diff --git a/scripts/check_layer_contract.jl b/scripts/check_layer_contract.jl
new file mode 100644
index 0000000..cc295d1
--- /dev/null
+++ b/scripts/check_layer_contract.jl
@@ -0,0 +1,127 @@
+#!/usr/bin/env julia
+#
+# Static audit for docs/src/developer/architecture_layers.md (layers A–C).
+# Run from anywhere:
+#   julia scripts/check_layer_contract.jl [REPO_ROOT]
+#
+# Uses only Base — no --project required.
+
+const REPO_ROOT = isempty(ARGS) ? dirname(dirname(@__FILE__)) : abspath(ARGS[1])
+
+const INCLUDE_IO_REGEX = r"include\s*\(\s*\"[^\"]*\bio/"
+
+function jl_files(dir::AbstractString)
+    list = String[]
+    isdir(dir) || return list
+    for (root, _, files) in walkdir(dir)
+        for f in files
+            endswith(f, ".jl") || continue
+            push!(list, joinpath(root, f))
+        end
+    end
+    sort!(list)
+end
+
+function code_fragment(line::AbstractString)::SubString{String}
+    # Ignore trailing `# …` so notes do not false-positive the auditors.
+    parts = split(line, '#'; limit = 2)
+    return rstrip(parts[1])
+end
+
+function skip_line(line::AbstractString)::Bool
+    s = strip(line)
+    isempty(s) && return true
+    startswith(s, '#') && return true
+    return false
+end
+
+const DOMAIN_FORBIDDEN_SUBSTRINGS = [
+    "GmshReader",
+    "read_gmsh_mesh",
+    "GmshMesh",
+    "JuliaFEM.Legacy",
+    "KernelAbstractions",
+    "CUDABackend",
+    "MetalBackend",
+    "AMDGPUBackend",
+    "oneAPIBackend",
+]
+
+const FOUNDATION_EXTRA_SUBSTRINGS = [
+    "DOFHandler",
+    "create_structured_box_mesh",
+]
+
+function violations_for_line(line::AbstractString, extra_substrings)::Vector{String}
+    hits = String[]
+    if occursin(INCLUDE_IO_REGEX, line)
+        push!(hits, "include(\"…io/…\")")
+    end
+    for tok in DOMAIN_FORBIDDEN_SUBSTRINGS
+        if occursin(tok, line)
+            push!(hits, tok)
+        end
+    end
+    for tok in extra_substrings
+        if occursin(tok, line)
+            push!(hits, tok)
+        end
+    end
+    return hits
+end
+
+function audit_tree(label::AbstractString, dir::AbstractString, extra_substrings)::Bool
+    ok = true
+    rel = relpath(dir, REPO_ROOT)
+    for path in jl_files(dir)
+        lineno = 0
+        for line in eachline(path)
+            lineno += 1
+            skip_line(line) && continue
+            frag = code_fragment(line)
+            isempty(strip(frag)) && continue
+            hits = violations_for_line(frag, extra_substrings)
+            isempty(hits) && continue
+            ok = false
+            relfile = relpath(path, REPO_ROOT)
+            println(stderr, "$relfile:$lineno: [layer contract] $(join(sort!(unique(hits)), ", "))")
+        end
+    end
+    ok || println(stderr, "($label) violations under $rel")
+    return ok
+end
+
+function main()::Int
+    src = joinpath(REPO_ROOT, "src")
+    isdir(src) || error("expected src/ under $REPO_ROOT")
+
+    println("Layer contract audit (see docs/src/developer/architecture_layers.md)")
+    println("Repository: ", REPO_ROOT)
+
+    all_ok = true
+
+    domains = joinpath(src, "domains")
+    all_ok &= audit_tree("Layer C (domains)", domains, String[])
+
+    foundation_dirs = [
+        joinpath(src, "topology"),
+        joinpath(src, "quadrature"),
+        joinpath(src, "geometry"),
+        joinpath(src, "basis"),
+        joinpath(src, "sparse"),
+    ]
+    for d in foundation_dirs
+        all_ok &= audit_tree("Layer A (foundation)", d, FOUNDATION_EXTRA_SUBSTRINGS)
+    end
+
+    if all_ok
+        println("OK — no forbidden coupling patterns found.")
+        return 0
+    else
+        println(stderr, "")
+        println(stderr, "FAILED — fix imports/includes or move code to an outer layer.")
+        return 1
+    end
+end
+
+exit(main())