Why was there no military use of chemical weapons by the Nazis?

I’m aware that Hitler had an understandable personal aversion to the stuff (sadly limited to soldiers), and that the Nazis presumed the Allies to have formulations as nasty as Sarin (when we didn’t, pace Op Vegetarian), and that the battlefield utility of chemical weapons is often less than their theoretical lethality would suggest...

But, I just can’t get my head around the fact that, in 1945, chemical weapons were not deployed against military targets by the Nazi Germans.

This was no ‘regular’ war fought over contested territory or what have you - the Nazis wished to wipe out the Jews and the Slavs, and were not all that fond of the Western Allies, who had been turning their cities into charnel for years.

Many (including Hitler) had assumed a Wagnerian, ‘end of days’ mentality, where they were happy to see their nation in ruins and fight on, because there could be no ‘post-war’. Children and the elderly were being sent to the front. Hitler even ordered the bombing of German infrastructure, though ‘cooler heads prevailed’.

They’d clearly lost the war, but had done so at a point at which they still maintained an integrity of command and a certain freedom of action: i.e, if given the order, the chemical weapons would surely have been able to be used?

A particularly convincing point is that use could have been restricted to the ‘barbarian’ Soviets (who they already planned to murder en masse c.f. Generalplan Ost), in order to buy time for the Western Allies to capture as much of Germany as possible.

Whilst this may not be the best form of historical analysis... if the Second World War were a fictional story, would it be believable for the regime which had morphed into a bottomless pit of evil (having not started out all that nice), aware of its facing utter defeat, not have used the one weapon (at least against their most hated enemy, who they viewed as subhuman) which could stall the relentless advance of their foes?

To top it all off, they’d been using chemical weapons against the Jews etc. for years. You can only be hanged once...

There will be good reasons I’m sure, and I’ll be very grateful for them being revealed to me, because what happened just doesn’t seem very plausible.