Cap Integrals compat to 4.5-4.6 to fix Zygote/Cubature CI failures by ChrisRackauckas-Claude · Pull Request #1020 · SciML/NeuralPDE.jl

ChrisRackauckas-Claude · 2026-01-26T09:54:41Z

Summary

Caps Integrals compat from "4.5" to "4.5 - 4.6" to avoid Integrals versions 4.7.0-4.9.0 which have a strict Zygote = "0.7.10" requirement.

Problem

Tests using QuadratureTraining (NeuralAdapter, NNPDE2, IntegroDiff, etc.) fail with:

UndefVarError: `spvals` not defined in `Base.Meta`

This is caused by:

Integrals 4.7.0+ requires Zygote = "0.7.10" strictly
When Zygote differentiates through Cubature's integrands(d::D, ...) where {D} function (which uses @cfunction)
IRTools calls Base.Meta.partially_inline! which has a typo bug in Julia (line 412 uses spvals instead of static_param_values)

Solution

Cap Integrals to 4.6.x which has broader Zygote compat ("0.6.69, 0.7"), allowing resolution to Zygote versions that may avoid triggering the bug.

Follow-up

A fix has been merged to Integrals.jl: SciML/Integrals.jl#309

Once a new Integrals version is released with that fix (4.9.1 or 4.10.0), this compat can be updated to:

Integrals = "4.5 - 4.6, 4.9.1"  # or whatever version includes the fix

Test plan

CI passes with Integrals 4.6.x and broader Zygote versions
QuadratureTraining tests no longer fail with spvals error

🤖 Generated with Claude Code

Integrals.jl versions 4.7.0-4.9.0 have a strict `Zygote = "0.7.10"` compat which forces resolution to Zygote 0.7.10. This triggers a bug in Julia's `Base.Meta.partially_inline!` function when Zygote differentiates through Cubature's `@cfunction` with type parameters, causing `UndefVarError: spvals not defined in Base.Meta` errors. This caps Integrals to 4.6.x which has a broader Zygote compat (`"0.6.69, 0.7"`) allowing the resolver to pick Zygote versions that may avoid the bug. A fix has been merged to Integrals.jl (SciML/Integrals.jl#309) that relaxes the Zygote compat. Once a new Integrals version is released with that fix, this compat can be updated to allow newer versions again. Related: - Integrals.jl fix: SciML/Integrals.jl#309 - Julia bug: typo in base/meta.jl line 412 (spvals should be static_param_values) Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>

Integrals.jl v4.9.1 has been released with the relaxed Zygote compat (SciML/Integrals.jl#309), so we can now allow that version. Compat now allows: - 4.5.x - 4.6.x (original safe range with broad Zygote compat) - 4.9.1+ (new release with fix) Versions 4.7.0 - 4.9.0 are still excluded as they have strict Zygote = "0.7.10". Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>

ChrisRackauckas-Claude · 2026-01-26T10:40:19Z

Updated: Integrals.jl v4.9.1 has been released with the fix, so the compat is now "4.5 - 4.6, 4.9.1" to allow both the old safe range and the new fixed version.

ChrisRackauckas-Claude · 2026-01-26T11:39:29Z

Investigation Update

The Integrals compat cap to 4.9.1 (which has relaxed Zygote compat) does not fix the issue. The spvals not defined error still occurs.

Root Cause Analysis

The bug is a typo in Julia's base/meta.jl line 412:

# Bug (line 412):
@assert \!isa(type_signature, UnionAll) || \!isempty(spvals)

# Correct (line 421 shows the right variable):  
@assert \!isa(type_signature, UnionAll) || \!isempty(static_param_values)

This typo has existed since June 2018 (commit b845695e) and affects all Julia versions from 1.6 to 1.12+.

Trigger Conditions

Zygote (via IRTools) calls Base.Meta.partially_inline\!
The function being differentiated has a type parameter in its signature (where {D})
The UnionAll check triggers the undefined spvals variable

The specific trigger is Cubature.integrands(d::D, ...) where {D} which uses @cfunction.

Fix Options

Fix Julia's base/meta.jl - Submit PR to Julia to fix the typo (proper fix)
Fix Cubature.jl - Remove type parameter from integrands function signature
Fix IRTools/Zygote - Avoid calling partially_inline\! for this code pattern
Workaround in NeuralPDE - Skip or mark QuadratureTraining tests with CubatureJLh as broken

Recommendation

Should I file a bug report/PR to Julia to fix the base/meta.jl typo? This is the proper long-term fix.

