diff --git a/.github/workflows/pr-tests.yml b/.github/workflows/pr-tests.yml
index 324115f..a8800fc 100644
--- a/.github/workflows/pr-tests.yml
+++ b/.github/workflows/pr-tests.yml
@@ -4,6 +4,7 @@ name: PR Tests
 # - Draft PRs: Fast tests only (no coverage) for rapid iteration
 # - Ready for Review: Full tests with coverage for quality assurance
 # - All subsequent commits: Continue with full coverage
+# - Pyomo tests run separately and don't block PRs
 
 on:
   pull_request:
@@ -11,7 +12,8 @@ on:
     types: [ opened, synchronize, reopened, ready_for_review, converted_to_draft ]
 
 jobs:
-  test:
+  test-scipy:
+    name: SciPy Tests
     runs-on: ubuntu-latest
     
     steps:
@@ -50,11 +52,11 @@ jobs:
     - name: Run tests
       run: |
         if [ "${{ steps.mode.outputs.mode }}" == "fast" ]; then
-          echo "⚡ Draft PR - fast tests only (no notebook tests)"
-          pytest tests/ -n auto -v -m "not notebook"
+          echo "Draft PR: Skipping notebook and pyomo tests for fast feedback"
+          pytest tests/ -n auto -v -m "not notebook and not pyomo"
         else
-          echo "🔍 Full PR - running tests with coverage report"
-          pytest tests/ -n auto -v -m "not notebook" --cov-report=xml:coverage.xml
+          echo "Ready PR: Running full scipy test suite (excluding notebook and pyomo)"
+          pytest tests/ -n auto -v -m "not notebook and not pyomo" --cov=lyopronto --cov-report=xml:coverage.xml
         fi
     
     - name: Upload coverage
@@ -66,3 +68,51 @@ jobs:
         name: pr-coverage
         fail_ci_if_error: false
         token: ${{ secrets.CODECOV_TOKEN }}
+
+  test-pyomo:
+    name: Pyomo Tests (Optional)
+    if: ${{ github.event.pull_request.draft == false }}
+    runs-on: ubuntu-latest
+    continue-on-error: true  # Pyomo tests are brittle, don't block PRs
+    
+    steps:
+    - uses: actions/checkout@v4
+    
+    - name: Read CI version config
+      id: versions
+      uses: mikefarah/yq@v4.44.1
+      with:
+        cmd: yq eval '.python-version' .github/ci-config/ci-versions.yml
+    
+    - name: Set up Python
+      uses: actions/setup-python@v5
+      with:
+        python-version: ${{ steps.versions.outputs.result }}
+        cache: 'pip'
+        cache-dependency-path: |
+          pyproject.toml
+    
+    - name: Install dependencies with optimization stack
+      run: |
+        python -m pip install --upgrade pip setuptools wheel
+        pip install .
+        pip install .[dev]
+        pip install pyomo idaes-pse
+        pip install -e . --no-build-isolation
+    
+    - name: Install IPOPT solver via IDAES
+      run: |
+        echo "Installing IPOPT solver via IDAES extensions"
+        idaes get-extensions --extra petsc
+    
+    - name: Run Pyomo tests
+      run: |
+        echo "Running Pyomo test suite (continue-on-error enabled)"
+        # Exit code 5 = no tests collected (pyomo tests added in later PRs)
+        pytest tests/ -n auto -v -m "pyomo" --cov=lyopronto --cov-report=term-missing || { rc=$?; [ $rc -eq 5 ] && echo "No pyomo-marked tests found yet (expected until PR #8)" && exit 0; exit $rc; }
+    
+    - name: Pyomo Test Summary
+      if: always()
+      run: |
+        echo "Pyomo tests completed"
+        echo "Failures here don't block PR merge"
diff --git a/.github/workflows/slow-tests.yml b/.github/workflows/slow-tests.yml
index e3f7d7e..20df2e0 100644
--- a/.github/workflows/slow-tests.yml
+++ b/.github/workflows/slow-tests.yml
@@ -17,6 +17,14 @@ on:
         options:
           - 'true'
           - 'false'
+      include_pyomo:
+        description: 'Include Pyomo tests (requires IPOPT)'
+        required: false
+        default: 'true'
+        type: choice
+        options:
+          - 'true'
+          - 'false'
 
 jobs:
   slow-tests:
@@ -43,18 +51,39 @@ jobs:
         python -m pip install --upgrade pip setuptools wheel
         pip install .
         pip install .[dev]
+        if [ "${{ inputs.include_pyomo }}" == "true" ]; then
+          pip install pyomo idaes-pse
+        fi
         pip install -e . --no-build-isolation
     
