(author) I thought AS worked pretty well. The syntax is a little idiosyncratic but it "just worked" once I learned its pet peeves, and it seems to have specific support for the added 9995 instructions.
Lots of resources on the original TI dev boards and tools for TMS99Xx.
Thank you, that’s a great site. There goes my Sunday morning!
I used AS to write the program, and it is my "reference assembler" for the one I am writing. I just wanted to see if I could write a working retro assembler.