[REDACTED]

[Ashtagon]

Improved Cohort is a feat that gives +1 Leadership and increases your Cohorts level by one, while also increasing its max level to one level lower then you. This gives you a max 18th level cohort pre-epic and allows it to progress just as if your character died and had been ressurrected... one level behind the party.

ok, so with that feat, your cohort's maximum level becomes 18. The Leadership table goes pretty high, and the final entry is "25+ Leadership", which notes a maximum cohort level of 17, or 18 with that feat.