Cerebras stock did not get saved on Friday night. The regular session closed at $166.43, and that is the last official print until the Monday, Oct. 5, open. It is the lowest close in Nasdaq’s daily series since the May 14, 2026 debut, 19.5% under the prior Friday’s $206.75, and 10.0% under the $185 price on 34.5 million shares. A headline that Sam Altman rescued the stock is treating an extended-hours bounce as a new close. CNBC, updated at 6:38 p.m. ET on Oct. 2, said the shares rose almost 3% after the bell. The post that came before that bounce did not name a model, did not restate a megawatt figure, and did not say a workload was moving back off Nvidia. I am not putting a dollar price on the extended-hours trade. CNBC’s “almost 3%” is the figure, and Monday has not traded.
Monday’s open has to trade three separate things at once. The first is a customer-concentration scare: SemiAnalysis said Ultrafast mode for GPT6.1 Sol is running on Nvidia GPUs, not Cerebras. The second is supply. Up to 19.4 million shares became eligible on Sept. 30, with further waves of about 19.4 million on Oct. 14 and Oct. 28. The third is the multiple, set at $185 and now underneath it. The 3% after-hours bounce prices the reassurance, not the megawatts. Altman did not say the 750-megawatt agreement was intact, and he did not say it was impaired.
Key facts
- Cerebras stock closed Friday, Oct. 2, at $166.43, down 19.5% from $206.75 on Sept. 25. CNBC called the week nearly 20%. Friday is the lowest close since the IPO. The lowest intraday print in the Nasdaq file is $160.81 on June 26.
- CNBC, updated 6:38 p.m. ET, said the shares rose almost 3% in extended trading after Altman’s post. This piece has no Monday, Oct. 5, price.
- The Motley Fool, on Sept. 21, reported the May 14 IPO as 34.5 million shares at $185, raising $6.4 billion. Nasdaq shows a first-day high of $386.34 and a first-day close of $311.07.
- SemiAnalysis posted on X at 6:00 p.m. ET on Tuesday, Sept. 29, that GPT6.1 Sol Ultrafast is not running on Cerebras and is running at a low batch size on Nvidia GPUs.
- Sam Altman posted at 6:19 p.m. ET on Friday: “Cerebras is a close partner, and we have a deep engagement pushing on the frontiers of speed.”
- Up to 19.4 million shares unlocked Sept. 30, CNBC said, citing the prospectus. The Fool’s calendar puts further waves of about 19.4 million on Oct. 14 and Oct. 28, then a final release on the second trading day after third-quarter results or on Nov. 9, whichever is first. No earnings date is treated as scheduled.
- Cerebras’s partnership blog describes 750 megawatts of wafer-scale systems, in stages beginning in 2026. CNBC’s Jan. 14 report said that capacity runs through 2028 and was worth over $10 billion, according to people close to the company.
From a Tuesday post to Friday’s after-hours words
The cash week and the post on X are not the same session. On Tuesday, Sept. 29, Cerebras closed at $194.95, still above the IPO price, on 9.5 million shares. At 6:00 p.m. ET, after that close, SemiAnalysis posted on X: “OpenAI’s latest GPT6.1 Sol Ultrafast is NOT running on Cerebras but is instead running at a low batch size on NVIDIA GPUs.” The post also asked whether Cerebras will serve that tier in the future. CNBC’s Oct. 2 story called the post Wednesday. The timestamp is Tuesday evening, New York time. Wednesday was the first regular session that could trade it.
Wednesday was also a supply date. The Motley Fool, on Sept. 21, had already put about 19.4 million shares on Sept. 30, one of three waves of that size. CNBC, citing the prospectus, said up to 19.4 million shares held by directors, officers, non-executive employees, and non-employee holders unlocked that day, equal to 8% of shares outstanding. The stock opened at $183.69, traded as high as $185.35, and closed at $177.65, down 8.9% on 13.9 million shares. The high tagged $185 and did not hold.
