Slack · ui · fg-0360

Link button in a Slack message shows a warning icon after the user clicks it

Small warning triangle next to a URL button after click

Verified 2026-10-15 · Confirmed by 0 builders · Trust 50/100

Cause

A button with a url still sends a block_actions payload to the app, and Slack expects a 200 within three seconds. With no listener, the request fails and the client shows the warning. Slack staff confirmed this is intended.

Fix

Register a listener for the button's action_id that only acknowledges.

Apply

app.action("open_report", async ({ ack }) => { await ack(); });

Affects: Slack desktop and web clients, Block Kit buttons with url, all versions as of 2026-10

Sources

• https://github.com/slackapi/node-slack-sdk/issues/869

claude mcp add --transport http footgun https://getfootgun.com/api/mcp