【AI Industry clothing remover aiAlert】At 5:55 on May 5th, GPT-5.5 is going to throw itself a party. At that time, GPT-5.5 will choose its own guests, and Codex’s reply to Sam will become the climax of this event. What is even more shocking is that a silent user migration has quietly begun in the AI coding tool circle, with developers switching from Claude Code to Codex.
At 5:55 on May 5th, GPT-5.5 will throw itself a launch party.
That is Beijing time, May 6th, 08:55 to 11:55.
This time is not chosen by Sam Altman, but by GPT-5.5 itself.
Sam Altman said that he will attend the launch celebration, and the model’s response to the invitation was:
“Starting at 5:55 on May 5th, the speech will be brief, and then we will gather GPT-5.6 together.”
Some people say that this gathering is to verify the prediction of GPT-5.6 on PolyMarket, and then bottom out.
What is worth mentioning is that the guest list is so interesting.
Sam, Codex’s reply to him, is also included.
Recently, users have been sending screenshots of the conversation to each other.
Sam replied with a sentence: Elon Musk is also invited, and the world needs more love.
But what Codex replied was not a joke. It was OpenAI’s internal product team directly voting with their feet.
What is even more shocking is that in the past month, a silent user migration has quietly occurred in the AI coding tool circle.
What happened behind the scenes was a silent migration, from Anthropic’s Claude Code to OpenAI’s Codex.
Sam himself posted on April 29th: feels like codex is having a chatgpt moment.
What he meant was that Claude Code’s loyal users are also considering whether they have already switched to Codex.
Codex Surpasses Claude Code
First, look at the data.
Claude Code was the first to reach the ceiling.
Codex has already broken through the ceiling.
Some people say that the model is stronger than Claude, but in fact, Codex won.
Sam’s “chatgpt moment” means that the more professional users use Codex, the more active the migration becomes.
The product positioning of the two is indeed different.
Claude Code takes the “researcher” route, focusing on deep thinking, complex project handling, and high difficulty tasks.
Codex takes the “engineer” route, focusing on fast delivery, quick iteration, and direct access to the market. It is a tool for professional developers.
To be honest, from the data comparison, Codex has 4,600 stars vs Claude Code’s 49 stars. In terms of data, Sam Altman’s tweet timing is indeed accurate: “Data may not be accurate.”
But in fact, Codex’s npm download volume has already completely crushed Claude Code.
From April 17th to May 3rd, the download volume surged, and the growth in the 4 days from April 30th to May 3rd was particularly obvious.
Some people say that users are biased and the actual data is fake. But looking at the data, Codex is indeed on an upward trend.
This trend started on the first day.
But we need to talk about what happened before.
The Outage
It all started on March 23rd.
A post on Reddit r/ClaudeAI sparked a heated discussion.
A Claude Pro user wrote: I’ve used 60% of my session in 3 minutes.
What? 60% of a 5-hour session used up in 3 minutes?
This was just the beginning of the weekend.
A week later, r/ClaudeAI and r/codex were trending at the same time.
A Pro user said: Hello, only 2% left.
A Max 20 user said: One prompt used 21%, reaching 100%.
There is a more extreme case. A user used the `–resume` parameter to restore the session, outputting 652,069 tokens, without any prompt.
A Reddit post with 388 upvotes wrote it very directly: One complex prompt to Claude and by the end you’ve burned 50-70% of your 5-hour limit.
One complex prompt, and 50-70% of the 5-hour limit is gone.
Another user wrote: I used it 8 hours a day.ai porn video generator .. bought two $200/month accounts. Canceled both immediately.
Using it 8 hours a day, buying two $200 accounts, and canceling both immediately.
On March 26th, Anthropic engineer Thariq Shihipar posted on X that the outage had affected about 7% of users.
But the official response was very slow, which angered many people.
On March 31st, Anthropic responded on Reddit:
“People are hitting usage limits in Claude Code way faster than expected. We’re actively investigating… it’s the top priority for the team.”
On the same day, The Register reported it, and the Hacker News homepage had 136 upvotes and 115 comments.
On April 1st, GitHub user @marcuspuchalla submitted issue #41930, directly writing “no formal communication issued.” The next day, Anthropic remained silent.
A Sentinel String
Then users began to discover the real reason.
Claude Code is built on Bun’s runtime, with a size of 228 MB. A group of developers used reverse engineering tools like Ghidra to decompile it, and found a hidden sentinel string inside.
It turns out that Anthropic’s custom Bun fork adds an internal billing sentinel string after every API request, replacing the original prompt cache prefix. This makes the Anthropic API billing system unable to distinguish between cached tokens and uncached tokens, with uncached tokens costing 10 to 20 times more.
The second problem is that the `–resume` / `–continue` flag causes the conversation cache to fail.
The third problem is even more serious. Users thought they were only sending one prompt, but in fact, the conversation history was consuming money. A single conversation trace showed that the internal sentinel string had tricked the prompt cache system.
What is even worse is that this bug was not discovered by Anthropic itself, but by a group of external developers using reverse engineering tools, who then reported it to AI companies and security teams.
On April 8th, Sam Altman posted on X that Codex would return $300 million.
