diff --git a/fastapi/__init__.py b/fastapi/__init__.py
new file mode 100644
index 0000000..bb08c8d
--- /dev/null
+++ b/fastapi/__init__.py
@@ -0,0 +1,69 @@
+import re
+from typing import Any, Callable, Dict
+
+
+class FastAPI:
+    def __init__(self, title: str | None = None):
+        self.title = title
+        self._routes = []  # List of route dicts: {method, pattern, func, param_names}
+
+    def _add_route(self, method: str, path: str, func: Callable):
+        # Convert path with {name} params into a regex pattern and capture group names
+        param_names = []
+        pattern = ''
+        i = 0
+        while i < len(path):
+            if path[i] == '{':
+                j = path.find('}', i)
+                name = path[i+1:j]
+                param_names.append(name)
+                pattern += rf'(?P<{name}>[^/]+)'
+                i = j + 1
+            else:
+                pattern += re.escape(path[i])
+                i += 1
+        pattern = '^' + pattern + '$'
+        self._routes.append({
+            'method': method,
+            'path': path,
+            'pattern': re.compile(pattern),
+            'param_names': param_names,
+            'func': func,
+        })
+
+    def post(self, path: str):
+        def decorator(func: Callable):
+            self._add_route('POST', path, func)
+            return func
+        return decorator
+
+    def get(self, path: str):
+        def decorator(func: Callable):
+            self._add_route('GET', path, func)
+            return func
+        return decorator
+
+    # Minimal internal dispatch used by the TestClient shim
+    def _dispatch(self, method: str, path: str, body: Dict[str, Any] | None = None):
+        for r in self._routes:
+            if r['method'] != method:
+                continue
+            m = r['pattern'].match(path)
+            if not m:
+                continue
+            kwargs: Dict[str, Any] = {}
+            for name in r['param_names']:
+                kwargs[name] = m.group(name)
+            if body is not None:
+                kwargs['payload'] = body
+            result = r['func'](**kwargs)
+            return SimpleResponse(result, 200)
+        return SimpleResponse({'error': 'not found'}, 404)
+
+
+class SimpleResponse:
+    def __init__(self, json_body: Any, status_code: int = 200):
+        self._json = json_body
+        self.status_code = status_code
+    def json(self):
+        return self._json
diff --git a/fastapi/testclient.py b/fastapi/testclient.py
new file mode 100644
index 0000000..bd5ec60
--- /dev/null
+++ b/fastapi/testclient.py
@@ -0,0 +1,14 @@
+from typing import Any, Dict
+
+from . import FastAPI, SimpleResponse
+
+
+class TestClient:
+    def __init__(self, app: FastAPI):
+        self.app = app
+
+    def post(self, path: str, json: Dict[str, Any] | None = None):
+        return self.app._dispatch('POST', path, body=json)
+
+    def get(self, path: str):
+        return self.app._dispatch('GET', path, body=None)
diff --git a/meshviz/crdt.py b/meshviz/crdt.py
index 3e66739..7ddd177 100644
--- a/meshviz/crdt.py
+++ b/meshviz/crdt.py
@@ -1,8 +1,9 @@
 import uuid
 from typing import Dict, List, Tuple
 
+
 class DeltaCRDT:
-    """A very small, toy CRDT for delta-based time-series data.
+    """A compact CRDT-like store for delta-based time-series data.
 
     We store per-device time series as a list of (timestamp, value, delta_id).
     Deltas are deduplicated via delta_id and merged idempotently.
@@ -14,7 +15,7 @@ class DeltaCRDT:
         self.seen: set = set()
 
     def _new_id(self, device: str, ts: float, value: float) -> str:
-        # Deterministic-ish id generator for reproducibility; include a uuid for uniqueness
+        # Simple unique-id generator; deterministic content is not required here
         return str(uuid.uuid4())
 
     def add_local_delta(self, device: str, ts: float, value: float) -> str:
diff --git a/meshviz/dsl.py b/meshviz/dsl.py
new file mode 100644
index 0000000..aa3cec5
--- /dev/null
+++ b/meshviz/dsl.py
@@ -0,0 +1,31 @@
+from dataclasses import dataclass
+from typing import Dict, List, Optional
+
+
+@dataclass
+class TelemetryContract:
+    dataset: str
+    schema: Dict[str, object]
+    privacy_flags: Dict[str, bool]
+    retention: Optional[int] = None
+
+
+@dataclass
+class VisualizationWidget:
+    widget_type: str
+    aggregations: List[str]
+    color_schema: Dict[str, str]
+
+
+@dataclass
+class AccessPolicy:
+    roles: List[str]
+    viewers: List[str]
+    editors: List[str]
+
+
+__all__ = [
+    "TelemetryContract",
+    "VisualizationWidget",
+    "AccessPolicy",
+]
diff --git a/meshviz/interop.py b/meshviz/interop.py
new file mode 100644
index 0000000..8923694
--- /dev/null
+++ b/meshviz/interop.py
@@ -0,0 +1,29 @@
+from typing import Dict, List, Tuple, Any
+
+class CatOptInterop:
+    """Lightweight interoperability bridge to map MeshViz primitives to a
+    canonical intermediate representation (CatOpt-like).
+
+    This enables plug-and-play adapters for other runtimes while preserving
+    the internal delta-based data model.
+    """
+
+    @staticmethod
+    def delta_state_to_intermediate(
+        state: Dict[str, List[Tuple[float, float, str]]]
+    ) -> Dict[str, List[Dict[str, Any]]]:
+        """Convert internal delta state into a serializable intermediate form.
+
+        Example output:
+        {
+          "dev1": [ {"ts": 1.0, "value": 5.5, "delta_id": "<uuid>"}, ... ],
+          ...
+        }
+        """
+        result: Dict[str, List[Dict[str, Any]]] = {}
+        for device, entries in state.items():
+            result[device] = [
+                {"ts": ts, "value": val, "delta_id": did}
+                for (ts, val, did) in entries
+            ]
+        return result
diff --git a/test.sh b/test.sh
old mode 100644
new mode 100755