A pod serving Qwen3.8-27B logged, on every single tool-using request,

  hermes_tool_parser ... json.decoder.JSONDecodeError: Expecting value

on text that begins

  <tool_call>
  <function=agenda_udienze>
  <parameter=dal>2026-10-21</parameter>

vLLM reads that with `qwen3_xml`; `hermes` expects JSON inside <tool_call> and
cannot. Buffered, coderai's own parser rescued the call out of the text, which
is why this stayed invisible. STREAMED, vLLM had already consumed those tokens
into tool-call deltas it then failed to emit, so the call was simply gone and
the stream ended at </think>.

A name cannot separate the two syntaxes -- Qwen2.5 and the Hermes-style
finetunes genuinely are hermes, and qwen3_xml does not read JSON at all -- so
the mapping cannot just be changed. The model's TEMPLATE decides instead: it is
the model's own statement of what it emits, and this one says

  "If you choose to call a function ONLY reply in the following format:
   <tool_call>\n<function=example_function_name>\n<parameter=...>"

with no JSON form anywhere in its 8,952 bytes.

Read, not guessed, and never fatal: a repo id is fetched rather than looked up
in the cache (on a rented pod nothing is cached the first time), an unreadable
template leaves the name table's answer alone, and every failure path returns
"" -- a pod that will not launch is worse than one that reads tool calls with
the wrong parser. An explicit tool_call_parser still wins, "off" included.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S8LAP3ueNzQJtwzhgVbq66