diff --git a/pyproject.toml b/pyproject.toml
index 77ed85a..fd002d7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -7,7 +7,10 @@ name = "idea151-aidmesh-federated-privacy"
 version = "0.0.1"
 description = "Core primitives for AidMesh: federated, privacy-preserving disaster response orchestration"
 requires-python = ">=3.8"
-dynamic = ["readme", "license", "authors"]
+readme = "README.md"
+
+[tool.setuptools.packages.find]
+where = ["src"]
 
 [tool.setuptools]
-packages = ["idea151_aidmesh_federated_privacy"]
+package-dir = {"" = "src"}
diff --git a/tests/test_models.py b/tests/test_models.py
new file mode 100644
index 0000000..19d1866
--- /dev/null
+++ b/tests/test_models.py
@@ -0,0 +1,42 @@
+from __future__ import annotations
+
+import pytest
+
+from datetime import datetime
+
+from idea151_aidmesh_federated_privacy import models
+
+
+def test_models_to_dict_and_immutability():
+    lp = models.LocalProblem(
+        id="lp-1",
+        domain="shelter",
+        assets={"tents": 100},
+        objectives=["max_coverage"],
+        constraints={"max_deploy": 50},
+    )
+
+    sd = models.SharedSignals(
+        forecast={"demand": 120}, capacity_proxies={"depotA": 80}, privacy_budget=1.0, version=1
+    )
+
+    now = datetime.utcnow()
+    pd = models.PlanDelta(
+        delta={"alloc": {"depotA": 40}},
+        timestamp=now,
+        author="planner-1",
+        contract_id="c-123",
+        signature="sig",
+    )
+
+    al = models.AuditLog(entry="created", signer="alice", timestamp=now, contract_id="c-123", version=1)
+
+    # to_dict should produce serializable dicts and timestamp should be ISO string
+    assert lp.to_dict()["id"] == "lp-1"
+    assert sd.to_dict()["version"] == 1
+    assert isinstance(pd.to_dict()["timestamp"], str) and "T" in pd.to_dict()["timestamp"]
+    assert isinstance(al.to_dict()["timestamp"], str) and "T" in al.to_dict()["timestamp"]
+
+    # dataclasses are frozen: setting an attribute should raise
+    with pytest.raises(Exception):
+        lp.id = "other"