When Sundar Pichai, Google’s chief executive, introduced a generative artificial intelligence feature for the company’s search engine last month, he and his colleagues demonstrated the new capability with six text-based queries that the public could try out.

The questions included “how do you clean a fabric sofa” and “what should I use to get a coffee stain out of my carpet.” These were intended to highlight how Google’s new feature, A.I. Overviews, could generate full and useful information summaries above traditional search results.

But by Friday, only one of the six queries still yielded an A.I. Overview, according to tests by The New York Times. Instead, the feature was noticeably less prevalent. The search for “what should I use to get a coffee stain out of my carpet” now resulted in a snippet of text from a website, JDog Carpet Cleaning & Floor Care, while “how do you clean a fabric sofa” was replaced by a link to HGTV’s website with the answer. (The results of the searches may vary depending on the user and location.)

The disappearance of A.I. Overviews for some of the searches appeared to be part of a broader rollback after the new technology produced a litany of untruths and errors — including recommending glue as part of a pizza recipe and suggesting that people ingest rocks for nutrients. Users loudly complained on social media about the mistakes, in many cases outright making fun of Google.

Liz Reid, who was recently promoted to Google’s head of search, wrote in a blog post on Thursday that the company had pared back A.I. Overviews in certain ways, launching “additional triggering refinements” to offer more careful responses about health, disabling misleading advice and limiting the inclusion of satire and user responses from forums like Reddit.

“We’ll keep improving when and how we show AI Overviews and strengthening our protections,” she wrote, adding that Google was working on updates to improve broad sets of search results.

Ashley Thompson, a Google spokeswoman, said in a statement on Friday that the company had made more than a dozen technical updates to its systems.

“A.I. Overviews are helping people on a large number of queries on Search today, serving as a jumping-off point to content across the web.” The company added that while it was making adjustments to improve A.I. Overviews, it was not pulling back from the feature for the long term.

The backtracking was a blow to Google’s efforts to keep up with its rivals Microsoft and OpenAI, the maker of the ChatGPT chatbot, in the frenzied race to lead A.I. It also underscored the difficult strategic choice that Google faces over whether to embrace A.I. technology that may not be dependable, or keep its highly popular search engine the same — and risk falling behind its peers.

Google had chosen to go slower than Microsoft, which placed more conversational A.I. into its Bing search engine early last year. Google, which has significantly more users than Bing, tested A.I. features for its search engine a year before introducing A.I. Overviews. The company said the new feature would be rolled out to users in the United States immediately and to more than a billion people by the end of the year.

But ultimately, Google ”should have rolled this out more slowly,” said Patrick Hall, an assistant professor of decision sciences at the George Washington University School of Business. “Once something like this happens, you really have to retreat. And if nothing else, there’s reputational harm” to the company.

Google, which has led internet search for more than two decades, has scrambled since OpenAI released ChatGPT in 2022. Some tech industry insiders considered the chatbot’s ability to generate answers to be a serious threat to Google’s search engine, which has been the most popular way to get information online.

Since then, Google has aggressively worked to regain its advantage in A.I., releasing a family of technology named Gemini, including new A.I. models for developers. The company also infused the technology into YouTube, Gmail and Docs, helping users create videos, emails and drafts with less effort.

Last month, Ms. Reid said at Google’s developer conference that the search engine would do more of the googling for users with A.I. Overviews. She highlighted increasingly complex requests that Google could answer with the feature, but those capabilities have not yet been launched for users.

Onstage, simpler questions like “how do I get the smell of a campfire out of my clothes” yielded A.I. answers including air it out, add baking soda and spray with lemon juice.

But when users got their hands on the new service, they found that A.I. Overviews sometimes generated wrong — or downright dangerous — answers, including recommending putting nontoxic glue on pizza to make the cheese stick. It also misunderstood some websites it was quoting and got presidential history wrong.

Of the six questions that Google launched for the public, the only one that consistently triggered an A.I. Overview on Friday was “what are interesting science projects I can do with my son who is 12 years old.”

The answer? Growing crystals, extracting DNA from saliva and writing a message with invisible ink.

When Frank Pine searched Google for a link to a news article two months ago, he encountered paragraphs generated by artificial intelligence about the topic at the top of his results. To see what he wanted, he had to scroll past them.

