GPT-6.1 Sol May Beat Luna for Subagents

Melvin Vivas · X post · 2026-09-30 · Open on X

Topics: AI Agents, Tool Use & MCP, LLM Fundamentals · Level: intermediate

Summary

The creator's first impression is that GPT-6.1 Sol has replaced Luna as the best model for subagents. He says he still needs to validate this.

Key points

• First impression: GPT-6.1 Sol beats Luna for subagent tasks.
• He calls it a big upgrade, but it hasn't been validated yet.
• Test new models on your own subagent workloads before switching.

Resources mentioned

• GPT-6.1 Sol · tool · openai.com · paid
  A new OpenAI model announced at DevDay 2026 (name as written in the machine transcript), offered with Fast and Ultra fast speed tiers.
  Also in: JevDev: Open-Source UI Tool for Experimenting with Jev (Typesafe.ai) (Melvin Vivas on X · notes), Comparing Coding Models on the Same Task in Devin iOS (Melvin Vivas on X · notes), 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) and 9 more
• Luna · tool · openai.com · paid
  The other model/agent the classifier routes tasks to; the post doesn't describe it further.
  Also in: Picking models for orchestrator and subagent roles in Codex (Melvin Vivas on X · notes), GPT-6 Sol Ultra Subagents Use Up Limits Fast (Melvin Vivas on X · notes), GPT-6 Sol vs Opus 5.5 in a Livestream Comparison (Melvin Vivas on X · notes), DigitalOcean Serverless Inference Now Serves OpenAI GPT-6 Models (Melvin Vivas on X · notes) and 14 more

Try this

• Compare GPT-6.1 Sol and Luna on your own subagent tasks before switching.