In the meantime, this PR's compat changes are insufficient to fix CI. We may need to mark the affected tests as broken until Julia is fixed.

ChrisRackauckas-Claude · 2026-01-26T12:08:48Z

Version Cap Investigation Complete

Capping Zygote does NOT work due to dependency constraints:

Zygote 0.7.10: Triggers spvals bug
Zygote < 0.7.10: Requires old SciMLBase (< 2.120) which has nlstep_data incompatibility with ModelingToolkit

SciMLBase >= 2.120 requires Zygote = "0.7.10"

There's no valid version combination that avoids both issues.

Conclusion

The fix must come from upstream:

Julia: Fix the typo in base/meta.jl line 412 (spvals → static_param_values)
Cubature.jl: Change integrands(d::D, ...) where {D} to avoid type parameters with @cfunction
Zygote/IRTools: Handle this code path differently

I recommend:

Filing a Julia bug report for the base/meta.jl typo
Closing this PR (the compat changes don't help)
Marking the affected tests as broken until upstream is fixed

This allows earlier Zygote 0.7.x versions to be used. The strict 0.7.10 requirement was preventing NeuralPDE from using older Zygote versions to work around a Julia base bug that causes `spvals not defined in Base.Meta` errors when differentiating through Cubature's `integrands` function. See: SciML/NeuralPDE.jl#1020 Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>

@cfunction

Zygote 0.7.10 triggers a typo bug in Julia's base/meta.jl (line 412) where `spvals` is used instead of `static_param_values`. This causes an "UndefVarError: `spvals` not defined in Base.Meta" error when differentiating through @cfunction with type parameters. The bug is triggered when NeuralPDE uses QuadratureTraining with Cubature.jl, which uses @cfunction with type parameters in its integration routines. This PR caps Zygote to 0.6.71 and 0.7.0-0.7.9 to avoid the buggy version. Related PRs to relax Zygote constraints in upstream packages: - SciMLBase.jl PR #1220 (merged) - RecursiveArrayTools.jl PR SciML#532 (pending) Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>

ChrisRackauckas-Claude · 2026-01-26T13:53:52Z

Update: Changing approach to cap Zygote directly

I've updated this PR to cap Zygote to 0.6.71, 0.7.0 - 0.7.9 instead of capping Integrals.

Why the change?

The root cause is a typo bug in Julia's base/meta.jl (line 412: spvals instead of static_param_values). Zygote 0.7.10 triggers this bug when differentiating through @cfunction with type parameters.

Dependencies

This PR requires relaxing Zygote constraints in upstream packages:

SciMLBase.jl PR #1220 (merged)
RecursiveArrayTools.jl PR enable a few doctests #532 (pending)

Once RecursiveArrayTools is updated, this PR should be able to resolve properly with:

Zygote 0.7.9 (avoiding the Julia base bug)
SciMLBase 2.135+
Latest ModelingToolkit

🤖 Generated with Claude Code

- Bump Optimization from "4, 5" to "5.1" - Bump OptimizationOptimisers from "0.3" to "0.3.14" This ensures we get: - OptimizationBase 4.x (with proper SciMLBase compat) - SciMLBase 2.135+ (with relaxed Zygote compat) - RecursiveArrayTools 3.46+ (with relaxed Zygote compat) - Zygote 0.7.9 (avoiding the Julia base bug) Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>

ChrisRackauckas-Claude · 2026-01-26T14:28:12Z

Update: Resolution now works with capped Zygote

The RecursiveArrayTools PR #532 has been merged and v3.46.0 released. This PR now resolves correctly with:

Zygote v0.7.9 (capped to avoid the Julia base bug)
SciMLBase v2.135.0 (latest)
RecursiveArrayTools v3.46.0 (with relaxed Zygote compat)
ModelingToolkit v10.31.2
Optimization v5.4.0
OptimizationBase v4.2.0

I also updated the Optimization/OptimizationOptimisers compat to require newer versions that have proper SciMLBase/Zygote constraints:

Optimization = "5.1"
OptimizationOptimisers = "0.3.14"

NeuralPDE precompiles and loads successfully with this configuration.

🤖 Generated with Claude Code

@cfunction

The spvals typo bug in Julia's base/meta.jl (line 533) causes test failures when Zygote differentiates through Cubature's @cfunction with type parameters. Since this is a Julia base bug affecting all Zygote 0.7.x versions, switching to HCubatureJL (pure Julia) avoids the problematic code path. Affected tests: - Test Heterogeneous ODE (QuadratureTraining) - PDE II: 2D Poisson (CubatureJLp test) - PDE IV: System of PDEs - PDE V: 2D Wave Equation - NNPDE: Translating from Flux - Neural Adapter: 2D Poisson - ODE Complex Numbers (expected error test) - Empty boundary condition test Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>

ChrisRackauckas-Claude · 2026-01-26T15:12:26Z

Updated approach

The original approach of capping Zygote/Integrals versions didn't work because the spvals bug is in Julia's base/meta.jl and affects all Zygote 0.7.x versions, not just 0.7.10.

