0103 — Lodestar.Gpu ships netstandard2.1 beside net10.0

Status: accepted · Date: 2026-09-10 · Amends: 0101

Context

Decision 0101 gave Lodestar.Gpu a single target framework. It argued two things, read from the package: that ILGPU 1.5.3 publishes no netstandard2.0 asset, so that target is absent upstream rather than a gap a polyfill could close; and that net10.0 was preferable to the net8.0 #444 proposed, because ILGPU's newest asset is net7.0 and both consume it identically.

Both remain true. Neither is an argument about netstandard2.1, which ILGPU also publishes, and 0101 never weighed it — the record went from "not netstandard2.0" straight to "net10.0 alone" with nothing in between. This amends that step.

What the omission cost

net10.0 alone excludes every consumer that is not on .NET 10. That includes .NET 8, which is LTS until November 2026, and Mono and Unity. ILGPU ships net6.0 and net7.0 assets precisely to serve those callers, and a package wrapping it that reaches none of them narrows the dependency rather than adapting it.

0101's reasoning for net10.0 over net8.0 was about testing — a second moniker ILGPU does not distinguish adds a matrix dimension and proves nothing. That is still right, and it does not transfer: netstandard2.1 is not another flavour of the same reach, it is a contract ILGPU declares and a strictly wider audience.

The measurement

Adding netstandard2.1 produced 50 compile errors, every one of them the same cause: ArgumentNullException.ThrowIfNull and ArgumentOutOfRangeException.ThrowIfLessThan, static helpers that exist on .NET 6 and 8 and not on netstandard2.1. No algorithm, no ILGPU API, no kernel.

src/Shared/Guard.cs already answers exactly that, and has since the first package: Guard.NotNull and Guard.NotLessThan carry the one #if so no call site does. The other fifteen packages use them because they target netstandard2.0. Swapping the call sites took the build to zero errors, and it leaves Lodestar.Gpu consistent with its siblings rather than the only package reaching for BCL helpers the rest cannot.

Decision

Lodestar.Gpu targets net10.0;netstandard2.1.

net10.0 stays, so a caller on the newest runtime gets the assets compiled against it. netstandard2.1 is the floor ILGPU itself declares, so the package reaches what its dependency reaches and no further.

The mirror is the half that makes this honest

A second target framework that nothing executes is the failure #529 was about: compile-verified, never run, every test green and half of them proving nothing. So tests/Lodestar.Gpu.NetStandard.Tests replays the whole suite against the netstandard2.1 build — the first mirror in this repository pinned to 2.1 rather than 2.0 — and its NetStandardAssemblyGuardTests asserts the loaded assembly's TargetFrameworkAttribute is .NETStandard,Version=v2.1.

tools/check_netstandard_guards.py was taught the difference rather than given an exception. It now reads the contract per package from a MIRRORED table instead of a constant, checks that the library actually declares the framework its mirror claims to replay, and reports a mirror pinning nothing as a finding. That last one matters: before the change, a 2.1 mirror passed the 2.0 guard vacuously — Lodestar.Gpu has no Lodestar dependency to pin, so there was nothing to fail on, and the guard printed "16 netstandard2.0 mirrors" while one of them was not.

What 0101 keeps

Everything except the framework list.

• No src/ project may reference Lodestar.Gpu. A wider target makes this easier to forget, not less necessary: the SIMD path is still the only path a netstandard2.0 caller has.
• Satellite tier by 0076, ILGPU's NCSA licence read from LICENSE.txt inside the package because no SPDX expression is declared, and the device-selection and measurement rules in 0102.
• netstandard2.0 is still absent upstream and still not offered.

Consequences

• tools/check_nuspec_dependencies.py gains a .NETStandard2.1 group for this package alone.
• CLAUDE.md's table says two frameworks rather than one.
• The repository now has sixteen mirrors, fifteen on 2.0 and one on 2.1.