OpenAI launches GPT-5.5, Polymarket contract certainty

OpenAI launched GPT-5.5 in ChatGPT and Codex, and the Polymarket contract for GPT-5.5 by April 30, 2026 now sits at 100% YES.

Market reaction

The April 30 market reached 100% YES, up from 98% just 24 hours ago. The June 30 market is also at 100% YES. No spread between the two contracts, which is what you’d expect once the event has actually happened.

Trading volume hit $233,954 in USDC over the last 24 hours. The largest single price movement was a 3-point drop at 5:37 PM, which settled back to full certainty quickly. Order book depth is thick enough that large trades barely moved the price.

Why it matters

The release itself killed any remaining speculation about delays or a pivot to GPT-6 before 5.5 shipped. At 100% probability, the market is resolved in all but name. There’s no room for new entrants to profit unless something truly bizarre happens, like OpenAI retracting the release.

What to watch

With the market fully priced in, the action moves elsewhere. Traders should watch for adoption data, competitive responses from DeepSeek and Anthropic, and integration announcements from Microsoft or other OpenAI partners that could affect related contracts.

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