# Should ParaView combine temporal VTKHDF files into one time series?

**URL:** <https://discourse.vtk.org/t/should-paraview-combine-temporal-vtkhdf-files-into-one-time-series/16615>\
**Category:** Development\
**Tags:** file-formats\
**Created:** [November 12, 2026, 7:08pm UTC](https://discourse.vtk.org/t/should-paraview-combine-temporal-vtkhdf-files-into-one-time-series/16615 "2026-11-12T19:08:30Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![nncarlson](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/n/ed655f/32.png) [@nncarlson](https://discourse.vtk.org/u/nncarlson)\
**Post date:** [November 12, 2026, 7:08pm UTC](https://discourse.vtk.org/t/should-paraview-combine-temporal-vtkhdf-files-into-one-time-series/16615/1 "2026-11-12T19:08:30Z")

</div>

I have two VTKHDF files representing successive simulation runs across a restart. The first contains four time steps and the second contains two later, nonoverlapping time steps. Each file reads correctly individually.

In ParaView 6.2.0, opening them together using:

reader = OpenDataFile([“first.vtkhdf”, “restart.vtkhdf”])  
reader.UseCache = 0  
reader.UpdatePipelineInformation()  
print(list(reader.TimestepValues))

produces four entries—the second file’s two times followed by two zeros—instead of the expected six. This occurs with both RectilinearGrid and StructuredGrid.

Is this combination intended to work through vtkFileSeriesReader? Its documentation suggests that internal time lists should be combined. If so, does this look like a bug, and is it known or fixed in a newer release?

A series of static VTKHDF snapshots works correctly in the same installation.