Lightning-AI/pytorch-lightning 2.6.4

Lightning 2.6.4

Repository: Lightning-AI/pytorch-lightning

Tag: 2.6.4

Published: 2026-05-20T22:08:42Z

Prerelease: no

Release notes:

Changes in 2.6.4

PyTorch Lightning

Removed

• Removed support for Neptune logger (#21572).

>*Note*: We usually don't remove features in a patch release, however in this case it's an exception since even without removing it the integration would be broken due to Neptune being acquired and sunsetting public service

Changed

• Raised minimum LitLogger version to 2026-03-17 (#21591)

Fixed

• Fixed val_check_interval raising ValueError when limit_val_batches=0 and interval exceeds training batches (#21560)
• Fixed FSDP mixed precision (bf16-mixed, 16-mixed) initializing model parameters in half precision instead of fp32 (#21586)
• Fixed device_mesh type hint in FSDPStrategy to accept a 2-element tuple via the CLI (#21581)
• Fixed RichModelSummary model size display formatting (#21467)
• Fixed floating-point precision in SimpleProfiler duration aggregation by using math.fsum (#21525)

Lightning Fabric

Fixed

• Fixed FSDP mixed precision (bf16-mixed, 16-mixed) initializing model parameters in half precision instead of fp32 (#21586)
• Fixed device_mesh type hint in FSDPStrategy to accept a 2-element tuple via the CLI (#21581)

Full commit list: 2.6.1 -> 2.6.4

Contributors

New Contributors

• @AsherJingkongChen made their first contribution in https://github.com/Lightning-AI/pytorch-lightning/pull/21467
• @ManasVardhan made their first contribution in https://github.com/Lightning-AI/pytorch-lightning/pull/21560

We thank all folks who submitted issues, features, fixes and doc changes. It's the only way we can collectively make Lightning :zap: better for everyone, nice job!

In particular, we would like to thank the authors and co-authors of the pull-requests above:

@AsherJingkongChen, @Borda, @bhimrazy, @deependujha, @justusschock, @littlebullGit, @ManasVardhan, @taha-yassine