Some commonly seen coding agents:

https://openai.com/codex/

• Though codex supports Plus subscription login directly, it still requires additional API key to call OpenAI models and thus needs additional API costs.

https://www.anthropic.com/claude-code

• Max plan at 5x level should be enough for most daily usage.
• Claude code and website / app claude share the same quota, therefore if your claude code reaches the limit, claude will be unavailable on other terminals either.

https://blog.google/technology/developers/introducing-gemini-cli-open-source-ai-agent/

• Gemini-cli could be used for free with 1000 requests per day.
• However, gemini-2.5-pro is only available for 100 interactions, while afterwards gemini-2.5-flash will take over, with a large performance drop.