fix: Anthropic via LiteLLM/proxies rejects requests with tool history but no tools param

[seilk]

When using Anthropic/Claude models via LiteLLM-based proxies (e.g., custom gateways), requests fail with:
UnsupportedParamsError: Anthropic doesn't support tool calling without tools= param specified
This happens when:

1. Message history contains previous tool calls (tool-call / tool-result)
2. Current request has no tools (e.g., compaction, title generation)

Root Cause

LiteLLM validates that if message history contains tool calls, the tools parameter must be present. Anthropic's native API now handles this gracefully, but many users route through LiteLLM proxies which enforce stricter validation.

Proposed Solution

Add a dummy tool when:

• Model is Anthropic/Claude (checked via providerID, api.id, or api.npm)
• Message history contains tool-call or tool-result
• No tools are provided (tools is empty)
  The dummy tool is excluded from activeTools so LLM won't actually call it.

Reproduction

curl -X POST "https://your-litellm-gateway" \
  -H "Authorization: Bearer $KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "model_name_for_claude",
    "messages": [
      {"role": "user", "content": "What is 2+2?"},
      {"role": "assistant", "content": null, "tool_calls": [{"id": "call_123", "type": "function", "function": {"name": "calc", "arguments": "{}"}}]},
      {"role": "tool", "tool_call_id": "call_123", "content": "4"},
      {"role": "assistant", "content": "The answer is 4."},
      {"role": "user", "content": "Thanks!"}
    ]
  }'
# Returns 400: UnsupportedParamsError

Relates to

• LiteLLM error: Anthropic doesn't support tool calling without tools= param specified #2915 (same root cause, different approach)

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• LiteLLM error: Anthropic doesn't support tool calling without tools= param specified #2915: LiteLLM error: Anthropic doesn't support tool calling without tools= param specified

Feel free to ignore if none of these address your specific case.

[hendem]

I am having this same problem.