Since no one else has answered this I, a lowly developer IC, will give it a shot.
Start by writing up a detailed employee handbook and code of conduct. Have a conversation with new reports about how these inevitably jargon-laden documents translate to expectations in human terms. You don't need to use the word "toxic", but talk about assuming good intent, communicating respectfully and clearly with others, and sharing credit and responsibility with teammates.
Create a sense that serious feedback about teammates' behavior given to you, the manager, about teammates' behavior will be taken seriously and kept confidential. Do this by handling the smaller stuff competently.
Give feedback to employees who are creating bad team dynamics early and often. Allow them opportunities to reflect and improve. Emphasize if necessary that their behavior is not just problematic at an interpersonal level, but it's (presumably) disrupting the company at a business level as well.
Work with HR to keep a paper trail and document conversations so that when the time comes to fire an employee who is irredeemably "toxic", there is a rich timeline of unpleasant behavior, feedback and warnings, and a failure to sufficiently improve over time. Ideally only someone with their head all the way up their ass wouldn't see how the patterns of behavior relate to documented expectations and to termination, but unfortunately that's who you're dealing with.
I suppose all of this only works to immunize against "toxicity" in a work environment that isn't already toxic.
I think these are very good ideas, actually I don't recall to have seen an employee handbook that states expectations explicitly, even while working for very big firms.
Well, at IBM they probably have something like that, I may be wrong about that.
Start by writing up a detailed employee handbook and code of conduct. Have a conversation with new reports about how these inevitably jargon-laden documents translate to expectations in human terms. You don't need to use the word "toxic", but talk about assuming good intent, communicating respectfully and clearly with others, and sharing credit and responsibility with teammates.
Create a sense that serious feedback about teammates' behavior given to you, the manager, about teammates' behavior will be taken seriously and kept confidential. Do this by handling the smaller stuff competently.
Give feedback to employees who are creating bad team dynamics early and often. Allow them opportunities to reflect and improve. Emphasize if necessary that their behavior is not just problematic at an interpersonal level, but it's (presumably) disrupting the company at a business level as well.
Work with HR to keep a paper trail and document conversations so that when the time comes to fire an employee who is irredeemably "toxic", there is a rich timeline of unpleasant behavior, feedback and warnings, and a failure to sufficiently improve over time. Ideally only someone with their head all the way up their ass wouldn't see how the patterns of behavior relate to documented expectations and to termination, but unfortunately that's who you're dealing with.
I suppose all of this only works to immunize against "toxicity" in a work environment that isn't already toxic.