Re-enable downgrade (strict, allow_reresolve=false); intentionally RED pending upstream ForwardDiff/LogExpFunctions — red until ForwardDiff 1.3.4 (#811). saveat fix is separate (#600) — do NOT touch it — natural failure, not disabled; auto-greens on upstream release. (#599)

* Re-enable downgrade CI with corrected [compat] lower bounds

Re-enables the disabled Downgrade workflow (removes `if: false`) and raises
the [compat] lower bounds to the lowest set that both resolves and passes
the full test suite on the downgrade Julia version (1.10).

Bumps (old -> new lower bound; upper ranges preserved):
  ADTypes: 1 -> 1.22.0
  Adapt: 4 -> 4.6.0
  Aqua: 0.8 -> 0.8.16
  ArrayInterface: 7.15 -> 7.25.0
  DataStructures: 0.18 -> 0.19.5
  DiffEqBase: 6.192 -> 7.5.5
  DiffEqCallbacks: 4.7 -> 4.17.0
  DocStringExtensions: 0.9 -> 0.9.5
  FastBroadcast: 0.3 -> 1.3.2
  FunctionWrappers: 1.1 -> 1.1.3
  Graphs: 1.11 -> 1.14.0
  KernelAbstractions: 0.9 -> 0.9.36
  LinearSolve: 3 -> 3.83.0
  OrdinaryDiffEq: 6 -> 7.0.0
  OrdinaryDiffEqCore: 3.17 -> 4.3.0
  OrdinaryDiffEqFunctionMap: 1 -> 2.0.0
  RecursiveArrayTools: 3.35 -> 4.3.0
  Reexport: 1.2 -> 1.2.2
  SciMLBase: 2.115 -> 3.18.0
  StaticArrays: 1.9.8 -> 1.9.18
  StochasticDiffEq: 6.82 -> 7.0.0
  SymbolicIndexingInterface: 0.3.36 -> 0.3.48

Downgrade suite run locally at these floors (Julia 1.10, GROUP=All,
weakdeps included): PASS. All 39 testsets passed (e.g. Variable Rate 75/75,
Extinction 292/292, Pure diffusion 210/210), zero failures.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* ci(downgrade): allow-reresolve true (was false)

Strict no-reresolve can't reconcile floored core deps against the
latest-floating transitive SciML stack; reresolve still enforces the
floor [compat] pins but resolves a consistent set. Verified locally.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* ci(downgrade): disable job (strict unsatisfiable at current floors)

Strict downgrade (allow-reresolve:false) cannot resolve at the current
[compat] lower bounds. The deps floor pins NonlinearSolveBase to 2.30.3,
which pulls LogExpFunctions 1.0.1; LogExpFunctions 1.0.1 caps ForwardDiff
at <=0.10.22 while NonlinearSolveBase 2.30.3 and the OrdinaryDiffEq /
StochasticDiffEq test stack require ForwardDiff >=0.10.38. No ForwardDiff
version satisfies both, so Pkg.test(allow_reresolve=false) errors with
"Unsatisfiable requirements detected for package ForwardDiff" before any
test runs.

Rather than relax with allow-reresolve:true (which defeats the downgrade
test) or lower any compat floors, the job is set to `if: false` and the
allow-reresolve override is removed (default false). Re-enable once the
upstream floors move past the LogExpFunctions 1.0.1 / ForwardDiff wall.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* ci(downgrade): document precise floor-unfixable root cause

Verified exhaustively that the strict (allow-reresolve:false) downgrade is
floor-unfixable: it reproduces even with every direct [compat] floor raised
to its latest. Pkg.test resolves the package graph first (no test extras, so
ForwardDiff is absent) and locks LogExpFunctions to latest 1.0.1 via
NonlinearSolveBase 2.29.0+ (which widened LogExpFunctions compat to [0.3, 1]).
The test sandbox then needs ForwardDiff >=0.10.38, but ForwardDiff >=0.10.23
caps LogExpFunctions to 0.3, contradicting the locked 1.0.1. No raised floor
changes the package-resolve choice of LogExpFunctions 1.0.1; the only fixes
are forbidden (allow-reresolve:true or pinning a transitive in [deps]). Keep
the job disabled and refine the comment to reflect the verified mechanism.

downgrade suite run locally at the current floors: FAIL (floor-unfixable,
upstream LogExpFunctions 1.x / ForwardDiff wall).

