GPT-5.6 has been generally available since July 9. OpenAI offers Sol, Terra, and Luna across ChatGPT, Codex, and the API, with plan-dependent model and effort choices.
Use this page for current model selection and pricing. On July 30, OpenAI cut Luna’s API price by 80% and Terra’s by 20%; the Luna viability analysis checks what that changes. The June Sol preview investigation remains a dated record of the earlier access gate.
Current Access
- ChatGPT: Plus, Pro, Business, and Enterprise users can access Sol; Pro and Enterprise can also select Sol Pro.
- ChatGPT Work and Codex: Free and Go users receive Terra. Plus, Pro, Business, and Enterprise users can choose Sol, Terra, or Luna and set effort.
maxis available to users with GPT-5.6 access; Codexultrais available on Plus and higher plans. - API: Sol, Terra, and Luna are available through the OpenAI API. Account tier, region, rate limits, and organization policy can still affect effective access.
- Trusted Access: Verified defenders can request less-restricted cyber capability while ordinary production safeguards remain the default.
Family and Pricing
Prices are standard short-context rates per 1 million tokens. Cache reads apply the published 90% discount; cache writes cost 1.25 times normal input.
| Model | Position | Input | Cache read / write | Output | Current access |
|---|---|---|---|---|---|
| GPT-5.6 Sol | Flagship | $5.00 | $0.50 / $6.25 | $30.00 | ChatGPT paid plans, Codex paid plans, API |
| GPT-5.6 Terra | Balanced | $2.00 | $0.20 / $2.50 | $12.00 | ChatGPT Work/Codex including Free and Go, API |
| GPT-5.6 Luna | Fast, lowest cost | $0.20 | $0.02 / $0.25 | $1.20 | ChatGPT Work/Codex paid plans, API |
All three API model pages list a 1.05M context window, 922K maximum input, and 128K maximum output. Requests above 272K input use the long-context rates for the full request:
| Model | Long input | Long cache read / write | Long output |
|---|---|---|---|
| GPT-5.6 Sol | $10.00 | $1.00 / $12.50 | $45.00 |
| GPT-5.6 Terra | $4.00 | $0.40 / $5.00 | $18.00 |
| GPT-5.6 Luna | $0.40 | $0.04 / $0.50 | $1.80 |
OpenAI also documents explicit cache breakpoints and a 30-minute minimum cache life. Batch, Flex, Fast, regional, and tool charges are separate.
Which Tier Would Fit?
| Need | Tier to evaluate | Useful comparison |
|---|---|---|
| Hard coding, science, or cyber evaluation | Sol | GPT-5.5 or Claude Opus 4.8 |
| Balanced capability and price | Terra | GPT-5.5, Claude Sonnet 5, or GLM-5.2 |
| Lowest GPT-5.6 token price and latency | Luna | Kimi K2.7 Code, GLM-5.2, or another generally available value lane |
These are evaluation hypotheses, not production rankings. Terra’s claimed GPT-5.5 competitiveness and Luna’s speed position come from OpenAI. AIHackers has not run a controlled repository evaluation for any GPT-5.6 tier.
