diff --git a/.forgejo/workflows/ci.yaml b/.forgejo/workflows/ci.yaml
index 41d6305..b59b17e 100644
--- a/.forgejo/workflows/ci.yaml
+++ b/.forgejo/workflows/ci.yaml
@@ -10,6 +10,14 @@ on:
 jobs:
   build-test-release:
     runs-on: arch-latest
+    env:
+      # x86-64-v2 = SSE4.2 baseline; runs on the CI SBC (Intel N5105 / Tremont,
+      # no AVX) and on essentially every x86_64 CPU since ~2011. v3 is out —
+      # it requires AVX2 the SBC doesn't have, so the bootstrap binary
+      # wouldn't even run there. mtune=generic keeps codegen balanced across
+      # consumer CPUs.
+      CRAFTER_BUILD_MARCH: x86-64-v2
+      CRAFTER_BUILD_MTUNE: generic
     steps:
       - name: Install build dependencies
         run: |
@@ -83,7 +91,9 @@ jobs:
           ls -la dist/
 
       - name: Upload workflow artifacts
-        uses: actions/upload-artifact@v4
+        # v4+ uses a GHES-only upload API Forgejo Actions doesn't implement;
+        # v3 stays on the older API that works on Forgejo.
+        uses: actions/upload-artifact@v3
         with:
           name: crafter-build
           path: dist/
diff --git a/project.cpp b/project.cpp
index af5b272..54ac2c0 100644
--- a/project.cpp
+++ b/project.cpp
@@ -11,11 +11,22 @@ extern "C" Configuration CrafterBuildProject(std::span<const std::string_view> a
         else if (arg.starts_with("--target=")) target = std::string(arg.substr(std::string_view("--target=").size()));
     }
 
+    // Honor CRAFTER_BUILD_MARCH/MTUNE so CI (which sets these for portability)
+    // applies them to both the self-rebuild and the mingw cross-compile —
+    // otherwise Configuration's "native" defaults bake in the build host's
+    // CPU and the published artifact's portability becomes accidental.
+    const char* envMarch = std::getenv("CRAFTER_BUILD_MARCH");
+    const char* envMtune = std::getenv("CRAFTER_BUILD_MTUNE");
+    std::string march = (envMarch && *envMarch) ? envMarch : "native";
+    std::string mtune = (envMtune && *envMtune) ? envMtune : "native";
+
     static auto crafterBuildLib = std::make_unique<Configuration>();
     crafterBuildLib->path = "./";
     crafterBuildLib->name = "crafter.build-lib";
     crafterBuildLib->outputName = "crafter-build";
     crafterBuildLib->target = target;
+    crafterBuildLib->march = march;
+    crafterBuildLib->mtune = mtune;
     crafterBuildLib->type = ConfigurationType::LibraryStatic;
     crafterBuildLib->debug = debug;
     {
@@ -60,6 +71,8 @@ extern "C" Configuration CrafterBuildProject(std::span<const std::string_view> a
     cfg.name = "crafter.build-exe";
     cfg.outputName = "crafter-build";
     cfg.target = target;
+    cfg.march = march;
+    cfg.mtune = mtune;
     cfg.type = ConfigurationType::Executable;
     cfg.debug = debug;
     cfg.dependencies = { crafterBuildLib.get() };