From 4107bbd6e1a8c5b150ccf8b7a3708369050f82bd Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Wed, 9 Jul 2025 15:21:18 -0700
Subject: [PATCH 01/17] tmp: temporarily points the dandischema dependency to
 the `devendorize` branch

This commit should be dropped before the
containing PR is merged. This is a temporary
measure to test the behavior of `dandischema`
with the changes in
https://github.com/dandi/dandi-schema/pull/294
---
 setup.cfg | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/setup.cfg b/setup.cfg
index 5efe08400..9c3240a80 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -35,7 +35,7 @@ install_requires =
     # >=8.2.0: https://github.com/pallets/click/issues/2911
     click >= 7.1, <8.2.0
     click-didyoumean
-    dandischema >= 0.11.0, < 0.12.0
+    dandischema @ git+https://github.com/dandi/dandi-schema.git@devendorize
     etelemetry >= 0.2.2
     # For pydantic to be able to use type annotations like `X | None`
     eval_type_backport;  python_version < "3.10"

From af36aa028cfb60200b4c169fe7f78941dd8d13a1 Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Thu, 10 Jul 2025 21:43:46 -0700
Subject: [PATCH 02/17] feat: expand `ServerInfo` to conclude `instance_config`

---
 dandi/utils.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/dandi/utils.py b/dandi/utils.py
index 06e461fbc..caeac7ac2 100644
--- a/dandi/utils.py
+++ b/dandi/utils.py
@@ -26,6 +26,7 @@
 import types
 from typing import IO, Any, List, Optional, Protocol, TypeVar, Union
 
+from dandischema.conf import Config as InstanceConfig
 import dateutil.parser
 from multidict import MultiDict  # dependency of yarl
 from pydantic import BaseModel, Field
@@ -546,6 +547,7 @@ class ServerServices(BaseModel):
 
 
 class ServerInfo(BaseModel):
+    instance_config: InstanceConfig
     # schema_version: str
     # schema_url: str
     version: str

From 7b15519b56b759e6bdabeea045a262f5884c40fe Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Thu, 10 Jul 2025 23:07:04 -0700
Subject: [PATCH 03/17] feat: provide func to fetch server info

---
 dandi/cli/base.py | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/dandi/cli/base.py b/dandi/cli/base.py
index 30fe73247..e88a6367c 100644
--- a/dandi/cli/base.py
+++ b/dandi/cli/base.py
@@ -2,11 +2,47 @@
 import os
 
 import click
+import requests
+from yarl import URL
+
+from dandi.consts import known_instances
+from dandi.utils import ServerInfo
 
 from .. import get_logger
 
 lgr = get_logger()
 
+
+def get_server_info(dandi_id: str) -> ServerInfo:
+    """
+    Get server info from a particular DANDI instance
+
+    Parameters
+    ----------
+    dandi_id : str
+        The ID specifying the particular known DANDI instance to query for server info.
+        This is a key in the `dandi.consts.known_instances` dictionary.
+
+    Returns
+    -------
+    ServerInfo
+        An object representing the server information responded by the DANDI instance.
+
+    Raises
+    ------
+    valueError
+        If the provided `dandi_id` is not a valid key in the
+        `dandi.consts.known_instances` dictionary.
+    """
+    if dandi_id not in known_instances:
+        raise ValueError(f"Unknown DANDI instance: {dandi_id}")
+
+    info_url = str(URL(known_instances[dandi_id].api) / "info/")
+    resp = requests.get(info_url)
+    resp.raise_for_status()
+    return ServerInfo.model_validate(resp.json())
+
+
 # Aux common functionality
 
 

From e28b6e761b9c10b3b58f56c271d654cad1ffbd3a Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Fri, 11 Jul 2025 11:34:34 -0700
Subject: [PATCH 04/17] feat: provide func to bind client to server

This function binds the DANDI client
to a specific DANDI server instance so
that subsequence commands executed
by the client is executed in the context
of the DANDI sever instance
---
 dandi/cli/base.py | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/dandi/cli/base.py b/dandi/cli/base.py
index e88a6367c..81dd21f63 100644
--- a/dandi/cli/base.py
+++ b/dandi/cli/base.py
@@ -2,6 +2,7 @@
 import os
 
 import click
+from dandischema.conf import set_instance_config
 import requests
 from yarl import URL
 
