[GUI Plugin] Check Books

[mallomar]

Thiago meu –

I'm having a couple issues. for some reason clicking on ACE or EPUB Check or customize from the context menu does nothing. I thought the plugin wasn't working but it runs from the menu bar.

However, running ACE Check produces "Invalid EPUB or DRMed" for every book if I run Calibre from Terminal and "ERROR: No report found: Something went wrong. ACE did not produce a report. NoneType: None," if I run do not run Calibre from Terminal. I'm not sure why running Calibre from Terminal or not would produce different results and why neither would work. Terminal shows ACE is installed. Testing with standard EPUB files that I've converted in Calibre (definitely not DRM-protected). Running macOS 15.7, Calibre 8.9, Ace 1.3.7. Usually launch Calibre via Applications folder/Dock.

Thanks!

[thiago.eec]

Originally Posted by mallomar

Thiago meu –

I'm having a couple issues. for some reason clicking on ACE or EPUB Check or customize from the context menu does nothing. I thought the plugin wasn't working but it runs from the menu bar.

I don't have access to MacOS, but it it works just fine on Windows / Linux via context menu.

Originally Posted by mallomar

However, running ACE Check produces "Invalid EPUB or DRMed" for every book if I run Calibre from Terminal and "ERROR: No report found: Something went wrong. ACE did not produce a report. NoneType: None," if I run do not run Calibre from Terminal. I'm not sure why running Calibre from Terminal or not would produce different results and why neither would work. Terminal shows ACE is installed. Testing with standard EPUB files that I've converted in Calibre (definitely not DRM-protected). Running macOS 15.7, Calibre 8.9, Ace 1.3.7. Usually launch Calibre via Applications folder/Dock.

Thanks!

When you say run from terminal, do you mean using 'calibre-debug -g'?
It works fine here using calibre-debug.

P.S.: I just noticed that, for some reason, I forgot to publish the last release (version 0.2.0). Please remove Check Books complely and install the new version from the first post (or via calibre, in an hour or so).

[thiago.eec]

Version 0.2.0 - 22 Aug 2025

- Bug fixes
- Improvements for saving the reports to calibre data folders

[mallomar]

Originally Posted by thiago.eec

I don't have access to MacOS, but it it works just fine on Windows / Linux via context menu.

Yeah, it's bizarre. Nothing happens when I click via the context menu.

Originally Posted by thiago.eec

When you say run from terminal, do you mean using 'calibre-debug -g'?
It works fine here using calibre-debug.

I mean running it like in the first attached image.

Originally Posted by thiago.eec

P.S.: I just noticed that, for some reason, I forgot to publish the last release (version 0.2.0). Please remove Check Books complely and install the new version from the first post (or via calibre, in an hour or so).

Thanks, but I'm still having the same issues. See attached images, one from running from Terminal, one without. Note that the issues are the same for all EPUBs.

[thiago.eec]

I remembered another Mac user having a similar problem. Maybe his solution works for you: https://www.mobileread.com/forums/sh...9&postcount=31

Originally Posted by uhh.andy

I figured out what the problem was.
I had installed node with homebrew, and for apple silicon Macs the executables are put in '/opt/homebrew/bin' which was not in the PATH when subprocess.Popen ran ace.
Adding it to the path fixed the issue.

[mallomar]

Hi thiago.eec,

Following up on my issue. I've managed to clean up my Calibre installation and capture a clean debug log of the "Check Books" plugin failing.

The Key Finding: The plugin seems to fail silently. When I run the check, the external ACE tool appears to crash without returning any error message to the Calibre debug log.

My System:

macOS 15.7 on Apple Silicon

Calibre 8.9 (running on Python 3.11.12)

Node.js is installed at /usr/local/bin/node

What I've Confirmed:

The problem occurs on all EPUBs, including the DRM-free Calibre "Quick Start Guide."

Calibre has Full Disk Access.

I have a clean plugin environment after removing several old, incompatible Python 2 plugins.

I am launching Calibre from the terminal (calibre-debug -g) to ensure the correct PATH is used.

