OpenAI made GPT-5.5 available via API starting around May 1, 2026, introducing a 1M token context window and a two-tier pricing structure. The standard GPT-5.5 tier is priced at $5 per million input tokens and $30 per million output tokens, while GPT-5.5-pro targets high-throughput enterprise workloads at $30/1M input and $180/1M output. The 1M context window positions GPT-5.5 competitively against long-context models from Anthropic and Google. The pro tier pricing is substantially higher than comparable models, signaling OpenAI is targeting customers with latency-sensitive or accuracy-critical production workloads. Developers integrating GPT-5.5 should evaluate context costs carefully given the wide spread between input and output token prices.