diff --git a/pyproject.toml b/pyproject.toml
index f39de7c..2dd7f67 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -9,7 +9,7 @@ authors = [{ name = "Astera Institute", email = "no-reply@astera.org" }]
 dependencies = [
     "absl-py",
     "etils[epath,epy]",
-    "jax",
+    "jax>=0.4.36",
     "numpy",
     "packaging",
     "Pillow",
diff --git a/src/jax_loop_utils/metric_writers/__init__.py b/src/jax_loop_utils/metric_writers/__init__.py
index 716a8f5..892f040 100644
--- a/src/jax_loop_utils/metric_writers/__init__.py
+++ b/src/jax_loop_utils/metric_writers/__init__.py
@@ -46,8 +46,11 @@
     ensure_flushes,
 )
 from jax_loop_utils.metric_writers.interface import MetricWriter
+from jax_loop_utils.metric_writers.keep_last_writer import KeepLastWriter
 from jax_loop_utils.metric_writers.logging_writer import LoggingWriter
+from jax_loop_utils.metric_writers.memory_writer import MemoryWriter
 from jax_loop_utils.metric_writers.multi_writer import MultiWriter
+from jax_loop_utils.metric_writers.prefix_suffix_writer import PrefixSuffixWriter
 from jax_loop_utils.metric_writers.utils import write_values
 
 # TODO(b/200953513): Migrate away from logging imports (on module level)
@@ -57,8 +60,11 @@
     "AsyncMultiWriter",
     "AsyncWriter",
     "ensure_flushes",
+    "KeepLastWriter",
     "LoggingWriter",
+    "MemoryWriter",
     "MetricWriter",
     "MultiWriter",
+    "PrefixSuffixWriter",
     "write_values",
 ]
diff --git a/src/jax_loop_utils/metric_writers/keep_last_writer.py b/src/jax_loop_utils/metric_writers/keep_last_writer.py
new file mode 100644
index 0000000..ceadeda
--- /dev/null
+++ b/src/jax_loop_utils/metric_writers/keep_last_writer.py
@@ -0,0 +1,53 @@
+from collections.abc import Mapping
+from typing import Any, Optional
+
+from .interface import Array, MetricWriter, Scalar
+
+
+class KeepLastWriter(MetricWriter):
+    """MetricWriter that keeps the last value for each metric in memory."""
+
+    def __init__(self, inner: MetricWriter):
+        self._inner: MetricWriter = inner
+        self.scalars: Optional[Mapping[str, Scalar]] = None
+        self.images: Optional[Mapping[str, Array]] = None
+        self.videos: Optional[Mapping[str, Array]] = None
+        self.audios: Optional[Mapping[str, Array]] = None
+        self.texts: Optional[Mapping[str, str]] = None
+        self.hparams: Optional[Mapping[str, Any]] = None
+        self.histogram_arrays: Optional[Mapping[str, Array]] = None
+        self.histogram_num_buckets: Optional[Mapping[str, int]] = None
+
+    def write_scalars(self, step: int, scalars: Mapping[str, Scalar]):
+        self._inner.write_scalars(step, scalars)
+        self.scalars = scalars
+
+    def write_images(self, step: int, images: Mapping[str, Array]):
+        self._inner.write_images(step, images)
+        self.images = images
+
+    def write_videos(self, step: int, videos: Mapping[str, Array]):
+        self._inner.write_videos(step, videos)
+        self.videos = videos
+
+    def write_audios(self, step: int, audios: Mapping[str, Array], *, sample_rate: int):
+        self._inner.write_audios(step, audios, sample_rate=sample_rate)
+        self.audios = audios
+
+    def write_texts(self, step: int, texts: Mapping[str, str]):
+        self._inner.write_texts(step, texts)
+        self.texts = texts
+
+    def write_hparams(self, hparams: Mapping[str, Any]):
+        self._inner.write_hparams(hparams)
+        self.hparams = hparams
+
+    def write_histograms(
+        self,
+        step: int,
+        arrays: Mapping[str, Array],
+        num_buckets: Optional[Mapping[str, int]] = None,
+    ):
+        self._inner.write_histograms(step, arrays, num_buckets)
+        self.histogram_arrays = arrays
+        self.histogram_num_buckets = num_buckets
diff --git a/src/jax_loop_utils/metric_writers/keep_last_writer_test.py b/src/jax_loop_utils/metric_writers/keep_last_writer_test.py
new file mode 100644
index 0000000..17b313c
--- /dev/null
+++ b/src/jax_loop_utils/metric_writers/keep_last_writer_test.py
@@ -0,0 +1,77 @@
+"""Tests for KeepLastMetricWriter."""
