Working on Smartphone: How I Freed Myself from PC with Genspark + Termux + Claude Code + Gemini CLI

Table of Contents

For 20 years as a software engineer, I've been glued to my PC for work. Currently, I'm independent, doing web and social media consulting, and app development. The conclusion I've reached is, "Do I really need a PC anymore?" In fact, I do almost all my work on my smartphone, except for tasks that require a large screen. In this article, I'll realistically introduce the tools I actually use and concrete methods for smartphone development.

What You'll Learn in This Article

How to build a "smartphone-only development environment" combining Genspark, Termux, Claude Code, and Gemini CLI, along with a realistic evaluation of each tool by a 20-year engineer.

Conclusion from a 20-Year Engineer: "No Need for a PC Anymore"

For me, having worked as an engineer for many years, the PC was the central tool for my work. However, with the rapid evolution of AI tools, that premise is fundamentally changing. The era has arrived where serious development and document creation can be done on a single smartphone, whether you're commuting, out and about, or on your couch at home.

I completely understand how those who feel "smartphone development is impossible" feel. I thought so too at first. However, the evolution of AI technology is breaking down that conventional wisdom. Especially the rise of Genspark and its combination with Android's Linux environment "Termux" have greatly expanded the possibilities of smartphone development.

Three Obstacles to Smartphone Migration and AI Breakthroughs

Three tasks that were difficult to migrate to a smartphone were PowerPoint document creation, application development, and website/blog creation. These tasks can now be sufficiently handled on a smartphone by using AI tools.

Task Previous Obstacle Current Solution
PowerPoint Document Creation Difficult to manipulate layouts on a smartphone Genspark's AI Slide Feature
Application Development Lack of IDE/terminal environment on smartphones Termux + Claude Code / Gemini CLI
Website/Blog Creation Coding and deployment assume a PC Genspark + Termux + Claude Code
For PowerPoint documents, "Genspark is the only choice."

By simply entering themes and key points, it automatically generates well-designed slides. It can be operated from a smartphone browser, and the output quality is commercial level. As of 2026, Genspark is the most practical slide creation tool for smartphones.

Overview and Use Cases of the Tools

Organizing my actual workflow, it follows this pattern: "Conception and prototyping with Genspark, detailed implementation with Termux + Claude Code, and then Gemini CLI when the billing limit is reached." I will explain each role.

It is technically possible to complete app development solely with Genspark. However, doing everything with Genspark leads to heavy credit consumption. Therefore, I feel that a division of labor where Genspark handles concept consideration, image creation, and prototype creation, while Termux + Claude Code or Gemini CLI handles detailed implementation, modifications, and deployment, is the optimal solution in terms of cost-performance.

Why Web version Claude or Firebase didn't work?

The web version of Claude was not practical because it was blocked by Cloudflare's security (bot countermeasures), making it inaccessible. Also, Firebase currently has low AI integration capabilities and was not practical for my use cases. For development requiring access to external services, Termux is currently the most flexible option.

Genspark: The Ultimate Weapon for Slide Creation and Prototyping

Genspark can be used directly from your browser. No special installation is required; just access it from Chrome or Safari on your smartphone. You can start using it immediately by signing up with your Google account from the official website.

The situation where I use it most often is during the conceptual stage of a new app. By simply broadly stating "I want to create an app with these features," it proposes screen design, technology stack, and even implementation order. By entrusting this prototype design phase to Genspark, subsequent implementation work with Termux becomes significantly smoother.

How to Use Genspark to Save Credits

① Give specific initial instructions (vague instructions lead to multiple interactions and credit consumption), ② Clearly specify the output volume (e.g., "5 slides," "500 words"), ③ Instruct only for differences when making corrections (e.g., "change only the title of the 3rd slide"). Being mindful of these three points can significantly reduce credit consumption.

Termux + Claude Code: Installation Steps for Serious Development

Termux is an app that allows you to run a Linux environment on your Android smartphone. By using it, terminal operations typically only possible on a PC can be performed on your smartphone.

Termux Installation

Termux can also be installed from Google's Play Store, but the Play Store version of Termux is no longer actively developed. For the latest features and packages, the F-Droid version is recommended. (I personally use the Play Store version as it works fine for my needs, but I generally recommend the F-Droid version.)

