STATUS UPDATE — 8 OCTOBER 2026
This comparison covers a retired model generation. GPT-5.6 Sol, Terra and Luna have been replaced by GPT-6.
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GPT-6 Sol — ChatGPT Plus, Pro, Business and Enterprise since 7 October 2026
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GPT-6 Luna — ChatGPT Free and Go since 8 October 2026. In the API at $0.10 / $0.50 per million tokens
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GPT-6.1 Sol — $2.00 / $10.00 per million tokens
The comparison below is kept for reference on how the 5.6 line behaved. For current pricing see
the October 2026 model pricing table.
QUICK VERDICT — AUGUST 2026
● AA Intelligence Index: Both 61 — tied
● Input price: Grok 4.6 $2/M vs Sol $5/M (Grok 60% cheaper)
● Output price: Grok 4.6 $6/M vs Sol $30/M (Grok 80% cheaper)
● Grok long-context caveat: Doubles to $4/$12/M above 200K tokens
● APEX-Agents: Grok 4.6 leads
● DeepSWE (repo-scale coding): GPT-5.6 Sol leads
● Codex async PR delivery: Sol only — no Grok equivalent
● Context window: Grok 500K vs Sol ~128K
● FLI safety: OpenAI C vs xAI F
Grok 4.6 and GPT-5.6 Sol tie on the Artificial Analysis Intelligence Index (both at 61) — but the nine-benchmark composite averages across task types where each leads differently. Per APIdog's benchmark breakdown, Grok 4.6 leads on APEX-Agents (long-running multi-step tasks) and offers a 500K context window. GPT-5.6 Sol leads on DeepSWE (repository-scale coding) and uniquely offers Codex async PR delivery — assign a task, get a pull request. The AA Index tie at 61 means Grok 4.6 is now at the frontier tier at $2/M input compared to Sol's $5/M — roughly 60% cheaper for equivalent composite benchmark performance.
Grok 4.6 for: Long-running interactive agent tasks (APEX-Agents leader), cost-sensitive pipelines under 200K tokens ($2/M — 60% cheaper than Sol), Cursor and Grok Build workflows (CursorBench 69.9%), 500K context window. Watch: doubles to $4/$12/M above 200K tokens — entire request repriced.
GPT-5.6 Sol for: Repository-scale coding (DeepSWE leader), Codex async PR delivery (unique — no Grok equivalent), OpenAI ecosystem (DALL-E 4, Realtime API), FLI C safety posture for enterprise procurement. At $5/M input, the premium buys Codex and better repo-scale coding.
Last updated August 14, 2026. Related: Grok 4.6 full review → · GPT-5.6 Sol vs Claude Opus 5 →