A face or cover photo whose host has lost the file is found on another server that holds the same blob. "No avatar for karnage?" (Adam, 2026-11-02): his kind 0 names a picture and a banner on media.21media.to, and that host answers "The requested blob was not found" for both — while blossom.primal.net, the server he publishes in his kind 10063, still has them, which is why other clients show his face. A picture named by its sha256 is a Blossom blob, served under the same name by any server holding the bytes: when the thumbnail maker finds the host without it (a 404, or a host that won't answer), the blob is looked for on the person's published servers and then the public ones we know, asked together, and the first that answers stands in — the thumbnail is made from it, the profile page's big face and banner paint from it, the feed's warm-up loads it — and the find is remembered on the device so the search runs once. tools/blob-alt-test.js serves a dead host and a published server holding the copies and checks the thumbnail, the profile page and the post rows

Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_01VMan6TFgisGKUDhdStLUvs

1 files changed, 94 insertions, 8 deletions

diff --git a/src/features/messages.js b/src/features/messages.js
index e3cdc8d..fb9a9d6 100644
--- a/src/features/messages.js
+++ b/src/features/messages.js
@@ -1019,6 +1019,68 @@ export function messagesFeature(ctx) {
       }
     }
   }
+  // ---- a Blossom blob gone from its host, found on another ---------------
+  // A picture named by its sha256 (…/<64 hex>.jpg) is a Blossom blob: any
+  // server holding the same bytes serves them under the same name. When the
+  // host in the URL no longer has it — Karnage's face and banner on
+  // media.21media.to answered "blob not found" (2026-11-02) while
+  // blossom.primal.net, the server he publishes in his kind 10063, still had
+  // both — the picture is looked for on the servers the person published
+  // and then on the public ones we know, and the first that answers stands
+  // in for it: the thumbnail is made from it, the big face and the banner
+  // paint from it. Remembered on the device, so the search runs once.
+  const BLOB_RE = /^(https?:\/\/[^/?#]+)(?:\/[^?#]*)?\/([0-9a-f]{64})(\.[a-z0-9]{2,5})?(?:[?#].*)?$/i;
+  const BLOB_ALT_HOSTS = ['https://blossom.primal.net', 'https://blossom.ditto.pub', 'https://nostr.download',
+    'https://blossom.nostr.build', 'https://blossom.band', 'https://cdn.satellite.earth'];
+  const BLOB_ALT_KEY = 'btc-wallet-blob-alts';
+  const blobAlts = new Map(); // url -> the copy that answered, or null when none did
+  (() => { try { for (const [k, v] of Object.entries(JSON.parse(localStorage.getItem(BLOB_ALT_KEY) || '{}'))) if (typeof v === 'string') blobAlts.set(k, v); } catch {} })();
+  const saveBlobAlts = () => {
+    try {
+      const found = [...blobAlts].filter(([, v]) => v).slice(-200);
+      localStorage.setItem(BLOB_ALT_KEY, JSON.stringify(Object.fromEntries(found)));
+    } catch {}
+  };
+  const blobProbing = new Map();
+  const blobAltOf = (url) => (url && blobAlts.get(url)) || null;
+  // the servers a person publishes for their files (BUD-03), asked only when
+  // one of their pictures has gone missing
+  const blobServersOf = async (pk) => {
+    try {
+      const evs = await queryOn(PROFILE_RELAYS, { kinds: [10063], authors: [pk], limit: 1 }, 4000);
+      const ev = (evs || []).sort((a, b) => b.created_at - a.created_at)[0];
+      return ev ? ev.tags.filter((x) => x[0] === 'server' && /^(https:\/\/|http:\/\/localhost(:\d+)?\/)/i.test(x[1] || ''))
+        .map((x) => x[1].replace(/\/+$/, '')) : [];
+    } catch { return []; }
+  };
+  // does an <img> load from here? (no CORS needed to find out)
+  const imageAnswers = (url, ms = 8000) => new Promise((resolve) => {
+    const im = new Image();
+    const timer = setTimeout(() => { im.onload = im.onerror = null; im.src = ''; resolve(false); }, ms);
+    im.onload = () => { clearTimeout(timer); resolve(true); };
+    im.onerror = () => { clearTimeout(timer); resolve(false); };
+    im.src = url;
+  });
+  function findBlobAlt(url, pk) {
+    if (blobAlts.has(url)) return Promise.resolve(blobAlts.get(url));
+    if (blobProbing.has(url)) return blobProbing.get(url);
+    const m = BLOB_RE.exec(url || '');
+    if (!m || typeof Image === 'undefined') return Promise.resolve(null);
+    const task = (async () => {
+      const origin = m[1].toLowerCase(), name = m[2] + (m[3] || '');
+      const hosts = [...new Set([...(pk ? await blobServersOf(pk) : []), ...BLOB_ALT_HOSTS])]
+        .filter((h) => h.toLowerCase() !== origin);
+      // asked together (a host that hangs mustn't hold the rest), the
+      // person's own servers preferred among those that answer
+      const answers = await Promise.all(hosts.map((h) => imageAnswers(h + '/' + name).then((ok) => (ok ? h + '/' + name : null))));
+      const alt = answers.find(Boolean) || null;
+      blobAlts.set(url, alt);
+      if (alt) saveBlobAlts();
+      return alt;
+    })().finally(() => blobProbing.delete(url));
+    blobProbing.set(url, task);
+    return task;
+  }
   function makeThumb(pk, p) {
     if (!p || !p.picture || typeof document === 'undefined') return;
     if (noCorsHost(p.picture)) return; // a host that won't hand over bytes; the <img> shows it anyway
@@ -1075,8 +1137,20 @@ export function messagesFeature(ctx) {
         // the browser's cache is welcome: the face was just painted from this
         // very URL, and 'reload' re-downloaded every original (38 MB in one
         // scroll) — a stale copy still makes a fine thumbnail
-        const res = await corsFetch(url, AbortSignal.timeout(THUMB_SLOW));
-        if (!res.ok) throw new Error('http ' + res.status);
+        let res = null;
+        try { res = await corsFetch(url, AbortSignal.timeout(THUMB_SLOW)); } catch (e) {
+          if (e && e.corsRefused) noteNoCors(url);
+          if (!BLOB_RE.test(url)) throw e;
+        }
+        // the host no longer has it (or won't answer): the same blob on
+        // another server is as good — and the face it paints is this one
+        if (!res || !res.ok) {
+          const alt = BLOB_RE.test(url) ? await findBlobAlt(url, pk) : null;
+          if (!alt) throw new Error('http ' + (res ? res.status : 'none'));
+          res = await corsFetch(alt, AbortSignal.timeout(THUMB_SLOW));
+          if (!res.ok) throw new Error('http ' + res.status);
+          scheduleRepaint(); // the big face, where one is up, can paint from the copy now
+        }
         bmp = await createImageBitmap(await res.blob());
         // centre-crop to a square, the way background-size:cover paints it
         const side = Math.min(bmp.width, bmp.height);
@@ -3857,8 +3931,9 @@ export function messagesFeature(ctx) {
     const punk = localPunk(p.picture, big);
     if (punk) return `url(${JSON.stringify(punk)})`;
     const local = p.thumb && p.thumbFor === p.picture ? p.thumb : null;
-    if (!local) return `url(${JSON.stringify(p.picture)})`;
-    return (big ? `url(${JSON.stringify(p.picture)}),` : '') + `url(${JSON.stringify(local)})`;
+    const pic = blobAltOf(p.picture) || p.picture; // the same blob elsewhere, when the host lost it
+    if (!local) return `url(${JSON.stringify(pic)})`;
+    return (big ? `url(${JSON.stringify(pic)}),` : '') + `url(${JSON.stringify(local)})`;
   }
 
