Error in NVDA 2026.1.1 when navigating in fractions

[MartheGjelstad]

I am using NVDA 2026.1.1 with the built in MathCAT. I updated NVDA from version 2025.3.3, where I had MathCAT as an add-on. This add-on is now disabled. I have replaced the libmathcat_py.pyd in the folder C:\Program files\NVDA with your new build @NSoiffer .

Below are some examples of MathML expressions and the error messages I get when I try to navigate in the expressions.

ClearSpeak

Navigation mode: It's not possible to change the navigation mode for the expressions where an error occur.

Summary: I think the navigation is not working for expressions following one of the rules:

• fraction-over-text
• default

Expression 1

Error message:

ERROR - mathPres.MathCAT.MathCAT.MathCATInteraction.reportFocus (13:05:26.066) - MainThread (14828):
Traceback (most recent call last):
  File "mathPres\MathCAT\MathCAT.pyc", line 81, in reportFocus
OSError: Internal error: With en/ClearSpeak in Enhanced mode, can't ZoomIn from expression with id 'M54sz3zn-2' inside:
 <math data-from-mathml='math' id='M54sz3zn-0' data-id-added='true'>
  <fraction data-from-mathml='mfrac' id='M54sz3zn-1' data-id-added='true'>
    <mrow data-from-mathml='mrow' id='M54sz3zn-2' data-id-added='true'>
      <mi data-from-mathml='mi' id='M54sz3zn-3' data-id-added='true'>x</mi>
      <mo data-from-mathml='mo' id='M54sz3zn-4' data-id-added='true'>+</mo>
      <mi data-from-mathml='mi' id='M54sz3zn-5' data-id-added='true'>y</mi>
    </mrow>
    <mrow data-from-mathml='mrow' id='M54sz3zn-6' data-id-added='true'>
      <mi data-from-mathml='mi' id='M54sz3zn-7' data-id-added='true'>x</mi>
      <mo data-from-mathml='mo' id='M54sz3zn-8' data-id-added='true'>-</mo>
      <mi data-from-mathml='mi' id='M54sz3zn-9' data-id-added='true'>y</mi>
    </mrow>
  </fraction>
 </math>

MathML expression:

<p>
    <math>
        <mrow>
        <mfrac>
        <mrow>
        <mi>x</mi><mo>+</mo><mi>y</mi></mrow>
        <mrow>
        <mi>x</mi><mo>-</mo><mi>y</mi></mrow>
        </mfrac>
        </mrow>
    </math>
</p>

Expression 2

I get an error message when I try to navigate in the fraction.

Error message:

ERROR - mathPres.MathCAT.MathCAT.MathCATInteraction._do_navigate (13:07:34.426) - MainThread (14828):
Traceback (most recent call last):
  File "mathPres\MathCAT\MathCAT.pyc", line 159, in _do_navigate
OSError: Internal error: With en/ClearSpeak in Enhanced mode, can't ZoomIn from expression with id 'Mkjjrix2-5' inside:
 <math data-from-mathml='math' id='Mkjjrix2-0' data-id-added='true'>
  <mrow data-from-mathml='mrow' id='Mkjjrix2-1' data-id-added='true'>
    <mn data-from-mathml='mn' id='Mkjjrix2-2' data-id-added='true'>62</mn>
    <mo data-from-mathml='mo' data-changed='added' id='Mkjjrix2-3' data-id-added='true'>&#x2062;</mo>
    <fraction data-from-mathml='mfrac' id='Mkjjrix2-4' data-id-added='true' data-intent-property=':unit:'>
      <unit data-from-mathml='mi' id='Mkjjrix2-5' data-id-added='true' data-intent-property=':unit:'>mi</unit>
      <unit data-from-mathml='mi' id='Mkjjrix2-6' data-id-added='true' data-intent-property=':unit:'>hr</unit>
    </fraction>
  </mrow>
 </math>

MathML expression:

<p>
    <math>
        <mrow>
        <mn>62</mn>
        <mfrac>
        <mi intent=':unit'>mi</mi>
        <mi intent=':unit'>hr</mi>
        </mfrac>
        </mrow>
    </math>
</p>

Expression 3

Error message:

