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GPT-5.6 Luna logo

GPT-5.6 Luna

OpenAI · Released Jun 2026

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GPT-5.6 Luna is OpenAI's budget tier: near-GPT-5.5 capability at $0.20 input and $1.20 output per 1M tokens at short context, after OpenAI's 80% price cut on 30 July 2026. Generally available via the API and Codex, it is the cheapest route into the GPT-5.6 family for high-volume agent, extraction and routing work. Remains conditional: all benchmarks are vendor-reported, Luna lacks activation classifiers, and it is not in the standard ChatGPT picker.

Is it right for you?

Good for

  • Best capability-per-dollar in the GPT-5.6 family: TerminalBench 2.1 at 82.5% is only 0.9 points behind GPT-5.5 (83.4%) at $0.20 input / $1.20 output per 1M, against Sol's $4 / $20. For high-volume agentic workflows, Luna is the economics winner.
  • Speed and throughput: positioned as the fastest GPT-5.6 model, optimized for latency-sensitive products, agent swarms, customer support, and real-time classification pipelines.
  • Routine automation and extraction: classification, summarization, formatting, routing, draft generation, and background automation where cost-per-request and throughput dominate over raw reasoning depth.
  • Model-routing architectures: the bottom tier of a Sol > Terra > Luna escalation ladder. Use Luna by default, escalate to Terra or Sol when Luna's eval score drops below threshold on a specific task.

Not good for

  • Long-context jobs budgeted off the headline rate: past short context Luna bills $0.40 input and $1.80 output per 1M tokens.
  • CTF score of 85.19% is the lowest in the family: solid but not dominant. For security-critical workflows, Terra or Sol are the appropriate tier.
  • Lacks the safety depth of Sol and Terra: no activation classifiers on Luna (per system card). For regulated cyber and bio workflows, use Terra or Sol with full monitoring stack.
  • Buying purely on lowest list price: DeepSeek's V4.1-Flash lists $0.15 input / $0.60 output per 1M off-peak, below Luna on both, though its weekday peak input rate ($0.30) is higher.

How it performs by task

High-volume agentic coding (budget)

Very Good

82.5% on TerminalBench 2.1 is only 0.9 behind GPT-5.5. Remarkable for a budget tier. Route routine coding tasks to Luna, escalate complex ones.

Classification and extraction

Excellent

The ideal model for cheap, high-throughput tasks. Classification, entity extraction, sentiment, routing, and formatting at $0.20/$1.20 per 1M is the economics win of the GPT-5.6 family.

Summarization and drafting

Very Good

Fast and affordable for document summarization, email drafting, report generation, and content workflows where speed matters more than extreme precision.

Cybersecurity

Good

CTF 85.19% is solid for a budget model but trails Terra (91.84%) and Sol (96.7%). No activation classifiers. Not the right tier for security-critical work.

Hard reasoning and deep research

Fair

Budget tier with no max or ultra reasoning modes. For hard problems, route to Sol. For everyday reasoning, Terra. Luna is for volume, not depth.

Pricing

Input

$0.20 / 1M tokens

Output

$1.20 / 1M tokens

Context

Short $0.20/$1.20 · long $0.40/$1.80 per 1M

View full pricing

Benchmarks

BenchmarkScoreSource
TerminalBench 2.182.5% Source
Internal CTF (capture-the-flag)85.19% Source

Verdict history

Sep 11, 2026
conditional -> conditional (stale price corrected) — No rating change. The standing summary still priced Luna at $1/$6 per 1M six weeks after OpenAI's 30 July cut, while the entity's own pricing fields already read $0.20/$1.20. OpenAI's API pricing page, fetched 11 September 2026, lists gpt-5.6-luna at $0.20 input / $1.20 output short context and $0.40 / $1.80 long context; the API changelog states 'Starting July 30, GPT-5.6 Luna costs 80% less'. Summary corrected; children that still claimed government-gated access or $1/$6 were corrected in the same pass.
Jul 22, 2026
pending -> conditional — Reached general availability on July 9, 2026. Pricing held stable at $1/$6 through GA. Now accessible to all developers. Remains conditional: vendor-reported benchmarks, no activation classifiers, no standard ChatGPT access.
Jul 16, 2026
copy edit to brevity standard, detail preserved in children — Density rewrite: compressed 176w/9s to ~70w/3s per the 55–90w verdict_summary standard. Benchmark scores, pricing detail, audience fit, and per-task ratings remain in strengths[], benchmarks[], task_strengths[], and verdict_audiences[].

Sources

Verification log

  • Pricing— Updated

    Automated agent

    Rates re-verified: pricing page row gpt-5.6-luna, verbatim 'Short context input $0.20 | Short context cached input $0.02 | Short context output $1.20 | Long context input $0.40 | Long context cached input $0.04 | Long context output $1.80'. API changelog Jul 30 2026: 'Starting July 30, GPT-5.6 Luna costs 80% less'. Stored pricing_input/output ($0.20/$1.20) were already correct; the PROSE was not (stale self-authored prose class). FIXED: pricing_context 'Fastest tier. 80% cut Jul 30 -> $0.20/$1.20.' -> 'Short $0.20/$1.20 · long $0.40/$1.80 per 1M'; pricing_url from the openai.com Sol preview blog to the developers pricing page; removed the false avoid_for 'Government-gated with no public access' (contradicted by its own 2026-07-22 GA transition and by the public price list); removed the false avoid_for 'At $1/$6 ... DeepSeek V4 Pro ($0.44/$0.87)' (both prices stale) and replaced it with a sourced lowest-list-price row (DeepSeek deepseek-flash $0.15/$0.60 off-peak, fetched today); added a long-context rate avoid_for; removed the false not_for_whom 'Teams without trusted-partner access ... gated'; corrected '$1/$6' in one audience and one task_strength and dropped the stale '1/5 Sol's cost' ratio. Summary still said '$1/$6': corrected via standalone verdict_set (conditional -> conditional, verdict 086bbfcc-b426-4124-b7ef-84024fbcd95c) because no announcing post exists for a six-week-old price cut; no draft created, not news.

  • Pricing— No changes

    Automated agent

  • Pricing— No changes

    Automated agent

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    Automated agent

  • Pricing— No changes

    Automated agent

  • Status— Updated

    Automated agent

    Summary re-dated to Jul 7 2026 and made explicit about what is awaited: stays pending pending GA + independent benchmarks; still government-gated (~20 orgs); family trending toward release (~Jul 9 GA per prediction markets, unconfirmed). Verdict unchanged (pending).

  • Pricing— No changes

    Automated agent

  • Pricing— No changes

    Automated agent

    Pricing unchanged: $1/$6 per 1M tokens. Government-gated. Confirmed by OpenAI blog.

  • Pricing— No changes

    Imported at launch

  • Profile— No changes

    Imported at launch

How we evaluate