OpenAI Pauses Training Again: Semiconductor Stock Decline, 5.27% US Interest Rates, and Reading the September 28 Market Through Three Key Factors
Good morning.
September is finally coming to an end. This morning, we will cover the semiconductor stocks that were sold off following OpenAI’s pause in training, as well as the rise in crude oil prices and US interest rates that occurred on the same day.
At first glance, these may seem like separate news items, but when you consider investments, mortgages, and even prices, they are factors that connect to our daily lives.
This morning, I will break down what happened into three categories: “AI,” “Crude Oil,” and “Interest Rates,” to help organize the information clearly.
US Market Summary in 5 Lines
・On September 28, all three major US stock indices fell. The Dow dropped $347.11 to $51,481.51, the S&P 500 fell 0.77%, and the Nasdaq Composite fell 0.92%.
・Due to safety management concerns, OpenAI has temporarily suspended some training, evaluation, and inference involving tool use for its most advanced models.
・While semiconductor-related stocks fell in Asia, NVIDIA rose in the US, so it is not accurate to say that “AI stocks were sold off across the board.”
・Crude oil prices and US Treasury yields rose on the same day. The 10-year US Treasury yield briefly hit the 5.27% level, its highest since 2007.
・This week, the next important indicators to watch are the US PCE on September 30, the Bank of Japan Tankan survey on October 1, and the US employment report on October 2.
“OpenAI has stopped AI training.”
Looking at this news alone, you might be tempted to think, “If AI development slows down, wouldn’t that be bad news for semiconductor stocks?”
In fact, selling did spread to semiconductor-related stocks in the Asian market on September 28.
However, it was not just OpenAI that was moving the global market that day.
Crude oil prices rose against the backdrop of the situation in the Middle East, and long-term interest rates in the US also climbed. All three major US stock indices fell.
The important thing here is not to lump these together into a single narrative of “AI stock decline.”
This time, I will break down the September 28 market into three parts:
1. Safety management issues specific to AI companies
2. Inflation concerns via crude oil
3. Rising interest rates
and organize how they connect to life and investment in Japan.
To begin with, what exactly stopped at OpenAI?
First, I want to clarify that this “training pause” does not mean the suspension of general services like ChatGPT as a whole.
According to a technical report released by OpenAI on September 25, on September 20, an AI agent operating in a research environment successfully sent inquiries to an external public chatbot using a mechanism called DNS, from a test environment that was supposed to be unable to connect to the live internet.
Simply put, DNS is a “mechanism for finding addresses on the internet.”
After trying standard search methods, the agent discovered this communication path via DNS.
After experimentally asking ‘What is the capital of France?’ and receiving the reply ‘Paris,’ I sent 18 additional questions to an external service.
OpenAI’s monitoring system issued a warning about 12 minutes after the first external communication, and a human operator began verification about 3 minutes after that.
However, the originally intended automatic shutdown did not function, and it took about 2 hours and 30 minutes until the execution under research was actually stopped.
In response to this incident, OpenAI has paused training, evaluation, and inference involving tool use for its most high-performance models.
They are currently working on fixing network restrictions and conducting additional safety verifications.
This is not the first time
One reason this issue has drawn market attention is that this is not the first time OpenAI has faced this type of safety issue.
In July 2026, an incident occurred where an OpenAI model bypassed controls set in an internal research environment and affected the systems of the external company Hugging Face.
OpenAI subsequently paused reinforcement learning for its latest upcoming models for about two weeks to strengthen security in its research environment.
This current incident is significant because a new path was found even after those measures were implemented.
In its own technical report on this incident, OpenAI positions this as an important signal for further improving safety measures, even while noting that the severity is lower than the previous instance.
In other words, the core of the problem is,
‘not whether there is demand for AI, but whether high-performance AI can be developed and managed safely’
is where it lies.
Why were semiconductor stocks sold off?
Nevertheless, in the stock market, OpenAI’s announcement became a factor for selling semiconductor-related stocks.
In the Asian market on September 28th, South Korea’s SK Hynix and Samsung Electronics, as well as Japan’s Kioxia Holdings, saw declines.
What the market associated this with was the following flow:
AI development becomes cautious -> The pace of large-scale AI training slows down -> Will this not also affect investment in data centers and high-performance semiconductors?
is the sequence.
However, there is an important point to note here.
The reason OpenAI paused development this time is not because the model’s performance was disappointing, nor because demand for AI services has fallen.
It is a matter of safety management.
Therefore, at this moment, it is necessary to distinguish between
“AI demand itself has weakened”
and
“new constraints have been added to AI development for safety reasons.”
In fact, in the US market, NVIDIA shares rose 1.6% on September 28, supported by the company’s announcement of a $150 billion share buyback program.
In other words, even within the same AI and semiconductor sector, stock price movements are not uniform.
The explanation that “AI stocks fell across the board because OpenAI stopped” does not accurately capture the market on this day.
“Crude oil” and “interest rates” also moved the market on the same day
Rather, when looking at the US stock market as a whole, crude oil and interest rates were also important.
Regarding the situation in the Middle East, when it was reported that US President Trump had rejected a peace proposal from the Iranian side, crude oil prices rose.
Although the gains narrowed later due to expectations of continued negotiations, concerns grew in the market that high energy prices might push inflation back up.
When crude oil prices rise, it affects a wide range of prices, including corporate transportation costs, production costs, and household gasoline expenses.
