# ChatGPT Splits Free Unlimited Luna From Paid Sol — Lab Factuality Only

Times of AI Desk · 2026-08-06 · Models

[https://timesof.ai/2026/08/openai-gpt-5-6-sol-chatgpt-luna-free-tier](https://timesof.ai/2026/08/openai-gpt-5-6-sol-chatgpt-luna-free-tier)

> OpenAI retuned GPT-5.6 Sol for ChatGPT Plus/Pro with a thinking-effort slider and made Luna the Free/Go default with unlimited text chats. Internal evals claim ~68% / ~62% fewer factual-error responses vs GPT-5.5 Instant — company-run, not Arena or Artificial Analysis. Distribution day, not a new base-model family.

OpenAI is splitting the free tier into **unlimited cheap intelligence** (Luna text) while selling **deeper, cleaner Sol** behind Plus/Pro — with a slider that productizes “how hard should the model think?” as UX instead of model-picker jargon.

**OpenAI** updated **ChatGPT** defaults across paid and free tiers. **Plus and Pro** get a **ChatGPT-tuned GPT-5.6 Sol** (separate from the Sol used in **Codex / ChatGPT Work**) plus a **thinking-effort slider** that replaces separate Instant vs Thinking modes. **Free and Go** users get **GPT-5.6 Luna** as default, with **unlimited text chats** and a **Think** button rolling out on a staggered schedule. OpenAI says one **billion** people now use ChatGPT weekly.

## What changed by tier

| Tier | Model default | New controls | Notes (OpenAI + release notes) |
|------|---------------|--------------|--------------------------------|
| **Plus / Pro** | Updated **GPT-5.6 Sol** (ChatGPT path) | **Thinking slider** | More focused answers; less excess formatting; adapts detail to question difficulty |
| **Free / Go** | **GPT-5.6 Luna** | **Think** button for harder questions (rolling) | **Unlimited text chats** next (abuse guardrails remain); limits stay on files, images, voice, image gen, other tools |
| **Codex / Work Sol** | Unchanged | — | ChatGPT Sol retune is **product-path specific** |

## Claims vs checks

OpenAI reports an **internal evaluation** on finance, medicine, and law prompts requiring factual detail:

| Model | Claim vs **GPT-5.5 Instant** |
|-------|------------------------------|
| **GPT-5.6 Sol** (updated ChatGPT) | ~**68%** fewer responses with ≥1 factual error |
| **GPT-5.6 Luna** | ~**62%** fewer responses with ≥1 factual error |

These are **company-run** figures — not independent arena or third-party factuality boards. Treat as lab-reported until Artificial Analysis / Arena-style audits catch up.

Not a new base-model family GA — GPT-5.6 Sol/Terra/Luna already public from the July family launch and subsequent price cuts. Independent **LMArena / Artificial Analysis** ranks for the **original** Sol/Luna tiers still apply as the backbone; this post does not publish a new public Elo. Note when ChatGPT-path Sol diverges from API/Codex Sol in user experience.

## Limits

- Factuality cuts are internal only; no new public Elo.
- Unlimited free text may raise abuse/cost pressure — not measured here.
- Work/Codex Sol stays deliberately different from chat Sol.

## Sources

- [OpenAI: Improving GPT-5.6 Sol in ChatGPT—and expanding access to GPT-5.6 Luna for free users (August 6, 2026)](https://openai.com/index/improving-gpt-5-6-sol-in-chatgpt/)
- [OpenAI ChatGPT release notes (August 6, 2026 section)](https://help.openai.com/en/articles/6825453-chatgpt-release-notes)
- [The Decoder: OpenAI improves GPT-5.6 Sol and free-tier Luna shift (August 6, 2026)](https://the-decoder.com/openai-improves-gpt-5-6-sol-in-chatgpt-and-restricts-free-users-to-its-weakest-model/)
- Times of AI: `openai-gpt-5-6-luna-terra-price-cuts` (July 30)