Sub-agent Task silently returns empty result when the final response stream fails (e.g. 503) — no error, no retry, completed work lost

Description

When a sub-agent (Task) finishes all its tool work but its final response stream then
fails — e.g. server [503] The request queue is full — the parent Task call returns an
empty result. No error is surfaced and no retry happens; the sub-agent's completed work
is silently discarded.

Reproduced on two explore sub-agents in one parent session (opencode 1.18.13). Both
completed 64 and 52 tool calls (data mining against a 151 MB DB), then hit [503] on
their last message (msg_fce23bb9..., msg_fce2648...). Both returned an empty
<task_result> to the parent. The work was only recoverable by re-extracting the
sub-agents' persisted tool outputs directly from opencode.db.

This is the known 503/free-tier overload family (#40254, #38051, #39276). The client-side
part I'm reporting is that a Task whose final stream dies should surface the stream error
to the parent (and/or retry), not return a success-looking empty result.

Plugins

@cortexkit/opencode-magic-context (context management); GitHub MCP; atomic-updater MCP

OpenCode version

1.18.13

Steps to reproduce

1. Start a Task (subagent) with a long multi-tool mining workload (many sqlite3/bash calls).
2. Hit a provider overload window so the final response stream fails with [503] ....
3. Observe: sub-agent completes all tool calls, final stream errors, sub-agent result is empty.
4. Parent receives empty result; no error shown; no retry; the mined data appears lost.

Screenshot and/or share link

No response

Operating System

Linux (Qubes OS 4.2.4) - Under Fedora (FC37) Standalone VM

Terminal

OpenCode TUI (CLI) - under Konsole