SciML/ModelingToolkit.jl

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An acausal modeling framework for automatically parallelized scientific machine learning (SciML) in Julia. A computer algebra system for integrated symbolics for physics-informed machine learning and automated transformations of differential equations

Stars: 1.7k
Forks: 270
Open beginner issues: 6
Indexed issues: 551
Avg merge: 20h 8m
Merged PRs (30d): 92

Dominant language: Julia
License: No license data
Last GitHub push: Sep 18, 2026
Latest indexed: Sep 19, 2026
Contributing guide: Contributing guide
Code of conduct: Code of conduct
Beginner labels: good first issue

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551 open issues indexed

A shift applied to a whole array variable in a clock partition refers to an undeclared variable Open

Difficulty 4/5 3-5 days Newbie friendliness 52/100

SciML/ModelingToolkit.jl#5169 · Opened Sep 19, 2026
Linearizing a model that contains discrete callbacks (synchronous / clocked subsystems) Open

Difficulty 5/5 Over a week Newbie friendliness 28/100

SciML/ModelingToolkit.jl#5166 · Opened Sep 18, 2026
Lower array-valued constraints of a System into cons/lcons/ucons Open

Difficulty 4/5 3-5 days Newbie friendliness 58/100

SciML/ModelingToolkit.jl#5151 · Opened Sep 13, 2026
Emit MultiObjectiveOptimizationFunction for Systems with several costs Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

SciML/ModelingToolkit.jl#5150 · Opened Sep 13, 2026
write_possibly_indexed_array! should broadcast scalar values to array-shaped keys (remove write_dd_guess!) Open

Difficulty 3/5 1-2 days Newbie friendliness 72/100

SciML/ModelingToolkit.jl#5147 · Opened Sep 13, 2026
Enzyme SCC initialization regresses at concretize_initializeprob on Julia 1.13 Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

SciML/ModelingToolkit.jl#5140 · Opened Sep 13, 2026
Compile and generate code for whole-array equation models without scalarizing per element (tracking) Open

bot-generated needs-chris-review

Difficulty 5/5 Over a week Newbie friendliness 25/100

SciML/ModelingToolkit.jl#5139 · 1 comment · Opened Sep 13, 2026
Array parameter defaults and bindings given as slices of another array parameter fail in MTKParameters Open

bot-generated needs-chris-review

Difficulty 4/5 3-5 days Newbie friendliness 35/100

SciML/ModelingToolkit.jl#5138 · Opened Sep 13, 2026
Flaky: downgrade Initialization `use_scc = true` gradient test returns 1e153 (Dual solve goes non-finite at t=0) Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

SciML/ModelingToolkit.jl#5125 · 1 comment · Opened Sep 12, 2026
Preserve array flow balances when expanding ordinary connector connections Open

bot-generated needs-chris-review

Difficulty 4/5 3-5 days Newbie friendliness 30/100

SciML/ModelingToolkit.jl#5119 · Opened Sep 12, 2026
Unit validation crashes on causal variable `connect`: `unknowns(::BasicSymbolic)` MethodError in MTKDynamicQuantitiesExt Open

Difficulty 2/5 1-3 hours Newbie friendliness 78/100

SciML/ModelingToolkit.jl#5118 · Opened Sep 12, 2026
Preserve array derivatives in implicit DAE residual code generation Open

bot-generated needs-chris-review

Difficulty 4/5 3-5 days Newbie friendliness 55/100

SciML/ModelingToolkit.jl#5097 · Opened Sep 9, 2026
Provide a proven fast path to BrownFullBasicInit instead of downstream build_initializeprob = false workarounds Open

bot-generated needs-chris-review

Difficulty 5/5 Over a week Newbie friendliness 35/100

SciML/ModelingToolkit.jl#5095 · Opened Sep 8, 2026
DAEProblem from a system with array-form differential equations fails with MethodError: no method matching vec(::Bool) Open

bot-generated

Difficulty 4/5 3-5 days Newbie friendliness 48/100

SciML/ModelingToolkit.jl#5093 · 2 comments · Opened Sep 7, 2026
unbound_inputs depends on a string-prefix collision between namespace names Open

