diff --git a/.github/workflows/testing.yml b/.github/workflows/testing.yml
index c240ec23..af7100fd 100644
--- a/.github/workflows/testing.yml
+++ b/.github/workflows/testing.yml
@@ -56,7 +56,7 @@ jobs:
       - name: Test with pytest
         env:
           MP_API_KEY: ${{ secrets[env.API_KEY_NAME] }}
-          #MP_API_ENDPOINT: https://api-preview.materialsproject.org/
+          # MP_API_ENDPOINT: https://api-preview.materialsproject.org/
         run: |
           pytest -n auto -x --cov=mp_api --cov-report=xml
       - uses: codecov/codecov-action@v1
diff --git a/mp_api/client/core/client.py b/mp_api/client/core/client.py
index 0545d78d..37b58aee 100644
--- a/mp_api/client/core/client.py
+++ b/mp_api/client/core/client.py
@@ -8,8 +8,10 @@
 import gzip
 import inspect
 import itertools
+import logging
 import os
 import platform
+import shutil
 import sys
 import warnings
 from concurrent.futures import FIRST_COMPLETED, ThreadPoolExecutor, wait
@@ -21,13 +23,17 @@
 from json import JSONDecodeError
 from math import ceil
 from typing import TYPE_CHECKING, ForwardRef, Optional, get_args
-from urllib.parse import quote
+from urllib.parse import quote, urljoin
 
 import boto3
+import pyarrow as pa
+import pyarrow.dataset as ds
 import requests
 from botocore import UNSIGNED
 from botocore.config import Config
 from botocore.exceptions import ClientError
+from deltalake import DeltaTable, QueryBuilder, convert_to_deltalake
+from emmet.core.arrow import arrowize
 from emmet.core.utils import jsanitize
 from pydantic import BaseModel, create_model
 from requests.adapters import HTTPAdapter
@@ -38,6 +44,7 @@
 from mp_api.client.core.exceptions import MPRestError
 from mp_api.client.core.settings import MAPI_CLIENT_SETTINGS
 from mp_api.client.core.utils import (
+    MPDataset,
     load_json,
     validate_api_key,
     validate_endpoint,
@@ -62,6 +69,15 @@
     __version__ = os.getenv("SETUPTOOLS_SCM_PRETEND_VERSION")
 
 
+hdlr = logging.StreamHandler()
+fmt = logging.Formatter("%(name)s - %(levelname)s - %(message)s")
+hdlr.setFormatter(fmt)
+
+logger = logging.getLogger(__name__)
+logger.setLevel(logging.INFO)
+logger.addHandler(hdlr)
+
+
 class _DictLikeAccess(BaseModel):
     """Define a pydantic mix-in which permits dict-like access to model fields."""
 
@@ -85,6 +101,7 @@ class BaseRester:
     suffix: str = ""
     document_model: type[BaseModel] | None = None
     primary_key: str = "material_id"
+    delta_backed: bool = False
 
     def __init__(
         self,
@@ -98,6 +115,10 @@ def __init__(
         timeout: int = 20,
         headers: dict | None = None,
         mute_progress_bars: bool = MAPI_CLIENT_SETTINGS.MUTE_PROGRESS_BARS,
+        local_dataset_cache: (
+            str | os.PathLike
+        ) = MAPI_CLIENT_SETTINGS.LOCAL_DATASET_CACHE,
+        force_renew: bool = False,
         **kwargs,
     ):
         """Initialize the REST API helper class.
@@ -129,6 +150,9 @@ def __init__(
             timeout: Time in seconds to wait until a request timeout error is thrown
             headers: Custom headers for localhost connections.
             mute_progress_bars: Whether to disable progress bars.
+            local_dataset_cache: Target directory for downloading full datasets. Defaults
+                to 'mp_datasets' in the user's home directory
+            force_renew: Option to overwrite existing local dataset
             **kwargs: access to legacy kwargs that may be in the process of being deprecated
         """
         self.api_key = validate_api_key(api_key)
@@ -141,7 +165,14 @@ def __init__(
         self.timeout = timeout
         self.headers = headers or {}
         self.mute_progress_bars = mute_progress_bars
-        self.db_version = BaseRester._get_database_version(self.base_endpoint)
+
+        (
+            self.db_version,
+            self.access_controlled_batch_ids,
+        ) = BaseRester._get_heartbeat_info(self.base_endpoint)
+
+        self.local_dataset_cache = local_dataset_cache
+        self.force_renew = force_renew
 
         self._session = session
         self._s3_client = s3_client
@@ -209,8 +240,9 @@ def __exit__(self, exc_type, exc_val, exc_tb):  # pragma: no cover
 
     @staticmethod
     @cache
-    def _get_database_version(endpoint):
-        """The Materials Project database is periodically updated and has a
+    def _get_heartbeat_info(endpoint) -> tuple[str, str]:
+        """DB version:
+        The Materials Project database is periodically updated and has a
         database version associated with it. When the database is updated,
         consolidated data (information about "a material") may and does
         change, while calculation data about a specific calculation task
@@ -220,9 +252,24 @@ def _get_database_version(endpoint):
         where "_DD" may be optional. An additional numerical or `postN` suffix
         might be added if multiple releases happen on the same day.
 
-        Returns: database version as a string
+        Access Controlled Datasets:
+        Certain contributions to the Materials Project have access
+        control restrictions that require explicit agreement to the
+        Terms of Use for the respective datasets prior to access being
+        granted.
+
+        A full list of the Terms of Use for all contributions in the
+        Materials Project are available at:
+
+        https://next-gen.materialsproject.org/about/terms
+
+        Returns:
+            tuple with database version as a string and a comma separated
+            string with all calculation batch identifiers that have access
+            restrictions
         """
-        return requests.get(url=endpoint + "heartbeat").json()["db_version"]
+        response = requests.get(url=endpoint + "heartbeat").json()
+        return response["db_version"], response["access_controlled_batch_ids"]
 
     def _post_resource(
         self,
@@ -353,10 +400,7 @@ def _patch_resource(
             raise MPRestError(str(ex))
 
     def _query_open_data(
-        self,
-        bucket: str,
-        key: str,
-        decoder: Callable | None = None,
+        self, bucket: str, key: str, decoder: Callable | None = None
     ) -> tuple[list[dict] | list[bytes], int]:
         """Query and deserialize Materials Project AWS open data s3 buckets.
 
