Nested Subagent Fails Silently in 3-Layer Deep Chain (Works Fine in 2-Layer)

[xsrtyq]

Description

A subagent called at depth 3 (parent → child → grandchild) fails silently without any error message. The issue does not occur at depth 2 (parent → child). The problem began appearing on 2026-04-17, while everything worked normally the previous day.

The grandchild agent receives the prompt successfully (child session window appears), enters a "thinking" phase, and then abruptly terminates without any error or output — not even a single tool call or text response.

Plugins

none

OpenCode version

v1.4.7

Steps to reproduce

1.Create a main agent that uses the task tool to call a child subagent.

2.In the child subagent's prompt, instruct it to further call a grandchild subagent via the task tool.

3.Give the grandchild subagent a simple task (e.g., "read a file and summarize").

4.Observe the behavior: the grandchild subagent starts, thinks for a few seconds, then disappears with no error.

Screenshot and/or share link

Operating System

Windows11

Terminal

Windows terminal

[mguttmann]

We ran into this too. In our reference implementation (proposal #32166, PR #32167) the depth-3 silent failure is gone: the root cause on our side was task_id resume targeting a non-direct-child session, which produced an unparented/silent run. Resume is now restricted to direct children, and over-depth spawns fail loudly with a typed SubagentDepthError instead of dying silently — chains of 3+ levels (up to 5) work and are covered by tests.