diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
new file mode 100644
index 0000000..f7b518c
--- /dev/null
+++ b/.github/workflows/ci.yaml
@@ -0,0 +1,57 @@
+name: CI
+
+on:
+  pull_request:
+    branches: [master]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    services:
+      db:
+        image: postgres:15-alpine
+        env:
+          POSTGRES_DB: expedition_db
+          POSTGRES_USER: expedition_user
+          POSTGRES_PASSWORD: expedition_pass
+        ports:
+          - 5432:5432
+        options: >-
+          --health-cmd "pg_isready -U expedition_user -d expedition_db"
+          --health-interval 5s
+          --health-timeout 5s
+          --health-retries 5
+
+      redis:
+        image: redis:7-alpine
+        ports:
+          - 6379:6379
+        options: >-
+          --health-cmd "redis-cli ping"
+          --health-interval 5s
+          --health-timeout 5s
+          --health-retries 5
+
+    env:
+      DATABASE_URL: postgres://expedition_user:expedition_pass@localhost:5432/expedition_db
+      REDIS_URL: redis://localhost:6379
+      SECRET_KEY: test-secret-key
+      DEBUG: "True"
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+
+      - name: Install dependencies
+        run: pip install -r requirements.txt
+
+      - name: Run migrations
+        run: python manage.py migrate --noinput
+
+      - name: Run tests
+        run: pytest tests/
diff --git a/authentication/authentication.py b/authentication/authentication.py
index 5d1d6b2..0571dd6 100644
--- a/authentication/authentication.py
+++ b/authentication/authentication.py
@@ -8,6 +8,8 @@
 from .models import Session, User
 
 class SessionAuthentication(BaseAuthentication):
+    def authenticate_header(self, request):
+        return 'Bearer'
     def authenticate(self, request: HttpRequest):
         header = request.headers.get("Authorization")
         if not header:
diff --git a/tests/test_cycles.py b/tests/test_cycles.py
new file mode 100644
index 0000000..0c4d0f9
--- /dev/null
+++ b/tests/test_cycles.py
@@ -0,0 +1,19 @@
+import pytest
+import os
+from tools.check_cycles import CycleDetector
+
+PROJECT_ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), '..'))
+
+class TestDependencyCycles:
+    @pytest.fixture(autouse=True)
+    def setup(self):
+        self.cycle_detector = CycleDetector(PROJECT_ROOT)
+
+    def test_no_cycles_exist(self):
+        self.cycle_detector.add_directory('/expeditions/')
+        self.cycle_detector.add_directory('/authentication/')
+        cycles = self.cycle_detector.detect()
+        assert len(cycles) == 0, (
+            f"Circular dependencies detected:\n"
+            + "\n".join(" -> ".join(c) for c in cycles)
+        )
\ No newline at end of file
diff --git a/tools/__init__.py b/tools/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tools/check_cycles.py b/tools/check_cycles.py
new file mode 100644
index 0000000..28165b9
--- /dev/null
+++ b/tools/check_cycles.py
@@ -0,0 +1,73 @@
+import ast
+import os
+from collections import defaultdict
+
+
+class CycleDetector:
+    def __init__(self, root):
+        self._root = os.path.abspath(root)
+        self._dirs = set()
+
+    def add_directory(self, directory):
+        self._dirs.add(self._root+directory)
+
+    @staticmethod
+    def _find_imports(filepath):
+        with open(filepath, 'r') as f:
+            tree = ast.parse(f.read())
+
+        imports = []
+        for node in ast.walk(tree):
+            if isinstance(node, ast.Import):
+                for alias in node.names:
+                    imports.append(alias.name)
+            elif isinstance(node, ast.ImportFrom):
+                if node.module:
+                    imports.append(node.module)
+        return imports
+
+    @staticmethod
+    def _detect_cycles(graph):
+        visited = set()
+        in_stack = set()
+        cycles = []
+
+        def dfs(node, path):
+            visited.add(node)
+            in_stack.add(node)
+            path.append(node)
+
+            for neighbor in graph.get(node, []):
+                if neighbor not in visited:
+                    dfs(neighbor, path)
+                elif neighbor in in_stack:
+                    cycle_start = path.index(neighbor)
+                    cycles.append(path[cycle_start:] + [neighbor])
+
+            path.pop()
+            in_stack.remove(node)
+
+        for node in graph:
+            if node not in visited:
+                dfs(node, [])
+
+        return cycles
+
+    def _build_dependency_graph(self, project_path):
+        graph = defaultdict(set)
+
+        for root, dirs, files in os.walk(project_path):
+            for f in files:
+                if f.endswith('.py'):
+                    filepath = os.path.join(root, f)
+                    module = filepath.replace(self._root, '').replace('/', '.').replace('.py', '').lstrip('.')
+                    imports = self._find_imports(filepath)
+                    for imp in imports:
+                        graph[module].add(imp)
+        return graph
+
+    def detect(self):
+        graph = defaultdict(set)
+        for directory in self._dirs:
+            graph.update(self._build_dependency_graph(directory))
+        return self._detect_cycles(graph)
\ No newline at end of file