OpenAI IPO closing market cap above $1T priced at 60.5% on Polymarket, down 7.0 points, on $1.1M traded

OpenAI’s IPO closing-market-cap contract above $1T was priced at 60.5% on Polymarket, down 7.0 percentage points over 24 hours, with $1.1M traded. According to PredictionBubbles’ finance board, the contract ranked among the largest downward moves in its finance coverage.

A lower probability, still above even odds

The supplied summary places the board reading at Oct. 28, 04:27 UTC. The accompanying headline was published on Oct 28, 2026, at 12:39 AM ET. At that snapshot, pricing still favored an OpenAI IPO closing market capitalization above $1T, despite the decline.

The supplied material does not identify a catalyst for the repricing or provide the contract’s full resolution criteria and deadline. The move therefore establishes a change in market-implied probability, rather than an explanation for why traders reassessed the outcome.

Movement and volume measure different things

PredictionBubbles ranks its movers by the absolute change in probability over the preceding 24 hours, while its volume rankings use total traded volume. The $1.1M figure should therefore not be read as the amount traded during the decline. According to the site, its finance board refreshes every 15 minutes and covers 208 open markets: 23 from Kalshi and 185 from Polymarket.

What it means for prediction markets

• The threshold remains favored: A 60.5% market-implied probability puts the above-$1T outcome ahead, but does not make it certain.
• The decline is a probability move: The 7.0-point fall is not a reported change in OpenAI’s valuation.
• Contract details remain important: The supplied material lacks full settlement terms. PredictionBubbles also cautions that related questions across venues can differ in wording, resolution rules and deadlines.