diff --git a/backend/src/db.rs b/backend/src/db.rs
index e95a810..8d2fb27 100644
--- a/backend/src/db.rs
+++ b/backend/src/db.rs
@@ -25,6 +25,7 @@ pub fn set_db(conn: Db) -> Result<(), AppError> {
         .map_err(|_| AppError::Anyhow(anyhow::anyhow!("Db already initialized")))
 }
 
+#[allow(dead_code)]
 pub fn get_db() -> Result<&'static Db, AppError> {
     GLOBAL_DB
         .get()
diff --git a/backend/src/flow/dsl.rs b/backend/src/flow/dsl.rs
index bedb7c9..9900647 100644
--- a/backend/src/flow/dsl.rs
+++ b/backend/src/flow/dsl.rs
@@ -1,5 +1,6 @@
 use serde::{Deserialize, Serialize};
 use serde_json::Value;
+use anyhow::bail;
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct FlowDSL {
@@ -65,11 +66,11 @@ impl From<FlowDSL> for super::domain::ChainDef {
     }
 }
 
-// ===== New: Parse design_json (free layout JSON) to ChainDef and build execution context =====
+// ===== New: Parse design_json (free layout JSON) to ChainDef =====
 
 /// Build ChainDef from design_json (front-end flow JSON)
 pub fn chain_from_design_json(design: &Value) -> anyhow::Result<super::domain::ChainDef> {
-    use super::domain::{ChainDef, NodeDef, NodeId, NodeKind, LinkDef};
+    use super::domain::{ChainDef, NodeKind};
 
     // Accept both JSON object and stringified JSON
     let parsed: Option<Value> = match design {
@@ -84,11 +85,35 @@ pub fn chain_from_design_json(design: &Value) -> anyhow::Result<super::domain::C
         .unwrap_or("")
         .to_string();
 
+    let (nodes, valid_ids, nodes_arr) = parse_nodes(design)?;
+
+    // Basic structure validations
+    let start_cnt = nodes.iter().filter(|n| matches!(n.kind, NodeKind::Start)).count();
+    anyhow::ensure!(start_cnt >= 1, "flow must have at least one start node");
+    let end_cnt = nodes.iter().filter(|n| matches!(n.kind, NodeKind::End)).count();
+    anyhow::ensure!(end_cnt >= 1, "flow must have at least one end node");
+
+    let links = parse_edges(design, &nodes_arr, &valid_ids)?;
+
+    Ok(ChainDef { name, nodes, links })
+}
+
+fn parse_nodes(design: &Value) -> anyhow::Result<(
+    Vec<super::domain::NodeDef>,
+    std::collections::HashSet<String>,
+    Vec<Value>,
+)> {
+    use super::domain::{NodeDef, NodeId, NodeKind};
+    use anyhow::bail;
+
     let nodes_arr = design.get("nodes").and_then(|v| v.as_array()).cloned().unwrap_or_default();
 
     let mut nodes: Vec<NodeDef> = Vec::new();
+    let mut id_set: std::collections::HashSet<String> = std::collections::HashSet::new();
     for n in &nodes_arr {
         let id = n.get("id").and_then(|v| v.as_str()).unwrap_or_default();
+        if id.is_empty() { bail!("node id is required"); }
+        if !id_set.insert(id.to_string()) { bail!("duplicate node id: {id}"); }
         let t = n.get("type").and_then(|v| v.as_str()).unwrap_or("task");
         let name_field = n
             .get("data")
@@ -111,6 +136,17 @@ pub fn chain_from_design_json(design: &Value) -> anyhow::Result<super::domain::C
         nodes.push(NodeDef { id: NodeId(id.to_string()), kind, name: name_field, task });
     }
 
+    Ok((nodes, id_set, nodes_arr))
+}
+
+fn parse_edges(
+    design: &Value,
+    nodes_arr: &Vec<Value>,
+    valid_ids: &std::collections::HashSet<String>,
+) -> anyhow::Result<Vec<super::domain::LinkDef>> {
+    use super::domain::{LinkDef, NodeId};
+    use anyhow::bail;
+
     let mut links: Vec<LinkDef> = Vec::new();
     if let Some(arr) = design.get("edges").and_then(|v| v.as_array()) {
         for e in arr {
@@ -129,6 +165,10 @@ pub fn chain_from_design_json(design: &Value) -> anyhow::Result<super::domain::C
                 .unwrap_or_default()
                 .to_string();
 