@@ -460,6 +504,12 @@ def _query_resource(
             url = validate_endpoint(self.endpoint, suffix=suburl)
 
             if query_s3:
+                pbar_message = (  # type: ignore
+                    f"Retrieving {self.document_model.__name__} documents"  # type: ignore
+                    if self.document_model is not None
+                    else "Retrieving documents"
+                )
+
                 if "/" not in self.suffix:
                     suffix = self.suffix
                 elif self.suffix == "molecules/summary":
@@ -469,15 +519,177 @@ def _query_resource(
                     suffix = infix if suffix == "core" else suffix
                     suffix = suffix.replace("_", "-")
 
-                # Paginate over all entries in the bucket.
-                # TODO: change when a subset of entries needed from DB
+                # Check if user has access to GNoMe
+                # temp suppress tqdm
+                re_enable = not self.mute_progress_bars
+                self.mute_progress_bars = True
+                has_gnome_access = bool(
+                    self._submit_requests(
+                        url=urljoin(self.base_endpoint, "materials/summary/"),
+                        criteria={
+                            "batch_id": "gnome_r2scan_statics",
+                            "_fields": "material_id",
+                        },
+                        use_document_model=False,
+                        num_chunks=1,
+                        chunk_size=1,
+                        timeout=timeout,
+                    )
+                    .get("meta", {})
+                    .get("total_doc", 0)
+                )
+                self.mute_progress_bars = not re_enable
+
                 if "tasks" in suffix:
-                    bucket_suffix, prefix = "parsed", "tasks_atomate2"
+                    bucket_suffix, prefix = ("parsed", "core/tasks/")
                 else:
                     bucket_suffix = "build"
                     prefix = f"collections/{self.db_version.replace('.', '-')}/{suffix}"
 
                 bucket = f"materialsproject-{bucket_suffix}"
+
+                if self.delta_backed:
+                    target_path = str(
+                        self.local_dataset_cache.joinpath(f"{bucket_suffix}/{prefix}")
+                    )
+                    os.makedirs(target_path, exist_ok=True)
+
+                    if DeltaTable.is_deltatable(target_path):
+                        if self.force_renew:
+                            shutil.rmtree(target_path)
+                            logger.warning(
+                                f"Regenerating {suffix} dataset at {target_path}..."
+                            )
+                            os.makedirs(target_path, exist_ok=True)
+                        else:
+                            logger.warning(
+                                f"Dataset for {suffix} already exists at {target_path}, returning existing dataset."
+                            )
+                            logger.info(
+                                "Delete or move existing dataset or re-run search query with MPRester(force_renew=True) "
+                                "to refresh local dataset.",
+                            )
+
+                            return {
+                                "data": MPDataset(
+                                    path=target_path,
+                                    document_model=self.document_model,
+                                    use_document_model=self.use_document_model,
+                                )
+                            }
+
+                    tbl = DeltaTable(
+                        f"s3a://{bucket}/{prefix}",
+                        storage_options={
+                            "AWS_SKIP_SIGNATURE": "true",
+                            "AWS_REGION": "us-east-1",
+                        },
+                    )
+
+                    controlled_batch_str = ",".join(
+                        [f"'{tag}'" for tag in self.access_controlled_batch_ids]
+                    )
+
+                    predicate = (
+                        f"WHERE batch_id NOT IN ({controlled_batch_str})"
+                        if not has_gnome_access
+                        else ""
+                    )
+
+                    builder = QueryBuilder().register("tbl", tbl)
+
+                    # Setup progress bar
+                    num_docs_needed = tbl.count()
+
+                    if not has_gnome_access:
+                        num_docs_needed = self.count(
+                            {"batch_id_neq_any": self.access_controlled_batch_ids}
+                        )
+
+                    pbar = (
+                        tqdm(
+                            desc=pbar_message,
+                            total=num_docs_needed,
+                        )
+                        if not self.mute_progress_bars
+                        else None
+                    )
+
+                    iterator = builder.execute(f"SELECT * FROM tbl {predicate}")
+
+                    file_options = ds.ParquetFileFormat().make_write_options(
+                        compression="zstd"
+                    )
+
+                    def _flush(
+                        accumulator: list[pa.RecordBatch], group: int, schema: pa.Schema
+                    ):
+                        # somewhere post datafusion 51.0.0 and arrow-rs 57.0.0
+                        # casts to *View types began, need to cast back to base schema
+                        # -> pyarrow is behind on implementation support for *View types
+                        tbl = (
+                            pa.Table.from_batches(accumulator)
+                            .select(schema.names)
+                            .cast(target_schema=schema)
+                        )
+
+                        ds.write_dataset(
+                            tbl,
+                            base_dir=target_path,
+                            format="parquet",
+                            basename_template=f"group-{group}-"
+                            + "part-{i}.zstd.parquet",
+                            existing_data_behavior="overwrite_or_ignore",
+                            max_rows_per_group=1024,
+                            file_options=file_options,
+                        )
+
+                    group = 1
+                    size = 0
+                    accumulator = []
+                    schema = pa.schema(arrowize(self.document_model))
+                    for page in iterator:
+                        # arro3 rb to pyarrow rb for compat w/ pyarrow ds writer
+                        rg = pa.record_batch(page)
+                        accumulator.append(rg)
+                        page_size = page.num_rows
+                        size += rg.get_total_buffer_size()
+
+                        if pbar is not None:
+                            pbar.update(page_size)
+
+                        if size >= MAPI_CLIENT_SETTINGS.DATASET_FLUSH_THRESHOLD:
+                            _flush(accumulator, group, schema)
+                            group += 1
+                            size = 0
+                            accumulator.clear()
+
+                    if accumulator:
+                        _flush(accumulator, group + 1, schema)
+
+                    if pbar is not None:
+                        pbar.close()
+
+                    logger.info(f"Dataset for {suffix} written to {target_path}")
+                    logger.info("Converting to DeltaTable...")
+
+                    convert_to_deltalake(target_path)
+
+                    logger.info(
+                        "Consult the delta-rs and pyarrow documentation for advanced usage: "
+                        "delta-io.github.io/delta-rs, arrow.apache.org/docs/python"
+                    )
+
+                    return {
+                        "data": MPDataset(
+                            path=target_path,
+                            document_model=self.document_model,
+                            use_document_model=self.use_document_model,
+                        )
+                    }
+
+                # Paginate over all entries in the bucket.
+                # TODO: change when a subset of entries needed from DB
                 paginator = self.s3_client.get_paginator("list_objects_v2")
                 pages = paginator.paginate(Bucket=bucket, Prefix=prefix)
 
