Replit's free mode runs on GPT-5.6 Luna

Replit is rolling out Free Mode as the new default for its $20/month Core and $100/month Pro subscribers, powered exclusively by OpenAI’s GPT-5.6 Luna. Despite the name, Free Mode still requires an existing paid subscription: it’s a lighter-weight lane for chatting, ideating, or running simple tasks before a project needs the larger model budget attached to the paid tier. Replit and OpenAI frame it as the start of a deeper joint roadmap.

The move follows OpenAI cutting GPT-5.6 Luna’s API cost by 80% on July 30, which made it economical for Replit to offer as a default rather than a premium option. OpenAI says internal testing found Luna produces factual errors about 62% less often than GPT-5.5 Instant across financial, medical, and legal prompts, a claim not yet independently verified.

What it means for you

If you build on Replit, expect simple scaffolding and Q&A tasks to route to Luna by default going forward, saving your paid-tier budget for work that actually needs a stronger model. If you’re evaluating GPT-5.6 Luna for your own product, the 80% price cut is the more durable signal here; a vendor’s own accuracy benchmark against its own prior model is a starting claim, not proof, until an independent eval confirms it. It’s part of a busy week of OpenAI product moves, alongside a reaffirmed zero data retention pledge and ChatGPT ads expanding into Europe.