preexec_fn=os.setsid runs Python code in the forked child before exec,
which is unsafe in multi-threaded processes (CPython docs). When the
Desktop gateway loads native libraries (onnxruntime, BLAS, provider SDKs)
with active thread pools, the fork can SIGSEGV before the child execs.
Replace all preexec_fn usage with start_new_session=True, which provides
the same setsid/process-group semantics without running Python in the
fork. This is already the pattern used throughout hermes_cli/gateway.py
and hermes_cli/_subprocess_compat.py.
Fixes#46789
os.setsid, os.killpg, and os.getpgid do not exist on Windows and raise
AttributeError on import or first call. This breaks the terminal tool,
code execution sandbox, process registry, and WhatsApp bridge on Windows.
Added _IS_WINDOWS platform guard in all four affected files, following
the pattern documented in CONTRIBUTING.md. On Windows, preexec_fn is
set to None and process termination falls back to proc.terminate() /
proc.kill() instead of process group signals.
Files changed:
- tools/environments/local.py (3 call sites)
- tools/process_registry.py (2 call sites)
- tools/code_execution_tool.py (3 call sites)
- gateway/platforms/whatsapp.py (3 call sites)
