Before the election, Nicole Manion and her boss joked about whether a Donald Trump victory would mean shed have to leave her tech job in Seattle and go home to Toronto. The ribbing has stopped.

The future of Manion, an analyst for a marketing-software company, is suddenly in jeopardy. She works in the U.S. on a special visa for Canadians and Mexicans that owes its existence to NAFTA, the continental free-trade deal the president-elect has threatened to rip up. To move here was always a dream of mine, she says. I always saw the States as that big brother, the land of opportunity, especially in tech. Do I go back to Toronto and start again, try and rebuild what Ive accomplished here? Or do I stay and run the risk?

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Tens of thousands of people working in the U.S. tech industry on temporary visas are, like Manion, suddenly thinking more seriously about whether their adopted country will still want them under President Trump. The former Apprentice host said on Nov. 9 that sweeping changes to U.S. immigration policy rank among his top three priorities, and hes surrounding himself with advisers and backers who take pride in their strict views on the issue, including Republican Senators Jeff Sessions of Alabama and Chuck Grassley of Iowa.

So far, though, Trump has been light on specifics, leaving workers and immigration advocates to scrutinize a handful of statements for clues. Hes said he will end forever the use of cheaper labor from the H-1B worker program, a lottery system thats a principal source of visas for tech workers, as an alternative to hiring U.S. citizens. But hes also said Silicon Valley and the U.S. in general need to bring talented workers into the country. Usually we have a much better sense for what the president-elect is going to focus on and where its going to take us, says Peter Leroe-Muoz, vice president for technology and innovation policy at the Silicon Valley Leadership Group, a regional lobbying organization.

The Valley would be the first to suffer if it got harder to come to America or if increasing xenophobia made fewer people want to, says investor Paul Graham, co-founder of startup accelerator Y Combinator. More than half the U.S. startups worth at least $1 billion have an immigrant founder, and the companies getting the most H-1B visas each yearabout 80,000 are grantedinclude Amazon.com and Microsoft. Facebook Chief Executive Officer Mark Zuckerberg has been lobbying Congress for an expansion of the H-1B quota. Now maintaining the status quo seems optimistic.

Another Silicon Valley immigration prioritywork authorizations for foreigners looking to start their own companies instead of working for someone elsesis also vulnerable. A recently proposed entrepreneurial parole from the U.S. Citizenship and Immigration Services, prompted by a memo from President Obama, would allow entrepreneurs to stay several years in the country if they meet certain thresholds for funding and job creation. Its a likely target for Trump, whos vowed to erase Obamas unilateral executive actions.

Abhishek Kona, a 28-year-old Indian software engineer at Bright, a solar panel maker in San Francisco, says hes putting the dream of having his own company aside for now to hang on to his employer-sponsored visa. Some other workers were scared to give their names. Another Indian expat, who works for delivery startup Postmates, says he and his wife are no longer looking to buy a home, as they were before the election. Instead, theyre questioning things they never had before, such as whether they want to raise their young son in the U.S. Daniel, an Israeli-Canadian who works at an international tech company in the Valley, was planning to move from San Francisco to New York next year with his boyfriend. Now theyre making plans to return to Canada or possibly move to Europe.

BlackBerry CEO John Chen, who lives in the Bay Area, says he hopes Trumps promise to crack down on the visa program was just bluster. It would really hurt the country in a profound way, says Chen, a Republican who immigrated to the U.S. from Hong Kong as a student and served on President George W. Bushs advisory council on exports. Either way, Trumps election is changing considerations for the next group of potential foreign hires, says Ava Benach, founding partner of Benach Collopy, an immigration law firm in Washington. If youre a U.S. tech company, your recruitment just got a lot harder, she says. Finding people who want to come to the U.S. now may be more difficult. People who have brown skin might feel pretty uncomfortable coming to the U.S. under these circumstances.

Some Valley investors are trying to insulate companies in their portfolios from the Trump administrations undetermined policies. Charles River Ventures, an early-stage investment firm, said this summer it plans to pay the legal fees required to keep the founders its backed in the country. Saar Gur, managing partner, says hes concerned the firm wont be able to continue to attract foreign talent of the same caliber. We regularly find two guys working at a desk somewhere and sell them on coming to the U.S., he says. What scares me now are those immigrants we arent going to be able to get.

Silicon Valley is still the best place in the world to work in tech, but things arent the same, says Can Duruk, a Turkish software engineer for Uber. He just got his green card after six years on an H-1B visa. But hes still worried about the possibilities for immigrants in the U.S. This country has elected someone who was more or less openly racist at points, Duruk says, comparing Trumps attitude and rise to the repressive Turkish President Recep Tayyip Erdogan. It feels like a punch in the stomach.

The bottom line: Trumps visa policies are far from settled, but the tens of thousands of U.S. tech workers dependent on them have reason to worry.

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