Custom tool/extension/hook/plugin modules under ~/.claude/tools are
evaluated with live side effects during createAgentSession. A module that
attaches a stdin consumer at import time — an MCP StdioServerTransport
built at module top level, or a bare process.stdin.resume() — steals
Bun's single stdin reader, so the TUI receives exactly one data event and
goes permanently deaf after the first keypress. Under tmux the terminal's
automatic DA1 reply is that one event, so the first user keystroke is
already dead: the input-deafness reported in #5378/#5618.
Broadened the loader's withExitGuard (renamed withHostGuard) to also
snapshot and restore process.stdin around third-party module evaluation:
any data/readable/end/close/error listener the module adds is removed, and
the stream's paused and raw-mode state is restored to the pre-load
snapshot. The exit guard already fenced process.exit; stdin is the same
class of host-state hijack.
Fixes#5618
roboomp
1fea9b149f