diff --git a/pyproject.toml b/pyproject.toml
index c2f0dc6ced7..e3e103e6d49 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -112,12 +112,9 @@ utils = [
 ]
 caching = ["diskcache>=5.6.3,<6.0"]
 mcp = ["mcp>=1.28.1,<2.0"]
-# Driver for the MongoDB Atlas vector store. Atlas Vector Search has no HTTP query
-# API, so that provider talks to the cluster over the wire protocol. Imported lazily
-# and kept out of the base install, which never needs a MongoDB driver. The floor is
-# 4.17 because that is where dnspython became a core dependency rather than the `srv`
-# extra, and Atlas hands out mongodb+srv:// URIs that do not resolve without it.
-mongodb = ["pymongo>=4.17,<5.0"]
+# Driver for the MongoDB Atlas vector store; Atlas Vector Search has no HTTP query API.
+# The floor is 4.9 because that is the release AsyncMongoClient landed in.
+mongodb = ["pymongo>=4.9,<5.0"]
 # SAML SSO for the admin UI. python3-saml pulls in xmlsec/lxml, whose wheels
 # bundle the native libxmlsec1/libxml2 libraries, so no system packages are
 # required. Kept out of the base `proxy` extra so it stays optional.
diff --git a/uv.lock b/uv.lock
index 362bb490a2a..bb1927ce093 100644
--- a/uv.lock
+++ b/uv.lock
@@ -10,7 +10,7 @@ resolution-markers = [
 ]
 
 [options]
-exclude-newer = "2026-08-30T17:51:25.171404Z"
+exclude-newer = "2026-08-31T00:55:41.895302Z"
 exclude-newer-span = "P3D"
 
 [manifest]
@@ -4554,7 +4554,7 @@ requires-dist = [
     { name = "pydantic", specifier = ">=2.10.0,<3.0.0" },
     { name = "pydantic-settings", specifier = ">=2.14.1,<3.0" },
     { name = "pyjwt", marker = "extra == 'proxy'", specifier = ">=2.13.0,<3.0" },
-    { name = "pymongo", marker = "extra == 'mongodb'", specifier = ">=4.17,<5.0" },
+    { name = "pymongo", marker = "extra == 'mongodb'", specifier = ">=4.9,<5.0" },
     { name = "pynacl", marker = "extra == 'proxy'", specifier = ">=1.6.2,<2.0" },
     { name = "pypdf", marker = "extra == 'proxy-runtime'", specifier = ">=6.16.1,<7.0" },
     { name = "pyroscope-io", marker = "sys_platform != 'win32' and extra == 'proxy'", specifier = ">=0.8.16,<1.0" },