Switching feeds paints posts at once instead of a spinner while the relays answer.

The disk cache held four feeds, so with more chips than that (or one never
opened here) a switch opened on nothing. Now:
- up to twelve feeds on disk: the four read last keep a page of 30, the
  rest 5 seed posts (same 256 KB budget);
- once the feed on screen settles, every other feed with nothing on disk
  has its first posts fetched ahead, one small request each, every 15 min;
- a feed with nothing on disk borrows matching posts (its people, its
  topics) that open feeds already hold.

tools/feed-switch-seed-test.js: with 8 s relays, a fetched-ahead feed and a
never-opened topic feed both paint rows at once (fails on the old code).

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01WMMwWYJkPQxLgfMsY7hWcU

4 files changed, 210 insertions, 15 deletions

diff --git a/src/features/messages.js b/src/features/messages.js
index 2f4446e..856a4bd 100644
--- a/src/features/messages.js
+++ b/src/features/messages.js
@@ -31,7 +31,7 @@ import {
 import { saveInbox } from '../dm-inbox.js';
 import { mergeFeedWindow } from '../feed-window.js';
 import { createThreadStore } from '../thread-cache.js';
-import { createFeedCache, FEED_CACHE_POSTS } from '../feed-cache.js';
+import { createFeedCache, FEED_CACHE_POSTS, FEED_SEED_POSTS } from '../feed-cache.js';
 import { makeSearcher, resultRows, fallbackAvatar, warmSearch, punkImageUrl, punkSmallUrl } from '../recipient-search.js';
 import { getNetwork } from '../api.js';
 import { decodeBolt11 } from '../ark/lightning.js';
@@ -4356,6 +4356,7 @@ export function messagesFeature(ctx) {
       let stored = [];
       try { stored = feedDisk()?.read(curFeedId) || wallet.loadFeatureState(feedCacheKey(curFeedId), []) || []; } catch {}
       if (!Array.isArray(stored)) stored = [];
+      if (!stored.length) stored = borrowedNotes(feedDef(curFeedId));
       stored = stored.slice(0, FEED_STORE);
       c = { id: curFeedId, status: 'loading', notes: stored, shown: FEED_PAGE, at: 0, booting: true, presentations: new Map() };
       feedStates.set(curFeedId, c);
@@ -4401,10 +4402,46 @@ export function messagesFeature(ctx) {
     } catch {} finally {
       if (!c.stopped) {
         c.status = 'ready';
-        if (c === feed && ui.chatOpen && ui.msgView === 'feed') { scheduleRepaint(); watchFeed(); }
+        if (c === feed && ui.chatOpen && ui.msgView === 'feed') { scheduleRepaint(); watchFeed(); seedOtherFeeds(); }
       }
     }
   }
+  // A feed never opened on this device (or pushed out of the disk cache)
+  // would open on a bare spinner. Posts another open feed already holds —
+  // by its people, on its topics — stand in until the relays answer.
+  function borrowedNotes(def) {
+    if (!def || def.all) return [];
+    const authors = new Set(feedAuthors(def)), topics = new Set(feedTopics(def));
+    if (!authors.size && !topics.size) return [];
+    const fits = (e) => (!authors.size || authors.has(e.pubkey))
+      && (!topics.size || (e.tags || []).some((x) => x[0] === 't' && topics.has(normTopic(x[1]))));
+    const seen = new Set(), out = [];
+    for (const o of feedStates.values()) {
+      for (const e of o.notes) if (!seen.has(e.id) && fits(e) && !hidden(e)) { seen.add(e.id); out.push(e); }
+    }
+    return out.sort((a, b) => b.created_at - a.created_at).slice(0, FEED_PAGE);
+  }
+  // And once the feed on screen has settled, the other feeds' first few
+  // posts are fetched ahead into the disk cache, one feed at a time, so
+  // switching to any of them paints at once.
