calcom/cal.com

Issue Summary

@calcom/[email protected] fails at runtime in a minimal Next.js App Router project when rendering the Booker atom from a client-only modal.

The same repro works on @calcom/[email protected]. The only intended difference between the working and failing branches is the package version and resulting lockfile changes.

Repro repo: https://github.com/mogusbi-motech/cal-com-atom-bundling-issue

Failing branch using @calcom/[email protected]: https://github.com/mogusbi-motech/cal-com-atom-bundling-issue/tree/main

Working comparison branch using @calcom/[email protected]: https://github.com/mogusbi-motech/cal-com-atom-bundling-issue/tree/working-2.6.0

The current failure appears to come from @calcom/atoms/dist/vendor/timezone-constants.js, which evaluates dayjs.tz.guess() before dayjs.tz is available.

Steps to Reproduce

1. Clone the repro:

   git clone https://github.com/mogusbi-motech/cal-com-atom-bundling-issue.git
   cd cal-com-atom-bundling-issue
   

2. Check out the failing branch:

   git checkout main
   

3. Install dependencies:

   pnpm install
   

4. Start the app:

   pnpm dev
   

5. Open the local Next.js URL.

6. Submit the form with valid Cal.com values:

   • Client ID
   • API URL, for example https://api.cal.com/v2
   • Username
   • Event slug

7. Click Open calendar modal.

For comparison, the same flow works on:

git checkout working-2.6.0
pnpm install
pnpm dev

Actual Results

• The calendar modal fails to load on @calcom/[email protected].
• The browser shows:

Unhandled Runtime Error
TypeError: Cannot read properties of undefined (reading 'guess')

Call Stack
eval
node_modules/@calcom/atoms/dist/vendor/timezone-constants.js (4:21)