experiencing a client-side error when users select options from an external_select element in the new Slack gantry-v2 web client. The same code works perfectly in the older Slack desktop client.
{"subtype":"missing_subtype","message":"Cannot read properties of undefined (reading 'text')","stack":"TypeError: Cannot read properties of undefined (reading 'text')\n at formatSingleOption
When it occurs:
- Error happens when user selects an option from the dropdown
- Dropdown loads and displays options correctly
- Only fails on selection in gantry-v2 client
- Works fine in older Slack desktop client
Our response format (confirmed correct per Block Kit docs):
{"ok": true, "options": [ {"text": { "type": "plain_text", "text": "abc-abc", "emoji": true }, "value": "abc" } ]}
#Slack Developers
Hello Sujay,
The formatSingleOption error in the new Slack gantry-v2 web client seems to be a client-side bug, as the same external_select payload works correctly in the older Slack desktop client. The error message indicates that the new client may not be handling option data properly after selection, even though your response format follows the correct Block Kit structure. Since this issue occurs only in the gantry-v2 client and not elsewhere, it’s likely a regression on Slack’s side rather than an issue with your code. The best approach is to report it to Slack’s developer support or through their API bug form, providing details about the behavior and the difference between the two client versions. Hope this helps!
