[Conversion Plugin] KFX Input

[pharaoh]

I cannot download kfx from the device (kindle scribe colorsoft) anymore, calibre crashes if i connect the device. KFX Input is latest 2.31.0

$ calibre
Device 0 (VID=1949 and PID=9981) is a Amazon Kindle Scribe 32GB.
KFX metadata reader (from KFX Input) activated for Scribe dc4b2264-e786-6550-845b-1764e93bf00c Notebook.kfx
Removed 18 KDF SQLite file fingerprint(s)
Found local_action_fragments table with 0 entries
Found local_delta_fragments table with 0 entries
KFX metadata reader (from KFX Input) activated for Scribe AC429BCF52D4420F9A7CA5E1E38F74F3 PDOC Notebook.kfx
Removed 1 KDF SQLite file fingerprint(s)
Found local_action_fragments table with 0 entries
Found local_delta_fragments table with 1 entries
Traceback (most recent call last):
File "/usr/lib64/calibre/calibre/customize/ui.py", line 530, in get_file_type_metadata
mi = plugin.get_metadata(stream, ftype.lower().strip())
File "calibre_plugins.kfx_input.metadata_reader", line 28, in get_metadata
md = YJ_Book(stream).get_metadata()
File "calibre_plugins.kfx_input.kfxlib.yj_book", line 152, in get_metadata
raise Exception("Failed to locate a KFX container with metadata")
Exception: Failed to locate a KFX container with metadata

Here's what I did: epub converted with "sent to kindle", downloaded the converted ebook onto kindle, connect with calibre, crash
If I remove the converted epub fro kindle, calibre does not crash.
i retested it with an epub I converted some time ago using the same method, same exception.
It seems, Amazon changed something in the KFX format.

[pharaoh]

if someone else has the issue:

the format did not change. If i download the kfx-file using mtp directly from the device, remove the download from the device and import the file into calibre, everything is fine: no crash, cover is ok. calibre crashes because libmtp (Linux) crashes if the ebook is downloaded on the device and calibre reads the contents of the device.

[pharaoh]

if someone else has the issue: the issue has been fixed in calibre 0.9.7 "MTP driver: Linux: Fix a rare crash when connecting devices with large collections "

[jhowell]

Originally Posted by pharaoh

if someone else has the issue: the issue has been fixed in calibre 0.9.7 "MTP driver: Linux: Fix a rare crash when connecting devices with large collections "

I'm glad you were able to solve it on your own. I would have been no help with that issue.

[ALZ]

Hi jhowell,
I encountered a new KFX feature that the current KFX Input plugin (v2.31.0) does not support yet.
Error message:
Unknown com.amazon.yjconversion feature: jpvertical-reflow-language-8
Book details:
ASIN: B0GNSJC86C
Issue date: 2026-02-17
Environment:
Calibre 9.8
KFX Input 2.31.0 + KFX Output (latest from this thread)
Windows 11
The book was exported via KFXArchiver 283 + Kindle for PC 2.8.3, imported as KFX-ZIP
Other newer Japanese books I purchased also use vertical reflow, but this is the first one hitting -8. Previous books with -7 worked fine.
Is it possible to add support for jpvertical-reflow-language-8 in the next update? Thank you very much for maintaining this essential plugin!

[jhowell]

Originally Posted by ALZ

Hi jhowell,
I encountered a new KFX feature that the current KFX Input plugin (v2.31.0) does not support yet.
Error message:
Unknown com.amazon.yjconversion feature: jpvertical-reflow-language-8
Book details:
ASIN: B0GNSJC86C
…
Is it possible to add support for jpvertical-reflow-language-8 in the next update? Thank you very much for maintaining this essential plugin!

Thanks for bringing this to my attention and providing an example. I need to do further research but at a first look the new feature appears to involve text rotation. Once I figure it out I will add support for it in the next release of this plugin.

[ALZ]

Originally Posted by jhowell

Thanks for bringing this to my attention and providing an example. I need to do further research but at a first look the new feature appears to involve text rotation. Once I figure it out I will add support for it in the next release of this plugin.

Thank you for investigating the jpvertical-reflow-language-8 issue.
I have encountered another different error with a new series. This series seems to consistently fail with the same SVG wrapper error.
Error:
Unexpected image style for SVG wrapper (img h=1920, w=1344)
It occurs on multiple full-page images with this style:
<div id="page_xx" style="-kfx-style-name: sFN; text-align: center"><img src="..." style="-kfx-style-name: sFN; height: 100%"/></div>
Affected books (all in the same series):
金獅子の王と漆黒の騎士 ～双翼の絆～【イラスト入り】 (ガッシュ文庫)
金獅子の王と漆黒の騎士 ～蜜月夜～【イラスト入り】 (ガッシュ文庫)
金獅子の王と漆黒の騎士 ～婚礼の儀～【イラスト入り】 (ガッシュ文庫)
All were imported as KFX-ZIP using the latest KFXArchiver + Kindle for PC 2.8.3, with KFX Input 2.31.0 + Calibre 9.8.
These appear to be fixed-layout heavy illustration books. Let me know if you need more details or sample files.
Thanks again for your great work!

