Building an app with Nova

From a description to an app

When you describe a new app in chat, Nova first works out its purpose, who uses it, what it records, and how each workflow behaves from start to finish. It also covers the lists people need, access, navigation, and setup outside the app. An independent review checks that design before construction starts. Nova asks questions only when an answer materially changes the app or isn't safe to assume.

Shared lists are part of that design. When the same facilities, products, or other values should serve several questions or app surfaces, Nova can design a Project data table once and point each use at it. Drafting and review do not change Project data. After the reviewed design is accepted, Nova creates the approved table and its rows before it starts constructing the app. If the design would change a table that other apps can already use, Nova explains that Project-wide effect and asks for approval first.

The live status immediately above the chat box names the current phase. Nova also gives a conservative rough estimate based on the design's assigned effort level: about 30 minutes for compact designs, an hour for standard designs, and 90 minutes for extended designs. Internal design submissions and technical review details stay out of the conversation.

No placeholder app appears while that design is still being worked out. The first app you see contains a coherent, valid workflow that you can open in the builder. Its tree stays read-only around the build progress while Nova adds the remaining parts as valid updates, so you never edit underneath the initial build. Direct editing and Preview become available when the whole build is finished; unfinished private work never appears in the app.

Resume an unfinished design

An app design that has not produced its first workflow appears under Designs in progress on the app list. Choose Resume to return to the same conversation and continue from its saved stage. Choose Discard when you no longer want Nova to take that design further.

Nova saves completed parts of a large design as it works. If the connection, server process, or model context is interrupted, it resumes from that exact saved work instead of rewriting completed sections. Only a complete, checked design advances to review or construction. Nova derives construction work from the accepted workflows, so it can't silently omit part of the design.

If the final check reveals that an included workflow still needs a decision from you, Nova returns to the question card and keeps the design in progress. It does not describe that unfinished workspace as reviewed or start building around the missing decision.

If you tell Nova that more requirements are coming, it saves its current design work and waits for your next message. The design remains in progress and the status changes to show that Nova needs input. It does not treat a conversational pause as a finished design or require you to restate what was already decided.

The design also has its own recovery address as soon as the first chat turn starts. Refreshing the page returns to that design. If the app was created while an update was lost in transit, Nova opens the authoritative app instead of starting a second copy.

If a later step stops

The app remains available when its first workflow was saved and a later part of the build stops. Open its app card to inspect what committed, but Nova keeps the initial-build editor locked and does not call that partial plan complete. A failed later step does not invalidate or hide the working revision that already exists. Temporary provider, connection, and database interruptions resume the same saved attempt automatically. A schema, validation, compiler, or budget failure stops as an internal build defect; Nova does not ask you to retry or reduce the accepted workflows. A time-budget stop is a rare backstop rather than a design problem: everything already saved stays intact, and once Nova's build limits are updated, a fresh build message in the same chat retries the same accepted plan without a new design instruction. When a temporary failure has already closed its connection cleanly and cannot auto-reconnect, Resume build continues the same accepted plan from its last durable workflow without adding a new design instruction. That action remains available after a refresh and appears only to Project members who can edit the app.

Start with a blank app

Choose Start with a blank app when you want to begin directly in the builder. That path creates Nova's smallest valid Survey, Form, and Question starter immediately, without the reviewed conversational design flow.

As the app grows, submenus can group related modules under one top-level menu. Nova supports one child level and keeps menu placement separate from parent-case relationships.

XPath that will run in CommCare

Nova checks formulas against the functions CommCare's device runtime actually implements and the same formulas run in Preview. A function being part of XPath 1.0 or XPath 2.0 is not enough by itself. Functions that CommCare does not provide are refused while you edit, before they can cause a runtime error for a worker.

Nova can also accept a small extension when it has an exact, tested translation to the device runtime. For example, you may write normalize-space(...) in the visual XPath editor; Nova exports an equivalent expression made from CommCare's native functions. CommCare HQ case-search formulas are checked separately because their server-side function list is different from the device's.

Nova never saves a formula that its owning Preview surface cannot faithfully run. Existing apps keep that guarantee when support changes: Nova continues to run their formulas or migrates them without changing their meaning. A defensive Preview error is treated as a Nova bug and contained so the rest of the Builder stays available; it is not an expected state the author needs to repair.

Lookup-table formulas use Nova's table and column references, which keep their identity when a table tag changes. Raw XPath can use the stable casedb and commcaresession instances, but it cannot name a lookup table by its mutable wire tag.

A form's After submit links decide where the app goes once the form is submitted, and their conditions run after the form has closed. They can use the case the form just saved and worker information, but they cannot read answers from the form that just closed. Nova refuses those form-local references instead of exporting navigation that will fail on the device.

External setup

Some workflows depend on work outside the app, such as providing an existing media asset or configuring an automation in CommCare HQ. Nova names those prerequisites and never claims that it completed them. Preview does not pretend to run external automations. One design session builds one app in your current Project; if a request describes several apps, Nova asks which one to build first.