Node.js & Claude Code Installation

Once Termux is launched, execute the following commands in order.

pkg update && pkg upgrade
pkg install nodejs
npm install -g @anthropic-ai/claude-code

Resolving the /tmp Access Issue (Important)

If you launch Claude Code as is, an error stating "cannot access /tmp" will occur, rendering Bash commands unusable. By using the termux-chroot command, a standard Linux environment including /tmp is emulated, resolving this permission issue. Please execute the following commands before launching Claude.

pkg install proot
termux-chroot
claude
Note for Using Wrangler (Cloudflare)

The Wrangler command for accessing Cloudflare servers is not officially supported on Termux. Attempting to install it manually is very difficult, so the shortcut is to ask Claude Code to install it. If you ask it to "install wrangler on Termux," it will autonomously try methods like faking Linux to install incompatible libraries or ignoring them.

Termux + Gemini CLI: The Ace for Maximizing Free Tier Usage

For detailed setup instructions for Gemini CLI, please refer to the previous article (Termux + Gemini Utilization Guide). Here, I will primarily introduce the use cases for Gemini CLI compared to Claude Code.

Currently, I find Claude Code easier to use. However, Gemini CLI has a quite generous free tier, making it valuable when Claude Code's usage limits are reached. Even when you hit "today's billing limit...", you can continue development by switching to Gemini CLI. For more details, please also refer to the Gemini CLI Official GitHub.

Notes on Installing Gemini CLI on Termux

Gemini CLI is also unofficially supported on Termux, so a regular `npm install` will result in errors midway. The solution is to skip installation scripts using the `--ignore-scripts` option. For detailed steps, please see this article.

Honest 5-Star Review of Each Tool's Usability

This is my subjective evaluation when operating from a smartphone. Each has its pros and cons, but this evaluation table should help you understand why I adopt a strategy of "using the best parts of each tool selectively."

Evaluation Item Genspark Termux＋Claude Code Termux＋Gemini CLI Web Version Claude Firebase
AI Agent Capability ⭐⭐⭐⭐（4） ⭐⭐⭐⭐⭐（5） ⭐⭐⭐（3） ⭐⭐⭐⭐⭐（5） ⭐（1）
Smartphone Usability ⭐⭐⭐⭐⭐（5） ⭐⭐⭐⭐（4） ⭐⭐⭐⭐（4） ⭐⭐⭐⭐⭐（5） ⭐⭐⭐（3）
Cloudflare Access ⭐⭐⭐⭐⭐（5） ⭐⭐⭐⭐（4） ⭐⭐⭐⭐（4） ✗（0） ⭐（1）
Cost ⭐⭐（2） ⭐⭐⭐⭐（4） ⭐⭐⭐（3） ⭐⭐⭐⭐（4） ⭐⭐⭐⭐⭐（5）
Explanation of Evaluation Points

Genspark scores highest in UI/operability and Cloudflare access, but its cost is lower due to high credit consumption. Claude Code offers an excellent balance of AI capability and cost, but Termux environment setup requires a bit of effort. Firebase (Google) has the highest cost-effectiveness, but its current AI agent capabilities and external access are weak, making it impractical for my use cases. The web version of Claude is high-performing, but the ban on Cloudflare access is a fatal limitation.

My Actual Workflow

① Create concepts, designs, and prototypes with Genspark → ② Implement and deploy with Termux + Claude Code → ③ Switch to Termux + Gemini CLI when Claude Code's billing limit is reached. This flow is currently the optimal solution. For a detailed comparison between Genspark and Claude Code, please refer to Claude Code vs Genspark: A Thorough Comparison.

Summary: Recommendations for a Smartphone Development Life

The era where development work can be done on a smartphone has arrived. Since I, who have been glued to a PC for 20 years, am saying this, it's neither flattery nor exaggeration. Of course, a PC still has advantages for large-screen tasks and highly complex large-scale development. However, much of daily development, modifications, deployment, and document creation can be completed on a smartphone.

Of course, smartphone development also has its drawbacks. Battery consumption is high, and checking differences in multiple files (Git Diff) can be difficult. For long hours of work, a Bluetooth keyboard is desirable, and I sometimes perform the final overall code review on a PC's larger screen. However, the fact that 80% of the work can be completed on a smartphone has dramatically lightened my workload and improved my mobility.

Summary of Smartphone Development Environment

・Slide/Document Creation → Genspark (browser-only, no installation required)
・Serious Development/Implementation → Termux + Claude Code (resolves /tmp issue with proot + termux-chroot)
・Backup Environment for Billing Limits → Termux + Gemini CLI (install workaround with --ignore-scripts)
・Cloudflare Integration → Genspark or Termux (Web version Claude not supported)

I hope this helps you in your smartphone development life. Start by trying Genspark's free plan. When you experience the feeling of "entrusting work to AI," your reliance on PCs will surely decrease.

References & Related Links

Try Genspark