fix(images): percent-encode original-image URLs ('#' in paths 404'd)

An image whose on-disk path contains '#' (post folders like 'BLUE#59')
served its hash-named thumbnail fine but 404'd the original: the unencoded
'#' in image_url was parsed by the browser as a URL fragment, so
'#59/01_timelapse.jpg' never reached the /images route. Add a shared
image_url(path) helper that percent-encodes the path (safe='/') and route
the 3 raw builders (gallery detail + 2 in series) through it. Not a
cleanup-tool deletion — the file is on disk; only the URL was wrong.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/app/services/gallery_service.py

@@ -16,6 +16,7 @@ translates that to HTTP 400.
 
 from dataclasses import dataclass
 from datetime import datetime
+from urllib.parse import quote
 
 from sqlalchemy import Select, and_, distinct, exists, func, or_, select
 from sqlalchemy.ext.asyncio import AsyncSession
@@ -120,6 +121,21 @@ def thumbnail_url(thumbnail_path: str | None, sha256_hex: str, mime: str) -> str
     return f"/images/thumbs/{bucket}/{sha256_hex}{ext}"
 
 
+def image_url(path: str) -> str:
+    """Return the URL to fetch the full-size original from /images.
+
+    The on-disk `path` mirrors the source tree (artist/post folders), so it can
+    contain characters that are special in a URL — most importantly '#' (post
+    titles like 'BLUE#59'), but also spaces, '?', '%'. The serve_image route
+    URL-decodes its <path:subpath> fine, but only if the browser sends the whole
+    path; an unencoded '#' is parsed as a fragment, so '#59/01_timelapse.jpg'
+    never reaches the server and the original 404s while the (hash-named)
+    thumbnail still loads. Percent-encode the path, keeping '/' as the segment
+    separator. Operator-flagged 2026-06-12."""
+    rel = path.split("/images/", 1)[-1]
+    return f"/images/{quote(rel, safe='/')}"
+
+
 def _require_single_filter(tag_ids, post_id, artist_id) -> None:
     """post_id is the post-detail view — it can't combine with the
     composable filters. tag_ids + artist_id (+ media_type) compose freely
@@ -589,7 +605,7 @@ class GalleryService:
             "created_at": record.created_at.isoformat(),
             "posted_at": posted_at.isoformat() if posted_at else None,
             "thumbnail_url": thumbnail_url(record.thumbnail_path, record.sha256, record.mime),
-            "image_url": f"/images/{record.path.split('/images/', 1)[-1]}",
+            "image_url": image_url(record.path),
             "artist": (
                 {"id": artist.id, "name": artist.name, "slug": artist.slug}
                 if artist is not None else None

backend/app/services/series_service.py

@@ -19,7 +19,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from ..models import Artist, ImageRecord, Post, Tag, TagKind
 from ..models.series_chapter import SeriesChapter
 from ..models.series_page import SeriesPage
-from .gallery_service import thumbnail_url
+from .gallery_service import image_url, thumbnail_url
 from .page_number_parser import parse_page_range
 
 
@@ -194,7 +194,7 @@ class SeriesService:
                 "thumbnail_url": thumbnail_url(
                     r.thumbnail_path, r.sha256, r.mime
                 ),
-                "image_url": f"/images/{r.path.split('/images/', 1)[-1]}",
+                "image_url": image_url(r.path),
                 "source_post": (
                     {"id": r.primary_post_id, "title": r.post_title}
                     if r.primary_post_id is not None
@@ -282,7 +282,7 @@ class SeriesService:
                     "thumbnail_url": thumbnail_url(
                         r.thumbnail_path, r.sha256, r.mime
                     ),
-                    "image_url": f"/images/{r.path.split('/images/', 1)[-1]}",
+                    "image_url": image_url(r.path),
                 }
             )
             # Group start page = the post's parsed starting page (stored on the

tests/test_gallery_service.py

@@ -8,11 +8,22 @@ from backend.app.services.gallery_service import (
     GalleryService,
     decode_cursor,
     encode_cursor,
+    image_url,
 )
 
 pytestmark = pytest.mark.integration
 
 
+def test_image_url_percent_encodes_special_chars():
+    # A '#' in a post folder ('BLUE#59') would otherwise be parsed as a URL
+    # fragment, dropping the rest of the path and 404'ing the original while the
+    # hash-named thumbnail still loads. Operator-flagged 2026-06-12.
+    url = image_url("/images/dismassd/patreon/2024-04-28_BLUE#59/01 a.jpg")
+    assert url == "/images/dismassd/patreon/2024-04-28_BLUE%2359/01%20a.jpg"
+    # '/' stays a separator; a plain path is unchanged.
+    assert image_url("/images/a/b/c.jpg") == "/images/a/b/c.jpg"
+
+
 def _now():
     return datetime.now(UTC)