@@ -514,11 +726,6 @@ def _query_resource(
                 }
 
                 # Setup progress bar
-                pbar_message = (  # type: ignore
-                    f"Retrieving {self.document_model.__name__} documents"  # type: ignore
-                    if self.document_model is not None
-                    else "Retrieving documents"
-                )
                 num_docs_needed = int(self.count())
                 pbar = (
                     tqdm(
@@ -1365,6 +1572,8 @@ def __getattr__(self, v: str):
                     use_document_model=self.use_document_model,
                     headers=self.headers,
                     mute_progress_bars=self.mute_progress_bars,
+                    local_dataset_cache=self.local_dataset_cache,
+                    force_renew=self.force_renew,
                 )
             return self.sub_resters[v]
 
diff --git a/mp_api/client/core/exceptions.py b/mp_api/client/core/exceptions.py
index fa9f8793..45cef802 100644
--- a/mp_api/client/core/exceptions.py
+++ b/mp_api/client/core/exceptions.py
@@ -1,4 +1,5 @@
 """Define custom exceptions and warnings for the client."""
+
 from __future__ import annotations
 
 
@@ -8,3 +9,15 @@ class MPRestError(Exception):
 
 class MPRestWarning(Warning):
     """Raised when a query is malformed but interpretable."""
+
+
+class MPDatasetIndexingWarning(Warning):
+    """Raised during sub-optimal indexing of MPDatasets."""
+
+
+class MPDatasetSlicingWarning(Warning):
+    """Raised during sub-optimal slicing of MPDatasets."""
+
+
+class MPDatasetIterationWarning(Warning):
+    """Raised during sub-optimal iteration of MPDatasets."""
diff --git a/mp_api/client/core/settings.py b/mp_api/client/core/settings.py
index f5818d57..9a7e0852 100644
--- a/mp_api/client/core/settings.py
+++ b/mp_api/client/core/settings.py
@@ -1,4 +1,5 @@
 import os
+from pathlib import Path
 
 from emmet.core.settings import EmmetSettings
 from pydantic import Field, field_validator
@@ -47,6 +48,7 @@ class MAPIClientSettings(BaseSettings):
             "condition_mixing_media",
             "condition_heating_atmosphere",
             "operations",
+            "batch_id_neq_any",
             "_fields",
         ],
         description="List API query parameters that do not support parallel requests.",
@@ -101,6 +103,16 @@ class MAPIClientSettings(BaseSettings):
         description="Angle tolerance for structure matching in degrees.",
     )
 
+    LOCAL_DATASET_CACHE: Path = Field(
+        Path("~/mp_datasets").expanduser(),
+        description="Target directory for downloading full datasets",
+    )
+
+    DATASET_FLUSH_THRESHOLD: int = Field(
+        int(2.75 * 1024**3),
+        description="Threshold bytes to accumulate in memory before flushing dataset to disk",
+    )
+
     model_config = SettingsConfigDict(env_prefix="MPRESTER_")
 
     @field_validator("ENDPOINT", mode="before")
diff --git a/mp_api/client/core/utils.py b/mp_api/client/core/utils.py
index 935e1453..82996a93 100644
--- a/mp_api/client/core/utils.py
+++ b/mp_api/client/core/utils.py
@@ -2,22 +2,35 @@
 
 import os
 import warnings
+from functools import cached_property
 from importlib import import_module
+from itertools import chain
 from typing import TYPE_CHECKING, Literal
 from urllib.parse import urljoin
 
 import orjson
+import pyarrow.dataset as ds
+from deltalake import DeltaTable
 from emmet.core import __version__ as _EMMET_CORE_VER
 from emmet.core.mpid_ext import validate_identifier
 from monty.json import MontyDecoder
 from packaging.version import parse as parse_version
 
-from mp_api.client.core.exceptions import MPRestError, MPRestWarning
+from mp_api.client.core.exceptions import (
+    MPDatasetIndexingWarning,
+    MPDatasetIterationWarning,
+    MPDatasetSlicingWarning,
+    MPRestError,
+    MPRestWarning,
+)
 from mp_api.client.core.settings import MAPI_CLIENT_SETTINGS
 
