From just a short skimming of the docs:

- my biggest issue with concurrency in python (especially with asyncio) is leaking tasks. Pyper should provide structured concurrency support a-la trio.

- I don't see the opposite of branch to collect the output of multiple sub pipelines into a single stage. I need this pretty much always and it is a chore to implement.

- Async need not force the full pipeline to be async. There should be an option to run async funcitons in background event loops. Especially as you already support threaded executions.

Your third point intrigues me a lot. I imagine for the majority of cases, it's generally more useful to work with async functions in the structure of async syntax, but I suppose it's possible to run async functions in a synchronous pipeline.

Even though there's currently no built-in support for this, a workaround could be to just define synchronous helper functions to handle running your async logic in an event loop.

asyncio.TaskGroup from stdlib provides structured concurrency