Thursday continued the break. The close was $169.52, down 4.58%, on 12.2 million shares. The high was $184.67, so the session never traded back through $185. FinanceFeeds has already published the Oct. 1 tape and the chief operating officer’s Rule 10b5-1 sale. That note stops before Friday’s close and before Altman’s reply. This one starts from the print those readers did not have.
Friday, Oct. 2, opened at $172.39, traded down to $165.22, and closed at $166.43 on 12.5 million shares, off 1.82% on the day. From the prior Friday’s $206.75, the close-to-close drop is 19.5%. That is the “nearly 20%” in CNBC’s week. It is also the lowest close since the IPO. It is not the lowest price the shares have traded. Nasdaq’s daily lows show $160.81 on June 26. CNBC’s “lowest price since the May IPO” fits the closing series. It does not fit the intraday record.
The first-day high was $386.34 and the first-day close was $311.07. Friday’s $166.43 is 56.9% under that high and 46.5% under that close. CNBC’s line that the stock is down by more than half since the opening pop is true against the high, not against the first close. The regular session was over before anyone read Altman. At 6:19 p.m. ET he posted: “There is some speculation about our partnership with Cerebras. Cerebras is a close partner, and we have a deep engagement pushing on the frontiers of speed.”
What the partnership page still says
Those two sentences are narrower than the recaps. Altman named the speculation, called Cerebras a close partner, and said there is a deep engagement “pushing on the frontiers of speed.” He did not name GPT6.1 Sol, Ultrafast, or Nvidia. He did not say the SemiAnalysis sentence was wrong, and he did not confirm it. The question on that post, whether Cerebras will serve the tier later, is still open in his text.
Cerebras’s partnership blog says OpenAI and Cerebras signed a multi-year agreement to deploy 750 megawatts of wafer-scale systems, rolling out in stages beginning in 2026. CNBC’s Jan. 14 report said the same 750 megawatts run through 2028 and that the arrangement was worth over $10 billion, according to people close to the company. The dollar figure is not in the blog post. Sachin Katti of OpenAI, on that blog, described the deal in portfolio language: “OpenAI’s compute strategy is to build a resilient portfolio that matches the right systems to the right workloads. Cerebras adds a dedicated low-latency inference solution to our platform.” That frames Cerebras as added silicon, not as the only chip on every fast tier.
An April 17 Reuters headline, carried on TradingView and sourced to The Information, said OpenAI would spend more than $20 billion on Cerebras chips and receive an equity stake. The body was not available on Sunday, so that figure stays a headline, not a term read in a contract. It should not be averaged with January’s “over $10 billion.”
What is still on the Cerebras site, fetched Sunday, is a different model string. The Ultrafast blog says Cerebras powers GPT-5.6 Sol on Ultrafast mode in the OpenAI API at up to 750 output tokens per second. GPT-5.6 Sol is not GPT6.1 Sol. CNBC hyphenated the newer name as GPT-6.1. A live page about the earlier tier does not answer a report about the later one.
Nvidia is already in OpenAI’s book. FinanceFeeds has reported that Nvidia’s Ohio guarantee was capped at $105 billion, not $250 billion, and has set OpenAI’s Jalapeño chip against Nvidia Blackwell. A lab that buys wafers, GPUs, and its own silicon can move one tier without tearing up the rest. On the partnership blog and the GPT-5.6 post, there is no sentence confirming or denying the Sept. 29 claim. CNBC’s Friday story does not quote Nvidia claiming the tier. The only new customer words are Altman’s.
The $185 line, the unlock calendar, and Monday
On May 14, 2026, Cerebras sold 34.5 million shares at $185 and raised $6.4 billion, the Motley Fool reported on Sept. 21. That count times $185 is $6.3825 billion. Nasdaq’s first-day high was $386.34 and the close was $311.07, matching the Fool’s peak just above $386. On Sept. 21 the stock was around $199. Friday’s $166.43 is 10.0% under the offer. Reclaiming $185 takes about 11% from that close, more than three times the extended-hours bounce. A Fool widget checked Sunday still showed $166.43, down 1.82%.
