The stdin-read loop in entry.py calls handle_request() inline, so the
five handlers that can block for seconds to minutes
(slash.exec, cli.exec, shell.exec, session.resume, session.branch)
freeze the dispatcher. While one is running, any inbound RPC —
notably approval.respond and session.interrupt — sits unread in the
pipe buffer and lands only after the slow handler returns.
Route only those five onto a small ThreadPoolExecutor; every other
handler stays on the main thread so the fast-path ordering is
unchanged and the audit surface stays small. write_json is already
_stdout_lock-guarded, so concurrent response writes are safe. Pool
size defaults to 4 (overridable via HERMES_TUI_RPC_POOL_WORKERS).
- add _LONG_HANDLERS set + ThreadPoolExecutor + atexit shutdown
- new dispatch(req) function: pool for long handlers, inline for rest
- _run_and_emit wraps pool work in a try/except so a misbehaving
handler still surfaces as a JSON-RPC error instead of silently
dying in a worker
- entry.py swaps handle_request → dispatch
- 5 new tests: sync path still inline, long handlers emit via stdout,
fast handler not blocked behind slow one, handler exceptions map to
error responses, non-long methods always take the sync path
Manual repro confirms the fix: shell.exec(sleep 3) + terminal.resize
sent back-to-back now returns the resize response at t=0s while the
sleep finishes independently at t=3s. Before, both landed together
at t=3s.
Fixes#12546.
