Check pi liveness per tmux pane and add "Seen" marks to the control board (#1503)

First step-3 refinement from Jason's daily use. Liveness now lists the
panes of the agent's tmux session and counts it alive only if a pane runs
pi, so killed pi sessions whose tmux session still exists show offline
instead of waiting. A "Seen" button on waiting and error rows stores the
row's lastActivity in <dataRoot>/board/seen.json (clicks only, never
rewritten by a scan, fail closed if corrupt) and drops the row from
"Waiting on you" until the agent writes anything newer; "Unsee" reverses
it. New POST /api/seen route: JSON only, 4 KB limit, 400 on bad input.

Tests: control-board 63/63 (30 new), registry 69/69. Review APPROVED;
receipt docs/plans/reviews/2026-09-12_control-board-step3-seen-marks.md.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

packages/control-board/src/cli.mjs

@@ -52,12 +52,12 @@ async function main() {
   const index = scan(specs, { boardDir, isAlive });
   if (opts.print) {
     for (const s of index.sessions) {
-      const flag = s.waitingOnYou ? "*" : " ";
+      const flag = s.waitingOnYou ? "*" : s.seen ? "s" : " ";
       const age = s.ageSeconds == null ? "-" : `${Math.round(s.ageSeconds / 60)}m`;
       process.stdout.write(`${flag} ${s.state.padEnd(8)} ${s.project.padEnd(14)} ${s.agent.padEnd(16)} ${age.padStart(7)}  ${s.lastAssistantText ? s.lastAssistantText.slice(0, 80) : ""}\n`);
     }
   }
-  process.stdout.write(`board: ${boardDir} (${index.sessions.length} sessions, ${index.waitingOnYou.length} waiting on you)\n`);
+  process.stdout.write(`board: ${boardDir} (${index.sessions.length} sessions, ${index.waitingOnYou.length} waiting on you, ${index.seen.length} seen)\n`);
 }
 
 main().catch((err) => {

packages/control-board/src/page.html

@@ -52,6 +52,10 @@
   .row-toggle{font:inherit;font-weight:600;background:none;border:0;padding:2px 0;color:var(--action);
     cursor:pointer;text-align:left}
   .row-toggle:hover{text-decoration:underline}
+  .seen-toggle{font:inherit;font-size:.76rem;background:none;border:1px solid var(--border);border-radius:6px;
+    padding:1px 8px;color:var(--action);cursor:pointer;margin-left:6px;vertical-align:middle}
+  .seen-toggle:hover{border-color:var(--action)}
+  .seen-tag{font-size:.72rem;color:var(--muted);margin-left:6px;vertical-align:middle}
   .msg-error{color:var(--danger)}
   .msg-text,.msg-error{display:block;max-width:36ch;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
   .detail-row td{background:var(--raised)}
@@ -151,6 +155,18 @@
     return '<span class="badge ' + cls + '">' + esc(state) + "</span>";
   }
 
+  // A "Seen" button on rows that need you; a "seen" tag plus "Unsee" on rows
+  // you have already marked. The mark clears itself when the agent writes again.
+  function seenControl(rec) {
+    var needsYou = rec.state === "waiting" || rec.state === "error";
+    if (!needsYou || !rec.lastActivity) return "";
+    var attrs = ' data-project="' + esc(rec.project) + '" data-agent="' + esc(rec.agent) + '" data-last="' + esc(rec.lastActivity) + '"';
+    if (rec.seen) {
+      return '<span class="seen-tag">seen</span><button type="button" class="seen-toggle" data-seen="false"' + attrs + ' title="Put this row back under Waiting on you">Unsee</button>';
+    }
+    return '<button type="button" class="seen-toggle" data-seen="true"' + attrs + ' title="I have read this; hide it from Waiting on you until the agent writes again">Seen</button>';
+  }
+
   function buildRowPair(rec, showProject) {
     var idx = rowIdx++;
     var key = (showProject ? "waiting:" : "group:") + [rec.project, rec.agent].join("/");
@@ -164,7 +180,7 @@
       '<tr class="' + cls + '">' +
       projectCell +
       '<td><button type="button" class="row-toggle" data-idx="' + idx + '" data-key="' + esc(key) + '" aria-expanded="' + (open ? "true" : "false") + '" aria-controls="detail-' + idx + '">' + esc(rec.agent) + "</button></td>" +
-      "<td>" + badge(rec.state) + "</td>" +
+      "<td>" + badge(rec.state) + seenControl(rec) + "</td>" +
       "<td>" + esc(humanAge(rec.ageSeconds)) + "</td>" +
       "<td>" + msg + "</td>" +
       "</tr>";
@@ -250,6 +266,7 @@
   function renderFooter(data) {
     var counts = data.counts || {};
     var parts = STATES.map(function (s) { return cap(s) + " " + (counts[s] || 0); }).join(" · ");
+    parts += " · Seen " + ((data.seen || []).length);
     footer.innerHTML = "<p>" + esc(parts) + " — generated " + esc(timeAgo(data.generatedAt)) + " (" + esc(data.generatedAt || "") + ")</p>";
   }
 
