diff --git a/CHANGELOG.md b/CHANGELOG.md
index 508d29c..5ed082f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -55,6 +55,17 @@ out_sliced = out.aggregate("slices", target_spans=(13,73))
 out_sliced = out[13:73]
 ```
 
+- A new `StringSplitAggregator` (`"split"`) is added to allow for supporting more complex aggregation procedures beyond simple subword merging  in`FeatureAttributionSequenceOutput` objects. More specifically, splitting supports regex expression to match split points even when these are (potentially overlapping) parts of existing tokens. The `split_mode` parameter can be set to `"single"` (default) to keep tokens containing matched split points separate while aggregating the rest, or `"start"` or `"end"` to concatenate them to the preceding/following aggregated token sequence. [#290](https://github.com/inseq-team/inseq/pull/290)
+
+```python
+# Split on newlines. Default split_mode = "single".
+out.aggregate("split", split_pattern="\n").aggregate("sum").show(do_aggregation=False)
+
+# Split on whitespace-separated words of length 5.
+# Note: this works if clean_special_chars = True is used, otherwise the split_pattern should be adjusted to split on special characters like "Ġ" or "▁".
+out.aggregate("split", split_pattern=r"\s(\w{5})(?=\s)", split_mode="end")
+```
+
 - The `__sub__` method in `FeatureAttributionSequenceOutput` is now used as a shortcut for `PairAggregator` ([#282](https://github.com/inseq-team/inseq/pull/282)).
 
 
@@ -90,6 +101,8 @@ out_female = attrib_model.attribute(
 
 - Fix support for multi-EOS tokens (e.g. LLaMA 3.2, see [#287](https://github.com/inseq-team/inseq/issues/287)).
 
+- Fix copying configuration parameters to aggregated `FeatureAttributionSequenceOutput` objects ([#292](https://github.com/inseq-team/inseq/pull/292)).
+
 ## 📝 Documentation and Tutorials
 
 - Updated tutorial with `treescope` usage examples.
diff --git a/inseq/data/aggregator.py b/inseq/data/aggregator.py
index 2e0301b..d8cf550 100644
--- a/inseq/data/aggregator.py
+++ b/inseq/data/aggregator.py
@@ -302,7 +302,7 @@ def _aggregate(
                     kwargs["aggregate_fn"] = kwargs["aggregate_fn"][cls.aggregator_family]
             field_func = getattr(cls, f"aggregate_{field}")
             aggregated_sequence_attribution_fields[field] = field_func(attr, **kwargs)
-        return attr.__class__(**aggregated_sequence_attribution_fields)
+        return attr.__class__(**aggregated_sequence_attribution_fields, **attr.config)
 
     @classmethod
     def _process_attribution_scores(
@@ -346,6 +346,12 @@ def _process_attribution_scores(
     @classmethod
     def post_aggregate_hook(cls, attr: "FeatureAttributionSequenceOutput", **kwargs):
         super().post_aggregate_hook(attr, **kwargs)
+        if attr.source_attributions is not None:
+            attr._num_dimensions = attr.source_attributions.ndim
+        elif attr.target_attributions is not None:
+            attr._num_dimensions = attr.target_attributions.ndim
+        else:
+            attr._num_dimensions = 0
         cls.is_compatible(attr)
 
     @classmethod
diff --git a/inseq/data/attribution.py b/inseq/data/attribution.py
index fbf2b68..e5e4fc1 100644
--- a/inseq/data/attribution.py
+++ b/inseq/data/attribution.py
@@ -167,6 +167,7 @@ class FeatureAttributionSequenceOutput(TensorWrapper, AggregableMixin):
     _aggregator: str | list[str] | None = None
     _dict_aggregate_fn: dict[str, str] | None = None
     _attribution_dim_names: dict[str, dict[int, str]] | None = None
+    _num_dimensions: int | None = None
 
     def __post_init__(self):
         if self._dict_aggregate_fn is None:
@@ -181,6 +182,8 @@ def __post_init__(self):
         self._attribution_dim_names = default_dim_names
         if self._aggregator is None:
             self._aggregator = "scores"
+        if self._num_dimensions is None:
+            self._num_dimensions = 0
         if self.attr_pos_end is None or self.attr_pos_end > len(self.target):
             self.attr_pos_end = len(self.target)
 
@@ -309,6 +312,10 @@ def _recover_from_safetensors(self):
             }
         return self
 
+    @property
+    def config(self) -> dict[str, Any]:
+        return {k: v for k, v in self.__dict__.items() if k.startswith("_")}
+
     @staticmethod
     def get_remove_pad_fn(attr: "FeatureAttributionStepOutput", name: str) -> Callable:
         if attr.source_attributions is None or name.startswith("decoder"):
@@ -696,10 +703,13 @@ class FeatureAttributionStepOutput(TensorWrapper):
     source: OneOrMoreTokenWithIdSequences | None = None
     prefix: OneOrMoreTokenWithIdSequences | None = None
     target: OneOrMoreTokenWithIdSequences | None = None
+    _num_dimensions: int | None = None
     _sequence_cls: type["FeatureAttributionSequenceOutput"] = FeatureAttributionSequenceOutput
 
     def __post_init__(self):
         self.to(torch.float32)
+        if self._num_dimensions is None:
+            self._num_dimensions = 0
         if self.step_scores is None:
             self.step_scores = {}
         if self.sequence_scores is None:
@@ -1213,8 +1223,6 @@ class MultiDimensionalFeatureAttributionSequenceOutput(FeatureAttributionSequenc
     attention head and per layer for every source-target token pair in the source attributions (i.e. 2 dimensions).
     """
 
-    _num_dimensions: int = 2
-
     def __post_init__(self):
         super().__post_init__()
         self._aggregator = ["mean"] * self._num_dimensions
@@ -1233,7 +1241,6 @@ def __post_init__(self):
 class MultiDimensionalFeatureAttributionStepOutput(FeatureAttributionStepOutput):
     """Raw output of a single step of multi-dimensional feature attribution."""
 
-    _num_dimensions: int = 2
     _sequence_cls: type["FeatureAttributionSequenceOutput"] = MultiDimensionalFeatureAttributionSequenceOutput
 
     def get_sequence_cls(self, **kwargs):