Campaigners for Britons in the European Union reacted furiously on Friday to the deal struck in the first phase of Brexit negotiations between Britain and the bloc, while advocates for EU citizens called it "a flawed compromise".
The agreement said both sides had reached a "common understanding" that all EU citizens would have the right to continue living and working where they reside when Britain withdraws from the bloc in 2019.
The deal, spelled out in a joint report published by the European Commission, also protects the rights of people who have not yet been granted permanent residency in Britain so they can still acquire it after withdrawal.
It also includes future family reunification rights for relatives, including spouses, parents, grandparents, children and grandchildren, an issue which had been a major sticking point in the negotiations.
On the contentious issue of legal jurisdiction, it said British courts would enforce the rights of EU citizens but judges could refer cases to the European Court of Justice for eight years after withdrawal.
But the agreement gave Britons living in EU countries no guarantees for automatic residency rights and free movement beyond any transition period, leaving advocates incredulous.
"This deal is even worse than we expected," said Jane Golding, chair of the British in Europe coalition.
"After 18 months of wrangling the UK and EU have sold 4.5 million people down the river in a grubby bargain that will have a severe impact on ordinary people's ability to live their lives as we do now," she said, referring to the total estimated number of British and European citizens impacted.
Guy Verhofstadt, the European Parliament's Brexit coordinator, also underlined that five outstanding issues remained for the final phase of the withdrawal talks, including guaranteeing British citizens future rights on free movement across the bloc.
About 3.7 million people living in the UK are citizens of another EU country, according to data from Britain's Office of National Statistics covering the year to June 2017.
Some 900,000 Britons live in other member state countries, according to a current estimate based on official data from 2010/2011.
British Prime Minister Theresa May hailed the agreement as allowing these expatriate citizens caught on different sides of the Brexit divide "to go on living their lives as before" when Britain leaves.
But representatives for Europeans in Britain impacted by Brexit said the proposals still left them in uncertainty.
"Today’s agreement... has not reassured EU citizens living in the UK," said Maike Bohn of The 3 Million, the largest grassroots organisation of EU citizens living in Britain, calling it a "flawed compromise".
"There is some progress on the substance of rights but some of the concessions come with a time limit," she said.
Campaigners are most concerned that the deal greenlights British proposals requiring people to apply for the right to stay.
The current registration system has a 10 percent error rate and has rejected more than a quarter of cases, according to The 3 Million.
"There are a huge number of people still in the dark about whether they will qualify or not," said Nicolas Hatton, the group's chairman.
"Hundreds and thousands of them might get a letter that they have to go."
Joan Pons, a Spanish nurse working in England, described the deal as "a house of cards that could crumble in the next phase."
He fears in particular the time limit placed on the ability to refer cases to the European Court of Justice, after which politics could change the consensus.
"May said that my life would be exactly the same after Brexit, and it's not true," Pons said.
"I don't trust May at all."
Academics tracking the negotiations had a mixed reaction to the proposals.
"On citizens' rights she's got a really good deal... far better than I thought she'd get," said Anand Menon, a professor of European politics at King's College London.
That view was echoed by his colleague Jonathan Portes, a professor of economics, who said it went "a considerable way towards resolving the uncertainty" hanging over those affected.
But Stijn Smismans, a professor of law at Cardiff University, said progress had been modest, identifying three problematic areas: ambiguity over the status EU residents will get post-Brexit, issues over the registration system they will use, and their long-term legal protections.