Slack Developer Changelog Recap: July – September 2026

As summer fades into fall, we’ve got a fresh harvest of updates for you! We’ve been hard at work on new features and updates to make your work life simpler, more pleasant, and more productive.

Announcements

What’s old, what’s new, and what might need some action from you!

• The next wave of the Agent messaging experience, and the deprecation of assistant_view. The Assistant messaging experience (assistant_view) will be deprecated in February 2027. The assistant-related methods that power it are being replaced by a new Agent messaging experience (agent_view) and new set of API methods, the Agent Sessions API. Agent sessions allow users to manage their conversations with your agent in one place with a status, a title, and a stop button. The agents.sessions.setStatus and agents.sessions.rename API methods replace the assistant.threads.setStatus and assistant.threads.setTitle API methods, respectively. See the Agent sessions guide to get started. For now, your existing calls keep working. If your app still uses assistant_view, follow the migration guide to move to the new experience.
• More Agent updates. We’ve released a set of improvements related to the agent experience: a newly renamed and revamped Agents & Tools tab with a landing page to help users find popular agents, an improved thread experience including multi-agent stacking, thread naming, a revamped thinking UI, and a native stop button for agent streams, UI refinements to the plan and task card blocks; Marketplace data that now appears in an agent’s About tab; and a new sidebar with pin/archive/unread and live updates. Read more in the guide to developing agents.
• Announcing Slack Code. Slack Code is how agents and people work together to build with AI in Slack, creating dedicated channels for more involved work. Within a session, agents can publish artifacts for people to oversee and iterate on: code diffs so people can review what changed, Block Kit views for structured interactive experiences, HTML previews for prototypes and generated interfaces, and canvases for longer-form content and collaboration. Refer to Slack Code: where your team and agents build together for more details.
• Announcing the Slack MCP and Skills Plugin. We introduced the Slack MCP and Skills Plugin for AI tools, which bundles a set of skills that help you develop on the Slack platform alongside the Slack MCP Server. The plugin is currently available for Claude Code and Cursor. Read the Slack MCP and Skills Plugin docs to get started.
• Agent context has landed. Agent apps can now receive context about what a user is currently viewing when they send a message. When a user has a channel, DM, thread, canvas, or list open and messages your app, Slack will pass that context automatically. Refer to the changelog entry for more details.
• Updated installation requirement for Slack Marketplace apps. As of July 2026, we require that apps submitting to the Slack Marketplace have at least 10 installations on active workspaces, up from the temporary lower threshold. Your app needs to stay at 10 or more installed workspaces throughout the entire duration of the review.
• Desktop notifications now pull text from blocks first. Slack desktop client notifications now pull text from blocks first, falling back to the top-level text field only if no text can be extracted from blocks. Mobile notifications continue to exclusively use message.text.

Slack CLI updates

The command line interface for quickly creating, developing, and deploying Slack apps. Here’s what’s new in the Slack CLI.

• The Slack CLI now recommends the official Slack plugin to Claude Code users.
• We reduced the verbose output when using create --app to link an existing app during project creation.
• We added a --category flag to the slack docs search command.
• When the CLI errors because a prompt must be shown while in a non-TTY environment (AI agents, devops scripts, etc.), the error message now displays the prompt and, for app and team selection, the matching flags to select an option.
• We added the slack manifest diff command, which prints differences between the project manifest and the app settings.
• We added the slack blocks preview command to open Block Kit blocks in the Block Kit Builder.
• We added the slack app request command, which checks the status of your most recent request to have an app approved for install.
• We added support for custom app icons. The slack run and slack deploy commands can now be used to upload an icon file.
• The CLI falls back to manifest.json when the get-manifest hook is unavailable.
• We added the slack manifest sync command to sync the app manifest between project and app settings.
• We added a --manifest-source flag to the run and deploy commands.
• We added support for the code_channels app manifest feature.
• Bug fixes:
  • We fixed a recurring unable_to_parse_json error caused by empty JSON files (credentials, config, or app state) left behind by an interrupted write; the CLI now treats them as empty state and recovers automatically.
  • We fixed the help template so hidden subcommands are no longer listed under their parent command.
  • We fixed an issue where interactive selection prompts left lingering rendered lines on screen after a selection is made.

Bolt updates

Updates to our Bolt frameworks, the quickest way to build an app on the Slack platform.

Bolt for JavaScript v5.0.0 is here! This release follows the Node Slack SDK’s shift from axios to the native Fetch API, removes the deprecated Workflow Steps from Apps feature, and raises the minimum Node.js version to 20. If your app doesn’t use proxy/TLS configuration or inspect respond() return values, this upgrade is possibly only a version bump. For full migration details, see the Bolt for JS v4 to v5 migration guide.

SDK updates

Updates to our in-language wrappers for the most commonly used parts of the Slack platform.

Node Slack SDK received new major versions across multiple packages. All packages now require Node.js 20 or later, which is the only breaking change for the following packages:

• The cli-hooks package has been updated to v2.
• The cli-test package has been updated to v4.
• The logger package has been updated to v5.
• The oauth package has been updated to v4.
• The types package has been updated to v3.

Three packages have more substantial breaking changes, most of which fall under the theme of HTTP transport improvements, such as migrating from axios to the native Fetch API:

• The socket-mode package has been updated to v3. See the guide on migrating @slack/socket-mode from v2 to v3.
• The web-api package has been updated to v8. See the guide on migrating @slack/web-api from v7 to v8.
• The webhook package has been updated to v8. See the guide on migrating @slack/webhook from v7 to v8.

That’s a wrap on this quarter’s highlights! Keep building and let us know what you think by submitting feedback to feedback@slack.com or by reaching out to us on GitHub.