diff --git a/fill_resistance/__init__.py b/fill_resistance/__init__.py
index e69de29..b3ca363 100644
--- a/fill_resistance/__init__.py
+++ b/fill_resistance/__init__.py
@@ -0,0 +1,7 @@
+"""Fill Resistance - DC resistance of copper zone fills and traces.
+
+__version__ is the runtime source of truth (metadata.json and
+pyproject.toml are not deployed with the plugin); a test keeps the
+three in sync.
+"""
+__version__ = "1.3.0"
diff --git a/fill_resistance/report.py b/fill_resistance/report.py
index e951c28..d889205 100644
--- a/fill_resistance/report.py
+++ b/fill_resistance/report.py
@@ -7,7 +7,7 @@ from pathlib import Path
 
 import numpy as np
 
-from . import config
+from . import __version__, config
 from .geometry import Problem, save_problem
 from .raster import RasterStack
 from .solver import Result
@@ -59,9 +59,10 @@ def write_summary(outdir: Path, problem: Problem, stack: RasterStack,
                   result: Result) -> Path:
     ny, nx = stack.shape2d
     info = result.solve_info
+    head = f"fill_resistance {__version__} summary"
     lines = [
-        "fill_resistance summary",
-        "=======================",
+        head,
+        "=" * len(head),
         f"board:             {problem.board_path}",
         f"net:               {problem.net_name}",
         f"test current:      {result.i_test:g} A",
diff --git a/tests/test_version.py b/tests/test_version.py
new file mode 100644
index 0000000..2edc54b
--- /dev/null
+++ b/tests/test_version.py
@@ -0,0 +1,33 @@
+"""fill_resistance.__version__ is the runtime source of the version:
+it must match the packaging metadata (which is not deployed with the
+plugin) and show up in summary.txt."""
+import json
+import re
+from pathlib import Path
+
+import fill_resistance
+from fill_resistance import raster, report, solver
+from tests.util import NM, strip_problem
+
+ROOT = Path(__file__).resolve().parent.parent
+
+
+def test_version_matches_packaging_metadata():
+    meta = json.loads((ROOT / "metadata.json").read_text(encoding="utf-8"))
+    assert meta["versions"][0]["version"] == fill_resistance.__version__
+
+    pyproject = (ROOT / "pyproject.toml").read_text(encoding="utf-8")
+    m = re.search(r'^version = "([^"]+)"', pyproject, re.M)
+    assert m is not None
+    assert m.group(1) == fill_resistance.__version__
+
+
+def test_summary_shows_version(tmp_path):
+    problem = strip_problem()
+    stack = raster.rasterize_stack(problem, 1.0 * NM)
+    e1, e2 = raster.electrode_masks(stack, problem)
+    result = solver.run_solve(problem, stack, e1, e2, 1.0,
+                              contact_model="equipotential")
+    text = report.write_summary(tmp_path, problem, stack,
+                                result).read_text(encoding="utf-8")
+    assert fill_resistance.__version__ in text.splitlines()[0]