Gastric cancer is one of the most common and deadly cancers globally, characterized by a poor prognosis. Approximately 70% of patients are diagnosed at an advanced stage, and the 5-year survival rate is only around 10%. While advancements in targeted therapies and immunotherapy have improved treatment efficacy and extended survival, advanced gastric and gastroesophageal junction adenocarcinomas remain incurable. Subgroup analyses indicate that patients with limited metastases, such as liver oligometastasis or retroperitoneal lymph node metastasis, may benefit more from conversion therapy. However, current guidelines do not recommend specific treatment protocols for gastric cancer with limited metastasis. Immunotherapy has shown moderate efficacy in selected patients with advanced gastric adenocarcinoma. Additionally, low-dose radiotherapy (LDRT) may synergistically enhance antitumor responses when combined with immunotherapy. This Phase II trial aims to evaluate the safety and efficacy of combining Adebrelimab, chemotherapy, and LDRT before surgery in treating adult patients with gastric or gastroesophageal junction adenocarcinoma.