   const FACE_WAIT_MS = 1000;
@@ -4064,7 +4139,17 @@ export function messagesFeature(ctx) {
   };
   function warmBanner(pk) {
     const b = bannerOf(pk);
-    if (b && !mediaReady.has(b)) return warmMedia(b, { thumb: true }).then(() => scheduleRepaint());
+    if (!b) return;
+    const shown = blobAltOf(b) || b;
+    if (mediaReady.has(shown)) return;
+    return warmMedia(shown, { thumb: true }).then(async () => {
+      // the host lost it: the same blob on another server paints instead
+      if (!mediaReady.has(shown) && shown === b && BLOB_RE.test(b)) {
+        const alt = await findBlobAlt(b, pk);
+        if (alt) await warmMedia(alt, { thumb: true });
+      }
+      scheduleRepaint();
+    });
   }
   function prefetchProfilePage(pk) {
     if (!pk || prefetched.has(pk)) return;
@@ -7100,7 +7185,7 @@ export function messagesFeature(ctx) {
     return urls;
   }
   const avatarUrl = (p, pk) => p?.picture
-    ? localPunk(p.picture) || (p.thumbFor === p.picture && p.thumb) || p.picture
+    ? localPunk(p.picture) || (p.thumbFor === p.picture && p.thumb) || blobAltOf(p.picture) || p.picture
     : punkSmallUrl(pk);
   async function warmAvatar(pk, deadline) {
     let p = liveProfileOf(pk);
@@ -13329,7 +13414,8 @@ export function messagesFeature(ctx) {
       // doesn't drop by the height of a cover photo when it arrives
       : urlish(lp.banner);
     const draftPic = draft && urlish(draft.picture);
-    if (bannerUrl && !draft && !mediaReady.has(bannerUrl)) warmBanner(pk);
+    const bannerShown = bannerUrl && !draft ? blobAltOf(bannerUrl) || bannerUrl : bannerUrl;
+    if (bannerUrl && !draft && !mediaReady.has(bannerShown)) warmBanner(pk);
     return h('div', { class: 'col', style: 'gap:16px' },
       // full header on profiles too — losing the search button here made
       // finding the NEXT person a trek back home
@@ -13338,7 +13424,7 @@ export function messagesFeature(ctx) {
         t(full || lp.eventAt || lp.name || lp.picture ? 'profFetchFailed' : 'profNotFound'),
         h('button', { class: 'btn-sm', onClick: () => { fetchFullProfile(pk); render(); } }, t('retry'))) : null,
       h('div', { class: 'card col', style: 'gap:12px' },
-        bannerUrl ? h('div', { class: 'profile-banner', style: `background-image:url(${JSON.stringify(draft ? bannerUrl : mediaSrc(bannerUrl, mediaReady.get(bannerUrl)))})` }) : null,
+        bannerUrl ? h('div', { class: 'profile-banner', style: `background-image:url(${JSON.stringify(draft ? bannerUrl : mediaSrc(bannerShown, mediaReady.get(bannerShown)))})` }) : null,
         h('div', { class: 'row gap6', style: 'align-items:center' },
           draftPic
             ? h('div', { class: 'chat-avatar profile-avatar ava-img', style: `background-image:url(${JSON.stringify(draftPic)})` })