Function isReasoningModel

src/model-utils.ts:118–137

(model: string | undefined)

 * (assume capable) — see the policy note above.
 */
export function isReasoningModel(model: string | undefined): boolean {
  if (!model) return true;

  const normalized = normalizeModelName(model)?.toLowerCase() ?? "";
  const id = stripProviderPrefix(normalized);

  // Env overrides win, parsed fresh so they remain test-stubbable.
  const envNon = parseEnvList(process.env.AIMOCK_NONREASONING_MODELS);
  if (matchesAny(id, envNon)) return false;
  const envReasoning = parseEnvList(process.env.AIMOCK_REASONING_MODELS);
  if (matchesAny(id, envReasoning)) return true;

  // Built-in denylist is the active guard.
  if (matchesAny(id, NONREASONING_FAMILIES)) return false;
  // Built-in reasoning list short-circuits to capable.
  if (matchesAny(id, REASONING_FAMILIES)) return true;

  // Unknown → assume reasoning-capable (fail open).
  return true;
}