[JimmXinu]

Originally Posted by tatteredscroll

Does the CLI expect simple filenames for merge? In other words, for multiple files, is it expecting something like--

$ calibre-debug --run-plugin EpubMerge file1.epub file2.epub book9.epub

EpubMerge itself doesn't have any particular expectations about file names.

Unless it's just an oversight that you forgot to include in your post, I suspect you need the '--' after '--run-plugin EpubMerge' that tells calibre-debug's option parser to stop and pass everything after that to EpubMerge.

From first post:

Originally Posted by JimmXinu

Usage: calibre-debug.exe --run-plugin EpubMerge -- [options] <input epub> [<input epub>...]

Given list of epubs will be merged together into one new epub.

Options:
  -h, --help            show this help message and exit
  -o OUTPUT, --output=OUTPUT
                        Set OUTPUT file, Default: merge.epub
  -t TITLE, --title=TITLE
                        Use TITLE as the metadata title.  Default: '<first
                        epub title> Anthology'
  -d DESC, --description=DESC
                        Use DESC as the metadata description.  Default: '<epub
                        title> by <author>' for each epub.
  -a AUTHOR, --author=AUTHOR
                        Use AUTHOR as a metadata author, multiple authors may
                        be given, Default: <All authors from epubs>
  -g TAG, --tag=TAG     Include TAG as dc:subject tag, multiple tags may be
                        given, Default: None
  -l LANG, --language=LANG
                        Include LANG as dc:language tag, multiple languages
                        may be given, Default: en
  -n, --no-titles-in-toc
                        Default is to put an entry in the TOC for each epub,
                        nesting each epub's chapters under it.
  -N, --no-original-toc
                        Default is to include the TOC from each original epub.
  -f, --flatten-toc     Flatten TOC down to one level only.
  -c COVER, --cover=COVER
                        Path to a jpg to use as cover image.
  -k, --keep-meta       Keep original metadata files in merged epub.  Use for
                        UnMerging.
  -s URL, --source=URL  Include URL as dc:source and
                        dc:identifier(opf:scheme=URL).
  -u, --unmerge         UnMerge an existing epub that was created by merging
                        with --keep-meta.
  -D OUTPUTDIR, --outputdir=OUTPUTDIR
                        Set output directory for unmerge, Default: (current
                        dir)