Altman's 'close partner' post adds about $2.5 billion to Cerebras after a 20% slide

In premarket trading, a 6.3% move on a company valued at just over $39 billion is worth about $2.5 billion ^[2][6][13]. It is roughly a quarter of the $10 billion agreement under which Cerebras is to deliver 750 megawatts of computing power to OpenAI through 2028 ^[8][14]. The prior week went the other way, and further. Taking $39 billion as roughly where the 20% slide ended, Cerebras started that week near $49 billion and lost close to $10 billion ^[15]. That loss is about the face value of the entire contract, and it came on reports about which chips run one mode of one model ^[3].

Even the size of the fall depends on the measure used. Market value is down about 59% from the $95 billion of the May debut ^[16], while the share price is down nearly half from its post-IPO high ^[7]. The reports do not reconcile the two.

The contract works out to about $13.3 million per megawatt ^[17], and the company trades at about 3.9 times the contract's face value ^[18]. With OpenAI's share of Cerebras revenue missing from both reports, the stock's response to Altman is the only gauge in the record of how much of the valuation the market ties to one customer.

Citi's reading is that the Nvidia choice is about sequencing. "We believe frontier-AI labs' latest models would initially roll out on internal chips before running on third-party or Cerebras cloud, so it's too early to read much into it," the analysts said in a note on Friday ^[10], adding that their 2026-2028 revenue view was "unchanged" ^[9]. A second reading is that OpenAI keeps its speed-sensitive products on Nvidia. That would cut against a company whose pitch is that its Wafer Scale Engine 3 runs faster than Nvidia's GPU ^[12], and it would leave the $10 billion as the full size of the relationship. A third is that the margin line matters more than any customer news. Citi puts the stock there: "We believe the stock's ability to outperform is increasingly tied to evidence that gross margins are stabilizing. Any further delay in the gross margin trough would likely weigh on sentiment, particularly given Cerebras' premium valuation," the analysts said ^[11].

I think the second reading is the one the market priced last week. Monday's bounce came from a post that described the relationship without changing its terms. The words quoted from Altman's post mention neither Nvidia nor the Ultrafast mode ^[4][5], and no move of that mode to Cerebras hardware has been reported. The counter-case is Citi's. Revenue forecasts held ^[9], so both the 20% and the 6.3% are sentiment on a stock that gross margins will eventually price. If the next margin report moves the shares more than the Nvidia report or Altman's post did, the single-customer view is wrong.