From 3cdaacc5e5bed0cacd06dfc975c685523f33c88c Mon Sep 17 00:00:00 2001
From: ChrisRackauckas-Claude <accounts@chrisrackauckas.com>
Date: Fri, 26 Jun 2026 15:02:02 -0400
Subject: [PATCH] Release v3.86.2 with SizedMatrix init_cacheval fix +
 regression test

The `init_cacheval(::GenericLUFactorization/::RFLUFactorization)` regression
for `SizedMatrix` (StaticArrays.LU has no `factors`/`info` field) was fixed in
#1056/#1053 but never released: `Project.toml` still read `3.86.1`, identical to
the registered release, so OrdinaryDiffEq CI kept installing the buggy v3.86.1
and the "Sized Matrix Tests" (Rodas4 over a `SizedMatrix` state) errored with
`type StaticArrays.LU has no field factors`.

Bump to 3.86.2 so the fix ships, and add test/Core/sized_matrix.jl covering the
`init_cacheval` path that threw: `init` of a `LinearProblem{SizedMatrix}` with
the default solver and with explicit `GenericLUFactorization`/`RFLUFactorization`.
The test errors on v3.86.1 with the exact `FieldError` and passes on main.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
---
 Project.toml              |  2 +-
 test/Core/sized_matrix.jl | 27 +++++++++++++++++++++++++++
 test/runtests.jl          |  1 +
 3 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100644 test/Core/sized_matrix.jl

diff --git a/Project.toml b/Project.toml
index 5f8f811ee..207955ffd 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "LinearSolve"
 uuid = "7ed4a6bd-45f5-4d41-b270-4a48e9bafcae"
-version = "3.86.1"
+version = "3.86.2"
 authors = ["SciML"]
 
 [deps]
diff --git a/test/Core/sized_matrix.jl b/test/Core/sized_matrix.jl
new file mode 100644
index 000000000..5200b8cda
--- /dev/null
+++ b/test/Core/sized_matrix.jl
@@ -0,0 +1,27 @@
+using LinearSolve, StaticArrays, RecursiveFactorization, LinearAlgebra, Test
+
+# A `SizedMatrix` (StaticArrays) is an in-place, dense matrix whose
+# `ArrayInterface.lu_instance` returns a `StaticArrays.LU` (fields `L`/`U`/`p`),
+# not a `LinearAlgebra.LU`. `init_cacheval` for `GenericLUFactorization` /
+# `RFLUFactorization` must not assume `lu_instance` yields a `LinearAlgebra.LU`
+# and reach for its `factors`/`info` fields. Regression for
+# SciML/LinearSolve.jl#1056: `init` used to throw
+# `type StaticArrays.LU has no field factors`, which broke the downstream
+# OrdinaryDiffEq "Sized Matrix Tests" (`Rodas4` over a `SizedMatrix` state, whose
+# default solver initializes the `GenericLU`/`RFLU` cachevals).
+
+A = SizedMatrix{9, 9}(rand(9, 9) + 9I)
+b = SizedVector{9}(rand(9))
+
+# `init` is where `init_cacheval` runs; this is the call that used to throw.
+@testset "init does not assume LinearAlgebra.LU for $(typeof(alg))" for alg in (
+        LinearSolve.GenericLUFactorization(), LinearSolve.RFLUFactorization(),
+    )
+    @test init(LinearProblem(A, b), alg) isa LinearSolve.LinearCache
+end
+
+@testset "default init/solve LinearProblem(SizedMatrix)" begin
+    cache = init(LinearProblem(A, b))
+    sol = solve!(cache)
+    @test sol.retcode == ReturnCode.Success
+end
diff --git a/test/runtests.jl b/test/runtests.jl
index 118343b96..bfd9cdfb9 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -70,6 +70,7 @@ else
             @time @safetestset "Nonstructural Zeros" include("Core/nonstructural_zeros.jl")
             @time @safetestset "Default Alg Tests" include("Core/default_algs.jl")
             @time @safetestset "FixedSizeArrays" include("Core/fixedsizearrays.jl")
+            @time @safetestset "SizedMatrix" include("Core/sized_matrix.jl")
             @time @safetestset "Adjoint Sensitivity" include("Core/adjoint.jl")
             @time @safetestset "ForwardDiff Overloads" include("Core/forwarddiff_overloads.jl")
             @time @safetestset "Traits" include("Core/traits.jl")