ERROR - mathPres.MathCAT.MathCAT.MathCATInteraction.reportFocus (13:10:13.295) - MainThread (14828):
Traceback (most recent call last):
  File "mathPres\MathCAT\MathCAT.pyc", line 81, in reportFocus
OSError: Internal error: With en/ClearSpeak in Enhanced mode, can't ZoomIn from expression with id 'Mad3q3m6-2' inside:
 <math data-from-mathml='math' id='Mad3q3m6-0' data-id-added='true'>
  <fraction data-from-mathml='mfrac' id='Mad3q3m6-1' data-id-added='true'>
    <mi data-from-mathml='mi' id='Mad3q3m6-2' data-id-added='true'>rise</mi>
    <mi data-from-mathml='mi' id='Mad3q3m6-3' data-id-added='true'>run</mi>
  </fraction>
 </math>

MathML expression:

<p>
    <math>
        <mfrac> <mi>rise</mi> <mi>run</mi> </mfrac>
    </math>
</p>

Expression 4

ERROR - mathPres.MathCAT.MathCAT.MathCATInteraction.reportFocus (13:12:08.275) - MainThread (14828):
Traceback (most recent call last):
  File "mathPres\MathCAT\MathCAT.pyc", line 81, in reportFocus
OSError: Internal error: With en/ClearSpeak in Enhanced mode, can't ZoomIn from expression with id 'Mrk4ti72-2' inside:
 <math data-from-mathml='math' id='Mrk4ti72-0' data-id-added='true'>
  <fraction data-from-mathml='mfrac' id='Mrk4ti72-1' data-id-added='true'>
    <fraction data-from-mathml='mfrac' id='Mrk4ti72-2' data-id-added='true'>
      <mn data-from-mathml='mn' id='Mrk4ti72-3' data-id-added='true'>10</mn>
      <mi data-from-mathml='mi' id='Mrk4ti72-4' data-id-added='true'>n</mi>
    </fraction>
    <fraction data-from-mathml='mfrac' id='Mrk4ti72-5' data-id-added='true'>
      <mn data-from-mathml='mn' id='Mrk4ti72-6' data-id-added='true'>2</mn>
      <mi data-from-mathml='mi' id='Mrk4ti72-7' data-id-added='true'>n</mi>
    </fraction>
  </fraction>
 </math>

MathML expression:

<p>
    <math>
        <mrow>
            <mfrac>
            <mrow>
            <mfrac>
                <mn>10</mn>
                <mi>n</mi>
            </mfrac>
            </mrow>
            <mrow>
            <mfrac>
            <mn>2</mn>
            <mi>n</mi>
            </mfrac>
            </mrow>
            </mfrac>
            </mrow>
        </math>
</p>

SimpleSpeak

Navigation mode: It's not possible to change the navigation mode for the expressions where an error occur.

Summary: I think the navigation is not working for expressions following the default rule. However, I don't get an error message when I navigate in the expression below:

<p>
    <math>
        <mrow>
        <mfrac>
            <mrow>
            <mfrac>
                <mn>1</mn>
                <mn>2</mn>
            </mfrac>
            </mrow>
            <mrow>
            <mfrac>
                <mn>2</mn>
                <mn>3</mn>
            </mfrac>
            </mrow>
        </mfrac>
        </mrow>
    </math>
</p>

Expression 1

Error message:

ERROR - mathPres.MathCAT.MathCAT.MathCATInteraction.reportFocus (13:18:14.306) - MainThread (18584):
Traceback (most recent call last):
  File "mathPres\MathCAT\MathCAT.pyc", line 81, in reportFocus
OSError: Internal error: With en/SimpleSpeak in Enhanced mode, can't ZoomIn from expression with id 'Mlahttqj-2' inside:
 <math data-from-mathml='math' id='Mlahttqj-0' data-id-added='true'>
  <fraction data-from-mathml='mfrac' id='Mlahttqj-1' data-id-added='true'>
    <mrow data-from-mathml='mrow' id='Mlahttqj-2' data-id-added='true'>
      <mi data-from-mathml='mi' id='Mlahttqj-3' data-id-added='true'>x</mi>
      <mo data-from-mathml='mo' id='Mlahttqj-4' data-id-added='true'>+</mo>
      <mi data-from-mathml='mi' id='Mlahttqj-5' data-id-added='true'>y</mi>
    </mrow>
    <mrow data-from-mathml='mrow' id='Mlahttqj-6' data-id-added='true'>
      <mi data-from-mathml='mi' id='Mlahttqj-7' data-id-added='true'>x</mi>
      <mo data-from-mathml='mo' id='Mlahttqj-8' data-id-added='true'>-</mo>
      <mi data-from-mathml='mi' id='Mlahttqj-9' data-id-added='true'>y</mi>
    </mrow>
  </fraction>
 </math>

