Use Opus 4.6 as default tokenizer for non-Claude models

Opus 4.7's tokenizer differs from most models; using 4.6 gives more
representative counts for open-source models routed through the
Anthropic count_tokens endpoint.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jahooma

common/src/constants/claude-oauth.ts

@@ -83,6 +83,7 @@ export const OPENROUTER_TO_ANTHROPIC_MODEL_MAP: Record<string, string> = {
 
   // Claude 4.x Opus models
   'anthropic/claude-opus-4.7': 'claude-opus-4-7',
+  'anthropic/claude-opus-4.6': 'claude-opus-4-6',
   'anthropic/claude-opus-4.5': 'claude-opus-4-5-20251101',
   'anthropic/claude-opus-4.1': 'claude-opus-4-1-20250805',
   'anthropic/claude-opus-4': 'claude-opus-4-1-20250805',

web/src/app/api/v1/token-count/_post.ts

@@ -32,7 +32,7 @@ const tokenCountRequestSchema = z.object({
 
 type TokenCountRequest = z.infer<typeof tokenCountRequestSchema>
 
-const DEFAULT_ANTHROPIC_MODEL = 'claude-opus-4-7'
+const DEFAULT_ANTHROPIC_MODEL = 'claude-opus-4-6'
 
 export async function postTokenCount(params: {
   req: NextRequest