[lanshuyue]

Reminder

• I read AGENTS.md and docs/developers_guide/agent_governance.md.
• No linked issue: this failure mode was identified during a focused code review.
• Focused tests and PW case checks are listed below.
• User-visible INPUT behavior and core-module impact are described below.
• No governance exception is requested.

Linked Issue

No linked issue; this PR addresses the single-precision PW onsite silent-skip path found during review.

Unit Tests and/or Case Tests for my changes

• cmake --build build --target MODULE_IO_read_item_serial abacus_basic_para -j 4 — passed.
• cmake --build build --target module_pwdft -j 4 — passed.
• cmake --build build --target onsite_op_test MODULE_PW_dftu_base_test MODULE_PW_test_dftu_pw_tools -j 4 — passed.
• OMP_NUM_THREADS=1 ctest --test-dir build --output-on-failure -R '^(onsite_op_test|MODULE_PW_dftu_base_test|MODULE_PW_test_dftu_pw_tools|MODULE_IO_read_item_serial)$' — 4/4 passed outside the restricted sandbox. The first sandboxed run could not initialize MPI; the rerun passed.
• build/abacus_basic_para --version — v3.11.0-beta11; build/abacus_basic_para -h precision — displays the new restriction.
• OMP_NUM_THREADS=1 build/abacus_basic_para --check-input on isolated copies of PW DFT+U and DeltaSpin cases with precision single — both exited 1 with feature-specific errors before SCF.
• Double-precision case checks in /tmp: relax_dftu_spin2 (1 rank) and scf_deltaspin2 (2 MPI ranks) completed. DeltaSpin energy, force, and stress match result.ref. The DFT+U relax values differ from the repository reference by 0.0004037623 eV, 0.002652 force sum, and 0.602177 stress sum. The unmodified upstream/develop code, rebuilt and run on the same isolated input, produced exactly the same values as this patch, so there is no numerical drift from this change.
• python3 tools/03_code_analysis/agent_governance_check.py --staged — no errors; two review warnings explained below.
• git diff --cached --check — passed.
• python3 tools/03_code_analysis/code_quality_score.py --format json source/source_pw/module_pwdft/op_pw_proj.cpp — 79 before, 91 after. This is static quality evidence, not numerical validation.

What's changed?

• Reject single-precision PW Kohn–Sham or TDDFT input when DFT+U or DeltaSpin onsite corrections are enabled, instead of silently applying an empty float operator.
• Pass nspin to OnsiteProj at construction and use it for the existing nspin=1/2/4 potential layout and spin selection. No double-precision arithmetic or kernel was changed.
• Add focused input regression coverage. The unused pointer-copy constructor and existing float stubs remain untouched to keep this fix narrow.

Governance Notes

• INPUT/docs changes: the precision Input_Item help text now states the restriction. Generated documentation is a build artifact and was not committed.
• Core module impact: the PW Hamiltonian passes its existing PARAM.inp.nspin value once into the operator. Four global reads are removed from op_pw_proj.cpp; the PR has a net reduction of three global references. The remaining read belongs at the existing Hamiltonian construction boundary.
• CPU/GPU coverage: CPU build and tests passed. GPU/CUDA/ROCm kernels and runtime were not executed because this build is CPU-only. No float onsite kernel support is claimed.
• Exceptions requested: none.

[ABACUS-PR-BOT]

No new correctness defect found in the inspected precision guard and nspin handoff. One nonblocking diagnostic suggestion is inline. This was a static review of 7df13fa89513e8227924262bf1541a46c987b14e against e5ad53046d4f4c4502bd04657b7fbeba60d97ad4; builds, tests, CLI and numerical checks were not run, and CI diagnostics were unavailable.

[ABACUS-PR-BOT]

Non-blocking: For esolver_type=tddft, switching to double precision still leaves DFT+U and spin constraints unsupported (pw::check_td_input). Please identify that solver restriction in this diagnostic while preserving early rejection.