fix(opencode): zombie processes from detached shell children on Linux #29506

Summary

tool/shell.ts spawns child shell processes with detached: true on Linux, causing zombie processes to accumulate over multiple opencode run sessions.

Root Cause

In packages/opencode/src/tool/shell.ts:304:

detached: process.platform !== "win32",

On Linux this spawns shell processes via setsid() into their own process group/session. When these child processes exit before the parent calls waitpid(), and with no SIGCHLD handler anywhere in the codebase, they become <defunct> zombie processes.

Observed: 8 opencode run sessions accumulated 11 zombie processes. The only fix was kill -9 on the parent opencode processes.

Proposed Fix

Change line 304 to detached: false on all platforms:

detached: false,

Without setsid(), child processes remain in the parent's process group. Node.js can properly reap them when handle.exitCode resolves. Explicit process cleanup is already handled via handle.kill() in abort/timeout paths, so signal isolation via detached is unnecessary.

Also Benefits

• shell tool stays status=running indefinitely after subprocess exits — pipe FD leak in spawn #29294 — detached: true causes parent to retain write-end FDs of child stdout pipes, preventing EOF delivery
• Bash tool: timeout-killed processes not detected as completed; user must manually abort #28654 — related timeout detection issue

Related

• fix(core): resolve spawn on exit not close to avoid bg-child hang #29108 — complementary fix for exit-vs-close race in cross-spawn-spawner.ts