diff --git a/test/test_env.py b/test/test_env.py
index b48b1a1cf8f..cef7a507f2a 100644
--- a/test/test_env.py
+++ b/test/test_env.py
@@ -8,6 +8,7 @@
 import functools
 import gc
 import os.path
+import random
 import re
 from collections import defaultdict
 from functools import partial
@@ -114,6 +115,7 @@
     DoubleToFloat,
     EnvBase,
     EnvCreator,
+    LLMHashingEnv,
     ParallelEnv,
     PendulumEnv,
     SerialEnv,
@@ -3419,6 +3421,29 @@ def test_pendulum_env(self, device):
             r = env.rollout(10, tensordict=TensorDict(batch_size=[5], device=device))
             assert r.shape == torch.Size((5, 10))
 
+    def test_llm_hashing_env(self):
+        vocab_size = 5
+
+        class Tokenizer:
+            def __call__(self, obj):
+                return torch.randint(vocab_size, (len(obj.split(" ")),)).tolist()
+
+            def decode(self, obj):
+                words = ["apple", "banana", "cherry", "date", "elderberry"]
+                return " ".join(random.choice(words) for _ in obj)
+
+            def batch_decode(self, obj):
+                return [self.decode(_obj) for _obj in obj]
+
+            def encode(self, obj):
+                return self(obj)
+
+        tokenizer = Tokenizer()
+        env = LLMHashingEnv(tokenizer=tokenizer, vocab_size=vocab_size)
+        td = env.make_tensordict("some sentence")
+        assert isinstance(td, TensorDict)
+        env.check_env_specs(tensordict=td)
+
 
 @pytest.mark.parametrize("device", [None, *get_default_devices()])
 @pytest.mark.parametrize("env_device", [None, *get_default_devices()])
diff --git a/torchrl/data/map/tree.py b/torchrl/data/map/tree.py
index 513a7b94e58..c09db75aa5b 100644
--- a/torchrl/data/map/tree.py
+++ b/torchrl/data/map/tree.py
@@ -135,35 +135,40 @@ def make_node(
     def full_observation_spec(self):
         """The observation spec of the tree.
 
-        This is an alias for `Tree.specs['output_spec', 'full_observation_spec']`."""
+        This is an alias for `Tree.specs['output_spec', 'full_observation_spec']`.
+        """
         return self.specs["output_spec", "full_observation_spec"]
 
     @property
     def full_reward_spec(self):
         """The reward spec of the tree.
 
-        This is an alias for `Tree.specs['output_spec', 'full_reward_spec']`."""
+        This is an alias for `Tree.specs['output_spec', 'full_reward_spec']`.
+        """
         return self.specs["output_spec", "full_reward_spec"]
 
     @property
     def full_done_spec(self):
         """The done spec of the tree.
 
-        This is an alias for `Tree.specs['output_spec', 'full_done_spec']`."""
+        This is an alias for `Tree.specs['output_spec', 'full_done_spec']`.
+        """
         return self.specs["output_spec", "full_done_spec"]
 
     @property
     def full_state_spec(self):
         """The state spec of the tree.
 
-        This is an alias for `Tree.specs['input_spec', 'full_state_spec']`."""
+        This is an alias for `Tree.specs['input_spec', 'full_state_spec']`.
+        """
         return self.specs["input_spec", "full_state_spec"]
 
     @property
     def full_action_spec(self):
         """The action spec of the tree.
 
-        This is an alias for `Tree.specs['input_spec', 'full_action_spec']`."""
+        This is an alias for `Tree.specs['input_spec', 'full_action_spec']`.
+        """
         return self.specs["input_spec", "full_action_spec"]
 
     @property
diff --git a/torchrl/envs/common.py b/torchrl/envs/common.py
index 004f2958a0d..f5d102a6279 100644
--- a/torchrl/envs/common.py
+++ b/torchrl/envs/common.py
@@ -555,6 +555,8 @@ def auto_specs_(
 
     @wraps(check_env_specs_func)
     def check_env_specs(self, *args, **kwargs):
+        return_contiguous = kwargs.pop("return_contiguous", not self._has_dynamic_specs)
+        kwargs["return_contiguous"] = return_contiguous
         return check_env_specs_func(self, *args, **kwargs)
 
     check_env_specs.__doc__ = check_env_specs_func.__doc__
@@ -3285,7 +3287,10 @@ def maybe_reset(self, tensordict: TensorDictBase) -> TensorDictBase:
         """
         if self._simple_done:
             done = tensordict._get_str("done", default=None)
-            any_done = done is not None and done.any()
+            if done is not None:
+                any_done = done.any()
+            else:
+                any_done = False
             if any_done:
                 tensordict._set_str(
                     "_reset",
diff --git a/torchrl/envs/custom/llm.py b/torchrl/envs/custom/llm.py
index 67880f08ee7..2f456482147 100644
--- a/torchrl/envs/custom/llm.py
+++ b/torchrl/envs/custom/llm.py
@@ -5,7 +5,7 @@
 from typing import Callable, List, Union
 
