GPT-5.6 Sol Pro decoded: 'Pro' is a reasoning mode, not a new model

2026-07-11 群聊日报

Packet capture reveals OpenCode's Sol Pro is just gpt-5.6-sol with reasoning.mode: "pro" — not a separate model. Mode, effort, and service_tier can be freely combined. A simple greeting jumps from 12 to 1,527 input tokens with Pro enabled, roughly 100x more expensive. Separately, GPT-5.6 now charges for cache writes, potentially doubling Codex costs for long tasks. One user burned 19B tokens in two days, 98% from cache reads. The biggest shock: a researcher's 2024 open problem was solved by gpt-5.6-sol ultra in 46 minutes, verified correct by Fable.

Why it matters: First-hand packet capture with concrete numbers, not a rehash. The Sol Pro debunk and cache billing discovery both deliver real signal, but the source is an anonymous chat group without official confirmation, so the score stays at the featured threshold.