diff --git a/.github/workflows/run_pre_commit.yaml b/.github/workflows/run_pre_commit.yaml
index eb7a4b214..e80facaeb 100644
--- a/.github/workflows/run_pre_commit.yaml
+++ b/.github/workflows/run_pre_commit.yaml
@@ -9,6 +9,7 @@ jobs:
     strategy:
       matrix:
         python-version: ["3.10"]
+        jax-version: ["0.4.14"]
 
     steps:
       - uses: actions/checkout@v3
@@ -20,16 +21,7 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           pip install flake8 pytest pre-commit
-          pip install --upgrade "jax[cpu]==0.4.11" "jaxlib==0.4.11"
-          # install haliax from source b/c it's changing in parallel with this repo
-          pip install git+https://github.com/stanford-crfm/haliax.git
-          pip install .
-#      - name: Lint with flake8
-#        run: |
-#          # stop the build if there are Python syntax errors or undefined names
-#          flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
-#          # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
-#          flake8 . --count --exit-zero --max-complexity=50 --max-line-length=127 --statistics
+          pip install . "jax[cpu]==${{ matrix.jax-version }}" "jaxlib==${{ matrix.jax-version }}"
       - name: "Run Pre-commit"
         run: |
           pre-commit run --all-files --show-diff-on-failure
diff --git a/config/gpt2_1536_sophiah.yaml b/config/gpt2_1536_sophiah.yaml
new file mode 100644
index 000000000..0d1008106
--- /dev/null
+++ b/config/gpt2_1536_sophiah.yaml
@@ -0,0 +1,32 @@
+data:
+  train_urls:
+    - "gs://pubmed-mosaic/openwebtext-sharded/openwebtext_train.{1..128}-of-128.jsonl.gz"
+  validation_urls:
+    - "gs://pubmed-mosaic/openwebtext-sharded/openwebtext_val.{1..8}-of-8.jsonl.gz"
+  cache_dir: "gs://levanter-data/tokenized/openwebtext/"
+  tokenizer: "gpt2"
+model:
+  type: gpt2
+  hidden_dim: 1536
+  num_heads: 24
+  num_layers: 48
+  seq_len: 1024
+  gradient_checkpointing: true
+  scale_attn_by_inverse_layer_idx: true
+trainer:
+  tracker:
+    project: "levanter"
+    tags: [ "openwebtext", "gpt2"]
+
+  mp: p=f32,c=bfloat16
+  model_axis_size: 1
+  per_device_parallelism: 2
+  per_device_eval_parallelism: 8
+optimizer:
+  type: sophia-h
+  learning_rate: 2E-4
+  weight_decay: 0.2
+  min_lr_ratio: 0.1
+  gamma: 0.01
+  # sophia needs a minimum amount of warmup or it doesn't do well
+  warmup: 2000
diff --git a/examples/alpaca-lora/alpaca_lora.py b/examples/alpaca-lora/alpaca_lora.py
index eef14e026..c83beddaa 100644
--- a/examples/alpaca-lora/alpaca_lora.py
+++ b/examples/alpaca-lora/alpaca_lora.py
@@ -114,40 +114,40 @@ def loraize_hf_model(model):
             }
         )
 
