feat: harden agent runtime for long-running tasks

tests/providers/test_provider_retry.py

@@ -211,3 +211,32 @@ async def test_image_fallback_without_meta_uses_default_placeholder() -> None:
         content = msg.get("content")
         if isinstance(content, list):
             assert any("[image omitted]" in (b.get("text") or "") for b in content)
+
+
+@pytest.mark.asyncio
+async def test_chat_with_retry_uses_retry_after_and_emits_wait_progress(monkeypatch) -> None:
+    provider = ScriptedProvider([
+        LLMResponse(content="429 rate limit, retry after 7s", finish_reason="error"),
+        LLMResponse(content="ok"),
+    ])
+    delays: list[float] = []
+    progress: list[str] = []
+
+    async def _fake_sleep(delay: float) -> None:
+        delays.append(delay)
+
+    async def _progress(msg: str) -> None:
+        progress.append(msg)
+
+    monkeypatch.setattr("nanobot.providers.base.asyncio.sleep", _fake_sleep)
+
+    response = await provider.chat_with_retry(
+        messages=[{"role": "user", "content": "hello"}],
+        on_retry_wait=_progress,
+    )
+
+    assert response.content == "ok"
+    assert delays == [7.0]
+    assert progress and "7s" in progress[0]
+
+