Major US stock exchanges experience an unscheduled trading halt or delay before December 2026.

Question

Six frontier AI models put this at 17% by 4 Dec 2026. Full reasoning from every model.

WillHappen.ai · Accepted Answer

17% — the median of 6 frontier models, resolving by 2026-12-04.

Answer

Gemini (Google): 3% — Turns on a severe exchange-wide tech outage or market circuit breaker hitting NYSE or Nasdaq in under four trading weeks. Full exchange halts or delays on NYSE/Nasdaq occur roughly once every 2-3 years, yielding an ~0.08 annual base rate. Across roughly 18 trading days remaining before December 2026, the Poisson probability of an outage is very low. A massive macro shock triggering a Level 1 7% S&P 500 circuit breaker is the primary risk factor but remains rare.

Answer

Claude (Anthropic): 80% — Depends on routine circuit-breaker/technical halts occurring, which happen almost yearly across NYSE/Nasdaq. Market-wide circuit breakers or exchange technical glitches (e.g., 2024 Nasdaq delays, 2010 flash crash, 2012 BATS/Knight) recur every 1-3 years. Over a 13-month window base rate for any unscheduled halt/delay across either exchange is high given volatility clusters and tech fragility. Main risk to 'yes' is unusually calm markets and flawless exchange uptime for the full period, which is uncommon.

Answer

GPT (OpenAI): 57% — A one-month window still includes plausible operational, weather, cyber, and market-structure triggers for NYSE or Nasdaq disruption. NYSE and Nasdaq must halt or delay their own markets between Nov. 4 and Dec. 4; a single venue-wide event qualifies. Brief exchange-wide interruptions occur intermittently, but a 30-day window is short and Thanksgiving reduces regular-session days. A major volatility shock, cyber incident, or severe Northeast infrastructure failure would sharply raise the odds.

Answer

Grok (xAI): 7% — A NYSE/Nasdaq halt in the next 20 sessions requires a circuit-breaker drop or rare tech outage. Market-wide circuit breakers last fired in March 2020 and have not since, even in 2022; they need a 7% S&P drop in a day. Full-session tech halts (NYSE 2015, Nasdaq 2013) occur roughly once every 5–7 years, so a 30-day window is far below that rate. Only an extreme one-day crash or exchange-wide outage in November would change the call.

Answer

DeepSeek (DeepSeek): 12% — Whether a 7% S&P 500 plunge or a technical failure forces NYSE/Nasdaq to halt trading in the next 30 days. NYSE and Nasdaq each maintain Rule 80B-style circuit breakers; a Level 1 halt needs a 7% S&P 500 drop before 3:25pm ET, which has happened only once since 2012 (March… Exchanges can also halt for technical failures: the July 2024 CrowdStrike outage and 2015 NYSE software glitch show single-venue halts occur roughly every 2-3 years. With one month left and no scheduled Fed meeting or election catalyst, the base rate for a 7% intraday drop in any given month is under 2%, but a technical halt is the…

Answer

Qwen (Alibaba): 22% — Exchange-wide technical halts occur a few times per year; a one-month window gives modest but real odds. NYSE and Nasdaq each experience exchange-level technical halts roughly 2-4 times per year combined (2024 saw multiple NYSE outages), giving ~20-30% in any single month. Circuit breakers (S&P 500 down 7%+) are far rarer—last triggered March 2020—so the probability rests almost entirely on technical failures, not volatility. A development that would raise this sharply: a major geopolitical shock or flash-crash event in November, which would push circuit-breaker odds from near-zero to…

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