@@ -43,6 +44,20 @@ def get_server_info(dandi_id: str) -> ServerInfo:
     return ServerInfo.model_validate(resp.json())
 
 
+def bind_client(server_info: ServerInfo) -> None:
+    """
+    Bind the DANDI client to a specific DANDI server instance. I.e., to set the DANDI
+    server instance as the context of subsequent command executions by the DANDI client
+
+    Parameters
+    ----------
+    server_info : ServerInfo
+        An object containing the information of the DANDI server instance to bind to.
+        This is typically obtained by calling `get_server_info()`.
+    """
+    set_instance_config(server_info.instance_config)
+
+
 # Aux common functionality
 
 

From 04f7c26207fe383ab1fcf6531cd56b0a5fdfc74a Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Fri, 11 Jul 2025 12:09:08 -0700
Subject: [PATCH 05/17] feat: provide func to initialize the DANDI client

This function should be run before a
command is executed so that it can
set the context of the execution such
as which DANDI sever instance to interact
with.
---
 dandi/cli/base.py | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/dandi/cli/base.py b/dandi/cli/base.py
index 81dd21f63..0f54a1769 100644
--- a/dandi/cli/base.py
+++ b/dandi/cli/base.py
@@ -58,6 +58,26 @@ def bind_client(server_info: ServerInfo) -> None:
     set_instance_config(server_info.instance_config)
 
 
+def init_client(dandi_id: str) -> None:
+    """
+    Initialize the DANDI client, including binding the client to a specific DANDI server
+    instance
+
+    Parameters
+    ----------
+    dandi_id : str
+        The ID specifying the particular known DANDI instance to bind the client to.
+        This is a key in the `dandi.consts.known_instances` dictionary.
+
+    Raises
+    ------
+    ValueError
+        If the provided `dandi_id` is not a valid key in the
+        `dandi.consts.known_instances` dictionary.
+    """
+    bind_client(get_server_info(dandi_id))
+
+
 # Aux common functionality
 
 

From 50a67ca9741102e86edb0c4f0d8fb24af04e0d68 Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Thu, 17 Jul 2025 01:17:01 -0700
Subject: [PATCH 06/17] feat: delay import of `dandischema.models` in
 `dandi.dandiapi`

---
 dandi/dandiapi.py | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/dandi/dandiapi.py b/dandi/dandiapi.py
index 553ec672c..cb411130b 100644
--- a/dandi/dandiapi.py
+++ b/dandi/dandiapi.py
@@ -17,7 +17,6 @@
 from typing import TYPE_CHECKING, Any, Dict, List, Optional
 
 import click
-from dandischema import models
 from pydantic import BaseModel, Field, PrivateAttr
 import requests
 import tenacity
@@ -36,7 +35,6 @@
 )
 from .exceptions import HTTP404Error, NotFoundError, SchemaVersionError
 from .keyring import keyring_lookup, keyring_save
-from .misctypes import Digest, RemoteReadableAsset
 from .utils import (
     USER_AGENT,
     check_dandi_version,
@@ -50,8 +48,11 @@
 )
 
 if TYPE_CHECKING:
+    from dandischema import models
     from typing_extensions import Self
 
+    from .misctypes import Digest, RemoteReadableAsset
+
 
 lgr = get_logger()
 
@@ -653,6 +654,8 @@ def check_schema_version(self, schema_version: str | None = None) -> None:
             uses; if not set, the schema version for the installed
             ``dandischema`` library is used
         """
+        from dandischema import models
+
         if schema_version is None:
             schema_version = models.get_schema_version()
         server_info = self.get("/info/")
@@ -1065,6 +1068,8 @@ def get_metadata(self) -> models.Dandiset:
             metadata.  Consider using `get_raw_metadata()` instead in order to
             fetch unstructured, possibly-invalid metadata.
         """
+        from dandischema import models
+
         return models.Dandiset.model_validate(self.get_raw_metadata())
 
     def get_raw_metadata(self) -> dict[str, Any]:
@@ -1469,6 +1474,8 @@ def get_metadata(self) -> models.Asset:
             valid metadata.  Consider using `get_raw_metadata()` instead in
             order to fetch unstructured, possibly-invalid metadata.
         """
+        from dandischema import models
+
         return models.Asset.model_validate(self.get_raw_metadata())
 
