DSPy 3.4.0b1 moves LM execution to a native engine interface with local code interpreter

DSPy shipped the first beta of 3.4, relocating language-model execution to a shared lm15 engine interface with engine='auto' falling back to LiteLLM before execution, adding a local CPython interpreter for trusted code and async execution in ReActV2, plus custom Flex code proposals in GEPA. The team frames 3.4 as the LM transition release and 3.5 as the migration deadline for the experimental 3.3 LM types.