diff --git a/src/memos/api/middleware/rate_limit.py b/src/memos/api/middleware/rate_limit.py
index c547378ca..72808a13d 100644
--- a/src/memos/api/middleware/rate_limit.py
+++ b/src/memos/api/middleware/rate_limit.py
@@ -57,8 +57,13 @@ def _get_client_key(request: Request) -> str:
 
     Uses API key if available, otherwise falls back to IP.
     """
-    # Try to get API key from header
+    # Try to get API key from header. Real clients send a Bearer scheme
+    # per RFC 6750 (``Authorization: Bearer krlk_<hex>``); we strip the
+    # scheme before the prefix check so keyed requests actually land on
+    # a per-key bucket (issue #2428).
     auth_header = request.headers.get("Authorization", "")
+    if auth_header.lower().startswith("bearer "):
+        auth_header = auth_header[len("bearer ") :].lstrip()
     if auth_header.startswith("krlk_"):
         # Use first 20 chars of key as identifier
         return f"ratelimit:key:{auth_header[:20]}"
diff --git a/tests/api/test_rate_limit_bearer.py b/tests/api/test_rate_limit_bearer.py
new file mode 100644
index 000000000..710346cf0
--- /dev/null
+++ b/tests/api/test_rate_limit_bearer.py
@@ -0,0 +1,78 @@
+"""Regression tests for issue #2428.
+
+``_get_client_key`` in ``src/memos/api/middleware/rate_limit.py`` checked
+whether ``request.headers['Authorization']`` started with ``krlk_`` — but
+real clients send ``Authorization: Bearer krlk_<hex>`` per RFC 6750, so
+the prefix check never matched and every request fell through to IP-based
+limiting. Behind a shared egress IP all keyed clients shared one bucket
+and the per-key rate-limit was dead code.
+
+The fix strips the ``Bearer `` scheme before testing the key prefix, so
+``Bearer krlk_<hex>`` correctly maps to ``ratelimit:key:<first 20 of the
+stripped key>``.
+"""
+
+from __future__ import annotations
+
+from types import SimpleNamespace
+
+from memos.api.middleware.rate_limit import _get_client_key
+
+
+def _fake_request(authorization: str | None, *, client_host: str = "10.0.0.1"):
+    headers: dict[str, str] = {}
+    if authorization is not None:
+        headers["Authorization"] = authorization
+    return SimpleNamespace(
+        headers=headers,
+        client=SimpleNamespace(host=client_host),
+    )
+
+
+class TestGetClientKey:
+    def test_bearer_krlk_key_uses_per_key_bucket(self):
+        body = "krlk_" + "a" * 64
+        request = _fake_request("Bearer " + body)
+        key = _get_client_key(request)
+        assert key == "ratelimit:key:" + body[:20]
+        assert "10.0.0.1" not in key
+
+    def test_bearer_krlk_key_first_twenty_chars_of_actual_key(self):
+        body = "krlk_" + "f" * 64
+        request = _fake_request("Bearer " + body)
+        key = _get_client_key(request)
+        assert key == "ratelimit:key:" + body[:20]
+
+    def test_lowercase_bearer_scheme(self):
+        # RFC 7235: the scheme name is case-insensitive. We normalise to
+        # lowercase before the prefix check.
+        body = "krlk_" + "b" * 64
+        request = _fake_request("bearer " + body)
+        key = _get_client_key(request)
+        assert key == "ratelimit:key:" + body[:20]
+
+    def test_bearer_with_non_key_token_falls_back_to_ip(self):
+        request = _fake_request("Bearer some-jwt-token")
+        key = _get_client_key(request)
+        assert key.startswith("ratelimit:ip:")
+        assert "10.0.0.1" in key
+
+    def test_missing_authorization_header_falls_back_to_ip(self):
+        request = _fake_request(None)
+        key = _get_client_key(request)
+        assert key.startswith("ratelimit:ip:")
+        assert "10.0.0.1" in key
+
+    def test_x_forwarded_for_header_preferred_over_ip(self):
+        request = _fake_request(None, client_host="203.0.113.1")
+        request.headers["X-Forwarded-For"] = "198.51.100.1, 10.0.0.1"
+        key = _get_client_key(request)
+        assert key == "ratelimit:ip:198.51.100.1"
+
+    def test_krlk_prefix_without_bearer_scheme_still_matches(self):
+        # Backwards compatibility: clients that sent a bare krlk_ header
+        # (before the Bearer scheme was added) must still match.
+        body = "krlk_" + "c" * 64
+        request = _fake_request(body)
+        key = _get_client_key(request)
+        assert key == "ratelimit:key:" + body[:20]