+  const SEED_EVERY = 15 * 60_000;
+  let feedsSeededAt = 0;
+  async function seedOtherFeeds() {
+    const disk = feedDisk();
+    if (!disk || isVisitor() || Date.now() - feedsSeededAt < SEED_EVERY) return;
+    feedsSeededAt = Date.now();
+    for (const def of feedList()) {
+      if (def.curated || def.of || feedStates.has(def.id) || disk.has(def.id)) continue;
+      const authors = feedAuthors(def).slice(0, REQ_AUTHORS), topics = feedTopics(def);
+      if (!authors.length && !topics.length) continue;
+      try {
+        const events = await queryOn(feedRelaysOr(def, NOTE_RELAYS), { kinds: FEED_KINDS, limit: FEED_SEED_POSTS * 2,
+          ...(authors.length ? { authors } : {}), ...(topics.length ? { '#t': topics } : {}) }, 3000);
+        if (feedStates.has(def.id)) continue; // opened while we were asking
+        disk.seed(def.id, events.filter((e) => FEED_KINDS.includes(e.kind) && !isReply(e) && !hidden(e)));
+      } catch {}
+    }
+  }
   // Make a feed the current one (no paint): Back/Forward through the
   // history restores ui.feedId and the view catches up from here.
   function selectFeed(id) {
diff --git a/src/feed-cache.js b/src/feed-cache.js
index 7394393..2c0b153 100644
--- a/src/feed-cache.js
+++ b/src/feed-cache.js
@@ -1,17 +1,20 @@
 // Disposable public feed cache. Budget is conservative UTF-16 storage bytes.
+// The feeds read most recently keep a full page; the rest keep a few seed
+// posts, so switching to any feed paints something before the relays answer.
 export const FEED_CACHE_POSTS = 30;
-const MAX_FEEDS = 4, MAX_UNITS = 256_000, MAX_AGE = 7 * 86400_000;
+export const FEED_SEED_POSTS = 5;
+const FULL_FEEDS = 4, MAX_FEEDS = 12, MAX_UNITS = 256_000, MAX_AGE = 7 * 86400_000;
 export function createFeedCache(storage, prefix, now = Date.now) {
   const keyOf = (id) => id === 'following' ? prefix : prefix + ':' + id;
   const valid = (e) => (e?.kind === 1 || e?.kind === 1068) && typeof e.id === 'string' && typeof e.pubkey === 'string'
     && typeof e.content === 'string' && Number.isFinite(e.created_at) && Array.isArray(e.tags);
-  function compact(notes) {
+  function compact(notes, max = FEED_CACHE_POSTS) {
     const kept = []; let size = 0;
     for (const e of (Array.isArray(notes) ? notes : []).filter(valid).sort((a, b) => b.created_at - a.created_at)) {
       const cost = JSON.stringify(e).length;
       if (size + cost > MAX_UNITS - 1000) continue;
       kept.push(e); size += cost;
-      if (kept.length === FEED_CACHE_POSTS) break;
+      if (kept.length === max) break;
     }
     return kept;
   }
@@ -23,19 +26,24 @@ export function createFeedCache(storage, prefix, now = Date.now) {
       try {
         const text = storage.getItem(key);
         const raw = JSON.parse(text);
-        const entry = Array.isArray(raw) ? { at: now(), notes: compact(raw) } : raw;
+        const entry = Array.isArray(raw) ? { at: now(), notes: raw } : raw;
         if (!entry || !Number.isFinite(entry.at) || now() - entry.at > MAX_AGE) entries.push({ key });
-        else entries.push({ key, text, value: { at: entry.at, notes: compact(entry.notes) } });
+        else entries.push({ key, text, entry });
       } catch { entries.push({ key }); }
     }
-    entries.sort((a, b) => (b.key === preferred) - (a.key === preferred) || (b.value?.at || 0) - (a.value?.at || 0));
+    // A feed that was read beats one only warmed in the background (seed).
+    entries.sort((a, b) => (b.key === preferred) - (a.key === preferred)
+      || (!a.entry?.seed) - (!b.entry?.seed) || (b.entry?.at || 0) - (a.entry?.at || 0));
     let units = 0, count = 0;
     for (const e of entries) {
-      const json = e.value && JSON.stringify(e.value);
+      const max = count < FULL_FEEDS && !e.entry?.seed ? FEED_CACHE_POSTS : FEED_SEED_POSTS;
+      const value = e.entry && { at: e.entry.at, notes: compact(e.entry.notes, max), ...(e.entry.seed ? { seed: true } : {}) };
+      const json = value && JSON.stringify(value);
       if (!json || count >= MAX_FEEDS || units + json.length > MAX_UNITS) storage.removeItem(e.key);
       else { if (e.text !== json) storage.setItem(e.key, json); units += json.length; count++; }
     }
   }
+  const peek = (id) => { try { return JSON.parse(storage.getItem(keyOf(id)) || 'null'); } catch { return null; } };
   return {
     read(id) {
       try {
@@ -49,5 +57,16 @@ export function createFeedCache(storage, prefix, now = Date.now) {
     save(id, notes) {
       try { storage.setItem(keyOf(id), JSON.stringify({ at: now(), notes: compact(notes) })); sweep(keyOf(id)); } catch {}
     },
+    // Whether a feed already has posts on disk (without counting as a read).
