The glean index scip command appears to only ever use defaults, and not accept any additional arguments:

https://github.com/facebookincubator/Glean/blob/main/glean/lang/scip/indexer/Glean/Indexer/SCIP.hs

When poking around, I also found this entrypoint:

https://github.com/facebookincubator/Glean/blob/main/glean/lang/scip/indexer/Glean/Indexer/SCIP/Main.hs

Which appears to have the behavior that is more expected. Before I open a PR, should the latter be used instead?

The consequence of this is that when indexing scip files, the language is always unknown, which renders glean/glass less than useful. Once I updated this manually, I was able to get glass working well.