diff --git a/.gitea/workflows/build.yml b/.gitea/workflows/build.yml
index 25c17a424..5444ac31e 100644
--- a/.gitea/workflows/build.yml
+++ b/.gitea/workflows/build.yml
@@ -19,6 +19,11 @@ env:
   LLVM_VERSION: "16.0.0"
   VCPKG_COMMIT_ID: "120deac3062162151622ca4860575a33844ba10b"
   CARGO_BIN: 'C:\Users\Yowie\.cargo\bin'
+  # VCPKG_ROOT must be visible to cargo (magnum-opus + scrap build.rs read
+  # it directly via env::var). GITHUB_ENV from a previous step doesn't
+  # always propagate reliably under act_runner -- set at workflow level.
+  VCPKG_ROOT: 'C:\vcpkg'
+  LIBCLANG_PATH: 'C:\LLVM16\bin'
 
 jobs:
   build: