Grok 4.6 vs GPT-5.6
xAI's flagship against OpenAI's frontier family, compared across price, context, coding standing, and access.
Updated August 28, 2026 · Independent comparison — Grok 4.6, GPT-5.6 are separate products.
Grok 4.6
xAI's frontier model for long-running agents
Grok 4.6 is xAI's frontier model, focused on long-running agents and more ambitious interactive and visual work — research, codebase analysis, application development, and polished artifacts. It has a 500K-token context window per xAI, a February 1, 2026 knowledge cutoff, and accepts text, image, and PDF input. xAI's official price (updated August 21, 2026) is a flat $2/$6 per million tokens with no context-based step, and no cache rate is published, though Cursor carries it first-party at $2/$6 with a $0.50 cache-read rate. It is available through the xAI API, the Grok app (SuperGrok / X Premium+ for chat), Cursor, OpenCode, OpenRouter, Vercel, Cloudflare, and Amazon Bedrock.
GPT-5.6
OpenAI's frontier GPT-5.6 family (alias resolves to Sol)
GPT-5.6 is OpenAI's frontier family in three tiers — the flagship Sol for the hardest work, the balanced Terra, and the fast, low-cost Luna — and the alias gpt-5.6 resolves to Sol. All three share roughly a 1.05M-token context window, up to 128K output, and a February 2026 knowledge cutoff. Sol's current API price is a promotional $4/$20 per million tokens (down from a $5/$30 list rate) held through November 21, 2026, with a $0.40 cache-read rate; requests over 272K input tokens are billed at 2x input / 1.5x output for the whole request ($8/$30). Terra is $2/$12 and Luna $1/$6. Inside ChatGPT, Free and Go users reach Terra via Work/Codex while Plus and above unlock Sol and Luna.
Bottom line
xAI's flagship against OpenAI's frontier family, compared across price, context, coding standing, and access. Choose Grok 4.6 if you want frontier-class quality at a flat, aggressive price — $2/$6 with no context step; choose GPT-5.6 if you want one family that scales from flagship Sol to low-cost Luna, matching price to task.
Context & Limits
| Feature | Grok 4.6 | GPT-5.6 |
|---|---|---|
| Context window | 500K | ~1.05M (1,050,000 tokens, all tiers) |
| Max output tokens | Not published | 128K |
| Multimodal input | Text, image, PDF | Text, image |
| Knowledge cutoff | February 2026 | February 2026 |
Pricing (per 1M tokens)
| Feature | Grok 4.6 | GPT-5.6 |
|---|---|---|
| Input | $2.00 (flat, xAI) | Sol $4.00 - Terra $2.00 - Luna $1.00 |
| Output | $6.00 (flat, xAI) | Sol $20.00 - Terra $12.00 - Luna $6.00 |
| Cached input read | Not published (Cursor lists $0.50) | Sol $0.40 - Terra/Luna $0.20 |
| Long-context surcharge | None (flat to 500K) | Sol >272K input: 2x in / 1.5x out ($8/$30) |
Coding & Agentic Standing
| Feature | Grok 4.6 | GPT-5.6 |
|---|---|---|
| Positioning | Frontier performance at an aggressive flat price, for long-running agents | One family from flagship Sol to low-cost Luna, priced to match task to tier |
| Agentic / tool use | Built for long-running agents, codebase analysis, and polished artifacts | Sol is strong at command-line and multi-step coding; adds max/ultra modes |
| Vendor benchmark suites reported | DeepSWE, APEX-Agents, GPQA Diamond, TAU-bench | SWE-bench Pro, Terminal-Bench, TAU-bench (Sol) |
| Directly comparable head-to-head score | No shared vendor-published benchmark | No shared vendor-published benchmark |
Access & Openness
| Feature | Grok 4.6 | GPT-5.6 |
|---|---|---|
| Open weights | ✗ | ✗ |
| Where you can run it | xAI API, Grok app (SuperGrok / X Premium+), Cursor, OpenCode, OpenRouter, Vercel, Cloudflare, Bedrock | ChatGPT (Free/Go = Terra via Work/Codex; Plus+ = Sol/Luna), OpenAI API, Cursor |
| Tool calling / structured outputs | ✓ | ✓ |
| Reasoning modes | Reasoning + function calling | reasoning.effort none-max; Sol adds max/ultra |
Speed & Fit
| Feature | Grok 4.6 | GPT-5.6 |
|---|---|---|
| Pricing model | Flat $2/$6 regardless of prompt size (up to 500K) | Tiered by model (Sol/Terra/Luna) plus Sol's long-context surcharge |
| Best-fit workload | Long-running agents, codebase analysis, and polished artifacts | Anything from the hardest research (Sol) to high-volume cheap work (Luna) |
| Context vs output | 500K context; output ceiling not published | ~1.05M context; 128K published output |
The Verdict
Choose Grok 4.6 if...
- ✓You want frontier-class quality at a flat, aggressive price — $2/$6 with no context step
- ✓Your work is long-running agents, codebase analysis, and polished artifacts
- ✓You need text, image, and PDF input in one model
- ✓You use xAI's API, the Grok app, Cursor, or partners (OpenCode, OpenRouter, Vercel, Cloudflare, Bedrock)
Choose GPT-5.6 if...
- ✓You want one family that scales from flagship Sol to low-cost Luna, matching price to task
- ✓You need a bigger context — ~1.05M tokens vs Grok's 500K
- ✓You want a published max-output ceiling (128K)
- ✓You live in ChatGPT or the OpenAI ecosystem
- ✓Your everyday work fits Terra ($2/$12) or Luna ($1/$6) rather than the flagship rate
Frequently Asked Questions
What is the difference between Grok 4.6 and GPT-5.6?
Grok 4.6 is xAI's frontier model, focused on long-running agents and more ambitious interactive and visual work — research, codebase analysis, application development, and polished artifacts. GPT-5.6 is OpenAI's frontier family in three tiers — the flagship Sol for the hardest work, the balanced Terra, and the fast, low-cost Luna — and the alias gpt-5.6 resolves to Sol.
How much do Grok 4.6 and GPT-5.6 cost?
Grok 4.6: $2.00 (flat, xAI). GPT-5.6: Sol $4.00 - Terra $2.00 - Luna $1.00. See the pricing table above for full plan details.
Should I choose Grok 4.6 or GPT-5.6?
Choose Grok 4.6 if you want frontier-class quality at a flat, aggressive price — $2/$6 with no context step. Choose GPT-5.6 if you want one family that scales from flagship Sol to low-cost Luna, matching price to task.
1DevToolRun either frontier model from one workspace
Grok 4.6 and GPT-5.6 are both closed models reached through an agent or API. 1DevTool runs Claude Code, Codex, and Gemini CLI side by side in persistent terminals and lets you plug in any model over your own keys — so you can drive Grok 4.6 and GPT-5.6 from the same workspace with no lock-in to either lab. It adds a built-in HTTP client, 13-engine database client, and embedded browser, all wired into Send-to-AI. One-time $29, no subscription.