fix(volcengine-ark): clamp GLM-5 max_tokens to model output ceiling (#2428)

Ark rejects max_tokens above 128000 for GLM-5.2. Add a config-driven STRIP_RULES entry that clamps max_tokens, max_completion_tokens and max_output_tokens down to the model maxOutput before the upstream call.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/unit/param-support.test.js

@@ -28,4 +28,28 @@ describe("stripUnsupportedParams", () => {
 
     expect(body).toEqual({ top_p: 1 });
   });
+
+  it("clamps VolcEngine Ark GLM max token fields to the model output ceiling", () => {
+    const body = {
+      max_tokens: 131072,
+      max_completion_tokens: 131072,
+      max_output_tokens: 131072,
+    };
+
+    stripUnsupportedParams("volcengine-ark", "GLM-5.2", body);
+
+    expect(body).toEqual({
+      max_tokens: 128000,
+      max_completion_tokens: 128000,
+      max_output_tokens: 128000,
+    });
+  });
+
+  it("keeps VolcEngine Ark GLM max tokens when already under the ceiling", () => {
+    const body = { max_tokens: 64000 };
+
+    stripUnsupportedParams("volcengine-ark", "GLM-5.2", body);
+
+    expect(body.max_tokens).toBe(64000);
+  });
 });