Allow explicit retry of failed native preview preparation

apps/desktop/src/main.ts

@@ -264,9 +264,21 @@ const mediaLane = new LatestLane<PreviewRequest>(
   (request) => previewRevision.accepts(request.revision),
   (request, error) => {
     if (!previewRevision.accepts(request.revision)) return;
-    element("media-preview-status").hidden = false;
+    const status = element("media-preview-status");
-    element("media-preview-status").textContent =
+    status.hidden = false;
-      `Preview unavailable: ${String(error)}. Use Open file.`;
+    status.textContent = `Preview unavailable: ${String(error)}. Use Open file.`;
+    const retry = document.createElement("button");
+    retry.type = "button";
+    retry.textContent = "Retry preview";
+    retry.addEventListener("click", () => {
+      const revision = previewRevision.retry(request.revision);
+      if (revision === undefined) return;
+      unloadMedia();
+      status.hidden = false;
+      status.textContent = "Preparing media preview…";
+      mediaLane.submit({ revision, result: request.result });
+    });
+    status.append(" ", retry);
   },
 );
 let displayedRequestId: number | null = null;

apps/desktop/src/media-display.ts

@@ -98,6 +98,10 @@ export class PreviewRevision {
   accepts(revision: number) {
     return revision === this.revision && this.key !== "";
   }
+  retry(revision: number): number | undefined {
+    if (!this.accepts(revision)) return undefined;
+    return ++this.revision;
+  }
   clear() {
     this.key = "";
     this.revision++;

apps/desktop/tests/media-display.test.mjs

@@ -11,6 +11,18 @@ import {
 import { LatestLane } from "../src/search-state.ts";
 const settle = () => new Promise((resolve) => setImmediate(resolve));
 
+test("explicit preview retry invalidates old work and cannot retry a stale selection", () => {
+  const state = new PreviewRevision();
+  const first = state.select("first");
+  const retried = state.retry(first.revision);
+  assert.equal(typeof retried, "number");
+  assert.equal(state.accepts(first.revision), false);
+  assert.equal(state.accepts(retried), true);
+  assert.equal(state.retry(first.revision), undefined);
+  state.select("second");
+  assert.equal(state.retry(retried), undefined);
+});
+
 test("indexed content refresh invalidates a decoded preview at the same path", () => {
   const revision = new PreviewRevision();
   const source = { kind: "timestamp_ms", number: 1200 };

docs/MEDIA-PREVIEW.md

@@ -19,6 +19,10 @@ Arbitrary paths, remote URLs, query strings and traversal are not preview grants
 The generic Tauri asset protocol is disabled in the new configuration.
 Index-change notifications also advance the preview selection identity, so a
 same-path image/recording reloads rather than retaining previously decoded media.
+Failed native preview preparation now offers an explicit **Retry preview**
+button. It invalidates the old request revision and cannot restart a selection
+that has since changed. There is no automatic retry loop. The added regression
+passed with all 60 frontend tests, formatting and the production frontend build.
 
 This does not hash every recording on every request. A same-size/mtime in-place
 write may remain undetected until a filesystem hint or byte-verifying rescan