fix: attribute parallel Devin subagents to their spawn calls

apps/web/src/features/conversation/narrative/__tests__/parallel-subagent-nesting.test.ts

@@ -90,6 +90,35 @@ describe("parallel sub-agent nesting", () => {
     expect(counts.subagents).toBe(4);
   });
 
+  it("never renders in-flight subagent children as active top-level rows", () => {
+    // Devin child markers carry subagent_context and never get their own
+    // terminal update, so they stay isComplete=false until the owning Agent
+    // resolves them. They must not leak into the top-level active-tool rows;
+    // that is what painted every narrative element as currently running.
+    const tools: ToolCall[] = [
+      mkTool({ id: "call-spawn", toolName: "Agent", startedAt: 1000, isComplete: true }),
+      mkTool({ id: "agent-1", toolName: "Agent", startedAt: 1001, isComplete: false, parentToolCallId: "call-spawn" }),
+      mkTool({ id: "c1", toolName: "Read", startedAt: 2000, isComplete: false, parentToolCallId: "agent-1" }),
+      mkTool({ id: "c2", toolName: "Grep", startedAt: 2100, isComplete: false, parentToolCallId: "agent-1" }),
+      mkTool({ id: "c3", toolName: "Read", startedAt: 2200, isComplete: false, parentToolCallId: "agent-1" }),
+    ];
+
+    const { items } = buildNarrativeItems({
+      toolCalls: tools,
+      hooks: [],
+      thoughtSegments: [],
+      streamingText: "",
+      isAgentRunning: true,
+    });
+
+    expect(items.filter((i) => i.type === "active-tool")).toEqual([]);
+    const agentItem = requiredSubagentItem(
+      items.find((i) => i.type === "subagent" && i.toolCall.id === "agent-1"),
+    );
+    expect(agentItem.lifecycle).toBe("started");
+    expect(agentItem.children.map((c) => c.id)).toEqual(["c1", "c2", "c3"]);
+  });
+
   it("treats empty-string parentToolCallId as top-level (cannot be a real parent id)", () => {
     // Defensive: if a bad event ever surfaces parentToolCallId: "" it must
     // be treated as no parent at all. Pre-fix, "" went into childrenMap[""]

packages/providers/src/private/devin/__tests__/devin-acp-event-mapper.test.ts

@@ -311,6 +311,33 @@ describe("mapDevinAcpSessionNotification", () => {
     expect(state.pendingSubagentCallIds).toEqual([]);
   });
 
+  it("attributes parallel subagent_started updates to their run_subagent calls in spawn order", () => {
+    const state = createDevinAcpTurnState();
+    const runSubagent = (toolCallId: string) =>
+      notification(
+        toolCall(toolCallId, {
+          kind: "other",
+          _meta: { "cognition.ai/inferenceToolName": "run_subagent" },
+        }),
+      );
+    const subagentStarted = (agentId: string) =>
+      notification({
+        sessionUpdate: "tool_call_update",
+        toolCallId: agentId,
+        status: "in_progress",
+        _meta: { "cognition.ai/subagent_started": { task: "work", title: "Work" } },
+      });
+
+    mapDevinAcpSessionNotification(runSubagent("call-a"), THREAD, state);
+    mapDevinAcpSessionNotification(runSubagent("call-b"), THREAD, state);
+
+    const first = mapDevinAcpSessionNotification(subagentStarted("agent-1"), THREAD, state);
+    const second = mapDevinAcpSessionNotification(subagentStarted("agent-2"), THREAD, state);
+
+    expect(first[0]).toMatchObject({ toolCallId: "agent-1", parentToolCallId: "call-a" });
+    expect(second[0]).toMatchObject({ toolCallId: "agent-2", parentToolCallId: "call-b" });
+  });
+
   it("copies task to description on run_subagent markers so narrative extractors find it", () => {
     const state = createDevinAcpTurnState();
     const events = mapDevinAcpSessionNotification(

packages/providers/src/private/devin/devin-acp-event-mapper.ts

@@ -322,9 +322,10 @@ function subagentStartedEvents(
   threadId: string,
   state: DevinAcpTurnState,
 ): AgentEvent[] {
-  const parentToolCallId = state.pendingSubagentCallIds[
-    state.pendingSubagentCallIds.length - 1
-  ];
+  // Devin emits subagent_started in spawn order, so pair it with the oldest
+  // unresolved run_subagent call. `last` would attach every parallel agent to
+  // the most recent call, hiding their subtrees under the wrong parent row.
+  const parentToolCallId = state.pendingSubagentCallIds.shift();
   if (parentToolCallId) state.subagentParentByAgentId.set(toolCallId, parentToolCallId);
   const task = typeof started.task === "string" ? started.task : undefined;
   const title = typeof started.title === "string" ? started.title : undefined;
@@ -423,8 +424,6 @@ function subagentCompletedEvents(
 ): AgentEvent[] {
   const parentToolCallId = state.subagentParentByAgentId.get(toolCallId);
   if (parentToolCallId) {
-    const idx = state.pendingSubagentCallIds.indexOf(parentToolCallId);
-    if (idx >= 0) state.pendingSubagentCallIds.splice(idx, 1);
     state.subagentParentByAgentId.delete(toolCallId);
   }
   state.accumulator.toolStartTimes.delete(toolCallId);