Fix markdown cursor restore crash on IOU description focus

[x-dev90]

Explanation of Change

Fixes a web crash in the IOU Description step where live-markdown cursor restoration could call Range.setStart / Range.setEnd with an offset larger than the actual DOM node length.

Fixed Issues

$ #95347
PROPOSAL: #95347 (comment)

Tests

Forced browser repro

Script

const input =
    document.querySelector('[aria-label="What\\\'s it for?"][contenteditable="true"]') ||
    [...document.querySelectorAll('[contenteditable="true"]')].find((el) => el.getAttribute('aria-label')?.includes("What's it for?"));

if (!input) {
    throw new Error('Markdown description input not found');
}

input.focus();

const walker = document.createTreeWalker(input, NodeFilter.SHOW_TEXT);
const textNode = walker.nextNode();

if (!textNode) {
    throw new Error('No text node found. Type text in the description first.');
}

// Save a caret position near/end of the current text.
const range = document.createRange();
range.setStart(textNode, textNode.length);
range.collapse(true);

const selection = window.getSelection();
selection.removeAllRanges();
selection.addRange(range);

// Let live-markdown cache contentSelection.
input.dispatchEvent(new Event('select', {bubbles: true}));

// Blur, then mutate only the rendered DOM text node.
// This keeps the markdown tree stale while making the DOM node shorter/empty.
input.blur();
textNode.textContent = '';

// Refocus. Before the fix this should call setCursorPosition with stale offsets
// and throw IndexSizeError from Range.setStart / setEnd.
input.focus();

1. Open NewDot on web.
2. Start creating an expense.
3. Choose Manual, enter an amount, and go to the Description step.
4. Type text into the description field, for example abcdef.
5. Open DevTools Console.
6. Run the forced desync script from above
7. Click the description input again.
   • No IndexSizeError is thrown.
   • The app remains usable.
   • The cursor is restored to a valid position.

• Verify that no errors appear in the JS console

Offline tests

Same as tests.

QA Steps

Product flow

1. Open NewDot on web.
2. Start creating an expense.
3. Choose Manual, enter an amount, and go to the Description step.
4. Type or edit the description.
5. Press Back to trigger the discard changes modal.
6. Click Cancel.
7. Confirm the modal closes and focus returns to the description input
   • No crash or console error.
   • The description input remains usable.
   • The entered description is preserved.

// TODO: These must be filled out, or the issue title must include "[No QA]."

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
• I wrote clear testing steps that cover the changes made in this PR
  • I added steps for local testing in the Tests section
  • I added steps for the expected offline behavior in the Offline steps section
  • I added steps for Staging and/or Production testing in the QA steps section
  • I added steps to cover failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
  • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
  • I tested this PR with a High Traffic account against the staging or production API to ensure there are no regressions (e.g. long loading states that impact usability).
• I included screenshots or videos for tests on all platforms
• I ran the tests on all platforms & verified they passed on:
  • Android: Native
  • Android: mWeb Chrome
  • iOS: Native
  • iOS: mWeb Safari
  • MacOS: Chrome / Safari
• I verified there are no console errors (if there's a console error not related to the PR, report it or open an issue for it to be fixed)
• I followed proper code patterns (see Reviewing the code)
  • I verified that comments were added to code that is not self explanatory
  • I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
  • I verified any copy / text that was added to the app is grammatically correct in English. It adheres to proper capitalization guidelines (note: only the first word of header/labels should be capitalized), and is either coming verbatim from figma or has been approved by marketing (in order to get marketing approval, ask the Bug Zero team member to add the Waiting for copy label to the issue)
• If a new code pattern is added I verified it was agreed to be used by multiple Expensify engineers
• I followed the guidelines as stated in the Review Guidelines
• I tested other components that can be impacted by my changes (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar are working as expected)
• If a new CSS style is added I verified that:
  • A similar style doesn't already exist
  • The style can't be created with an existing StyleUtils function (i.e. StyleUtils.getBackgroundAndBorderStyle(theme.componentBG))
• If new assets were added or existing ones were modified, I verified that:
  • The assets are optimized and compressed (for SVG files, run npm run compress-svg)
  • The assets load correctly across all supported platforms.
• If the PR modifies code that runs when editing or sending messages, I tested and verified there is no unexpected behavior for all supported markdown - URLs, single line code, code blocks, quotes, headings, bold, strikethrough, and italic.
• If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
• If the PR modifies a component related to any of the existing Storybook stories, I tested and verified all stories for that component are still working as expected.
• If the PR modifies a component or page that can be accessed by a direct deeplink, I verified that the code functions as expected when the deeplink is used - from a logged in and logged out account.
• If the PR modifies the UI (e.g. new buttons, new UI components, changing the padding/spacing/sizing, moving components, etc) or modifies the form input styles:
  • I verified that all the inputs inside a form are aligned with each other.
  • I added Design label and/or tagged @Expensify/design so the design team can review the changes.
• I added unit tests for any new feature or bug fix in this PR to help automatically prevent regressions in this user flow.
• If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.

