fix(dashboard): refresh Sessions list in real time when new sessions are created

The dashboard's FastAPI server and a terminal CLI are separate processes
sharing one SQLite session DB; there is no inter-process push channel.
The Sessions page polled the 50 newest sessions every 5s for the
"overview" card but only re-fetched the paginated sessions list on page
change or delete, so a session started in a terminal never appeared in
the list until the user navigated.

Reuse the existing 5s overview poll as a change signal: when the head
session id changes, silently reload the current page (no loading
spinner flicker, no scroll/reset of expanded rows or bulk selection,
which are keyed by id). The detection logic is extracted into a pure
shouldRefreshSessions() helper with unit tests. Adds a minimal vitest
setup for web/ (test script + config).

web/package.json

@@ -48,6 +48,7 @@
     "three": "^0.180.0",
     "typescript": "^6.0.3",
     "typescript-eslint": "^8.56.1",
-    "vite": "^8.0.16"
+    "vite": "^8.0.16",
+    "vitest": "^4.1.5"
   }
 }

web/src/lib/session-refresh.test.ts

@@ -0,0 +1,21 @@
+import { describe, it, expect } from "vitest";
+import { shouldRefreshSessions } from "./session-refresh";
+
+describe("shouldRefreshSessions", () => {
+  it("returns false on the first poll (no baseline yet)", () => {
+    expect(shouldRefreshSessions(null, "s2")).toBe(false);
+  });
+
+  it("returns false when the current response has no sessions", () => {
+    expect(shouldRefreshSessions("s1", null)).toBe(false);
+    expect(shouldRefreshSessions(null, null)).toBe(false);
+  });
+
+  it("returns false when the newest session id is unchanged", () => {
+    expect(shouldRefreshSessions("s1", "s1")).toBe(false);
+  });
+
+  it("returns true when a new session appears at the head of the list", () => {
+    expect(shouldRefreshSessions("s1", "s2")).toBe(true);
+  });
+});

web/src/lib/session-refresh.ts

@@ -0,0 +1,26 @@
+/**
+ * Decide whether the paginated sessions list should be silently
+ * re-fetched after an overview poll.
+ *
+ * The dashboard's FastAPI server and a terminal CLI are separate
+ * processes that share the same SQLite session DB. There is no
+ * inter-process push channel, so the Sessions page polls the 50 newest
+ * sessions every few seconds (the "overview" poll). When that poll
+ * surfaces a session id at the head of the list that we have not seen
+ * before, a new session was created in another process and the
+ * paginated list is stale — refresh it.
+ *
+ * Returns false on the very first poll (no baseline yet) and when
+ * either id is null (empty DB / transient empty response), so we never
+ * trigger a spurious reload on mount or while the DB is empty.
+ */
+export function shouldRefreshSessions(
+  prevNewestId: string | null,
+  currentNewestId: string | null,
+): boolean {
+  return (
+    prevNewestId !== null &&
+    currentNewestId !== null &&
+    prevNewestId !== currentNewestId
+  );
+}

web/src/pages/SessionsPage.tsx

@@ -30,6 +30,7 @@ import {
   Archive,
 } from "lucide-react";
 import { api } from "@/lib/api";
+import { shouldRefreshSessions } from "@/lib/session-refresh";
 import type {
   SessionInfo,
   SessionMessage,
@@ -805,8 +806,12 @@ export default function SessionsPage() {
     };
   }, [setEnd]);
 
-  const loadSessions = useCallback((p: number) => {
+  const loadSessions = useCallback((p: number, silent = false) => {
-    setLoading(true);
+    // ``silent`` skips the loading spinner so background refreshes
+    // (triggered when the overview poll detects a new session from
+    // another process) don't flicker the whole page or drop the user's
+    // scroll position.
+    if (!silent) setLoading(true);
     api
       .getSessions(PAGE_SIZE, p * PAGE_SIZE)
       .then((resp) => {
@@ -814,7 +819,9 @@ export default function SessionsPage() {
         setTotal(resp.total);
       })
       .catch(() => {})
-      .finally(() => setLoading(false));
+      .finally(() => {
+        if (!silent) setLoading(false);
+      });
   }, []);
 
   const loadStats = useCallback(() => {
@@ -828,6 +835,15 @@ export default function SessionsPage() {
     loadStats();
   }, [loadStats]);
 
+  // Refs for the overview poll's new-session detection. The poll effect
+  // below is mounted once with stable deps, so it reads the current page
+  // and the last-seen newest session id through refs instead of capturing
+  // stale values. ``newestSeenRef`` starts null so the first poll sets a
+  // baseline without triggering a redundant reload (mount already loads).
+  const newestSeenRef = useRef<string | null>(null);
+  const pageRef = useRef(page);
+  pageRef.current = page;
+
   useEffect(() => {
     loadSessions(page);
     refreshEmptyCount();
@@ -841,13 +857,27 @@ export default function SessionsPage() {
         .catch(() => {});
       api
         .getSessions(50)
-        .then((r) => setOverviewSessions(r.sessions))
+        .then((r) => {
+          setOverviewSessions(r.sessions);
+          // The dashboard server and a terminal CLI are separate
+          // processes sharing one session DB — there is no push channel,
+          // so we detect sessions created in another process here. The
+          // overview poll already fetches the 50 newest sessions, so we
+          // reuse its head id as a cheap change signal: when it changes,
+          // silently refresh the paginated list so the new session shows
+          // up in real time without a visible loading flicker.
+          const newest = r.sessions[0]?.id ?? null;
+          if (shouldRefreshSessions(newestSeenRef.current, newest)) {
+            loadSessions(pageRef.current, true);
+          }
+          newestSeenRef.current = newest;
+        })
         .catch(() => {});
     };
     loadOverview();
     const id = setInterval(loadOverview, 5000);
     return () => clearInterval(id);
-  }, []);
+  }, [loadSessions]);
 
   useEffect(() => {
     const el = logScrollRef.current;

web/vitest.config.ts

@@ -0,0 +1,16 @@
+import { defineConfig } from "vitest/config";
+import react from "@vitejs/plugin-react";
+import path from "path";
+
+export default defineConfig({
+  plugins: [react()],
+  resolve: {
+    alias: {
+      "@": path.resolve(__dirname, "./src"),
+    },
+  },
+  test: {
+    environment: "node",
+    include: ["src/**/*.test.{ts,tsx}"],
+  },
+});