diff --git a/agent_core/__init__.py b/agent_core/__init__.py
index bf0eddf..ffd607b 100644
--- a/agent_core/__init__.py
+++ b/agent_core/__init__.py
@@ -2,4 +2,4 @@
 
 from __future__ import annotations
 
-__version__ = "0.1.0"
+__version__ = "0.4.0"
diff --git a/agent_core/collector/app.py b/agent_core/collector/app.py
index 6776b05..15d1c60 100644
--- a/agent_core/collector/app.py
+++ b/agent_core/collector/app.py
@@ -8,10 +8,11 @@
 
 from collections.abc import AsyncIterator
 from contextlib import asynccontextmanager
+from importlib.metadata import PackageNotFoundError, version
 from typing import Any
 
-from fastapi import FastAPI
-from sqlalchemy import select
+from fastapi import FastAPI, HTTPException
+from sqlalchemy import select, text
 
 from agent_core.collector.db import (
     TraceEventRow,
@@ -23,6 +24,15 @@
 from agent_core.contracts.tracing import TraceEvent
 
 
+def _package_version() -> str:
+    try:
+        return version("agent-core")
+    except PackageNotFoundError:
+        from agent_core import __version__
+
+        return __version__
+
+
 def _row_from_event(event: TraceEvent) -> TraceEventRow:
     cost = event.cost
     return TraceEventRow(
@@ -57,10 +67,16 @@ async def lifespan(_: FastAPI) -> AsyncIterator[None]:
         yield
         await engine.dispose()
 
-    app = FastAPI(title="agent-core trace collector", version="0.2.0", lifespan=lifespan)
+    app = FastAPI(title="agent-core trace collector", version=_package_version(), lifespan=lifespan)
+    app.state.collector_sessionmaker = sessionmaker
 
     @app.get("/healthz")
     async def healthz() -> dict[str, str]:
+        try:
+            async with app.state.collector_sessionmaker() as session:
+                await session.execute(text("SELECT 1"))
+        except Exception as exc:
+            raise HTTPException(status_code=503, detail="database unavailable") from exc
         return {"status": "ok"}
 
     @app.post("/v1/trace")
diff --git a/pyproject.toml b/pyproject.toml
index 07e3a53..8f3eb48 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "agent-core"
-version = "0.3.0"
+version = "0.4.0"
 description = "Shared typed contracts for the AS215932 Agent Runtime Framework (Phase 1 / §31 safe milestone)."
 requires-python = ">=3.11"
 dependencies = ["pydantic>=2,<3"]
@@ -16,6 +16,12 @@ dev = [
     "fastapi>=0.110", "uvicorn>=0.29", "sqlalchemy>=2", "httpx>=0.27", "aiosqlite>=0.20",
 ]
 
+[dependency-groups]
+dev = [
+    "pytest>=8", "pyyaml>=6", "ruff>=0.5", "mypy>=1.8", "types-PyYAML",
+    "fastapi>=0.110", "uvicorn>=0.29", "sqlalchemy>=2", "httpx>=0.27", "aiosqlite>=0.20",
+]
+
 [tool.hatch.build.targets.wheel]
 packages = ["agent_core"]
 
diff --git a/tests/collector/test_collector.py b/tests/collector/test_collector.py
index 6b4aacc..f76b1da 100644
--- a/tests/collector/test_collector.py
+++ b/tests/collector/test_collector.py
@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+from types import TracebackType
+
 from fastapi.testclient import TestClient
 
 from agent_core.collector.app import create_app
@@ -14,6 +16,27 @@ def test_healthz(tmp_path) -> None:
         assert client.get("/healthz").json() == {"status": "ok"}
 
 
+def test_healthz_checks_database_connectivity(tmp_path) -> None:
+    class BrokenSession:
+        async def __aenter__(self) -> BrokenSession:
+            raise RuntimeError("database down")
+
+        async def __aexit__(
+            self,
+            exc_type: type[BaseException] | None,
+            exc: BaseException | None,
+            tb: TracebackType | None,
+        ) -> None:
+            return None
+
+    app = _app(tmp_path)
+    app.state.collector_sessionmaker = lambda: BrokenSession()
+    with TestClient(app) as client:
+        response = client.get("/healthz")
+        assert response.status_code == 503
+        assert response.json() == {"detail": "database unavailable"}
+
+
 def test_ingest_and_read(tmp_path) -> None:
     event = {
         "event_type": "model_call",