diff --git a/backend/src/helpers/slack/slack-post-message.ts b/backend/src/helpers/slack/slack-post-message.ts
index b8b3391c1..1005b1058 100644
--- a/backend/src/helpers/slack/slack-post-message.ts
+++ b/backend/src/helpers/slack/slack-post-message.ts
@@ -1,3 +1,4 @@
+import Sentry from '@sentry/minimal';
 import axios from 'axios';
 import { appConfig } from '../../shared/config/app-config.js';
 import { Constants } from '../constants/constants.js';
@@ -17,8 +18,20 @@ export async function slackPostMessage(message: string, channel = Constants.DEFA
 			},
 			{ headers: { authorization: `Bearer ${slackBotToken}` } },
 		);
+		const data = res.data as { ok?: boolean; error?: string };
+		if (data && data.ok === false) {
+			// Slack accepted the HTTP call but refused the post (revoked token, unknown channel…).
+			// Slack is the ops pager — it silently failing is itself an incident, so report through
+			// the one channel that still works. Cannot use WinstonLogger here (it imports this helper).
+			console.error(`slackPostMessage rejected by Slack API: ${data.error}`);
+			Sentry.captureMessage(`slackPostMessage rejected by Slack API: ${data.error}`);
+		}
 		return res.data;
-	} catch (_e) {
+	} catch (e) {
+		// Same reasoning as above: a broken alerting channel must not be invisible. Still swallowed —
+		// posting must never affect the operation that triggered it.
+		console.error('slackPostMessage failed:', e);
+		Sentry.captureException(e);
 		return;
 	}
 }