What is even more ironic is that every 100 users get a free quota, directly increasing to 1,000.
At the same time, Anthropic’s engineering team was still fixing that sentinel string.
The April 22nd Pricing Change
Anthropic’s approach was: the model is not the problem, the product positioning is the problem.
The key point is the A/B test on April 22nd.
Claude Code’s $20 Pro tier was removed, and the advanced reasoning model was also removed from Claude Code. Users’ actual token costs far exceeded the $20 limit, and they were forced to bind to the $100/$200 Max plan, with costs completely out of control. Business users were completely lost.
But what Anthropic did not expect was that Claude Code’s slogan was “$20 unlimited Opus,” which was completely false.
Within a few hours, anger on Hacker News and Reddit reached its peak. Simon Willison wrote a very direct sentence in his blog:
“Anthropic inadvertently handed OpenAI a significant marketing advantage.”
This sentence was reposted wildly within a week.
Anthropic rolled back within a few hours, but the Claude Code users who had already been hurt by the $20 plan had already made their choice in their hearts.
OpenAI’s reaction was extremely fast.
Sam replied with two words: ok boomer.
Anthropic’s subsequent attempt to fix the problem: Opus 4.7 increased the token limit to $15/$75, but users’ actual costs still far exceeded the $20 limit.
The engineering team was fixing bugs, but the pricing structure was under pressure.
More importantly, users’ relationship with Claude Code is a product relationship, not a pricing relationship.
The $20 plan is a product promise, and breaking it is a trust breach.
Users are not numbers, they are people.
What Codex Is Really Changing
Let’s look at the bigger picture.
Since the open source release of Codex CLI in April 2025, OpenAI’s Codex has been accelerating.
Every week is a surprise. Every month is a leap.
After the April 16th update, Codex has become a CLI tool, a desktop platform, and a “living activity” with 90 million weekly active users, all connected through the AI Super App.
Greg Brockman said in a speech on April 18th that Codex has moved from “code completion” to “Agentic IDE.”
What is worth mentioning is that Greg himself, as one of the earliest OpenAI executives, switched from Emacs to the terminal to Codex on February 19th.
He is a developer who has used Emacs for decades, saying that this is a completely new platform.
OpenAI’s first stage of the product was to reduce the threshold for every developer. Every line of code is being promoted at the same time.
The second stage is the Codex platform, the desktop. Sam and the team said the same thing: “much more to come.”
But the most important thing is that the entire team is working on the same product at the same time, which is not common in OpenAI’s history.
The last time this happened was when ChatGPT was first released.
But Did Codex Really Win
Let’s look at some real problems.
A poll on dev.to with 500 votes and Reddit’s high-score comments.
In a blind test, Claude Code won 8 out of 12 rounds, with a 67% win rate.
In terms of token efficiency, for the same Express.js refactoring, Codex used 1.5 million tokens, while Claude Code used 6.2 million… four times more.
At first glance, this data is shocking.
But what Codex wins is not “writing better code,” but “writing code faster, cheaper, and more in line with market needs.”
Anthropic has proven over the past year that its model is the champion in “accuracy” and “depth.”
But at this moment, on this track, Codex won in a completely different way. It used low prices to suppress costs, used speed to grab market share, used token efficiency to improve efficiency, and then used stability to retain users.
A user with the ID @d-lo on Hacker News wrote in 4 words:
“I’ve mostly switched to Codex (GPT-5.4 high) over Claude Code (Opus 4.6) in the last few weeks.”
Another user @antoineMoPa wrote more directly:
“Claude has become pretty slow in the last couple of weeks, so I switched to codex.”
These are not marketing-driven migrations, but real user pain points.
On April 29th, Sam Altman posted the key sentence.
“Feels like codex is having a chatgpt moment.”
What does “ChatGPT moment” mean? For OpenAI itself, it means:
On November 30, 2022, when ChatGPT was released, it was not the strongest product, but the first product that ordinary people could use. It broke the threshold from a professional tool to a mass product, and the market structure changed.
The timing of this sentence is also worth noting. On April 29th, exactly one week after Anthropic’s Pro tier rollback.
A week ago, Anthropic was still rolling back on Reddit. A week later, OpenAI’s CEO used a “chatgpt moment” to position his own product.
Greg Brockman also posted a week later, on April 26th, writing: “codex empowers anyone to build.”
The key is “anyone.”
Before this, anyone who wanted to use Claude Code needed a “certificate” — anyone needed $20 and Opus. Now, the threshold is gone.
Back to May 5th at 5:55
Let’s go back to this event, GPT-5.5’s party.
At that time, the model chose its own guests, and Codex replied to Sam, and Elon Musk.
This event is the most symbolic product judgment in the AI circle. OpenAI has positioned Codex as the core of its own product system. In the future, there will be more.
And Anthropic, after the April 22nd rollback and the following week of repeated grinding, has already fallen behind by a full lap. It is building its own product and its own moat.
But in the past year, the path has been proven: a tool company that suddenly becomes good will be completely replaced by a company that is good from the start.
Who writes more beautiful code is not important. Who can become a part of daily work is the real signing page.
This battle has just begun.