app.backend.constants

Backend-only environment configuration.

Reads HF_TOKEN (HF Inference API + claim decomposition) and HF_CACHE_DIR (mounted HF cache for ModernBERT-NLI) from the process environment, with a .env fallback for local development. HF_FALLBACK_MODEL is the model used both as the generation fallback when Hydra is unavailable and as the LLM that performs atomic claim decomposition in app.backend.claim_splitter.

Lives here rather than under olmo_tap so the research package has no dependency on FastAPI / HF API plumbing.