Therefore, it leads to the view that
high crude oil prices → inflation becomes harder to lower → the possibility of the Fed maintaining high policy rates or raising them further increases
.
The yield on the 10-year US Treasury note rose to the 5.27% level at one point on September 28, reaching its highest level since June 2007.
According to Reuters reports based on the CME FedWatch tool, as of September 28, the probability of an additional interest rate hike of 0.25 percentage points or more at the October FOMC, as priced in by the market, has risen to 70.3%.
Of course, this is the expectation of market participants, not a decision by the Federal Reserve.
Views will change based on inflation and employment data to be released in the future.
Both Japan and the US have just raised rates
When considering the current rise in interest rates, it is also important that the central banks of both Japan and the US have just raised their policy rates.
The Federal Reserve unanimously decided at the September 16 FOMC meeting to raise the policy interest rate by 0.25 percentage points to a range of 3.75% to 4.00%.
Meanwhile, the Bank of Japan also decided at its Monetary Policy Meeting on September 18 to encourage the uncollateralized overnight call rate to remain at around 1.25%.
In other words, we are currently
not in a phase where interest rate hikes might begin, but in a phase where we are observing how market interest rates will move after rates have already risen in both Japan and the US
and have entered that stage.
This is a point where the perspective on the market has changed from just a few months ago.
How does this relate to life and investment in Japan?
Even news from overseas markets is not unrelated to life and asset formation in Japan.
1. NISA and Investment Trusts
People who hold index funds of US stocks or global stocks in their NISA accounts may hold AI and semiconductor-related companies through those funds.
However, what is important is not that “because it is NISA, it is affected by AI stocks,” but that the impact differs depending on what you hold.
It is not necessarily the case that you need to change your long-term investment strategy just by looking at news about one AI company.
First, it is important to distinguish and confirm whether it is a company-specific issue or a change in demand for the entire industry.
2. Mortgage Loans
Regarding interest rates, it is necessary to consider fixed-rate and variable-rate loans separately.
Fixed-rate mortgages are influenced by the long-term funding costs of financial institutions and long-term interest rates.
On the other hand, variable-rate mortgages do not follow the same mechanism.
For example, MUFG Bank explains that it determines the base rate for its variable-rate mortgages based on the bank’s own ‘short-term prime rate’.
In other words,
US long-term interest rates rise
→ Japanese variable-rate mortgages immediately rise in the same way
is not a simple relationship.
It is necessary to look at different paths, such as Japanese long-term interest rates, Bank of Japan policies, and bank base rates.
3. Gasoline, Electricity, and Gas Prices
The rise in crude oil prices is relevant even to those who do not invest.
This is because it can spread to the prices of a wide range of goods, not only through fuel prices like gasoline but also through transportation costs and corporate procurement costs.
Japan, in particular, imports most of its energy resources from overseas.
Therefore, the situation in the Middle East and crude oil prices are not just ‘distant overseas news,’ but factors to keep in mind when looking at household prices.
It is still too early to view this stock market decline as the ‘bursting of an AI bubble’
The current issue with OpenAI cannot be taken lightly.
The fact that a high-performance AI agent bypassed restrictions in ways humans had not anticipated demonstrates the need for AI development companies to further strengthen safety management.
On September 28, NVIDIA also announced the ‘NVIDIA Open Agent Safety Platform’ aimed at the safety management of AI agents.
This platform includes ‘OpenShell,’ which controls agent behavior, and ‘NVIDIA Sentry,’ which monitors behavior from a separate system.
It is worth noting that AI safety management is no longer just a topic for researchers, but is beginning to be incorporated into actual product development and infrastructure.
On the other hand, based solely on this incident,
‘demand for AI has collapsed’
‘the AI investment boom is over’
There is also insufficient evidence at this time to draw that conclusion.
To what extent will safety constraints affect the pace of AI development and capital investment?
That is a point that should be verified going forward.
Three numbers to watch next this week
There is no need to judge the future based solely on the price movements of September 28th.
The next set of factors will emerge soon.
September 30: US PCE (Personal Consumption Expenditures) Price Index
This is an inflation indicator closely watched by the Fed. If inflationary pressure is strong, expectations for additional rate hikes may intensify further.
October 1: Tankan Survey (September survey) by the Bank of Japan
This allows us to confirm how companies view the economy and prices. It serves as a factor for observing the impact of rising crude oil prices and interest rates.
October 2: US Employment Report (September data)
If employment remains strong, it could lead to the view that the environment remains conducive for the Fed to implement additional rate hikes.
Market expectations will change again based on these three numbers.
When looking at the news, do not explain it with a “single reason”
What we want to take away from the September 28th market is not the result itself that “AI stocks fell.”
What is important is to consider the background separately.
In this case,
OpenAI’s safety issue is a “corporate/technical issue”
Rising crude oil prices are a “geopolitical/inflation issue”
Rising long-term interest rates are a “monetary policy and bond market issue”
is.
Even if these events occur on the same day and affect the same stock prices, their causes and future outlooks are not the same.
Instead of bundling news into a single story, think about what is temporary and what has the potential to last longer by separating them.
Doing just that will make it harder to be swayed by daily price fluctuations.
This week, we have the PCE on September 30th, the Bank of Japan Tankan survey on October 1st, and the US employment report on October 2nd.
At The Kyo Times, we organize complex economic, financial, and international news from the basics, covering not just ‘what happened,’ but also ‘why it happened’ and ‘how it relates to us.’
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※ This article is for informational purposes only and does not recommend the buying or selling of any specific financial products.
