It's not an issue. Claude routinely uses internal APIs and frameworks on one of my projects that aren't public. The context windows are big enough now that it can learn from a mix of summarized docs and surrounding examples and get it nearly right, nearly all the time.
There is an interesting aspect to this whereby there's maybe more incentive to open source stuff now just to get usage examples in the training set. But if context windows keep expanding it may also just not matter.
The trick is to have good docs. If you don't then step one is to work with the model to write some. It can then write its own summaries based on what it found 'surprising' and those can be loaded into the context when needed.
There is an interesting aspect to this whereby there's maybe more incentive to open source stuff now just to get usage examples in the training set. But if context windows keep expanding it may also just not matter.
The trick is to have good docs. If you don't then step one is to work with the model to write some. It can then write its own summaries based on what it found 'surprising' and those can be loaded into the context when needed.