Generated images survive moves and renames

Agents tidy up folders after generating images (sort into subfolders, rename
revisions); the image records kept the old path, so /api/images/<id>/file
answered 404 and only the requesting device still showed them from its cache.

- Generated images get a copy in the image store (images.blob, kept by the
  blob GC); existing ones are copied once on start-up.
- Records follow: after bash commands with mv/rename (missing images of the
  owner from the last two weeks, found by name or by content hash), when moved
  with the file manager (file or folder), and on access (served from the copy,
  relocated in the background; without a copy found by file name).
- Chat gallery falls back to the preview the model saw when the file is gone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/src/images.rs

@@ -213,6 +213,8 @@ pub async fn generate(app: &App, req: GenerateRequest) -> Result<Vec<ImageRecord
         let name = if images.len() > 1 { format!("{stamp}-{base}-{}.{ext}", i + 1) } else { format!("{stamp}-{base}.{ext}") };
         let path = req.dir.join(name);
         tokio::fs::write(&path, &bytes).await?;
+        // A copy in the image store keeps it viewable when the file is moved or deleted.
+        let blob = app.store.put_blob(&ctype, &bytes).map_err(|e| tracing::warn!("image copy: {e:#}")).ok();
         let rec = ImageRecord {
             id: new_id(),
             user_id: req.user_id.clone(),
@@ -223,6 +225,7 @@ pub async fn generate(app: &App, req: GenerateRequest) -> Result<Vec<ImageRecord
             width: img["width"].as_i64().unwrap_or(0),
             height: img["height"].as_i64().unwrap_or(0),
             created_at: now_ms(),
+            blob,
         };
         app.store.add_image(&rec)?;
         records.push(rec);
@@ -252,6 +255,98 @@ pub async fn generate(app: &App, req: GenerateRequest) -> Result<Vec<ImageRecord
     Ok(records)
 }
 
+/// A generated image whose file is gone: the same file name below its original folder
+/// (or the folder above it), e.g. after an agent sorted the images into subfolders.
+/// Only inside `roots`; looks at a few thousand entries at most.
+pub fn find_moved(path: &Path, roots: &[PathBuf]) -> Option<PathBuf> {
+    let name = path.file_name()?;
+    search_near(path, roots, |p, _| p.file_name() == Some(name))
+}
+
+/// Like `find_moved`, but by content: an image file with the same bytes (renamed).
+pub fn find_by_content(path: &Path, roots: &[PathBuf], hash: &str, size: u64) -> Option<PathBuf> {
+    search_near(path, roots, |p, len| {
+        let ext = p.extension().and_then(|e| e.to_str()).map(|e| e.to_ascii_lowercase());
+        len == size && matches!(ext.as_deref(), Some("png" | "jpg" | "jpeg" | "webp")) && std::fs::read(p).is_ok_and(|b| crate::blobs::hash(&b) == hash)
+    })
+}
+
+/// Files below the folder of `path` and the folder above it (3 levels, hidden folders
+/// skipped, inside `roots`) for which `matches(path, size)` holds.
+fn search_near(path: &Path, roots: &[PathBuf], matches: impl Fn(&Path, u64) -> bool) -> Option<PathBuf> {
+    let dir = path.parent()?;
+    let mut budget = 5000usize;
+    for base in [Some(dir), dir.parent()].into_iter().flatten() {
+        if !roots.iter().any(|r| base.starts_with(r)) {
+            continue;
+        }
+        let mut stack = vec![(base.to_path_buf(), 0usize)];
+        while let Some((d, depth)) = stack.pop() {
+            let Ok(entries) = std::fs::read_dir(&d) else { continue };
+            for e in entries.flatten() {
+                if budget == 0 {
+                    return None;
+                }
+                budget -= 1;
+                let p = e.path();
+                let Ok(ft) = e.file_type() else { continue };
+                if ft.is_file() && p != path && matches(&p, e.metadata().map(|m| m.len()).unwrap_or(0)) {
+                    return Some(p);
+                }
+                let hidden = p.file_name().and_then(|n| n.to_str()).is_some_and(|n| n.starts_with('.') || n == "node_modules");
+                if ft.is_dir() && depth < 3 && !hidden {
+                    stack.push((p, depth + 1));
+                }
+            }
+        }
+    }
+    None
+}
+
+/// Where the file of a generated image is now: by name, then (with a copy in the image
+/// store) by content. Corrects the stored path when found.
+pub fn relocate(app: &App, rec: &ImageRecord) -> Option<PathBuf> {
+    let path = Path::new(&rec.path);
+    let roots = app.user_roots(rec.user_id.as_deref());
+    let found = find_moved(path, &roots).or_else(|| {
+        let hash = rec.blob.as_deref()?;
+        let (_, bytes) = app.store.blob(hash).ok()??;
+        find_by_content(path, &roots, hash, bytes.len() as u64)
+    })?;
+    let _ = app.store.set_image_path(&rec.id, &found.display().to_string());
+    Some(found)
+}
+
+/// After an agent moved or renamed files: find the generated images of `owner` from the
+/// last two weeks whose files are gone and correct their paths. Returns how many.
+pub fn relocate_missing(app: &App, owner: Option<&str>) -> usize {
+    let since = now_ms() - 14 * 86_400_000;
+    let Ok(list) = app.store.images(owner, 500) else { return 0 };
+    list.iter().filter(|r| r.created_at >= since && !Path::new(&r.path).exists()).filter(|r| relocate(app, r).is_some()).count()
+}
+
+/// Copies in the image store for generated images from before they were kept (once per
+/// image, files up to 25 MB): later moves and renames are then found by content.
+pub fn backfill_copies(app: &App) -> Result<usize> {
+    let mut n = 0;
+    for (id, path) in app.store.images_without_copy()? {
+        let Ok(meta) = std::fs::metadata(&path) else { continue };
+        if !meta.is_file() || meta.len() > 25 * 1024 * 1024 {
+            continue;
+        }
+        let Ok(bytes) = std::fs::read(&path) else { continue };
+        let mime = match Path::new(&path).extension().and_then(|e| e.to_str()).map(|e| e.to_ascii_lowercase()).as_deref() {
+            Some("jpg" | "jpeg") => "image/jpeg",
+            Some("webp") => "image/webp",
+            _ => "image/png",
+        };
+        let hash = app.store.put_blob(mime, &bytes)?;
+        app.store.set_image_blob(&id, &hash)?;
+        n += 1;
+    }
+    Ok(n)
+}
+
 /// Downscaled copy for the model's context.
 fn preview_for_model(path: &Path) -> Option<ImageData> {
     let img = image::open(path).ok()?;
@@ -363,6 +458,37 @@ impl Tool for GenerateImage {
 mod tests {
     use super::*;
 
