From b234532d9f02e232c973aa1cf6d137530b0b8d27 Mon Sep 17 00:00:00 2001
From: NanoCode012 <nano@axolotl.ai>
Date: Fri, 28 Nov 2025 18:54:48 +0700
Subject: [PATCH] Feat: add peft_ensure_weight_tying (#3278)

* feat: upgrade peft to 0.18.0

* feat: add peft_ensure_weight_tying

* fix: default

* chore: adjust kwarg per feedback
---
 requirements.txt                  | 2 +-
 src/axolotl/loaders/adapter.py    | 2 ++
 src/axolotl/utils/schemas/peft.py | 9 +++++++++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/requirements.txt b/requirements.txt
index 08759279d..f020aaffc 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -11,7 +11,7 @@ liger-kernel==0.6.3
 packaging==23.2
 
 huggingface_hub>=0.36.0
-peft>=0.17.1
+peft>=0.18.0
 tokenizers>=0.22.1
 transformers==4.57.1
 accelerate==1.11.0
diff --git a/src/axolotl/loaders/adapter.py b/src/axolotl/loaders/adapter.py
index 8e8177b62..dca688bb2 100644
--- a/src/axolotl/loaders/adapter.py
+++ b/src/axolotl/loaders/adapter.py
@@ -102,6 +102,8 @@ def load_lora(
         lora_config_kwargs["layer_replication"] = cfg.peft_layer_replication
     if cfg.peft_trainable_token_indices:
         lora_config_kwargs["trainable_token_indices"] = cfg.peft_trainable_token_indices
+    if cfg.peft_ensure_weight_tying is not None:
+        lora_config_kwargs["ensure_weight_tying"] = cfg.peft_ensure_weight_tying
 
     # Determine the correct PEFT task type
     model_cls = type(model).__name__
diff --git a/src/axolotl/utils/schemas/peft.py b/src/axolotl/utils/schemas/peft.py
index af22913fd..fd16dec3f 100644
--- a/src/axolotl/utils/schemas/peft.py
+++ b/src/axolotl/utils/schemas/peft.py
@@ -100,6 +100,15 @@ class LoraConfig(BaseModel):
             )
         },
     )
+    peft_ensure_weight_tying: bool | None = Field(
+        default=None,
+        json_schema_extra={
+            "description": (
+                "Whether to tie adapter weights for tied model weights. "
+                "See https://github.com/huggingface/peft/issues/2864"
+            )
+        },
+    )
 
     qlora_sharded_model_loading: bool | None = Field(
         default=False,