 if TYPE_CHECKING:
+    from pathlib import Path
     from typing import Any
 
+    from pydantic._internal._model_construction import ModelMetaclass
+
 
 def _compare_emmet_ver(
     ref_version: str, op: Literal["==", ">", ">=", "<", "<="]
@@ -229,3 +242,115 @@ def __getattr__(self, v: str) -> Any:
             self._load()
         if hasattr(self._imported, v):
             return getattr(self._imported, v)
+
+
+class MPDataset:
+    """Convenience wrapper for pyarrow datasets stored on disk."""
+
+    def __init__(
+        self,
+        path: Path,
+        document_model: ModelMetaclass,
+        use_document_model: bool,
+    ):
+        """Initialize a MPDataset.
+
+        Parameters
+        -----------
+        path: Path | str
+            A path-like string.
+        document_model: ModelMetaclass
+            Pydantic document model for use during de-serialization of arrow data
+        use_document_model: bool
+            Use 'document_model' during de-serialization of arrow data.
+        """
+        self._start = 0
+        self._path = path
+        self._document_model = document_model
+        self._dataset = ds.dataset(path)
+        self._row_groups = list(
+            chain.from_iterable(
+                [
+                    fragment.split_by_row_group()
+                    for fragment in self._dataset.get_fragments()
+                ]
+            )
+        )
+        self._use_document_model = use_document_model
+
+    @property
+    def pyarrow_dataset(self) -> ds.Dataset:
+        return self._dataset
+
+    @property
+    def pydantic_model(self) -> ModelMetaclass:
+        return self._document_model
+
+    @property
+    def use_document_model(self) -> bool:
+        return self._use_document_model
+
+    @use_document_model.setter
+    def use_document_model(self, value: bool):
+        self._use_document_model = value
+
+    @cached_property
+    def delta_table(self) -> DeltaTable:
+        return DeltaTable(self._path)
+
+    @cached_property
+    def num_chunks(self) -> int:
+        return len(self._row_groups)
+
+    def __getitem__(self, idx):
+        if isinstance(idx, slice):
+            warnings.warn(
+                """
+                Pythonic slicing of arrow-based MPDatasets is sub-optimal, consider using
+                idiomatic arrow patterns. See MP's docs on MPDatasets for relevant examples:
+                docs.materialsproject.org/downloading-data/arrow-datasets
+                """,
+                MPDatasetSlicingWarning,
+                stacklevel=2,
+            )
+            start, stop, step = idx.indices(len(self))
+            _take = list(range(start, stop, step))
+            ds_slice = self._dataset.take(_take).to_pylist(maps_as_pydicts="strict")
+            return (
+                [self._document_model(**_row) for _row in ds_slice]
+                if self._use_document_model
+                else ds_slice
+            )
+
+        warnings.warn(
+            """
+            Pythonic indexing into arrow-based MPDatasets is sub-optimal, consider using
+            idiomatic arrow patterns. See MP's docs on MPDatasets for relevant examples:
+            docs.materialsproject.org/downloading-data/arrow-datasets
+            """,
+            MPDatasetIndexingWarning,
+            stacklevel=2,
+        )
+        _row = self._dataset.take([idx]).to_pylist(maps_as_pydicts="strict")[0]
+        return self._document_model(**_row) if self._use_document_model else _row
+
+    def __len__(self) -> int:
+        return self._dataset.count_rows()
+
+    def __iter__(self):
+        with warnings.catch_warnings(
+            action="ignore", category=MPDatasetIndexingWarning
+        ):
+            warnings.warn(
+                """
+                Iterating through arrow-based MPDatasets is sub-optimal, consider using
+                idiomatic arrow patterns. See MP's docs on MPDatasets for relevant examples:
+                docs.materialsproject.org/downloading-data/arrow-datasets
+                """,
+                MPDatasetIterationWarning,
+                stacklevel=2,
+            )
+            current = self._start
+            while current < len(self):
+                yield self[current]
+                current += 1
diff --git a/mp_api/client/mprester.py b/mp_api/client/mprester.py
index 1d9afc5c..3dd81b3c 100644
--- a/mp_api/client/mprester.py
+++ b/mp_api/client/mprester.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import itertools
+import os
 import warnings
 from collections import defaultdict
 from functools import cache, lru_cache
@@ -82,6 +83,10 @@ def __init__(
         session: Session | None = None,
         headers: dict | None = None,
         mute_progress_bars: bool = MAPI_CLIENT_SETTINGS.MUTE_PROGRESS_BARS,
+        local_dataset_cache: (
+            str | os.PathLike
+        ) = MAPI_CLIENT_SETTINGS.LOCAL_DATASET_CACHE,
+        force_renew: bool = False,
         **kwargs,
     ):
         """Initialize the MPRester.
@@ -116,6 +121,9 @@ def __init__(
             session: Session object to use. By default (None), the client will create one.
             headers: Custom headers for localhost connections.
             mute_progress_bars:  Whether to mute progress bars.
+            local_dataset_cache: Target directory for downloading full datasets. Defaults
+                to "mp_datasets" in the user's home directory
+            force_renew: Option to overwrite existing local dataset
             **kwargs: access to legacy kwargs that may be in the process of being deprecated
         """
         self.api_key = validate_api_key(api_key)
@@ -131,6 +139,8 @@ def __init__(
         self._include_user_agent = include_user_agent
         self.use_document_model = use_document_model
         self.mute_progress_bars = mute_progress_bars
+        self.local_dataset_cache = local_dataset_cache
+        self.force_renew = force_renew
         self._contribs = None
 
         self._deprecated_attributes = [
@@ -205,6 +215,8 @@ def __init__(
                         use_document_model=self.use_document_model,
                         headers=self.headers,
                         mute_progress_bars=self.mute_progress_bars,
+                        local_dataset_cache=self.local_dataset_cache,
+                        force_renew=self.force_renew,
                     ),
                 )
 
diff --git a/mp_api/client/routes/materials/tasks.py b/mp_api/client/routes/materials/tasks.py
index 4e8498c9..fdf391a9 100644
--- a/mp_api/client/routes/materials/tasks.py
+++ b/mp_api/client/routes/materials/tasks.py
@@ -3,8 +3,11 @@
 from datetime import datetime
 from typing import TYPE_CHECKING
 
+import pyarrow as pa
+from deltalake import DeltaTable, QueryBuilder
 from emmet.core.mpid import MPID, AlphaID
 from emmet.core.tasks import CoreTaskDoc
+from emmet.core.trajectory import RelaxTrajectory
 
 from mp_api.client.core import BaseRester, MPRestError
 from mp_api.client.core.utils import validate_ids
@@ -19,8 +22,9 @@ class TaskRester(BaseRester):
     suffix: str = "materials/tasks"
     document_model: type[BaseModel] = CoreTaskDoc  # type: ignore
     primary_key: str = "task_id"
+    delta_backed = True
 
-    def get_trajectory(self, task_id: MPID | AlphaID | str) -> list[dict[str, Any]]:
+    def get_trajectory(self, task_id: MPID | AlphaID | str) -> dict[str, Any]:
         """Returns a Trajectory object containing the geometry of the
         material throughout a calculation. This is most useful for
         observing how a material relaxes during a geometry optimization.
@@ -29,20 +33,31 @@ def get_trajectory(self, task_id: MPID | AlphaID | str) -> list[dict[str, Any]]:
             task_id (str, MPID, AlphaID): Task ID
 
         Returns:
-            list of dict representing emmet.core.trajectory.Trajectory
+            dict representing emmet.core.trajectory.RelaxTrajectory
         """
-        traj_data = self._query_resource_data(
-            {"task_ids": [AlphaID(task_id).string]},
-            suburl="trajectory/",
-            use_document_model=False,
-        )[0].get(
-            "trajectories", None
-        )  # type: ignore
-
-        if traj_data is None:
+        as_alpha = str(AlphaID(task_id, padlen=8)).split("-")[-1]
+        traj_tbl = DeltaTable(
+            "s3a://materialsproject-parsed/core/trajectories/",
+            storage_options={"AWS_SKIP_SIGNATURE": "true", "AWS_REGION": "us-east-1"},
+        )
+
+        traj_data = pa.table(
+            QueryBuilder()
+            .register("traj", traj_tbl)
+            .execute(
+                f"""
+                SELECT *
+                FROM   traj
+                WHERE  identifier='{as_alpha}'
+                """
+            )
+            .read_all()
+        ).to_pylist(maps_as_pydicts="strict")
+
+        if not traj_data:
             raise MPRestError(f"No trajectory data for {task_id} found")
 
