diff --git a/.github/workflows/ubuntu.yml b/.github/workflows/ubuntu.yml
index efce0957..068b2060 100644
--- a/.github/workflows/ubuntu.yml
+++ b/.github/workflows/ubuntu.yml
@@ -103,7 +103,30 @@ jobs:
         SEMBA_FDTD_ENABLE_MPI: ${{ matrix.mpi }}
         SEMBA_FDTD_ENABLE_MTLN: ${{ matrix.mtln }}
         SEMBA_FDTD_ENABLE_HDF: ${{ matrix.hdf }}
+        SEMBA_FDTD_ENABLE_OUTPUT_MODULE: ${{ matrix.new-output-module }}
       run: python -m pytest test/ --durations=20
+
+    - name: Build legacy observation executable
+      if: matrix.new-output-module=='ON' && matrix.mpi=='OFF'
+      run: |
+        cmake -S . -B build-legacy \
+          -DCMAKE_BUILD_TYPE=${{matrix.build-type}} \
+          -DSEMBA_FDTD_ENABLE_MPI=${{matrix.mpi}} \
+          -DSEMBA_FDTD_ENABLE_HDF=${{matrix.hdf}} \
+          -DSEMBA_FDTD_ENABLE_MTLN=${{matrix.mtln}} \
+          -DSEMBA_FDTD_ENABLE_DOUBLE_PRECISION=${{matrix.double-precision}} \
+          -DSEMBA_FDTD_ENABLE_OUTPUT_MODULE=OFF
+        cmake --build build-legacy -j
+
+    - name: Run python output equivalence tests
+      if: matrix.new-output-module=='ON' && matrix.mpi=='OFF'
+      env:
+        SEMBA_FDTD_ENABLE_MPI: ${{ matrix.mpi }}
+        SEMBA_FDTD_ENABLE_MTLN: ${{ matrix.mtln }}
+        SEMBA_FDTD_ENABLE_HDF: ${{ matrix.hdf }}
+        SEMBA_FDTD_ENABLE_OUTPUT_MODULE: ${{ matrix.new-output-module }}
+        SEMBA_LEGACY_EXE: ${{ github.workspace }}/build-legacy/bin/semba-fdtd
+      run: python -m pytest test/pyWrapper/test_output_module_equivalence.py --durations=20
         
        
       
diff --git a/test/pyWrapper/test_output_module_equivalence.py b/test/pyWrapper/test_output_module_equivalence.py
new file mode 100644
index 00000000..b988d1cc
--- /dev/null
+++ b/test/pyWrapper/test_output_module_equivalence.py
@@ -0,0 +1,77 @@
+from utils import *
+
+
+legacy_exe = os.getenv(
+    "SEMBA_LEGACY_EXE",
+    os.path.join(os.getcwd(), "build-legacy", "bin", "semba-fdtd"),
+)
+
+missing_legacy_exe_skip = pytest.mark.skipif(
+    not os.path.isfile(legacy_exe),
+    reason="Legacy executable not found. Set SEMBA_LEGACY_EXE or build build-legacy/bin/semba-fdtd",
+)
+
+
+def _run_solver(case_file, exe_path, run_dir):
+    solver = FDTD(input_filename=case_file, path_to_exe=exe_path, run_in_folder=run_dir)
+    solver.run()
+    return solver
+
+
+def _assert_probe_columns_equal(probe_legacy, probe_new, columns, atol=1e-8, rtol=1e-5):
+    legacy_time = probe_legacy["time"].to_numpy()
+    new_time = probe_new["time"].to_numpy()
+
+    for col in columns:
+        new_vals = np.interp(new_time, legacy_time, probe_legacy[col].to_numpy())
+        assert np.allclose(new_vals, probe_new[col].to_numpy(), atol=atol, rtol=rtol)
+
+
+def _compare_case_probes(case_file, probe_names, columns_by_probe, tmp_path):
+    legacy_dir = tmp_path / "legacy"
+    new_dir = tmp_path / "new"
+    legacy_dir.mkdir()
+    new_dir.mkdir()
+
+    solver_legacy = _run_solver(case_file, legacy_exe, legacy_dir)
+    solver_new = _run_solver(case_file, SEMBA_EXE, new_dir)
+
+    for probe_name in probe_names:
+        legacy_probe = Probe(solver_legacy.getSolvedProbeFilenames(probe_name)[0])
+        new_probe = Probe(solver_new.getSolvedProbeFilenames(probe_name)[0])
+        _assert_probe_columns_equal(
+            legacy_probe,
+            new_probe,
+            columns_by_probe[probe_name],
+        )
+
+
+@missing_legacy_exe_skip
+def test_point_probe_output_equivalence_planewave_in_box(tmp_path):
+    case_file = CASES_FOLDER + "planewave/pw-in-box.fdtd.json"
+    _compare_case_probes(
+        case_file=case_file,
+        probe_names=["before", "inbox", "after"],
+        columns_by_probe={
+            "before": ["field"],
+            "inbox": ["field", "incident"],
+            "after": ["field"],
+        },
+        tmp_path=tmp_path,
+    )
+
+
+@mtln_skip
+@missing_legacy_exe_skip
+def test_wire_probe_output_equivalence_towel_hanger(tmp_path):
+    case_file = CASES_FOLDER + "towelHanger/towelHanger.fdtd.json"
+    _compare_case_probes(
+        case_file=case_file,
+        probe_names=["wire_start", "wire_mid", "wire_end"],
+        columns_by_probe={
+            "wire_start": ["current_0"],
+            "wire_mid": ["current_0"],
+            "wire_end": ["current_0"],
+        },
+        tmp_path=tmp_path,
+    )