Function extractFencedTypeScript

src/compiled/cognition/validate.ts:477–503

* Extract the largest TypeScript-tagged code fence from a model's response. * Models commonly wrap their output in ```typescript ... ``` (sometimes ```ts * or ```tsx). When that's present, the prose around the fence is never valid * TS — keeping it in the validator would just produce noise. If no

(value: string)

 * forgot the language tag.
 */
function extractFencedTypeScript(value: string): string {
  // Match ```<lang?>\n ... \n``` blocks. Lang is optional and case-insensitive.
  // We use a non-greedy `[\s\S]*?` so consecutive fences don't merge.
  const fenceRe = /```([a-zA-Z]*)\s*\n([\s\S]*?)\n```/g;
  const tsFences: string[] = [];
  const untaggedFences: string[] = [];
  let m: RegExpExecArray | null;
  while ((m = fenceRe.exec(value)) !== null) {
    const lang = (m[1] || "").toLowerCase();
    const body = m[2];
    if (lang === "typescript" || lang === "ts" || lang === "tsx") {
      tsFences.push(body);
    } else if (lang === "") {
      untaggedFences.push(body);
    }
  }
  // Prefer typescript-tagged fences. Fall back to the largest untagged one
  // since some models drop the language tag. If neither, return the whole
  // input — the legacy behaviour.
  const pool = tsFences.length > 0 ? tsFences : untaggedFences;
  if (pool.length === 0) return value;
  let best = pool[0];
  for (let i = 1; i < pool.length; i++) {
    if (pool[i].length > best.length) best = pool[i];
  }
  return best;
}

/**
 * Delegate to a user-supplied extension_point. The extension may return