The 'tool_name' key on role=tool messages is an internal Hermes field
(stored in the messages.tool_name SQLite column for FTS indexing) that
is not part of the OpenAI Chat Completions schema. Strict OpenAI-compatible
providers — notably Moonshot AI (Kimi) — reject it with HTTP 400:
Error from provider: Extra inputs are not permitted,
field: 'messages[N].tool_name', value: 'execute_code'
Add 'tool_name' to the sanitize block in ChatCompletionsTransport.convert_messages
alongside the existing Codex Responses API fields (codex_reasoning_items,
codex_message_items) so it is popped before the request is sent.
Reproducer:
hermes chat --model kimi-k2.6
> list the top 5 Hacker News stories
-> assistant emits tool_call(execute_code)
-> tool result message gets tool_name='execute_code'
-> next turn's payload includes messages[N].tool_name -> 400
Permissive backends (MiniMax, OpenRouter on most routes) ignore the extra
field and were masking the bug.
258965663c