The traditional narrative with Konishi Yukinaga's diplomatic career during the middle portion of the Imjin War is that he lied to Hideyoshi about what the Ming court was asking of him, and conspired to make it appear to both sides as if there was a surrender and concession, when in reality no such thing had been said. However, I've been hearing a new narrative now that, for the most part, Hideyoshi was in fact aware of what was going on. If that was the case though, then why did he become so angry at Konishi Yukinaga when negotiations failed that the other bugyo had to intercede on his behalf?
It seems like there's many versions of what exactly he did during the diplomatic part of the war, and I'm not sure if it's due to various theories or simply outdated scholarship not being pushed back against enough.
Hideyoshi was angry because Konishi Yukinaga didn't tell him the emperor didn't agree to let him have the 4 provinces of Joseon. Had Konishi told him about this, then nothing would have happened. However, Konishi didn't want the negotiation to collapse, so he hid this fact from Hideyoshi. They continued with the investiture ceremony without Hideyoshi knowing this.
After the investiture was successful, Hideyoshi was in good mood. He then sent 2 monks to entertain the envoy and told them to "ask whatever they want". The Ming envoys asked Hideyoshi when he would return the land to Joseon and withdraw. Hideyoshi was upset. He then got angry. During his meeting with Terazawa Hirotaka, apparently, he said, "You should have told me from the beginning! Why didn't you tell me?!". This indicates he wasn't angry about the content of the negotiation. He was angry that Konishi failed to disclose some information.
After this, the envoys were expelled, but the reason was that Joseon was disrespectful and didn't send a prince. Hideyoshi didn't want to have another war with Ming, so he blamed Joseon. He hoped Ming wouldn't get involved since he was now Ming's vassal.
Memory is a little blurry, but as far as I know, the first official negotiation held at Nagoya Castle in Japan was conducted through written communication between Ming (fake) envoys and Genso Keitetsu, with Hideyoshi himself being physically present. Konishi Yukinaga wasn't even part of the negotiation.
However, during the negotiation, Hideyoshi gave a list of seven maximalist demands from a position of strength, so he was likely misled about the actual situation in Korea, possibly due to an earlier, unofficial negotiation between Shen Weijing and a bunch of Japanese commanders at Yangsan warehouse. The report from this negotiation gave Hideyoshi the impression that Ming had come to beg for peace, even though it was the Japanese commanders that initiated the peace negotiation in the first place.
Konishi was part of this one, but he was not the only Japanese commanders involved. He did however suggest to the Ming side about the "beg for peace" part (which Shen agreed, although he probably spun the details into a more palpable forms when he report back to his superior), so he wasn't actually deceiving Hideyoshi either.