# Extend Oracle Fusion Safely With Sandboxes And Visual Builder Studio > Source: https://netray.co/erp-help/fusion-visual-builder-sandbox-extensions > Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems. > Section: ERP Help ## Short answer Fusion customizations - a new field, a validation rule, a redesigned page layout, or a standalone custom app - are built inside a sandbox, an isolated workspace that lets you make and test changes without affecting other users until you explicitly publish. Application Composer handles fields, objects, and business rules; Visual Builder Studio builds new standalone pages and full custom applications that can embed inside or sit alongside Fusion. ## Kind how-to ## System oracle-fusion ## Erp Oracle Fusion Cloud ERP ## Module Application Composer / Visual Builder Studio / Sandboxes ## Query how to extend Oracle Fusion with Visual Builder and sandboxes ## Alternate Queries - Oracle Fusion sandbox setup for customization - Visual Builder Studio vs Application Composer Fusion - publish sandbox changes Oracle Fusion - Oracle Fusion custom page Visual Builder extension ## Applies To Oracle Fusion Cloud ERP, SCM, and HCM, all monthly updates; Application Composer and Visual Builder Studio (VBS) ## Steps ### Build and publish a Fusion extension safely **Items:** Open Navigator > Configuration > Sandboxes (or the Setup and Maintenance sandbox tool) and create a new sandbox scoped to the tools you need - Application Composer, Page Composer, or Visual Builder. Activate the sandbox; while active, your session shows the isolated version of the application, and changes you make are invisible to other users until publish. For field-level or object-level changes - a custom field, a formula field, a validation rule, a new child object - use Application Composer inside the active sandbox. For UI layout changes to an existing page - rearranging, hiding, or renaming regions and fields on a standard page - use Page Composer, also scoped to the sandbox. For a new standalone page, embedded component, or a fuller custom application, open Visual Builder Studio, create or open a VB application, and build against Fusion's REST APIs or a Fusion-provided business object. Test thoroughly inside the sandbox - functional behavior, security, and any integration touchpoints - since sandbox testing is your only safety net before the change becomes visible to everyone. Publish the sandbox once validated; publishing merges the change into the mainline and makes it visible to all users - there is no per-user rollback after publish, only a new corrective change. For Visual Builder applications, use VB Studio's separate deployment lifecycle (dev, test, production environments) rather than treating a Fusion sandbox as the VB app's own environment management. ## Sections ### What A Sandbox Actually Isolates **Body:** A sandbox is a metadata-level isolation layer: your changes to fields, page layouts, or business rules exist only within that sandbox's context until published, so other users continue seeing the current production configuration. It is not a separate database or a full environment clone - transactional data is shared and live throughout, only the customization metadata is isolated. ### Application Composer Vs Page Composer **Body:** Application Composer changes the data model: new fields, objects, relationships, validation rules, and object workflow rules that affect how data behaves regardless of which page displays it. Page Composer changes presentation only: which fields show on a specific page, their order, labels, and visibility, without touching the underlying object. A requirement that sounds like a UI change sometimes actually needs an Application Composer field first, with Page Composer only placing it on the page. ### When To Reach For Visual Builder Studio Instead **Body:** Application Composer and Page Composer extend existing standard pages and objects. When the requirement is a genuinely new page, a mobile-friendly custom form, or an application that combines Fusion data with an external source, Visual Builder Studio builds it as a proper application - with its own REST-based data model, UI components, and deployment pipeline - that can be embedded in Fusion navigation or run standalone. ### Publishing Discipline **Body:** Because publishing a sandbox is a one-way merge visible to everyone, treat sandbox testing as seriously as any pre-production testing cycle: verify with realistic data, check security role visibility for the new field or page, and confirm the change does not break an existing integration that depends on the object's prior shape. A bad publish is corrected with another published change, not a rollback. ## Pitfalls - Making changes directly without an active sandbox where the tool allows it, losing the isolation and testing safety net sandboxes exist for. - Confusing a presentation change (Page Composer) with a data model change (Application Composer) and building the wrong one for the requirement. - Publishing a sandbox without testing security role visibility for a new field, so it either leaks to users who should not see it or is invisible to users who need it. - Treating a Fusion sandbox as if it were a full environment clone with isolated transactional data - it is not; live data is shared throughout. - Building a genuinely new page or application inside Application Composer's limits instead of using Visual Builder Studio, fighting the tool for a requirement it was not designed for. - Letting multiple people work unscoped changes in the same sandbox without coordinating, causing conflicting or overwritten customizations at publish time. ## Ai Angle For a customization request, ERPray grounded on your Fusion configuration can tell you upfront whether it needs an Application Composer field, a Page Composer layout change, or a full Visual Builder Studio page - and check whether a similar field or rule already exists - so a team is not building a sandbox change that duplicates existing metadata or picks the wrong tool for the requirement. ## Faq ### Can two people work in the same sandbox at once? **Answer:** Technically yes if they both activate it, but it is risky - unscoped concurrent changes in one sandbox can overwrite or conflict with each other at publish time. Most implementations scope sandboxes per change or per developer and merge carefully, rather than sharing one sandbox freely. ### What happens to my sandbox changes if I never publish them? **Answer:** They remain isolated indefinitely and never affect other users; you can also explicitly discard a sandbox to remove the changes entirely if the customization is abandoned, without any cleanup needed in production. ### Do Visual Builder Studio applications live inside the same sandbox as Application Composer changes? **Answer:** No. VB Studio applications have their own project and environment lifecycle (dev, test, production) separate from a Fusion sandbox, even though a VB application can be embedded into Fusion's navigation and call Fusion's REST APIs or business objects. ### Can I roll back a published sandbox change? **Answer:** Not directly - publishing merges the change into the mainline for all users. If a published change needs to be undone, you create and publish a new corrective sandbox change rather than reverting to a prior state automatically. ## Search terms Oracle Fusion sandbox customization, Application Composer vs Page Composer, Visual Builder Studio Oracle Fusion, Fusion sandbox publish changes, Oracle Fusion custom field how to, Visual Builder Fusion custom application, Oracle Fusion Page Composer layout, VB Studio Fusion REST API extension --- Talk to an engineer: https://netray.co/contact?intent=erp_ai | Machine catalog: https://netray.co/agent/catalog.json