AD tests disabled on Julia pre-release due to Zygote.jl incompatibilities

[ChrisRackauckas-Claude]

Summary

AD tests (derivative_tests.jl, nested_ad_tests.jl) are currently excluded from pre-release Julia CI runs due to upstream Zygote.jl incompatibilities with Julia 1.12.

This was implemented in PR #296 by moving AD tests to a separate test group that's excluded from pre-release Julia in the CI matrix.

Upstream Issues

The root cause appears to be Zygote.jl regressions on Julia 1.12:

• broken nested forward diff on julia v1.12 FluxML/Zygote.jl#1594 - Broken nested forward differentiation on Julia 1.12

  • ERROR: non-differentiable function getglobal when using nested pushforward

• failure at handling globals on julia 1.12 FluxML/Zygote.jl#1591 - Failure at handling globals on Julia 1.12

  • Gradient computation returns (nothing, nothing) instead of correct values

• Assertion errors on IR verification on upcoming 1.12 FluxML/Zygote.jl#1580 - Assertion errors on IR verification on Julia 1.12

  • ErrorException: IR verification failed during optimization phase

Action Items

• Monitor upstream Zygote.jl issues for fixes
• Re-enable AD tests on pre-release Julia once Zygote.jl is compatible with Julia 1.12

References

• PR Fix #291: Handle NullParameters in Zygote gradient computation #296 - Moved AD tests to nopre test group
• broken nested forward diff on julia v1.12 FluxML/Zygote.jl#1594
• failure at handling globals on julia 1.12 FluxML/Zygote.jl#1591
• Assertion errors on IR verification on upcoming 1.12 FluxML/Zygote.jl#1580