From 7874669de07685a9ab0977eb51d1b40318887c1f Mon Sep 17 00:00:00 2001
From: YeonGyu-Kim <code.yeon.gyu@gmail.com>
Date: Sun, 8 Mar 2026 02:22:22 +0900
Subject: [PATCH] feat(call-omo-agent): block sync subagent depth overflows

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
---
 src/tools/call-omo-agent/tools.test.ts | 23 +++++++++++++++++++++++
 src/tools/call-omo-agent/tools.ts      |  8 ++++++++
 2 files changed, 31 insertions(+)

diff --git a/src/tools/call-omo-agent/tools.test.ts b/src/tools/call-omo-agent/tools.test.ts
index a560c8bea..11af01a9a 100644
--- a/src/tools/call-omo-agent/tools.test.ts
+++ b/src/tools/call-omo-agent/tools.test.ts
@@ -4,12 +4,14 @@ import type { BackgroundManager } from "../../features/background-agent"
 import { createCallOmoAgent } from "./tools"
 
 describe("createCallOmoAgent", () => {
+  const assertCanSpawnMock = mock(() => Promise.resolve(undefined))
   const mockCtx = {
     client: {},
     directory: "/test",
   } as unknown as PluginInput
 
   const mockBackgroundManager = {
+    assertCanSpawn: assertCanSpawnMock,
     launch: mock(() => Promise.resolve({
       id: "test-task-id",
       sessionID: null,
@@ -99,4 +101,25 @@ describe("createCallOmoAgent", () => {
     //#then
     expect(result).not.toContain("disabled via disabled_agents")
   })
+
+  test("should return a tool error when sync spawn depth validation fails", async () => {
+    //#given
+    assertCanSpawnMock.mockRejectedValueOnce(new Error("Subagent spawn blocked: child depth 4 exceeds background_task.maxDepth=3."))
+    const toolDef = createCallOmoAgent(mockCtx, mockBackgroundManager, [])
+    const executeFunc = toolDef.execute as Function
+
+    //#when
+    const result = await executeFunc(
+      {
+        description: "Test",
+        prompt: "Test prompt",
+        subagent_type: "explore",
+        run_in_background: false,
+      },
+      { sessionID: "test", messageID: "msg", agent: "test", abort: new AbortController().signal },
+    )
+
+    //#then
+    expect(result).toContain("background_task.maxDepth=3")
+  })
 })
diff --git a/src/tools/call-omo-agent/tools.ts b/src/tools/call-omo-agent/tools.ts
index c2a169e64..5f5b5d319 100644
--- a/src/tools/call-omo-agent/tools.ts
+++ b/src/tools/call-omo-agent/tools.ts
@@ -57,6 +57,14 @@ export function createCallOmoAgent(
         return await executeBackground(args, toolCtx, backgroundManager, ctx.client)
       }
 
+      if (!args.session_id) {
+        try {
+          await backgroundManager.assertCanSpawn(toolCtx.sessionID)
+        } catch (error) {
+          return `Error: ${error instanceof Error ? error.message : String(error)}`
+        }
+      }
+
       return await executeSync(args, toolCtx, ctx)
     },
   })