[Fix] Automations fail to report when Roomote cannot access Slack channel

apps/api/src/handlers/mcp/slack.ts

@@ -971,16 +971,19 @@ slackMcp.post('/thread_reply', async (c) => {
     blocks.push(...imageBlocks);
     blocks.push(...rootFooterBlocks);
 
-    const rootMessageTs = await slack.postMessage({
+    const rootPost = await slack.postTopLevelMessage({
       channel: slackReplyTarget.channel,
       text: getSlackFallbackText(fallbackText, imageBlocks.length),
       unfurl_links: false,
       unfurl_media: false,
       blocks,
     });
+    const rootMessageTs = rootPost.messageTs;
 
     if (!rootMessageTs) {
-      throw new Error('Slack chat.postMessage returned no message timestamp');
+      throw new Error(
+        `Slack chat.postMessage failed${rootPost.error ? `: ${rootPost.error}` : ' without a message timestamp'}`,
+      );
     }
 
     // The root message is already visible in Slack; failing the reply here
@@ -1343,11 +1346,8 @@ slackMcp.post('/thread_reply', async (c) => {
       );
     }
 
-    if (message === 'Slack chat.postMessage returned no message timestamp') {
-      return c.json(
-        { error: 'Slack chat.postMessage returned no message timestamp' },
-        502,
-      );
+    if (message.startsWith('Slack chat.postMessage failed')) {
+      return c.json({ error: message }, 502);
     }
 
     if (message === 'Slack thread source message no longer exists') {

packages/sdk/src/server/automations/custom-automations.ts

@@ -26,6 +26,7 @@ import {
   listConnectedCommunicationProviders,
   type ResolvedAutomationDestination,
 } from './destination';
+import { getCommunicationProviderAdapter } from '../lib/communication-providers';
 import {
   isCronRunDue,
   resolveDeploymentTimeZone,
@@ -246,6 +247,28 @@ async function launchCustomAutomationRow(
       });
       return result;
     }
+
+    if (destination.provider === 'slack') {
+      const slack = await getCommunicationProviderAdapter('slack');
+      const isMember =
+        slack?.provider === 'slack'
+          ? await slack.isAppInChannel(destination.channelId)
+          : null;
+      if (isMember !== true) {
+        const message =
+          isMember === false
+            ? `Slack app cannot access report channel ${destination.channelId}. Invite the app to the channel or choose another destination.`
+            : `Slack report channel ${destination.channelId} could not be verified. Try again before running this automation.`;
+        result.skippedReason = message;
+        result.errors.push(message);
+        await recordCustomAutomationRunOutcome(db, {
+          id: automation.id,
+          status: 'failed',
+          error: message,
+        });
+        return result;
+      }
+    }
   }
 
   // The short claim fence prevents concurrent launchers from double-launching

packages/slack/src/slack-notifier.ts

@@ -886,6 +886,26 @@ export class SlackNotifier {
     return response?.ts;
   }
 
+  /**
+   * Posts a top-level message while preserving Slack's API error code for
+   * callers that need to report why a new conversation could not be created.
+   */
+  public async postTopLevelMessage(message: SlackMessage): Promise<{
+    messageTs?: string;
+    error?: string;
+  }> {
+    const response = await this.sendMessage(
+      'chat.postMessage',
+      message,
+      'regular',
+    );
+
+    return {
+      ...(response?.ts ? { messageTs: response.ts } : {}),
+      ...(response?.error ? { error: response.error } : {}),
+    };
+  }
+
   public async postEphemeralMessage(message: SlackMessage & { user: string }) {
     const response = await this.sendMessage(
       'chat.postEphemeral',