diff --git a/app/main.py b/app/main.py
index c6a6ad1..bae5678 100644
--- a/app/main.py
+++ b/app/main.py
@@ -79,19 +79,48 @@ async def get_current_user(user: User = Depends(current_active_user)):
 # OAuth endpoints use GET instead of POST
 _OAUTH_PATHS = {"/auth/google/authorize", "/auth/google/callback"}
 
+# Global default for every other route, matching the per-client-IP keying of
+# the auth limits. Enforced here in-house (limits via limiter._limiter)
+# rather than through slowapi's SlowAPIMiddleware, whose default_limits
+# enforcement FastAPI >=0.137 breaks for routes mounted via include_router
+# (slowapi issue #281).
+_DEFAULT_RATE_LIMIT: RateLimitItem = parse("300/minute")
+
+# Infrastructure paths that must never 429: probes, docs, and the security
+# contact file.
+_RATE_LIMIT_EXEMPT_PATHS = {
+    "/",
+    "/health",
+    "/docs",
+    "/openapi.json",
+    "/.well-known/security.txt",
+}
+
 
 @app.middleware("http")
-async def rate_limit_auth(request: Request, call_next) -> Response:
-    """Apply rate limits to auth endpoints."""
-    rate_limit = _AUTH_RATE_LIMITS.get(request.url.path)
-    is_oauth = request.url.path in _OAUTH_PATHS
-    if rate_limit and (request.method == "POST" or is_oauth):
+async def rate_limit(request: Request, call_next) -> Response:
+    """Apply rate limits.
+
+    Auth endpoints get their strict per-path limits; every other route gets
+    the global default except the exempt infrastructure paths. A request
+    that consumed an auth limit does not also consume the default bucket.
+    """
+    path = request.url.path
+    auth_limit = _AUTH_RATE_LIMITS.get(path)
+    is_oauth = path in _OAUTH_PATHS
+    if auth_limit and (request.method == "POST" or is_oauth):
+        rate_limit_item: RateLimitItem | None = auth_limit
+    elif path in _RATE_LIMIT_EXEMPT_PATHS:
+        rate_limit_item = None
+    else:
+        rate_limit_item = _DEFAULT_RATE_LIMIT
+    if rate_limit_item is not None:
         key = get_remote_address(request)
-        if not limiter._limiter.hit(rate_limit, key):
+        if not limiter._limiter.hit(rate_limit_item, key):
             log_security_event(
                 SecurityEvent.RATE_LIMIT_HIT,
                 request=request,
-                detail=f"path={request.url.path}",
+                detail=f"path={path}",
             )
             return JSONResponse(
                 status_code=429,
diff --git a/tests/conftest.py b/tests/conftest.py
index 7e56b48..ac417c2 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -17,6 +17,17 @@
 async_session_maker = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
 
 
+@pytest.fixture(autouse=True)
+def reset_rate_limiter():
+    """Clear rate-limit buckets between tests so request counts don't leak
+    across tests (the limiter storage is process-global)."""
+    from app.main import limiter
+
+    limiter._storage.reset()
+    yield
+    limiter._storage.reset()
+
+
 @pytest.fixture(autouse=True)
 async def setup_database():
     """Create tables before each test, drop after."""
diff --git a/tests/test_rate_limiting.py b/tests/test_rate_limiting.py
new file mode 100644
index 0000000..5fd3669
--- /dev/null
+++ b/tests/test_rate_limiting.py
@@ -0,0 +1,29 @@
+"""Global rate limiting behaviour.
+
+Every route outside the exempt infrastructure set gets the in-house
+300/min default (auth endpoints keep their stricter per-path limits).
+The default is enforced by our own middleware calling `limits` directly,
+so it is immune to the FastAPI >=0.137 / slowapi issue #281 regression
+that breaks SlowAPIMiddleware-based default_limits.
+"""
+
+from httpx import AsyncClient
+
+
+class TestGlobalRateLimit:
+    async def test_default_limit_applies_to_non_auth_routes(self, client: AsyncClient):
+        # /collections is an ordinary API route with no per-path limit, so
+        # it gets the 300/min default (matches _DEFAULT_RATE_LIMIT in
+        # app/main.py — bump both together if that changes). The limit is
+        # consumed regardless of auth outcome, so unauthenticated traffic
+        # cannot hammer the route either.
+        for _ in range(300):
+            assert (await client.get("/collections")).status_code != 429
+        assert (await client.get("/collections")).status_code == 429
+
+    async def test_infrastructure_routes_are_exempt(self, client: AsyncClient):
+        # / and /health must never 429 — probes and uptime checks hit them
+        # far more often than any human client.
+        for _ in range(310):
+            assert (await client.get("/health")).status_code == 200
+        assert (await client.get("/")).status_code == 200