In yet another sign that the drive to close the Rikers jail complex has moved far beyond the realm of reason, Mayor Bill de Blasio and the City Council have agreed to ensure no jail gets built on the island again, ever.

Not exactly a vote of confidence that New York City will be satisfied with what it’s to get instead of Rikers, is it?

This, when the actual replace-Rikers plan is still a work in progress, with another council vote set for Thursday to advance the construction/expansion of four jails across four boroughs so that Rikers can close.

And when most of the targeted neighborhoods vehemently don’t welcome them.

For that matter, the mayor must contend with a growing “no new jails” movement that argues the city should “divest from prisons and police” so it can spend the savings on free housing, education and so on.

Impractical, but then again de Blasio’s own vision requires the city to get the total jail population down to 4,600 — and will leave it no room to detain much more than that number, should it find it needs to during some future crime wave.

Then again, the mayor won’t commit to closing the Rikers jail before 2026, and he’s out of office come Jan. 1, 2022.

So the city still has time to consider alternatives, like the rebuild-at-Rikers alternative drawn up by the architectural firm of William Bialosky and Partners. (It was hired by a group that’s resisting the drive for the skyscraper jail in Chinatown.)

Bialosky points out that the Rikers lot offers something pretty valuable for building a truly humane jail: space. Why pack detainees into high-rise buildings when you can use existing ones for a more diffused, campus-like environment incorporating better access to daylight and greenery? The 45-page prospectus even calls for plots where inmates can grow crops.

The idea’s at least worth keeping in mind if the city’s leaders ever stop treating the evil of Rikers as a religious dogma and start asking what really makes sense.