+    has: (id) => !!peek(id)?.notes?.length,
+    // A few posts fetched ahead for a feed not yet opened. Never replaces
+    // posts a read left behind, and ranks below every feed that was read.
+    seed(id, notes) {
+      try {
+        if (peek(id)?.notes?.length) return;
+        storage.setItem(keyOf(id), JSON.stringify({ at: now(), seed: true, notes: compact(notes, FEED_SEED_POSTS) }));
+        sweep(null);
+      } catch {}
+    },
   };
 }
diff --git a/tools/feed-cache-test.js b/tools/feed-cache-test.js
index 995e01a..3df9447 100644
--- a/tools/feed-cache-test.js
+++ b/tools/feed-cache-test.js
@@ -12,14 +12,28 @@ storage.setItem('wallet:funds', 'untouched');
 assert.equal(cache.read('following').length, 30);
 assert.equal(JSON.parse(storage.getItem('wallet:feedNotes')).notes.length, 30);
 for (let i = 0; i < 5; i++) cache.save('custom' + i, notes);
-assert.equal(cache.read('following').length, 0);
-assert.equal([...values.keys()].filter((k) => k.includes('feedNotes')).length, 4);
-cache.read('custom1');
-cache.save('custom5', notes);
-assert.equal(cache.read('custom2').length, 0);
+const stored = (id) => JSON.parse(storage.getItem(id === 'following' ? 'wallet:feedNotes' : 'wallet:feedNotes:' + id) || 'null');
+assert.equal(stored('following').notes.length, 5, 'a feed past the four most recent keeps seed posts');
+assert.equal(stored('custom4').notes.length, 30);
+assert.equal(cache.read('following').length, 5, 'and reads them back');
+for (let i = 5; i < 14; i++) cache.save('custom' + i, notes);
+assert.equal([...values.keys()].filter((k) => k.includes('feedNotes')).length, 12);
+assert.equal(stored('custom0'), null, 'the least recently read goes first');
+assert.equal(stored('custom3').notes.length, 5);
+cache.read('custom3'); cache.save('custom3', notes);
+assert.equal(stored('custom3').notes.length, 30, 'reopened, it gets a full page again');
+assert.equal(stored('custom10').notes.length, 5, 'and the oldest of the four drops to seed posts');
+// seeds warmed ahead never outrank or overwrite a feed that was read
+cache.seed('custom13', notes.slice(0, 2));
+assert.equal(stored('custom13').notes.length, 30);
+assert.equal(cache.has('warm'), false);
+cache.seed('warm', notes);
+assert.equal(cache.has('warm'), true);
+assert.equal(stored('warm').notes.length, 5);
+assert.equal(stored('custom13').notes.length, 30);
 cache.save('big', notes.map((e) => ({ ...e, content: 'x'.repeat(15000) })));
 assert([...values].filter(([k]) => k.includes('feedNotes')).reduce((n, [, v]) => n + v.length, 0) <= 256000);
 time += 8 * 86400_000;
 assert.equal(cache.read('big').length, 0);
 assert.equal(storage.getItem('wallet:funds'), 'untouched');
-console.log('✓ legacy caches shrink; 30 posts/feed, four feeds, byte budget, LRU and seven-day expiry enforced');
+console.log('✓ legacy caches shrink; 30 posts for the four most recent feeds, 5 seed posts for up to 12, byte budget, LRU and seven-day expiry enforced');
diff --git a/tools/feed-switch-seed-test.js b/tools/feed-switch-seed-test.js
new file mode 100644
index 0000000..a012dfe
--- /dev/null
+++ b/tools/feed-switch-seed-test.js
@@ -0,0 +1,125 @@
+// Switching to a feed paints posts at once, never a bare spinner, even when
+// the relays are slow: a feed that was never opened borrows matching posts
+// other open feeds already hold, and once the feed on screen settles the
+// other feeds' first posts are fetched ahead into the disk cache.
