feat(herd): a one-line mosh prompt under the session

README.md

@@ -183,13 +183,42 @@ moshcode herd ui
 │   ✕ stop   │                                   │
 │   ⊞ tile   │                                   │
 │   ← detach │                                   │
-└────────────┴───────────────────────────────────┘
+│            │                                   │
+│ enter ▸ …  │                                   │
+│ F12 ▸ …    │                                   │
+├────────────┴───────────────────────────────────┤
+│ mosh ▸ ps · start claude · show <n> · detach   │
+└────────────────────────────────────────────────┘
 ```
 
 Members and actions down the left, the selected member's **real terminal** on
 the right. Click a member to show it; click an action to start a shell, start an
 agent, or stop the selected one. `q` detaches and leaves everything running.
 
+Click the member that is already on screen — or press Enter — and the keyboard
+goes to it, so you are typing at the agent itself.
+
+### The mosh bar
+
+The row along the bottom is a mosh prompt, and it is always there. **F12** jumps
+to it from anywhere, including from inside an agent that has taken the keyboard,
+which makes it the way out of a session you cannot otherwise leave. Esc goes
+back to the session; `detach` leaves with everything still running.
+
+It takes any `moshcode herd` verb, so you can start a second agent without
+leaving the first:
+
+```
+mosh ▸ start claude          # another agent, now on screen
+mosh ▸ show api              # put a different member up
+mosh ▸ ps                    # the roster, over the session, then out of the way
+```
+
+`attach` means `show` here — in a workspace the word means "put it in the
+content pane", and the real attach would be a tmux client inside a tmux client.
+Output grows the bar over the content for as long as you are reading it, then it
+collapses back to one row.
+
 The right-hand pane is not a picture of a session — it *is* the session's pane,
 moved in. tmux's model is session → window → pane, so moving between *windows*
 cannot keep anything on screen; but `join-pane` moves a running pane into an

src/cli-schema.mjs

@@ -745,9 +745,17 @@ export const HERD_VERBS = [
   { name: "untile", description: "put tiled members back in their own sessions",
     synopsis: [["moshcode herd untile", ""]] },
   { name: "ui", description: "sidebar of members and actions, selected one beside it",
-    synopsis: [["moshcode herd ui", "click a member to show it · s shell · a agent · x stop · q detach"]],
+    synopsis: [["moshcode herd ui", "click a member to show it · click it again to type in it · F12 for the mosh bar"]],
     flags: [],
     examples: [["moshcode herd ui", "the workspace — start here"]] },
+  { name: "bar", description: "the one-line mosh prompt under the session (runs inside the workspace)",
+    synopsis: [["moshcode herd bar", "F12 reaches it from inside an agent · Esc goes back · detach leaves"]],
+    flags: [],
+    examples: [
+      ["F12", "jump to the bar from anywhere, even mid-agent"],
+      ["start claude", "another agent, without leaving this one"],
+      ["show api", "put a different member on screen"],
+    ] },
   { name: "run", description: "run ANY command in the herd — an agent moshcode does not ship, a build, a script",
     synopsis: [["moshcode herd run [--name <slug>] -- <command…>", "everything after -- is the command"]],
     flags: [

src/herd-bar.mjs

@@ -0,0 +1,196 @@
+// `moshcode herd bar` — a one-line mosh prompt pinned under the session.
+//
+// WHY THIS EXISTS. The workspace put a real agent in the content pane, which is
+// the point of it — but a real agent takes the keyboard. Click into claude and
+// every sidebar key stops working, and with tmux's status line off there is
+// nothing on screen that says how to get back out. You are looking at one agent
+// with no visible way to leave it, which is exactly the complaint.
+//
+// A status line would have been the small fix: one line of text that never goes
+// away. But a line you can only read answers "how do I get out" and nothing
+// else — you still cannot start a second agent without leaving first. So the
+// line takes input. It is the same surface as the CLI (every `moshcode herd`
+// verb works here) which means the escape hatch and the command line are one
+// thing rather than two.
+//
+// The bar is one row until it has something to say, then it grows over the
+// content, then it collapses again. Output has to go somewhere, and stealing
+// rows from the agent for a moment is cheaper than a pane that is mostly empty.
+import { spawnSync } from "node:child_process";
+
+import { tmux } from "./herd.mjs";
+import { acid, ash, bone } from "./ui.mjs";
+
+export const BAR_TITLE = "mosh-bar";
+export const SIDEBAR_TITLE = "herd";
+export const BAR_HEIGHT = 1;
+export const BAR_OPEN_HEIGHT = 14;
+
+/** The key that reaches the bar from anywhere, including from inside an agent. */
+export const BAR_KEY = "F12";
+
+export const HINT = "ps · start claude · show <n> · kill <n> · detach · help";
+
+/* ------------------------------------------------------------- pane geometry */
+
+/**
+ * Which pane is which, by title.