That experience annoyed Mr. Pine, the executive editor of Media News Group and Tribune Publishing, which own 68 daily newspapers across the country. Now, those paragraphs scare him.

In May, Google announced that the A.I.-generated summaries, which compile content from news sites and blogs on the topic being searched, would be made available to everyone in the United States. And that change has Mr. Pine and many other publishing executives worried that the paragraphs pose a big danger to their brittle business model, by sharply reducing the amount of traffic to their sites from Google.

“It potentially chokes off the original creators of the content,” Mr. Pine said. The feature, AI Overviews, felt like another step toward generative A.I. replacing “the publications that they have cannibalized,” he added.

Media executives said in interviews that Google had left them in a vexing position. They want their sites listed in Google’s search results, which for some outlets can generate more than half of their traffic. But doing that means Google can use their content in AI Overviews summaries.

Publishers could also try to protect their content from Google by forbidding its web crawler from sharing any content snippets from their sites. But then their links would show up without any description, making people less likely to click.

Another alternative — refusing to be indexed by Google, and not appearing on its search engine at all — could be fatal to their business, they said.

“We can’t do that, at least for now,” said Renn Turiano, the head of product at Gannett, the country’s largest newspaper publisher.

Yet AI Overviews, he said, “is greatly detrimental to everyone apart from Google, but especially to consumers, smaller publishers and businesses large and small that use search results.”

Google said its search engine continued to send billions of visits to websites, providing value to publishers. The company has also said it has not showcased its A.I. summaries when it was clear that users were looking for news on current events.

Liz Reid, Google’s vice president of search, said in an interview before the introduction of AI Overviews that there were hopeful signs for publishers during testing.

“We do continue to see that people often do click on the links in AI Overviews and explore,” she said. “A website that appears in the AI Overview actually gets more traffic” than one with just a traditional blue link.

On Thursday afternoon, Ms. Reid wrote in a blog post that Google would limit AI Overviews to a smaller set of search results after it produced some high-profile errors, but added that the company was still committed to improving the system.

The A.I.-generated summaries are the latest area of tension between tech companies and publishers. The use of articles from news sites has also set off a legal fight over whether companies like OpenAI and Google violated copyright law by taking the content without permission to build their A.I. models.

The New York Times sued OpenAI and its partner, Microsoft, in December, claiming copyright infringement of news content related to the training and servicing of A.I. systems. Seven newspapers owned by Media News Group and Tribune Publishing, including The Chicago Tribune, brought a similar suit against the same tech companies. OpenAI and Microsoft have denied any wrongdoing.

AI Overviews is Google’s latest attempt to catch up to rivals Microsoft and OpenAI, the maker of ChatGPT, in the A.I. race.

More than a year ago, Microsoft put generative A.I. at the heart of its search engine, Bing. Google, afraid to mess with its cash cow, initially took a more cautious approach. But the company announced an aggressive rollout for the A.I. feature at its annual developer conference in mid-May: By the end of the year, more than a billion people would have access to the technology.

AI Overviews combine statements generated from A.I. models with snippets of content from live links across the web. The summaries often contain excerpts from multiple websites while citing sources, giving comprehensive answers without the user ever having to click to another page.

Since its debut, the tool has not always been able to differentiate between accurate articles and satirical posts. When it recommended that users put glue on pizza or eat rocks for a balanced diet, it caused a furor online.

Publishers said in interviews that it was too early to see a difference in traffic from Google since AI Overviews arrived. But the News/Media Alliance, a trade group of 2,000 newspapers, has sent a letter to the Justice Department and the Federal Trade Commission urging the agencies to investigate Google’s “misappropriation” of news content and stop the company from rolling out AI Overviews.

Many publishers said the rollout underscored the need to develop direct relationships with readers, including getting more people to sign up for digital subscriptions and visit their sites and apps directly, and be less reliant on search engines.

Nicholas Thompson, the chief executive of The Atlantic, said his magazine was investing more in all the areas where it had a direct relationship to readers, such as email newsletters.

Newspapers such as The Washington Post and The Texas Tribune have turned to a marketing start-up, Subtext, that helps companies connect with subscribers and audiences through text messaging.