MathML expression:

<p>
    <math>
        <mrow>
        <mfrac>
        <mrow>
        <mi>x</mi><mo>+</mo><mi>y</mi></mrow>
        <mrow>
        <mi>x</mi><mo>-</mo><mi>y</mi></mrow>
        </mfrac>
        </mrow>
    </math>
</p>

Expression 2

Error message:

ERROR - mathPres.MathCAT.MathCAT.MathCATInteraction._do_navigate (13:19:20.453) - MainThread (18584):
Traceback (most recent call last):
  File "mathPres\MathCAT\MathCAT.pyc", line 159, in _do_navigate
OSError: Internal error: With en/SimpleSpeak in Enhanced mode, can't ZoomIn from expression with id 'Msk4m6wu-5' inside:
 <math data-from-mathml='math' id='Msk4m6wu-0' data-id-added='true'>
  <mrow data-from-mathml='mrow' id='Msk4m6wu-1' data-id-added='true'>
    <mn data-from-mathml='mn' id='Msk4m6wu-2' data-id-added='true'>62</mn>
    <mo data-from-mathml='mo' data-changed='added' id='Msk4m6wu-3' data-id-added='true'>&#x2062;</mo>
    <fraction data-from-mathml='mfrac' id='Msk4m6wu-4' data-id-added='true' data-intent-property=':unit:'>
      <unit data-from-mathml='mi' id='Msk4m6wu-5' data-id-added='true' data-intent-property=':unit:'>mi</unit>
      <unit data-from-mathml='mi' id='Msk4m6wu-6' data-id-added='true' data-intent-property=':unit:'>hr</unit>
    </fraction>
  </mrow>
 </math>

MathML expression:

<p>
    <math>
        <mrow>
        <mn>62</mn>
        <mfrac>
        <mi intent=':unit'>mi</mi>
        <mi intent=':unit'>hr</mi>
        </mfrac>
        </mrow>
    </math>
</p>

Expression 3

Error message:

ERROR - mathPres.MathCAT.MathCAT.MathCATInteraction.reportFocus (13:20:25.092) - MainThread (18584):
Traceback (most recent call last):
  File "mathPres\MathCAT\MathCAT.pyc", line 81, in reportFocus
OSError: Internal error: With en/SimpleSpeak in Character mode, can't ZoomIn from expression with id 'Mekd0nor-2' inside:
 <math id='Mekd0nor-0' data-id-added='true'>
  <mfrac id='Mekd0nor-1' data-id-added='true'>
    <mi id='Mekd0nor-2' data-id-added='true'>rise</mi>
    <mi id='Mekd0nor-3' data-id-added='true'>run</mi>
  </mfrac>
 </math>

MathML expression:

<p>
    <math>
        <mfrac> <mi>rise</mi> <mi>run</mi> </mfrac>
    </math>
</p>

Expression 4

Error message:

ERROR - mathPres.MathCAT.MathCAT.MathCATInteraction.reportFocus (13:23:19.219) - MainThread (18584):
Traceback (most recent call last):
  File "mathPres\MathCAT\MathCAT.pyc", line 81, in reportFocus
OSError: Internal error: With en/SimpleSpeak in Character mode, can't ZoomIn from expression with id 'M3r2jm8j-3' inside:
 <math id='M3r2jm8j-0' data-id-added='true'>
  <mfrac id='M3r2jm8j-1' data-id-added='true'>
    <mfrac id='M3r2jm8j-2' data-id-added='true'>
      <mn id='M3r2jm8j-3' data-id-added='true'>10</mn>
      <mi id='M3r2jm8j-4' data-id-added='true'>n</mi>
    </mfrac>
    <mfrac id='M3r2jm8j-5' data-id-added='true'>
      <mn id='M3r2jm8j-6' data-id-added='true'>2</mn>
      <mi id='M3r2jm8j-7' data-id-added='true'>n</mi>
    </mfrac>
  </mfrac>
 </math>