-        return traj_data
+        return RelaxTrajectory(**traj_data[0]).model_dump()
 
     def search(
         self,
diff --git a/pyproject.toml b/pyproject.toml
index d91f4029..a28c6122 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -27,6 +27,8 @@ dependencies = [
   "emmet-core>=0.86.3",
   "boto3",
   "orjson >= 3.10,<4",
+  "pyarrow >= 20.0.0",
+  "deltalake >= 1.4.0",
 ]
 dynamic = ["version"]
 
diff --git a/requirements/requirements-ubuntu-latest_py3.11.txt b/requirements/requirements-ubuntu-latest_py3.11.txt
index b83dc92a..2769b72b 100644
--- a/requirements/requirements-ubuntu-latest_py3.11.txt
+++ b/requirements/requirements-ubuntu-latest_py3.11.txt
@@ -6,13 +6,15 @@
 #
 annotated-types==0.7.0
     # via pydantic
+arro3-core==0.6.5
+    # via deltalake
 bibtexparser==1.4.4
     # via pymatgen
 blake3==1.0.8
     # via emmet-core
-boto3==1.42.38
+boto3==1.42.45
     # via mp-api (pyproject.toml)
-botocore==1.42.38
+botocore==1.42.45
     # via
     #   boto3
     #   s3transfer
@@ -24,6 +26,10 @@ contourpy==1.3.3
     # via matplotlib
 cycler==0.12.1
     # via matplotlib
+deltalake==1.4.2
+    # via mp-api (pyproject.toml)
+deprecated==1.3.1
+    # via deltalake
 emmet-core==0.86.3
     # via mp-api (pyproject.toml)
 fonttools==4.61.1
@@ -49,11 +55,11 @@ monty==2025.3.3
     #   pymatgen
 mpmath==1.3.0
     # via sympy
-narwhals==2.15.0
+narwhals==2.16.0
     # via plotly
 networkx==3.6.1
     # via pymatgen
-numpy==2.4.1
+numpy==2.4.2
     # via
     #   contourpy
     #   matplotlib
@@ -63,7 +69,7 @@ numpy==2.4.1
     #   pymatgen-io-validation
     #   scipy
     #   spglib
-orjson==3.11.6
+orjson==3.11.7
     # via
     #   mp-api (pyproject.toml)
     #   pymatgen
@@ -79,6 +85,8 @@ pillow==12.1.0
     # via matplotlib
 plotly==6.5.2
     # via pymatgen
+pyarrow==23.0.0
+    # via mp-api (pyproject.toml)
 pybtex==0.25.1
     # via emmet-core
 pydantic==2.12.5
@@ -133,10 +141,11 @@ sympy==1.14.0
     # via pymatgen
 tabulate==0.9.0
     # via pymatgen
-tqdm==4.67.1
+tqdm==4.67.3
     # via pymatgen
 typing-extensions==4.15.0
     # via
+    #   arro3-core
     #   blake3
     #   emmet-core
     #   mp-api (pyproject.toml)
@@ -154,3 +163,5 @@ urllib3==2.6.3
     # via
     #   botocore
     #   requests
+wrapt==2.1.1
+    # via deprecated
diff --git a/requirements/requirements-ubuntu-latest_py3.11_extras.txt b/requirements/requirements-ubuntu-latest_py3.11_extras.txt
index ffc1a886..0f35bc7c 100644
--- a/requirements/requirements-ubuntu-latest_py3.11_extras.txt
+++ b/requirements/requirements-ubuntu-latest_py3.11_extras.txt
@@ -14,6 +14,8 @@ anyio==4.12.1
     #   mcp
     #   sse-starlette
     #   starlette
+arro3-core==0.6.5
+    # via deltalake
 arrow==1.4.0
     # via isoduration
 ase==3.27.0
@@ -25,9 +27,9 @@ attrs==25.4.0
     #   cyclopts
     #   jsonschema
     #   referencing
-authlib==1.6.6
+authlib==1.6.7
     # via fastmcp
-babel==2.17.0
+babel==2.18.0
     # via sphinx
 backports-tarfile==1.2.0
     # via jaraco-context
@@ -41,9 +43,9 @@ blake3==1.0.8
     # via emmet-core
 boltons==25.0.0
     # via mpcontribs-client
-boto3==1.42.38
+boto3==1.42.45
     # via mp-api (pyproject.toml)
-botocore==1.42.38
+botocore==1.42.45
     # via
     #   boto3
     #   s3transfer
@@ -51,7 +53,7 @@ bravado==12.0.1
     # via mpcontribs-client
 bravado-core==6.1.1
     # via bravado
-cachetools==6.2.6
+cachetools==7.0.0
     # via
     #   mpcontribs-client
     #   py-key-value-aio
@@ -74,8 +76,10 @@ cloudpickle==3.1.2
     # via pydocket
 contourpy==1.3.3
     # via matplotlib
-coverage[toml]==7.13.2
+coverage[toml]==7.13.4
     # via pytest-cov
+croniter==6.0.0
+    # via pydocket
 cryptography==46.0.4
     # via
     #   authlib
@@ -89,6 +93,10 @@ cyclopts==4.5.1
     # via fastmcp
 decorator==5.2.1
     # via ipython
+deltalake==1.4.2
+    # via mp-api (pyproject.toml)
+deprecated==1.3.1
+    # via deltalake
 diskcache==5.6.3
     # via py-key-value-aio
 distlib==0.4.0
@@ -116,7 +124,7 @@ executing==2.2.1
     # via stack-data
 fakeredis[lua]==2.33.0
     # via pydocket
-fastmcp==2.14.4
+fastmcp==2.14.5
     # via mp-api (pyproject.toml)
 filelock==3.20.3
     # via virtualenv
@@ -169,7 +177,7 @@ inflect==7.5.0
     # via robocrys
 iniconfig==2.3.0
     # via pytest
-ipython==9.9.0
+ipython==9.10.0
     # via mpcontribs-client
 ipython-pygments-lexers==1.1.1
     # via ipython
@@ -268,7 +276,7 @@ more-itertools==10.8.0
     #   jaraco-functools
 mp-pyrho==0.5.1
     # via pymatgen-analysis-defects
-mpcontribs-client==5.10.4
+mpcontribs-client==5.10.5
     # via mp-api (pyproject.toml)
 mpmath==1.3.0
     # via sympy
@@ -282,7 +290,7 @@ mypy-extensions==1.1.0
     # via
     #   mp-api (pyproject.toml)
     #   mypy
-narwhals==2.15.0