-    logger.info(f"Total parameter count: {all_param_count}")
-    logger.info(f"Trainable parameter count: {just_lora_params}")
-    logger.info(f"Fraction of parameters that are trainable: {just_lora_params * 1.0 / all_param_count%.3}")
-
-    # Levanter has two kinds of data loaders: sharded and replicated. Replicated is simpler and allows for
-    # single pass training. Sharded only loads a subset of the data on each device, and is more efficient for large
-    # datasets. We use replicated here since the dataset is small.
-    loader = trainer.replicated_loader(train_dataset, trainer.TrainBatch)
-    loader = non_caching_cycle(loader)
-
-    if state.step != 0:
-        logger.info(f"Resuming training from step {state.step}")
-        for i in range(state.step):
-            next(loader)  # type: ignore
-
-    # Save HF PEFT checkpoints periodically (and at the end of training), which is just the lora weights
-    if config.hf_save_path is not None:
-        full_save_path = os.path.join(config.hf_save_path, trainer.run_id)
-        trainer.add_hook(
-            save_peft_checkpoint_callback(
-                full_save_path, config.lora, config.model_name_or_path, tokenizer, config.hf_upload
-            ),
-            every=config.hf_save_steps,
-        )
-
-    # Save merged HF checkpoints if requested
-    if config.merged_hf_save_path is not None:
-        full_save_path = os.path.join(config.merged_hf_save_path, trainer.run_id)
-        trainer.add_hook(
-            save_merged_hf_checkpoint_callback(full_save_path, converter, config.merged_hf_upload),
-            every=config.hf_save_steps,
-        )
-
-    trainer.train(state, loader)
+        logger.info(f"Total parameter count: {all_param_count}")
+        logger.info(f"Trainable parameter count: {just_lora_params}")
+        logger.info(f"Fraction of parameters that are trainable: {just_lora_params * 1.0 / all_param_count%.3}")
+
+        # Levanter has two kinds of data loaders: sharded and replicated. Replicated is simpler and allows for
+        # single pass training. Sharded only loads a subset of the data on each device, and is more efficient for large
+        # datasets. We use replicated here since the dataset is small.
+        loader = trainer.replicated_loader(train_dataset, trainer.TrainBatch)
+        loader = non_caching_cycle(loader)
+
+        if state.step != 0:
+            logger.info(f"Resuming training from step {state.step}")
+            for i in range(state.step):
+                next(loader)  # type: ignore
+
+        # Save HF PEFT checkpoints periodically (and at the end of training), which is just the lora weights
+        if config.hf_save_path is not None:
+            full_save_path = os.path.join(config.hf_save_path, trainer.run_id)
+            trainer.add_hook(
+                save_peft_checkpoint_callback(
+                    full_save_path, config.lora, config.model_name_or_path, tokenizer, config.hf_upload
+                ),
+                every=config.hf_save_steps,
+            )
+
+        # Save merged HF checkpoints if requested
+        if config.merged_hf_save_path is not None:
+            full_save_path = os.path.join(config.merged_hf_save_path, trainer.run_id)
+            trainer.add_hook(
+                save_merged_hf_checkpoint_callback(full_save_path, converter, config.merged_hf_upload),
+                every=config.hf_save_steps,
+            )
+
+        trainer.train(state, loader)
 
 
 if __name__ == "__main__":
diff --git a/src/levanter/__init__.py b/src/levanter/__init__.py
index ecabba8df..3042154e2 100644
--- a/src/levanter/__init__.py
+++ b/src/levanter/__init__.py
@@ -8,5 +8,5 @@
 import levanter.tracker as tracker
 import levanter.trainer as trainer
 import levanter.visualization as visualization
-from levanter.tracker import current_tracker, get_tracker
+from levanter.tracker import current_tracker
 from levanter.trainer import initialize
diff --git a/src/levanter/data/sharded_dataset.py b/src/levanter/data/sharded_dataset.py
index 0ec178e08..d162882ac 100644
--- a/src/levanter/data/sharded_dataset.py
+++ b/src/levanter/data/sharded_dataset.py
@@ -147,9 +147,10 @@ class WrappedHFDataset(ShardedDataset[dict]):
     kwargs are passed to load_dataset
     """
 
-    def __init__(self, id, *, split, **kwargs):
+    def __init__(self, id, *, split, streaming: bool = True, **kwargs):
         self.id = id
         self.split = split
+        self.streaming = streaming
         self.kwargs = kwargs
         self._shard_names = self._compute_shard_names()
 