[jhowell]

Originally Posted by ALZ

I have encountered another different error with a new series. This series seems to consistently fail with the same SVG wrapper error.

That error will also be fixed in the next plugin update.

[topher18]

I’m trying to understand whether I’m seeing a known KFX/DeDRM limitation, a newer unsupported KFX DRM voucher format, or something still wrong with my import process.

I tried to Add Book to the library from the device window in Calibre.

The book is: Living Off Your Acorns: Your Guide To The Four Phases of Retirement

Environment:

* macOS 26.4.1
* Calibre 9.8.0
* KFX Input 2.31.0
* DeDRM 10.0.9
* Source device: e-ink Kindle over USB
* The Kindle serial number configured in DeDRM matches the physical Kindle used for the import

Background:

On my first attempt, Calibre/KFX Input failed with this error:

```text
KeyError('YJFragmentList item is missing: c0:: $260::')
```

That made me think Calibre might not have copied or seen the full KFX package.

I then retried using **Add Books from Device** with Mac Finder set to show hidden files. After that, the missing `YJFragmentList` error disappeared. KFX Input now appears to find and process multiple KFX containers:

```text
Processing container: CR!BFNNP2AQAD4Z92XNKQJ8W6EMW8CF.kfx
Processing container: CR!PSE90HPHNN6VBD7Q47XBXNHNPJPC.kfx
Processing container: Living Off Your Acorns_ Your Guide To The Four Phases of Retirement_B0GYRGVXYL.kfx
```

However, DeDRM still fails before conversion completes:

```text
DeDRM v10.0.9: Trying to decrypt vq72ly8z.kfx-zip
Decrypting KFX-ZIP ebook: vq72ly8z
Found 1 keys to try after 0.8 seconds
Decrypting KFX DRM voucher: voucher
Exception: Unknown type encountered in envelope, expected VoucherEnvelope
DeDRM v10.0.9: Failed to decrypt with error: Failed to decrypt KFX DRM voucher with any key
DeDRM v10.0.9: Looking for new default Kindle Key after 0.8 seconds
No k4Mac kindle-info/rainier/kinf2011 files have been found.
DeDRM v10.0.9: Ultimately failed to decrypt after 0.8 seconds.
```

Then KFX Input fails because the book still has DRM:

```text
KFXDRMError: Book container Living Off Your Acorns_ Your Guide To The Four Phases of Retirement_B0GYRGVXYL.kfx has DRM and cannot be converted
calibre.ebooks.DRMError: This book has DRM!
```

My current interpretation is:

1. The original missing-fragment problem may have been caused by an incomplete import or hidden/supporting files not being included.
2. After re-importing, the KFX package appears complete enough for KFX Input to process the containers.
3. The remaining problem appears to be DeDRM failing to parse/decrypt the KFX DRM voucher.
4. Since DeDRM reports “Found 1 keys to try,” it seems to be finding a candidate key from my configured e-ink Kindle serial number.
5. The later `k4Mac kindle-info/rainier/kinf2011` message looks like fallback behavior after the first key failed, not necessarily evidence that my e-ink Kindle serial number was ignored.

Does this error:

```text
Unknown type encountered in envelope, expected VoucherEnvelope
```

indicate a newer or unsupported KFX DRM voucher/container format?

Or is there still something else I should check about the KFX import from the e-ink Kindle?

I’m not looking for general DRM-circumvention advice. I’m trying to determine whether this is a known limitation/compatibility issue with this KFX book, this Kindle download path, or the current KFX Input / DeDRM toolchain.

[jhowell]

Version 2.32.0 - 14 May 2026

Prevent error when converting books with the jpvertical-reflow-language-8 feature.

Handle full page images in vertical layout Japanese books. Fixes "Unexpected image style for SVG wrapper".

[jhowell]

Originally Posted by topher18

I’m trying to understand whether I’m seeing a known KFX/DeDRM limitation, a newer unsupported KFX DRM voucher format, or something still wrong with my import process.
...
My current interpretation is:

1. The original missing-fragment problem may have been caused by an incomplete import or hidden/supporting files not being included.

Most likely the download of the book from Amazon to the Kindle was not yet complete when you started the import.

Originally Posted by topher18

2. After re-importing, the KFX package appears complete enough for KFX Input to process the containers.

Yes.

Originally Posted by topher18

3. The remaining problem appears to be DeDRM failing to parse/decrypt the KFX DRM voucher.

Amazon has recently updated the DRM in use on almost all Kindle devices, even older ones that have not received a full firmware update in years. The error "Unknown type encountered in envelope, expected VoucherEnvelope" is an indication of newer DRM that the version of DeDRM you used does not support.

The first post in the thread Dealing with Kindle ebooks in calibre generally has the latest information on the status of Kindle DRM. The section "Method 3: eink Kindle" is relevant to you.

Originally Posted by topher18

4. Since DeDRM reports “Found 1 keys to try,” it seems to be finding a candidate key from my configured e-ink Kindle serial number.

