Learning Timeline
Key Insights
Differences in 'Agentic' Styles
Codex tends to proceed with executing the plan without interruptions, whereas Claude Code frequently requests additional 'permission' before making file changes.
Output Strengths vs. Weaknesses
Claude Code is often 'over-ambitious' by adding complex UI (such as gradient backgrounds), but it occasionally introduces bugs into the app logic. Codex is simpler and remains focused on the requested features, which typically results in better stability.
Claude Troubleshooting Tips
If Claude produces inconsistent results, note that Anthropic has acknowledged recent API stability issues. Using the Opus model can help yield more accurate results for the time being.
Prompts
Basic Pomodoro App Building Prompt
Target:
Codex CLI & Claude Code
Build a simple pomodoro timer app with start, pause, and reset buttons. Show the countdown. 25 minutes by default. switch to a 5m minute break after each session and loop the cycle. Use clean, minimal UI
Feature Addition Prompt (Iteration)
Target:
Codex CLI & Claude Code
implement multi-timer functionality and adjustable durations.
Step by Step
How to Build an App Using GPT-5 Codex CLI
- Open your terminal or command line interface (CLI).
- Type the command `codex` to activate the agent.
- Ensure the 'GPT-5 Codex' model is selected or active in the session.
- Enter the prompt to build the app (refer to the Prompt Card) and press Enter.
- Watch as Codex plans and executes the code writing automatically (Codex typically doesn't ask for permission repeatedly).
- Once completed, review the list of generated files (e.g., `index.html`).
- Type the command `open index.html` directly from the CLI to view the app in your browser.
How to Build an App Using Claude Code
- Open a separate terminal or CLI window.
- Type the command `claude` to start the session.
- Switch the model to 'Opus' by typing the model-change command for optimal performance.
- Enter the same prompt used with Codex.
- Provide Permission when Claude asks for confirmation to create or modify files by typing 'y' or 'yes'.
- Review the feature summary provided by Claude once the code generation is finished.
- Open the generated HTML file in your browser to test the timer functionality.
