```typescript
type Msg = { role: "system" | "user" | "assistant"; content: string };

export async function llmChat(messages: Msg[]) {
  const res = await fetch("http://localhost:11434/api/chat", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({
      model: "llama3.1",
      messages,
      stream: false
    })
  });

  if (!res.ok) {
    const txt = await res.text().catch(() => "");
    return `Rosalinda: erreur LLM local (${res.status}). ${txt}`;
  }

  const data: any = await res.json();
  return data?.message?.content ?? "Rosalinda: (réponse vide)";
}
```