+
+import numpy as np
+from absl.testing import absltest
+
+from jax_loop_utils.metric_writers import keep_last_writer, noop_writer
+
+
+class KeepLastWriterTest(absltest.TestCase):
+    def setUp(self):
+        super().setUp()
+        self.writer = keep_last_writer.KeepLastWriter(noop_writer.NoOpWriter())
+
+    def test_write_scalars(self):
+        scalars1 = {"metric1": 1.0}
+        scalars2 = {"metric2": 2.0}
+
+        self.writer.write_scalars(0, scalars1)
+        self.assertEqual(self.writer.scalars, scalars1)
+
+        self.writer.write_scalars(1, scalars2)
+        self.assertEqual(self.writer.scalars, scalars2)
+
+    def test_write_images(self):
+        image = np.zeros((2, 2, 3))
+        images = {"image": image}
+
+        self.writer.write_images(0, images)
+        self.assertEqual(self.writer.images, images)
+
+    def test_write_videos(self):
+        video = np.zeros((10, 2, 2, 3))
+        videos = {"video": video}
+
+        self.writer.write_videos(0, videos)
+        self.assertEqual(self.writer.videos, videos)
+
+    def test_write_audios(self):
+        audio = np.zeros((100, 2))
+        audios = {"audio": audio}
+
+        self.writer.write_audios(0, audios, sample_rate=44100)
+        self.assertEqual(self.writer.audios, audios)
+
+    def test_write_texts(self):
+        texts = {"text": "hello world"}
+
+        self.writer.write_texts(0, texts)
+        self.assertEqual(self.writer.texts, texts)
+
+    def test_write_hparams(self):
+        hparams = {"learning_rate": 0.1}
+
+        self.writer.write_hparams(hparams)
+        self.assertEqual(self.writer.hparams, hparams)
+
+    def test_write_histograms(self):
+        arrays = {"hist": np.array([1, 2, 3])}
+        num_buckets = {"hist": 10}
+
+        self.writer.write_histograms(0, arrays, num_buckets)
+        self.assertEqual(self.writer.histogram_arrays, arrays)
+        self.assertEqual(self.writer.histogram_num_buckets, num_buckets)
+
+    def test_initial_values_are_none(self):
+        self.assertIsNone(self.writer.scalars)
+        self.assertIsNone(self.writer.images)
+        self.assertIsNone(self.writer.videos)
+        self.assertIsNone(self.writer.audios)
+        self.assertIsNone(self.writer.texts)
+        self.assertIsNone(self.writer.hparams)
+        self.assertIsNone(self.writer.histogram_arrays)
+        self.assertIsNone(self.writer.histogram_num_buckets)
+
+
+if __name__ == "__main__":
+    absltest.main()
diff --git a/src/jax_loop_utils/metric_writers/mlflow/metric_writer.py b/src/jax_loop_utils/metric_writers/mlflow/metric_writer.py
index ec47b89..508ea5e 100644
--- a/src/jax_loop_utils/metric_writers/mlflow/metric_writer.py
+++ b/src/jax_loop_utils/metric_writers/mlflow/metric_writer.py
@@ -20,17 +20,22 @@
 
 
 class MlflowMetricWriter(MetricWriterInterface):
-    """MLflow implementation of MetricWriter."""
+    """Writes metrics to MLflow Tracking."""
 
-    def __init__(self, experiment_name: str, tracking_uri: str | None = None):
+    def __init__(
+        self,
+        experiment_name: str,
+        run_name: str | None = None,
+        tracking_uri: str | None = None,
+    ):
         """Initialize MLflow writer.
 
         Args:
             experiment_name: Name of the MLflow experiment.
