feat(ai-chat): add grok-4.6 model to xai provider

- Add grok-4.6 model definition with pricing and context specs
- Add aliases x-ai/grok-4.6 and grok-4.6-latest
- Add unit tests for alias resolution and metering calculation

Closes #3562

src/backend/drivers/ai-chat/providers/xai/XAIProvider.test.ts

@@ -387,6 +387,42 @@ describe('XAIProvider model resolution', () => {
         );
     });
 
+    it('resolves grok-4.6 aliases to grok-4.6 with correct metering overrides', async () => {
+        const { provider } = makeProvider();
+        createMock.mockResolvedValueOnce({
+            choices: [
+                {
+                    message: { content: 'ok', role: 'assistant' },
+                    finish_reason: 'stop',
+                },
+            ],
+            usage: {
+                prompt_tokens: 1000,
+                completion_tokens: 500,
+                prompt_tokens_details: { cached_tokens: 200 },
+            },
+        });
+
+        await withTestActor(() =>
+            provider.complete({
+                model: 'grok-4.6-latest',
+                messages: [{ role: 'user', content: 'hi' }],
+            }),
+        );
+
+        expect(createMock.mock.calls[0]![0].model).toBe('grok-4.6');
+        expect(recordSpy).toHaveBeenCalledWith(
+            expect.any(Object),
+            expect.anything(),
+            'xai:grok-4.6',
+            {
+                prompt_tokens: 1000 * 200,
+                completion_tokens: 500 * 600,
+                cached_tokens: 200 * 50,
+            },
+        );
+    });
+
     it('falls back to the default model when given an unknown id', async () => {
         const { provider } = makeProvider();
         createMock.mockResolvedValueOnce(baseCompletion);

src/backend/drivers/ai-chat/providers/xai/models.ts

@@ -21,6 +21,28 @@ import type { IChatModel } from '../../types.js';
 
 // Hardcoded from https://models.dev/api.json
 export const XAI_MODELS: IChatModel[] = [
+    {
+        puterId: 'x-ai:x-ai/grok-4.6',
+        id: 'grok-4.6',
+        modalities: { input: ['text', 'image'], output: ['text'] },
+        open_weights: false,
+        tool_call: true,
+        knowledge: '2026-02',
+        release_date: '2026-08-12',
+        name: 'Grok 4.6',
+        aliases: ['x-ai/grok-4.6', 'grok-4.6-latest'],
+        context: 500_000,
+        costs_currency: 'usd-cents',
+        input_cost_key: 'prompt_tokens',
+        output_cost_key: 'completion_tokens',
+        costs: {
+            tokens: 1_000_000,
+            prompt_tokens: 200,
+            completion_tokens: 600,
+            cached_tokens: 50,
+        },
+        max_tokens: 30_000,
+    },
     {
         puterId: 'x-ai:x-ai/grok-4.5',
         id: 'grok-4.5',