diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index 921b755..079d07d 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -50,10 +50,20 @@ jobs:
       - name: Install build dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install build setuptools-scm
+          pip install "build>=1.0" setuptools-scm
 
       - name: Build sdist
-        run: python -m build --sdist
+        run: |
+          python -m build --sdist
+          # Verify sdist filename uses underscores (PEP 625)
+          ls -la dist/
+          if ls dist/cfd-python-*.tar.gz 1> /dev/null 2>&1; then
+            echo "ERROR: sdist has hyphenated name, renaming..."
+            for f in dist/cfd-python-*.tar.gz; do
+              mv "$f" "${f/cfd-python/cfd_python}"
+            done
+          fi
+          ls -la dist/
 
       - name: Upload sdist
         uses: actions/upload-artifact@v4