herdr

name	herdr
description	Control Herdr, a terminal multiplexer for coding agents. Use Herdr to inspect or control panes, tabs, workspaces, terminals, run commands, or start and monitor background processes like dev servers. Use for subagents when the user or another skill explicitly asks for or requires subagents. Requires HERDR_ENV=1.

Herdr

Herdr organizes terminals into workspaces, tabs, and panes, recognizes coding agents running inside panes, and exposes the current session through the herdr CLI.

Before issuing any control command, verify that this agent is running inside a Herdr-managed pane:

test "${HERDR_ENV:-}" = 1

If the check fails, say that you are not running inside Herdr and stop. Do not inspect or control the focused Herdr session from outside Herdr.

When the check passes, the herdr binary in PATH talks to the current session. Use it to inspect neighboring work, create terminal layout, start agents and commands, read output, and wait for state changes.

Learn the current CLI

The installed binary is the authority for command syntax. Start with:

herdr --help

Then print the relevant command group by running the group without a subcommand:

herdr agent
herdr pane
herdr workspace
herdr tab
herdr worktree
herdr terminal
herdr notification
herdr integration
herdr session

Do not run bare herdr for discovery; it launches or attaches the TUI. Do not probe a mutating nested command by omitting arguments. Commands such as herdr workspace create are valid with defaults and will execute.

Most control commands return JSON. Read identifiers and state from those responses instead of predicting them.

Understand layout, panes, and agents

Choose the primitive that matches the job:

• Workspace, tab, and pane topology organize terminal locations.
• Pane commands control raw terminals, shells, tests, servers, input, and output.
• Agent commands control the recognized coding agent currently occupying a pane.

A pane exists whether or not it contains an agent. agent start requires an existing available shell pane and never creates, splits, or moves layout. Use pane commands for ordinary processes. Use agent commands when Herdr must validate agent identity or interpret idle, working, blocked, done, and unknown lifecycle states.

Agent commands accept either a unique live agent name or the pane ID currently hosting that agent. They do not accept terminal IDs or bare agent-kind labels. Names must match [a-z][a-z0-9_-]{0,31} and be unique among live agents. A name follows the current pane occupant and is cleared when that agent exits, is released, or is replaced.

idle means the agent is ready for input and its tab has been seen in the focused Herdr UI. done is the same underlying idle state after unseen background work finishes. Focusing the tab or targeting the pane or agent with a focus command marks it seen. CLI reads do not mark it seen. blocked means Herdr recognized an approval or question UI. unknown means an agent is present but Herdr cannot classify it confidently; it does not prove completion.

Use IDs and caller context

Public IDs are opaque stable handles:

• workspace: w1
• tab: w1:t1
• pane: w1:p1

Closed tab and pane IDs are not reused. A pane moved into another workspace receives a new workspace-qualified pane ID. After pane move, continue with .result.move_result.pane.pane_id or the live agent name. The old value is reported as .result.move_result.previous_pane_id; only the moved process's inherited caller context keeps resolving that old ID, so do not use it as a general agent target.

Herdr injects the caller's context into each managed pane:

printf '%s\n' "$HERDR_WORKSPACE_ID" "$HERDR_TAB_ID" "$HERDR_PANE_ID"

Prefer --current when a pane command should target the calling pane. Omitting a target may use the UI-focused pane, which can belong to the user or another client.

Discover live state with:

herdr workspace list
herdr tab list --workspace "$HERDR_WORKSPACE_ID"
herdr pane current --current
herdr pane list --workspace "$HERDR_WORKSPACE_ID"
herdr agent list

Creation responses expose the IDs to use next. workspace create returns .result.workspace, .result.tab, and .result.root_pane. tab create returns .result.tab and .result.root_pane. pane split returns the new pane as .result.pane.

Start and coordinate an agent

Default to a sibling pane in the current tab and the current working directory. Do not create a workspace, tab, worktree, or different cwd unless the user explicitly requests that topology or location.

Honor a direction requested by the user. Otherwise inspect the caller pane:

herdr pane layout --pane "$HERDR_PANE_ID"

Split a wide pane to the right and a narrow or tall pane down. Avoid repeated same-direction splits that create unusably narrow columns or short rows. Keep the user's focus in the calling pane and explicitly preserve the caller's working directory:

herdr pane split --current --direction right --cwd "$PWD" --no-focus

Replace right with down when appropriate. Read the new pane ID from .result.pane.pane_id.

