Dreaming in smoke - Tricia Sullivan

Kalypso Deed is a shotgun, riding the interface between the AI Ganesh
and human scientists who solve problems through cyberassisted Dreams.
But she's young and a little careless; she'd rather mix drinks and play
jazz. Azamat Marcsson is a colorless statistician: middle-aged, boring,
and obsessed with microorganisms. A first-class nonentity - until one of
his Dreams implodes, taking Kalypso with it.

Now Ganesh is crashing, and nothing could be worse. For on the planet
T'nane, it is the AI alone that keeps the colonists alive, eking out a
grim existence in an environment inimical to human life. To save the
colony, Kalypso must persuade Marcsson to finish the Dream that is
destroying Ganesh. But Marcsson has gone mad, and T'nane itself has
plans for them both that will alter their minds-and their world - forever.