MathML expression:

<p>
    <math>
        <mrow>
            <mfrac>
            <mrow>
            <mfrac>
                <mn>10</mn>
                <mi>n</mi>
            </mfrac>
            </mrow>
            <mrow>
            <mfrac>
            <mn>2</mn>
            <mi>n</mi>
            </mfrac>
            </mrow>
            </mfrac>
            </mrow>
        </math>
</p>

[MartheGjelstad]

@AndersEkl and @TimArborealis , have you started testing the updated navigation file, and are you experiencing the same problems as me?

[NSoiffer]

I spent many frustrating hours trying to track the problem down and finally came to the conclusion that what I told you about where to place the file is wrong: there are two copies of libmathcat_py.pyd in NVDA. I don't know why. Although the rules directory is in C:\Program Files\NVDA\include\nvda-mathcat\assets along with libmathcat_py.pyd, there is another location for libmathcat_py.pyd: C:\Program Files\NVDA. That is apparently the one to change.

Please close this issue if using that location solves your problem.

I've done a rebuild of MathCATForPython. It includes the fix for the bad SSML strings. You can find the new pyd file there. It's the 64 bit zipped file.

There is also a rebuilt addon for both versions of NVDA. I tried the 64-bit version for 2026.1 and much to my surprise, it seems to mostly work in the latest NVDA -- I guess they fixed something from one of the later betas. There seems to be some issues switching languages (if you aren't reading the math in the speech language NVDA uses, it doesn't speak correctly). There might be other issues, but the speech and navigation worked for me if you install the addon. I also uninstalled the addon and everything was back to working as before. The preferences are not being shared.

[MartheGjelstad]

@NSoiffer, I replaced the libmathcat_py.pyd file with your new build in C:\Program Files\NVDA. I also tried to restart my computer. I still get the errors when I try to navigate in the expressions.

@NSoiffer , do I need a beta version of NVDA to test the rebuilt addon? I can't find MathCAT in the addon store for NVDA 2026.1.1

[TimArborealis]

I just tested the same expressions as Marthe, having placed the new libmathcat_py.pyd file in C:\Program Files\NVDA. The navigate.yaml file having been translated directly from the new Norwegian version with no structurural differences. I get the same results as Marthe, except for some reason there are no error messages in the NVDA log (only "Fel vid navigering av matematik" verbally and in the speech window).

[MartheGjelstad]

@TimArborealis , I found the error messages in the log. Did you look there?

[TimArborealis]

I did, but there is nothing there.

[hjy1210]

@MartheGjelstad
After using the new version of libmathcat_py.pyd(with size 3921KB) provided by @NSoiffer above, all five formula you provided can be navigated and change navigation mode when navigating. The results seems correct for me.

Note: my translation is based on english version of navigate.yaml in main branch at commit #0becf66.

[MartheGjelstad]

@hjy1210 The libmathcat_py.pyd I am using has the same size as the one you are using. I also think we are using the same english navigate.yaml as base. It was last updated on April 26, and the commit you are refering to is from May 25.

Maybe I should try to reinstall NVDA and see if that solves my problems.

[hjy1210]

@MartheGjelstad MathJax create MathML from latex expression. How to create following MathML with attribute intent=':intent' by MathJax?

<math>
    <mrow>
    <mn>62</mn>
    <mfrac>
    <mi intent=':unit'>mi</mi>
    <mi intent=':unit'>hr</mi>
    </mfrac>
    </mrow>
</math>

[MartheGjelstad]

The intent attribute is part of MathML 4, which is still a work in progress (https://www.w3.org/TR/mathml4/). I am not an expert on MathJax, but I don't think it supports the intet attribute.

[MartheGjelstad]

@NSoiffer , @hjy1210 , @TimArborealis , it worked to reinstall NVDA! I can now navigate in the expressions.