An available shell pane must be at its interactive prompt, with the shell itself in the foreground and no foreground command, editor, or agent running. Start a supported agent in that pane with a useful unique name:

herdr agent start reviewer --kind codex --pane <returned-pane-id>

Use the kind requested by the user. Run herdr agent to inspect the installed kind list and options. Pass native agent arguments only after --:

herdr agent start reviewer --kind codex --pane <returned-pane-id> -- <agent-args...>

agent start returns only after Herdr detects the expected agent in the same pane and considers it ready for interactive input. It defaults to a 30-second startup timeout.

Submit work through the agent surface:

herdr agent prompt reviewer "Review the current diff and report only actionable findings." --wait --timeout 120000

agent prompt atomically submits text and encoded Enter while honoring the pane's live bracketed-paste mode. For normal agent work, --wait is enough: it waits for the first settled idle, done, or blocked state. Do not repeat those defaults with --until.

A prompt sent from a non-working state must produce an observed lifecycle change within five seconds. Otherwise Herdr returns agent_prompt_stalled instead of waiting indefinitely. This wait tracks lifecycle state, not an individual turn; if the agent is already working, completion of the active turn may satisfy it.

Use --until only for a state-specific workflow, such as waiting for an already-running agent to request input:

herdr agent wait reviewer --until blocked --timeout 120000

Without --until, standalone agent wait uses the same settled-state defaults as agent prompt --wait.

Use logical keys for interactive agent UI controls:

herdr agent send-keys reviewer esc
herdr agent send-keys reviewer ctrl+c

Herdr validates all keys before writing any bytes. Read the result through the resolved agent:

herdr agent get reviewer
herdr agent read reviewer --source recent-unwrapped --lines 120

If a wait fails or returns blocked, inspect agent get and agent read before deciding what input to send. Use the pane surface only when raw terminal control is intentional.

Run an ordinary command in another pane

Create a sibling pane with the same geometry rule, preserve the caller's working directory, and keep user focus unchanged:

herdr pane split --current --direction right --cwd "$PWD" --no-focus

Read the new pane ID from .result.pane.pane_id, then run and inspect the command:

herdr pane run <returned-pane-id> "just test"
herdr pane wait-output <returned-pane-id> --match "test result" --timeout 120000
herdr pane read <returned-pane-id> --source recent-unwrapped --lines 120

pane run atomically sends command text and Enter. pane wait-output searches the selected snapshot immediately, so output that already exists can match. Use --match <text> for a literal substring or --regex <pattern> for a Rust regular expression. Omitting --timeout allows an indefinite wait.

Use the read source that matches the task:

• visible: the currently rendered viewport.
• recent: recent rendered output, including soft wraps.
• recent-unwrapped: recent output with soft wraps joined; prefer it for logs and transcripts.
• detection: the plain-text bottom-buffer snapshot used for agent detection.

Use --format ansi when colors and terminal styling are evidence. Otherwise use text.

--lines asks Herdr for more rows from the pane's available screen and host scrollback. If increasing it does not reveal more of a completed response, the pane is probably running the agent on the terminal's alternate screen. Rows that leave the alternate screen do not enter Herdr's host scrollback, so a larger line count cannot recover them.

After that failed read, ask the agent to write its complete response as Markdown in a temporary directory and reply only with the file path, then read the file directly. Use this only as a fallback; do not request file output in the initial prompt.

Safety and coordination rules

• Use --no-focus for background work unless the user asked to switch context.
• Use --current, an explicit pane ID, or a unique agent name. Do not rely on another client's focused pane.
• Parse IDs from JSON responses. Do not derive them from sidebar order or examples.
• Do not close workspaces, tabs, panes, or sessions you did not create unless the user explicitly asked.
• Never run herdr server stop from an active session unless the user explicitly intends to stop the server and its pane processes.
• Never kill the main Herdr process. Use named test sessions for experiments that need an isolated server.
• CLI server errors are JSON on stderr with exit status 1. CLI syntax errors exit with status 2.