@@ -184,7 +185,7 @@ def open_shard_at_row(self, shard_name: str, row: int) -> Iterator[dict]:
     def _load_dataset(self):
         # obnoxiously, the dataset loading stuff doesn't work with ray because of multiprocessing
         # so we have to do this hacky thing where we load the dataset in the worker
-        return datasets.load_dataset(self.id, split=self.split, **self.kwargs)
+        return datasets.load_dataset(self.id, split=self.split, streaming=self.streaming, **self.kwargs)
 
 
 class TextUrlDataset(ShardedDataset[str]):
diff --git a/src/levanter/main/lora_lm.py b/src/levanter/main/lora_lm.py
index 862aff5d5..ecad5e87f 100644
--- a/src/levanter/main/lora_lm.py
+++ b/src/levanter/main/lora_lm.py
@@ -92,6 +92,7 @@ def loraize_hf_model(model):
         state = trainer.initial_state(training_key, model=model, is_trainable=lora_param_filter)
 
         all_param_count = parameter_count(state.model)
+        # TODO: remove this once we put this in trainer itself
         just_lora_params = parameter_count(eqx.filter(state.model, lora_param_filter))
 
         levanter.tracker.log_summary(
@@ -118,6 +119,7 @@ def loraize_hf_model(model):
         train_loader = trainer.sharded_loader(train_dataset, Batch)
 
         # boilerplate hooks and such
+        trainer.add_eval_hook(eval_dataset)
         trainer.add_hook(callbacks.log_performance_stats(Pos.size, trainer.config.train_batch_size), every=1)
         if config.peft_save_path is not None:
             full_save_path = os.path.join(config.peft_save_path, trainer.run_id)
diff --git a/src/levanter/optim/sophia.py b/src/levanter/optim/sophia.py
index 8895942a2..daa03285e 100644
--- a/src/levanter/optim/sophia.py
+++ b/src/levanter/optim/sophia.py
@@ -11,7 +11,7 @@
 from jax.random import PRNGKey
 from jaxtyping import PRNGKeyArray
 
-# import levanter.tracker
+import levanter.tracker
 from levanter.optim.config import HessianOptConfig, OptimizerConfig
 from levanter.optim.util import hvp, tree_gaussian_like
 from levanter.utils.jax_utils import parameter_count, tree_filter_like
@@ -348,9 +348,7 @@ def update_fn(updates, state, params=None, *, obj_fn, **kwargs):
             updates = jax.tree_util.tree_map(lambda u: jnp.clip(u, -clip_threshold, clip_threshold), updates)
             stats["optim/unclipped_fraction"] = unclipped_count / parameter_count(updates)
 
-        # this doesn't work well on CPU, so skip if cpu
-        # if jax.lib.xla_bridge.get_backend().platform != "cpu":
-        #     levanter.tracker.jit_log_metrics(stats, step=state.count)
+        levanter.tracker.jit_log_metrics(stats, step=state.count)
 
         if mu_dtype is not None:
             mu = jax.tree_util.tree_map(lambda t: t.astype(mu_dtype), mu)
diff --git a/src/levanter/trainer.py b/src/levanter/trainer.py
index 14aa98327..53611809f 100644
--- a/src/levanter/trainer.py
+++ b/src/levanter/trainer.py
@@ -259,29 +259,30 @@ def EvalBatch(self):
         return self.config.EvalBatch
 
     def __enter__(self):
+        if len(self._cmanagers) > 0:
+            raise RuntimeError("Trainer is already entered")
 
-        this_managers = [
+        self._cmanagers = [
             levanter.current_tracker(self.tracker),
             self.device_mesh,
             hax.axis_mapping(self.parameter_axis_mapping),
         ]
-        self._cmanagers.append(this_managers)
 
-        for cmanager in this_managers:
+        for cmanager in self._cmanagers:
             cmanager.__enter__()
 
         return self
 
     def __exit__(self, *args):
-        assert len(self._cmanagers) > 0, "Trainer.__exit__ called without corresponding Trainer.__enter__"
-        cur_managers = self._cmanagers.pop()
         problems = []
-        for cmanager in reversed(cur_managers):
+        for cmanager in reversed(self._cmanagers):
             try:
                 cmanager.__exit__(*args)
             except Exception as e:
                 problems.append(e)
 
+        self._cmanagers = []
+
         if len(problems) > 0:
             raise RuntimeError("Exception(s) occurred while exiting trainer", problems) from problems[0]
 
@@ -395,23 +396,23 @@ def training_steps(
         Generator that yields training steps and runs hooks.
         """
         iter_data = iter(train_loader)
-        with levanter.current_tracker(self.tracker):
-            while state.step < self.num_train_steps:
-                with capture_time() as loading_time:
-                    example = next(iter_data)
 
