feat: add max reasoning tier for Sonnet 4.6 (#1257)

src/models.json

@@ -68,6 +68,19 @@
       "parallel_tool_calls": true
     }
   },
+  {
+    "id": "sonnet-4.6-xhigh",
+    "handle": "anthropic/claude-sonnet-4-6",
+    "label": "Sonnet 4.6",
+    "description": "Sonnet 4.6 (max reasoning)",
+    "updateArgs": {
+      "context_window": 200000,
+      "max_output_tokens": 128000,
+      "reasoning_effort": "xhigh",
+      "enable_reasoner": true,
+      "parallel_tool_calls": true
+    }
+  },
   {
     "id": "sonnet-4.5",
     "handle": "anthropic/claude-sonnet-4-5-20250929",

src/tests/model-tier-selection.test.ts

@@ -95,12 +95,14 @@ describe("getReasoningTierOptionsForHandle", () => {
       "low",
       "medium",
       "high",
+      "xhigh",
     ]);
     expect(options.map((option) => option.modelId)).toEqual([
       "sonnet-4.6-no-reasoning",
       "sonnet-4.6-low",
       "sonnet-4.6-medium",
       "sonnet",
+      "sonnet-4.6-xhigh",
     ]);
   });