Sourced from whest-starterkit @ aaa3882.

Stage 2: Validate the Contract

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Stage 1 confirms your estimator runs and converges. Stage 2 confirms it satisfies the harness contract — right shapes, right types, finite values, optional lifecycle hooks behave.

🚀 Run it

uv run whest validate --estimator estimator.py

A passing run renders a Rich panel with four green OK rows:

╭─ Validation ─╮
│ Status: success
│ ┏━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━┓
│ ┃ Status ┃ Check                    ┃ Detail     ┃
│ ┡━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━┩
│ │ OK     │ class resolved           │ Estimator  │
│ │ OK     │ setup(context) completed │ ok         │
│ │ OK     │ predict() returned shape │ (2, 4)     │
│ │ OK     │ values finite            │ all finite │
│ └────────┴──────────────────────────┴────────────┘
╰──────────────╯

What each check does

• class resolved — the loader found class Estimator(BaseEstimator) in your file (override with --class CustomName).
• setup(context: SetupContext) — if you defined setup() (it's optional), the validator calls it with a probe SetupContext and confirms it returns without raising. See SetupContext fields.
• predict() returned shape — invoked on a probe MLP (width=4, depth=2 by default) and asserts the returned array has shape (mlp.depth, mlp.width).
• values finite — no NaN or Inf in the returned array.

A failing run halts at the first failed check and prints a structured error pointing at the contract clause that broke. See estimator-contract.md for the full contract.

✅ Expected outcome

Validate is a 2-second sanity check against a probe MLP — it doesn't score your estimator, only that it returns the right shape of the right type with finite values. Most participants pass on the first try.

If a check fails, the panel prints the broken clause inline. For shape mismatches, the error includes expected_shape and got_shape so you can fix the bug without reading source.

✅ When you're ready

Move on to Stage 3: run the harness locally.