@@ -320,7 +337,43 @@
     renderHeaderStatus();
   }
 
+  function postSeen(btn) {
+    if (fetching) return;
+    fetching = true;
+    btn.disabled = true;
+    fetch("/api/seen", {
+      method: "POST",
+      headers: { "content-type": "application/json" },
+      body: JSON.stringify({ project: btn.dataset.project, agent: btn.dataset.agent, lastActivity: btn.dataset.last, seen: btn.dataset.seen === "true" })
+    })
+      .then(function (res) {
+        return res.json().catch(function () {
+          throw new Error("the server sent a response that was not valid JSON");
+        }).then(function (body) {
+          if (!res.ok) throw new Error((body && body.error) || "HTTP " + res.status);
+          return body;
+        });
+      })
+      .then(function (body) {
+        lastData = body;
+        hideError();
+        renderAll();
+      })
+      .catch(function (err) {
+        console.error("marking seen failed", err);
+        showError(err && err.message ? err.message : "unknown error");
+        btn.disabled = false;
+      })
+      .then(function () {
+        fetching = false;
+        renderHeaderStatus();
+        scheduleNextFetch();
+      });
+  }
+
   main.addEventListener("click", function (e) {
+    var seenBtn = e.target.closest(".seen-toggle");
+    if (seenBtn) return postSeen(seenBtn);
     var btn = e.target.closest(".row-toggle");
     if (!btn) return;
     var detail = document.getElementById("detail-" + btn.dataset.idx);

packages/control-board/src/scan.mjs

@@ -5,11 +5,13 @@
 //   working  - the agent is in the middle of a turn (thinking or running tools)
 //   waiting  - the agent finished its turn; it is your move
 //   error    - the agent's last turn ended in an error, was aborted, or was cut off; look at it
-//   offline  - no live tmux session for this agent
+//   offline  - no tmux session for this agent, or its session no longer runs pi
 //   idle     - the agent is live but has no conversation yet
 //   unknown  - liveness could not be checked (tmux missing or unresponsive); not a guess
 //
-// Board files are derived and rewritable. They are not run records.
+// Board files are derived and rewritable. They are not run records. The one
+// exception is <boardDir>/seen.json, which holds Jason's "seen" marks and is
+// only changed when he clicks; a scan reads it and never rewrites it.
 
 import { existsSync, readFileSync, readdirSync, statSync, mkdirSync, writeFileSync, renameSync } from "node:fs";
 import { join, basename, isAbsolute, resolve } from "node:path";
@@ -108,17 +110,82 @@ export function deriveState({ alive, session }) {
   return "working";
 }
 