     def get_raw_metadata(self) -> dict[str, Any]:
@@ -1495,6 +1502,8 @@ def get_raw_digest(self, digest_type: str | models.DigestType | None = None) ->
         .. versionchanged:: 0.36.0
             Renamed from ``get_digest()`` to ``get_raw_digest()``
         """
+        from dandischema import models
+
         if digest_type is None:
             digest_type = self.digest_type.value
         elif isinstance(digest_type, models.DigestType):
@@ -1517,6 +1526,8 @@ def get_digest(self) -> Digest:
         a dandi-etag digest for blob resources or a dandi-zarr-checksum for
         Zarr resources
         """
+        from .misctypes import Digest
+
         algorithm = self.digest_type
         return Digest(algorithm=algorithm, value=self.get_raw_digest(algorithm))
 
@@ -1651,6 +1662,8 @@ def digest_type(self) -> models.DigestType:
         determined based on its underlying data: dandi-etag for blob resources,
         dandi-zarr-checksum for Zarr resources
         """
+        from dandischema import models
+
         if self.asset_type is AssetType.ZARR:
             return models.DigestType.dandi_zarr_checksum
         else:
@@ -1683,6 +1696,8 @@ def as_readable(self) -> RemoteReadableAsset:
         Returns a `Readable` instance that can be used to obtain a file-like
         object for reading bytes directly from the asset on the server
         """
+        from .misctypes import RemoteReadableAsset
+
         md = self.get_raw_metadata()
         local_prefix = self.client.api_url.lower()
         for url in md.get("contentUrl", []):
@@ -1965,6 +1980,10 @@ def from_server_data(
         cls, asset: BaseRemoteZarrAsset, data: ZarrEntryServerData
     ) -> RemoteZarrEntry:
         """:meta private:"""
+        from dandischema import models
+
+        from .misctypes import Digest
+
         return cls(
             client=asset.client,
             zarr_id=asset.zarr,

From c6aec313a5f8169fe82eccca5acdd313b169d15a Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Thu, 17 Jul 2025 13:32:18 -0700
Subject: [PATCH 07/17] feat: delay import of `dandischema.models` in
 `dandi.files.bases`

---
 dandi/files/bases.py | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/dandi/files/bases.py b/dandi/files/bases.py
index 15bc616c4..fa2754228 100644
--- a/dandi/files/bases.py
+++ b/dandi/files/bases.py
@@ -10,15 +10,12 @@
 from pathlib import Path
 import re
 from threading import Lock
-from typing import IO, Any, Generic
+from typing import IO, TYPE_CHECKING, Any, Generic
 from xml.etree.ElementTree import fromstring
 
 import dandischema
 from dandischema.consts import DANDI_SCHEMA_VERSION
 from dandischema.digests.dandietag import DandiETag
-from dandischema.models import BareAsset, CommonModel
-from dandischema.models import Dandiset as DandisetMeta
-from dandischema.models import get_schema_version
 from packaging.version import Version
 from pydantic import ValidationError
 from pydantic_core import ErrorDetails
@@ -41,6 +38,10 @@
     Validator,
 )
 
+if TYPE_CHECKING:
+    from dandischema.models import BareAsset, CommonModel
+    from dandischema.models import Dandiset as DandisetMeta
+
 lgr = dandi.get_logger()
 
 # TODO -- should come from schema.  This is just a simplistic example for now
@@ -107,6 +108,8 @@ def get_metadata(
         ignore_errors: bool = True,
     ) -> DandisetMeta:
         """Return the Dandiset metadata inside the file"""
+        from dandischema.models import Dandiset as DandisetMeta
+
         with open(self.filepath) as f:
             meta = yaml_load(f, typ="safe")
         return DandisetMeta.model_construct(**meta)
@@ -126,6 +129,9 @@ def get_validation_errors(
                 meta, _required_dandiset_metadata_fields, str(self.filepath)
             )
         else:
+            from dandischema.models import Dandiset as DandisetMeta
+            from dandischema.models import get_schema_version
+
             current_version = get_schema_version()
             if schema_version != current_version:
                 raise ValueError(
@@ -186,6 +192,8 @@ def get_validation_errors(
         schema_version: str | None = None,
         devel_debug: bool = False,
     ) -> list[ValidationResult]:
+        from dandischema.models import BareAsset, get_schema_version
+
         current_version = get_schema_version()
         if schema_version is None:
             schema_version = current_version

