[octo_t]

the text format changes, the API stays relatively static (afaik). Most tools use something similar to:

  LLVMContext &Context = getGlobalContext();
  SMDiagnostic Err;
  Module *Mod = ParseIRFile(argv[1], Err, Context);

[jevinskie]

The C API is deemed stable. The C++ API changes every release. The textual IR has so far been forwards compatible. Bit code is also supposed to be forwards compatible but some bugs have prevented this in the past. Backwards compatibility is right out which can be frustrating.