Pin pandas to exclude 3.0.4 (segfault constructing pd.Timedelta on Python 3.14)

[galipremsagar]

Description

pandas 3.0.4 (released 2026-06-28) segfaults when constructing any pd.Timedelta on Python 3.14, which crashes import cudf at module-load time (the DatetimeIndex class body in python/cudf/cudf/core/index.py builds a set of pd.Timedelta constants). This breaks all of cudf / cudf.pandas and the pandas-tests CI job (pytest segfaults during collection, before any test runs).

Minimal reproducer — pristine venv with only pandas==3.0.4 + numpy on CPython 3.14, no cudf involved:

import pandas as pd
pd.Timedelta(days=28)   # Fatal Python error: Segmentation fault

It is a regression from pandas 3.0.3 (works) — pandas is the only changed package — and reproduces with numpy 2.3.3 (pandas 3.0.4's own declared minimum for py3.14) and 2.4.6. The faulthandler C stack shows unbounded recursion between pandas/_libs/tslibs/timedeltas and numpy's _multiarray_umath.

Filed upstream: pandas-dev/pandas#66086

This PR pins pandas != 3.0.4 in the runtime dependency (run_common in dependencies.yaml, regenerated into the wheel/conda metadata). The exclusion form (rather than <3.0.4) lets a fixed pandas (e.g. 3.0.5) be picked up automatically; the pin should be removed once that ships.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 5646b5f and 5fe2b2e.

📒 Files selected for processing (9)

• conda/environments/all_cuda-129_arch-aarch64.yaml
• conda/environments/all_cuda-129_arch-x86_64.yaml
• conda/environments/all_cuda-133_arch-aarch64.yaml
• conda/environments/all_cuda-133_arch-x86_64.yaml
• dependencies.yaml
• python/cudf/pyproject.toml
• python/cudf_polars/pyproject.toml
• python/dask_cudf/pyproject.toml
• python/pylibcudf/pyproject.toml

🚧 Files skipped from review as they are similar to previous changes (2)

• python/cudf/pyproject.toml
• python/pylibcudf/pyproject.toml

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📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes
  • Excluded the problematic pandas==3.0.4 by tightening pandas upper bounds across supported conda environments and Python package configurations.
  • Updated shared pandas constraints and related test/extras pins to keep pandas 3.0.x working while avoiding the 3.0.4 release.
  • Refined “oldest” and compatibility test matrices so they won’t select pandas==3.0.4 (temporary cap noted in the dependency configs).

Walkthrough

Narrows pandas version constraints in dependencies.yaml, several pyproject.toml files, and four conda environment YAML files to exclude versions at or above 3.0.4a0. Updates one dask_cudf copyright line.

Changes

Pandas 3.0.4 exclusion

Layer / File(s)	Summary
Canonical pin and pyproject.toml updates dependencies.yaml, python/cudf/pyproject.toml, python/dask_cudf/pyproject.toml, python/pylibcudf/pyproject.toml, python/cudf_polars/pyproject.toml	dependencies.yaml updates the shared &pandas anchor and test matrix pins to cap pandas below 3.0.4a0 and adds comments about the pandas 3.0.4 / Python 3.14 pd.Timedelta import failure; the pyproject.toml files apply the same cap, and dask_cudf/pyproject.toml also updates its copyright text.
Generated conda environment files conda/environments/all_cuda-129_arch-aarch64.yaml, conda/environments/all_cuda-129_arch-x86_64.yaml, conda/environments/all_cuda-133_arch-aarch64.yaml, conda/environments/all_cuda-133_arch-x86_64.yaml	All four conda environment specs change their pandas constraint from >=3.0.0,<3.1.0 to >=3.0.0,<3.0.4a0.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• rapidsai/cudf#22189: Updates the same test_cudf_pandas_compat matrix area in dependencies.yaml that this PR adjusts.

Suggested labels

ci, conda

Suggested reviewers

• vyasr
• mroeschke
• jameslamb

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: excluding pandas 3.0.4 due to a Timedelta segfault on Python 3.14.
Description check	✅ Passed	The description is detailed and directly matches the dependency pinning change and its motivation.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

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• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@dependencies.yaml`:
- Around line 917-920: The `pandas 3.0.4` exclusion is still being bypassed in
the test selectors, so update the selector definitions for
`test_python_cudf_common` and `test_cudf_pandas_compat` to exclude `3.0.4` as
well. Make the same version constraint used by the `pandas` dependency anchor
apply in these test env selectors so Python 3.14 jobs cannot resolve to the
broken release. Locate the relevant test selector entries by their names and
ensure they no longer allow `pandas==3.0.*` without the explicit `!=3.0.4`
guard.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

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Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

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📥 Commits

Reviewing files that changed from the base of the PR and between 4d2410a and 67e5b76.

📒 Files selected for processing (8)

• conda/environments/all_cuda-129_arch-aarch64.yaml
• conda/environments/all_cuda-129_arch-x86_64.yaml
• conda/environments/all_cuda-133_arch-aarch64.yaml
• conda/environments/all_cuda-133_arch-x86_64.yaml
• dependencies.yaml
• python/cudf/pyproject.toml
• python/dask_cudf/pyproject.toml
• python/pylibcudf/pyproject.toml

[bdice]

How confident are we that a fix will land in 3.0.5? I would feel more confident with an upper bound pinning like <3.0.4a0, at least until a fix is filed upstream.

Approving to unblock CI either way.

[galipremsagar]

/merge