+ *
+ * Titles rather than indexes or ids: a pane keeps its title across `join-pane`,
+ * which is the whole reason the workspace can move panes around at all, and
+ * indexes shift every time one arrives or leaves.
+ */
+export function paneRoles(target, { runner = spawnSync } = {}) {
+  const roles = { sidebar: null, content: null, bar: null };
+  const r = tmux(["list-panes", "-t", target, "-F", "#{pane_id}\t#{pane_title}"], { runner });
+  if (!r.ok) return roles;
+  for (const line of r.stdout.split("\n")) {
+    const [paneId, title] = line.split("\t");
+    if (!paneId) continue;
+    if (title === BAR_TITLE) roles.bar = { paneId, title };
+    else if (title === SIDEBAR_TITLE) roles.sidebar = { paneId, title };
+    else roles.content = { paneId, title };
+  }
+  return roles;
+}
+
+/* --------------------------------------------------------------- line editing */
+
+/**
+ * One keystroke against the current line. Pure, so the editor is testable
+ * without a terminal — the bar itself is then only plumbing.
+ */
+export function editLine(line, key) {
+  if (key === "\r" || key === "\n") return { line, action: "submit" };
+  if (key === "\x1b") return { line: "", action: "escape" };
+  if (key === "\x03") return { line: "", action: "escape" };          // Ctrl-C
+  if (key === "\x15") return { line: "", action: "edit" };             // Ctrl-U
+  if (key === "\x17") return { line: line.replace(/\S+\s*$/, ""), action: "edit" }; // Ctrl-W
+  if (key === "\x7f" || key === "\b") return { line: line.slice(0, -1), action: "edit" };
+  if (key.length === 1 && key >= " " && key !== "\x7f") return { line: line + key, action: "edit" };
+  return { line, action: "none" };
+}
+
+/**
+ * What a typed line means.
+ *
+ * `attach` deliberately becomes `show`. Running the real attach from in here
+ * would start a tmux client inside the client already showing this pane, which
+ * tmux refuses — and the thing the word means in a workspace is "put it in the
+ * content pane" anyway.
+ */
+export function resolveCommand(input) {
+  const argv = String(input || "").trim().split(/\s+/).filter(Boolean);
+  if (!argv.length) return { kind: "empty", argv: [] };
+  const [verb, ...rest] = argv;
+  if (verb === "detach" || verb === "exit" || verb === "quit") return { kind: "detach", argv: rest };
+  if (verb === "show" || verb === "attach" || verb === "fg") return { kind: "show", argv: rest };
+  if (verb === "help" || verb === "?") return { kind: "help", argv: rest };
+  if (verb === "clear") return { kind: "clear", argv: rest };
+  return { kind: "herd", argv };
+}
+
+/** The prompt line. The hint is what makes the way out discoverable at rest. */
+export function renderPrompt(line, { cols = 80, showHint = true } = {}) {
+  const prompt = `${acid("mosh")} ${bone("▸")} `;
+  if (!line && showHint) return `${prompt}${ash(HINT.slice(0, Math.max(0, cols - 8)))}`;
+  return `${prompt}${line}`;
+}
+
+export function helpLines() {
+  return [
+    "the bar takes any moshcode herd verb:",
+    "  ps                 the roster        start claude       new agent",
+    "  show <name>        put it on screen  shell              new shell",
+    "  kill <name>        end one           tile               all at once",
+    "  read <name>        its last screen   prompt <n> <text>  type into it",
+    "",
+    `${BAR_KEY} comes back here from anywhere · Esc returns to the session · detach leaves`,
+  ];
+}
+
+/* ----------------------------------------------------------------- the bar */
+
+/**
+ * Runs inside the one-line pane at the bottom of the workspace.
