When growing up, many of us heard the phrase “first-class citizen.” In society, it has a social or political meaning. In programming, however, it has a precise technical definition.
A first-class object (or first-class citizen) is an entity that can:
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Be assigned to a variable
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Be passed as an argument to a function
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Be returned from a function
In short, it can be treated like any other value in the language.
But what does “first-class citizen” mean inside the context of Atlassian Forge?
Forge Today: The Actual State of Things
Forge is Atlassian’s cloud-native development platform for building apps that run inside Atlassian Cloud products like:
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Jira
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Confluence
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Bitbucket
Forge was introduced as the long-term strategic direction for Atlassian Cloud extensibility.
Meanwhile, Atlassian Connect is not “dead,” but Atlassian has clearly positioned Forge as the future platform. Connect apps continue to work, but new capabilities increasingly launch on Forge first, and Atlassian encourages vendors to migrate over time.
So when we talk about “first-class citizen” in Forge, we are no longer talking about programming language semantics. We’re talking about platform priority, capability parity, and long-term viability.
UI in Forge: The Two Official Paths
Forge supports two UI approaches:
1. UI Kit
2. Custom UI
Let’s examine both - based on actual current capabilities.
UI Kit
What UI Kit actually is:
UI Kit is a declarative component framework provided by Forge. You write React-like syntax, but it runs in a controlled Forge runtime environment.
What it does well
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Tight integration with Forge backend functions
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Automatic security sandboxing
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No need to host static assets
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Simplified development for standard workflows
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Works seamlessly with Forge’s permission model
Real limitations (based on current platform behavior)
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Limited component set
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No direct DOM access
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No arbitrary third-party frontend libraries
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Limited styling flexibility
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No full control over browser APIs
UI Kit is intentionally constrained. It is designed for simplicity, security, and platform consistency - not for deep UI customization.
It is not an abstraction layer in the classical software architecture sense. It is a managed UI runtime with guardrails.
Custom UI
Custom UI is fundamentally different.
Here you:
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Build your frontend however you like (React, Vue, Svelte, vanilla JS)
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Bundle static assets
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Host them via Forge
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Communicate with backend functions via <a href="https://community.atlassian.com/forums/user/viewprofilepage/user-id/4918321">@Forge</a>/bridge
What Custom UI enables
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Full control of layout and styling
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Third-party libraries
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Advanced state management
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Complex visualizations
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Rich UX interactions
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Near-parity with modern SPA development
The trade-off:
So… Is UI Kit a First-Class Citizen in Forge?
If we use the programming definition - the answer is irrelevant. UI approaches are not values in a language.
Instead, let’s redefine first-class citizen in the context of Forge:
A first-class citizen in a platform is a capability that:
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Receives long-term investment
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Achieves feature parity with platform evolution
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Is not structurally limited compared to alternatives
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Is viable for building production-grade commercial apps
Under that definition:
UI Kit is not a “second-class” feature. It is officially supported and actively maintained. However, it is opinionated by design. It optimizes for:
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Security
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Simplicity
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Compliance
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Fast internal tooling
Custom UI optimizes for:
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Flexibility
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Power
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Complex UX
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Marketplace-grade apps
The Real Strategic Direction
Based on Atlassian’s current documentation and ecosystem guidance:
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Forge is the strategic platform.
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Custom UI is the path for advanced UI.
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UI Kit is ideal for simple extensions and structured UI use cases.
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Atlassian continues to invest in both, but Custom UI offers fewer architectural ceilings.
The Practical Conclusion
If you're building:
UI Kit is perfectly valid.
If you're building:
Custom UI is the safer long-term architectural choice.
Final Thought
In programming, a first-class citizen is about capability equality.
In Forge, being a first-class citizen is about platform priority, extensibility, and long-term viability.
UI Kit is supported.
Custom UI is unconstrained.
Forge itself is the future.
And in that ecosystem, the real first-class citizen is the approach that removes architectural ceilings before they remove your growth.
