Implement Herdr-backed pane orchestration for delegated sessions as an alternative to tmux and zellij.
Manage pane lifecycle (split, rename, run, close) within the current Herdr workspace.
Keep process cleanup safe and graceful (interrupt + close).
Design
HerdrMultiplexer in index.ts implements Multiplexer.
findBinary is a which/where herdr probe with cached path.
isInsideSession checks process.env.HERDR_ENV or process.env.HERDR_PANE_ID; isAvailable uses cached binaryPath.
spawnPane resolves the parent pane via HERDR_PANE_ID or --current, splits it in the configured direction, renames the new pane to the agent description, and runs opencode attach via herdr pane run. Pane IDs are extracted by parsing JSON CLI output from herdr pane split.
closePane sends ctrl+c via herdr pane send_keys, waits briefly, then runs herdr pane close.
applyLayout is intentionally a no-op (Herdr does not expose equivalent layout rebalancing APIs).
Layout direction mapping is done by getPaneDirection:
determine parent pane from HERDR_PANE_ID env var or --current
split parent pane via herdr pane split <parent> --direction <dir>
parse JSON output to extract new pane ID (new_pane_id)
rename the pane via herdr pane send_text <pane> \x1b]0;<desc>\x07
run opencode attach <url> --session <sessionId> --dir <directory> via herdr pane run <pane>
return { success, paneId }
closePane(paneId):
herdr pane send_keys <pane> ctrl+c
wait 250ms
herdr pane close <pane>; treats exit codes 0 and 1 as successful closure.
applyLayout is a no-op retained for interface compatibility.
Integration
Selected when multiplexerConfig.type === 'herdr' or auto mode resolves to herdr (process.env.HERDR_ENV or process.env.HERDR_PANE_ID present).
Consumed by MultiplexerSessionManager as the pane backend in Herdr environments.
UI attach command semantics are identical to tmux in argument shape: opencode attach <url> --session <sessionId> --dir <directory>, so delegated sessions remain config-agnostic across backends.
