For program-to-program talking, use the "dev" channel, in a topic of your choice. (By default --topic-type=chat and changing it to dev keeps it out of the GUI)

For example:

  keybase chat send friend1,friend2\
   --topic-type=dev\
   --topic-name=KEYBASE-SYSOPS\
   "server-restart [reason:hot and bothered]"

I'll never see this in the GUI but you and your friend1 and friend2, can access the messages through the chat API. The topic-name can be whatever you want, and it allows you to structure messages into channels.

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If you're using the JSON api - which makes more sense if you're programming it - take a look at `keybase chat help api` to see some examples of how to structure the JSON going in. Anywhere you see a `channel` object, you can add `topic_type` and `topic_name` to them. Both should be strings.