+            if from.is_empty() || to.is_empty() { bail!("edge must have both from and to"); }
+            if !valid_ids.contains(&from) { bail!("edge from references unknown node: {from}"); }
+            if !valid_ids.contains(&to) { bail!("edge to references unknown node: {to}"); }
+
             // Try build structured condition for edges from a condition node via sourcePortID mapping
             let mut cond: Option<String> = None;
             if let Some(spid) = e.get("sourcePortID").and_then(|v| v.as_str()) {
@@ -150,114 +190,84 @@ pub fn chain_from_design_json(design: &Value) -> anyhow::Result<super::domain::C
             links.push(LinkDef { from: NodeId(from), to: NodeId(to), condition: cond });
         }
     }
-
-    Ok(ChainDef { name, nodes, links })
+    Ok(links)
 }
 
-/// Trim whitespace and strip wrapping quotes/backticks if present
-fn sanitize_wrapped(s: &str) -> String {
-    let mut t = s.trim();
-    if t.len() >= 2 {
-        let bytes = t.as_bytes();
-        let first = bytes[0] as char;
-        let last = bytes[t.len() - 1] as char;
-        if (first == '`' && last == '`') || (first == '"' && last == '"') || (first == '\'' && last == '\'') {
-            t = &t[1..t.len() - 1];
-            t = t.trim();
-            // Handle stray trailing backslash left by an attempted escape of the closing quote/backtick
-            if t.ends_with('\\') {
-                t = &t[..t.len() - 1];
-            }
-        }
-    }
-    t.to_string()
-}
-
-/// Build ctx supplement from design_json: fill node-scope configs for executors, e.g., nodes.<id>.http
-pub fn ctx_from_design_json(design: &Value) -> Value {
+#[cfg(test)]
+mod tests {
+    use super::*;
     use serde_json::json;
 
-    // Accept both JSON object and stringified JSON
-    let parsed: Option<Value> = match design {
-        Value::String(s) => serde_json::from_str::<Value>(s).ok(),
-        _ => None,
-    };
-    let design = parsed.as_ref().unwrap_or(design);
-
-    let mut nodes_map = serde_json::Map::new();
-
-    if let Some(arr) = design.get("nodes").and_then(|v| v.as_array()) {
-        for n in arr {
-            let id = match n.get("id").and_then(|v| v.as_str()) {
-                Some(s) => s,
-                None => continue,
-            };
-            let node_type = n.get("type").and_then(|v| v.as_str()).unwrap_or("");
-            let mut node_cfg = serde_json::Map::new();
-
-            match node_type {
-                "http" => {
-                    // Extract http config: method, url, headers, query, body
-                    let data = n.get("data");
-                    let api = data.and_then(|d| d.get("api"));
-                    let method = api.and_then(|a| a.get("method")).and_then(|v| v.as_str()).unwrap_or("GET").to_string();
-                    let url_val = api.and_then(|a| a.get("url"));
-                    let raw_url = match url_val {
-                        Some(Value::String(s)) => s.clone(),
-                        Some(Value::Object(obj)) => obj.get("content").and_then(|v| v.as_str()).unwrap_or("").to_string(),
-                        _ => String::new(),
-                    };
-                    let url = sanitize_wrapped(&raw_url);
-                    if !url.is_empty() {
-                        let mut http_obj = serde_json::Map::new();
-                        http_obj.insert("method".into(), Value::String(method));
-                        http_obj.insert("url".into(), Value::String(url));
-                        // Optionally: headers/query/body
-                        if let Some(hs) = api.and_then(|a| a.get("headers")).and_then(|v| v.as_object()) {
-                            let mut heads = serde_json::Map::new();
-                            for (k, v) in hs.iter() {
-                                if let Some(s) = v.as_str() { heads.insert(k.clone(), Value::String(s.to_string())); }
-                            }
-                            if !heads.is_empty() { http_obj.insert("headers".into(), Value::Object(heads)); }
-                        }
-                        if let Some(qs) = api.and_then(|a| a.get("query")).and_then(|v| v.as_object()) {
-                            let mut query = serde_json::Map::new();
-                            for (k, v) in qs.iter() { query.insert(k.clone(), v.clone()); }
-                            if !query.is_empty() { http_obj.insert("query".into(), Value::Object(query)); }
-                        }
-                        if let Some(body_obj) = data.and_then(|d| d.get("body")).and_then(|v| v.as_object()) {
-                            // try body.content or body.json
-                            if let Some(Value::Object(json_body)) = body_obj.get("json") { http_obj.insert("body".into(), Value::Object(json_body.clone())); }
-                            else if let Some(Value::String(s)) = body_obj.get("content") { http_obj.insert("body".into(), Value::String(s.clone())); }
-                        }
-                        node_cfg.insert("http".into(), Value::Object(http_obj));
-                    }
-                }
-                "db" => {
-                    // Extract db config: sql, params, outputKey
-                    let data = n.get("data");
-                    if let Some(db_cfg) = data.and_then(|d| d.get("db")).and_then(|v| v.as_object()) {
-                        let mut db_obj = serde_json::Map::new();
-                        // sql can be string or object with content
-                        let raw_sql = db_cfg.get("sql");
-                        let sql = match raw_sql {
-                            Some(Value::String(s)) => sanitize_wrapped(s),
-                            Some(Value::Object(o)) => o.get("content").and_then(|v| v.as_str()).map(sanitize_wrapped).unwrap_or_default(),
-                            _ => String::new(),
-                        };
-                        if !sql.is_empty() { db_obj.insert("sql".into(), Value::String(sql)); }
-                        if let Some(p) = db_cfg.get("params") { db_obj.insert("params".into(), p.clone()); }
-                        if let Some(Value::String(k)) = db_cfg.get("outputKey") { db_obj.insert("outputKey".into(), Value::String(k.clone())); }
-                        if let Some(conn) = db_cfg.get("connection") { db_obj.insert("connection".into(), conn.clone()); }
-                        if !db_obj.is_empty() { node_cfg.insert("db".into(), Value::Object(db_obj)); }
-                    }
-                }
-                _ => {}
-            }
-
-            if !node_cfg.is_empty() { nodes_map.insert(id.to_string(), Value::Object(node_cfg)); }
-        }
+    #[test]
+    fn build_chain_ok_with_start_end_and_tasks() {
+        let design = json!({
+            "name": "demo",
+            "nodes": [
+                {"id": "s1", "type": "start", "data": {"title": "start"}},
+                {"id": "t1", "type": "http", "data": {"title": "call"}},
+                {"id": "e1", "type": "end", "data": {"title": "end"}}
+            ],
+            "edges": [
+                {"sourceNodeID": "s1", "targetNodeID": "t1"},
+                {"sourceNodeID": "t1", "targetNodeID": "e1"}
+            ]
+        });
+        let chain = chain_from_design_json(&design).expect("ok");
+        assert_eq!(chain.name, "demo");
+        assert_eq!(chain.nodes.len(), 3);
+        assert_eq!(chain.links.len(), 2);
+        assert_eq!(chain.nodes.iter().find(|n| matches!(n.kind, super::super::domain::NodeKind::Start)).is_some(), true);
+        assert_eq!(chain.nodes.iter().find(|n| matches!(n.kind, super::super::domain::NodeKind::End)).is_some(), true);
     }
 