The lockup was never one 180-day cliff. The Fool counted 11 dates. The first 10 free about 171 million shares, against about 238 million outstanding, including about 27.7 million after the first-quarter report, about 36.4 million after the second-quarter report, and about 14.6 million on Aug. 19, Sept. 2, and Sept. 16. CNBC said up to 14.6 million shares had unlocked every two weeks since Aug. 19.
Three waves of about 19.4 million were still ahead when the Fool published. Sept. 30 has now happened. Oct. 14 and Oct. 28 are the next two, both Wednesdays, as Sept. 30 was. Monday, Oct. 5, is not on that list. The last release is whichever comes first: the second trading day after third-quarter results, or Nov. 9. As of the Sept. 21 piece the company had not scheduled that report, and nothing verified here adds a date. Altera’s IPO filing, with Intel’s 49% stake, is a different supply story. Cerebras is already unlocking.
The Fool’s about 238 million shares at Friday’s close is about $39.6 billion of arithmetic, beside CNBC’s “just over $39 billion.” CNBC’s first-day $95 billion market cap is not re-derived from that share count. Its 8% claim on Wednesday’s block implies a slightly higher count. Both stay as reported.
The chart is regular-session closes from May 14 through Oct. 2. The dashed line is $185 and Friday’s dot is $166.43. Extended hours are excluded. The table is not a price target.
| Monday path | What would have to be true | What Friday’s evidence is |
|---|---|---|
| Bull: the scare narrowed to one tier | Altman’s post is read as closing the “deal is dead” tail, and one workload is not the 750 megawatts. | He said “close partner” and “frontiers of speed.” He did not restate the megawatts. |
| Bear: workload and float still lead | The open sells a post that did not assign the tier, with $185 overhead and about 19.4 million shares on Oct. 14. | SemiAnalysis is unrebutted on the tier. Wed–Fri volume was 13.9 million, 12.2 million, and 12.5 million shares. |
| Split: tone and terms do not clear together | A reassurance, a share unlock, and an offer price do not have to print on the same side of the open. | No Monday trade exists yet. A nearly 3% extended-hours rise and a 19.5% cash week are both in the record. |
Supply, one customer, and who is speaking
Supply, concentration, and disclosure answer different questions. CNBC reported that chief executive Andrew Feldman and chief technology officer Sean Lie sold over $240 million of Class A shares between Aug. 20 and Sept. 25, under plans adopted shortly after the IPO. Those dates end before the SemiAnalysis post. A plan from just after the May listing is not a comment on a late-September note, and the cash went to the sellers, not into company proceeds. The Wednesday unlock then made up to 19.4 million more shares eligible. Eligibility is not a sale. Wednesday-through-Friday volume is the tape that shows stock changing hands lower.
The Fool put remaining performance obligations at $25.4 billion as of June 30, with a significant share from one customer, OpenAI. A report about one tier can move the equity when the backlog is that concentrated. That is not “the agreement is cancelled.” CNBC’s January piece recalled an older version of the same shape: G42 was 87% of revenue in the first half of 2024. The named counterparty has changed. Dependence on one large customer has not.
Business Insider reported on May 14, 2026, that a court exhibit in Altman’s litigation against Elon Musk showed he held 89,373 Cerebras shares, first taken in February 2017 and marked at $3.2 million at the end of last year on that exhibit. BI also reported a $1 billion OpenAI loan to Cerebras, an option to buy more chips through 2030, and warrants for millions of shares. The 89,373 figure is a May description of an exhibit, not a Form 4 from this week, and it is not evidence he traded around Friday’s post. The tension is structural. The customer’s chief executive is, on that older exhibit, also a shareholder in the supplier. The post is news. It is not a prospectus, and it does not say where GPT6.1 Sol Ultrafast runs.
The chief operating officer’s September sale, under a June 30 Rule 10b5-1 plan and already footnoted on FinanceFeeds, is a scheduled sale. It is not a comment on SemiAnalysis.
