Function trimTrailingPartialTag

src/llm/thinking.ts:65–79

* If `s` ends with a dangling `<…` that has no closing `>` yet AND could still grow into a * suppressible marker (a thinking/tool open tag, or a stray closer), cut it. This is the * stateless analog of StreamDisplayFilter's tail-buffering: without it, a partial * tag like `<thinki` would

(s: string)

 * too (it resolves on the next frame).
 */
function trimTrailingPartialTag(s: string): string {
  const lt = s.lastIndexOf('<');
  if (lt === -1) return s;
  const tail = s.slice(lt);
  if (tail.includes('>')) return s; // complete tag — handled by the block/closer passes
  const lower = tail.toLowerCase();
  const openForms = ['<thinking>', '<think>', '<reasoning>', '<reflection>',
    '<function_call>', '<tool_call>', '<tool_use>', '<tool>'];
  const couldGrow =
    openForms.some(t => t.startsWith(lower)) ||
    '<function='.startsWith(lower) ||
    /^<function=[a-z_][\w.-]*$/i.test(tail) ||
    STRAY_CLOSERS.some(c => c.startsWith(lower));
  return couldGrow ? s.slice(0, lt).trimEnd() : s;
}

/**
 * Strip thinking for display from a FULL accumulated string (not a stream).