feat: update 'app link' to not change the app manifest source

[mwbrooks]

Changelog

Updated slack app link command to support project's that use a manifest file as the manifest source (manifest.json).

• Does not display a warning message when the manifest source is local (project file).
• Does not change the manifest source - now uses the project's current manifest source.
• Displays the current manifest source for the developer's reference.
• Displays a tip on where to change the manifest source (.slack/config.json).

Updated the app manifest overwrite warning prompt wording and appearance.

• Clarifies that the app settings manifest will be overwritten by the project's app manifest file.
• Displays a yellow warning that changes were detected on the app settings manifest that are not in the project's app manifest file.

Summary

This pull request is a little spicy 🌶️ because remove speed bumps and reduces friction for developers to allows apps from App setting to be managed by the Slack CLI.

See Changelog section for a detailed breakdown of the changes.

Motivation

The motivation for these changes is 💬 developer feedback. A consistent theme of questions from developers is how to have the Slack CLI manage and use the manifest.json that ships with all of our sample apps (sensible question). We often need to explain how to manually update .slack/config.json → manifest.source: "local" for developers to get the experience they want.

Our concern for embracing the project's manifest file is that it can overwrite the manifest on App Settings. This could be a shocking and difficult experience, if it happens unexpectedly. Thankfully, the Slack CLI's overwrite protection has been reliable for the past year and this change leans more heavily on it.

Preview

Linking an App ID from App Setting

Currently, when Linking an App ID from App Setting, the developer is forced to switch the manifest source to be App Setting (remote). If they decline the confirmation prompt, then they cannot link the app. A workaround that developers have taken is to accept the confirmation and then manually change the manifest source back to the manifest file: .slack/config → manifest.source: "local".

Now, the manifest source is not changed - it can remain local (manifest file) or remote (app settings). We rely on the manifest overwrite protection to warn developers when there are changes on App Settings that are not in the manifest file.

Expand to see a video of the current behaviour

2026-03-13-app-link-current.mov

2026-03-13-app-link-new.mov

Overwriting App Settings Warning

We made minor wording and appearance changes to clarify that the app settings manifest will be overwritten by the manifest file.

Expand to see a video of the current behaviour

2026-03-13-overwrite-manifest-current.mov

2026-03-13-overwrite-manifest-new.mov

Test Steps

# Create a Bolt Framework project
$ lack create my-app -t https://github.com/slack-samples/bolt-js-starter-template.git
$ cd my-app/

# Start & Stop the dev server to create an App ID 
$ lack run
# → Create an app
# → Stop the server once it's running
# CTRL+C

# Copy the App ID
$ lack app list
# → Copy the App ID

# Unlink the App ID
$ lack app unlink
# → Select your App ID

# Test: App Link
$ lack app link
# → Confirm: "Manifest source is "project" (local)"
# → Confirm: "Manifest source is configured in .slack/config.json"
# → App ID: Paste the App ID
# → Environment: Local

# Test: Change App Settings
$ lack app settings
# → Add a short description
# → Add a background color
# → Save

# Test: Overwrite Warning
$ lack run
# → Confirm: Overwrite warning
# → Select "Y"
# → CTRL+C after dev server starts

# Test: Confirm No Overwrite Warning when Manifests In-Sync
$ lack run
# → Confirm: No warning and dev server starts
# → CTRL+C

# Clean up
$ lack delete -f
$ cd ..
$ rm -rf my-app/

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.89%. Comparing base (a87561b) to head (3632f26).

Files with missing lines	Patch %	Lines
cmd/app/link.go	83.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@                             Coverage Diff                              @@
##           mwbrooks-default-bolt-manifest-source-local     #396   +/-   ##
============================================================================
  Coverage                                        67.88%   67.89%           
============================================================================
  Files                                              218      218           
  Lines                                            18090    18055   -35     
============================================================================
- Hits                                             12280    12258   -22     
+ Misses                                            4655     4642   -13     
  Partials                                          1155     1155           

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[mwbrooks]

Some words for the kind reviewers!

[mwbrooks]

note(out-of-scope): We should have the default manifest source return by a common method instead of manually setting it in each spot.

[mwbrooks]

note: Test linking an app when the manifest source is local (manifest file).

[mwbrooks]

note: Test linking an app when the manifest source is remote (app settings).

[mwbrooks]

note: I'm open to other formatting (Red?) but I think we should make this pop and stand out in some way.