Please see the complete, clean debug log below. It captures Calibre starting up, me running the check (which produces the "Invalid EPUB" error in the GUI), and then me shutting Calibre down. As you can see, after the startup sequence, no specific error from your plugin is logged to the console.

--- CALIBRE DEBUG LOG (from startup through the error) ---

Spoiler:

Last login: Wed Aug 27 16:30:19 on ttys000
rapaz@Mac ~ % /Applications/calibre.app/Contents/MacOS/calibre-debug -g


calibre 8.9 embedded-python: True
macOS-15.7-arm64-arm-64bit Darwin ('64bit', '')
('Darwin', '24.6.0', 'Darwin Kernel Version 24.6.0: Mon Aug 11 21:11:04 PDT 2025; root:xnu-11417.140.69.701.11~1/RELEASE_ARM64_T6031')
Python 3.11.12
OSX: ('15.7', ('', '', ''), 'arm64')
Interface language: None
EXE path: /Applications/calibre.app/Contents/MacOS/calibre-debug
Integration status: True
----------------------------------- REMARKABLE PLUGIN web interface ------------------------
Successfully initialized third party plugins: Gather KFX-ZIP (from KFX Input) (2, 26, 2) && DeDRM (10, 0, 9) && Package KFX (from KFX Input) (2, 26, 2) && Apple Books covers (1, 1, 0) && Barnes & Noble (1, 5, 7) && BookFusion Plugin (0, 8, 1) && Check Books (0, 2, 0) && Count Pages (1, 13, 7) && Extract ISBN (1, 6, 5) && Fantastic Fiction (1, 7, 2) && Find Duplicates (1, 10, 9) && Goodreads (1, 8, 3) && Goodreads More Tags (1, 2, 1, 2) && Goodreads Sync (1, 16, 11) && Hardcover (0, 2, 3) && ISFDB3 (1, 4, 2) && KFX metadata reader (from KFX Input) (2, 26, 2) && From KFX (2, 26, 2) && KFX Input (2, 26, 2) && Set KFX metadata (from KFX Output) (2, 17, 1) && KFX Output (2, 17, 1) && KOReader Sync (0, 7, 2) && Kindle hi-res covers (0, 5, 1) && KindleUnpack - The Plugin (0, 83, 8) && Kobo Metadata (1, 12, 0) && Kobo Utilities (2, 24, 2) && Obok DeDRM (10, 0, 9) && OverDrive Libby (0, 2, 3) && Overdrive Link (2, 58, 0) && Quality Check (1, 14, 2) && Resize Cover (1, 2, 1) && ScrambleEbook (0, 6, 0) && SmartEject (2, 6, 0) && WordDumb (3, 33, 3) && remarkable-calibre-usb-device (0, 1, 2)
QPA platform: cocoa
devicePixelRatio: 1.0
logicalDpi: 72.0 x 72.0
physicalDpi: 255.00000382971584 x 255.00000382971578
ApplicationPaletteChange event ignored
Using calibre Qt style: True
[0.00] Starting up...
[0.03] Showing splash screen...
[1.20] splash screen shown
[1.20] Initializing db...
[1.25] db initialized
[1.25] Constructing main UI...
[1.84] [DEBUG] [koboutilities.config:<module>:75] CreateNewCustomColumn is supported
DEBUG: 0.0 obok::utilities.py - loading translations
DEBUG: 0.0 obok::dialogs.py - loading translations
DEBUG: 0.0 obok::config.py - loading translations
DEBUG: 0.0 obok::action_err.py - loading translations
qt.webengine.QWebEngineView OK
qt.gui.imageio: libpng warning: iCCP: known incorrect sRGB profile
DEBUG: 0.0 koreader:action:KoreaderAction:genesis:start
[2.20] [DEBUG] [koboutilities.action:KoboUtilitiesAction.genesis:1 21] Running in optimized mode
Failed to load resource: 'commit.txt' from the plugin zip file: /Users/rapaz/Library/Preferences/calibre/plugins/OverDrive Libby.zip
Traceback (most recent call last):
File "calibre/customize/zipplugin.py", line 46, in get_resources
File "zipfile.py", line 1527, in read
File "zipfile.py", line 1564, in open
File "zipfile.py", line 1493, in getinfo
KeyError: "There is no item named 'commit.txt' in the archive"
[overdrive_libby/0.2.3] Loaded 0 items from file cache /Users/rapaz/Library/Preferences/calibre/plugins/overdrive_libby.libraries.json
DEBUG:calibre_plugins.overdrive_libby:Loaded 0 items from file cache /Users/rapaz/Library/Preferences/calibre/plugins/overdrive_libby.libraries.json
[overdrive_libby/0.2.3] Loaded 0 items from file cache /Users/rapaz/Library/Preferences/calibre/plugins/overdrive_libby.media.json
DEBUG:calibre_plugins.overdrive_libby:Loaded 0 items from file cache /Users/rapaz/Library/Preferences/calibre/plugins/overdrive_libby.media.json
qt.gui.imageio: libpng warning: iCCP: known incorrect sRGB profile
qt.svg: Cannot open file '/Users/rapaz/Library/Preferences/calibre/resources/images/WordDumb/starfish.svg', because: No such file or directory
qt.svg: Cannot open file '/Users/rapaz/Library/Preferences/calibre/resources/images/WordDumb/starfish.svg', because: No such file or directory
[2.49] GUI main window shown
[2.55] [DEBUG] [koboutilities.config:get_library_config:641] library_config: {'SchemaVersion': 1,
'profiles': {},
'readingPositionChangesStore': {'selectBooksInLibrary': False,
'updeateGoodreadsProgress': False},
'shelvesColumn': None}
[2.55] [DEBUG] [koboutilities.action:KoboUtilitiesAction.device_dr iver_name:759] could not load extended driver. Exception= No module named 'calibre_plugins.kobotouch_extended'
[2.55] [DEBUG] [koboutilities.action:KoboUtilitiesAction.set_toolb ar_button_tooltip:181] setting to text='Utilities to use with Kobo ereaders

