[BUG] How to use Anthropic after Claude code move

[yunhailuo]

Problem (one or two sentences)

I've been using Anthropic provider and something seem to change recently and it stopped working. I suspect this might be related to Claude code removal so the title. I've been using this API with Claude code using ANTHROPIC_BASE_URL and ANTHROPIC_CUSTOM_HEADERS and it's still working fine.

Context (who is affected and when)

I've been seeing this error since 1/23/2026 when using Anthropic provider and chat with message like "hello"

Reproduction steps

...
        "apiConfigs": {
            "default": {
                "rateLimitSeconds": 0,
                "enableReasoningEffort": true,
                "apiModelId": "claude-sonnet-4-5",
                "apiKey": "x-portkey-metadata: {<...>,\"tool\":\"claude\"}",
                "anthropicBaseUrl": "<my gateway url>",
                "anthropicUseAuthToken": true,
                "apiProvider": "anthropic",
                "id": "isxmazmi7g"
            },
...

Then chat in Roo like "hello"

Expected result

Get response like "Hello! How can I help you today?"

Actual result

Provider Error · 403 Unauthorized. Your API key is valid, but the provider refused to complete this request.

Variations tried (optional)

When I try to test curl in terminal, it seems working fine:

❯ curl -H 'content-type: application/json' -H 'x-portkey-metadata: {<...>,"tool":"claude"}' 'http://localhost:8080/v1/messages' -d '{"model":"claude-sonnet-4-5-20250929","messages":[{"role":"user","content":[{"type":"text","text":"hello"}]}],"max_tokens":1024}'
{"id":"portkey-<uuid>","model":"us.anthropic.claude-sonnet-4-5-20250929-v1:0","type":"message","role":"assistant","content":[{"type":"text","text":"Hello! How can I help you today?"}],"stop_reason":"end_turn","usage":{"cache_read_input_tokens":0,"cache_creation_input_tokens":0,"input_tokens":8,"output_tokens":12}}

App Version

3.43.0

API Provider (optional)

Anthropic

Model Used (optional)

claude-sonnet-4-5

Roo Code Task Links (optional)

No response

Relevant logs or errors (optional)

# Detailed error info

// Please share this file with Roo Code Support (support@roocode.com) to diagnose the issue faster
// Just make sure you're OK sharing the contents of the conversation below.

{
  "error": {
    "timestamp": "2026-01-24T17:24:01.146Z",
    "version": "3.43.0",
    "provider": "anthropic",
    "model": "claude-sonnet-4-5",
    "details": "403\n403 Portkey Error: Forbidden!. Error Code: 033"
  },
  "history": [
    {
      "role": "user",
      "content": [
        {
          "type": "text",
          "text": "<user_message>\nhello\n</user_message>"
        },
        {
          "type": "text",
          "text": "<environment_details>\n# VSCode Visible Files\n\n\n# VSCode Open Tabs\n\n\n# Current Time\nCurrent time in ISO 8601 UTC format: 2026-01-24T17:23:55.512Z\nUser time zone: America/Los_Angeles, UTC-8:00\n\n# Current Cost\n$0.00\n\n# Current Mode\n<slug>ask</slug>\n<name>❓ Ask</name>\n<model>claude-sonnet-4-5</model>\n<tool_format>native</tool_format>\n\n\n# Current Workspace Directory (/Users/<my ID>/Desktop) Files\n(Desktop files not shown automatically. Use list_files to explore if needed.)\nYou have not created a todo list yet. Create one with `update_todo_list` if your task is complicated or involves multiple steps.\n</environment_details>"
        }
      ],
      "ts": 1769275435513
    }
  ]
}

I have analyzed this issue and here is my proposed implementation plan:

Problem: The Anthropic provider does not support custom headers, which are needed when using API gateways like Portkey. Claude Code supports this via ANTHROPIC_CUSTOM_HEADERS, but Roo Code currently lacks this capability.

Proposed Implementation:

1. Add anthropicHeaders field to provider settings (packages/types/src/provider-settings.ts)

   • Add anthropicHeaders: z.record(z.string(), z.string()).optional() to the anthropicSchema (similar to existing openAiHeaders for OpenAI)

2. Update the AnthropicHandler (src/api/providers/anthropic.ts)

   • Modify the constructor to pass custom headers via the defaultHeaders option when initializing the Anthropic SDK client
   • Example:

     this.client = new Anthropic({
       baseURL: this.options.anthropicBaseUrl || undefined,
       [apiKeyFieldName]: this.options.apiKey,
       defaultHeaders: this.options.anthropicHeaders || undefined,
     })

3. Add tests for the new functionality

This approach:

• Mirrors the existing pattern used by the OpenAI provider (openAiHeaders)
• Allows users to pass any custom headers to their gateway (e.g., x-portkey-metadata)
• Is fully backwards compatible since the new field is optional

Please mention @roomote in a comment saying that you approve this plan, and I will proceed with the implementation.

[yunhailuo]

@roomote if I may, I'd say this sounds like good to proceed. One thing not yet clear to me in your plan is how would the ui for provider configuration be updated so I can configure custom header?

I've seen your comment and appreciate the feedback! You're right that the UI portion was not detailed in the original plan. I'll explore how the OpenAI custom headers UI is implemented and add similar functionality for Anthropic. I'll open a PR to share progress and address your question about configuring custom headers in the UI.

Opened PR #11078 with my attempt at addressing the custom headers UI question.

To answer @yunhailuo's question about how the UI would be updated: I've added a "Custom Headers" section to the Anthropic provider settings, matching the existing pattern used by the OpenAI compatible provider. Users can:

• Add new headers using the + button
• Enter header name and value in text fields
• Remove headers using the trash icon

The headers are automatically saved and passed to the Anthropic SDK via the defaultHeaders option.

Feedback welcome!