diff --git a/.gitea/workflows/mcp-tests.yml b/.gitea/workflows/mcp-tests.yml
index 3d4b8db..5b122ae 100644
--- a/.gitea/workflows/mcp-tests.yml
+++ b/.gitea/workflows/mcp-tests.yml
@@ -31,5 +31,5 @@ jobs:
 
       - name: Run MCP lint/format/tests via nix-shell
         run: |
-          cd "${GITEA_WORKSPACE:-${GITHUB_WORKSPACE:-$PWD}}"
-          nix run .#mcp-tests
+          repo_root="$PWD"
+          MCP_TESTS_WORKDIR="$repo_root" nix run .#mcp-tests
diff --git a/parts/packages.nix b/parts/packages.nix
index 546763b..0025619 100644
--- a/parts/packages.nix
+++ b/parts/packages.nix
@@ -37,7 +37,9 @@
         ];
         text = ''
           start_dir="$PWD"
-          if [ -n "''${GITEA_WORKSPACE:-}" ]; then
+          if [ -n "''${MCP_TESTS_WORKDIR:-}" ]; then
+            cd "''${MCP_TESTS_WORKDIR}"
+          elif [ -n "''${GITEA_WORKSPACE:-}" ]; then
             cd "''${GITEA_WORKSPACE}"
           elif [ -n "''${GITHUB_WORKSPACE:-}" ]; then
             cd "''${GITHUB_WORKSPACE}"