-export function tmuxIsAlive({ socket, session }) {
+// Programs that count as a live pi agent in a tmux pane. A tmux session that
+// still exists but only runs a shell (or another harness) is not alive: its
+// pi session log is history, not status.
+export const PI_COMMANDS = Object.freeze(["pi"]);
+
+export function panesRunPi(listPanesOutput) {
+  return String(listPanesOutput)
+    .split("\n")
+    .map((l) => l.trim())
+    .some((cmd) => PI_COMMANDS.includes(cmd));
+}
+
+// true: a pane in the tmux session runs pi. false: no such session, or no pane
+// runs pi. null: tmux could not be run at all (reported as "unknown", never
+// assumed alive). `exec` is injectable for tests.
+export function tmuxIsAlive({ socket, session }, { exec = spawnSync } = {}) {
   const args = [];
   if (socket) args.push("-L", socket);
-  args.push("has-session", "-t", `=${session}`);
-  const r = spawnSync("tmux", args, { encoding: "utf8", timeout: 5000 });
+  args.push("list-panes", "-s", "-t", `=${session}`, "-F", "#{pane_current_command}");
+  const r = exec("tmux", args, { encoding: "utf8", timeout: 5000 });
   if (r.error) return null;
-  return r.status === 0;
+  if (r.status !== 0) return false;
+  return panesRunPi(r.stdout ?? "");
+}
+
+// "Seen" marks: { "<project>/<agent>": "<lastActivity ISO>" }. A mark only
+// applies while the agent's newest message still has that timestamp; anything
+// the agent writes afterwards clears it automatically.
+export function seenKey(rec) {
+  return `${rec.project}/${rec.agent}`;
+}
+
+export function seenPath(boardDir) {
+  return join(boardDir, "seen.json");
+}
+
+// Fail closed: a present but unreadable seen.json refuses the scan rather than
+// silently dropping every mark.
+export function loadSeen(boardDir) {
+  const path = seenPath(boardDir);
+  if (!existsSync(path)) return {};
+  let parsed;
+  try {
+    parsed = JSON.parse(readFileSync(path, "utf8"));
+  } catch (err) {
+    throw new ConfigError(`seen marks file is not valid JSON: ${path} (${err.message})`);
+  }
+  if (!parsed || typeof parsed !== "object" || Array.isArray(parsed)) throw new ConfigError(`seen marks file must be a JSON object: ${path}`);
+  for (const [k, v] of Object.entries(parsed)) {
+    if (typeof v !== "string") throw new ConfigError(`seen marks file has a non-string value for ${JSON.stringify(k)}: ${path}`);
+  }
+  return parsed;
+}
+
+export function saveSeen(boardDir, marks) {
+  mkdirSync(boardDir, { recursive: true, mode: 0o700 });
+  writeAtomic(seenPath(boardDir), marks);
+}
+
+// Set or clear one mark. Returns the updated map.
+export function markSeen(boardDir, { project, agent, lastActivity, seen = true }) {
+  for (const [name, v] of Object.entries({ project, agent, lastActivity })) {
+    if (typeof v !== "string" || v.length === 0 || v.length > 512) throw new ConfigError(`${name} must be a non-empty string`);
+  }
+  if (project.includes("/")) throw new ConfigError("project must not contain '/'");
+  if (typeof seen !== "boolean") throw new ConfigError("seen must be true or false");
+  const marks = loadSeen(boardDir);
+  const key = seenKey({ project, agent });
+  if (seen) marks[key] = lastActivity;
+  else delete marks[key];
+  saveSeen(boardDir, marks);
+  return marks;
 }
 
 // One agent -> one status record.
-export function scanAgent(spec, { isAlive = tmuxIsAlive, now = () => new Date() } = {}) {
+export function scanAgent(spec, { isAlive = tmuxIsAlive, now = () => new Date(), seen = {} } = {}) {
   const alive = isAlive(spec.tmux);
   const file = findNewestSession(spec.sessionsDir);
   const session = file ? readSession(file) : null;
@@ -126,11 +193,14 @@ export function scanAgent(spec, { isAlive = tmuxIsAlive, now = () => new Date()
   const scannedAt = now();
   const lastActivity = session?.lastTimestamp ?? null;
   const ageSeconds = lastActivity ? Math.max(0, Math.round((scannedAt.getTime() - Date.parse(lastActivity)) / 1000)) : null;
+  const needsYou = state === "waiting" || state === "error";
+  const isSeen = needsYou && lastActivity !== null && seen[seenKey(spec)] === lastActivity;
   return {
     agent: spec.agent,
     project: spec.project,
     state,
-    waitingOnYou: state === "waiting" || state === "error",
+    waitingOnYou: needsYou && !isSeen,
+    seen: isSeen,
     alive,
     tmux: spec.tmux,
     sessionFile: file,
@@ -174,7 +244,8 @@ function writeAtomic(path, data) {
 // Scan every spec and write <boardDir>/sessions/<project>/<agent>.json plus index.json.
 export function scan(specs, { boardDir, isAlive, now } = {}) {
   if (!boardDir || !isAbsolute(boardDir)) throw new ConfigError("boardDir must be an absolute path");
-  const records = specs.map((spec) => scanAgent(spec, { isAlive, now }));
+  const seen = loadSeen(boardDir);
+  const records = specs.map((spec) => scanAgent(spec, { isAlive, now, seen }));
   for (const rec of records) {
     const dir = join(boardDir, "sessions", rec.project);
     mkdirSync(dir, { recursive: true, mode: 0o700 });
@@ -184,7 +255,8 @@ export function scan(specs, { boardDir, isAlive, now } = {}) {
   const index = {
     generatedAt,
     counts: Object.fromEntries(STATES.map((s) => [s, records.filter((r) => r.state === s).length])),
-    waitingOnYou: records.filter((r) => r.waitingOnYou).map((r) => `${r.project}/${r.agent}`),
+    waitingOnYou: records.filter((r) => r.waitingOnYou).map(seenKey),
+    seen: records.filter((r) => r.seen).map(seenKey),
     sessions: records,
   };
   mkdirSync(boardDir, { recursive: true, mode: 0o700 });