Difficulty 5/5 Over a week Newbie friendliness 30/100

SciML/ModelingToolkit.jl#5088 · 1 comment · Opened Sep 7, 2026
[bot-unreviewed] @component rebinds the `name` keyword after the body runs, so closures capturing it see the constructor name Open

bot-generated needs-chris-review

Difficulty 4/5 3-5 days Newbie friendliness 38/100

SciML/ModelingToolkit.jl#5082 · Opened Sep 6, 2026
[bot-unreviewed] Implicit affect solve ignores the ODE solver's tolerance, so a solvable callback throws UnsolvableCallbackError Open

bot-generated needs-chris-review

Difficulty 4/5 3-5 days Newbie friendliness 52/100

SciML/ModelingToolkit.jl#5079 · 1 comment · Opened Sep 6, 2026
[bot-unreviewed] Indexing an array parameter with a discrete Int in a symbolic affect fails in mtkcompile (StableIndex typeassert) Open

Difficulty 4/5 3-5 days Newbie friendliness 42/100

SciML/ModelingToolkit.jl#5078 · Opened Sep 6, 2026
[bot-unreviewed] SymbolicContinuousCallback with affect_neg = nothing still saves and re-initializes at negative crossings Open

Difficulty 3/5 1-2 days Newbie friendliness 62/100

SciML/ModelingToolkit.jl#5077 · Opened Sep 6, 2026
Pyomo cart-pole test with LagrangeLegendre collocation needs ~1920 Ipopt iterations (half the Optimization group's runtime) Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

SciML/ModelingToolkit.jl#5076 · Opened Sep 5, 2026
Array observed state is misclassified as parameter-only by getu Open

Difficulty 3/5 1-2 days Newbie friendliness 72/100

SciML/ModelingToolkit.jl#5072 · Opened Sep 5, 2026
`respecialize`: leaving the value in the operating point gives an uninformative symbolic `MethodError` Open

Difficulty 3/5 1-2 days Newbie friendliness 68/100

SciML/ModelingToolkit.jl#5068 · Opened Sep 4, 2026
`SCCNonlinearProblem` cannot be solved: the generated cache writer calls the cache element type as a constructor Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

SciML/ModelingToolkit.jl#5067 · 1 comment · Opened Sep 4, 2026
`NonlinearSystem(sys)` produces systems that cannot be compiled or turned into a problem (three facets) Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

SciML/ModelingToolkit.jl#5066 · Opened Sep 4, 2026
Downgrade MTKBase QA rewrites test extras into runtime dependencies Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

SciML/ModelingToolkit.jl#5064 · 1 comment · Opened Sep 4, 2026
ModelingToolkitBase QA lane red since #4832: JET typo mode reports 263 errors, 234 of them from Moshi `@match` codegen Open

Difficulty 5/5 Over a week Newbie friendliness 30/100

SciML/ModelingToolkit.jl#5063 · 2 comments · Opened Sep 4, 2026
Downgrade QA fails after test extras are promoted into runtime dependencies Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

SciML/ModelingToolkit.jl#5059 · Opened Sep 1, 2026
Support Dual propagation in out-of-place DAE array residuals Open

Difficulty 3/5 1-2 days Newbie friendliness 68/100

SciML/ModelingToolkit.jl#5053 · Opened Aug 31, 2026
Reverse-mode adjoints fail for any system with a continuous event Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

SciML/ModelingToolkit.jl#5018 · 2 comments · Opened Aug 25, 2026
After index reduction the Fekete index-3 DAE goes Unstable at t ~ 4 of 1000, even with exact initialization; hand-written index-2 form of the same model reaches t = 1000 Open

Difficulty 5/5 Over a week Newbie friendliness 42/100

SciML/ModelingToolkit.jl#5012 · Opened Aug 23, 2026
Defaults on index-reduced-away states become hard ICs: overdetermined AND inconsistent initialization system (120 eqs / 60 unknowns, least squares stalls at ||r||inf = 18.7) Open

Difficulty 5/5 Over a week Newbie friendliness 30/100

SciML/ModelingToolkit.jl#5011 · Opened Aug 23, 2026
Pyomo 2 dynamic optimization extension fails on PythonCall callback and symbolic operations Open