+    #[test]
+    fn finds_moved_files_and_keeps_their_copies() {
+        let dir = std::env::temp_dir().join(format!("cc-img-moved-{}", std::process::id()));
+        let art = dir.join("art");
+        std::fs::create_dir_all(art.join("older")).unwrap();
+        std::fs::write(art.join("older/20261110-a.png"), b"x").unwrap();
+        // Moved into a subfolder: found; renamed or outside the roots: not.
+        assert_eq!(find_moved(&art.join("20261110-a.png"), std::slice::from_ref(&dir)), Some(art.join("older/20261110-a.png")));
+        assert_eq!(find_moved(&art.join("20261110-b.png"), std::slice::from_ref(&dir)), None);
+        assert_eq!(find_moved(&art.join("20261110-a.png"), &[dir.join("elsewhere")]), None);
+        // Renamed: found by content.
+        std::fs::write(art.join("older/level-5.png"), b"renamed bytes").unwrap();
+        let h = crate::blobs::hash(b"renamed bytes");
+        assert_eq!(find_by_content(&art.join("20261110-c.png"), std::slice::from_ref(&dir), &h, 13), Some(art.join("older/level-5.png")));
+        assert_eq!(find_by_content(&art.join("20261110-c.png"), std::slice::from_ref(&dir), &crate::blobs::hash(b"other"), 13), None);
+        // The image store keeps the copy of a generated image.
+        let store = crate::store::Store::open(&dir.join("t.db")).unwrap();
+        let hash = store.put_blob("image/png", b"png bytes").unwrap();
+        store
+            .add_image(&ImageRecord { id: "i".into(), user_id: None, session_id: None, prompt: "p".into(), model: "m".into(), path: "/gone.png".into(), width: 1, height: 1, created_at: 0, blob: Some(hash.clone()) })
+            .unwrap();
+        assert_eq!(store.gc_blobs().unwrap(), 0);
+        // Moved with the file manager: the entry follows (file or folder, not look-alikes).
+        assert_eq!(store.move_image_paths("/gone.png", "/art/new.png").unwrap(), 1);
+        assert_eq!(store.move_image_paths("/art", "/bilder/").unwrap(), 1);
+        assert_eq!(store.move_image_paths("/bild", "/x").unwrap(), 0);
+        assert_eq!(store.image("i").unwrap().unwrap().path, "/bilder/new.png");
+        assert_eq!(store.blob(&hash).unwrap().unwrap().1, b"png bytes");
+        std::fs::remove_dir_all(&dir).unwrap();
+    }
+
     fn m(id: &str) -> ImageModel {
         with_defaults(ImageModel { id: id.into(), ..Default::default() })
     }