+ */
+export async function herdBar({
+  stdin = process.stdin,
+  stdout = process.stdout,
+  runner = spawnSync,
+  target = "herd:ui",
+  run = null,
+} = {}) {
+  const me = process.env.TMUX_PANE;
+  const herdCommand = run || (async (argv, options) => (await import("./herd-cli.mjs")).herdCommand(argv, options));
+
+  let line = "";
+  let open = false;
+
+  const cols = () => stdout.columns || 80;
+  const collapse = () => {
+    if (!open) return;
+    open = false;
+    tmux(["resize-pane", "-t", me, "-y", String(BAR_HEIGHT)], { runner });
+  };
+  const expand = (rows) => {
+    open = true;
+    tmux(["resize-pane", "-t", me, "-y", String(Math.min(BAR_OPEN_HEIGHT, rows + 2))], { runner });
+  };
+  const draw = () => {
+    stdout.write(`\x1b[2J\x1b[H${renderPrompt(line, { cols: cols() })}`);
+  };
+  const show = (lines) => {
+    expand(lines.length);
+    stdout.write(`\x1b[2J\x1b[H${lines.join("\r\n")}\r\n${renderPrompt("", { cols: cols(), showHint: false })}`);
+  };
+  /** Give the keyboard back to whatever is on screen. */
+  const toContent = () => {
+    const roles = paneRoles(target, { runner });
+    if (roles.content) tmux(["select-pane", "-t", roles.content.paneId], { runner });
+  };
+
+  const submit = async () => {
+    const typed = line;
+    line = "";
+    const command = resolveCommand(typed);
+    if (command.kind === "empty") { collapse(); draw(); toContent(); return true; }
+    if (command.kind === "clear") { collapse(); draw(); return true; }
+    if (command.kind === "help") { show(helpLines()); return true; }
+    if (command.kind === "detach") { tmux(["detach-client"], { runner }); return false; }
+    if (command.kind === "show") {
+      const [name] = command.argv;
+      const { showMember } = await import("./herd-workspace.mjs");
+      const okShown = name && showMember(name, { runner, me });
+      if (!okShown) { show([ash(`no session named ${JSON.stringify(name || "")} — try ps`)]); return true; }
+      collapse(); draw(); toContent();
+      return true;
+    }
+    const out = [];
+    await herdCommand(command.argv, { write: (s) => out.push(...String(s).split("\n")) });
+    if (out.length) show(out);
+    else { collapse(); draw(); }
+    return true;
+  };
+
+  try { stdin.setRawMode?.(true); } catch { /* not a tty */ }
+  stdin.resume();
+  draw();
+
+  await new Promise((resolve) => {
+    stdin.on("data", async (buf) => {
+      for (const key of String(buf)) {
+        const next = editLine(line, key);
+        line = next.line;
+        if (next.action === "submit") {
+          if (!(await submit())) { resolve(); return; }
+          continue;
+        }
+        if (next.action === "escape") { collapse(); draw(); toContent(); continue; }
+        if (next.action === "edit") { if (open) { collapse(); } draw(); }
+      }
+    });
+  });
+
+  return 0;
+}

src/herd-cli.mjs

@@ -178,7 +178,7 @@ export function herdStart(argv, { write = console.log } = {}) {
   }
   write(ok(`${bone(name)} — ${key} running in the herd. the prompt is yours.`));
   if (flags.agent) write(warn("agent mode: native approvals are bypassed or auto-approved."));
-  write(info(`attach: ${acid(`moshcode attach ${name}`)} · roster: ${acid("moshcode ps")}`));
+  write(info(`workspace: ${acid("moshcode herd ui")} · attach: ${acid(`moshcode attach ${name}`)} · roster: ${acid("moshcode ps")}`));
   const note = substrateNote(substrate);
   if (note) write(info(note));
   return EXIT.matched;
@@ -253,7 +253,7 @@ export function herdRun(argv, { write = console.log, shell = false } = {}) {
     return EXIT.matched;
   }
   write(ok(`${bone(name)} — ${label} running in the herd. the prompt is yours.`));
-  write(info(`attach: ${acid(`moshcode attach ${name}`)} · roster: ${acid("moshcode ps")}`));
+  write(info(`workspace: ${acid("moshcode herd ui")} · attach: ${acid(`moshcode attach ${name}`)} · roster: ${acid("moshcode ps")}`));
   return EXIT.matched;
 }
 
@@ -729,6 +729,7 @@ const VERBS = {
   // inside it for machines with no tmux to swap panes on.
   ui: async (argv, options) => (await import("./herd-workspace.mjs")).herdUi(argv, options),
   sidebar: async (argv, options) => (await import("./herd-workspace.mjs")).herdSidebar(options),
+  bar: async (argv, options) => (await import("./herd-bar.mjs")).herdBar(options),
   tile: async (argv, options) => (await import("./herd-tile.mjs")).herdTile(argv, options),
   untile: async (argv, options) => (await import("./herd-tile.mjs")).herdUntile(argv, options),
   ps: herdPs, list: herdPs, status: herdStatus,