Mike Donoghue, Subtext’s chief executive, said media companies were no longer chasing the largest audiences, but were trying to keep their biggest fans engaged. The New York Post, one of his customers, lets readers exchange text messages with sports reporters on staff as an exclusive subscriber benefit.

Then there’s the dispute over copyright. It took an unexpected turn when OpenAI, which scraped news sites to build ChatGPT, started cutting deals with publishers. It said it would pay companies, including The Associated Press, The Atlantic and News Corp., which owns The Wall Street Journal, to access their content. But Google, whose ad technology helps publishers make money, has not yet signed similar deals. The internet giant has long resisted calls to compensate media companies for their content, arguing that such payments would undermine the nature of the open web.

“You can’t opt out of the future, and this is the future,” said Roger Lynch, the chief executive of Condé Nast, whose magazines include The New Yorker and Vogue. “I’m not disputing whether it will happen or whether it should happen, only that it should happen on terms that will protect creators.”

He said search remained “the lifeblood and majority of traffic” for publishers and suggested that the solution to their woes could come from Congress. He has asked lawmakers in Washington to clarify that the use of content for training A.I. is not “fair use” under existing copyright law and requires a licensing fee.

Mr. Thompson of The Atlantic, whose publication announced a deal with OpenAI on Wednesday, still wishes Google would pay publishers as well. While waiting, he said before the rollout of AI Overviews that despite industry concerns, The Atlantic wanted to be part of Google’s summaries “as much as possible.”

“We know traffic will go down as Google makes this transition,” he said, “but I think that being part of the new product will help us minimize how much it goes down.”

David McCabe contributed reporting.

When Mark Zuckerberg, the chief executive of Meta, announced last year that his company would release an artificial intelligence system, Jeffrey Emanuel had reservations.

Mr. Emanuel, a part-time hacker and full-time A.I. enthusiast, had tinkered with “closed” A.I. models, including OpenAI’s, meaning the systems’ underlying code could not be accessed or modified. When Mr. Zuckerberg introduced Meta’s A.I. system by invitation only to a handful of academics, Mr. Emanuel was concerned that the technology would remain limited to just a small circle of people.

But in a release last summer of an updated A.I. system, Mr. Zuckerberg made the code “open source” so that it could be freely copied, modified and reused by anyone.

Mr. Emanuel, the founder of the blockchain start-up Pastel Network, was sold. He said he appreciated that Meta’s A.I. system was powerful and easy to use. Most of all, he loved how Mr. Zuckerberg was espousing the hacker code of making the technology freely available — largely the opposite of what Google, OpenAI and Microsoft have done.

“We have this champion in Zuckerberg,” Mr. Emanuel, 42, said. “Thank God we have someone to protect the open-source ethos from these other big companies.”

Mr. Zuckerberg has become the highest-profile technology executive to support and promote the open-source model for A.I. That has put the 40-year-old billionaire squarely on one end of a divisive debate over whether the potentially world-changing technology is too dangerous to be made available to any coder who wants it.

Microsoft, OpenAI and Google have more of a closed A.I. strategy to guard their tech, out of what they say is an abundance of caution. But Mr. Zuckerberg has loudly stood behind how the technology should be open to all.

“This technology is so important, and the opportunities are so great, that we should open source and make it as widely available as we responsibly can, so that way everyone can benefit,” he said in an Instagram video in January.

That stance has turned Mr. Zuckerberg into the unlikely man of the hour in many Silicon Valley developer communities, prompting talk of a “glow-up” and a kind of “Zuckaissance.” Even as the chief executive continues grappling with scrutiny over misinformation and child safety issues on Meta’s platforms, many engineers, coders, technologists and others have embraced his position on making A.I. available to the masses.

Since Meta’s first fully open-source A.I. model, called LLaMA 2, was released in July, the software has been downloaded more than 180 million times, the company said. A more powerful version of the model, LLaMA 3, which was released in April, reached the top of the download charts on Hugging Face, a community site for A.I. code, at record speed.

Developers have created tens of thousands of their own customized A.I. programs on top of Meta’s A.I. software to perform everything from helping clinicians read radiology scans to creating scores of digital chatbot assistants.

