How Bolt Won the Native Financial Calculator Showdown: A Vibe Coder’s Retrospective

Introduction

Building a native-feel financial calculator app—with offline capability, real-time interactivity, and a polished UI—can be deceptively complex. As developers, we lean on AI-assisted tools to accelerate scaffolding, enforce best practices, and minimize tedious iteration. Recently, I benchmarked two leading AI-powered assistants—Bolt and Cursor—against a shared objective: deliver an Android-only Expo SDK 53 app featuring both an EMI calculator and a Goal Planner. Here’s how the two tools stacked up.

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Experiment Setup

Bolt Prompt

A concise, single-sentence request:

1. Build me a native React Native Android app for EMI calculation with real-time sliders, synchronized text inputs, and export-ready structure.

Cursor Prompt

A detailed brief mirroring every build requirement:

1. • Calculator types, real-time feedback, pie chart output, form validation, Expo SDK 53 compatibility, type-safe components.

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Bolt’s Experience: One Clean Shot

• Folder Structure: Immediately generated logical components/, screens/, and utils/ folders.

• SDK Compatibility: Brought in the correct Expo 53 dependencies out of the box.

• Interactive Preview: Loaded instantly in Expo Go—no manual tweaks.

• UI Synchronization: Sliders and inputs stayed in lockstep, with polished styling baked in.

• Test Suite: Delivered Jest tests for calcEMI(), calcMonthlySIP(), and calcLumpSum() right alongside the functions.

• Deployment: Project was EAS-build-ready without additional configuration.

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Cursor’s Struggle: Fifty Iterations Later

Despite the detailed prompt, Cursor’s output required substantial manual intervention:

• Broken Structure: Components scattered, imports misaligned.

• Version Mismatch: Incorrect React/Expo combo leading to runtime errors.

• UI Glitches: Sliders often failed to update fields; layout margins inconsistent.

• No Preview: Expo Go would error out until dependency versions were fixed by hand.

• Testing Omitted: No unit tests generated; calculation logic had to be extracted and wrapped manually.

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Side-by-Side Comparison

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Why Bolt Resonates with Vibe Coders

For those of us who pride ourselves on crafting “vibes” rather than just code, Bolt delivers:

• Speed: One prompt, one project.

• Reliability: Adheres to specified SDK and architecture.

• Polish: Out-of-the-box UI consistency and instant previews.

• Cleanliness: Well-structured code and automatic tests.

Cursor’s powerful agent layer shows promise, but until it masters spec fidelity and dependency alignment, it can’t match Bolt for truly native mobile builds.

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Conclusion

In real-world app development, time saved on setup and iteration directly translates to better focus on UX nuances, edge-case handling, and performance tuning. Bolt’s single-shot success on this financial calculator—complete with unit tests and APK readiness—makes it a clear winner for developers who demand both speed and quality.

If you’ve tried Bolt or Cursor in your own projects, I’d love to hear your experiences and war stories in the comments. Let’s keep elevating our coder vibes together.