Western LLMs are definitely still ahead on agentic coding, but I wouldn't say the gap has been increasing. There's been diminishing returns at the very top level in the last couple of months, the Claude 4.5 -> 4.6 and GPT 5.2 -> 5.4 difference isn't as drastic as the previous jumps.
As much as we might hate Anthropic's CEO, Claude is still undeniably the best at enterprise-level coding performance in my testing and talking to various folks in the industry, but Anthropic's decision to ban & go after Chinese enterprise users is going to screw them in the long-term. China is a huge market for LLMs and the tokens usage reflect that since Western apps/models are banned. All of that usage then feeds into additional training data, which with sufficient compute, will eventually put China ahead even in areas the West is currently ahead in.