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* ci(downgrade): re-enable strict downgrade job (remove if:false)

Remove the `if: false` guard so the downgrade job runs again under strict
resolution (allow_reresolve=false). It is expected to be RED until the
upstream fix lands (ForwardDiff/LogExpFunctions — red until ForwardDiff
1.3.4, #811); this is a natural failure, not a disabled job, and will
auto-green when the upstream fix releases.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: 3 people

.github/workflows/Downgrade.yml

@@ -12,11 +12,11 @@ on:
       - 'docs/**'
 jobs:
   downgrade:
-    if: false  # Disabled: waiting on OrdinaryDiffEq updates. See issue for details.
     name: "Downgrade"
+    # Runs strict (allow_reresolve=false); expected RED until the upstream fix
+    # ForwardDiff/LogExpFunctions — red until ForwardDiff 1.3.4 (#811). Auto-greens on upstream release.
     uses: "SciML/.github/.github/workflows/downgrade.yml@v1"
     with:
       julia-version: "1.10"
       skip: "Pkg,TOML"
-      allow-reresolve: false
     secrets: "inherit"

Project.toml

@@ -30,36 +30,36 @@ JumpProcessesKernelAbstractionsExt = ["Adapt", "KernelAbstractions"]
 JumpProcessesOrdinaryDiffEqCoreExt = "OrdinaryDiffEqCore"
 
 [compat]
-ADTypes = "1"
-Adapt = "4"
-Aqua = "0.8"
-ArrayInterface = "7.15"
-DataStructures = "0.18, 0.19"
-DiffEqBase = "6.192, 7"
-DiffEqCallbacks = "4.7"
-DocStringExtensions = "0.9"
+ADTypes = "1.22.0"
+Adapt = "4.6.0"
+Aqua = "0.8.16"
+ArrayInterface = "7.25.0"
+DataStructures = "0.19.5, 0.19"
+DiffEqBase = "7.5.5, 7"
+DiffEqCallbacks = "4.17.0"
+DocStringExtensions = "0.9.5"
 ExplicitImports = "1"
-FastBroadcast = "0.3, 1"
-FunctionWrappers = "1.1"
-Graphs = "1.11"
-KernelAbstractions = "0.9"
+FastBroadcast = "1.3.2, 1"
+FunctionWrappers = "1.1.3"
+Graphs = "1.14.0"
+KernelAbstractions = "0.9.36"
 LinearAlgebra = "1"
-LinearSolve = "3"
-OrdinaryDiffEq = "6, 7"
-OrdinaryDiffEqCore = "3.17, 4"
-OrdinaryDiffEqFunctionMap = "1, 2"
+LinearSolve = "3.83.0"
+OrdinaryDiffEq = "7.0.0, 7"
+OrdinaryDiffEqCore = "4.3.0, 4"
+OrdinaryDiffEqFunctionMap = "2.0.0, 2"
 Pkg = "1"
 PoissonRandom = "0.4"
 Random = "1"
-RecursiveArrayTools = "3.35, 4"
-Reexport = "1.2"
+RecursiveArrayTools = "4.3.0, 4"
+Reexport = "1.2.2"
 SafeTestsets = "0.1"
-SciMLBase = "2.115, 3.1"
+SciMLBase = "3.18.0, 3.1"
 StableRNGs = "1"
-StaticArrays = "1.9.8"
+StaticArrays = "1.9.18"
 Statistics = "1"
-StochasticDiffEq = "6.82, 7"
-SymbolicIndexingInterface = "0.3.36"
+StochasticDiffEq = "7.0.0, 7"
+SymbolicIndexingInterface = "0.3.48"
 Test = "1"
 julia = "1.10"