Use decoupled way for backend client

README.md

@@ -38,6 +38,31 @@ Agent 配置路径优先级
 - 如果要引用环境变量，请在 YAML 显式写 `${ENV_VAR}`。
 - `siliconflow` 独立 section 已移除；请在 `agent.llm / agent.tts / agent.asr` 内通过 `provider`、`api_key`、`api_url`、`model` 配置。
 
+## Backend Integration
+
+Engine runtime now supports adapter-based backend integration:
+
+- `BACKEND_MODE=auto|http|disabled`
+- `BACKEND_URL` + `BACKEND_TIMEOUT_SEC`
+- `HISTORY_ENABLED=true|false`
+
+Behavior:
+
+- `auto`: use HTTP backend only when `BACKEND_URL` is set, otherwise engine-only mode.
+- `http`: force HTTP backend; falls back to engine-only mode when URL is missing.
+- `disabled`: force engine-only mode (no backend calls).
+
+History write path is now asynchronous and buffered per session:
+
+- `HISTORY_QUEUE_MAX_SIZE`
+- `HISTORY_RETRY_MAX_ATTEMPTS`
+- `HISTORY_RETRY_BACKOFF_SEC`
+- `HISTORY_FINALIZE_DRAIN_TIMEOUT_SEC`
+
+This keeps turn processing responsive even when backend history APIs are slow/failing.
+
+Detailed notes: `docs/backend_integration.md`.
+
 测试
 
 ```