diff --git a/.github/workflows/main-arm64.yml b/.github/workflows/main-arm64.yml
index 9b4810f..9d7f293 100644
--- a/.github/workflows/main-arm64.yml
+++ b/.github/workflows/main-arm64.yml
@@ -29,12 +29,12 @@ jobs:
           python -m venv venvs/cu12
           bash -c "source venvs/cu12/bin/activate && \
             pip install --upgrade pip -qq && \
-            pip install --pre --extra-index-url=https://pypi.nvidia.com cuopt-cu12==26.2.* -qq &&
+            pip install --timeout=150 --pre --extra-index-url=https://pypi.nvidia.com --extra-index-url=https://pypi.anaconda.org/rapidsai-wheels-nightly/simple/ cuopt-cu12==26.4.0a78 -qq &&
             deactivate"
           python -m venv venvs/cu13
           bash -c "source venvs/cu13/bin/activate && \
             pip install --upgrade pip -qq && \
-            pip install --pre --extra-index-url=https://pypi.nvidia.com cuopt-cu13==26.2.* -qq &&
+            pip install --timeout=150 --pre --extra-index-url=https://pypi.nvidia.com --extra-index-url=https://pypi.anaconda.org/rapidsai-wheels-nightly/simple/ cuopt-cu13==26.4.0a78 -qq &&
             deactivate"
 
       # Get GAMS (ARM64 version)
diff --git a/.github/workflows/main-x86_64.yml b/.github/workflows/main-x86_64.yml
index c2e625d..ab0de0a 100644
--- a/.github/workflows/main-x86_64.yml
+++ b/.github/workflows/main-x86_64.yml
@@ -12,7 +12,7 @@ jobs:
   build-link:
     runs-on: ubuntu-latest
     container:
-      image: python:3.12
+      image: python:3.13
 
     steps:
       - name: Checkout repository
@@ -22,6 +22,14 @@ jobs:
         run: |
           apt-get update && apt-get install -y patchelf curl unzip zip gcc
 
+      # Download custom cuOpt wheel artifact
+      - name: Download and extract cuopt-int64 wheel
+        run: |
+          curl -L -H "Authorization: Bearer ${{ secrets.GITHUB_TOKEN }}" \
+            https://api.github.com/repos/GAMS-dev/cuopt-int64/actions/artifacts/5869680145/zip \
+            --output cuopt-int64-wheel.zip
+          unzip -q cuopt-int64-wheel.zip -d cuopt_wheel_dir
+
       # Get CUDA runtimes via pip
       - name: Set up python virtual environments with NVIDIA dependencies for CUDA 12 and CUDA 13 (respectively)
         run: |
@@ -29,12 +37,13 @@ jobs:
           python -m venv venvs/cu12
           bash -c "source venvs/cu12/bin/activate && \
             pip install --upgrade pip -qq && \
-            pip install --pre --extra-index-url=https://pypi.nvidia.com cuopt-cu12==26.2.* -qq &&
+            pip install --timeout=150 --pre --extra-index-url=https://pypi.nvidia.com --extra-index-url=https://pypi.anaconda.org/rapidsai-wheels-nightly/simple/ cuopt-cu12==26.4.0a81 -qq &&
             deactivate"
           python -m venv venvs/cu13
           bash -c "source venvs/cu13/bin/activate && \
             pip install --upgrade pip -qq && \
-            pip install --pre --extra-index-url=https://pypi.nvidia.com cuopt-cu13==26.2.* -qq &&
+            pip install --timeout=150 --pre --extra-index-url=https://pypi.nvidia.com --extra-index-url=https://pypi.anaconda.org/rapidsai-wheels-nightly/simple/ cuopt-cu13==26.4.0a81 -qq &&
+            pip install --force-reinstall --no-deps cuopt_wheel_dir/*.whl --extra-index-url https://pypi.anaconda.org/rapidsai-wheels-nightly/simple/ --pre &&
             deactivate"
 
       # Get GAMS
diff --git a/gmscuopt.c b/gmscuopt.c
index 3be82bc..9f1594b 100644
--- a/gmscuopt.c
+++ b/gmscuopt.c
@@ -133,7 +133,7 @@ int main(int argc, char *argv[])
 
   cuopt_int_t num_variables = gmoN(gmo);
   cuopt_int_t num_constraints = gmoM(gmo);
-  cuopt_int_t nnz = gmoNZ(gmo);
+  int64_t nnz = gmoNZ64(gmo);
 
   cuopt_int_t* constraint_matrix_row_offsets=NULL;
   cuopt_int_t* constraint_matrix_column_indices=NULL;