-            tracking_uri: Address of local or remote tracking server. If not provided, defaults
-                to the service set by ``mlflow.tracking.set_tracking_uri``. See
-                `Where Runs Get Recorded <../tracking.html#where-runs-get-recorded>`_
-                for more info.
+            run_name: Name of the MLflow run.
+            tracking_uri: Address of local or remote tracking server.
+              Treated the same as arguments to mlflow.set_tracking_uri.
+              See https://www.mlflow.org/docs/latest/python_api/mlflow.html#mlflow.set_tracking_uri
         """
         self._client = mlflow.MlflowClient(tracking_uri=tracking_uri)
         experiment = self._client.get_experiment_by_name(experiment_name)
@@ -42,7 +47,9 @@ def __init__(self, experiment_name: str, tracking_uri: str | None = None):
                 experiment_name,
             )
             experiment_id = self._client.create_experiment(experiment_name)
-        self._run_id = self._client.create_run(experiment_id=experiment_id).info.run_id
+        self._run_id = self._client.create_run(
+            experiment_id=experiment_id, run_name=run_name
+        ).info.run_id
 
     def write_scalars(self, step: int, scalars: Mapping[str, Scalar]):
         """Write scalar metrics to MLflow."""
diff --git a/src/jax_loop_utils/metric_writers/prefix_suffix_writer.py b/src/jax_loop_utils/metric_writers/prefix_suffix_writer.py
new file mode 100644
index 0000000..cef4e5e
--- /dev/null
+++ b/src/jax_loop_utils/metric_writers/prefix_suffix_writer.py
@@ -0,0 +1,70 @@
+"""Writer that adds prefix and suffix to metric keys."""
+
+from typing import Any, Mapping, Optional
+
+from jax_loop_utils.metric_writers import interface
+
+
+class PrefixSuffixWriter(interface.MetricWriter):
+    """Wraps a MetricWriter and adds prefix/suffix to all keys."""
+
+    def __init__(
+        self,
+        writer: interface.MetricWriter,
+        prefix: str = "",
+        suffix: str = "",
+    ):
+        """Initialize the writer.
+
+        Args:
+            writer: The underlying MetricWriter to wrap
+            prefix: String to prepend to all keys
+            suffix: String to append to all keys
+        """
+        self._writer = writer
+        self._prefix = prefix
+        self._suffix = suffix
+
+    def _transform_keys(self, data: Mapping[str, Any]) -> dict[str, Any]:
+        """Add prefix and suffix to all keys in the mapping."""
+        return {
+            f"{self._prefix}{key}{self._suffix}": value for key, value in data.items()
+        }
+
+    def write_scalars(self, step: int, scalars: Mapping[str, interface.Scalar]):
+        self._writer.write_scalars(step, self._transform_keys(scalars))
+
+    def write_images(self, step: int, images: Mapping[str, interface.Array]):
+        self._writer.write_images(step, self._transform_keys(images))
+
+    def write_videos(self, step: int, videos: Mapping[str, interface.Array]):
+        self._writer.write_videos(step, self._transform_keys(videos))
+
+    def write_audios(
+        self, step: int, audios: Mapping[str, interface.Array], *, sample_rate: int
+    ):
+        self._writer.write_audios(
+            step, self._transform_keys(audios), sample_rate=sample_rate
+        )
+
+    def write_texts(self, step: int, texts: Mapping[str, str]):
+        self._writer.write_texts(step, self._transform_keys(texts))
+
+    def write_histograms(
+        self,
+        step: int,
+        arrays: Mapping[str, interface.Array],
+        num_buckets: Optional[Mapping[str, int]] = None,
+    ):
+        if num_buckets is not None:
+            num_buckets = self._transform_keys(num_buckets)
+        self._writer.write_histograms(step, self._transform_keys(arrays), num_buckets)
+
+    def write_hparams(self, hparams: Mapping[str, Any]):
+        self._writer.write_hparams(self._transform_keys(hparams))
+
+    def flush(self):
+        self._writer.flush()
+
+    def close(self):
+        self._writer.close()
diff --git a/src/jax_loop_utils/metric_writers/prefix_suffix_writer_test.py b/src/jax_loop_utils/metric_writers/prefix_suffix_writer_test.py
new file mode 100644
index 0000000..b255b10
--- /dev/null
+++ b/src/jax_loop_utils/metric_writers/prefix_suffix_writer_test.py
@@ -0,0 +1,80 @@
+"""Tests for PrefixSuffixWriter."""
