Anthropic's sonnet 5.5 leaks, outperforms gpt-6 sol and approaches astra

Anthropic's Sonnet 5.5 has leaked ahead of its official release, with early tests showing it outperforms GPT-6 Sol and closely matches GPT-6 Astra. The model, now in final testing phases, has been quietly rolled out to some users via Claude Code. Developers report that Sonnet 5.5 generates complex UI animations and code with high efficiency and natural coding style, surpassing GPT-6 Sol in speed and quality. Its pricing, at $2 per million tokens, is significantly lower than OpenAI's offerings, threatening to disrupt the market. Analysts suggest that Sonnet 5.5 could challenge OpenAI's dominance, especially with its competitive pricing and performance. The leak comes ahead of OpenAI's DevDay on September 29, 2026, raising concerns about Anthropic's rapid development cycle and potential for further innovation.