Version: 0.80.3856
Savegame: http://www.aprogas.net/~aprogas/tmp/Diplomatic%20Victory.zip
Short description: under certain conditions accepting a pact gives a great amount of diplomatic points
Long description:
The game is on a Random Large (Single) map with 8 players (7 unfair random AI), with Diplomatic Victory and Allied Victory enabled and other victory conditions disabled. I play TEC Loyalists (green) and have become friendly with an Advent Rebel neighbour (Psi Order Zealots, red) and am also building diplomatic relations with some other factions. I have researched all pacts and offered them to Psi Order Zealots, they have previously offered me a Research and Antimatter Pact and I accepted those without problems. They now offer a Culture Pact and if I accept it, my diplomatic points jump from 34.28 to 1534.68 and I win a diplomatic victory (they jump from 38.86 to 1539.22). The rate of both me and them jumps from 0.01120 to 50.01120. If I choose to continue playing instead of quitting, they revoke all treaties (as players usually do when continuing after a victory) and I cannot test how diplomatic points behave after the victory.
I continued playing this game without accepting the Culture Pact and later I am offered a Mass Pact; the same issue occurs with the Mass Pact with my points jumping from 41.60 to 1542.06 and Psi Order Zealot's points from 45.47 to 1545.84.
As a minor side-issue, I noticed the production reports contain the following messages: Psi Order Zealots has won a Diplomatic Victory, Psi Order Zealots is close to winning an Occupation Victory, You have won a Diplomatic Victory, You are close to winning an Occupation Victory. In other words, it says Occupation Victory where it should say Diplomatic Victory.
How to reproduce:
Open the linked savegame, in the diplomatic screen, go to Psi Order Zealots (red) and accept the Culture Pact.