Configs

prime-rl uses pydantic-config — a Pydantic-based TOML + CLI config system (no tyro). Every entrypoint accepts TOML files via @ and CLI overrides.

Loading and composition

uv run rl @ examples/basic/reverse-text/rl.toml                                  # single TOML
uv run rl @ examples/basic/reverse-text/rl.toml --max-steps 50                   # CLI override
uv run rl @ base.toml @ overlay.toml                                       # left-to-right merge
uv run rl --model @ model.toml --data @ data.toml                          # nested section files
uv run rl @ base.toml --trainer @ trainer.toml --trainer.lr 1e-3           # mixed

Resolution order: CLI > config files (left-to-right) > class defaults. Merging is deep — unset fields in an overlay are preserved from the base. output_dir has one extra fallback: CLI > config files > $PRL_OUTPUT_DIR > "outputs".

Naming: CLI uses kebab-case (--vllm.max-model-len); TOML uses snake_case (max_model_len).

Inspect & validate