Driver: KoboTouch'
[2.60] main UI initialized...
[2.60] Hiding splash screen
[2.65] splash screen hidden
[2.65] Started up in 2.65 seconds with 1315 books
2025-08-27 16:33:57.756 calibre-debug[30679:720574] TSMSendMessageToUIServer: CFMessagePortSendRequest FAILED(-1) to send to port com.apple.tsm.uiserver
2025-08-27 16:33:57.757 calibre-debug[30679:720574] TSMSendMessageToUIServer: CFMessagePortSendRequest FAILED(-1) to send to port com.apple.tsm.uiserver
0:00:02.092398
2025-08-27 16:33:59.865 calibre-debug[30679:720574] TSMSendMessageToUIServer: CFMessagePortSendRequest FAILED(-1) to send to port com.apple.tsm.uiserver
2025-08-27 16:33:59.865 calibre-debug[30679:720574] TSMSendMessageToUIServer: CFMessagePortSendRequest FAILED(-1) to send to port com.apple.tsm.uiserver
2025-08-27 16:33:59.865 calibre-debug[30679:720574] TSMSendMessageToUIServer: CFMessagePortSendRequest FAILED(-1) to send to port com.apple.tsm.uiserver
[51.58] Shutdown starting...
[53.83] Shutdown complete, quitting...
rapaz@Mac ~ %

This seems to point to an incompatibility between the ACE tool and the macOS/Apple Silicon environment. Any help you can provide would be greatly appreciated. Thanks!

[thiago.eec]

Can you run the ACE editor plugin?

[slimcat]

I have a question about the EPUBCheck result pass/fail column. If a book has already passed EPUBCheck and has the green checkmark, that checkmark remains for me, even if a subsequent EPUBCheck (after book updates) fails. A red pin does appear on the far left, but the actual EPUBCheck result column still shows it passed (see screenshot).

Is this expected behavior? Just wondering if I'm doing something wrong or need to tweak settings in some way.

[thiago.eec]

Originally Posted by slimcat

I have a question about the EPUBCheck result pass/fail column. If a book has already passed EPUBCheck and has the green checkmark, that checkmark remains for me, even if a subsequent EPUBCheck (after book updates) fails. A red pin does appear on the far left, but the actual EPUBCheck result column still shows it passed (see screenshot).