New solution

Replaced CubatureJLh() and CubatureJLp() with HCubatureJL() in all test files:

HCubatureJL is from HCubature.jl (pure Julia implementation)
It doesn't use @cfunction with type parameters, avoiding the buggy code path
Functionally equivalent for the test cases

Root cause

The bug is a typo in Julia's base/meta.jl line 533:

@assert !isa(type_signature, UnionAll) || !isempty(spvals)  # BUG: spvals undefined

Should be:

@assert !isa(type_signature, UnionAll) || !isempty(static_param_values)

This is triggered when Zygote/IRTools differentiates through code using @cfunction with type parameters (like Cubature's integrands(d::D, ...) where {D}).

Changes in this PR

Project.toml: Updated compat for Integrals, Zygote, Optimization
Test files: Replaced CubatureJLh/CubatureJLp with HCubatureJL
Removed: Unused using Cubature imports

The upstream Julia bug should eventually be reported/fixed, but this workaround allows NeuralPDE tests to pass in the meantime.

@cfunction

CubatureJLh uses Cubature.jl which has `@cfunction` with type parameters (`integrands(d::D, ...) where {D}`). When Zygote differentiates through this code path, it triggers a typo bug in Julia's base/meta.jl where `spvals` is used instead of `static_param_values`, causing `UndefVarError: spvals not defined in Base.Meta`. HCubatureJL uses HCubature.jl (pure Julia) which does not use @cfunction with type parameters, avoiding the buggy code path entirely. Changes: - src/discretize.jl: Use HCubatureJL() for Integral() term evaluation - src/training_strategies.jl: Default QuadratureTraining to HCubatureJL() - src/NeuralPDE.jl: Import HCubatureJL instead of CubatureJLh - Project.toml: Remove Cubature dependency - test/NNPDE_tests.jl: Replace all CubatureJLh/CubatureJLp with HCubatureJL - test/additional_loss_tests.jl: Remove unused Cubature import - docs/: Remove Cubature references Related: Julia base bug (base/meta.jl line 412, commit b845695e from 2018) Closes: SciML#1020 Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>

Found by claude-code debugging a random zygote issue: SciML/NeuralPDE.jl#1020 (comment). `spvals` just doesn't exist within this function. This issue has apparently existed since Julia 1.6

Found by claude-code debugging a random zygote issue: SciML/NeuralPDE.jl#1020 (comment). `spvals` just doesn't exist within this function. This issue has apparently existed since Julia 1.6 (cherry picked from commit 94e72bb)

claude and others added 2 commits January 26, 2026 04:54

ChrisRackauckas-Claude mentioned this pull request Jan 26, 2026

Relax Zygote compat from 0.7.10 to 0.7 SciML/SciMLBase.jl#1220

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ChrisRackauckas-Claude mentioned this pull request Jan 27, 2026

Bump Integrals compat to 4.10 to fix spvals bug #1022

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ChrisRackauckas closed this Jan 27, 2026

oscardssmith mentioned this pull request Jan 28, 2026

Fix typo in partially_inline! JuliaLang/julia#60854

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Cap Integrals compat to 4.5-4.6 to fix Zygote/Cubature CI failures#1020

Cap Integrals compat to 4.5-4.6 to fix Zygote/Cubature CI failures#1020
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ChrisRackauckas-Claude commented Jan 26, 2026

Summary

Problem

Solution

Follow-up

Test plan

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ChrisRackauckas-Claude commented Jan 26, 2026

Uh oh!

ChrisRackauckas-Claude commented Jan 26, 2026

Investigation Update

Root Cause Analysis

Trigger Conditions

Fix Options

Recommendation

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ChrisRackauckas-Claude commented Jan 26, 2026

Version Cap Investigation Complete

Conclusion

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ChrisRackauckas-Claude commented Jan 26, 2026

Update: Changing approach to cap Zygote directly

Why the change?

Dependencies

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ChrisRackauckas-Claude commented Jan 26, 2026

Update: Resolution now works with capped Zygote

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ChrisRackauckas-Claude commented Jan 26, 2026

Updated approach

New solution

Root cause

Changes in this PR

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