[ChrisRackauckas-Claude]

Drop SparseConnectivityTracer from the docs environment and FirstOrder tests so NonlinearSolveBase can keep LogExpFunctions = \"1\".

Follow-up to the bound-only workaround in #1200 (leave that PR). After #1198, docs CI failed with:

LogExpFunctions restricted by SparseConnectivityTracer WeakCompat to 0.3.28-0.3 — no versions left

Root cause

NonlinearSolveBase depends on LogExpFunctions (logistic/logit in bounds transforms) with compat "1". Docs and FirstOrder tests also depended on SparseConnectivityTracer. No live SCT version allows LogExpFunctions 1:

SCT	WeakCompat LogExpFunctions
0.6.5 – 0.6.x	0.3.28-0.3
1.x including latest 1.2.2 (2026-06-24)	0.3.28-0.3

Confirmed on SCT main (LogExpFunctions = \"0.3.28\"). SCT is adrhill/SparseConnectivityTracer.jl; Chris is not an owner/maintainer/top contributor (adrhill 184, gdalle 34, …), so this is not filed upstream from here.

What changed

Replace executed TracerSparsityDetector usage with DifferentiationInterface.DenseSparsityDetector (already a docs/test dependency; Symbolics 7.25+ would also allow LEF 1, but is not a docs dep). NSB stays on LogExpFunctions = \"1\".

file	change
docs/Project.toml	drop SparseConnectivityTracer
docs/src/basics/sparsity_detection.md	show DenseSparsityDetector instead of SCT
docs/src/tutorials/large_systems.md	DenseSparsityDetector in executed examples; drop tracer-vs-DI comparison
docs/src/tutorials/snes_ex2.md	same
lib/NonlinearSolveFirstOrder/Project.toml	drop SCT extra/compat/target
FirstOrder sparsity_tests__item{1,2}.jl, rootfind_tests__item19.jl	DenseSparsityDetector

User-facing: NonlinearSolve + SparseConnectivityTracer is still unsatisfiable until SCT allows LogExpFunctions 1. Docs now demonstrate DenseSparsityDetector / SymbolicsSparsityDetector instead. Inlining logistic/logit in NSB to drop the LEF dep entirely would restore SCT coexistence without waiting on adrhill; not done here.

Verification (Julia 1.10.11)

Fresh docs resolve (no Manifest):

LogExpFunctions=1.0.1
SparseConnectivityTracer_in_graph=false
DOCS_RESOLVE_LEF1_OK

FirstOrder test env (after dropping SCT extra): LogExpFunctions=1.0.1, SCT not in graph.

Sparsity tests (local env, DenseSparsityDetector):

Brusselator 2D | 4 passed | 1m48s
Structured Jacobians | 16 passed | 29.7s
Simple Sparse AutoDiff | 16 passed | 26.7s

Docs build: julia +1.10 --project=docs docs/make.jl → DOCS_MAKE_EXIT:0 (Documenter HTML rendered; deploy skipped locally).

Runic.jl --inplace on the three test files; no further diff.

Not verified: GPU, downstream IntegrationTest, full FirstOrder Core (Enzyme/Zygote paths beyond item19), allowed-to-fail jobs.

This PR should be ignored until reviewed by @ChrisRackauckas.

🤖 Generated with Claude Code

[ChrisRackauckas-Claude]

Closing. Do not drop SparseConnectivityTracer from docs/tests. The pin is a stale SCT compat bound, not an API break. Upstream: JuliaDiff/SparseConnectivityTracer.jl#327

[adrhill]

SpaseConnectivityTracer.jl v1.2.3 with the fix has been tagged.