+    - name: Install IPOPT solver via IDAES (if Pyomo enabled)
+      if: inputs.include_pyomo == 'true'
+      run: |
+        echo "Installing IPOPT solver via IDAES extensions"
+        idaes get-extensions --extra petsc
+    
     - name: Run slow tests
+      env:
+        RUN_SLOW_TESTS: "1"
       run: |
+        # Helper: allow exit code 5 (no tests collected) to pass gracefully
+        run_pytest() { "$@" || { rc=$?; [ $rc -eq 5 ] && echo "No matching tests found (exit 5 is OK)" && return 0; return $rc; }; }
         if [ "${{ inputs.run_all }}" == "true" ]; then
-          echo "🔍 Running ALL tests (including slow optimization tests)"
-          echo "⏱️ This may take 30-40 minutes on CI"
-          pytest tests/ -n auto -v --cov=lyopronto --cov-report=xml --cov-report=term-missing
+          echo "Running ALL tests (including slow optimization tests)"
+          echo "This may take 30-40 minutes on CI"
+          if [ "${{ inputs.include_pyomo }}" == "true" ]; then
+            run_pytest pytest tests/ -n auto -v --cov=lyopronto --cov-report=xml --cov-report=term-missing
+          else
+            run_pytest pytest tests/ -n auto -v -m "not pyomo" --cov=lyopronto --cov-report=xml --cov-report=term-missing
+          fi
         else
-          echo "🐌 Running ONLY slow tests (marked with @pytest.mark.slow)"
-          echo "⏱️ This focuses on optimization tests that take minutes"
-          pytest tests/ -n auto -v -m "slow" --cov=lyopronto --cov-report=xml --cov-report=term-missing
+          echo "Running ONLY slow tests (marked with @pytest.mark.slow)"
+          echo "This focuses on optimization tests that take minutes"
+          if [ "${{ inputs.include_pyomo }}" == "true" ]; then
+            run_pytest pytest tests/ -n auto -v -m "slow" --cov=lyopronto --cov-report=xml --cov-report=term-missing
+          else
+            run_pytest pytest tests/ -n auto -v -m "slow and not pyomo" --cov=lyopronto --cov-report=xml --cov-report=term-missing
+          fi
         fi
     
     - name: Upload coverage
@@ -70,8 +99,8 @@ jobs:
       if: always()
       run: |
         if [ "${{ inputs.run_all }}" == "true" ]; then
-          echo "✅ Complete test suite finished"
+          echo "Complete test suite finished"
         else
-          echo "🐌 Slow tests completed"
+          echo "Slow tests completed"
         fi
-        echo "📊 Coverage uploaded to Codecov"
+        echo "Coverage uploaded to Codecov"
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index d7904b2..e3be451 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -1,14 +1,15 @@
 name: Main Branch Tests
 
 # Full tests with coverage for main branch
-# (PRs are handled by pr-tests.yml)
+# Runs both scipy tests and Pyomo tests in separate jobs
 
 on:
   push:
-    branches: [ main, dev-pyomo ]
+    branches: [ main ]
 
 jobs:
-  test:
+  test-scipy:
+    name: SciPy Tests
     runs-on: ubuntu-latest
     
     steps:
@@ -33,23 +34,77 @@ jobs:
         pip install .[dev]
         pip install -e . --no-build-isolation
     
