[BUG] Unable to login using the Mac app

[robinandeer]

Issue

Unable to login using the Desktop app "Unable to Sign In"

How to reproduce

1. Open Desktop app
2. Click on Sign in
3. See error

Unable to Sign In
We couldn't complete your sign-in because the redirect address doesn't match what's registered.

Expected Behavior

The OAuth flow completes as expected.

Screenshots

Platform

• Mac App

Additional Context

Login is fine using npx

[dosubot]

Hi @robinandeer! I'm Dosu and I'm helping the MCPJam team.

This matches a bug that was fixed in PR #3590. The root cause: macOS only routes a custom URL scheme (mcpjam://) to apps that declare it in CFBundleURLTypes (Info.plist). The desktop app's sign-in flow opens WorkOS in the system browser and depends on the browser navigating to mcpjam://oauth/callback to hand the auth code back [1] — but without the bundle declaration, macOS has no registered handler for that scheme, so the browser dead-ends with the "redirect address doesn't match" error.

The runtime call app.setAsDefaultProtocolClient("mcpjam") in src/main.ts covers Windows/Linux but is documented as unsupported on macOS. The fix added a protocols entry to forge.config.ts so the mcpjam scheme is properly declared in the macOS bundle [2].

Updating to the latest release (after PR #3590 was merged on July 31) should fix this. The npx path works because it uses a different redirect mechanism (loopback) rather than the custom protocol scheme, which is why sign-in succeeds there.

To reply, just mention @dosu.

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Docs are dead. Just use Dosu.

[ZeHuari]

Thanks for the report @robinandeer — we reproduced it and know what's going on.

The app needs port 6274, and only one program can use a port at a time. If something else already has it, the desktop app quietly switches to 6275 — and sign-in breaks, because only 6274 is approved with our auth provider.

That's why npx worked for you: the CLI was holding 6274, so the desktop app got pushed off it. You can only run one at a time right now.

Workaround: close the CLI inspector and any other running instance, then open the desktop app and sign in. It should work.

We're fixing it on our side so the port no longer matters

(Side note: not a Mac-only issue, we reproduced it on Windows. And the bot comment above isn't the right explanation.)