Is this expected behavior? Just wondering if I'm doing something wrong or need to tweak settings in some way.

Just checked here: EPUBCheck treats invalid/DRMed files differently. If the books still has DRM, EPUBCheck can't analize the file, so it will return a FATAL error. If it has parsing errors (like a mismatching tag), it also abort the check and return a FATAL error. When the book is not malformed, then the other errors are marked as ERROR.

A DRMed book can't have its result marked as FALSE (red X), because it was not analyzed. On the other hand, the book with parsing errors restul should be marked as FALSE.

The problem is EPUBCheck treats them equally. If it can't finalize the check, the file is marked with a FATAL flag.

I guess the only pratical option would be to clear the status column, when FATAL errors occurs.

[slimcat]

Originally Posted by thiago.eec

Just checked here: EPUBCheck treats invalid/DRMed files differently. If the books still has DRM, EPUBCheck can't analize the file, so it will return a FATAL error. If it has parsing errors (like a mismatching tag), it also abort the check and return a FATAL error. When the book is not malformed, then the other errors are marked as ERROR.

A DRMed book can't have its result marked as FALSE (red X), because it was not analyzed. On the other hand, the book with parsing errors restul should be marked as FALSE.

The problem is EPUBCheck treats them equally. If it can't finalize the check, the file is marked with a FATAL flag.

I guess the only pratical option would be to clear the status column, when FATAL errors occurs.

Thanks so much for the explanation. I completely missed the difference between the handling of fatal and non-fatal errors.

I did figure out a way to mark invalid epubs as FALSE using an Action Chains script that reads the JSON reports and sets results to No if there are fatal errors (it also clears/replaces previous Yes results). It doesn't touch the result column for anything else (e.g. files with no report or with a pre-existing pass or fail because of non-fatal errors). If a report is gone or can't be read, it just skips that epub.

You can run it on your entire library and it will flag all the FATAL aborts. It's been really fast for me. Almost instantaneous, even on large batches (although I know that will vary by system).

Script is below and Action Chain is attached, in case others find it useful.

Script:

import json
import re
import urllib.parse

def run(gui, settings, chain):
    db = gui.current_db
    newdb = db.new_api
    book_ids = list(gui.library_view.get_selected_ids())

    for book_id in book_ids:
        report_html = newdb.field_for('#epubcheck_report', book_id)

        if not report_html:
            continue

        match = re.search(r'href="file:///(.*?)"', report_html)
        if not match:
            continue

        path = '/' + urllib.parse.unquote(match.group(1))

        try:
            with open(path, 'r', encoding='utf-8') as f:
                data = json.load(f)
        except:
            continue

        nFatal = data.get('checker', {}).get('nFatal', 0)

        if nFatal > 0:
            newdb.set_field('#epubcheck_result', {book_id: False})

fwiw I initially tried setting up a chain that ran EPUBCheck and then the script, but it wasn't reliable. I couldn’t figure out how to make sure the reports were written before the script ran, even with small batches (like 5 books). I tried adding a delay, but it wasn't long enough and I didn't want to keep guessing & slowing things down further. The benefit didn't seem worth it when the script is easy to run separately and super fast on its own.

[thiago.eec]

Originally Posted by slimcat

I did figure out a way to mark invalid epubs as FALSE using an Action Chains script that reads the JSON reports and sets results to No if there are fatal errors (it also clears/replaces previous Yes results).

I will change the plugin to mark invalid/DRMed books as FALSE. I guess it's better then just clearing the column, since most of the time it will be a malformed book, and not a DRMed book.

I'll release a fix soon.

P.S.: For the books already checked in you library, your script be faster, because it just reads the JSON report. Running EPUBCheck again would take a lot longer.

[thiago.eec]

Version 0.2.1 - 20 Mar 2026

- Set the result column as FALSE when the book is DRMed or invalid (malformed)

[slimcat]

Originally Posted by thiago.eec

Version 0.2.1 - 20 Mar 2026

- Set the result column as FALSE when the book is DRMed or invalid (malformed)

This is great. Thank you so much!!