stdin-server

stdin-server — interactive stdin for a child process

Source of truth: tools/stdin-server/stdin_server.py (stdlib-only, 100% line+branch gated). Full design + caveats: tools/stdin-server/README.md.

The gap it closes

Claude Code's Bash tool runs -NonInteractive with stdin wired to the null device, so it can launch a REPL / debugger / db-shell but cannot type into one after it starts. This server owns the child process and relays its stdin/stdout — the non-duplicate surface of Desktop Commander.

Mount (opt-in, NOT always-on)

Zero third-party deps, so there is no install step. Register an MCP server whose command is python tools/stdin-server/stdin_server.py; it speaks newline-delimited JSON-RPC 2.0 on its own stdio. Mount it only for the session that needs an interactive channel — the box has a measured commit-exhaustion freeze caused by per-session stdio-MCP duplication, so do not add it to the always-on fleet.

The three verbs

• start_process(command: list[str], cwd?) -> {session_id, pid}
• interact_with_process(session_id, input, wait_ms=200) -> {output, alive, exit_code}
• read_process_output(session_id, max_chars=8192, timeout_ms=1000) -> {output, more, truncated, alive, exit_code}

more means buffered output still remains; truncated means the 256 KiB drop-oldest ring discarded older output before you read it.

Canonical flow — drive a REPL

start_process(["python", "-i", "-u"])            -> {session_id: "proc-1", pid: ...}
interact_with_process("proc-1", "print(2+2)\n")  -> {output: ">>> 4\n>>> ", alive: true}
interact_with_process("proc-1", "exit()\n")      -> {alive: false, exit_code: 0}

Windows caveat

pty is Unix-only, so children run over ordinary pipes: an isatty()-gated prompt may be suppressed (launch the CPython REPL with -i -u), and a child that writes without flushing will not emit until it flushes or exits. A ConPTY / pywinpty front-end is a documented follow-on, outside this stdlib-only scope.