v0.4.0 - Next-Open Execution Ledger & Data-Quality Fixes

Highlights

• New opt-in simulate_next_open and NextOpenResult: an explicit position ledger with opening fills, actual unit drift, publication ordering and observation masks.
• Self-financing costs on risky buys and sells, cash accounting, and a benchmark using the same ledger conventions.
• Optional initial-equity baselines for drawdown and Calmar, including inception losses in the new ledger without changing legacy metric defaults.

Fixes And Compatibility

• HMM convergence metadata now describes the selected highest-likelihood restart. Model selection and fitted parameters are unchanged.
• The legacy overlay rejects missing, nonfinite or nonpositive prices needed for an exposed return or benchmark. Valid-input golden outputs are preserved.
• Warning migration: replace non_session_asof with asof_not_in_panel. Absence from a supplied panel does not prove market closure; is_stale=False does not by itself establish exchange-calendar freshness.
• The legacy close-only API and pipeline defaults remain unchanged. Next-open execution is opt-in and requires caller-supplied, consistently adjusted prices and an exchange schedule.

See the execution contract and changelog for assumptions and migration details.

Validation

• 184 offline tests passed against an installed package, with tests run outside the checkout.
• Final release preparation changes documentation only; no functional code changes follow that validation.
• Ruff, formatting and strict MyPy checks pass.
• Wheel and source-distribution installation, dependency checks, module imports and both CLI entry points are verified on Windows / Python 3.12.4, without the optional Textual extra.

Distribution

This release includes the wheel, source distribution and SHA256 checksums. GitHub and PyPI publication are separate; PyPI upload is handled by the maintainer.

To install a downloaded wheel:

python -m pip install ./regimelab-0.4.0-py3-none-any.whl