Summary

Alta Flows ships with a native Slack integration that lets a workflow post a message to a Slack channel as one of its steps. You connect Slack to Alta once via OAuth, then drop a Send Message action into any flow — picking the channel from a dropdown and passing the message body as a static string or a variable from an earlier step.

Who this is for

Anyone building a workflow in Alta Flows who wants to ping a Slack channel as part of the run — e.g. notify a sales channel when a prospect books a meeting, post a deal-stage change into a revops channel, or send a daily digest into a leadership channel from a scheduled flow.

Heads-up: this is different from Slack notification routing

Don't confuse this with the Slack notifications you set up under Settings → Notifications (replies, daily plan, manual task approvals, workflow alerts). Those are Alta-managed event streams routed to a Slack channel. The Send Message action below is something you place inside a custom flow you've built — totally separate.

Before you start

You can edit flows in Alta (Workflows section).
Someone in your workspace can authorize a Slack app — you need permission to install apps in the Slack workspace, or someone who does.
The Slack channel you want to post into is either public, or private with the Alta Slack app invited (use /invite @Alta in the channel after the app is installed).

Step 1 — Connect Slack to Alta (one-time, via OAuth)

Open a flow in Workflows (or create a new one).
Add an action step and pick Slack from the integration list. The Slack tile is in the Communication category.
Pick the Send Message action.
You'll be prompted to authenticate. Click the auth button and complete the Slack OAuth screen — choose the workspace, review the requested scopes, and click Allow.
You're returned to the flow editor with Slack connected. The connection is account-level — once it's done, anyone in your Alta workspace can use Slack in their flows without re-authenticating.

Step 2 — Configure the Send Message action

Channel (required). Pick the destination channel from the dropdown. Alta loads the list of public and private channels from your connected workspace (archived channels are excluded). Description in the field: "You can get the Channel ID by right-clicking on the channel and selecting 'View Channel Details.'"
Message (required). The text body to post. This is a long-text field, so you can write multi-line messages. You can also reference variables from earlier steps in the flow using Alta's variable picker — e.g. drop in the prospect's name, a deal value from a CRM step, or output from an AI step.
Save the step.

Step 3 — Test the step, then publish the flow

Use the flow's Test controls to run a sample payload through the Slack step. A success looks like "Message sent successfully" in the step output; the message will appear in the channel almost instantly.
When you're happy, Publish the flow. The Slack step will then post on every real run.

Tips and common pitfalls

Channel dropdown is empty or says "connect slack account". The auth didn't complete. Re-run the OAuth step. If you're still empty after that, you may not have permission to install Slack apps in your workspace — ask a Slack admin.
"not_in_channel" error on a private channel. The Alta Slack app hasn't been added to that channel. Open the channel in Slack and run /invite @Alta.
Message body posts blank or shows raw template syntax. A variable reference is broken — the upstream step didn't produce that field, or the variable name is mistyped. Open the test run output, copy the actual path of the value you want, and re-insert it via the variable picker.
Markdown vs. plain text. Alta sends the message as a Slack section block with mrkdwn formatting, so Slack's mrkdwn syntax works: *bold*, _italic_, `code`, <https://example.com|link text>, line breaks via newlines. Standard Markdown (e.g. **bold**) won't render.
Channel limits. Alta lists up to 1,000 channels in the dropdown (paginated from Slack). If your workspace has more, type to filter — the dropdown searches by channel name.
The step is set to fail the run by default. Both Continue on failure and Retry on failure default to off. If you'd rather have a failed Slack post just log and move on, flip Continue on failure on for that step.
Want to send to a DM or thread? Not supported directly — the action posts to channel IDs only, as a top-level message. To DM a user, create a private channel with just that person and the Alta app.