Opus 5 Issues - or maybe its just me?

[superdooper86]

Written by AI. Sorry

Is it a request payload issue?
[x] Yes, this is a request payload issue. I am using a client/cURL to send a request payload, but I received an unexpected error.
[ ] No, it's another issue.

If it's a request payload issue, you MUST know
Request is accepted (HTTP 200), but the effective model behavior is wrong. Curl payload and observed results are included below.

Describe the bug
Requesting claude-opus-5 through CLIProxyAPI Claude OAuth (cloak enabled) does not behave like real Claude Opus 5.

Control: official Claude Code on the same machine/account class correctly behaves as Opus 5 and reports knowledge cutoff May 2026.

Via CLIProxyAPI, the same style of prompt against claude-opus-5 behaves like an older model:

• self-identifies as Claude Opus 4.5
• reports knowledge cutoff as early 2025 / ~March 2025
• weaker/staler knowledge than Claude Code on the same prompt

This reproduces on:

• release v7.2.98
• current dev build 46172dd4

Cloak is enabled (disable-claude-cloak-mode: false). Disabling cloak is not a usable workaround (aggressive 429s).

CLI Type
Claude Code OAuth

Model Name
claude-opus-5

LLM Client

• CLIProxyAPI Anthropic-compatible /v1/messages
• control comparison: official Claude Code CLI 2.1.219

Request Information
curl http://127.0.0.1:8317/v1/messages
-H "x-api-key: $CLIPROXY_API_KEY"
-H "anthropic-version: 2023-06-01"
-H "content-type: application/json"
-d '{
"model": "claude-opus-5",
"max_tokens": 64000,
"stream": false,
"thinking": { "type": "adaptive" },
"output_config": { "effort": "high" },
"messages": [
{
"role": "user",
"content": "what exact model are you, and what is your knowledge cut off."
}
]
}'

Observed via CLIProxyAPI (cloak ON):

• response is successful
• response model field remains claude-opus-5
• content effectively says:
  • Claude Opus 4.5
  • knowledge cutoff early 2025 / around March 2025

Control via Claude Code CLI:

• real Opus 5 behavior
• knowledge cutoff May 2026

Notes:

• /v1/models lists claude-opus-5
• request shape matches current Anthropic Opus 5 usage (thinking adaptive + output_config.effort)

Expected behavior
model: "claude-opus-5" through Claude OAuth + cloak should route to real Claude Opus 5 and match Claude Code behavior/knowledge for the same account class (including May 2026 cutoff packaging), not behave like Opus 4.5 / early-2025.

Screenshots
N/A

OS Type

• OS: macOS
• Version: 27.0 (Build 26A5388g), arm64
• CLIProxyAPI: dev-46172dd4 (also reproduced on v7.2.98)
• Claude Code: 2.1.219

Additional context

• Proxy config:
  • host: 127.0.0.1
  • port: 8317
  • disable-claude-cloak-mode: false
• This appears to be upstream model routing / OAuth serving for claude-opus-5, not just a client display-label issue.
• Claude Code may self-report a packaged id variant, but plain claude-opus-5 should already be full Opus 5. The bug is that CLIProxy’s claude-opus-5 path does not behave like real Opus 5.

[miroblog]

same...
needs updating beta headers/ cch signature?

[L0g0ff]

I have an working Opus-5 with hermes now (2 commits).

It is vibe code project so I don't do a PR to CLIProxyAPI upstream. Feel free to borrow the information you need.

https://github.com/L0g0ff/CLIProxyAPI/commits/main/