+// Run: bun tools/feed-switch-seed-test.js
+import puppeteer from 'puppeteer-core';
+import { cacheKeyFor } from '../src/wallet.js';
+import { generateSecretKey, getPublicKey, finalizeEvent } from 'nostr-tools/pure';
+import { buildHtml } from '../build.js';
+const sleep = (ms) => new Promise((r) => setTimeout(r, ms));
+let ok = true;
+const check = (n, c, d = '') => { console.log(` ${c ? '✓' : '✗'} ${n}${d ? ' — ' + d : ''}`); if (!c) ok = false; };
+const A = generateSecretKey(), B = generateSecretKey();
+const PK_A = getPublicKey(A), PK_B = getPublicKey(B);
+const now = Math.floor(Date.now() / 1000);
+const post = (sk, i, content, tags = []) => finalizeEvent({ kind: 1, created_at: now - 100 - i * 60, tags, content }, sk);
+// Alice is followed; one of her posts is on #bitcoin. Bob is only in his own feed.
+const alice = Array.from({ length: 12 }, (_, i) => post(A, i, 'alice post ' + (i + 1), i === 3 ? [['t', 'bitcoin']] : []));
+const bob = Array.from({ length: 12 }, (_, i) => post(B, i, 'bob post ' + (i + 1)));
+
+const html = await buildHtml({ minify: true, pwa: false });
+const server = Bun.serve({ port: 0, fetch: (req) => {
+  const path = new URL(req.url).pathname;
+  if (path.startsWith('/punks') || path === '/verify-worker.js') return new Response(Bun.file('dist' + path));
+  return new Response(html, { headers: { 'content-type': 'text/html' } });
+} });
+const browser = await puppeteer.launch({ executablePath: process.env.CHROME || '/usr/bin/google-chrome', headless: 'new', args: ['--no-sandbox'] });
+const page = await browser.newPage();
+// Stub relay: kind-1 requests answered from the posts above, by author and
+// (for topics) never — until window.__slow, when every answer takes 8 s.
+await page.evaluateOnNewDocument((all) => {
+  const Real = window.WebSocket;
+  window.__reqs = [];
+  window.WebSocket = function (...a) {
+    const ws = new Real(...a);
+    const send = ws.send.bind(ws);
+    ws.send = (data) => {
+      try {
+        const m = JSON.parse(data);
+        if (m[0] === 'REQ') {
+          const f = m[2] || {};
+          const evs = (f.kinds || []).includes(1) && !f['#e'] && !f.ids && !f['#t'] && f.authors
+            ? all.filter((e) => f.authors.includes(e.pubkey) && (!f.until || e.created_at <= f.until)).slice(0, f.limit || 100) : [];
+          if (f.authors) window.__reqs.push({ authors: f.authors, limit: f.limit, slow: !!window.__slow });
+          setTimeout(() => {
+            for (const e of evs) ws.dispatchEvent(new MessageEvent('message', { data: JSON.stringify(['EVENT', m[1], e]) }));
+            ws.dispatchEvent(new MessageEvent('message', { data: JSON.stringify(['EOSE', m[1]]) }));
+          }, window.__slow ? 8000 : 0);
+          return;
+        }
+        if (m[0] === 'EVENT') return;
+      } catch {}
+      return send(data);
+    };
+    return ws;
+  };
+  window.WebSocket.prototype = Real.prototype; Object.assign(window.WebSocket, Real);
+}, [...alice, ...bob]);
+const errs = [];
+page.on('pageerror', (e) => errs.push(String(e)));
+const click = (t) => page.evaluate((x) => { const e = [...document.querySelectorAll('button')].find((n) => n.textContent.trim().toLowerCase().includes(x)); if (e) { e.click(); return true; } return false; }, t);
+const waitText = async (x, ms = 25000) => { for (let i = 0; i < ms / 250; i++) { if ((await page.evaluate(() => document.body.innerText)).toLowerCase().includes(x)) return true; await sleep(250); } return false; };
+const chip = (name) => page.evaluate((n) => { const e = [...document.querySelectorAll('.feed-chip')].find((b) => b.textContent.trim() === n); if (e) e.click(); return !!e; }, name);