 import torch
-from tensordict import NestedKey, TensorDictBase
+from tensordict import NestedKey, TensorDict, TensorDictBase
 from tensordict.tensorclass import NonTensorData, NonTensorStack
 
 from torchrl.data import (
@@ -103,7 +103,7 @@ def __init__(
         self.observation_key = observation_key
         observation_spec = {
             observation_key: CategoricalSpec(n=vocab_size, shape=(-1,)),
-            "hash": Unbounded(shape=(1,), dtype=torch.int64),
+            "hashing": Unbounded(shape=(1,), dtype=torch.int64),
         }
         self.text_output = text_output
         if not text_output:
@@ -117,6 +117,16 @@ def __init__(
         self.action_spec = Composite(action=CategoricalSpec(vocab_size, shape=(1,)))
         _StepMDP(self)
 
+    def make_tensordict(self, input: str | List[str]) -> TensorDict:
+        """Converts a string or list of strings in a TensorDict with appropriate shape and device."""
+        list_len = len(input) if isinstance(input, list) else 0
+        tensordict = TensorDict(
+            {self.observation_key: self._tokenizer(input)}, device=self.device
+        )
+        if list_len:
+            tensordict.batch_size = [list_len]
+        return self.reset(tensordict)
+
     def _reset(self, tensordict: TensorDictBase):
         """Initializes the environment with a given observation.
 
@@ -128,7 +138,11 @@ def _reset(self, tensordict: TensorDictBase):
 
         """
         out = tensordict.empty()
-        obs = tensordict.get(self.observation_key)
+        obs = tensordict.get(self.observation_key, None)
+        if obs is None:
+            raise RuntimeError(
+                f"Resetting the {type(self).__name__} environment requires a prompt."
+            )
         if self.text_output:
             if obs.ndim > 1:
                 text = self._tokenizer.batch_decode(obs)
@@ -139,9 +153,9 @@ def _reset(self, tensordict: TensorDictBase):
             out.set(self.text_key, text)
 
         if obs.ndim > 1:
-            out.set("hash", self._hashing_module(obs).unsqueeze(-1))
+            out.set("hashing", self._hashing_module(obs).unsqueeze(-1))
         else:
-            out.set("hash", self._hashing_module(obs.unsqueeze(0)).transpose(0, -1))
+            out.set("hashing", self._hashing_module(obs.unsqueeze(0)).transpose(0, -1))
 
         if not self.full_done_spec.is_empty():
             out.update(self.full_done_spec.zero(tensordict.shape))
@@ -166,7 +180,7 @@ def _step(self, tensordict):
         obs = torch.cat([tensordict.get(self.observation_key), action], -1)
         kwargs = {self.observation_key: obs}
 
-        catval = torch.cat([tensordict.get("hash"), action], -1)
+        catval = torch.cat([tensordict.get("hashing"), action], -1)
         if obs.ndim > 1:
             new_hash = self._hashing_module(catval).unsqueeze(-1)
         else:
@@ -182,7 +196,7 @@ def _step(self, tensordict):
             kwargs[self.text_key] = text
         kwargs.update(
             {
-                "hash": new_hash,
+                "hashing": new_hash,
                 "done": torch.zeros((*tensordict.batch_size, 1), dtype=torch.bool),
                 "terminated": torch.zeros(
                     (*tensordict.batch_size, 1), dtype=torch.bool
diff --git a/torchrl/envs/utils.py b/torchrl/envs/utils.py
index 423b71e316e..d2ec66475ab 100644
--- a/torchrl/envs/utils.py
+++ b/torchrl/envs/utils.py
@@ -778,12 +778,15 @@ def check_env_specs(
         )
     zeroing_err_msg = (
         "zeroing the two tensordicts did not make them identical. "
-        "Check for discrepancies:\nFake=\n{fake_tensordict}\nReal=\n{real_tensordict}"
+        f"Check for discrepancies:\nFake=\n{fake_tensordict}\nReal=\n{real_tensordict}"
     )
     from torchrl.envs.common import _has_dynamic_specs
 
     if _has_dynamic_specs(env.specs):
-        for real, fake in zip(real_tensordict.unbind(-1), fake_tensordict.unbind(-1)):
+        for real, fake in zip(
+            real_tensordict.filter_non_tensor_data().unbind(-1),
+            fake_tensordict.filter_non_tensor_data().unbind(-1),
+        ):
             fake = fake.apply(lambda x, y: x.expand_as(y), real)
             if (torch.zeros_like(real) != torch.zeros_like(fake)).any():
                 raise AssertionError(zeroing_err_msg)
@@ -1367,6 +1370,8 @@ def _update_during_reset(
     reset_keys: List[NestedKey],
 ):
     """Updates the input tensordict with the reset data, based on the reset keys."""
+    if not reset_keys:
+        return tensordict.update(tensordict_reset)
     roots = set()
     for reset_key in reset_keys:
         # get the node of the reset key