Bash tool hangs with continuously-outputting background processes

[WanderWang]

Description

The Bash tool hangs indefinitely when a command spawns a background process that continuously writes to stdout/stderr. This happens even though the foreground shell command itself has already finished executing.

PR #20901 (merged in v1.3.14) partially addressed this by switching from close to exit for process completion detection. However, that fix only covers background processes that do not produce output (e.g. sleep 10 &). If the background process keeps writing to stdout (e.g. uvicorn, npm run dev, docker compose up), the Bash tool's stdout stream collector never terminates, so the entire tool execution promise never resolves.

Plugins

oh-my-openagent

OpenCode version

1.4.3

Steps to reproduce

1. Create a minimal FastAPI file demo_server.py:

from fastapi import FastAPI
app = FastAPI()
@app.get("/health")
def health(): return {"status": "ok"}

2. Run the "dangerous" command inside OpenCode's Bash tool:

bash -c "uv run uvicorn demo_server:app --host 0.0.0.0 --port 9876 & sleep 2; curl -s http://localhost:9876/health; echo 'Foreground done'"

Expected behavior: The Bash tool should return after curl, echo, and sleep complete.
Actual behavior: The Bash tool remains in running state indefinitely until timeout kills it.

3. Run the "safe" command for comparison:

bash -c "nohup uv run uvicorn demo_server:app --host 0.0.0.0 --port 9877 > /dev/null 2>&1 & sleep 2; curl -s http://localhost:9877/health; echo 'Done'"

Expected behavior: Returns immediately as expected.
Actual behavior: Returns immediately as expected.

Screenshot and/or share link

No response

Operating System

Ubuntu 22 ( as a Docker Container)

Terminal

bash

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• bash tool hangs when command spawns background child processes #20902: Same root cause — bash tool hangs when commands spawn background child processes that keep stdout/stderr open (also references PR fix: use exit event instead of close to resolve bash tool hang with background processes #20901)
• Bug: no-ending bash execution blocks the process #21060: Similar symptom — bash execution blocks indefinitely when a long-running process continuously outputs logs

If this is indeed a duplicate, please consider closing this issue and adding any additional context to the existing ones.