Claude Opus 4.5 returns "Internal server error" in response body via Anthropic OAuth (Sonnet works)

[KennReloaded]

Summary
Claude Opus 4.5 returns "Internal server error" via Anthropic OAuth. Sonnet 4.5 works with same credentials.

Response times show Anthropic rejects Opus immediately (~500ms) vs Sonnet processing normally (~12s):

Opus:   200 | 476ms  | thinking: budget=24576 → Internal server error
Sonnet: 200 | 12.76s | thinking: budget=32768 → Success

CLI Type
claude code (Anthropic OAuth)

Model Name
claude-opus-4-5-20251101

LLM Client
roo-code v3.41.3

Request Information
Debug logs with debug: true:

[15:13:35] [debug] Use OAuth provider=claude auth_file=claude-[redacted]@gmail.com.json for model claude-opus-4-5-20251101
[15:13:35] [debug] thinking: processed config to apply | provider=claude model=claude-opus-4-5-20251101 mode=budget budget=24576
[15:13:35] [info ] 200 | 476ms | POST "/v1/chat/completions"

Client receives: {"details": "Internal server error"}

Expected behavior
Opus 4.5 should work like Sonnet 4.5 with same OAuth credentials.

OS Type

• OS: Windows 10

Additional context

• CLIProxyAPI v6.7.28