Yes.

Originally Posted by topher18

5. The later `k4Mac kindle-info/rainier/kinf2011` message looks like fallback behavior after the first key failed, not necessarily evidence that my e-ink Kindle serial number was ignored.

That is an attempt by DeDRM to obtain a key from the old Kindle for Mac app, just in case your book was imported from that app. It does nothing useful at this point since that app has been retired.

[sosuke]

Hi, I'm getting conversion errors saying Bookpart filename is not unique. Please let me know if any other information is required.

Convert from KFX
Software versions: From KFX 2.32.0, calibre 9.8, Linux-5.15.0-161-generic-x86_64-with-glibc2.43
KFX Input plugin help is available at https://www.mobileread.com/forums/sh...d.php?t=291290

Processing The New Girl: First Crush: A Graphic Novel (The New Girl #2)
Processing container: /tmp/calibre-2_bojvdz/ahm7wupt.kfx
Features: CanonicalFormat-2, kfxgen.positionMaps-2, kfxgen.textBlock-1, yj_double_page_spread-1, yj_non_pdf_fixed_layout-2, yj_thumbnails_present-1
Metadata: ASIN=B0FK1NHFKB, asset_id=CR!K5NP78T16X1P37NZASZZXSE3TQW2, author="Calin, Cassandra", book_id=Zh7QTsT4RY6GdN3-QqM9kw0, cde_content_type=EBOK, content_id=B0FK1NHFKB, continuous_popup_progression=0, creator_version=2.15.0, file_creator=YJConversionTools, is_sample=False, issue_date=2026-05-05, kfxgen=20.12.238.0, language=en, max_id=851, min_kindle_version=5.8.5, publisher="Scholastic Inc.", reading_orders=1, title="The New Girl: First Crush: A Graphic Novel (The New Girl #2)", yj_double_page_spread=1, yj_fixed_layout=1
Converting book to EPUB 2
Traceback (most recent call last):
  File "calibre_plugins.kfx_input.jobs", line 56, in convert_process
    epub_data = book.convert_to_epub(
        epub2_desired=epub2_desired,
        desaturate_notebooks=config_desaturate_notebooks(),
        progress_fn=update_progress)
  File "calibre_plugins.kfx_input.kfxlib.yj_book", line 105, in convert_to_epub
    result = KFX_EPUB(self, epub2_desired=epub2_desired, force_cover=force_cover,
             ~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                      desaturate_notebooks=desaturate_notebooks,
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                      progress=make_progress(progress_fn)).decompile_to_epub()
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "calibre_plugins.kfx_input.kfxlib.yj_to_epub", line 95, in __init__
    self.process_reading_order()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "calibre_plugins.kfx_input.kfxlib.yj_to_epub_content", line 110, in process_reading_order
    self.process_section(self.get_fragment(ftype="$260", fid=section_name), seq)
    ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "calibre_plugins.kfx_input.kfxlib.yj_to_epub_content", line 154, in process_section
    self.process_page_spread_page_template(self.get_fragment(ftype="$608", fid=page_templates[0]), section_name)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "calibre_plugins.kfx_input.kfxlib.yj_to_epub_content", line 253, in process_page_spread_page_template
    self.process_page_spread_page_template(page_template_, section_name, page_property, parent_template_id, is_section=False)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "calibre_plugins.kfx_input.kfxlib.yj_to_epub_content", line 335, in process_page_spread_page_template
    book_part = self.new_book_part(
        filename=self.SECTION_TEXT_FILEPATH % unique_section_name if RETAIN_SECTION_FILENAMES else None,
        opf_properties=set(page_spread.split()))
  File "calibre_plugins.kfx_input.kfxlib.epub_output", line 509, in new_book_part
    raise Exception("BookPart filename %s is not unique" % filename)
Exception: BookPart filename /cR-left.xhtml is not unique
ERROR: Unhandled exception: Exception('BookPart filename /cR-left.xhtml is not unique')

Thanks

[jhowell]

Originally Posted by sosuke

Hi, I'm getting conversion errors saying Bookpart filename is not unique. Please let me know if any other information is required.

Thank you for the report. I will look into it and let you know if I need any additional information.

[jhowell]

Originally Posted by sosuke

Hi, I'm getting conversion errors saying Bookpart filename is not unique. Please let me know if any other information is required.

An update on this:

I have been able to duplicate the problem and I found that it is caused by different KFX formatting that Amazon has begun using on comics delivered to Kindles running older firmware prior to version 5.18.

It appears that they are replacing existing comics with panel view (that were previously delivered to those Kindles in KF8/AZW3 format) with a KFX variant that does not contain panels in order for them to work on older Kindle firmware. This is likely part of an upcoming retiring of the older Kindle formats by Amazon.

This new KFX variant will be handled in the next plugin release but it will take several days to develop and test.

[topher18]

Thank you, jhowell.

<< The first post in the thread Dealing with Kindle ebooks in calibre generally has the latest information on the status of Kindle DRM. The section "Method 3: eink Kindle" is relevant to you. >>