Possible Tech Exploit that AI can't handle
When you set up a game where AI are in teams and the following settings are enabled in scientific, the AI can be crippled for a fairly long time or the whole game as far as technology acquisition. In the game I ran, the AI was configured to cheating difficulty. After playing over 100 turns on a 100k tile map with, 10 teams of 3 AI each, none of the AI I had contact with were able to retain any of the techs for longer than a turn or 2 (not even the first stage).
0. Team members have own tech tree
1. There is Research Point Penalty when receiving tech for free (in the game I played, this was 25% of the tech cost was deducted)
2. Tech Loss when below a specified threshold (a 25% negative balance in the specific game)
3. Chance for tech loss when gifting (or stealing via diplomat/spy) and receiving technology via treaty (25%/50% respectively)
4. Tech point recovery when tech is lost (50% in the game I played)
5. Tech cost Initial ratio x3 (setting that determines base cost for a tech that is factored with the ruleset)
Ruleset Used: Freeciv23 (the ruleset using 2 combat's system and 3's terrain properties, the readme for the ruleset says the AI was adapted to play well in those rules)
The AI's first instinct when it acquires a new tech is to help a fellow teammate also get the tech but the tech loss ratio would end up causing both the donor and recipient to risk losing the tech, and even when it wasn't lost due to treaty, the insufficient science output made it challenging for even large AI empires (one AI had the same score as me, but generally was using warriors 100 turns into the game. Since tech penalty and tech loss isn't commonly seen in games, this is relatively low priority, but the suggestion is to have the AI check for tech loss risk before making a decision to exchange/trade or steal, though none of the AI in the game I ran for 120 turns ever got to diplomat.
Also, it should be noted that its possible under these settings to exploit the AI to always give its resources for tech it can't maintain with these settings every turn. I did a test where the AI I as a player had an alliance with (not part of a team). It had 1k gold and by continuously trading tech that it would lose, I drained its gold income to less than 100 in 2 turns by giving away the safe (no risk of loss to me as a player) in exchange for the gold. Such settings make it possible to take away cities and other key resources to cripple or destroy a nation.