-                levanter.tracker.log_metrics({"throughput/loading_time": loading_time()}, step=state.step)
+        while state.step < self.num_train_steps:
+            with capture_time() as loading_time:
+                example = next(iter_data)
 
-                info = self.train_step(state, example)
+            levanter.tracker.log_metrics({"throughput/loading_time": loading_time()}, step=state.step)
 
-                if run_hooks:
-                    with capture_time() as hook_time:
-                        self.run_hooks(info)
+            info = self.train_step(state, example)
+            state = info.state
 
-                    levanter.tracker.log_metrics({"throughput/hook_time": hook_time()}, step=state.step)
+            if run_hooks:
+                with capture_time() as hook_time:
+                    self.run_hooks(info)
 
-                state = info.state
-                yield info
+                levanter.tracker.log_metrics({"throughput/hook_time": hook_time()}, step=state.step)
+
+            yield info
 
     def train(self, state: TrainerState[M], train_loader: Iterable[X], run_hooks: bool = True) -> StepInfo[M]:
         """
@@ -488,21 +489,21 @@ def _train_step(self, state: TrainerState, *batch, **batch_kwargs) -> tuple[Scal
         key, new_key = jax.random.split(state.training_key)
         model = inference_mode(state.model, False)
 
-        loss, grads = self._compute_gradients_microbatched(model, batch, **batch_kwargs, key=key)
+        loss, grads = self._compute_gradients_microbatched(self.loss_fn, model, batch, **batch_kwargs, key=key)
 
         new_state = self._take_train_step(state, model, grads, *batch, **batch_kwargs, key=key)
         new_state = dataclasses.replace(new_state, training_key=new_key)
 
         return loss, new_state
 
-    def _compute_gradients_microbatched(self, model: M, batch, **batch_kwargs) -> tuple[Scalar, M]:
-        grad_fn = eqx.filter_value_and_grad(self.loss_fn, has_aux=False)
+    def _compute_gradients_microbatched(self, loss_fn, model: M, batch, **batch_kwargs) -> tuple[Scalar, M]:
+        grad_fn = eqx.filter_value_and_grad(loss_fn, has_aux=False)
         grad_fn = microbatched(
             grad_fn,
             self.TrainBatch,
-            self.config.per_device_parallelism,
-            self.parameter_axis_mapping,
+            self.config.microbatch_size,
             self.parameter_axis_mapping,
+            self.compute_axis_mapping,
         )
         return grad_fn(model, *batch, **batch_kwargs)
 
@@ -512,13 +513,14 @@ def _take_train_step(self, state: S, model, grads, *batch, **batch_kwargs) -> S:
         """
         # only train on the trainable parameters. We're leaning on JAX to do dead code elimination for us
         with hax.axis_mapping(self.parameter_axis_mapping):
+            opt_state = state.opt_state
             train_grads = _partition_trainable_params(grads, state.is_trainable)[0]
             trainable_model = _partition_trainable_params(model, state.is_trainable)[0]
-            updates, opt_state = self.optimizer.update(train_grads, state.opt_state, params=trainable_model)
-
             partial_fn = lambda model: self.loss_fn(model, *batch, **batch_kwargs)
 
-            updates, opt_state = self.optimizer.update(grads, opt_state, params=trainable_model, obj_fn=partial_fn)
+            updates, opt_state = self.optimizer.update(
+                train_grads, opt_state, params=trainable_model, obj_fn=partial_fn
+            )
             model = eqx.apply_updates(model, updates)
 
             return dataclasses.replace(state, _step=state._step + 1, model=model, opt_state=opt_state)
@@ -787,7 +789,7 @@ class AllConfig(Protocol):
 
 def initialize(config: TrainerConfig | AllConfig):
     """Initializes jax, logging, setting the run name/id in the process. Also initializes tracking and saves config
-    as hyperparameters and as an artifact"""
+    as hyperparameters and an artifact"""
     if isinstance(config, TrainerConfig):
         trainer_config = config
     else:
@@ -797,6 +799,10 @@ def initialize(config: TrainerConfig | AllConfig):
     levanter.tracker.log_configuration(config)
 
