The levels 5, 6, 7 and 8 of lichess artificial intelligence just received a consequent boost. The max search depth has been increased, and stockfish transposition table is now put in use. Levels 1 to 4 have not been changed.
Also, the analysis should benefit from the transposition table and give more accurate results.
Kudos to tsinnema for the investigation of stockfish source code, and precious advices about lichess integration.