From a437bcb3e50abb9cf8c70a5b3313129657a8e772 Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Thu, 17 Jul 2025 15:02:30 -0700
Subject: [PATCH 08/17] feat: delay import of `dandischema.models` in
 `dandi.metadata.core`

---
 dandi/metadata/core.py | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/dandi/metadata/core.py b/dandi/metadata/core.py
index 12a53264e..b77afabe0 100644
--- a/dandi/metadata/core.py
+++ b/dandi/metadata/core.py
@@ -3,21 +3,26 @@
 from datetime import datetime
 from pathlib import Path
 import re
+from typing import TYPE_CHECKING
 
-from dandischema import models
 from pydantic import ByteSize
 
-from .util import extract_model, get_generator
 from .. import get_logger
-from ..misctypes import Digest, LocalReadableFile, Readable
 from ..utils import get_mime_type, get_utcnow_datetime
 
+if TYPE_CHECKING:
+    from dandischema import models
+
+    from ..misctypes import Digest, Readable
+
 lgr = get_logger()
 
 
 def get_default_metadata(
     path: str | Path | Readable, digest: Digest | None = None
 ) -> models.BareAsset:
+    from dandischema import models
+
     metadata = models.BareAsset.model_construct()  # type: ignore[call-arg]
     start_time = end_time = datetime.now().astimezone()
     add_common_metadata(metadata, path, start_time, end_time, digest)
@@ -35,6 +40,11 @@ def add_common_metadata(
     Update a `dict` of raw "schemadata" with the fields that are common to both
     NWB assets and non-NWB assets
     """
+    from dandischema import models
+
+    from .util import get_generator
+    from ..misctypes import LocalReadableFile, Readable
+
     if digest is not None:
         metadata.digest = digest.asdict()
     else:
@@ -73,4 +83,8 @@ def prepare_metadata(metadata: dict) -> models.BareAsset:
 
     .. [2] metadata in the form used by the ``dandischema`` library
     """
+    from dandischema import models
+
+    from .util import extract_model
+
     return extract_model(models.BareAsset, metadata)

From 7503e4bd1e8953ceacf5b47f7556530fe736ec01 Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Fri, 18 Jul 2025 15:42:38 -0700
Subject: [PATCH 09/17] feat: delay import of `dandischema.models` in
 `dandi.files.bases`

---
 dandi/files/bases.py | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/dandi/files/bases.py b/dandi/files/bases.py
index fa2754228..7297d9624 100644
--- a/dandi/files/bases.py
+++ b/dandi/files/bases.py
@@ -10,7 +10,7 @@
 from pathlib import Path
 import re
 from threading import Lock
-from typing import IO, TYPE_CHECKING, Any, Generic
+from typing import IO, TYPE_CHECKING, Any, Generic, TypeVar
 from xml.etree.ElementTree import fromstring
 
 import dandischema
@@ -24,7 +24,6 @@
 import dandi
 from dandi.dandiapi import RemoteAsset, RemoteDandiset, RESTFullAPIClient
 from dandi.metadata.core import get_default_metadata
-from dandi.misctypes import DUMMY_DANDI_ETAG, Digest, LocalReadableFile, P
 from dandi.utils import post_upload_size_check, pre_upload_size_check, yaml_load
 from dandi.validate_types import (
     ORIGIN_INTERNAL_DANDI,
@@ -42,6 +41,11 @@
     from dandischema.models import BareAsset, CommonModel
     from dandischema.models import Dandiset as DandisetMeta
 
+    # noinspection PyUnresolvedReferences
+    from dandi.misctypes import BasePath, Digest, LocalReadableFile
+
+P = TypeVar("P", bound="BasePath")
+
 lgr = dandi.get_logger()
 
 # TODO -- should come from schema.  This is just a simplistic example for now
@@ -153,6 +157,8 @@ def as_readable(self) -> LocalReadableFile:
 
         Returns a `Readable` instance wrapping the local file
         """
+        from dandi.misctypes import LocalReadableFile
+
         return LocalReadableFile(self.filepath)
 
 
@@ -167,7 +173,11 @@ class LocalAsset(DandiFile):
     #: (i.e., relative to the Dandiset's root)
     path: str
 
-    _DUMMY_DIGEST = DUMMY_DANDI_ETAG
+    @staticmethod
+    def _get_dummy_digest() -> Digest:
+        from dandi.misctypes import DUMMY_DANDI_ETAG
+
+        return DUMMY_DANDI_ETAG
 