Benchmark Evidence
benchmark artifact
GPT-5.6 Evidence and Comparison Baselines
| Model | Provider | Status | Context | Input price | Output price | Coding signal | Tool-use signal | Benchmark evidence | Speed | Verdict | Sources | Checked |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| GPT-5.6 Sol | OpenAI | active Generally available through ChatGPT paid plans, Codex paid plans, and the OpenAI API; plan and effort options vary. | 1.05M | $5.00 / 1M | $30.00 / 1M | Artificial Analysis reports 80 on its Coding Agent Index at max effort; OpenAI reports 64.6% on SWE-bench Pro. | Generally available in API and paid Codex plans; max and ultra modes are vendor-documented. |
| OpenAI announced a selected-customer Cerebras preview for July; production latency is not verified. | Generally available flagship; test on real tasks and apply stronger controls for agentic or cyber work. | OpenAI GPT-5.6 general availability [archive], OpenAI API pricing [archive], Artificial Analysis GPT-5.6 evaluation [archive], Agent Arena leaderboard, OpenAI GPT-5.6 availability [archive], OpenAI GPT-5.6 system card | 2026-08-01 |
| GPT-5.6 Terra | OpenAI | active Generally available through ChatGPT Work, Codex including Free and Go, and the OpenAI API. | 1.05M | $2.00 / 1M | $12.00 / 1M | Artificial Analysis reports 77 on its Coding Agent Index at max effort; OpenAI reports 63.4% on SWE-bench Pro. | Generally available in API and Codex, including the Free and Go Codex lane. |
| not verified | Generally available balanced lane; compare accepted-task cost with Sol, Luna, and other providers. | OpenAI GPT-5.6 general availability [archive], OpenAI GPT-5.6 price update [archive], OpenAI API pricing [archive], Artificial Analysis GPT-5.6 evaluation [archive], Agent Arena leaderboard, OpenAI GPT-5.6 availability [archive], OpenAI GPT-5.6 system card | 2026-08-01 |
| GPT-5.6 Luna | OpenAI | active Generally available through paid ChatGPT Work/Codex plans and the OpenAI API. | 1.05M | $0.20 / 1M | $1.20 / 1M | Artificial Analysis reports 75 on its Coding Agent Index at max effort; BenchLM ranks Luna #6/129 in coding with an Estimated overall position. | Generally available in API and paid Codex plans. |
| Vendor-positioned as fastest; measured production latency is not verified. | Generally available lowest-cost GPT-5.6 tier; verify quality and cost per accepted task. | OpenAI GPT-5.6 general availability [archive], OpenAI GPT-5.6 price update [archive], OpenAI API pricing [archive], OpenAI GPT-5.6 Luna model page [archive], Artificial Analysis GPT-5.6 evaluation [archive], Agent Arena leaderboard, BenchLM GPT-5.6 Luna profile [archive], OpenAI GPT-5.6 availability [archive], OpenAI GPT-5.6 system card | 2026-08-01 |
| GPT-5.5 | OpenAI | active Generally available prior-generation OpenAI model retained for existing integrations and comparisons. | 1.05M API; 400K Codex | $5.00 / 1M | $30.00 / 1M | not verified | not verified | not verified | not verified | Primary coding seat while ChatGPT/Codex limits fit the workload. | OpenAI GPT-5.5 API model page, OpenAI GPT-5.5 ChatGPT limits, Artificial Analysis: GPT-5.5, LMArena leaderboard dataset | 2026-06-28 |
| Claude Opus 4.8 | Anthropic | historical Still available, but superseded by Opus 5 for current premium comparisons. | 1M | $5.00 / 1M | $25.00 / 1M | Historical premium Claude baseline; use Opus 5 for new task-level comparisons. | Still available for pinned integrations; new Claude premium routing should test Opus 5. |
| Artificial Analysis measured 57.3 output tokens/s; provider and workload latency vary. | Historical premium baseline. Use Claude Opus 5 for current Claude premium routing. | Claude models overview [archive], Claude API pricing [archive], Artificial Analysis: Claude Opus 4.8 [archive], Artificial Analysis Intelligence Index v4.1, LMArena leaderboard dataset, Berkeley Function Calling Leaderboard | 2026-07-25 |
| GLM-5.2 | Z.AI | active Current Z.AI flagship coding model and supported-tool value lane. | 1M | $1.40 / 1M | $4.40 / 1M | Z.AI reports 62.1 on SWE-Bench Pro and 81.0 on Terminal-Bench 2.1. | Supported-tool coding lane; BFCL score not imported. |
| Artificial Analysis flags higher output-token use; measure total cost per successful task. | July value pick to test for supported coding-tool workflows; keep Opus/GPT for final arbitration until local evals pass. | Z.AI GLM-5.2 overview [archive], Z.AI pricing [archive], Artificial Analysis: GLM-5.2 article [archive], Artificial Analysis Intelligence Index v4.1, SWE-bench, Berkeley Function Calling Leaderboard | 2026-06-28 |
| Kimi K2.7 Code | Moonshot AI | active Cheaper routine Kimi coding API lane; HighSpeed is the same model at higher token prices. | 256K | $0.95 / 1M | $4.00 / 1M | Kimi K2.7 Code remains the lower-cost 256K coding lane after K3; independent normalized benchmarks are not imported. | OpenAI-compatible API; thinking mode required in the documented K2.7 Code quickstart. |
| HighSpeed model ID exists at a higher token price; latency not independently measured here. | Cheaper routine Kimi coding API lane when Kimi routing fits and 256K context is enough. | Kimi K2.7 Code quickstart [archive], Kimi K2.7 Code pricing [archive], Kimi Code K2.7 release notes [archive], SWE-bench, Berkeley Function Calling Leaderboard | 2026-06-28 |
GPT-5.6 is generally available, but its listed benchmark results remain vendor-reported. Site-owned cost-per-successful-task and repository quality are not verified.
