diff --git a/hooks/scripts/__tests__/session-start-trends-staleness.test.mjs b/hooks/scripts/__tests__/session-start-trends-staleness.test.mjs
new file mode 100644
index 0000000..a304333
--- /dev/null
+++ b/hooks/scripts/__tests__/session-start-trends-staleness.test.mjs
@@ -0,0 +1,79 @@
+import { describe, test } from 'node:test';
+import assert from 'node:assert/strict';
+import { execFileSync } from 'node:child_process';
+import { mkdtempSync, rmSync, mkdirSync, writeFileSync, copyFileSync } from 'node:fs';
+import { join, dirname } from 'node:path';
+import { tmpdir } from 'node:os';
+import { fileURLToPath } from 'node:url';
+
+// B-S3: SessionStart emits a warn-only "trend signals are N days old" nudge,
+// driven by the trend store's newest capturedAt, and ONLY when the store already
+// holds captures. session-start is a procedural hook with no exports, so we run
+// it as a subprocess with an isolated HOME + LINKEDIN_STUDIO_DATA and inspect the
+// additionalContext. Pattern: session-start-remember.test.mjs subprocess harness.
+const here = dirname(fileURLToPath(import.meta.url));
+const hookPath = join(here, '..', 'session-start.mjs');
+const PLUGIN_ROOT = join(here, '..', '..', '..');
+const STATE_TEMPLATE = join(PLUGIN_ROOT, 'config', 'state-file.template.md');
+
+const NUDGE = 'Trend signals are';
+const isoDaysAgo = (n) => new Date(Date.now() - n * 86400000).toISOString().slice(0, 10);
+
+// Run the hook against an isolated HOME + data root; optionally seed a trend
+// store. Returns the additionalContext string the hook injected at session start.
+function runHook({ captures }) {
+  const home = mkdtempSync(join(tmpdir(), 'lis-ts-home-'));
+  const data = mkdtempSync(join(tmpdir(), 'lis-ts-data-'));
+  try {
+    // The reminders block only runs when the state file already exists; the
+    // template is the canonical valid state, so copy it into the isolated HOME.
+    mkdirSync(join(home, '.claude'), { recursive: true });
+    copyFileSync(STATE_TEMPLATE, join(home, '.claude', 'linkedin-studio.local.md'));
+
+    if (captures) {
+      mkdirSync(join(data, 'trends'), { recursive: true });
+      writeFileSync(
+        join(data, 'trends', 'trends.json'),
+        JSON.stringify({ schemaVersion: 1, trends: captures }),
+      );
+    }
+
+    const stdout = execFileSync('node', [hookPath], {
+      input: '',
+      env: { ...process.env, HOME: home, USERPROFILE: home, LINKEDIN_STUDIO_DATA: data },
+      encoding: 'utf-8',
+    });
+    return JSON.parse(stdout).hookSpecificOutput.additionalContext;
+  } finally {
+    rmSync(home, { recursive: true, force: true });
+    rmSync(data, { recursive: true, force: true });
+  }
+}
+
+const trend = (capturedAt) => ({
+  id: 't' + capturedAt,
+  title: 'Some trend ' + capturedAt,
+  url: 'https://example.com/' + capturedAt,
+  source: 'tavily',
+  capturedAt,
+  topics: ['x'],
+});
+
+describe('session-start — trend-store staleness nudge (B-S3)', () => {
+  test('fires when newest capture is >=7 days old', () => {
+    const ctx = runHook({ captures: [trend('2026-01-01'), trend(isoDaysAgo(10))] });
+    assert.ok(ctx.includes(NUDGE), 'expected the trend-staleness nudge for a 10-day-old store');
+  });
+
+  test('does NOT fire when newest capture is fresh (<7 days)', () => {
+    const ctx = runHook({ captures: [trend(isoDaysAgo(2))] });
+    assert.ok(!ctx.includes(NUDGE), 'a 2-day-old store must not trigger the nudge');
+  });
+
+  test('does NOT fire (and does not crash) when the store is absent/empty', () => {
+    const absent = runHook({ captures: null });
+    assert.ok(!absent.includes(NUDGE), 'no store => no nudge');
+    const empty = runHook({ captures: [] });
+    assert.ok(!empty.includes(NUDGE), 'empty store => no nudge (never-scanned user is never nagged)');
+  });
+});
diff --git a/hooks/scripts/session-start.mjs b/hooks/scripts/session-start.mjs
index 09fa0d9..04d3be1 100644
--- a/hooks/scripts/session-start.mjs
+++ b/hooks/scripts/session-start.mjs
@@ -29,6 +29,28 @@ function daysSince(dateStr) {
   return Math.floor((Date.now() - epoch) / 86400000);
 }
 