Screenshots/Videos

Android: Native

Android: mWeb Chrome

Screen_Recording_20260725_122410_Chrome.mp4

iOS: Native

Screen.Recording.2026-07-27.at.10.54.47.AM.mov

iOS: mWeb Safari

Screen.Recording.2026-07-25.at.2.35.17.PM.mov

MacOS: Chrome / Safari

Screen.Recording.2026-07-22.at.5.07.12.PM.mov

[github-actions]

⚠️ This PR is possibly changing native code and/or updating libraries, it may cause problems with HybridApp. Please check if any patch updates are required in the HybridApp repo and run an AdHoc build to verify that HybridApp will not break. Ask Contributor Plus for help if you are not sure how to handle this. ⚠️

[melvin-bot]

@suneox Please copy/paste the Reviewer Checklist from here into a new comment on this PR and complete it. If you have the K2 extension, you can simply click: [this button]

[melvin-bot]

@mountiny Please copy/paste the Reviewer Checklist from here into a new comment on this PR and complete it. If you have the K2 extension, you can simply click: [this button]

[x-dev90]

@suneox, Gentle bump. thanks.

[suneox]

@suneox, Gentle bump. thanks.

I'll take a look at this one today

[suneox]

@x-dev90 Please feel free to open a PR directly in react-native-live-markdown. Expensify maintains that repo, so we can fix it upstream instead of using a patch.

Please update the PR description by moving the Product flow under QA Steps. Additionally, please attach Screenshots/Videos for the other platform to cover all QA steps per the author checklist.

[mountiny]

@suneox thanks! Can you please test the change in the app?

[suneox]

Reviewer Checklist

• I have verified the author checklist is complete (all boxes are checked off).
• I verified the correct issue is linked in the ### Fixed Issues section above
• I verified testing steps are clear and they cover the changes made in this PR
  • I verified the steps for local testing are in the Tests section
  • I verified the steps for Staging and/or Production testing are in the QA steps section
  • I verified the steps cover any possible failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
  • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
• I checked that screenshots or videos are included for tests on all platforms
• I included screenshots or videos for tests on all platforms
• I verified that the composer does not automatically focus or open the keyboard on mobile unless explicitly intended. This includes checking that returning the app from the background does not unexpectedly open the keyboard.
• I verified tests pass on all platforms & I tested again on:
  • Android: HybridApp
  • Android: mWeb Chrome
  • iOS: HybridApp
  • iOS: mWeb Safari
  • MacOS: Chrome / Safari
• If there are any errors in the console that are unrelated to this PR, I either fixed them (preferred) or linked to where I reported them in Slack
• I verified proper code patterns were followed (see Reviewing the code)
  • I verified that comments were added to code that is not self explanatory
  • I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
  • I verified any copy / text that was added to the app is grammatically correct in English. It adheres to proper capitalization guidelines (note: only the first word of header/labels should be capitalized), and is either coming verbatim from figma or has been approved by marketing (in order to get marketing approval, ask the Bug Zero team member to add the Waiting for copy label to the issue)
• If a new code pattern is added I verified it was agreed to be used by multiple Expensify engineers
• I verified that this PR follows the guidelines as stated in the Review Guidelines
• I verified other components that can be impacted by these changes have been tested, and I retested again (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar have been tested & I retested again)
• If a new component is created I verified that:
  • A similar component doesn't exist in the codebase
  • All props are defined accurately
  • The component has a clear name that is non-ambiguous and the purpose of the component can be inferred from the name alone
  • The only data being stored in the state is data necessary for rendering and nothing else
  • The component has the minimum amount of code necessary for its purpose, and it is broken down into smaller components in order to separate concerns and functions
• If a new CSS style is added I verified that:
  • A similar style doesn't already exist
  • The style can't be created with an existing StyleUtils function (i.e. StyleUtils.getBackgroundAndBorderStyle(theme.componentBG)
• If the PR modifies code that runs when editing or sending messages, I tested and verified there is no unexpected behavior for all supported markdown - URLs, single line code, code blocks, quotes, headings, bold, strikethrough, and italic.
• If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
• If the PR modifies a component related to any of the existing Storybook stories, I tested and verified all stories for that component are still working as expected.
• If the PR modifies a component or page that can be accessed by a direct deeplink, I verified that the code functions as expected when the deeplink is used - from a logged in and logged out account.
• If the PR modifies the UI (e.g. new buttons, new UI components, changing the padding/spacing/sizing, moving components, etc) or modifies the form input styles:
  • I verified that all the inputs inside a form are aligned with each other.
  • I added Design label and/or tagged @Expensify/design so the design team can review the changes.
• For any bug fix or new feature in this PR, I verified that sufficient unit tests are included to prevent regressions in this flow.
• If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.
• I have checked off every checkbox in the PR reviewer checklist, including those that don't apply to this PR.

Screenshots/Videos

Android: HybridApp

az_recorder_20260727_152501.1.mp4

Android: mWeb Chrome

az_recorder_20260727_152501.mp4

iOS: HybridApp

CleanShot.2026-07-27.at.15.21.37.3.mp4

iOS: mWeb Safari

CleanShot.2026-07-27.at.15.23.39.4.mp4

MacOS: Chrome / Safari

CleanShot.2026-07-27.at.12.02.33.2.mp4

[suneox]

Everything works as expected with the patch applied. We'll remove it once the library PR gets merged

[x-dev90]

@suneox The upstream PR in react-native-live-markdown has been merged and published in @expensify/react-native-live-markdown@0.1.334.

I updated this PR to use 0.1.334 and removed the temporary patch-package patch. I also retested the forced desync repro and confirmed the IndexSizeError no longer occurs.

Could you please take a look when you get a chance? thanks

[x-dev90]

@mountiny, please feel free to review the code. I’m investigating the failure action and running another round of testing. I’ll let you know once it’s complete. Thanks!

[mountiny]

Looks good but you need to also update the pods