“I told Mark, I think that open sourcing LLaMA is the most popular thing that Facebook has done in the tech community — ever,” said Patrick Collison, chief executive of the payments company Stripe, who recently joined a Meta strategic advisory group that is aimed at helping the company make strategic decisions about its A.I. technology. Meta owns Facebook, Instagram and other apps.

Mr. Zuckerberg’s new popularity in tech circles is striking because of his fraught history with developers. Over two decades, Meta has sometimes pulled the rug out from under coders. In 2013, for instance, Mr. Zuckerberg bought Parse, a company that built developer tools, to attract coders to build apps for Facebook’s platform. Three years later, he shuttered the effort, angering developers who had invested their time and energy in the project.

A spokeswoman for Mr. Zuckerberg and Meta declined to comment. (The New York Times last year sued OpenAI and its partner, Microsoft, claiming copyright infringement of news content related to A.I. systems.)

Open-source software has a long and storied history in Silicon Valley, with major tech battles revolving around open versus proprietary — or closed — systems.

In the internet’s early days, Microsoft jockeyed to provide the software that ran internet infrastructure, only to eventually lose out to open-source software projects. More recently, Google open sourced its Android mobile operating system to take on Apple’s closed iPhone operating system. Firefox, the internet browser, WordPress, a blogging platform, and Blender, a popular set of animation software tools, were all built using open-source technologies.

Mr. Zuckerberg, who founded Facebook in 2004, has long backed open-source technology. In 2011, Facebook started the Open Compute Project, a nonprofit that freely shares designs of servers and equipment inside data centers. In 2016, Facebook also developed Pytorch, an open-source software library that has been widely used to create A.I. applications. The company is also sharing blueprints of computing chips that it has developed.

“Mark is a great student of history,” said Daniel Ek, Spotify’s chief executive, who considers Mr. Zuckerberg a confidant. “Over time in the computing industry, he’s seen that there’s always been closed and open paths to take. And he has always defaulted to open.”

At Meta, the decision to open source its A.I. was contentious. In 2022 and 2023, the company’s policy and legal teams supported a more conservative approach to releasing the software, fearing a backlash among regulators in Washington and the European Union. But Meta technologists like Yann LeCun and Joelle Pineau, who spearhead A.I. research, pushed the open model, which they argued would better benefit the company in the long term.

The engineers won. Mr. Zuckerberg agreed that if the code was open, it could be improved and safeguarded faster, he said in a post last year on his Facebook page.

While open sourcing LLaMA means giving away computer code that Meta spent billions of dollars to create with no immediate return on investment, Mr. Zuckerberg calls it “good business.” As more developers use Meta’s software and hardware tools, the more likely they are to become invested in its technology ecosystem, which helps entrench the company.

The technology has also helped Meta improve its own internal A.I. systems, aiding ad targeting and recommendations of more relevant content on Meta’s apps.

“It is 100 percent aligned with Zuckerberg’s incentives and how it can benefit Meta,” said Nur Ahmed, a researcher at MIT Sloan who studies A.I. “LLaMA is a win-win for everybody.”

Competitors are taking note. In February, Google open sourced the code for two A.I. models, Gemma 2B and Gemma 7B, a sign that it was feeling the heat from Mr. Zuckerberg’s open-source approach. Google did not respond to requests for comment. Other companies, including Microsoft, Mistral, Snowflake and Databricks, have also started offering open-source models this year.

For some coders, Mr. Zuckerberg’s A.I. approach hasn’t erased all of the baggage of the past. Sam McLeod, 35, a software developer in Melbourne, Australia, deleted his Facebook accounts years ago after growing uncomfortable with the company’s track record on user privacy and other factors.

But more recently, he said, he recognized that Mr. Zuckerberg had released “cutting edge” open-source software models with “permissive licensing terms,” something that can’t be said for other big tech companies.

Matt Shumer, 24, a developer in New York, said he had used closed A.I. models from Mistral and OpenAI to power digital assistants for his start-up, HyperWrite. But after Meta released its updated open-source A.I. model last month, Mr. Shumer started relying heavily on that instead. Whatever reservations he had about Mr. Zuckerberg are in the past.

“Developers have started to see past a lot of issues they’ve had with him and Facebook,” Mr. Shumer said. “Right now, what he’s doing is genuinely good for the open-source community.”