+// B-S3: newest trend capture (ISO date) from the persistent trend store, read
+// as raw JSON. The hook must NOT spawn the tsx CLI at session start (slow +
+// needs node_modules/tsx); the store schema (trends[].capturedAt) is stable and
+// versioned, so a direct read is safe. Twin of scripts/trends/src/store.ts:
+// newestCaptureDate (max capturedAt). Returns null when the store is absent,
+// unreadable, or empty — no captures yet ⇒ no nudge.
+function trendsNewestCapture(storePath) {
+  if (!existsSync(storePath)) return null;
+  try {
+    const parsed = JSON.parse(readFileSync(storePath, 'utf-8'));
+    const trends = Array.isArray(parsed?.trends) ? parsed.trends : [];
+    let newest = null;
+    for (const t of trends) {
+      const d = typeof t?.capturedAt === 'string' ? t.capturedAt : null;
+      if (d && (newest === null || d > newest)) newest = d;
+    }
+    return newest;
+  } catch {
+    return null;
+  }
+}
+
 function isoWeek() {
   const d = new Date();
   const dayNum = d.getUTCDay() || 7;
@@ -309,6 +331,16 @@ if (existsSync(STATE_FILE)) {
     reminders += '- No analytics data imported yet. Run /linkedin:import to start tracking performance.\\n';
   }
 
+  // Trend-store staleness (B-S3): warn-only, ≥7 days. Fires ONLY when the store
+  // already holds captures (newest === null ⇒ no nudge), so a never-scanned user
+  // is never nagged. Neutral wording — "scan for trends" hits trend-spotter's own
+  // trigger; no hardcoded beat (de-niche invariant, §17 guard).
+  const newestTrendCapture = trendsNewestCapture(join(getDataRoot('trends'), 'trends.json'));
+  const daysSinceTrend = daysSince(newestTrendCapture);
+  if (daysSinceTrend !== null && daysSinceTrend >= 7) {
+    reminders += `- Trend signals are ${daysSinceTrend} days old. Scan for trends to refresh the digest before planning content.\\n`;
+  }
+
   // Milestone reminders
   if (milestonePhase && followerCount > 0) {
     if (milestoneStatus === 'SIGNIFICANTLY BEHIND') {
diff --git a/scripts/test-runner.sh b/scripts/test-runner.sh
index c8727e7..8ada9a6 100755
--- a/scripts/test-runner.sh
+++ b/scripts/test-runner.sh
@@ -683,7 +683,7 @@ if [ -x "$TR_DIR/node_modules/.bin/tsx" ]; then
   TR_OUT=$( set +e; (cd "$TR_DIR" && npm test) 2>&1; echo "TR_EXIT:$?" )
   TR_EXIT=$(echo "$TR_OUT" | grep -oE 'TR_EXIT:[0-9]+' | grep -oE '[0-9]+' | head -1)
   TR_TESTS=$(echo "$TR_OUT" | grep -oE 'tests [0-9]+' | grep -oE '[0-9]+' | tail -1)
-  TRENDS_TESTS_FLOOR=21
+  TRENDS_TESTS_FLOOR=24  # B-S3: +3 newestCaptureDate tests (staleness signal)
   if [ "$TR_EXIT" = "0" ] && [ -n "$TR_TESTS" ] && [ "$TR_TESTS" -ge "$TRENDS_TESTS_FLOOR" ]; then
     pass "trends-store suite green: $TR_TESTS tests pass (floor $TRENDS_TESTS_FLOOR)"
   else
diff --git a/scripts/trends/src/cli.ts b/scripts/trends/src/cli.ts
index 001e791..73f42c6 100644
--- a/scripts/trends/src/cli.ts
+++ b/scripts/trends/src/cli.ts
@@ -6,6 +6,7 @@
  *                                       [--source <s>] [--summary "<s>"] [--store <path>]
  *   node --import tsx src/cli.ts query --topics <a,b>  [--store <path>] [--json]
  *   node --import tsx src/cli.ts list   [--since <YYYY-MM-DD>] [--limit <n>] [--store <path>] [--json]
+ *   node --import tsx src/cli.ts status [--store <path>] [--json]
  *
  * The capture agent (research-engine) calls `add` to fold a freshly-polled trend
  * into the store, and `query`/`list` to reason over accumulated history. The
@@ -19,6 +20,7 @@ import {
   defaultStorePath,
   history,
   loadStore,
+  newestCaptureDate,
   queryByTopic,
   saveStore,
 } from "./store.js";
@@ -55,7 +57,8 @@ function usage(msg: string): never {
     "usage:\n" +
       '  add --title "<t>" --url "<u>" --topics <a,b> [--source <s>] [--summary "<s>"] [--store <path>]\n' +
       "  query --topics <a,b> [--store <path>] [--json]\n" +
-      "  list [--since <YYYY-MM-DD>] [--limit <n>] [--store <path>] [--json]",
+      "  list [--since <YYYY-MM-DD>] [--limit <n>] [--store <path>] [--json]\n" +
+      "  status [--store <path>] [--json]",
   );
   process.exit(2);
 }
@@ -64,6 +67,11 @@ function today(): string {
   return new Date().toISOString().slice(0, 10);
 }
 
