[borisbat]

Behavior change: the nightly matrix no longer runs a windows 64 Debug cell. The per-PR matrix is unchanged; the four other Debug cells keep covering the Debug-only interpreter paths.

Why. An MSVC Debug sweep of tests/ takes most of an hour on the hosted runner, and the lane's run_build || run_build_isolated retry turns one missed watchdog into a four-hour job. On #4495 the merged lint project suite ran 1775 s as one ctest there, past dastest's 1200 s default, and the cell then sat in its isolated retry for the rest of the night; master's own nightly the same day took 37 min, so the cell flips on any slow suite.

What changes.

• ci/ci_matrix.py drops the cell; the raised sweep watchdogs (SLOW_SWEEP_BUDGETS) now name the sanitizer cells alone.
• ci/test_ci_matrix.py: the nightly-only cell list loses that one name and the half-speed assertion keys on sanitizers only. No assertion is dropped or loosened beyond the removed cell.
• utils/CMakeLists.txt: the lint_project_* ctest's Windows Debug exemption from utils, dastest/tests: suites merge by topic; lint exe; shape gate per root #4495 goes with the cell.
• tests/CMakeLists.txt and skills/internal/preflight.md stop naming the cell.

Where to look. ci/ci_matrix.py build_cells, ci/test_ci_matrix.py NIGHTLY_ONLY_BUILD.

Validation and notes

Validation

• python3 ci/test_ci_matrix.py: 27 tests pass; ci_matrix.py build_nightly lists 16 cells, windows 32 and 64 Release only.
• No workflow names the cell: build_matrix.yml and nightly.yml take the matrix from the script.

Not done

• The windows cells still have no Debug build at all; a Debug-only MSVC regression surfaces on a developer box, as it did before the nightly cell existed.

[Copilot]

Note

Copilot was unable to complete this review at the selected tier due to model policy or plan restrictions.

🟢 Approval recommended

The change is a straightforward CI-matrix maintenance update (removing a nightly-only Windows Debug lane) with corresponding test expectation and documentation adjustments, and the provided context indicates no active issues blocking approval.

No open issues 🎉

What changed in this PR

This pull request removes the Windows x64 Debug job from the nightly CI build matrix (leaving the per-PR matrix unchanged) and updates tests, CMake notes, and internal documentation to match the new nightly configuration.

Changes:

• Drop the nightly-only windows-64-Debug-none cell from ci/ci_matrix.py.
• Update ci/test_ci_matrix.py pinned expectations and “slow/raised watchdog budget” assertions to align with the reduced nightly matrix.
• Remove remaining references/exemptions for the deleted lane in CMake and internal docs.

File	Summary
utils/​CMakeLists.txt	Removes the Windows Debug-specific exclusion for lint_project_* ctests now that the nightly lane is removed.
tests/​CMakeLists.txt	Updates comments/documentation around sweep/watchdog budgets to no longer reference the removed Windows Debug nightly lane.
skills/​internal/​preflight.md	Updates internal CI/preflight documentation to stop naming the deleted nightly cell.
ci/​test_ci_matrix.py	Updates matrix tests to remove the nightly Windows x64 Debug cell and adjust related assertions accordingly.
ci/​ci_matrix.py	Removes the Windows x64 Debug nightly build cell and updates associated rationale/comments.

_{Review effort: Balanced}