Baron Rothschild’s famous line, “Buy on the cannons, sell on the trumpets,” was the quote Michael Hartnett chose to lead his latest Flow Show, and it feels particularly relevant as investors continue marching deeper into what he now openly describes as the largest speculative bubble since the railroad boom of the 19th century.

Only a week ago, Hartnett finally acknowledged what many market veterans have been quietly discussing for months: this is a historic bubble. Yet even then, he argued that investors were not quite ready to head for the exits. His reasoning was straightforward. Markets rarely abandon risk assets ahead of blockbuster IPO waves, and policymakers are unlikely to tighten financial conditions aggressively until inflation becomes a more obvious political problem. In his framework, that likely means waiting until CPI pushes toward the 4% to 5% range, the zone that has historically forced policymakers to lean against speculative excess and often marked the beginning of more meaningful market corrections.

Fast forward to today and Hartnett’s attention has shifted from identifying the bubble to preparing for what comes after it. His starting point is a familiar one. Ultimately, every major speculative cycle is brought to heel by the same forces: central banks and bond markets. Rising yields increase the cost of capital, tighten financial conditions, and eventually force investors to reassess even the most compelling growth stories. The problem for bears is that those forces are not yet fully engaged. Global central banks have delivered 31 rate cuts so far this year versus just 12 hikes, and liquidity conditions remain far more supportive than restrictive. Add in an estimated $3 trillion pipeline of potential IPO issuance still waiting in the wings, and the fuel feeding the current boom appears far from exhausted.