Fix new-window context leak showing previous session ctx%

Stop tmux status from falling back to global status files, seed new
tmux instances at 0%, rank live sessions by opened_at instead of
signals.json keepalive mtime, and bind Grok pids to tmux more reliably.

tests/dashboard.test.ts

@@ -62,6 +62,95 @@ describe("dashboard", () => {
     fs.rmSync(tmp, { recursive: true, force: true });
   });
 
+  it("new window: old live session with fresher signals mtime does not steal primary", async () => {
+    // Repro: old tab still live and signals.json keeps updating; new tab has
+    // later opened_at but no/low context — must pick new (ctx ~0), not old 78%.
+    const tmp = fs.mkdtempSync(path.join(os.tmpdir(), "hud-newwin-"));
+    const cwd = "/Users/dex/AI FILM SPACE/0717";
+    const oldId = "old-busy-78";
+    const newId = "new-window-zero";
+    const enc = encodeURIComponent(cwd);
+    const oldDir = path.join(tmp, "sessions", enc, oldId);
+    const newDir = path.join(tmp, "sessions", enc, newId);
+    fs.mkdirSync(oldDir, { recursive: true });
+    fs.mkdirSync(newDir, { recursive: true });
+
+    const oldSignals = {
+      contextWindowUsage: 78,
+      contextTokensUsed: 392180,
+      contextWindowTokens: 500000,
+      turnCount: 18,
+      toolCallCount: 344,
+      primaryModelId: "grok-4.5",
+    };
+    fs.writeFileSync(path.join(oldDir, "signals.json"), JSON.stringify(oldSignals));
+    fs.writeFileSync(
+      path.join(oldDir, "summary.json"),
+      JSON.stringify({
+        info: { id: oldId, cwd },
+        last_active_at: "2026-07-17T06:00:00.000Z",
+        updated_at: "2026-07-17T06:00:00.000Z",
+        created_at: "2026-07-17T04:00:00.000Z",
+        current_model_id: "grok-4.5",
+      }),
+    );
+    // Touch signals again so mtime is "now" (old session keepalive)
+    const now = Date.now();
+    fs.utimesSync(path.join(oldDir, "signals.json"), new Date(now), new Date(now));
+
+    fs.writeFileSync(
+      path.join(newDir, "summary.json"),
+      JSON.stringify({
+        info: { id: newId, cwd },
+        last_active_at: "2026-07-17T08:00:00.000Z",
+        updated_at: "2026-07-17T08:00:00.000Z",
+        created_at: "2026-07-17T08:00:00.000Z",
+        current_model_id: "grok-4.5",
+      }),
+    );
+    // Explicit empty/low context for new window
+    fs.writeFileSync(
+      path.join(newDir, "signals.json"),
+      JSON.stringify({
+        contextWindowUsage: 0,
+        contextTokensUsed: 0,
+        contextWindowTokens: 500000,
+        turnCount: 0,
+        toolCallCount: 0,
+        primaryModelId: "grok-4.5",
+      }),
+    );
+
+    fs.writeFileSync(
+      path.join(tmp, "active_sessions.json"),
+      JSON.stringify([
+        {
+          session_id: oldId,
+          pid: process.pid,
+          cwd,
+          opened_at: "2026-07-17T04:00:00.000Z",
+        },
+        {
+          session_id: newId,
+          pid: process.pid,
+          cwd,
+          opened_at: "2026-07-17T08:00:00.000Z",
+        },
+      ]),
+    );
+
+    const r = await refreshDashboard({ grokHome: tmp, noUsage: true });
+    assert.ok(r.session);
+    assert.equal(r.session!.sessionId, newId);
+    assert.ok(
+      Math.round(r.session!.contextPercent) < 5,
+      `new window must be ~0% ctx, got ${r.session!.contextPercent}`,
+    );
+    assert.doesNotMatch(r.title, /78%/);
+
+    fs.rmSync(tmp, { recursive: true, force: true });
+  });
+
   it("after /new: prefers newest active session, not first-listed old 78%", async () => {
     // Repro: active_sessions keeps old tab first; new tab second with low/no signals.
     const tmp = fs.mkdtempSync(path.join(os.tmpdir(), "hud-new-"));

tests/multi-session.test.ts

@@ -1,11 +1,14 @@
 import { describe, it } from "node:test";
 import assert from "node:assert/strict";
+import os from "node:os";
+import path from "node:path";
 import {
   uniqueTmuxSessionName,
   sanitizeId,
   isInProcessTree,
   parentPid,
 } from "../src/multi-session.js";
+import { tmuxStatusCommands } from "../src/tmux-hud.js";
 
 describe("multi-session isolation", () => {
   it("uniqueTmuxSessionName never returns fixed grok-hud", () => {
@@ -48,4 +51,23 @@ describe("multi-session isolation", () => {
       assert.equal(isInProcessTree(process.pid, pp), true);
     }
   });
+
+  it("tmux status format never falls back to global status (new window isolation)", () => {
+    const home = path.join(os.tmpdir(), "hud-fake-home");
+    const cmds = tmuxStatusCommands(home);
+    const formats = cmds
+      .filter((a) => a[0] === "set" && String(a[2] ?? "").startsWith("status-format"))
+      .map((a) => a.slice(3).join(" "));
+    assert.ok(formats.length >= 1);
+    for (const f of formats) {
+      // Must only read per-session path; global fallback leaked old ctx%
+      assert.match(f, /hud\/tmux\/#\{session_name\}/);
+      assert.doesNotMatch(
+        f,
+        /hud\/tmux-lines\.txt|hud\/tmux-status\.txt(?!\/)/,
+      );
+      // No "|| cat …/hud/tmux-status" style global fallback
+      assert.doesNotMatch(f, /\|\|\s*cat\s+\S*\/hud\/tmux-/);
+    }
+  });
 });