REASONING

Anthropic's model family. As of October 2026: Opus 5.5 as the default, Fable 5.1 for the hardest long-horizon work, Sonnet 5.5 for speed, Haiku 5.5 for cost. 1M context. Max from $100/mo.

OpenAI's chat app. As of October 2026 Free and Go run GPT-6 Luna; Plus ($20/mo) adds GPT-6.1 Sol and GPT-6 Astra. Agent mode, Codex, image generation, code interpreter.

Chinese lab shipping open-weight MoE models. The V4 family (previewed April 24, 2026) runs a 1M context on DeepSeek's API; R1 (2025) popularized open reasoning models. Low-cost API.

OpenAI's GPT-5 model, released August 2025. Unified fast and reasoning modes in one model. Superseded by the GPT-6 family in September 2026 and now marked deprecated in the API.

Google's model family. As of October 2026 Gemini 4 Argon (GA October 13, 1M token context) is the flagship for coding and agents, with Gemini 3.8 Flash (free tier in AI Studio) as the fast, cheaper option.

xAI's model family, now documented under the SpaceXSI (SpaceX Super Intelligence) name. Grok 4.7 (September 21, 2026) has a 500K context at $2/$6 per million tokens. OpenAI-compatible API.

DeepSeek's reasoning-first model built for agents. First model to integrate thinking directly into tool use. Ships alongside V3.2-Speciale, which rivals GPT-5 and Gemini 3.0 Pro.

Anthropic's Opus model released April 2026, since succeeded by Opus 4.8 and Opus 5.5. Strong at coding, long-context analysis, and agentic work. 1M context, $5/$25 per million tokens.

Anthropic's first generally available Mythos-class model, released June 9, 2026. 1M context, 128K max output, $10/$50 per million tokens. Built for long-horizon agentic work.