China has promised "consequences" for Taiwan's presence at the Pacific Islands Forum opening ceremony, which put the two rivals in the same room.
Palau's National Gymnasium in Koror was the unlikely venue for the geopolitical flashpoint on Monday night.
On the stage were traditional dancers, Pacific leaders and speeches pleading for unity and climate action.
And in the audience, along with Australia Prime Minister Anthony Albanese and other regional leaders, were delegates from external powers - including the two bitter enemies.
Palau is one of just 12 nations that recognise Taiwan, rather than Beijing, and Taipei has used the Micronesian nation's hosting rights to engage in diplomatic efforts.
That outreach extended to Foreign Minister Lin Chia-lung attending the opening ceremony on Monday night, prompting a stern reaction from Chinese officials.
China's Pacific envoy, Qian Bo, said he had lodged diplomatic objections at Taiwan's presence at the summit.
"We certainly have serious concern," he told journalists.
"We have made our position very clear to the government of Palau and the (Pacific Islands Forum) secretariat."
Asked if there would be consequences, Mr Qian said "there will always be consequences".
"It should not have happened. We think it's very inappropriate," he said.
China and Taiwan share an unresolvable problem, with Beijing believing the US-backed island is an inalienable part of its territory, and Taipei claiming it is sovereign.
Beijing uses fierce diplomacy to subdue Taiwan's claims, urging other nations to acknowledge the "One China" principle, which asserts its authority.
This prevents the vast majority of governments from political engagement with Taiwan, though many nations - including Australia - hold strong economic links.
There is no PIF rule that prevents Taiwan's presence, with Palau President Surangel Whipps offering a pointed rebuke to countries looking to control the region.
"The world increasingly recognises the strategic important of our region and we welcome friends and genuine partnerships," he said in his opening address.
"Our partners are welcome to sail with us, but they do not chose our destination.
"The Pacific agenda must be driven by us, for us, and the Forum must remain the political home in which that agenda is shaped."
There is a distinction between the nations' status within PIF, with China a "dialogue partner" which can sit around the table at formal sessions, and Taiwan a "development partner" with lesser rights.
While a diplomatic clash in Palau felt somewhat inevitable, it is not yet clear what the fallout will be.
PIF members are currently debating a review of those partnership roles, with China eager to see Taiwan lose any recognition.
Following his private complaints to Palau and PIF, and his public comments, Mr Qian said he would next take his umbrage to the dialogue partner meetings on Tuesday.
The incident was the obvious talking point from the ceremony, where Mr Whipps urged nations to maintain a focus on climate.
"Climate change remains the single greatest threat to the security and the well-being of Pacific peoples," he said.
The 55th PIF leaders meeting has also been notable for a lengthy list of no-shows.
Leaders from Fiji, Kiribati, New Caledonia, Samoa, Solomon Islands and Vanuatu are not attending for a range of reasons, with Kiribati not sending political representation at all.