 
+def _params_only(t):
+    return eqx.filter(t, is_inexact_arrayish)
+
+
 def _partition_trainable_params(model, filter):
     """
     Partitions the model into trainable and non-trainable parameters. This is used internally
diff --git a/src/levanter/utils/hf_utils.py b/src/levanter/utils/hf_utils.py
index 408a8c8da..ef77dcdfd 100644
--- a/src/levanter/utils/hf_utils.py
+++ b/src/levanter/utils/hf_utils.py
@@ -18,7 +18,8 @@ def num_cpus_used_by_tokenizer(tokenizer) -> int:
         else:
             # This is a bit hacky, but HF's fast tokenizers are parallelized under the hood.
             # we reserve a couple of cores just so Ray has somewhere to run the coordinator.
-            return min(max(1, logical_cpu_core_count() - 2), 32)
+            # Empirically it doesn't usually exceed 16-20, and it's useful to have some slack
+            return min(max(1, logical_cpu_core_count() - 2), 12)
     else:
         return 1
 
diff --git a/tests/test_doremi.py b/tests/test_doremi.py
index c6ac76a47..64a84a191 100644
--- a/tests/test_doremi.py
+++ b/tests/test_doremi.py
@@ -6,6 +6,7 @@
 
 import haliax as hax
 
+import levanter.tracker
 from levanter.callbacks import eval_loss_loop
 from levanter.data.dataset import ShardableDataset
 from levanter.data.mixture import MixtureDataset
@@ -136,15 +137,17 @@ def init_model():
     assert l3_ref < l1_ref < l2_ref
 
     from levanter.doremi import estimate_mixture_weights
-
-    w = estimate_mixture_weights(
-        initial_proxy=init_model(),
-        ref=ref_model,
-        data_sources=datasets,
-        trainer_config=tiny_trainer_config,
-        key=next(keys),
-        loss_fn=compute_loss_fn,
-    )
+    from levanter.tracker import NoopTracker
+
+    with levanter.tracker.current_tracker(NoopTracker()):
+        w = estimate_mixture_weights(
+            initial_proxy=init_model(),
+            ref=ref_model,
+            data_sources=datasets,
+            trainer_config=tiny_trainer_config,
+            key=next(keys),
+            loss_fn=compute_loss_fn,
+        )
 
     w1 = w["d1"]
     w2 = w["d2"]
diff --git a/tests/test_tensorstore_serialization.py b/tests/test_tensorstore_serialization.py
index 398bad1f0..caf8a365d 100644
--- a/tests/test_tensorstore_serialization.py
+++ b/tests/test_tensorstore_serialization.py
@@ -1,10 +1,12 @@
 from tempfile import TemporaryDirectory
+from typing import Any
 
 import equinox as eqx
 import jax
 import jax.numpy as jnp
 import numpy as np
 import optax
+import pytest
 from chex import assert_trees_all_close
 
 import haliax as hax
@@ -127,3 +129,26 @@ def make_state(key):
             jax.tree_util.tree_leaves(arrays_only(restored_model)),
             jax.tree_util.tree_leaves(arrays_only(initial_model)),
         )
+
+
+def test_tensorstore_ok_with_nones():
+    A = hax.Axis("A", 10)
+
+    class MyModule(eqx.Module):
+        a: Any
+        b: Any
+
+    m = MyModule(a=None, b=hax.zeros(A))
+    m2 = MyModule(a=None, b=hax.ones(A))
+
+    with TemporaryDirectory() as tmpdir:
+        tree_serialize_leaves_tensorstore(tmpdir, m)
+        m3 = tree_deserialize_leaves_tensorstore(tmpdir, m2)
+        assert m3.a is None
+        assert hax.all(m3.b == hax.zeros(A))
+
+    m3 = MyModule(a=hax.zeros(A), b=hax.ones(A))
+    with TemporaryDirectory() as tmpdir:
+        tree_serialize_leaves_tensorstore(tmpdir, m2)
+        with pytest.raises(ValueError):
+            tree_deserialize_leaves_tensorstore(tmpdir, m3)