GPT 6 Luna: cheapest smart paid model for OpenCode

Introduction

GPT 6 Luna is the small member of the GPT 6 family (Astra, Sol, Luna) on OpenCode Console. It is the cheapest smart paid model: roughly ten cents per 1M input tokens, yet good enough as a full agent — it follows tools, keeps context, and survives long refactors. Use it as the step-up when Muse Spark 1.3 Free is rate-limited, for overnight runs, and for CI jobs where every cent counts. Reserve Claude Opus 5.5 for the hard final pass.

Pricing and ids

Endpoint family:

https://opencode.ai/inference/v1/responses

Context: Luna is cheaper than most Flash, Nano and Mini models at comparable quality as an agent. Verify current prices in the Console models docs before budgeting.

Connect in OpenCode

Same Console key as Spark, then pin Luna as default or per-agent:

{ "$schema": "https://opencode.ai/config.json", "model": "opencode/gpt-6-luna" }

One-shot review from CI with no TUI:

opencode run --standalone --model opencode/gpt-6-luna "Review this repository for correctness and summarize issues"

Skills and agents fit

Luna likes checklist skills: preconditions, diff-before-write, exact test command, stop conditions. Best matches from Five complete examples: db-migrate and git-release. In the aredel repo it owns page plus blocks plus verify. Agent side, it runs builder: edits allowed, tests allowed, push denied. Pair it with @test-writer for coverage on every feature.

Example workflow

Routine paid build after free triage:

With builder and @test-writer, add cursor pagination to orders with three tests, show git diff --stat and stop

Use the reviewer subagent with @api-review on git diff --cached

Luna does the implementation steps, then hands the staged diff to Claude Opus 5.5 for the verdict. For background work set the review command to subagent: true and keep typing in the parent.

Privacy and limits

Paid Console requests follow the provider data policy with limited retention for safety, unlike the free contributor tier that may train on prompts. Luna is therefore the default for customer code that Muse Spark 1.3 Free must not see. Set monthly workspace limits and review opencode stats --cost --models weekly — Luna is cheap per token but long sessions still add up.

Troubleshooting

• Over 272K pricing jump: long sessions cross the threshold — enable compaction with a keep.tokens budget and commit mid-way.
• Weak planning: switch to Plan mode first, then back to Build; do not let Luna edit on the first prompt for hard features.
• CI cost creep: pin Luna for CI, keep Opus for manual final review only.

Official sources:

• opencode.ai/v2/docs
• opencode.ai/docs/console/models

Article author: Arthur Isaev