+narwhals==2.16.0
     # via plotly
 networkx==3.6.1
     # via
@@ -291,7 +299,7 @@ networkx==3.6.1
     #   scikit-image
 nodeenv==1.10.0
     # via pre-commit
-numpy==2.4.1
+numpy==2.4.2
     # via
     #   ase
     #   contourpy
@@ -317,23 +325,8 @@ numpy==2.4.1
 openapi-pydantic==0.5.1
     # via fastmcp
 opentelemetry-api==1.39.1
-    # via
-    #   opentelemetry-exporter-prometheus
-    #   opentelemetry-instrumentation
-    #   opentelemetry-sdk
-    #   opentelemetry-semantic-conventions
-    #   pydocket
-opentelemetry-exporter-prometheus==0.60b1
     # via pydocket
-opentelemetry-instrumentation==0.60b1
-    # via pydocket
-opentelemetry-sdk==1.39.1
-    # via opentelemetry-exporter-prometheus
-opentelemetry-semantic-conventions==0.60b1
-    # via
-    #   opentelemetry-instrumentation
-    #   opentelemetry-sdk
-orjson==3.11.6
+orjson==3.11.7
     # via
     #   mp-api (pyproject.toml)
     #   pymatgen
@@ -342,7 +335,6 @@ packaging==26.0
     #   fastmcp
     #   lazy-loader
     #   matplotlib
-    #   opentelemetry-instrumentation
     #   plotly
     #   pytest
     #   scikit-image
@@ -355,7 +347,7 @@ pandas==2.3.3
     #   mpcontribs-client
     #   pymatgen
     #   seaborn
-parso==0.8.5
+parso==0.8.6
     # via jedi
 pathable==0.4.4
     # via jsonschema-path
@@ -388,9 +380,7 @@ pluggy==1.6.0
 pre-commit==4.5.1
     # via mp-api (pyproject.toml)
 prometheus-client==0.24.1
-    # via
-    #   opentelemetry-exporter-prometheus
-    #   pydocket
+    # via pydocket
 prompt-toolkit==3.0.52
     # via ipython
 psutil==7.2.2
@@ -408,7 +398,9 @@ py-key-value-aio[disk,keyring,memory,redis]==0.3.0
 py-key-value-shared==0.3.0
     # via py-key-value-aio
 pyarrow==23.0.0
-    # via emmet-core
+    # via
+    #   emmet-core
+    #   mp-api (pyproject.toml)
 pybtex==0.25.1
     # via
     #   emmet-core
@@ -434,7 +426,7 @@ pydantic-settings==2.12.0
     #   emmet-core
     #   mcp
     #   pymatgen-io-validation
-pydocket==0.16.6
+pydocket==0.17.5
     # via fastmcp
 pyflakes==3.4.0
     # via flake8
@@ -447,7 +439,7 @@ pygments==2.19.2
     #   sphinx
 pyisemail==2.0.1
     # via mpcontribs-client
-pyjwt[crypto]==2.10.1
+pyjwt[crypto]==2.11.0
     # via mcp
 pymatgen==2025.10.7
     # via
@@ -500,6 +492,7 @@ python-dateutil==2.9.0.post0
     #   botocore
     #   bravado
     #   bravado-core
+    #   croniter
     #   matplotlib
     #   pandas
 python-dotenv==1.2.1
@@ -513,6 +506,7 @@ python-multipart==0.0.22
 pytz==2025.2
     # via
     #   bravado-core
+    #   croniter
     #   pandas
 pyyaml==6.0.3
     # via
@@ -522,7 +516,7 @@ pyyaml==6.0.3
     #   pre-commit
     #   pybtex
     #   swagger-spec-validator
-redis==7.1.0
+redis==7.1.1
     # via
     #   fakeredis
     #   py-key-value-aio
@@ -551,7 +545,7 @@ rfc3986-validator==0.1.1
     # via jsonschema
 rfc3987-syntax==1.1.0
     # via jsonschema
-rich==14.3.1
+rich==14.3.2
     # via
     #   cyclopts
     #   fastmcp
@@ -591,10 +585,8 @@ seaborn==0.13.2
     # via pymatgen-analysis-diffusion
 secretstorage==3.5.0
     # via keyring
-seekpath==2.2.0
+seekpath==2.2.1
     # via emmet-core
-semantic-version==2.10.0
-    # via mpcontribs-client
 shapely==2.1.2
     # via pymatgen-analysis-alloys
 shellingham==1.5.4
@@ -655,7 +647,7 @@ threadpoolctl==3.6.0
     # via scikit-learn
 tifffile==2026.1.28
     # via scikit-image
-tqdm==4.67.1
+tqdm==4.67.3
     # via
     #   matminer
     #   mpcontribs-client
@@ -670,11 +662,12 @@ typer==0.21.1
     # via pydocket
 types-requests==2.32.4.20260107
     # via mp-api (pyproject.toml)
-types-setuptools==80.10.0.20260124
+types-setuptools==81.0.0.20260209
     # via mp-api (pyproject.toml)
 typing-extensions==4.15.0
     # via
     #   anyio
+    #   arro3-core
     #   blake3
     #   bravado
     #   emmet-core
@@ -686,8 +679,6 @@ typing-extensions==4.15.0
     #   mp-api (pyproject.toml)
     #   mypy
     #   opentelemetry-api
-    #   opentelemetry-sdk
-    #   opentelemetry-semantic-conventions
     #   pint
     #   py-key-value-shared
     #   pydantic
@@ -727,13 +718,13 @@ uvicorn==0.40.0
     #   mcp
 virtualenv==20.36.1
     # via pre-commit
-wcwidth==0.5.2
+wcwidth==0.6.0
     # via prompt-toolkit
 webcolors==25.10.0
     # via jsonschema
 websockets==16.0
     # via fastmcp
-wrapt==1.17.3
-    # via opentelemetry-instrumentation
+wrapt==2.1.1
+    # via deprecated
 zipp==3.23.0
     # via importlib-metadata
diff --git a/requirements/requirements-ubuntu-latest_py3.12.txt b/requirements/requirements-ubuntu-latest_py3.12.txt
index 9822afda..6bdfdf4a 100644
--- a/requirements/requirements-ubuntu-latest_py3.12.txt
+++ b/requirements/requirements-ubuntu-latest_py3.12.txt
@@ -6,13 +6,15 @@
 #
 annotated-types==0.7.0
     # via pydantic
+arro3-core==0.6.5
