Measuring Codex Pro Runtime: Astra(low) + Luna(max) Subagents

Melvin Vivas · X post · 2026-09-08 · Open on X

Topics: AI Agents, Tool Use & MCP, AI Dev Tools & Productivity, LLMOps, Deployment & Monitoring · Level: intermediate

Summary

Melvin Vivas reports real usage figures from Codex Pro (5x). A one-hour run with Astra (low reasoning) as orchestrator and Luna (max reasoning) as subagents used about 7% of the weekly limit. From that he estimates about 14.3 hours of runtime per week, and notes that a run using only Astra would burn limits faster.

Key points

• Setup: Astra at low reasoning as orchestrator, Luna at max reasoning as subagents.
• A 1-hour run left 93% of the weekly Pro 5x limit.
• That projects to about 14.3 hours of total runtime per weekly limit.
• Delegating to Luna subagents lowers usage; Astra alone would use limits faster.
• Measure usage per hour of runtime to plan your agent budget.

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
• GPT 5.6 Luna · tool · openai.com · paid
  The OpenAI model used inside Codex for the demo. The transcript gives the variant name as 'Soul', which is unclear.
  Also in: Set Codex subagent model and reasoning to save usage limits (Melvin Vivas on X · notes), Use GPT-5.6 Luna in Codex for Terminal Tasks (Melvin Vivas on X · notes), Match Reasoning Effort to Task Length in Codex (Astra/Sol) (Melvin Vivas on X · notes), Run Coworker desktop agents cheaply with GPT-5.6 Luna on OpenRouter (Melvin Vivas on X · notes) and 24 more

Try this

• Track the % of your weekly limit used per hour of runtime to estimate your total budget.