First 2026 release

[mdekstrand]

I'm pleased to announce the first 2026 release, 2026.1.0! This mostly follows in the changes of the 2025 release series, with a few cleanups of old or deprecated APIs and an improvement to the training interface.

Users implementing their own components should pay attention to the Trainable changes, although components implementing UsesTrainer are unchanged. The old IterativeTraining interface is gone in favor of UsesTrainer.

The metric interfaces are also simplified; this will mostly affect users implementing their own metrics. The metric aggregation support is overhauled, which will affect all users; RunAnalysis still exists, but is deprecated, in favor of MeasurementCollector.

See the release notes and documentation for full details: https://lenskit.github.io/lenskit-docs/stable/releases/2026.html

As always, feedback is very welcome in the form of discussions, bug reports, pull requests, or even e-mails.

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This discussion was created from the release First 2026 release.