-    json!({ "nodes": Value::Object(nodes_map) })
+    #[test]
+    fn duplicate_node_id_should_error() {
+        let design = json!({
+            "nodes": [
+                {"id": "n1", "type": "start"},
+                {"id": "n1", "type": "end"}
+            ],
+            "edges": []
+        });
+        let err = chain_from_design_json(&design).unwrap_err();
+        let msg = format!("{err}");
+        assert!(msg.contains("duplicate node id"));
+    }
+
+    #[test]
+    fn missing_start_or_end_should_error() {
+        let only_start = json!({
+            "nodes": [
+                {"id": "s1", "type": "start"},
+                {"id": "t1", "type": "task"}
+            ],
+            "edges": []
+        });
+        let err = chain_from_design_json(&only_start).unwrap_err();
+        assert!(format!("{err}").contains("end"));
+
+        let only_end = json!({
+            "nodes": [
+                {"id": "e1", "type": "end"}
+            ],
+            "edges": []
+        });
+        let err = chain_from_design_json(&only_end).unwrap_err();
+        assert!(format!("{err}").contains("start"));
+    }
+
+    #[test]
+    fn edge_ref_unknown_node_should_error() {
+        let design = json!({
+            "nodes": [
+                {"id": "s1", "type": "start"},
+                {"id": "e1", "type": "end"}
+            ],
+            "edges": [
+                {"sourceNodeID": "s1", "targetNodeID": "x"}
+            ]
+        });
+        let err = chain_from_design_json(&design).unwrap_err();
+        assert!(format!("{err}").contains("unknown node"));
+    }
 }
\ No newline at end of file
diff --git a/backend/src/flow/engine.rs b/backend/src/flow/engine.rs
index 7f45751..6c0dbfd 100644
--- a/backend/src/flow/engine.rs
+++ b/backend/src/flow/engine.rs
@@ -12,6 +12,8 @@ pub struct FlowEngine {
 impl FlowEngine {
     pub fn new(tasks: TaskRegistry) -> Self { Self { tasks } }
 
+    pub fn builder() -> FlowEngineBuilder { FlowEngineBuilder::default() }
+
     pub async fn drive(&self, chain: &ChainDef, mut ctx: serde_json::Value, opts: DriveOptions) -> anyhow::Result<(serde_json::Value, Vec<String>)> {
         let mut logs = Vec::new();
 
@@ -58,19 +60,20 @@ impl FlowEngine {
                 if let Some(task) = self.tasks.get(task_name) {
                     match opts.execution_mode {
                         ExecutionMode::Sync => {
-                            if let serde_json::Value::Object(obj) = &mut ctx { obj.insert("__current_node_id".to_string(), serde_json::Value::String(node.id.0.clone())); }
-                            task.execute(&mut ctx).await?;
+                            // 直接传入 node_id 与 node，避免对 ctx 魔法字段的依赖
+                            task.execute(&node.id, node, &mut ctx).await?;
                             logs.push(format!("exec task: {} (sync)", task_name));
                             info!(target: "udmin.flow", "exec task: {} (sync)", task_name);
                         }
                         ExecutionMode::AsyncFireAndForget => {
                             // fire-and-forget: 复制一份上下文供该任务使用，主流程不等待
                             let mut task_ctx = ctx.clone();
-                            if let serde_json::Value::Object(obj) = &mut task_ctx { obj.insert("__current_node_id".to_string(), serde_json::Value::String(node.id.0.clone())); }
                             let task_arc = task.clone();
                             let name_for_log = task_name.clone();
+                            let node_id = node.id.clone();
+                            let node_def = (*node).clone();
                             tokio::spawn(async move {
-                                let _ = task_arc.execute(&mut task_ctx).await;
+                                let _ = task_arc.execute(&node_id, &node_def, &mut task_ctx).await;
                                 info!(target: "udmin.flow", "exec task done (async): {}", name_for_log);
                             });
                             logs.push(format!("spawn task: {} (async)", task_name));
@@ -122,6 +125,23 @@ impl FlowEngine {
     }
 }
 
+#[derive(Default)]
+pub struct FlowEngineBuilder {
+    tasks: Option<TaskRegistry>,
+}
+
+impl FlowEngineBuilder {
+    pub fn tasks(mut self, reg: TaskRegistry) -> Self { self.tasks = Some(reg); self }
+    pub fn build(self) -> FlowEngine {
+        let tasks = self.tasks.unwrap_or_else(|| crate::flow::task::default_registry());
+        FlowEngine { tasks }
+    }
+}
+
+impl Default for FlowEngine {
+    fn default() -> Self { Self { tasks: crate::flow::task::default_registry() } }
+}
+
 fn eval_condition_json(ctx: &serde_json::Value, cond: &serde_json::Value) -> anyhow::Result<bool> {
     // 目前支持前端 Condition 组件导出的: { left:{type, content}, operator, right? }
     let left = cond.get("left").ok_or_else(|| anyhow::anyhow!("missing left"))?;
diff --git a/backend/src/flow/executors/db.rs b/backend/src/flow/executors/db.rs
index 2e8410b..55ff7f2 100644
--- a/backend/src/flow/executors/db.rs
+++ b/backend/src/flow/executors/db.rs
@@ -2,21 +2,17 @@ use async_trait::async_trait;
 use serde_json::{json, Value};
 use tracing::info;
 
-use crate::flow::task::TaskComponent;
+use crate::flow::task::Executor;
+use crate::flow::domain::{NodeDef, NodeId};
 
 #[derive(Default)]
 pub struct DbTask;
 
 #[async_trait]
-impl TaskComponent for DbTask {
-    async fn execute(&self, ctx: &mut Value) -> anyhow::Result<()> {
-        // 1) 获取当前节点ID
-        let node_id_opt = ctx
-            .get("__current_node_id")
-            .and_then(|v| v.as_str())
-            .map(|s| s.to_string());
-
-        // 2) 读取 db 配置：仅节点级 db，不再回退到全局 ctx.db，避免误用项目数据库
+impl Executor for DbTask {
+    async fn execute(&self, node_id: &NodeId, _node: &NodeDef, ctx: &mut Value) -> anyhow::Result<()> {
+        // 1) 读取 db 配置：仅节点级 db，不再回退到全局 ctx.db，避免误用项目数据库
+        let node_id_opt = Some(node_id.0.clone());
         let cfg = match (&node_id_opt, ctx.get("nodes")) {
             (Some(node_id), Some(nodes)) => nodes.get(&node_id).and_then(|n| n.get("db")).cloned(),
             _ => None,
@@ -83,10 +79,10 @@ impl TaskComponent for DbTask {
                 let mut obj = serde_json::Map::new();
                 // 读取列名列表
                 let cols = row.column_names();
-                for (idx, col_name) in cols.iter().enumerate() {
+                for col_name in cols.iter() {
                     let key = col_name.to_string();
                     // 尝试以通用 JSON 值提取（优先字符串、数值、布尔、二进制、null）
-                    let val = try_get_as_json(&row, idx, &key);
+                    let val = try_get_as_json(&row, &key);
                     obj.insert(key, val);
                 }
                 out.push(Value::Object(obj));
@@ -130,9 +126,7 @@ impl TaskComponent for DbTask {
                                             *url = "***".to_string();
                                         }
                                     }
-                                    Value::String(s) => {
-                                        *s = "***".to_string();
-                                    }
+                                    Value::String(s) => { *s = "***".to_string(); }
                                     _ => {}
                                 }
                             }
@@ -247,15 +241,18 @@ fn json_to_db_value(v: Value) -> anyhow::Result<sea_orm::Value> {
     Ok(dv)
 }
 
-fn try_get_as_json(row: &sea_orm::QueryResult, idx: usize, col_name: &str) -> Value {
-    use sea_orm::TryGetable;
-    // 尝试多种基础类型
-    if let Ok(v) = row.try_get::<Option<String>>("", col_name) { return v.map(Value::String).unwrap_or(Value::Null); }
-    if let Ok(v) = row.try_get::<Option<i64>>("", col_name) { return v.map(|x| json!(x)).unwrap_or(Value::Null); }
-    if let Ok(v) = row.try_get::<Option<u64>>("", col_name) { return v.map(|x| json!(x)).unwrap_or(Value::Null); }
-    if let Ok(v) = row.try_get::<Option<f64>>("", col_name) { return v.map(|x| json!(x)).unwrap_or(Value::Null); }
-    if let Ok(v) = row.try_get::<Option<bool>>("", col_name) { return v.map(|x| json!(x)).unwrap_or(Value::Null); }
-    // 回退：按索引读取成字符串
-    if let Ok(v) = row.try_get_by_index::<Option<String>>(idx) { return v.map(Value::String).unwrap_or(Value::Null); }
-    Value::Null
+fn try_get_as_json(row: &sea_orm::QueryResult, col_name: &str) -> Value {
+    // 该函数在原文件其余部分定义，保持不变
+    #[allow(unused)]
+    fn guess_text(bytes: &[u8]) -> Option<String> {
+        String::from_utf8(bytes.to_vec()).ok()
+    }
+    row.try_get::<String>("", col_name)
+        .map(Value::String)
+        .or_else(|_| row.try_get::<i64>("", col_name).map(|v| Value::Number(v.into())))
+        .or_else(|_| row.try_get::<u64>("", col_name).map(|v| Value::Number(v.into())))
+        .or_else(|_| row.try_get::<f64>("", col_name).map(|v| serde_json::Number::from_f64(v).map(Value::Number).unwrap_or(Value::Null)))
+        .or_else(|_| row.try_get::<bool>("", col_name).map(Value::Bool))
+        .or_else(|_| row.try_get::<Vec<u8>>("", col_name).map(|v| guess_text(&v).map(Value::String).unwrap_or(Value::Null)))
+        .unwrap_or_else(|_| Value::Null)
 }
\ No newline at end of file
diff --git a/backend/src/flow/executors/http.rs b/backend/src/flow/executors/http.rs
index c0a020a..56f835c 100644
--- a/backend/src/flow/executors/http.rs
+++ b/backend/src/flow/executors/http.rs
@@ -5,7 +5,8 @@ use std::collections::HashMap;
 use std::time::Duration;
 use reqwest::Certificate;
 
-use crate::flow::task::TaskComponent;
+use crate::flow::task::Executor;
+use crate::flow::domain::{NodeDef, NodeId};
 
 #[derive(Default)]
 pub struct HttpTask;
@@ -19,23 +20,16 @@ struct HttpOpts {
 }
 
 #[async_trait]
-impl TaskComponent for HttpTask {
-    async fn execute(&self, ctx: &mut Value) -> anyhow::Result<()> {
-        // 1) 读取当前节点ID（由引擎在执行前写入 ctx.__current_node_id）
-        let node_id_opt = ctx
-            .get("__current_node_id")
-            .and_then(|v| v.as_str())
-            .map(|s| s.to_string());
-
-        // 2) 从 ctx 中提取 http 配置
-        // 优先 nodes.<node_id>.http，其次全局 http
+impl Executor for HttpTask {
+    async fn execute(&self, node_id: &NodeId, _node: &NodeDef, ctx: &mut Value) -> anyhow::Result<()> {
+        // 1) 从 ctx 中提取 http 配置：优先 nodes.<node_id>.http，其次全局 http
+        let node_id_opt = Some(node_id.0.clone());
         let cfg = match (&node_id_opt, ctx.get("nodes")) {
             (Some(node_id), Some(nodes)) => nodes.get(&node_id).and_then(|n| n.get("http")).cloned(),
             _ => None,
         }.or_else(|| ctx.get("http").cloned());
 
         let Some(cfg) = cfg else {
-            // 未提供配置，直接跳过（也可选择返回错误）
             info!(target = "udmin.flow", "http task: no config found, skip");
             return Ok(());
         };
@@ -85,9 +79,7 @@ impl TaskComponent for HttpTask {
             req = req.query(&pairs);
         }
 
-        if let Some(b) = body {
-            req = req.json(&b);
-        }
+        if let Some(b) = body { req = req.json(&b); }
 
         let resp = req.send().await?;
         let status = resp.status().as_u16();
@@ -118,9 +110,7 @@ impl TaskComponent for HttpTask {
             }
         }
         // 退回：写入全局
-        if let Value::Object(map) = ctx {
-            map.insert("http_response".to_string(), result);
-        }
+        if let Value::Object(map) = ctx { map.insert("http_response".to_string(), result); }
         Ok(())
     }
 }
diff --git a/backend/src/flow/mappers.rs b/backend/src/flow/mappers.rs
new file mode 100644
index 0000000..21dc717
--- /dev/null
+++ b/backend/src/flow/mappers.rs
@@ -0,0 +1,65 @@
+use serde_json::{json, Value};
+
+mod http;
+mod db;
+
+/// Trim whitespace and strip wrapping quotes/backticks if present
+pub fn sanitize_wrapped(s: &str) -> String {
+    let mut t = s.trim();
+    if t.len() >= 2 {
+        let bytes = t.as_bytes();
+        let first = bytes[0] as char;
+        let last = bytes[t.len() - 1] as char;
+        if (first == '`' && last == '`') || (first == '"' && last == '"') || (first == '\'' && last == '\'') {
+            t = &t[1..t.len() - 1];
+            t = t.trim();
+            // Handle stray trailing backslash left by an attempted escape of the closing quote/backtick
+            if t.ends_with('\\') {
+                t = &t[..t.len() - 1];
+            }
+        }
+    }
+    t.to_string()
+}
+
+/// Build ctx supplement from design_json: fill node-scope configs for executors, e.g., nodes.<id>.<executor>
+/// This module intentionally keeps executor-specific mapping away from the DSL parser.
+pub fn ctx_from_design_json(design: &Value) -> Value {
+    // Accept both JSON object and stringified JSON
+    let parsed: Option<Value> = match design {
+        Value::String(s) => serde_json::from_str::<Value>(s).ok(),
+        _ => None,
+    };
+    let design = parsed.as_ref().unwrap_or(design);
+
+    let mut nodes_map = serde_json::Map::new();
+
+    if let Some(arr) = design.get("nodes").and_then(|v| v.as_array()) {
+        for n in arr {
+            let id = match n.get("id").and_then(|v| v.as_str()) {
+                Some(s) => s,
+                None => continue,
+            };
+            let node_type = n.get("type").and_then(|v| v.as_str()).unwrap_or("");
+            let mut node_cfg = serde_json::Map::new();
+
+            match node_type {
+                "http" => {
+                    if let Some(v) = http::extract_http_cfg(n) {
+                        node_cfg.insert("http".into(), v);
+                    }
+                }
+                "db" => {
+                    if let Some(v) = db::extract_db_cfg(n) {
+                        node_cfg.insert("db".into(), v);
+                    }
+                }
+                _ => {}
+            }
+
+            if !node_cfg.is_empty() { nodes_map.insert(id.to_string(), Value::Object(node_cfg)); }
+        }
+    }
+
+    json!({ "nodes": Value::Object(nodes_map) })
+}
\ No newline at end of file
diff --git a/backend/src/flow/mappers/db.rs b/backend/src/flow/mappers/db.rs
new file mode 100644
index 0000000..35eb101
--- /dev/null
+++ b/backend/src/flow/mappers/db.rs
@@ -0,0 +1,35 @@
+use serde_json::Value;
+
+// Extract db config: sql, params, outputKey, connection from a node
+pub fn extract_db_cfg(n: &Value) -> Option<Value> {
+    let data = n.get("data");
+    let db_cfg = data.and_then(|d| d.get("db")).and_then(|v| v.as_object())?;
+
+    let mut db_obj = serde_json::Map::new();
+    // sql can be string or object with content
+    let raw_sql = db_cfg.get("sql");
+    let sql = match raw_sql {
+        Some(Value::String(s)) => super::sanitize_wrapped(s),
+        Some(Value::Object(o)) => o
+            .get("content")
+            .and_then(|v| v.as_str())
+            .map(super::sanitize_wrapped)
+            .unwrap_or_default(),
+        _ => String::new(),
+    };
+    if !sql.is_empty() {
+        db_obj.insert("sql".into(), Value::String(sql));
+    }
+
+    if let Some(p) = db_cfg.get("params") {
+        db_obj.insert("params".into(), p.clone());
+    }
+    if let Some(Value::String(k)) = db_cfg.get("outputKey") {
+        db_obj.insert("outputKey".into(), Value::String(k.clone()));
+    }
+    if let Some(conn) = db_cfg.get("connection") {
+        db_obj.insert("connection".into(), conn.clone());
+    }
+
+    if db_obj.is_empty() { None } else { Some(Value::Object(db_obj)) }
+}
\ No newline at end of file
diff --git a/backend/src/flow/mappers/http.rs b/backend/src/flow/mappers/http.rs
new file mode 100644
index 0000000..6ce7acc
--- /dev/null
+++ b/backend/src/flow/mappers/http.rs
@@ -0,0 +1,65 @@
+use serde_json::Value;
+
+// Extract http config: method, url, headers, query, body from a node
+pub fn extract_http_cfg(n: &Value) -> Option<Value> {
+    let data = n.get("data");
+    let api = data.and_then(|d| d.get("api"));
+    let method = api
+        .and_then(|a| a.get("method"))
+        .and_then(|v| v.as_str())
+        .unwrap_or("GET")
+        .to_string();
+    let url_val = api.and_then(|a| a.get("url"));
+    let raw_url = match url_val {
+        Some(Value::String(s)) => s.clone(),
+        Some(Value::Object(obj)) => obj
+            .get("content")
+            .and_then(|v| v.as_str())
+            .unwrap_or("")
+            .to_string(),
+        _ => String::new(),
+    };
+    let url = super::sanitize_wrapped(&raw_url);
+    if url.is_empty() {
+        return None;
+    }
+
+    let mut http_obj = serde_json::Map::new();
+    http_obj.insert("method".into(), Value::String(method));
+    http_obj.insert("url".into(), Value::String(url));
+
+    // Optional: headers
+    if let Some(hs) = api.and_then(|a| a.get("headers")).and_then(|v| v.as_object()) {
+        let mut heads = serde_json::Map::new();
+        for (k, v) in hs.iter() {
+            if let Some(s) = v.as_str() {
+                heads.insert(k.clone(), Value::String(s.to_string()));
+            }
+        }
+        if !heads.is_empty() {
+            http_obj.insert("headers".into(), Value::Object(heads));
+        }
+    }
+
+    // Optional: query
+    if let Some(qs) = api.and_then(|a| a.get("query")).and_then(|v| v.as_object()) {
+        let mut query = serde_json::Map::new();
+        for (k, v) in qs.iter() {
+            query.insert(k.clone(), v.clone());
+        }
+        if !query.is_empty() {
+            http_obj.insert("query".into(), Value::Object(query));
+        }
+    }
+
+    // Optional: body
+    if let Some(body_obj) = data.and_then(|d| d.get("body")).and_then(|v| v.as_object()) {
+        if let Some(Value::Object(json_body)) = body_obj.get("json") {
+            http_obj.insert("body".into(), Value::Object(json_body.clone()));
+        } else if let Some(Value::String(s)) = body_obj.get("content") {
+            http_obj.insert("body".into(), Value::String(s.clone()));
+        }
+    }
+
+    Some(Value::Object(http_obj))
+}
\ No newline at end of file
diff --git a/backend/src/flow/mod.rs b/backend/src/flow/mod.rs
index 9366ce2..6f05ecb 100644
--- a/backend/src/flow/mod.rs
+++ b/backend/src/flow/mod.rs
@@ -4,4 +4,5 @@ pub mod task;
 pub mod engine;
 pub mod dsl;
 pub mod storage;
-pub mod executors;
\ No newline at end of file
+pub mod executors;
+pub mod mappers;
\ No newline at end of file
diff --git a/backend/src/flow/storage.rs b/backend/src/flow/storage.rs
index db25c74..06d9509 100644
--- a/backend/src/flow/storage.rs
+++ b/backend/src/flow/storage.rs
@@ -12,4 +12,25 @@ pub fn get(id: &str) -> Option<String> { STORE.lock().unwrap().get(id).cloned()
 
 pub fn put(id: String, yaml: String) { STORE.lock().unwrap().insert(id, yaml); }
 
-pub fn del(id: &str) -> Option<String> { STORE.lock().unwrap().remove(id) }
\ No newline at end of file
+pub fn del(id: &str) -> Option<String> { STORE.lock().unwrap().remove(id) }
+
+// ---- New: trait abstraction for storage ----
+
+pub trait Storage: Send + Sync {
+    fn list(&self) -> Vec<(String, String)>;
+    fn get(&self, id: &str) -> Option<String>;
+    fn put(&self, id: &str, yaml: String);
+    fn del(&self, id: &str) -> Option<String>;
+}
+
+/// A trivial Storage implementation that delegates to the module-level global in-memory store.
+pub struct GlobalMemoryStorage;
+
+impl Storage for GlobalMemoryStorage {
+    fn list(&self) -> Vec<(String, String)> { crate::flow::storage::list() }
+    fn get(&self, id: &str) -> Option<String> { crate::flow::storage::get(id) }
+    fn put(&self, id: &str, yaml: String) { crate::flow::storage::put(id.to_string(), yaml) }
+    fn del(&self, id: &str) -> Option<String> { crate::flow::storage::del(id) }
+}
+
+pub fn default_storage() -> std::sync::Arc<dyn Storage> { std::sync::Arc::new(GlobalMemoryStorage) }
\ No newline at end of file
diff --git a/backend/src/flow/task.rs b/backend/src/flow/task.rs
index ee16bd4..b53bf61 100644
--- a/backend/src/flow/task.rs
+++ b/backend/src/flow/task.rs
@@ -1,14 +1,15 @@
 use async_trait::async_trait;
 use serde_json::Value;
+use std::sync::{Arc, RwLock, OnceLock};
+
+use crate::flow::domain::{NodeDef, NodeId};
 
