tai/taicpp/docs/shell.md

shell: processes, boxes, live output, speech

Scope: src/shell/ (namespace detz::shell). Source of truth is ../tai.py; this file states what the C++ port does today, how it is verified, and the gaps. Wiring for other modules: wiring/shell.md.

Command Output Rule (repository AGENTS.md)

Every command an agent runs for the user streams live and is returned to the agent. The window is a fixed-height message (LiveStream, or the chat TUI's live block through the StreamSink protocol). A command that stops on a prompt (sudo, ssh, y/n) runs on a pty and asks through ask(text, secret); the answer is typed into the command, a decline (nullopt) sends end-of-file, and time spent waiting for the user never counts against the timeout. Anything that runs a process goes through RunLive with ShellIo::Stream and ShellIo::Ask. No bare subprocess-style calls for agent commands.

Caps (constants, all from tai.py)

constant	value	where
kShellTimeout (SHELL_TIMEOUT)	120 s	runlive.h
kRunOutputCap (RUN_OUTPUT_CAP)	4,000,000 chars, pty path only	runlive.h
kRunPromptIdle (RUN_PROMPT_IDLE)	1.0 s of silence before a prompt is asked	runlive.h
kRunMaxAsks (RUN_MAX_ASKS)	20 questions per command	runlive.h
kRunAnswerCap (RUN_ANSWER_CAP)	1000 chars typed per answer	runlive.h
kRunRows x kRunCols	24 x 120 pty window	pty.h
kStreamHeight (STREAM_HEIGHT)	4 lines	livestream.h
kShellSnapshotMaxFiles	25 files	targets.h
ShellSession caps	SID_MAX 64, CHAIN_CAP 64, ROWS_CAP 1000, TREE_DEPTH 8, TREE_KIDS 10, TREE_LINES 40	session.h

Parity table (tai.py symbol -> C++)

tai.py	C++	notes
run_live, run_live_pty	RunLive::Run, RunLive::RunPty	pipe path with reader thread, pty path with prompt detection; RunInterrupted on Ctrl-C when allow_interrupt (foreground only), child group killed
KeyboardInterrupt out of run_live	RunInterrupted (runlive.h)	converted to TurnInterrupted by AgentReplHost::run_turn, so the REPL prints interrupted and checkpoints
RUN_CTRL_RE, RUN_PROMPT_RE	RunLive::StripControl, RunLive::LooksLikePrompt	hand-written scanners, same alternation
PtyProc	PtyProc	posix_openpt, TIOCSCTTY, TIOCSWINSZ, poll reader, echo probe
subprocess.Popen/run, shutil.which	Popen, Subprocess::Run, Subprocess::Which (proc.h)	errno reporting through a CLOEXEC pipe, Python OSError/TimeoutExpired texts
LiveStream, stream_status, human_size	LiveStream, StreamStatus, HumanSize
Spinner	Spinner	stderr tty only, 80 ms frames, shimmer + clock when color is on
LaneBoard	LaneBoard	list_agents injected as AgentLister
Glow (every static method)	Glow (glow.h)	describe_call over JsonValue, agent_row/lanes over AgentRow
Sandbox, container_engine, box_state, update_box_caps, ensure_box, box_exec, box_python, box_transcribe, box_speak, box_opencode_binary, box_opencode_run	Sandbox (sandbox.h)	BoxOpencodeExec is the exec half; the caller runs opencode_parse_events
BOX_CONTAINERFILE, BOX_STT, BOX_TTS, BOX_OPENCODE_INSTALL_SCRIPT	BoxData (boxdata.cpp, generated from tai.py)	byte-identical, checked by the box parity case
curl_hint, CURL_HINT	CurlHint, kCurlHint
ShellSession (current, register, tree_lines, report, ...)	ShellSession (session.h)	SessionDb interface replaces store.db; pid/boot/chain logic identical
shell_target_paths, segment_targets	ShellTargets::Paths, ShellTargets::Segment	shlex, glob and os.walk ported (Shlex, PyGlob)
Tools.shell_stream, Tools.shell_ask	ShellIo::Stream, ShellIo::Ask over ShellApp
edge_token, edge_timestamp, edge_ssml, edge_chunks, ws_send, ws_recv_exact, ws_recv, edge_skew, edge_connect, edge_synthesize	EdgeSpeech (edge.h)	TLS bytes via libcurl connect-only, EdgeSocket seam for tests
play_audio, listen_audio, RECORDERS, TRANSCRIBERS	Audio (audio.h)

Old invented API (Sandbox::run(allow-list), ShellSession::exec, PtyProc::spawn/read_all, Spinner::tick/done, LiveStream::push/drain/joined, LaneBoard::set/render, Glow::highlight, speak_text) is gone; tai.py has none of it. Replacements are listed in wiring/shell.md.

How it is verified

• tests/shell_parity.py builds tests/shell_parity_driver.cpp and runs every case through the driver and through the same function of ../tai.py, comparing bytes. Real processes, a real pty (including the real su password prompt), real files, a scripted fake podman, a fake /proc, a fake websocket server. Fuzzed inputs for markdown, wrap, truncate, diff, json. python3 tests/shell_parity.py [--fuzz N] [--filter NAME] [--live] [-v].
• tests/shell_test.cpp: unit tests, build line in its header.
• Both build with -Wall -Wextra and must be warning-free; the parity run fails on any compiler warning.

Gaps and deviations (stated, not hidden)

• Unicode classes: \w, \d, str.isalnum, str.lower use hand-written ranges (exact for ASCII, Latin-1, Greek, Cyrillic basics; approximate beyond). Affects markdown italics boundaries, number tokens in highlight_python, complete_files case folding for exotic scripts.
• The pipe path of run_live keeps all output in memory (no cap), exactly like tai.py; only the pty path is capped.
• After a timeout only the shell is killed (Popen.kill), as in tai.py. A grandchild that keeps the pipe open makes run_live wait up to 10 s for the reader and leaves the grandchild running.
• Spinner and LaneBoard are time based; the parity run compares the first frames, the final clear and the frame count within 2, not every frame.
• Edge speech: wire handling is verified offline against tai.py with a scripted server. The live service answered 403 Forbidden to tai.py and to the port alike when last tried (2026-10-25, this machine), so end-to-end audio was not verified.
• Sandbox::EnsureBox image build and the opencode install were exercised only against a scripted fake engine, not a real multi-minute podman build.
• ShellIo::Ask REPL fallback: Ctrl-C/EOF during the question maps to a decline through the shared fd-0 reader, like tai.py maps KeyboardInterrupt/EOFError (decline sends end-of-file to the command).
• BackendError here is detz::shell::BackendError; the agent core converts it at the call site.