diff --git a/headroom/providers/anthropic.py b/headroom/providers/anthropic.py
index 56a8d0790..107fc53c5 100644
--- a/headroom/providers/anthropic.py
+++ b/headroom/providers/anthropic.py
@@ -59,9 +59,7 @@ _DANGLING_ANSI_STYLE_SUFFIX_RE = re.compile(r"(?:\[[0-9;]*m\])+$")
 def sanitize_anthropic_model_id(model: str) -> str:
     """Return an Anthropic model id without terminal styling artifacts."""
     cleaned = _ANSI_ESCAPE_RE.sub("", str(model)).strip()
-    if cleaned.startswith("claude-"):
-        cleaned = _DANGLING_ANSI_STYLE_SUFFIX_RE.sub("", cleaned)
-    return cleaned
+    return _DANGLING_ANSI_STYLE_SUFFIX_RE.sub("", cleaned)
 
 
 def sanitize_anthropic_model_metadata(value: Any) -> Any:
diff --git a/tests/test_providers/test_anthropic.py b/tests/test_providers/test_anthropic.py
index cbaf2accc..63fa1f73f 100644
--- a/tests/test_providers/test_anthropic.py
+++ b/tests/test_providers/test_anthropic.py
@@ -13,6 +13,7 @@ class TestAnthropicModelSanitization:
         from headroom.providers.anthropic import sanitize_anthropic_model_id
 
         assert sanitize_anthropic_model_id("claude-opus-4-8[1m]") == "claude-opus-4-8"
+        assert sanitize_anthropic_model_id("glm-5.2[1m]") == "glm-5.2"
 
     def test_sanitize_model_metadata_cleans_nested_model_ids(self):
         from headroom.providers.anthropic import sanitize_anthropic_model_metadata
diff --git a/tests/test_proxy_anthropic_model_sanitization.py b/tests/test_proxy_anthropic_model_sanitization.py
new file mode 100644
index 000000000..80880cab6
--- /dev/null
+++ b/tests/test_proxy_anthropic_model_sanitization.py
@@ -0,0 +1,77 @@
+from __future__ import annotations
+
+from typing import Any
+
+import httpx
+import pytest
+
+pytest.importorskip("fastapi")
+
+from fastapi.testclient import TestClient
+
+from headroom.proxy.server import ProxyConfig, create_app
+
+
+def test_anthropic_messages_strips_local_1m_model_suffix_before_forwarding() -> None:
+    config = ProxyConfig(
+        optimize=False,
+        cache_enabled=False,
+        rate_limit_enabled=False,
+        cost_tracking_enabled=False,
+        log_requests=False,
+        ccr_inject_tool=False,
+        ccr_handle_responses=False,
+        ccr_context_tracking=False,
+        image_optimize=False,
+    )
+    app = create_app(config)
+    client = TestClient(app)
+
+    captured: dict[str, Any] = {}
+
+    async def _fake_retry(
+        method: str,  # noqa: ARG001
+        url: str,  # noqa: ARG001
+        headers: dict[str, str],  # noqa: ARG001
+        body: dict[str, Any],
+        body_mutated: bool,
+        mutation_reasons: list[str],
+        **kwargs: Any,
+    ) -> httpx.Response:
+        captured["body"] = dict(body)
+        captured["body_mutated"] = body_mutated
+        captured["mutation_reasons"] = list(mutation_reasons)
+        return httpx.Response(
+            200,
+            json={
+                "id": "msg_glm_1m",
+                "type": "message",
+                "role": "assistant",
+                "model": body["model"],
+                "content": [{"type": "text", "text": "ok"}],
+                "usage": {
+                    "input_tokens": 10,
+                    "output_tokens": 1,
+                    "cache_read_input_tokens": 0,
+                    "cache_creation_input_tokens": 0,
+                },
+            },
+        )
+
+    app.state.proxy._retry_request = _fake_retry  # type: ignore[assignment]
+
+    response = client.post(
+        "/v1/messages",
+        headers={"x-api-key": "test-key", "anthropic-version": "2023-06-01"},
+        json={
+            "model": "glm-5.2[1m]",
+            "max_tokens": 10,
+            "stream": False,
+            "messages": [{"role": "user", "content": "2+2"}],
+        },
+    )
+
+    assert response.status_code == 200, response.text
+    assert captured["body"]["model"] == "glm-5.2"
+    assert captured["body_mutated"] is True
+    assert captured["mutation_reasons"] == ["sanitize_model_id"]