-    - name: Run ALL tests with pytest and coverage (including slow tests)
+    - name: Run SciPy tests (excluding Pyomo tests)
       run: |
-        echo "🔍 Running complete test suite including slow tests"
-        echo "⏱️ This may take 30-40 minutes on CI (includes optimization tests)"
-        pytest tests/ -n auto -v --cov=lyopronto --cov-report=xml --cov-report=term-missing
+        echo "Running SciPy test suite (excluding Pyomo tests)"
+        pytest tests/ -n auto -v -m "not pyomo" --cov=lyopronto --cov-report=xml --cov-report=term-missing
     
     - name: Upload coverage to Codecov
       uses: codecov/codecov-action@v4
       with:
         file: ./coverage.xml
-        flags: unittests
-        name: codecov-umbrella
+        flags: scipy-tests
+        name: scipy-coverage
         fail_ci_if_error: false
         token: ${{ secrets.CODECOV_TOKEN }}
     
     - name: Coverage Summary
       if: always()
       run: |
-        echo "✅ Full coverage tests completed for main branch"
-        echo "📊 Coverage metrics updated in Codecov"
+        echo "SciPy tests completed for main branch"
+        echo "Coverage metrics updated in Codecov"
+
+  test-pyomo:
+    name: Pyomo Tests
+    runs-on: ubuntu-latest
+    continue-on-error: true  # Pyomo tests are brittle, don't block merges
+    
+    steps:
+    - uses: actions/checkout@v4
+    - name: Read CI version config
+      id: versions
+      uses: mikefarah/yq@v4.44.1
+      with:
+        cmd: yq eval '.python-version' .github/ci-config/ci-versions.yml
+    - name: Set up Python
+      uses: actions/setup-python@v5
+      with:
+        python-version: ${{ steps.versions.outputs.result }}
+        cache: 'pip'
+        cache-dependency-path: |
+          pyproject.toml
+    
+    - name: Install dependencies with optimization stack
+      run: |
+        python -m pip install --upgrade pip setuptools wheel
+        pip install .
+        pip install .[dev]
+        pip install pyomo idaes-pse
+        pip install -e . --no-build-isolation
+    
+    - name: Install IPOPT solver via IDAES
+      run: |
+        echo "Installing IPOPT solver via IDAES extensions"
+        idaes get-extensions --extra petsc
+    
+    - name: Run Pyomo tests
+      run: |
+        echo "Running Pyomo test suite"
+        echo "These tests require IPOPT solver and may be slower"
+        # Exit code 5 = no tests collected (pyomo tests added in later PRs)
+        pytest tests/ -n auto -v -m "pyomo" --cov=lyopronto --cov-report=xml --cov-report=term-missing || { rc=$?; [ $rc -eq 5 ] && echo "No pyomo-marked tests found yet (expected until PR #8)" && exit 0; exit $rc; }
+    
+    - name: Upload coverage to Codecov
+      uses: codecov/codecov-action@v4
+      with:
+        file: ./coverage.xml
+        flags: pyomo-tests
+        name: pyomo-coverage
+        fail_ci_if_error: false
+        token: ${{ secrets.CODECOV_TOKEN }}
+    
+    - name: Pyomo Test Summary
+      if: always()
+      run: |
+        echo "Pyomo tests completed (continue-on-error enabled)"
+        echo "Coverage metrics updated in Codecov"
diff --git a/pytest.ini b/pytest.ini
index 628d695..4cb86a4 100644
--- a/pytest.ini
+++ b/pytest.ini
@@ -17,6 +17,7 @@ addopts =
     --disable-warnings
     -n auto
     --maxfail=5
+    --dist loadgroup
 
 # Markers for organizing tests
 markers =
@@ -27,6 +28,9 @@ markers =
     parametric: Parametric tests across multiple scenarios
     fast: Quick tests that run in under 1 second
     main: Tests that cover functionality previously included in main.py
+    serial: Tests intended to be run serially; enforce with 'pytest -m serial -n 0'
+    pyomo: Tests requiring Pyomo and IPOPT solver (deselect with '-m not pyomo')
+    notebook: Tests that execute Jupyter notebooks for documentation
 
 # Minimum Python version
 minversion = 3.8