+    # via deltalake
 bibtexparser==1.4.4
     # via pymatgen
 blake3==1.0.8
     # via emmet-core
-boto3==1.42.38
+boto3==1.42.45
     # via mp-api (pyproject.toml)
-botocore==1.42.38
+botocore==1.42.45
     # via
     #   boto3
     #   s3transfer
@@ -24,6 +26,10 @@ contourpy==1.3.3
     # via matplotlib
 cycler==0.12.1
     # via matplotlib
+deltalake==1.4.2
+    # via mp-api (pyproject.toml)
+deprecated==1.3.1
+    # via deltalake
 emmet-core==0.86.3
     # via mp-api (pyproject.toml)
 fonttools==4.61.1
@@ -49,11 +55,11 @@ monty==2025.3.3
     #   pymatgen
 mpmath==1.3.0
     # via sympy
-narwhals==2.15.0
+narwhals==2.16.0
     # via plotly
 networkx==3.6.1
     # via pymatgen
-numpy==2.4.1
+numpy==2.4.2
     # via
     #   contourpy
     #   matplotlib
@@ -63,7 +69,7 @@ numpy==2.4.1
     #   pymatgen-io-validation
     #   scipy
     #   spglib
-orjson==3.11.6
+orjson==3.11.7
     # via
     #   mp-api (pyproject.toml)
     #   pymatgen
@@ -79,6 +85,8 @@ pillow==12.1.0
     # via matplotlib
 plotly==6.5.2
     # via pymatgen
+pyarrow==23.0.0
+    # via mp-api (pyproject.toml)
 pybtex==0.25.1
     # via emmet-core
 pydantic==2.12.5
@@ -133,7 +141,7 @@ sympy==1.14.0
     # via pymatgen
 tabulate==0.9.0
     # via pymatgen
-tqdm==4.67.1
+tqdm==4.67.3
     # via pymatgen
 typing-extensions==4.15.0
     # via
@@ -153,3 +161,5 @@ urllib3==2.6.3
     # via
     #   botocore
     #   requests
+wrapt==2.1.1
+    # via deprecated
diff --git a/requirements/requirements-ubuntu-latest_py3.12_extras.txt b/requirements/requirements-ubuntu-latest_py3.12_extras.txt
index 6c0f7e0e..d6ae9c46 100644
--- a/requirements/requirements-ubuntu-latest_py3.12_extras.txt
+++ b/requirements/requirements-ubuntu-latest_py3.12_extras.txt
@@ -14,6 +14,8 @@ anyio==4.12.1
     #   mcp
     #   sse-starlette
     #   starlette
+arro3-core==0.6.5
+    # via deltalake
 arrow==1.4.0
     # via isoduration
 ase==3.27.0
@@ -25,9 +27,9 @@ attrs==25.4.0
     #   cyclopts
     #   jsonschema
     #   referencing
-authlib==1.6.6
+authlib==1.6.7
     # via fastmcp
-babel==2.17.0
+babel==2.18.0
     # via sphinx
 beartype==0.22.9
     # via
@@ -39,9 +41,9 @@ blake3==1.0.8
     # via emmet-core
 boltons==25.0.0
     # via mpcontribs-client
-boto3==1.42.38
+boto3==1.42.45
     # via mp-api (pyproject.toml)
-botocore==1.42.38
+botocore==1.42.45
     # via
     #   boto3
     #   s3transfer
@@ -49,7 +51,7 @@ bravado==12.0.1
     # via mpcontribs-client
 bravado-core==6.1.1
     # via bravado
-cachetools==6.2.6
+cachetools==7.0.0
     # via
     #   mpcontribs-client
     #   py-key-value-aio
@@ -72,8 +74,10 @@ cloudpickle==3.1.2
     # via pydocket
 contourpy==1.3.3
     # via matplotlib
-coverage[toml]==7.13.2
+coverage[toml]==7.13.4
     # via pytest-cov
+croniter==6.0.0
+    # via pydocket
 cryptography==46.0.4
     # via
     #   authlib
@@ -87,6 +91,10 @@ cyclopts==4.5.1
     # via fastmcp
 decorator==5.2.1
     # via ipython
+deltalake==1.4.2
+    # via mp-api (pyproject.toml)
+deprecated==1.3.1
+    # via deltalake
 diskcache==5.6.3
     # via py-key-value-aio
 distlib==0.4.0
@@ -114,7 +122,7 @@ executing==2.2.1
     # via stack-data
 fakeredis[lua]==2.33.0
     # via pydocket
-fastmcp==2.14.4
+fastmcp==2.14.5
     # via mp-api (pyproject.toml)
 filelock==3.20.3
     # via virtualenv
@@ -165,7 +173,7 @@ inflect==7.5.0
     # via robocrys
 iniconfig==2.3.0
     # via pytest
-ipython==9.9.0
+ipython==9.10.0
     # via mpcontribs-client
 ipython-pygments-lexers==1.1.1
     # via ipython
@@ -264,7 +272,7 @@ more-itertools==10.8.0
     #   jaraco-functools
 mp-pyrho==0.5.1
     # via pymatgen-analysis-defects
-mpcontribs-client==5.10.4
+mpcontribs-client==5.10.5
     # via mp-api (pyproject.toml)
 mpmath==1.3.0
     # via sympy
@@ -278,7 +286,7 @@ mypy-extensions==1.1.0
     # via
     #   mp-api (pyproject.toml)
     #   mypy
-narwhals==2.15.0
+narwhals==2.16.0
     # via plotly
 networkx==3.6.1
     # via
@@ -287,7 +295,7 @@ networkx==3.6.1
     #   scikit-image
 nodeenv==1.10.0
     # via pre-commit
-numpy==2.4.1
+numpy==2.4.2
     # via
     #   ase
     #   contourpy
@@ -313,23 +321,8 @@ numpy==2.4.1
 openapi-pydantic==0.5.1
     # via fastmcp
 opentelemetry-api==1.39.1
-    # via
-    #   opentelemetry-exporter-prometheus
-    #   opentelemetry-instrumentation
-    #   opentelemetry-sdk
-    #   opentelemetry-semantic-conventions
-    #   pydocket
-opentelemetry-exporter-prometheus==0.60b1
     # via pydocket
-opentelemetry-instrumentation==0.60b1
-    # via pydocket
-opentelemetry-sdk==1.39.1
-    # via opentelemetry-exporter-prometheus
-opentelemetry-semantic-conventions==0.60b1
-    # via
-    #   opentelemetry-instrumentation
-    #   opentelemetry-sdk
-orjson==3.11.6
+orjson==3.11.7
     # via