     @abstractmethod
     def get_digest(self) -> Digest:
@@ -202,7 +212,7 @@ def get_validation_errors(
                 f"Unsupported schema version: {schema_version}; expected {current_version}"
             )
         try:
-            asset = self.get_metadata(digest=self._DUMMY_DIGEST)
+            asset = self.get_metadata(digest=self._get_dummy_digest())
             BareAsset(**asset.model_dump())
         except ValidationError as e:
             if devel_debug:
@@ -317,6 +327,7 @@ def get_metadata(
     def get_digest(self) -> Digest:
         """Calculate a dandi-etag digest for the asset"""
         # Avoid heavy import by importing within function:
+        from dandi.misctypes import Digest
         from dandi.support.digests import get_digest
 
         value = get_digest(self.filepath, digest="dandi-etag")
@@ -484,6 +495,8 @@ def as_readable(self) -> LocalReadableFile:
 
         Returns a `Readable` instance wrapping the local file
         """
+        from dandi.misctypes import LocalReadableFile
+
         return LocalReadableFile(self.filepath)
 
 

From f21d8483f2a3d99f67c14088b9b1ccc6dc9b34eb Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Sun, 20 Jul 2025 11:34:25 -0700
Subject: [PATCH 10/17] feat: delay import of
 `dandi.misctypes.DUMMY_DANDI_ZARR_CHECKSUM` in `dandi.files.zarr.py`

This is a step in delaying import of `schema.models` in
`dandi.files.zarr.py`
---
 dandi/files/zarr.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/dandi/files/zarr.py b/dandi/files/zarr.py
index 6220e2294..226de031a 100644
--- a/dandi/files/zarr.py
+++ b/dandi/files/zarr.py
@@ -34,7 +34,7 @@
     RESTFullAPIClient,
 )
 from dandi.metadata.core import get_default_metadata
-from dandi.misctypes import DUMMY_DANDI_ZARR_CHECKSUM, BasePath, Digest
+from dandi.misctypes import BasePath, Digest
 from dandi.utils import (
     chunked,
     exclude_from_zarr,
@@ -363,7 +363,11 @@ class ZarrStat:
 class ZarrAsset(LocalDirectoryAsset[LocalZarrEntry]):
     """Representation of a local Zarr directory"""
 
-    _DUMMY_DIGEST = DUMMY_DANDI_ZARR_CHECKSUM
+    @staticmethod
+    def _get_dummy_digest() -> Digest:
+        from dandi.misctypes import DUMMY_DANDI_ZARR_CHECKSUM
+
+        return DUMMY_DANDI_ZARR_CHECKSUM
 
     @property
     def filetree(self) -> LocalZarrEntry:

From eb963904b33e96badbce7cbfa7394c1c35d019a9 Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Sun, 20 Jul 2025 12:55:34 -0700
Subject: [PATCH 11/17] feat: replace `Digest` constants in `misctypes.py` with
 cache funcs

Replace`DUMMY_DANDI_ETAG` and `DUMMY_DANDI_ZARR_CHECKSUM`
in `dandi.misctypes` with caching functions. This change
is needed to delay the import of `dandischema.models`
in `dandi.misctypes` and in this package in general
---
 dandi/files/bases.py         |  4 ++--
 dandi/files/zarr.py          |  4 ++--
 dandi/metadata/nwb.py        |  4 ++--
 dandi/misctypes.py           | 15 ++++++++++-----
 dandi/tests/test_metadata.py |  6 ++++--
 5 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/dandi/files/bases.py b/dandi/files/bases.py
index 7297d9624..d1c547959 100644
--- a/dandi/files/bases.py
+++ b/dandi/files/bases.py
@@ -175,9 +175,9 @@ class LocalAsset(DandiFile):
 
     @staticmethod
     def _get_dummy_digest() -> Digest:
-        from dandi.misctypes import DUMMY_DANDI_ETAG
+        from dandi.misctypes import get_dummy_dandi_etag
 
-        return DUMMY_DANDI_ETAG
+        return get_dummy_dandi_etag()
 
     @abstractmethod
     def get_digest(self) -> Digest:
diff --git a/dandi/files/zarr.py b/dandi/files/zarr.py
index 226de031a..822c08c45 100644
--- a/dandi/files/zarr.py
+++ b/dandi/files/zarr.py
@@ -365,9 +365,9 @@ class ZarrAsset(LocalDirectoryAsset[LocalZarrEntry]):
 
