When an assistant message has tool calls but no text, the OpenAI Chat Completions format uses `content: null`, since content is optional next to tool calls and OpenAI's own API returns null there. Open WebUI sent an empty string in two places: when replaying earlier tool calls from the chat history, and when converting requests from clients that use its Anthropic-compatible endpoint. For Claude models, LiteLLM 1.81.14 through 1.108.x replaces that empty string with "[System: Empty message content sanitised to satisfy protocol]", and the model then repeats that line in its replies (LiteLLM 1.109 and later leave the empty text out instead). These messages now go out with null content, which OpenAI and every provider tested on OpenRouter (Gemini, Claude, DeepSeek, Qwen, Mistral, Llama, Kimi and Grok) accept.
Fixes#34264
Classic298andGitHub
80478abea1