     #   mp-api (pyproject.toml)
     #   pymatgen
@@ -338,7 +331,6 @@ packaging==26.0
     #   fastmcp
     #   lazy-loader
     #   matplotlib
-    #   opentelemetry-instrumentation
     #   plotly
     #   pytest
     #   scikit-image
@@ -351,7 +343,7 @@ pandas==2.3.3
     #   mpcontribs-client
     #   pymatgen
     #   seaborn
-parso==0.8.5
+parso==0.8.6
     # via jedi
 pathable==0.4.4
     # via jsonschema-path
@@ -384,9 +376,7 @@ pluggy==1.6.0
 pre-commit==4.5.1
     # via mp-api (pyproject.toml)
 prometheus-client==0.24.1
-    # via
-    #   opentelemetry-exporter-prometheus
-    #   pydocket
+    # via pydocket
 prompt-toolkit==3.0.52
     # via ipython
 psutil==7.2.2
@@ -404,7 +394,9 @@ py-key-value-aio[disk,keyring,memory,redis]==0.3.0
 py-key-value-shared==0.3.0
     # via py-key-value-aio
 pyarrow==23.0.0
-    # via emmet-core
+    # via
+    #   emmet-core
+    #   mp-api (pyproject.toml)
 pybtex==0.25.1
     # via
     #   emmet-core
@@ -430,7 +422,7 @@ pydantic-settings==2.12.0
     #   emmet-core
     #   mcp
     #   pymatgen-io-validation
-pydocket==0.16.6
+pydocket==0.17.5
     # via fastmcp
 pyflakes==3.4.0
     # via flake8
@@ -443,7 +435,7 @@ pygments==2.19.2
     #   sphinx
 pyisemail==2.0.1
     # via mpcontribs-client
-pyjwt[crypto]==2.10.1
+pyjwt[crypto]==2.11.0
     # via mcp
 pymatgen==2025.10.7
     # via
@@ -496,6 +488,7 @@ python-dateutil==2.9.0.post0
     #   botocore
     #   bravado
     #   bravado-core
+    #   croniter
     #   matplotlib
     #   pandas
 python-dotenv==1.2.1
@@ -509,6 +502,7 @@ python-multipart==0.0.22
 pytz==2025.2
     # via
     #   bravado-core
+    #   croniter
     #   pandas
 pyyaml==6.0.3
     # via
@@ -518,7 +512,7 @@ pyyaml==6.0.3
     #   pre-commit
     #   pybtex
     #   swagger-spec-validator
-redis==7.1.0
+redis==7.1.1
     # via
     #   fakeredis
     #   py-key-value-aio
@@ -547,7 +541,7 @@ rfc3986-validator==0.1.1
     # via jsonschema
 rfc3987-syntax==1.1.0
     # via jsonschema
-rich==14.3.1
+rich==14.3.2
     # via
     #   cyclopts
     #   fastmcp
@@ -587,10 +581,8 @@ seaborn==0.13.2
     # via pymatgen-analysis-diffusion
 secretstorage==3.5.0
     # via keyring
-seekpath==2.2.0
+seekpath==2.2.1
     # via emmet-core
-semantic-version==2.10.0
-    # via mpcontribs-client
 shapely==2.1.2
     # via pymatgen-analysis-alloys
 shellingham==1.5.4
@@ -651,7 +643,7 @@ threadpoolctl==3.6.0
     # via scikit-learn
 tifffile==2026.1.28
     # via scikit-image
-tqdm==4.67.1
+tqdm==4.67.3
     # via
     #   matminer
     #   mpcontribs-client
@@ -666,7 +658,7 @@ typer==0.21.1
     # via pydocket
 types-requests==2.32.4.20260107
     # via mp-api (pyproject.toml)
-types-setuptools==80.10.0.20260124
+types-setuptools==81.0.0.20260209
     # via mp-api (pyproject.toml)
 typing-extensions==4.15.0
     # via
@@ -680,8 +672,6 @@ typing-extensions==4.15.0
     #   mp-api (pyproject.toml)
     #   mypy
     #   opentelemetry-api
-    #   opentelemetry-sdk
-    #   opentelemetry-semantic-conventions
     #   pint
     #   py-key-value-shared
     #   pydantic
@@ -721,13 +711,13 @@ uvicorn==0.40.0
     #   mcp
 virtualenv==20.36.1
     # via pre-commit
-wcwidth==0.5.2
+wcwidth==0.6.0
     # via prompt-toolkit
 webcolors==25.10.0
     # via jsonschema
 websockets==16.0
     # via fastmcp
-wrapt==1.17.3
-    # via opentelemetry-instrumentation
+wrapt==2.1.1
+    # via deprecated
 zipp==3.23.0
     # via importlib-metadata
diff --git a/tests/client/materials/test_tasks.py b/tests/client/materials/test_tasks.py
index c89530a4..ea064989 100644
--- a/tests/client/materials/test_tasks.py
+++ b/tests/client/materials/test_tasks.py
@@ -1,12 +1,14 @@
 import os
-from ..conftest import client_search_testing, requires_api_key
-import pytest
 
+import pytest
 from emmet.core.mpid import MPID, AlphaID
-from emmet.core.trajectory import Trajectory
+from emmet.core.trajectory import RelaxTrajectory
 from emmet.core.utils import utcnow
+
 from mp_api.client.routes.materials.tasks import TaskRester
 
+from ..conftest import client_search_testing, requires_api_key
+
 
 @pytest.fixture
 def rester():
@@ -56,11 +58,11 @@ def test_client(rester):
 
 @pytest.mark.parametrize("mpid", ["mp-149", MPID("mp-149"), AlphaID("mp-149")])
 def test_get_trajectories(rester, mpid):
-    trajectories = [traj for traj in rester.get_trajectory(mpid)]
+    trajectory = rester.get_trajectory(mpid)
 
     expected_model_fields = {
         field_name
-        for field_name, field in Trajectory.model_fields.items()
+        for field_name, field in RelaxTrajectory.model_fields.items()
         if not field.exclude
     }
-    assert all(set(traj) == expected_model_fields for traj in trajectories)
+    assert set(trajectory) == expected_model_fields