From 5f17201caac8c43fcb465efd993e9549b8c8075f Mon Sep 17 00:00:00 2001
From: Gausshj <kylin_0@qq.com>
Date: Mon, 15 Dec 2025 15:08:50 +0800
Subject: [PATCH] fix(contract): fix contract sign issue

- Do not apply sign on permutation of the first step of contract
---
 grassmann_tensor/tensor.py | 31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/grassmann_tensor/tensor.py b/grassmann_tensor/tensor.py
index 117c21e..30269c1 100644
--- a/grassmann_tensor/tensor.py
+++ b/grassmann_tensor/tensor.py
@@ -844,8 +844,35 @@ def contract(
         order_b = left_leg_b + right_leg_b
 
         # 1. Permutation
-        a = a.permute(order_a)
-        b = b.permute(order_b)
+        arrow_a = tuple(a.arrow[i] for i in order_a)
+        edges_a = tuple(a.edges[i] for i in order_a)
+        tensor_a = a.tensor.permute(order_a)
+        parity_a = tuple(a.parity[i] for i in order_a)
+        mask_a = a.mask.permute(order_a)
+
+        a = dataclasses.replace(
+            a,
+            _arrow=arrow_a,
+            _edges=edges_a,
+            _tensor=tensor_a,
+            _parity=parity_a,
+            _mask=mask_a,
+        )
+
+        arrow_b = tuple(b.arrow[i] for i in order_b)
+        edges_b = tuple(b.edges[i] for i in order_b)
+        tensor_b = b.tensor.permute(order_b)
+        parity_b = tuple(b.parity[i] for i in order_b)
+        mask_b = b.mask.permute(order_b)
+
+        b = dataclasses.replace(
+            b,
+            _arrow=arrow_b,
+            _edges=edges_b,
+            _tensor=tensor_b,
+            _parity=parity_b,
+            _mask=mask_b,
+        )
 
         arrow = a.arrow[:-contract_length_a] + b.arrow[contract_length_b:]
         edges = a.edges[:-contract_length_a] + b.edges[contract_length_b:]