Difficulty 4/5 3-5 days Newbie friendliness 52/100

SciML/ModelingToolkit.jl#5005 · Opened Aug 21, 2026
Initialization fails if there is no consumer of a GlobalScope parameter in the system Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 55/100

SciML/ModelingToolkit.jl#4990 · Opened Aug 18, 2026
MTK SDDE ArgumentError when Connecting two Components Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 48/100

SciML/ModelingToolkit.jl#4985 · 4 comments · Opened Aug 17, 2026
sorted_incidence_matrix fails on a simplified scalar ODE Open

SciML/ModelingToolkit.jl#4961 · 1 assignee · Opened Aug 14, 2026
QA: JET package analysis exceeds the 60-minute root QA budget Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

SciML/ModelingToolkit.jl#4958 · 8 comments · Opened Aug 14, 2026
Repair strict Documentation failures on the linear analysis API page Open

Difficulty 4/5 3-5 days Newbie friendliness 52/100

SciML/ModelingToolkit.jl#4957 · Opened Aug 13, 2026
Seeded Poissonians SIR mean assertion is process-nondeterministic Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

SciML/ModelingToolkit.jl#4944 · Opened Aug 11, 2026
Remove stale structural-transformation internals from strict docs Open

Difficulty 2/5 1-3 hours Newbie friendliness 84/100

SciML/ModelingToolkit.jl#4943 · 2 comments · Opened Aug 11, 2026
ModelingToolkitBase discrete-system tests use SciMLBase without importing it Open

Difficulty 1/5 Under an hour Newbie friendliness 88/100

SciML/ModelingToolkit.jl#4937 · Opened Aug 11, 2026
History-aware initialization for delayed `System`s Open

bug

Difficulty 5/5 Over a week Newbie friendliness 35/100

SciML/ModelingToolkit.jl#4935 · 1 comment · Opened Aug 11, 2026
Optimization tests construct incomplete parameters for expression trajectories Open

Difficulty 3/5 1-2 days Newbie friendliness 72/100

SciML/ModelingToolkit.jl#4925 · Opened Aug 10, 2026
Raise the LinearSolve 5.x floor past the ForwardDiff issquare import bug Open

Difficulty 2/5 1-3 hours Newbie friendliness 84/100

SciML/ModelingToolkit.jl#4924 · Opened Aug 10, 2026
Raise BoundaryValueDiffEqMIRK floor past the RecursiveArrayTools v4 interpolation bug Open

Difficulty 2/5 1-3 hours Newbie friendliness 88/100

SciML/ModelingToolkit.jl#4923 · Opened Aug 10, 2026
Raise ModelingToolkitBase DiffEqBase floor for symbolic diagnostics Open

Difficulty 2/5 1-3 hours Newbie friendliness 86/100

SciML/ModelingToolkit.jl#4922 · Opened Aug 10, 2026
MTKBase compatibility-floor CI errors when Julia 1.10 inference tests unexpectedly pass Open

Difficulty 2/5 1-3 hours Newbie friendliness 76/100

SciML/ModelingToolkit.jl#4911 · 1 comment · Opened Aug 9, 2026
Clean master Runic fails on InitializationProblem return Open

Difficulty 1/5 Under an hour Newbie friendliness 92/100

SciML/ModelingToolkit.jl#4908 · Opened Aug 9, 2026
QA: the ExplicitImports *_via_owners checks still fail on the lts (Julia 1.10) half of the matrix Open

Difficulty 4/5 3-5 days Newbie friendliness 52/100

SciML/ModelingToolkit.jl#4903 · 1 comment · Opened Aug 7, 2026
Optimization on MTK based SteadyStateProblem fails with AutoForwardDiff due to MTKParameter type change Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 45/100

SciML/ModelingToolkit.jl#4898 · 2 comments · Opened Aug 6, 2026
Wrong dense output in the event-truncated step for mass-matrix systems with SymbolicContinuousCallback Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

SciML/ModelingToolkit.jl#4896 · Opened Aug 6, 2026

SciML/ModelingToolkit.jl

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