GPT-6 Sol changelog

GPT-6 becomes the ChatGPT model on free and paid plans

OpenAI launched GPT-6 to everyone in ChatGPT on free and paid plans globally, replacing GPT-5.6 Sol and GPT-5.6 Luna in ChatGPT. Codex and ChatGPT Work keep the September versions.

Who is affected:

Everyone using ChatGPT.

What to do:

No action needed. re-check saved prompts and GPTs for changed behavior.

MarginLab Codex tracker shows GPT-6 Sol pass rates falling while its baseline is still being collected

MarginLab's Codex tracker (GPT-6 Sol at high effort, from September 24, 2026) showed 54% on the latest day (50 tasks), 59% over 7 days (350 tasks) and 79% over 30 days (1,450 tasks). The page marks 1-day (-29.4%) and 7-day (-24.9%) changes as statistically significant but says degradation detection is paused while the new baseline is built.

Who is affected:

Codex CLI users on GPT-6 Sol at high effort.

What to do:

Treat the drop as provisional and compare GPT-6.1 Sol on your own tasks.

OpenAI fixes an image encoding bug that degraded GPT-6 Sol and Luna image understanding

OpenAI's API changelog says a bug in image encoding degraded image understanding in GPT-6 Sol and GPT-6 Luna, and the fix improves visual tasks in the API and Codex, including computer use.

Who is affected:

Apps and Codex sessions that sent image inputs or used computer use with GPT-6 Sol or GPT-6 Luna after their September 22 release.

What to do:

Rerun evaluations and retry workflows that used image inputs with GPT-6 Sol or GPT-6 Luna.

GPT-6 Sol and GPT-6 Luna available in GitHub Copilot

GPT-6 Sol is available on Copilot Pro+, Max, Business and Enterprise, and GPT-6 Luna also on Pro, under usage-based billing.

GPT-6 Sol and Luna roll out in Codex and ChatGPT Work

GPT-6 Sol and GPT-6 Luna rolled out to Codex and ChatGPT Work for Plus, Pro, Business, Enterprise and Edu at lower token prices than GPT-5.6. Free and Go get Luna in the desktop app. They are not available in ChatGPT Chat.

Who is affected:

Codex and ChatGPT Work users.

What to do:

Pick gpt-6-sol or gpt-6-luna. Enterprise admins must enable them.

GPT-6 Sol released at $2 input and $10 output

GPT-6 Sol launched on the Responses and Chat Completions APIs at $2 input, $0.20 cached input and $10 output per million tokens for prompts up to 272K tokens.

Who is affected:

Developers on GPT-5.6 Sol or Terra.

What to do:

Compare GPT-6 Sol with your current model. It is cheaper than GPT-5.6 Sol.