+/** Whole days from one ISO date to another (floor); negative if `from` is later. */
+function daysBetween(fromIso: string, toIso: string): number {
+  return Math.floor((new Date(toIso).getTime() - new Date(fromIso).getTime()) / 86400000);
+}
+
 function main(): void {
   const [command, ...rest] = process.argv.slice(2);
   const flags = parseFlags(rest);
@@ -140,6 +148,24 @@ function main(): void {
     return;
   }
 
+  if (command === "status") {
+    const store = loadStore(storePath);
+    const newest = newestCaptureDate(store);
+    const daysStale = newest === null ? null : daysBetween(newest, today());
+    if (asJson) {
+      console.log(JSON.stringify({ store: storePath, count: store.trends.length, newest, daysStale }));
+      return;
+    }
+    console.log(`Store: ${storePath}`);
+    console.log(`  trends: ${store.trends.length}`);
+    if (newest === null) {
+      console.log("  newest: — (empty store; no captures yet)");
+    } else {
+      console.log(`  newest: ${newest} (${daysStale}d ago)`);
+    }
+    return;
+  }
+
   usage(command ? `unknown command: ${command}` : "no command given");
 }
 
diff --git a/scripts/trends/src/store.ts b/scripts/trends/src/store.ts
index d80c070..52d359f 100644
--- a/scripts/trends/src/store.ts
+++ b/scripts/trends/src/store.ts
@@ -161,6 +161,17 @@ export function history(store: TrendStore, opts: HistoryOptions = {}): TrendReco
   return out;
 }
 
+/**
+ * The most recent capturedAt across the store (ISO date), or null when the
+ * store is empty. The staleness signal behind the SessionStart trend-freshness
+ * nudge (B-S3) and the `status` CLI subcommand: reuses history()'s newest-first
+ * ordering so the module has a single notion of "newest". Pure — the days-stale
+ * arithmetic (needs "today") lives in the caller, not here.
+ */
+export function newestCaptureDate(store: TrendStore): string | null {
+  return history(store, { limit: 1 })[0]?.capturedAt ?? null;
+}
+
 /**
  * Default store path under the per-user data dir (M0 data-path convention), so
  * the trend history survives plugin upgrades/reinstalls. `LINKEDIN_STUDIO_DATA`
diff --git a/scripts/trends/tests/store.test.ts b/scripts/trends/tests/store.test.ts
index 80a0932..a149329 100644
--- a/scripts/trends/tests/store.test.ts
+++ b/scripts/trends/tests/store.test.ts
@@ -13,6 +13,7 @@ import {
   addTrend,
   queryByTopic,
   history,
+  newestCaptureDate,
 } from "../src/store.js";
 import { SCHEMA_VERSION } from "../src/types.js";
 import type { TrendStore } from "../src/types.js";
@@ -294,4 +295,39 @@ describe("trends store", () => {
       assert.deepEqual(h.map((t) => t.title), ["Newest"]);
     });
   });
+
+  describe("newestCaptureDate (B-S3 staleness signal)", () => {
+    test("empty store → null (no captures yet → no nudge)", () => {
+      assert.equal(newestCaptureDate(emptyStore()), null);
+    });
+
+    test("single trend → its capturedAt", () => {
+      const store = addTrend(emptyStore(), {
+        title: "Solo",
+        url: "https://example.com/solo",
+        source: "tavily",
+        capturedAt: "2026-06-05",
+        topics: ["x"],
+      }).store;
+      assert.equal(newestCaptureDate(store), "2026-06-05");
+    });
+
+    test("multiple trends → the max (newest) capturedAt, regardless of insertion order", () => {
+      let store = emptyStore();
+      for (const [title, capturedAt] of [
+        ["Middle", "2026-05-01"],
+        ["Newest", "2026-06-01"],
+        ["Oldest", "2026-04-01"],
+      ] as const) {
+        store = addTrend(store, {
+          title,
+          url: `https://example.com/${title}`,
+          source: "tavily",
+          capturedAt,
+          topics: ["x"],
+        }).store;
+      }
+      assert.equal(newestCaptureDate(store), "2026-06-01");
+    });
+  });
 });