What Monday can settle, and what the next waves still own
Monday, Oct. 5, is the first regular session that can trade Altman’s words. This article has no price for it. The paths below are not targets.
The bullish path treats the post as closing the tail that the partnership is over. SemiAnalysis described one tier, GPT6.1 Sol Ultrafast, on Nvidia at a low batch size. The 750-megawatt agreement is a different object, and GPT-5.6 Sol Ultrafast is still described on Cerebras’s site as powered by Cerebras. No new block of about 19.4 million shares unlocks Monday. The next wave is Oct. 14. That buyer is underwriting tone and a calendar gap, still under $185. Touching the offer would take about 11% from Friday’s close. That is the size of the gap, not a forecast that it closes.
The bearish path is that the open sells the post, because the post did not restore the workload. The SemiAnalysis specifics are still unanswered. The lowest close since the IPO is $166.43, June 26’s $160.81 intraday low already printed, and $185 is overhead. Oct. 14 and Oct. 28 still free about 19.4 million shares each on the Fool’s schedule. Failing to trade back through $185 before that wave would mean supply, not the adjective, is setting the price. That is not a call that $160.81 breaks.
Two further waves follow, then a final release on the second trading day after third-quarter results or on Nov. 9, whichever comes first. No third-quarter date was set in the Sept. 21 account, and none is added here. Naming the hardware behind GPT6.1 Sol Ultrafast, or a filing that changes the $25.4 billion backlog, would change the revenue argument. Another “close partner” would not. AMD’s acquisition of Taalas is a separate inference-silicon bid. It does not say where this tier runs.
An extended-hours percentage is a poor stand-in for 750 megawatts. The 3% prices the reassurance. The megawatts are still a document. Cerebras stock goes into Monday with the partnership described, the named workload disputed, and the offer price overhead.
Frequently asked questions
Why is Cerebras stock down?
Cerebras stock fell 19.5% from the Sept. 25 close of $206.75 to Friday’s $166.43. The week put a SemiAnalysis post, saying GPT6.1 Sol Ultrafast is on Nvidia GPUs rather than Cerebras, next to a Sept. 30 unlock of up to 19.4 million shares. The close is 10% under the $185 IPO price and is the lowest close since the May debut. Altman’s Friday post arrived after the bell and did not name the tier SemiAnalysis had described.
What did Sam Altman say?
At 6:19 p.m. ET on Oct. 2 he wrote: “There is some speculation about our partnership with Cerebras. Cerebras is a close partner, and we have a deep engagement pushing on the frontiers of speed.” He did not mention GPT6.1 Sol, Ultrafast, Nvidia, or the 750-megawatt agreement. CNBC said the stock rose almost 3% in extended trading after the post. That move is not a regular-session close, and it is not a Monday print.
Did the after-hours rise put the shares back above $185?
No figure CNBC published does that. The report said the shares rose almost 3% after Friday’s $166.43 close. A gain of about 11% from that close would be required to touch the $185 IPO price. Monday, Oct. 5, had not opened when this was written. The extended-hours percentage is not a new official close, and it is not in the Nasdaq daily series used for the chart.
Is Monday an unlock day for Cerebras?
Not on the schedule the Motley Fool laid out on Sept. 21. About 19.4 million shares were due Sept. 30, and that date has passed. The next waves of about that size are Oct. 14 and Oct. 28, both Wednesdays on the published calendar. Monday, Oct. 5, can still trade shares that became eligible Wednesday. It does not, on that calendar, free a new block at the open.
Did OpenAI cancel the Cerebras agreement?
No source read for this piece says that. Cerebras’s blog still describes a multi-year deployment of 750 megawatts beginning in 2026. CNBC in January put the value at over $10 billion through 2028, citing people close to the company. SemiAnalysis said one later tier, GPT6.1 Sol Ultrafast, is on Nvidia at a low batch size. Altman called Cerebras a close partner and did not confirm or deny that specific sentence.
