All of the current Google and LLM answers to this talk about things like setting Reline.autocompletion = false and IRB.conf[:USE_AUTOCOMPLETE] = false. These will indeed work to disable autocomplete....after IRB has been started. But across many experiments I tried, there was no point during the Rails initialization process where I could add these instructions without them getting overridden by the time my cursor took control.

This issue was exacerbated by my IRB being unwilling to read from the local .irbrc in the project directory. There are probably ways to force this to be read, but I suspect that the point at which a local .irbrc file would be loaded might still be prior to the IRB initializer that wants to set USE_AUTOCOMPLETE to true.

The one/only way I could get IRB to be started without autocomplete enabled was by adding to the initialization process:

I'm sure there are more elegant ways, but this is an effective way to ensure that autocomplete will be initially disabled in both local development environments as well as staging and production IRB consoles.