Model capability, evaluation integrity, and what inference actually costs.
OpenAI's GPT-6 Sol and GPT-6 Luna arrived on September 22 at half the promotional price of their GPT-5.6 namesakes. The rate card shows the Sol name now sits one rung lower than it did.
Anthropic released Claude Sonnet 5.5 on September 28 at Sonnet 5's prices. Its migration docs list five requests that now fail, and one of them collides with the model's new cyber fallback.
Opus 5.5's 40% saving explained, the default effort that dropped to medium, and what breaks moving from Opus 5.
Claude Code 2.1.277 adds AGENTS.md support, with an either/or default.
Claude Code 2.1.278: server-side auto mode checks, no classifier charge.
DeepSeek reversed its plan to route deepseek-v4-pro to V4.1-Flash on Sept 14, but the launch page wasn't updated.
