fix(calibre-web): keep /usr/bin resolving for the manual workaround

CodeRabbit spotted that an install already storing "/usr/bin" stays broken:
that value is not empty, so the cont-init statement leaves it alone, and with
the symlink only in /opt/kepubify it no longer resolves under 0.6.27.

The case is real and narrow. A failed save never persists the value --
_configuration_result() calls config.load() on the error path, discarding it --
so the only way to hold "/usr/bin" is a save that succeeded, which requires
having first applied the workaround published in the issue thread:

    ln -sf /usr/bin/kepubify /usr/bin/kepubify-linux-64bit

Anyone who did that, and anyone copying that comment, would have been broken
again by this PR.

Fixed with one more symlink rather than CodeRabbit's suggested migration of
"/usr/bin" back to NULL, because that would overwrite a path the user set by
hand. Making their setting keep working is better than resetting it. Verified
against the 0.6.27 resolution logic:

    symlink in /opt only   stored '/usr/bin' -> ''
    plus /usr/bin symlink  stored '/usr/bin' -> '/usr/bin/kepubify-linux-64bit'
                           autodetect        -> '/opt/kepubify'

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

calibre_web/CHANGELOG.md

@@ -1,4 +1,9 @@
  
+## 0.6.27.4 (2026-09-04)
+- Fix: Kobo sync could not be enabled, failing with "Kepubify binary not found" even when the path was set by hand. The LinuxServer base image installs the converter as `/usr/bin/kepubify` with `curl -o`, which leaves it mode 0644 and gives it a name calibre-web does not accept : `binary_helper.py` only takes `kepubify-linux-64bit` or `kepubify-linux-32bit`, and only when `os.access(X_OK)` passes. The addon now makes the binary executable and publishes it as `/opt/kepubify/kepubify-linux-64bit`, the directory calibre-web's own autodetection already probes, so the path is filled in without any manual step (https://github.com/alexbelgium/hassio-addons/issues/3040)
+- Fix: on installs created before that change, calibre-web had already run its autodetection once, found nothing usable and stored an empty path, and it never retries. An empty path is now reset so calibre-web detects the converter itself at the next start. A path set by hand is left alone
+- Fix: `/usr/bin` also keeps working as a converter path, so the setting stored by anyone who applied the manual `ln -sf /usr/bin/kepubify /usr/bin/kepubify-linux-64bit` workaround keeps resolving after the update instead of silently breaking again
+
 ## 0.6.27.3 (2026-08-30)
 - Doc: explain in the README that Calibre-Web's optional extras (metadata, kobo, gdrive, gmail, goodreads, ldap, oauth, comics) are already installed by the LinuxServer base image, that `pip install calibreweb[...]` inside the container is useless and not persistent, and that the cover fields on the Edit Metadata page are gated on `Enable Uploads` plus the user's `Upload` permission (https://github.com/alexbelgium/hassio-addons/issues/1143)
 - Fix: remove the Dockerfile step that claimed to install the Calibre binaries into `/opt/calibre`. There is no `wget` in the image, so the command failed silently and left the layer empty; the binaries are and were provided at start by the default `linuxserver/mods:universal-calibre` docker mod

calibre_web/Dockerfile

@@ -45,8 +45,23 @@ ARG CONFIGLOCATION="/config"
 RUN chmod 744 /ha_lsio.sh && if grep -qr "lsio" /etc; then /ha_lsio.sh "$CONFIGLOCATION"; fi && rm /ha_lsio.sh
 
 # Specific images modifications
+# The base image installs kepubify with "curl -o /usr/bin/kepubify", which both leaves it mode
+# 0644 and gives it a name calibre-web does not accept : binary_helper.py only takes
+# "kepubify-linux-64bit" or "kepubify-linux-32bit", and only when os.access(X_OK) passes. Both
+# defects have to be fixed, which is why enabling Kobo sync failed with "Kepubify binary not
+# found" even when the path was set by hand. Publish it under an accepted name in /opt/kepubify,
+# the directory calibre-web's own autodetect_kepubify_binary() already probes, so calibre-web
+# fills the setting in itself. The second link keeps /usr/bin working as well : that is the value
+# already stored by anyone who applied the "ln -sf /usr/bin/kepubify /usr/bin/kepubify-linux-64bit"
+# workaround, and their setting is not empty, so it is left alone below and has to keep resolving.
+# Unguarded on purpose: if a future base image stops shipping the binary, the build must fail here
+# rather than ship a silently broken add-on.
 RUN \
-    usermod --home /config abc
+    usermod --home /config abc \
+    && chmod 0755 /usr/bin/kepubify \
+    && mkdir -p /opt/kepubify \
+    && ln -s /usr/bin/kepubify /opt/kepubify/kepubify-linux-64bit \
+    && ln -s /usr/bin/kepubify /usr/bin/kepubify-linux-64bit
 
 ##################
 # 3 Install apps #

calibre_web/config.yaml

@@ -116,5 +116,5 @@ schema:
 slug: calibre-web
 udev: true
 url: https://github.com/alexbelgium/hassio-addons/tree/master/calibre_web
-version: "0.6.27.3"
+version: "0.6.27.4"
 video: true

calibre_web/rootfs/etc/cont-init.d/80-configuration.sh

@@ -32,6 +32,14 @@ else
     # before calibre-web, so a failure here is not fatal : the next start applies it.
     trusted_ips_error=$(sqlite3 /config/app.db "update settings set config_reverse_proxy_trusted_ips='127.0.0.1,::1,::ffff:127.0.0.1,172.30.32.0/23,::ffff:172.30.32.0/119,'||coalesce(config_reverse_proxy_trusted_ips,'') where coalesce(config_reverse_proxy_trusted_ips,'') not like '%::ffff:172.30.32.0/119%'" 2>&1) ||
         bashio::log.warning "Could not set the ingress trusted ip list, it will be applied at next start (${trusted_ips_error})"
+
+    # Calibre-web autodetects kepubify only while this setting is still NULL. On every install
+    # that predates the Dockerfile fix above, that detection already ran, found nothing usable and
+    # stored an empty string, so it is never retried. Put an empty value back to NULL and
+    # calibre-web detects /opt/kepubify itself when it starts, a few seconds after this runs.
+    # A path the user set by hand is not empty and is left alone.
+    kepubify_error=$(sqlite3 /config/app.db "update settings set config_kepubifypath = NULL where config_kepubifypath = ''" 2>&1) ||
+        bashio::log.warning "Could not reset the kepubify path, it will be applied at next start (${kepubify_error})"
 fi
 
 bashio::log.info "Default username:password is admin:admin123"