Cannot react with `+:reaction_name:` syntax - setReaction not found

[Brenton-Keats]

Search before asking

• I had searched in the issues and found no similar issues.

Operating System

• macOS
• Windows
• Linux

Operating System Version

macOS 26.5.2

It happens on the web browser too?

Yes, it happens on the web browser too

Rocket.Chat Desktop App Version

4.15.4

Rocket.Chat Server Version

8.5

Describe the bug

Attempting to react to a message by typing +:reaction_name: (e.g. "+:grin:") does not correctly add the action. It is displayed in the client, but not received by other clients and reloading the app will remove the (non-existent) reaction.

When creating the reaction, two error alerts appear in the top-right corner stating "Method 'setReaction' not found"

How to Reproduce

1. Open any channel, thread, or direct message with any messages
2. Type a reaction e.g. +:grin: and send the message.
3. Observe the errors, and the reaction being displayed in the history.
4. (optional) verify the reaction has not appeared from another client. This may be a different client from the same device (e.g. web + desktop)
5. Reload the client that the reaction was posted from. Observe the reaction is no longer shown.

Describe your Expected behavior

Adding a reaction with the previously-working syntax should... add the reaction.

Anything else

• Occurs every time
• Clicking on the "non-existent" reaction icon will actually add the reaction, making it observable from other clients (though ordinarily, clicking the icon removes the reaction first time). Clicking on it again removes it as expected.

Are you willing to submit a code contribution?

• Yes, I am willing to submit a Pull Request!

[flynng42]

This is also reproducible in v4.15.6