     @staticmethod
     def _get_dummy_digest() -> Digest:
-        from dandi.misctypes import DUMMY_DANDI_ZARR_CHECKSUM
+        from dandi.misctypes import get_dummy_dandi_zarr_checksum
 
-        return DUMMY_DANDI_ZARR_CHECKSUM
+        return get_dummy_dandi_zarr_checksum()
 
     @property
     def filetree(self) -> LocalZarrEntry:
diff --git a/dandi/metadata/nwb.py b/dandi/metadata/nwb.py
index 38c2ac4e7..1413e2917 100644
--- a/dandi/metadata/nwb.py
+++ b/dandi/metadata/nwb.py
@@ -13,7 +13,7 @@
 from .. import get_logger
 from ..consts import metadata_all_fields
 from ..files import bids, dandi_file, find_bids_dataset_description
-from ..misctypes import DUMMY_DANDI_ETAG, Digest, LocalReadableFile, Readable
+from ..misctypes import Digest, LocalReadableFile, Readable, get_dummy_dandi_etag
 from ..pynwb_utils import (
     _get_pynwb_metadata,
     get_neurodata_types,
@@ -68,7 +68,7 @@ def get_metadata(
             )
             assert isinstance(df, bids.BIDSAsset)
             if not digest:
-                digest = DUMMY_DANDI_ETAG
+                digest = get_dummy_dandi_etag()
             path_metadata = df.get_metadata(digest=digest)
             meta["bids_version"] = df.get_validation_bids_version()
             # there might be a more elegant way to do this:
diff --git a/dandi/misctypes.py b/dandi/misctypes.py
index 9ed2dcf07..22c1cca3f 100644
--- a/dandi/misctypes.py
+++ b/dandi/misctypes.py
@@ -11,6 +11,7 @@
 from dataclasses import dataclass
 from datetime import datetime
 from fnmatch import fnmatchcase
+from functools import cache
 import os.path
 from pathlib import Path
 from typing import IO, TypeVar, cast
@@ -54,11 +55,15 @@ def asdict(self) -> dict[DigestType, str]:
 
 #: Placeholder digest used in some situations where a digest is required but
 #: not actually relevant and would be too expensive to calculate
-DUMMY_DANDI_ETAG = Digest(algorithm=DigestType.dandi_etag, value=32 * "d" + "-1")
-DUMMY_DANDI_ZARR_CHECKSUM = Digest(
-    algorithm=DigestType.dandi_zarr_checksum,
-    value=32 * "d" + "-1--1",
-)
+@cache
+def get_dummy_dandi_etag() -> Digest:
+    return Digest(algorithm=DigestType.dandi_etag, value=32 * "d" + "-1")
+
+
+@cache
+def get_dummy_dandi_zarr_checksum() -> Digest:
+    return Digest(algorithm=DigestType.dandi_zarr_checksum, value=32 * "d" + "-1--1")
+
 
 P = TypeVar("P", bound="BasePath")
 
diff --git a/dandi/tests/test_metadata.py b/dandi/tests/test_metadata.py
index 5c20acf0d..2bd2ff0fb 100644
--- a/dandi/tests/test_metadata.py
+++ b/dandi/tests/test_metadata.py
@@ -49,7 +49,7 @@
     species_map,
     timedelta2duration,
 )
-from ..misctypes import DUMMY_DANDI_ETAG
+from ..misctypes import get_dummy_dandi_etag
 from ..utils import ensure_datetime
 
 METADATA_DIR = Path(__file__).with_name("data") / "metadata"
@@ -836,7 +836,9 @@ def test_ndtypes(ndtypes, asset_dict):
 def test_nwb2asset(simple2_nwb: Path) -> None:
     # Classes with ANY_AWARE_DATETIME fields need to be constructed with
     # model_construct()
-    assert nwb2asset(simple2_nwb, digest=DUMMY_DANDI_ETAG) == BareAsset.model_construct(
+    assert nwb2asset(
+        simple2_nwb, digest=get_dummy_dandi_etag()
+    ) == BareAsset.model_construct(
         schemaKey="Asset",
         schemaVersion=DANDI_SCHEMA_VERSION,
         keywords=["keyword1", "keyword 2"],