+
+from unittest import mock
+
+import numpy as np
+from absl.testing import absltest
+
+from jax_loop_utils.metric_writers import memory_writer, prefix_suffix_writer
+
+
+class PrefixSuffixWriterTest(absltest.TestCase):
+    def setUp(self):
+        super().setUp()
+        self.memory_writer = memory_writer.MemoryWriter()
+        self.writer = prefix_suffix_writer.PrefixSuffixWriter(
+            self.memory_writer,
+            prefix="prefix/",
+            suffix="/suffix",
+        )
+
+    def test_write_scalars(self):
+        self.writer.write_scalars(0, {"metric": 1.0})
+        self.assertEqual(self.memory_writer.scalars, {0: {"prefix/metric/suffix": 1.0}})
+
+    def test_write_images(self):
+        image = np.zeros((2, 2, 3))
+        self.writer.write_images(0, {"image": image})
+        self.assertEqual(
+            list(self.memory_writer.images[0].keys()), ["prefix/image/suffix"]
+        )
+
+    def test_write_texts(self):
+        self.writer.write_texts(0, {"text": "hello"})
+        self.assertEqual(self.memory_writer.texts, {0: {"prefix/text/suffix": "hello"}})
+
+    def test_write_histograms(self):
+        data = np.array([1, 2, 3])
+        buckets = {"hist": 10}
+        self.writer.write_histograms(0, {"hist": data}, buckets)
+        self.assertEqual(
+            list(self.memory_writer.histograms[0].arrays.keys()),
+            ["prefix/hist/suffix"],
+        )
+
+    def test_write_hparams(self):
+        self.writer.write_hparams({"param": 1})
+        self.assertEqual(self.memory_writer.hparams, {"prefix/param/suffix": 1})
+
+    def test_empty_prefix_suffix(self):
+        writer = prefix_suffix_writer.PrefixSuffixWriter(self.memory_writer)
+        writer.write_scalars(0, {"metric": 1.0})
+        self.assertEqual(self.memory_writer.scalars, {0: {"metric": 1.0}})
+
+    def test_write_videos(self):
+        video = np.zeros((10, 32, 32, 3))  # Simple video array with 10 frames
+        self.writer.write_videos(0, {"video": video})
+        self.assertEqual(
+            list(self.memory_writer.videos[0].keys()), ["prefix/video/suffix"]
+        )
+
+    def test_write_audios(self):
+        audio = np.zeros((16000,))  # 1 second of audio at 16kHz
+        self.writer.write_audios(0, {"audio": audio}, sample_rate=16000)
+        self.assertEqual(
+            list(self.memory_writer.audios[0].audios.keys()), ["prefix/audio/suffix"]
+        )
+
+    def test_close(self):
+        with mock.patch.object(self.memory_writer, "close") as mock_close:
+            self.writer.close()
+            mock_close.assert_called_once()
+
+    def test_flush(self):
+        with mock.patch.object(self.memory_writer, "flush") as mock_flush:
+            self.writer.flush()
+            mock_flush.assert_called_once()
+
+
+if __name__ == "__main__":
+    absltest.main()
diff --git a/uv.lock b/uv.lock
index f2ec1e3..6d87ecb 100644
--- a/uv.lock
+++ b/uv.lock
@@ -734,7 +734,7 @@ requires-dist = [
     { name = "etils", extras = ["epath", "epy"] },
     { name = "flax", marker = "extra == 'synopsis'" },
     { name = "ipykernel", marker = "extra == 'synopsis'" },
-    { name = "jax" },
+    { name = "jax", specifier = ">=0.4.36" },
     { name = "matplotlib", marker = "extra == 'synopsis'" },
     { name = "mlflow-skinny", marker = "extra == 'mlflow'", specifier = ">=2.0" },
     { name = "numpy" },