Handling errors when sending messages to the bot

Is it an issue related to Adaptive Cards?

No

Is this an accessibility issue?

No

What version of Web Chat are you using?

Latest production

Which distribution are you using Web Chat from?

Bundle (webchat.js)

Which hosting environment does this issue primarily affect?

Web apps

Which browsers and platforms do the issue happened?

Browser: Chrome (latest)

Which area does this issue affect?

Others or unrelated

Which theme pack does this issue affect?

I did not test it on other theme packs

What is the public URL for the website?

No response

Please describe the bug

When the bot fails to respond and the Direct Line POST /v3/directline/conversations/{id}/activities returns an error (e.g., 502 Bad Gateway), Web Chat does not render any error message or system notification. I also can't find a way to register a listener for that error to display any custom messages outside of the chat or perform any actions.

The user sees no feedback in the transcript; only the browser console logs the 5xx. This creates the impression that the bot ignored the message.

Is there any way to register a listener and display the message sending error? Since none of the listeners used are called when this error occurs.

Do you see any errors in console log?

botframework-webchat.js:2  POST https://directline.botframework.com/v3/directline/conversations/xxxxxxxxxxx/activities 502 (Bad Gateway)
o @ botframework-webchat.js:2
t.send @ botframework-webchat.js:2
t @ botframework-webchat.js:2
t._subscribe @ botframework-webchat.js:2
e._trySubscribe @ botframework-webchat.js:2
e.subscribe @ botframework-webchat.js:2
e.call @ botframework-webchat.js:2
e.subscribe @ botframework-webchat.js:2
e.call @ botframework-webchat.js:2
e.subscribe @ botframework-webchat.js:2
e.call @ botframework-webchat.js:2
e.subscribe @ botframework-webchat.js:2
t.subscribeToResult @ botframework-webchat.js:2
t._innerSub @ botframework-webchat.js:2
t._tryNext @ botframework-webchat.js:2
t._next @ botframework-webchat.js:2
t.next @ botframework-webchat.js:2
t._next @ botframework-webchat.js:2
t.next @ botframework-webchat.js:2
t.notifyNext @ botframework-webchat.js:2
t._next @ botframework-webchat.js:2
t.next @ botframework-webchat.js:2
t.dispatch @ botframework-webchat.js:2
t._execute @ botframework-webchat.js:2
t.execute @ botframework-webchat.js:2
t.flush @ botframework-webchat.js:2
setInterval
t.requestAsyncId @ botframework-webchat.js:2
t.schedule @ botframework-webchat.js:2
e.schedule @ botframework-webchat.js:2
t._subscribe @ botframework-webchat.js:2
e._trySubscribe @ botframework-webchat.js:2
e.subscribe @ botframework-webchat.js:2
t.subscribeToResult @ botframework-webchat.js:2
t._innerSub @ botframework-webchat.js:2
t._tryNext @ botframework-webchat.js:2
t._next @ botframework-webchat.js:2
t.next @ botframework-webchat.js:2
t._next @ botframework-webchat.js:2
t.next @ botframework-webchat.js:2
t.notifyNext @ botframework-webchat.js:2
t._next @ botframework-webchat.js:2
t.next @ botframework-webchat.js:2
t.dispatch @ botframework-webchat.js:2
t._execute @ botframework-webchat.js:2
t.execute @ botframework-webchat.js:2
t.flush @ botframework-webchat.js:2
setInterval
....

How to reproduce the issue?

1. Render Web Chat with Direct Line (minimal sample below).

2. Start a normal conversation with the bot.

3. After the bot's first successful response, cause the bot endpoint to fail (stop the bot or return HTTP 5xx).

4. Send another message.

What do you expect?

A way to register a listener and display the message sending error

What actually happened?

There is no visible error or way to listen for that message sending error when you get an error code from the API

Do you have any screenshots or recordings to repro the issue?

Adaptive Card JSON

Additional context

No response

Start by reproducing the failure with the bundled webchat.js and a Direct Line POST /v3/directline/conversations/{id}/activities that returns HTTP 5xx. Trace how the failed send is surfaced beyond the browser console, then verify that the transcript shows feedback or exposes a listener for the sending error.