Structural barriers constrain the sustainable integration of public sports services in the Chengdu Chongqing Economic Circle

Achieving balanced regional collaboration in public services is a core challenge for sustainable urban development. This study analyzes the formation mechanisms of the public sports service collaborative network in the Chengdu-Chongqing Economic Circle (CCEC) to provide targeted policy insights for promoting equitable regional integration. To overcome the challenge of analyzing unstructured policy texts, we developed an integrated framework: a fine-tuned BERT model was used to extract weighted collaborative relationships from policy documents (2020–2024). The network's structural evolution was then analyzed using Social Network Analysis (SNA), and its formation mechanisms were identified using Valued Exponential Random Graph Models (VERGMs) for the period 2021–2023. The results show that: (1) The collaborative network exhibits a persistent core-periphery structure, evolving towards denser but uneven integration, with peripheral areas lagging significantly. (2) Chengdu and Chongqing consistently function as the dominant hubs, concentrating the majority of collaborative ties and reinforcing regional imbalances. (3) Network formation is significantly driven by endogenous structural tendencies (transitivity), strong administrative homophily (OR ≈ 5.93), resource attraction (PGDP, R&D), and policy-activated geographic proximity (OR ≈ 2.27). In conclusion, while policy initiatives successfully stimulate collaboration, the network's evolution is fundamentally constrained by pre-existing administrative hierarchies and resource imbalances, hindering the goals of sustainable and equitable development. The proposed BERT-VERGM framework is a powerful tool for uncovering these policy-driven dynamics.