diff --git a/hermes_cli/model_normalize.py b/hermes_cli/model_normalize.py
index 8c4a31b25d2..c2865b0364b 100644
--- a/hermes_cli/model_normalize.py
+++ b/hermes_cli/model_normalize.py
@@ -245,6 +245,14 @@ def _strip_matching_provider_prefix(model_name: str, target_provider: str) -> st
     This prevents arbitrary slash-bearing model IDs from being mangled on
     native providers while still repairing manual config values like
     ``zai/glm-5.1`` for the ``zai`` provider.
+
+    ``custom`` is a generic bucket for arbitrary user-defined endpoints, not
+    a vendor identity like ``zai``/``gemini``/``xai``. An alias that merely
+    *resolves to* ``custom`` (e.g. ``ollama``, via ``_PROVIDER_ALIASES``)
+    does not mean a ``ollama/`` prefix is redundant -- it may be the actual
+    routing prefix a proxy in front of the custom endpoint (e.g. LiteLLM)
+    requires, as in ``ollama/glm-5.2``. Only a literal ``custom/`` prefix --
+    the bucket's own name -- is treated as redundant here.
     """
     if "/" not in model_name:
         return model_name
@@ -253,8 +261,13 @@ def _strip_matching_provider_prefix(model_name: str, target_provider: str) -> st
     if not prefix.strip() or not remainder.strip():
         return model_name
 
-    normalized_prefix = _normalize_provider_alias(prefix)
     normalized_target = _normalize_provider_alias(target_provider)
+    if normalized_target == "custom":
+        if prefix.strip().lower() == "custom":
+            return remainder.strip()
+        return model_name
+
+    normalized_prefix = _normalize_provider_alias(prefix)
     if normalized_prefix and normalized_prefix == normalized_target:
         return remainder.strip()
     return model_name
diff --git a/tests/hermes_cli/test_model_normalize.py b/tests/hermes_cli/test_model_normalize.py
index 564c188e96e..a11389aef1d 100644
--- a/tests/hermes_cli/test_model_normalize.py
+++ b/tests/hermes_cli/test_model_normalize.py
@@ -182,6 +182,27 @@ class TestIssue6211NativeProviderPrefixNormalization:
         assert normalize_model_for_provider(model, target_provider) == expected
 
 
+class TestCustomProviderIsNotAVendorIdentity:
+    """``custom`` is a generic bucket, not a vendor -- an alias that merely
+    *resolves to* ``custom`` (e.g. ``ollama`` -> ``custom`` in
+    ``_PROVIDER_ALIASES``) must not be treated as a redundant prefix the
+    way ``zai/``, ``gemini/``, etc. are for their own native providers.
+
+    Regression for: a named custom provider (e.g. a LiteLLM proxy fronting
+    Ollama) registers its own routing name as ``ollama/glm-5.2``. Stripping
+    the ``ollama/`` prefix because it happens to alias to ``custom``
+    produced a bare ``glm-5.2`` the proxy doesn't recognise.
+    """
+
+    @pytest.mark.parametrize("model,expected", [
+        ("ollama/glm-5.2", "ollama/glm-5.2"),
+        ("ollama/llama3.2", "ollama/llama3.2"),
+        ("custom/some-model", "some-model"),
+    ])
+    def test_only_literal_custom_prefix_is_stripped(self, model, expected):
+        assert normalize_model_for_provider(model, "custom") == expected
+
+
 # ── detect_vendor ──────────────────────────────────────────────────────
 
 class TestDetectVendor: