feat(rails): GET /api/sub-tasks/:id — node detail with parents/events

src/hierarchy/store.ts

@@ -127,6 +127,74 @@ export async function recordSubTaskEvent(
   }
 }
 
+function tryParseJson(s: string): unknown {
+  try {
+    return JSON.parse(s);
+  } catch {
+    return s;
+  }
+}
+
+export async function getSubTaskDetail(id: string): Promise<unknown | null> {
+  const prisma = getPrisma();
+  const node = await prisma.subTask.findUnique({
+    where: { id },
+    include: {
+      events: {
+        orderBy: { timestamp: "asc" },
+        select: {
+          id: true,
+          eventType: true,
+          payloadJson: true,
+          timestamp: true,
+        },
+      },
+    },
+  });
+  if (!node) return null;
+
+  // Walk up parent chain
+  const parents: Array<{ id: string; role: string; title: string }> = [];
+  let cursor: string | null = node.parentId;
+  while (cursor) {
+    const p = await prisma.subTask.findUnique({
+      where: { id: cursor },
+      select: { id: true, parentId: true, role: true, title: true },
+    });
+    if (!p) break;
+    parents.unshift({ id: p.id, role: p.role, title: p.title });
+    cursor = p.parentId;
+  }
+
+  // Direct children list
+  const children = await prisma.subTask.findMany({
+    where: { parentId: id },
+    orderBy: { createdAt: "asc" },
+    select: {
+      id: true,
+      role: true,
+      agentName: true,
+      title: true,
+      state: true,
+      model: true,
+      startedAt: true,
+      completedAt: true,
+    },
+  });
+
+  return {
+    ...node,
+    parents,
+    childrenList: children,
+    events: node.events.map((e) => ({
+      id: e.id,
+      eventType: e.eventType,
+      payload: tryParseJson(e.payloadJson),
+      timestamp: e.timestamp,
+    })),
+  };
+}
+
 export async function getSubTaskTree(pipelineId: string): Promise<unknown> {
   const prisma = getPrisma();
   const all = await prisma.subTask.findMany({

src/server/http.ts

@@ -18,6 +18,7 @@ import {
   recordSubTaskEvent,
   updateSubTask,
   getSubTaskTree,
+  getSubTaskDetail,
 } from "../hierarchy/store.js";
 import { childLogger } from "../logger.js";
 
@@ -191,6 +192,15 @@ export async function startHttpServer(opts: ServerOpts): Promise<{
         return sendJson(res, 200, { pipelineId: pid, tree });
       }
 
+      // ── Single sub-task detail ──
+      const detailMatch = path.match(/^\/api\/sub-tasks\/([^/]+)$/);
+      if (method === "GET" && detailMatch) {
+        const id = detailMatch[1]!;
+        const detail = await getSubTaskDetail(id);
+        if (!detail) return sendJson(res, 404, { error: "not_found" });
+        return sendJson(res, 200, detail);
+      }
+
       return sendJson(res, 404, { error: "not_found", path });
     } catch (err) {
       log.error(