+const rows = () => page.evaluate(() => [...document.querySelectorAll('.notes-feed > .row[data-key]')].map((r) => r.innerText.match(/(alice|bob) post \d+/)?.[0]).filter(Boolean));
+const spinner = () => page.evaluate(() => !document.querySelector('.notes-feed') && !!document.querySelector('.spinner'));
+
+try {
+  await page.setViewport({ width: 390, height: 844 });
+  await page.goto(server.url.href, { waitUntil: 'domcontentloaded' });
+  await page.evaluate(() => localStorage.setItem('btc-wallet-network', 'regtest'));
+  await page.reload({ waitUntil: 'domcontentloaded' }); await sleep(400);
+  await click('create a new wallet'); await sleep(600);
+  await page.waitForSelector('.words .w .t');
+  const mn = (await page.$$eval('.words .w .t', (l) => l.map((e) => e.textContent.trim()))).join(' ');
+  await click('skip verification');
+  await waitText('receive', 20000);
+  const base = cacheKeyFor(mn + '\n');
+  await page.evaluate(([k, a, b, ns]) => {
+    const t = Date.now();
+    localStorage.setItem(k + ':follows', JSON.stringify({ tags: [['p', a]], c: '', at: Math.floor(t / 1000) }));
+    localStorage.setItem(k + ':feedNotes', JSON.stringify(ns));
+    localStorage.setItem(k + ':profiles', JSON.stringify({ [a]: { name: 'Alice', t }, [b]: { name: 'Bob', t } }));
+    const s = JSON.parse(localStorage.getItem(k + ':messages') || '{}');
+    s.feeds = [{ id: 'bob', name: 'Bobfeed', follows: false, authors: [b], topics: [], packs: [] },
+      { id: 'btc', name: 'Btcfeed', follows: false, authors: [], topics: ['bitcoin'], packs: [] }];
+    localStorage.setItem(k + ':messages', JSON.stringify(s));
+    localStorage.setItem('btc-wallet-feed', 'following');
+  }, [base, PK_A, PK_B, alice]);
+  await page.reload({ waitUntil: 'domcontentloaded' });
+  await waitText('receive', 20000);
+  await page.evaluate(() => [...document.querySelectorAll('.app-nav-button, button')].find((b) => b.textContent.trim() === 'Feed')?.click());
+  await page.waitForSelector('.notes-feed', { timeout: 15000 });
+  check('Following opens on its cached posts', (await rows())[0] === 'alice post 1', JSON.stringify((await rows()).slice(0, 2)));
+
+  // the feed on screen settles, then Bob's feed is fetched ahead
+  let seeded = null;
+  for (let i = 0; i < 40 && !seeded; i++) {
+    await sleep(250);
+    seeded = await page.evaluate((k) => JSON.parse(localStorage.getItem(k + ':feedNotes:bob') || 'null'), base);
+  }
+  check('another feed is fetched ahead into the disk cache', seeded?.seed && seeded.notes.length > 0 && seeded.notes.length <= 5,
+    JSON.stringify(seeded && { seed: seeded.seed, n: seeded.notes.length }));
+  check('...with a small request', (await page.evaluate(() => window.__reqs)).some((r) => r.authors.join() === PK_B && r.limit <= 10));
+
+  // from here every relay answer takes 8 s
+  await page.evaluate(() => { window.__slow = true; });
+  check('the Bob chip is there', await chip('Bobfeed'));
+  await sleep(400);
+  const bobRows = await rows();
+  check('switching to a feed fetched ahead paints its posts at once', bobRows[0] === 'bob post 1', JSON.stringify(bobRows.slice(0, 3)));
+  check('...not a spinner', !(await spinner()));
+
+  await chip('Btcfeed');
+  await sleep(400);
+  const btcRows = await rows();
+  check('a topic feed never opened borrows a matching post an open feed holds', btcRows.includes('alice post 4') && btcRows.length === 1, JSON.stringify(btcRows));
+  check('...not a spinner', !(await spinner()));
+  check('no page errors', errs.length === 0, errs.join('; ').slice(0, 300));
+} catch (e) {
+  console.log('✗ threw', e.message); ok = false;
+} finally {
+  await browser.close(); server.stop(true);
+}
+console.log(ok ? '\n✅ feed switching paints at once' : '\n❌ failed');
+process.exit(ok ? 0 : 1);