From 2c06e3d3726a32378796b622632fc454223cf2f3 Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Sun, 20 Jul 2025 13:21:45 -0700
Subject: [PATCH 12/17] feat: delay `dandischema.models` import in
 `dandi/misctypes.py`

---
 dandi/misctypes.py | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/dandi/misctypes.py b/dandi/misctypes.py
index 22c1cca3f..8df0aa283 100644
--- a/dandi/misctypes.py
+++ b/dandi/misctypes.py
@@ -14,9 +14,10 @@
 from functools import cache
 import os.path
 from pathlib import Path
-from typing import IO, TypeVar, cast
+from typing import IO, TYPE_CHECKING, TypeVar, cast
 
-from dandischema.models import DigestType
+if TYPE_CHECKING:
+    from dandischema.models import DigestType
 
 
 @dataclass
@@ -35,6 +36,8 @@ def dandi_etag(cls, value: str) -> Digest:
         Construct a `Digest` with the given value and a ``algorithm`` of
         ``DigestType.dandi_etag``
         """
+        from dandischema.models import DigestType
+
         return cls(algorithm=DigestType.dandi_etag, value=value)
 
     @classmethod
@@ -43,6 +46,8 @@ def dandi_zarr(cls, value: str) -> Digest:
         Construct a `Digest` with the given value and a ``algorithm`` of
         ``DigestType.dandi_zarr_checksum``
         """
+        from dandischema.models import DigestType
+
         return cls(algorithm=DigestType.dandi_zarr_checksum, value=value)
 
     def asdict(self) -> dict[DigestType, str]:
@@ -57,11 +62,15 @@ def asdict(self) -> dict[DigestType, str]:
 #: not actually relevant and would be too expensive to calculate
 @cache
 def get_dummy_dandi_etag() -> Digest:
+    from dandischema.models import DigestType
+
     return Digest(algorithm=DigestType.dandi_etag, value=32 * "d" + "-1")
 
 
 @cache
 def get_dummy_dandi_zarr_checksum() -> Digest:
+    from dandischema.models import DigestType
+
     return Digest(algorithm=DigestType.dandi_zarr_checksum, value=32 * "d" + "-1--1")
 
 

From 19171a5718045b58dbeef172c8a7227d173a06cc Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Sun, 20 Jul 2025 13:40:55 -0700
Subject: [PATCH 13/17] feat: delay `dandischema.models` import in
 `dandi/files/zarr.py`

---
 dandi/files/zarr.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/dandi/files/zarr.py b/dandi/files/zarr.py
index 822c08c45..42077d06e 100644
--- a/dandi/files/zarr.py
+++ b/dandi/files/zarr.py
@@ -11,9 +11,8 @@
 import os.path
 from pathlib import Path
 from time import sleep
-from typing import Any, Optional
+from typing import TYPE_CHECKING, Any, Optional
 
-from dandischema.models import BareAsset, DigestType
 from pydantic import BaseModel, ConfigDict, ValidationError
 import requests
 from zarr_checksum.tree import ZarrChecksumTree
@@ -55,6 +54,9 @@
     Validator,
 )
 
+if TYPE_CHECKING:
+    from dandischema.models import BareAsset
+
 lgr = get_logger()
 
 
@@ -320,6 +322,8 @@ def get_digest(self) -> Digest:
         directory, the algorithm will be the DANDI Zarr checksum algorithm; if
         it is a file, it will be MD5.
         """
+        from dandischema.models import DigestType
+
         # Avoid heavy import by importing within function:
         from dandi.support.digests import get_digest, get_zarr_checksum
 

From 571de07515c27e8a77de76b771458bccb2690ce4 Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Sun, 20 Jul 2025 14:16:40 -0700
Subject: [PATCH 14/17] feat: delay `dandischema.models` import in
 `dandi/files/bids.py`

---
 dandi/files/bids.py | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/dandi/files/bids.py b/dandi/files/bids.py
index a441e5999..39c8d713a 100644
--- a/dandi/files/bids.py
+++ b/dandi/files/bids.py
@@ -5,10 +5,9 @@
 from datetime import datetime
 from pathlib import Path
 from threading import Lock
+from typing import TYPE_CHECKING
 import weakref
 
-from dandischema.models import BareAsset
-
 from dandi.bids_validator_deno import bids_validate
 
 from .bases import GenericAsset, LocalFileAsset, NWBAsset
@@ -18,6 +17,9 @@
 from ..misctypes import Digest
 from ..validate_types import ValidationResult
 