OpenAI’s July 9 launch and system card publish an expanded evaluation suite for the family. Artificial Analysis independently reports max-effort Intelligence Index scores of 59 for Sol, 55 for Terra, and 51 for Luna, plus Coding Agent Index scores of 80, 77, and 75. Its cost-per-task fields still use the higher launch prices, so they are not current after July 30.
Agent Arena ranked Sol xHigh #4, Terra xHigh #17, and Luna xHigh #18 when checked August 1. BenchLM placed Luna #6/129 in its coding category, but its overall #25/214 position is Estimated. These are shortlist signals, not an AIHackers result: site-owned CAR and repository testing remain not-run.
Do not combine these benchmark families into one percentage:
- Terminal-Bench 2.1 tests command-line agent tasks.
- GeneBench v1 covers long-horizon genomics and quantitative biology.
- ExploitBench and ExploitGym cover security workflows.
- Artificial Analysis provides a separate independent aggregate for models it has evaluated.
- Cost per successful task still requires the same real task, harness, completion rules, retries, and review process.
Deployment Gate
Before production routing:
- Confirm the exact model ID and approved API organization or Codex workspace.
- Record the applicable agreement, retention terms, region, and safeguard behavior.
- Use disposable infrastructure and read-only credentials for the first agent tests.
- Require confirmation for destructive operations, credential movement, uploads, and scope expansion.
- Verify completion from diffs, tests, logs, and external state instead of the model’s summary.
- Measure input, output, cache writes, retries, latency, accepted patches, and human review time.
The July 9 system card supersedes the preview card. It still reports a greater tendency than GPT-5.5 to exceed user intent in agentic coding simulations, while saying absolute rates remain low. This supports stronger controls; it does not prove those failures are routine.
What to Recheck
Re-run the comparison when OpenAI changes plan entitlements, context or rate-limit specifications, pricing, safety evidence, or when independent evaluators publish reproducible results. For cyber work, verify whether normal safeguards or Trusted Access applies to the exact account and task.
Sources
- OpenAI: GPT-5.6 general availability (Archive)
- OpenAI: July 30 price update (Archive)
- OpenAI API docs: pricing (Archive) and Luna model specification (Archive)
- OpenAI: GPT-5.6 System Card
- Artificial Analysis: GPT-5.6 evaluation (Archive) — benchmark scores are current evidence; displayed launch prices are stale after July 30
- Arena: Agent Arena
- BenchLM: GPT-5.6 Luna
- OpenAI: Model-evaluation security incident (Archive)
- OpenAI: Public model catalog (Archive)
Related links
- /posts/openai-gpt-5-6-sol-limited-preview/
- /posts/openai-exploitgym-hugging-face-breach/
- /posts/frontier-model-access-gates-fable-gpt-5-6/
- /posts/gpt-5-6-luna-price-cut/
- /compare/models/premium/
- /models/claude-opus-4-8/
- /models/glm-5.2/
- /models/kimi-k2.7-code/
Last verified: August 1, 2026. Availability, account eligibility, safeguards, pricing, rankings, and model specifications can change independently.