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docs/src/legacy.md

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+# [Legacy module](@id legacy_module)
+
+JuliaFEM.jl is **0.x**; the default `using JuliaFEM` surface is the type-stable
+pipeline described in `AGENTS.md` (`Element{K,P,S,N}`, `DOFHandler`, domain
+kernels, modern assemblers).
+
+Older tutorials, notebooks, and helper scripts target a **previous** API:
+`Problem` / `Assembly` / `Solver` / `Analysis`, Dict-based fields, legacy element
+constructors, and some mesh readers (for example Abaqus `.inp` and Code Aster
+`.med`). That code lives under `src/legacy/` inside `module Legacy`.
+
+## Enabling Legacy
+
+Set the environment variable **`JULIAFEM_ENABLE_LEGACY=1`** before the first
+`using JuliaFEM` in a Julia session so the `Legacy` submodule is loaded.
+Symbols are namespaced as `JuliaFEM.Legacy.<name>` and are **not** re-exported
+from `JuliaFEM`.
+
+## When to use it
+
+- Porting old scripts or reproducing historical results.
+- Reading meshes or models that still depend on legacy constructors.
+
+For new work, prefer the current API and the Quarto site map at
+`juliafem.github.io/docs/documentation-map.md`.