+if TYPE_CHECKING:
+    from dandischema.models import BareAsset
+
 BIDS_ASSET_ERRORS = ("BIDS.NON_BIDS_PATH_PLACEHOLDER",)
 BIDS_DATASET_ERRORS = ("BIDS.MANDATORY_FILE_MISSING_PLACEHOLDER",)
 
@@ -84,6 +86,8 @@ def _get_metadata(self) -> None:
 
         This populates `self._asset_metadata`
         """
+        from dandischema.models import BareAsset
+
         with self._lock:
             if self._asset_metadata is None:
                 # Import here to avoid circular import
@@ -236,6 +240,8 @@ def get_metadata(
         digest: Digest | None = None,
         ignore_errors: bool = True,
     ) -> BareAsset:
+        from dandischema.models import BareAsset
+
         bids_metadata = BIDSAsset.get_metadata(self, digest, ignore_errors)
         nwb_metadata = NWBAsset.get_metadata(self, digest, ignore_errors)
         return BareAsset(

From 007e89a134663b53c0afd8ca11ed3aa6f55a8ee1 Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Sun, 20 Jul 2025 14:25:35 -0700
Subject: [PATCH 15/17] feat: delay `dandischema.models` import in
 `dandi/dandiset.py`

---
 dandi/dandiset.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/dandi/dandiset.py b/dandi/dandiset.py
index 63ebbfb1b..bce4a818d 100644
--- a/dandi/dandiset.py
+++ b/dandi/dandiset.py
@@ -7,8 +7,6 @@
 from pathlib import Path, PurePath, PurePosixPath
 from typing import TYPE_CHECKING
 
-from dandischema.models import get_schema_version
-
 from . import get_logger
 from .consts import dandiset_metadata_file
 from .files import DandisetMetadataFile, LocalAsset, dandi_file, find_dandi_files
@@ -32,6 +30,8 @@ def __init__(
         schema_version: str | None = None,
     ) -> None:
         if schema_version is not None:
+            from dandischema.models import get_schema_version
+
             current_version = get_schema_version()
             if schema_version != current_version:
                 raise ValueError(

From f7861df1841a7dfd2aca64b98cd32f6bfed28f4c Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Sun, 20 Jul 2025 14:53:14 -0700
Subject: [PATCH 16/17] feat: delay `dandischema.models` import in
 `dandi/cli/cmd_ls.py`

---
 dandi/cli/cmd_ls.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/dandi/cli/cmd_ls.py b/dandi/cli/cmd_ls.py
index 9ac9ed42f..4c01c370a 100644
--- a/dandi/cli/cmd_ls.py
+++ b/dandi/cli/cmd_ls.py
@@ -3,7 +3,6 @@
 import os.path as op
 
 import click
-from dandischema import models
 
 from .base import devel_option, lgr, map_to_click_exceptions
 from .formatter import JSONFormatter, JSONLinesFormatter, PYOUTFormatter, YAMLFormatter
@@ -92,6 +91,8 @@ def ls(
 ):
     """List .nwb files and dandisets metadata."""
 
+    from dandischema import models
+
     # TODO: more logical ordering in case of fields = None
     common_fields = ("path", "size")
     if schema is not None:

From 066e16e5922fade8d11a4049a551356ecc97cd84 Mon Sep 17 00:00:00 2001
From: Isaac To <isaac.chun.to@gmail.com>
Date: Sun, 20 Jul 2025 15:04:05 -0700
Subject: [PATCH 17/17] feat: delay `dandischema.models` import in
 `dandi/download.py`

---
 dandi/download.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/dandi/download.py b/dandi/download.py
index 51cf31de3..874b33b28 100644
--- a/dandi/download.py
+++ b/dandi/download.py
@@ -21,7 +21,6 @@
 from typing import IO, Any, Literal
 
 from dandischema.digests.dandietag import ETagHashlike
-from dandischema.models import DigestType
 from fasteners import InterProcessLock
 import humanize
 from interleave import FINISH_CURRENT, lazy_interleave
@@ -995,6 +994,8 @@ def digest_callback(path: str, algoname: str, d: str) -> None:
             digests[path] = d
 
     def downloads_gen():
+        from dandischema.models import DigestType
+
         for entry in asset.iterfiles():
             entries.append(entry)
             etag = entry.digest