqm)
+
+                    with self.assertRaises(type(mock_upload_exc)):
+                        fut.result()
+
+    def test_many_upload_failures(self):
+        """Failure handling in high concurrency mode works correctly."""
+
+        # build a test problem
+        bqm = dimod.BQM.from_ising({}, {'ab': 1})
+
+        # use a global mocked session, so we can modify it on-fly
+        session = mock.Mock()
+
+        # upload is now part of submit, so we need to mock it
+        mock_upload_exc = ValueError('error')
+        def mock_upload(self, bqm):
+            return Present(exception=mock_upload_exc)
+
+        # construct a functional solver by mocking client and api response data
+        with mock.patch.object(Client, 'create_session', lambda self: session):
+            with Client('endpoint', 'token') as client:
+                with mock.patch.object(UnstructuredSolver, 'upload_bqm', mock_upload):
+                    solver = UnstructuredSolver(client, unstructured_solver_data())
+
+                    futs = [solver.sample_bqm(bqm) for _ in range(100)]
+
+                    for fut in futs:
+                        with self.assertRaises(type(mock_upload_exc)):
+                            fut.result()

Combine upload and submit steps for unstructured solvers
tests/test_mock_unstructured_submission.py::TestUnstructuredSolver::test_many_upload_failures tests/test_mock_unstructured_submission.py::TestUnstructuredSolver::test_submit_immediate_reply tests/test_mock_unstructured_submission.py::TestUnstructuredSolver::test_upload_failure