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# System Behavior: Training

> Living document. Updated by `/archive-spec` when features are completed.
> Last archived: F010 on 2026-03-28

---

## Training Pipeline

### Training notebook produces a trained model from one-click execution
<!-- since: F006 | test: tests/training/test_config.py::test_grpo_config_defaults -->

The system accepts a `notebooks/train_grpo.ipynb` notebook that, when run end-to-end, downloads a HuggingFace model, trains it on SQLEnv episodes using GRPO, and saves the trained weights to a configurable output directory.

### Training produces a learning curve showing reward improvement
<!-- since: F006 -->

After training completes, the notebook displays a matplotlib plot of reward over training steps, showing whether the model learned to improve its SQL exploration strategy over the course of training.

### Training produces side-by-side episode transcripts
<!-- since: F006 -->

After training completes, the notebook displays episode transcripts comparing random-action baseline episodes against trained-model episodes on the same questions, showing the difference in exploration behavior.

### Rollout function plays SQLEnv episodes via model generation
<!-- since: F006 | test: tests/training/test_rollout.py::test_rollout_func -->

The system accepts a batch of question prompts and returns episode completions by playing full SQLEnv episodes: resetting the environment, generating actions with HF model.generate(), parsing them into SQLActions, and stepping the environment until the episode ends.

### Reward functions return per-completion scores for GRPO training
<!-- since: F006 | test: tests/training/test_rewards.py::test_reward_correctness -->

The system accepts TRL-format completion batches and returns float reward lists from three independent callables: correctness (binary 0/1), progress (normalized cumulative progress), and operational (sum of per-step L1 signals).

### Unparseable model output falls back to QUERY action
<!-- since: F006 | test: tests/training/test_rollout.py::test_parse_model_output_fallback -->

When the model produces text that cannot be parsed as `ACTION_TYPE: argument` format, the system defaults to a QUERY action with the raw text as the argument, allowing the episode to continue rather than crashing.

### TRL environment_factory integration
<!-- since: F010 | test: tests/unit/test_trl_adapter.py::test_configure_and_instantiate -->

The training system accepts a TRL-compatible environment class (`SQLEnvTRL`) as `environment_factory` for `GRPOTrainer`. TRL auto-discovers `describe`, `sample`, `query`, and `answer` as callable tools via typed docstrings and runs generation/tool-calling/multi-turn control flow without custom rollout glue.

### Class-level environment configuration for no-arg factory construction
<!-- since: F010 | test: tests/unit/test_trl_adapter.py::test_configure_sets_class_attrs -->

The adapter accepts environment configuration (`questions_path`, `db_dir`, `step_budget`) through a `configure()` classmethod before trainer construction, satisfying TRL's no-argument `environment_factory` instantiation contract.

### Environment reward accumulation via callback
<!-- since: F010 | test: tests/unit/test_trl_adapter.py::test_reward_accumulation -->

Each adapter instance accumulates per-step reward during an episode, and a module-level reward callback reads those values and returns `list[float]` in environment order for TRL reward ingestion.

### Episode state isolation across resets and concurrent instances
<!-- since: F010 | test: tests/unit/test_trl_adapter.py::test_reset_clears_state -->

Each environment instance owns independent mutable episode state. Calling `reset()` clears reward and done flags for a fresh episode, preventing cross-episode leakage and avoiding cross-instance state sharing.

### build_trainer accepts environment_factory
<!-- since: F010 | previously: F006 | test: tests/unit/test_trl_adapter.py::test_build_trainer_environment_factory -->

**Before:** `build_trainer` accepted a rollout-function path and passed custom rollout glue into trainer construction.
**After:** `build_trainer` accepts `environment_factory` and forwards the environment class directly to `GRPOTrainer`, with optional `configure()` pre-wiring from notebook config values.

The legacy rollout module remains in the repository for compatibility/reference but is no longer the training pipeline's default orchestration path.