Detection

resolveMux picks a backend for you, and throws if the process is in no supported multiplexer. When you want the detection result itself — the backend name, the pane, and how it was found, without the throw — call the probe directly. See Detection for the two-mode algorithm this implements.

probeMultiplexer is unchanged by resolveMux/MuxSession: it stays the raw, exec-first call below (it is what a session’s own detection runs internally, before there is a session to bind exec to). It is the non-throwing gate for a caller that runs with-or-without a multiplexer:

import { probeMultiplexer, resolveMux, nodeExec } from 'cyber-mux'

if (probeMultiplexer(nodeExec, process.env).mux !== 'none') {
  const mux = resolveMux(process.env)
  // ...
}

import { probeMultiplexer, currentPane, nodeExec, type MuxProbe } from 'cyber-mux'

probeMultiplexer(exec, env, opts?) → MuxProbe

Two-mode detection:

1. Fast-path — $CYBER_MUX (tmux | herdr | wezterm | zellij | screen | none) is trusted outright, and also serves as an override (=none forces no-mux even inside a real multiplexer). $CYBER_MUX_PANE carries the pane id. screen is recognized here but is not a drivable backend — probeMultiplexer reports mux: 'screen', and resolveMux/resolveMuxAdapter then reject it with a named error rather than returning an adapter. Recognition is not support.
2. Discovery — otherwise, walk the process ancestry from $$, falling back to the $TMUX/$HERDR_ENV/$WEZTERM_PANE/$ZELLIJ hint only when the walk is inconclusive.

const probe = probeMultiplexer(nodeExec, process.env)
// { mux: 'tmux', pane: '%3', via: 'ancestry' }

MuxProbe carries mux, an optional pane, and via ('env' when the fast-path answered, 'ancestry' when the walk did).

ProbeOptions

• discover — set false to skip the ancestry walk and answer none when the fast-path misses, for a caller that only trusts the explicit override.
• envPrefix — the environment-variable namespace the fast-path reads, without the trailing _PANE. Defaults to CYBER_MUX. See below.

currentPane(env)

This session’s own pane, resolved from env alone (no ps walk): the $CYBER_MUX_PANE fast-path, then $TMUX_PANE, $HERDR_PANE_ID, $WEZTERM_PANE, $ZELLIJ_PANE_ID. Returns { mux, pane } tagged with the multiplexer, or undefined when the session is in no pane-carrying multiplexer. This is the mux-agnostic self-identity key that mux.callerPane() (and the raw callerPane) is built on.

Embedding under your own namespace

If you embed cyber-mux inside a host tool with its own environment convention, pass envPrefix so the fast-path reads your variables instead of CYBER_MUX, without forking detection:

// Reads $MYTOOL_MUX and $MYTOOL_MUX_PANE for the fast-path;
// discovery still walks the process ancestry unchanged.
const probe = probeMultiplexer(nodeExec, process.env, { envPrefix: 'MYTOOL_MUX' })

<prefix> names the mux and <prefix>_PANE the pane. This is one prefix per call — the host’s — not an alias list; an unset envPrefix is exactly the default CYBER_MUX behavior.