fix(server): Parse Bare Tool-Name XML Calls

[jkyamog]

Adds a narrow compatibility case for model output that uses the tool name as
the XML tag itself:

<bash>
<parameter=command>
grep -n "f5.test" /workspace/project/tests/bootstrap.cjs
</parameter>
</function>

Before this change, the C++ server did not parse this as a tool call. The raw
XML stayed in visible assistant text and the turn finished as normal text
instead of tool_calls / tool_use.

Bug

Observed through a Pi agent session using Lucebox as the model runtime.

The session record showed reasoning was already correctly separated:

{
  "type": "thinking",
  "thinkingSignature": "reasoning_content"
}

But the malformed tool call was left in the visible text content:

<bash>
<parameter=command>
grep -n "f5.test" /workspace/project/tests/bootstrap.cjs
</parameter>
</function>

The agent therefore displayed the tool XML as assistant text and did not run
the tool.

Change

• Adds parser support for bare tool-name XML:

  <TOOL_NAME>
  <parameter=KEY>VALUE</parameter>
  </function>

• Also accepts a matching generic XML close:

  </TOOL_NAME>

• Keeps the behavior constrained:

  • only runs when request tools are present
  • only accepts names in the declared tool list
  • requires at least one <parameter=...> tag
  • reuses the existing XML parameter parser and argument JSON serialization

This avoids turning arbitrary XML-ish prose into tool calls.

Review follow-up:

• The matching generic close is implemented as a backreference (</TOOL_NAME>)
  rather than "any XML close" so the regex cannot stop early on inner tags like
  </parameter>.
• The fixture asserts that </function> is fully stripped from visible content.

[jkyamog]

I encountered this issue twice on long running Pi agent session, so I decided to fix this as it occurs frequent enough. It was using Qwen 3.6 27B Q4 model. I have then run the fix with 10M-20M more tokens and so far no tool call issues.

[cubic-dev-ai]

All reported issues were addressed across 2 files

<sub>Reply with feedback, questions, or to request a fix.

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[davide221]

Thanks for the fix @jkyamog 🚀