diff --git a/models/rfd3/src/rfd3/inference/input_parsing.py b/models/rfd3/src/rfd3/inference/input_parsing.py
index 17032e4..f309180 100644
--- a/models/rfd3/src/rfd3/inference/input_parsing.py
+++ b/models/rfd3/src/rfd3/inference/input_parsing.py
@@ -184,6 +184,7 @@ class DesignInputSpecification(BaseModel):
     symmetry: Optional[SymmetryConfig] = Field(None, description="Symmetry specification, see docs/symmetry.md")
     # Centering & COM guidance
     ori_token: Optional[list[float]] = Field(None, description="Origin coordinates")
+    ori_jitter: Optional[float] = Field(None, description="Jitter ori in a random direction and use ori_jitter to sample distance via exponential distribution")
     infer_ori_strategy: Optional[str] = Field(None, description="Strategy for inferring origin; `com` or `hotspots`")
     # Additional global conditioning
     plddt_enhanced: Optional[bool] = Field(True, description="Enable pLDDT enhancement")
@@ -725,6 +726,13 @@ class DesignInputSpecification(BaseModel):
                     ligand_array.set_annotation(
                         annot, np.full(ligand_array.array_length(), default)
                     )
+            
+            chain_cand = 'X'
+            while chain_cand in atom_array.chain_id.tolist():
+                chain_cand = chain_cand + chain_cand
+            ligand_chain = np.array([chain_cand]*len(ligand_array))
+            ligand_array.chain_id = ligand_chain
+
             atom_array = atom_array + ligand_array
         return atom_array
 
@@ -749,8 +757,10 @@ class DesignInputSpecification(BaseModel):
                     "Partial diffusion with symmetry: skipping COM centering to preserve chain spacing"
                 )
             else:
+                if not exists(self.ori_jitter):
+                   self.ori_jitter = None
                 atom_array = set_com(
-                    atom_array, ori_token=None, infer_ori_strategy="com"
+                    atom_array, ori_token=None, infer_ori_strategy="com", ori_jitter=self.ori_jitter
                 )
         else:
             # Standard: set ori token, zero out diffused atoms
diff --git a/models/rfd3/src/rfd3/inference/legacy_input_parsing.py b/models/rfd3/src/rfd3/inference/legacy_input_parsing.py
index aed3cc9..fbee346 100644
--- a/models/rfd3/src/rfd3/inference/legacy_input_parsing.py
+++ b/models/rfd3/src/rfd3/inference/legacy_input_parsing.py
@@ -736,6 +736,12 @@ def create_atom_array_from_design_specification_legacy(
             + np.max(atom_array.res_id)
             + 1
         )
+        chain_cand = 'X'
+        while chain_cand in atom_array.chain_id.tolist():
+            chain_cand = chain_cand + chain_cand
+        ligand_chain = np.array([chain_cand]*len(ligand_array))
+        ligand_array.chain_id = ligand_chain
+
         atom_array = atom_array + ligand_array
 
     # ... Apply symmetry if it exists ahead of any other processing
diff --git a/models/rfd3/src/rfd3/utils/inference.py b/models/rfd3/src/rfd3/utils/inference.py
index 2d04e14..426eace 100644
--- a/models/rfd3/src/rfd3/utils/inference.py
+++ b/models/rfd3/src/rfd3/utils/inference.py
@@ -452,7 +452,7 @@ as input and return a three-element list or numpy array of floats.
 
 
 def set_com(
-    atom_array, ori_token: list | None = None, infer_ori_strategy: str | None = None
+        atom_array, ori_token: list | None = None, infer_ori_strategy: str | None = None, ori_jitter: float | None = None
 ):
     if exists(ori_token):
         center = np.array([float(x) for x in ori_token], dtype=atom_array.coord.dtype)
@@ -505,6 +505,17 @@ def set_com(
             atom_array.coord = np.zeros_like(
                 atom_array.coord, dtype=atom_array.coord.dtype
             )
+    if ori_jitter is not None:
+        # randomly jitter ori with given scale
+        direction = np.random.normal(size=3)
+        direction /= np.linalg.norm(direction)
+
+        # Random length (mean ~ scale)
+        length = np.random.exponential(scale=scale)
+        jittered_offset = direction*length
+
+        atom_array.coord -= jittered_offset
+
     return atom_array