packages/control-board/src/serve.mjs

@@ -3,8 +3,14 @@
 //
 //   GET /            the page (src/page.html)
 //   GET /api/board   re-runs the scanner and returns index.json as JSON
+//   POST /api/seen   {project, agent, lastActivity, seen?} marks a row as seen
+//                    (or clears the mark with seen:false), rescans, returns index
 //   GET /healthz     {"ok":true}
 //
+// POST requires Content-Type: application/json. A plain form post from another
+// site in the browser cannot set that header without a CORS preflight, and this
+// server answers no preflight, so a stray page cannot flip marks.
+//
 // Every /api/board request rescans, so the page is never staler than its
 // refresh timer. The scan rewrites the derived board files as a side effect.
 
@@ -12,7 +18,42 @@ import { createServer as createHttpServer } from "node:http";
 import { readFileSync } from "node:fs";
 import { join } from "node:path";
 import { isIP } from "node:net";
-import { scan, ConfigError } from "./scan.mjs";
+import { scan, markSeen, ConfigError } from "./scan.mjs";
+
+const MAX_BODY = 4096;
+
+function sendJson(res, status, body) {
+  res.writeHead(status, { "content-type": "application/json", "cache-control": "no-store" });
+  res.end(JSON.stringify(body) + "\n");
+}
+
+function readJsonBody(req) {
+  return new Promise((resolvePromise, reject) => {
+    const type = String(req.headers["content-type"] || "").split(";")[0].trim().toLowerCase();
+    if (type !== "application/json") return reject(new Error("Content-Type must be application/json"));
+    const chunks = [];
+    let size = 0;
+    req.on("data", (c) => {
+      size += c.length;
+      if (size > MAX_BODY) {
+        req.destroy();
+        reject(new Error(`body larger than ${MAX_BODY} bytes`));
+        return;
+      }
+      chunks.push(c);
+    });
+    req.on("end", () => {
+      try {
+        const parsed = JSON.parse(Buffer.concat(chunks).toString("utf8"));
+        if (!parsed || typeof parsed !== "object" || Array.isArray(parsed)) throw new Error("body must be a JSON object");
+        resolvePromise(parsed);
+      } catch (err) {
+        reject(new Error(`invalid JSON body: ${err.message}`));
+      }
+    });
+    req.on("error", reject);
+  });
+}
 
 const LOOPBACK = new Set(["127.0.0.1", "::1", "localhost"]);
 
@@ -29,6 +70,22 @@ export function loadPage(path = join(import.meta.dirname, "page.html")) {
 export function createServer({ specs, boardDir, isAlive, now, page = loadPage() }) {
   return createHttpServer((req, res) => {
     const url = new URL(req.url, "http://localhost");
+    if (req.method === "POST" && url.pathname === "/api/seen") {
+      return readJsonBody(req)
+        .then((body) => {
+          try {
+            markSeen(boardDir, { project: body.project, agent: body.agent, lastActivity: body.lastActivity, seen: body.seen ?? true });
+          } catch (err) {
+            return sendJson(res, 400, { error: err.message });
+          }
+          try {
+            sendJson(res, 200, scan(specs, { boardDir, isAlive, now }));
+          } catch (err) {
+            sendJson(res, 500, { error: err.message });
+          }
+        })
+        .catch((err) => sendJson(res, 400, { error: err.message }));
+    }
     if (req.method !== "GET" && req.method !== "HEAD") {
       res.writeHead(405, { "content-type": "text/plain" });
       return res.end("method not allowed\n");