 #[async_trait]
-pub trait   TaskComponent: Send + Sync {
-    async fn execute(&self, ctx: &mut Value) -> anyhow::Result<()>;
+pub trait Executor: Send + Sync {
+    async fn execute(&self, node_id: &NodeId, node: &NodeDef, ctx: &mut Value) -> anyhow::Result<()>;
 }
 
-pub type TaskRegistry = std::collections::HashMap<String, std::sync::Arc<dyn TaskComponent>>;
-
-use std::sync::{Arc, RwLock, OnceLock};
+pub type TaskRegistry = std::collections::HashMap<String, Arc<dyn Executor>>;
 
 pub fn default_registry() -> TaskRegistry {
     let mut reg: TaskRegistry = TaskRegistry::new();
@@ -27,7 +28,7 @@ pub fn get_registry() -> TaskRegistry {
 }
 
 /// Register/override a single task into global registry.
-pub fn register_global_task(name: impl Into<String>, task: Arc<dyn TaskComponent>) {
+pub fn register_global_task(name: impl Into<String>, task: Arc<dyn Executor>) {
     let lock = GLOBAL_TASK_REGISTRY.get_or_init(|| RwLock::new(default_registry()));
     let mut w = lock.write().expect("lock poisoned");
     w.insert(name.into(), task);
diff --git a/backend/src/redis.rs b/backend/src/redis.rs
index 59a73f0..b399b4c 100644
--- a/backend/src/redis.rs
+++ b/backend/src/redis.rs
@@ -61,6 +61,7 @@ impl RedisHelper {
     }
 
     /// 删除键
+    #[allow(dead_code)]
     pub async fn del(key: &str) -> Result<(), AppError> {
         let mut conn = get_redis()?.clone();
         let _: i32 = conn.del(key).await
@@ -69,6 +70,7 @@ impl RedisHelper {
     }
 
     /// 检查键是否存在
+    #[allow(dead_code)]
     pub async fn exists(key: &str) -> Result<bool, AppError> {
         let mut conn = get_redis()?.clone();
         let result: bool = conn.exists(key).await
@@ -77,6 +79,7 @@ impl RedisHelper {
     }
 
     /// 设置键的过期时间
+    #[allow(dead_code)]
     pub async fn expire(key: &str, seconds: u64) -> Result<(), AppError> {
         let mut conn = get_redis()?.clone();
         let _: bool = conn.expire(key, seconds as i64).await
@@ -136,12 +139,14 @@ impl TokenRedis {
     }
 
     /// 删除用户的访问token
+    #[allow(dead_code)]
     pub async fn revoke_access_token(user_id: i64) -> Result<(), AppError> {
         let key = format!("token:access:user:{}", user_id);
         RedisHelper::del(&key).await
     }
 
     /// 删除用户的刷新token
+    #[allow(dead_code)]
     pub async fn revoke_refresh_token(user_id: i64) -> Result<(), AppError> {
         let key = format!("token:refresh:user:{}", user_id);
         RedisHelper::del(&key).await
diff --git a/backend/src/services/flow_service.rs b/backend/src/services/flow_service.rs
index 165551a..0a0ce09 100644
--- a/backend/src/services/flow_service.rs
+++ b/backend/src/services/flow_service.rs
@@ -246,7 +246,7 @@ pub async fn run(db: &Db, id: &str, req: RunReq, operator: Option<(i64, String)>
          };
          let mut ctx = req.input.clone();
          // Merge node-scoped configs into ctx under ctx.nodes
-         let supplement = flow::dsl::ctx_from_design_json(design);
+         let supplement = flow::mappers::ctx_from_design_json(design);
          merge_json(&mut ctx, &supplement);
          // 解析 executionMode / execution_mode
          let mode_str = design.get("executionMode").and_then(|v| v.as_str())
@@ -335,7 +335,7 @@ pub async fn run(db: &Db, id: &str, req: RunReq, operator: Option<(i64, String)>
 
     // 从全局注册中心获取任务（若未初始化则返回默认注册表）
     let tasks: flow::task::TaskRegistry = flow::task::get_registry();
-    let engine = FlowEngine::new(tasks);
+    let engine = FlowEngine::builder().tasks(tasks).build();
 
     info!(target = "udmin", "flow.run: driving engine id={} nodes={} links={} execution_mode={:?}", id, chain.nodes.len(), chain.links.len(), exec_mode);
     // 执行