[BUG]: opencode attach processes not terminated when tmux pane is killed (zombie process accumulation)

[raki-1203]

Problem Description

When using opencode --port 4096 (server mode) with tmux-based subagent visualization, opencode attach processes accumulate and are not properly cleaned up when their tmux panes are closed/killed.

Evidence

  Pid: Program:        Command:                                                                              Threads: User:       MemB       Cpu%
93351 opencode         opencode --port 4096                                                                  23       raki-1203   1.4G       3.9
 6228 opencode         opencode attach http://127.0.0.1:4096/ --session ses_3f37d334affePb4V7d8AFrWQLA       11       raki-1203   518M       1.8
 2068 opencode         opencode attach http://127.0.0.1:4096/ --session ses_3f384731fffeY2Y4xwWoF8tfYi       11       raki-1203   471M       1.8
 2063 opencode         opencode attach http://127.0.0.1:4096/ --session ses_3f3847c7affe1uu6zJosot0t17       7        raki-1203   491M       1.7
 3393 opencode         opencode attach http://127.0.0.1:4096/ --session ses_3f37fed31ffeMHtS0K9IZZIk4X       7        raki-1203   535M       1.7
 6399 opencode         opencode attach http://127.0.0.1:4096/ --session ses_3f37cdd7bffeVZS3hyof474y73       11       raki-1203   524M       1.8
 2046 opencode         opencode attach http://127.0.0.1:4096/ --session ses_3f3849decffesz37To7b736MlR       7        raki-1203   537M       1.8

These sessions have completed, their tmux panes have been killed, but the opencode attach processes remain running.

Steps to Reproduce

1. Start opencode in server mode: opencode --port 4096
2. Run tasks that spawn subagent sessions (e.g., using delegate_task or background agents)
3. Subagent sessions create tmux split panes via tmux split-window "opencode attach http://127.0.0.1:4096/ --session ses_xxx"
4. When subagent work completes, tmux pane is killed via tmux kill-pane -t %paneId
5. The opencode attach process continues running as orphan

Expected Behavior

When the tmux pane running opencode attach is killed (receives SIGHUP), the attach process should:

1. Detect terminal/pane closure
2. Clean up resources
3. Exit gracefully

Current Behavior

• opencode attach processes ignore SIGHUP or don't properly handle terminal closure
• Processes continue running indefinitely consuming memory (~500MB each)
• CPU usage accumulates causing MacBook to overheat
• Only manual kill or system restart clears these processes

Technical Analysis

The issue appears to be in how opencode attach handles signal:

1. SIGHUP not handled: When tmux kill-pane closes the pane, SIGHUP is sent to the process. The attach command doesn't seem to handle this signal properly.

2. Server connection kept alive: Even after the parent session calls session.abort(), the attach process maintains its server connection and keeps running.

3. No stdin/tty detection: The process doesn't detect when its stdin/tty becomes invalid.

Proposed Solutions

Option 1: Handle SIGHUP signal (Recommended)

signal.Notify(sigs, syscall.SIGHUP)
// On SIGHUP, exit gracefully

Option 2: Detect stdin/tty closure

When stdin is closed or tty becomes invalid, exit the attach process.

Option 3: Periodic server connection check

If the session is aborted on server side, the attach client should detect this and exit.

Related Issues

• Memory Leak: Orphaned processes when terminal closes without explicit exit #10563 - Memory Leak: Orphaned processes when terminal closes without explicit exit
• [Bug] MCP processes not terminated after session ends #6633 - MCP processes not terminated after session ends
• v1.1.6 still has memory bloat - heap not released + MCP orphan processes #7261 - v1.1.6 still has memory bloat + MCP orphan processes

Environment

• macOS (Apple Silicon)
• opencode v1.1.43
• Running in server mode with --port 4096
• Using tmux for subagent visualization (via oh-my-opencode plugin)

Impact

• Memory leak: ~500MB per orphaned attach process
• CPU usage accumulation
• MacBook overheating during extended use
• Requires manual process cleanup (pkill -f "opencode attach")

Workaround

Currently using this workaround before the tmux pane is closed:

# Get PID of the process in the pane, then kill it
tmux display -p -t %paneId '#{pane_pid}' | xargs kill

But this is fragile and doesn't address the root cause.

[github-actions]

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

• Memory Leak: Orphaned processes when terminal closes without explicit exit #10563: Memory Leak: Orphaned processes when terminal closes without explicit exit
• [Bug] MCP processes not terminated after session ends #6633: MCP processes not terminated after session ends
• v1.1.6 still has memory bloat - heap not released + MCP orphan processes #7261: v1.1.6 still has memory bloat + MCP orphan processes

Feel free to ignore if none of these address your specific case.

[rekram1-node]

If you are using oh my opencode please close here and reopen on their repo, some of what u are describing is not vanilla opencode

[axsuul]

I think this should be fixed now