Issues

• isin on object-dtype columns coerces to strings: isin(['1']) matches the integer 1 (pandas does not), isin([1]) misses it

  needs triage
  dask/dask#12612 · Filter by author ptimizeroracle opened on Sep 28, 2026

• dask.array.linalg.lstsq raises LinAlgError on rank-deficient input (numpy returns minimum-norm solution)

  needs triage
  dask/dask#12610 · Filter by author francisco-dlp opened on Sep 27, 2026

• set_index splits duplicate index values across partitions when a list column is present and repartition(partition_size=...) precedes it (regression 2025.3.0 → 2025.4.1)

  needs triage
  dask/dask#12604 · Filter by author guozhans opened on Sep 23, 2026

• dask.array.reductions.nanquantile never dispatches float32 input to numbagg, forcing a much slower fallback

  needs triage
  dask/dask#12601 · Filter by author benritchie opened on Sep 17, 2026

• Index join with MultiIndex columns fails on the shuffle path: "columns overlap but no suffix specified: MultiIndex([('_partitions', '')])"

  needs triage
  dask/dask#12599 · Filter by author fbunt opened on Sep 16, 2026

• __version__ resolves to "unknown" when installed via conda due to missing __commit_id__ in _version.py

  needs triage
  dask/dask#12591 · Filter by author DeBoni03 opened on Sep 9, 2026

• da.from_zarr does not use shards (da.from_array does)

  needs triage
  dask/dask#12586 · Filter by author joshua-gould opened on Sep 8, 2026
  1

• da.to_zarr writes corrupt data when specifying chunks or shards

  needs triage
  dask/dask#12583 · Filter by author joshua-gould opened on Sep 4, 2026

• Support irregular array chunks using zarr

  needs attentionneeds triage
  dask/dask#12581 · Filter by author joshua-gould opened on Sep 1, 2026

• set_index on read_parquet(dtype_backend="pyarrow") raises TypeError: data type '...' not understood for nested Arrow dtypes

  needs attentionneeds triage
  dask/dask#12580 · Filter by author guozhans opened on Sep 1, 2026

• set_index(..., npartitions=...) can leave inconsistent divisions metadata

  needs attentionneeds triage
  dask/dask#12565 · Filter by author ramonruiz97 opened on Aug 19, 2026

• Dask left merge carries over wrong index values in the presence of empty partitions

  needs attentionneeds triage
  dask/dask#12564 · Filter by author albarji opened on Aug 19, 2026
  1

• Assigning a DataFrame column with dd.to_datetime() changes dtypes of unrelated columns

  needs attentionneeds triage
  dask/dask#12556 · Filter by author andrewrli opened on Aug 15, 2026

• Dask optimization of [merge_asof + drop] graphs removes columns prematurely

  needs attentionneeds triage
  dask/dask#12544 · Filter by author albarji opened on Aug 7, 2026
  1

• Unable to save dask dataframe containing list column with pandas==3

  needs attentionneeds triage
  dask/dask#12543 · Filter by author joshua-gould opened on Aug 6, 2026
  1

• Autochunking fails with zero length dimensions

  needs attentionneeds triage
  dask/dask#12537 · Filter by author charles-turner-1 opened on Aug 1, 2026

• Implicit re-exports in __init__.py

  needs attentionneeds triage
  dask/dask#12526 · Filter by author JeppeKlitgaard opened on Jul 28, 2026

• dask.visualize shows unfused graphs, but scheduler runs fused graph

  needs triage
  dask/dask#12517 · Filter by author maneesh29s opened on Jul 22, 2026
  1

• dask-expr bug: dd.drop([], axis=1) raises ValueError

  needs attentionneeds triage
  dask/dask#12510 · Filter by author jtilly opened on Jul 20, 2026

• Optimized graph size depends on PYTHONHASHSEED (up to 30x task-count blowup)

  needs attentionneeds triage
  dask/dask#12507 · Filter by author bertcoerver opened on Jul 16, 2026

• persist() on a root read_parquet with column projection returns a corrupt collection; any later compute fails with "lost dependencies"

  needs attentionneeds triage
  dask/dask#12488 · Filter by author Dimitri-Schnider opened on Jul 4, 2026
  1

• Dask to_zarr warns and rechunks on existing array template

  needs triage
  dask/dask#12458 · Filter by author Jaapel opened on Jun 12, 2026

• clone() corrupts graphs containing Task/GraphNode values, breaking task-spec fusion

  needs triage
  dask/dask#12455 · Filter by author JSKenyon opened on Jun 11, 2026

• Severe repartition slowdown for wide PyArrow-string DataFrames with unknown divisions

  needs triage
  dask/dask#12449 · Filter by author albarji opened on Jun 8, 2026
  1

• ⚠️ Upstream CI failed ⚠️

  upstream
  dask/dask#12446 · Filter by author github-actions opened on Jun 5, 2026