Measuring Codex Usage Burn Rate: Astra (high) Without Subagents

Melvin Vivas · X post · 2026-09-10 · Open on X

Topics: AI Dev Tools & Productivity, LLMOps, Deployment & Monitoring · Level: intermediate

Summary

A quick, hands-on cost test of Codex with the Astra model at the 'high' reasoning level and no subagents, covering a review, plan and code workflow. Over 17 minutes the weekly limit dropped from 64% to 62%. The post works out the burn rate and how long a full weekly limit would last. It also shows a simple way to estimate the cost of your own coding-agent setup.

Key points

• Test setup: Codex with Astra at high reasoning, no subagents, doing a review → plan → code workflow.
• Weekly usage went from 64% to 62% between 12:37 and 12:54, so 2% in 17 minutes.
• That is about 0.118% per minute, or roughly 7.1% per hour.
• At that rate a full 100% weekly limit lasts about 850 minutes (around 14h 10m) of active work.
• Next test: Astra at xhigh reasoning, which is reported to be cheaper.
• Method: note the usage % at a start and end time, then extrapolate to estimate how long your limits will last.

Resources mentioned

• OpenAI Codex · tool · openai.com · paid
  OpenAI's coding agent. In the diagram it writes code, fixes review findings and drives the build loop. The creator also used it to make this video.
  Also in: An agent bot that installs and drives Codex on its own (Melvin Vivas on X · notes), Asking a Coder bot to install Codex (Melvin Vivas on X · notes), Sign in with ChatGPT: Setting Usage Limits for Each App (Melvin Vivas on X · notes), Codex Cloud Environments Must Be Saved & Published Before Use (Melvin Vivas on X · notes) and 240 more
• GPT-6 Astra · tool · openai.com · paid
  The model announced in the quoted launch post, pitched as the developer's most capable model for work, coding, science and cybersecurity, and able to operate a computer.
  Also in: Customizing Your Coding Setup with Pi Coding Agent Extensions (Melvin Vivas on X · notes), Pi Agent Council: Ask Multiple LLMs in Parallel and Compare Their Advice (Melvin Vivas on X · notes), Use GPT-6.1 Sol by Default, Save Astra for Emergencies (Melvin Vivas on X · notes), Dots in ChatGPT: always-on AI agents that you hand responsibilities to (Melvin Vivas on X · notes) and 49 more

Try this

• Track the usage % at a start and end time to calculate your own burn rate.
• Compare reasoning levels (high vs xhigh) to see which is cheaper for your workflow.