GPT-5.6 Sol vs Grok 4.5
GPT-5.6 Sol and Grok 4.5 are the July 2026 flagship routes from OpenAI and xAI for coding agents, tool-heavy workflows, and long-context API work. GPT-5.6 Sol is the primary GPT-5.6 compare anchor with a 1.05M-token context window and OpenAI GA launch rows. Grok 4.5 is available through Grok Build, Cursor, and the SpaceXAI API/console, with tiered pricing at a 200K prompt threshold and an EU launch-day availability caveat from xAI.
Pick GPT-5.6 Sol when you want OpenAI's July 2026 frontier stack, the larger 1.05M context window, and OpenAI-sourced GA rows such as DeepSWE 1.1 at 72.7% and GPQA Diamond at 94.6%. Pick Grok 4.5 when xAI's lower standard-tier API pricing ($2/$6 per 1M tokens for prompts up to 200K) and Grok Build/Cursor distribution matter more, and run your own acceptance tests because several Grok 4.5 chart scores are xAI first-party only. Do not treat Terra or Luna as the OpenAI flagship in this pair.
Decision scorecard
Local evidence first| Signal | GPT-5.6 Sol | Grok 4.5 |
|---|---|---|
| Product type | Standalone API model | Coding-specialized model |
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | custom coding agents, code generation, and tool loops |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1.05m | 500k |
| Cheapest output | $30/1M tokens | $6/1M tokens |
| Provider routes | 2 tracked | 3 tracked |
| Shared benchmarks | 3 shared | SWE-bench Pro leader |
Decision tradeoffs
- GPT-5.6 Sol holds a shared-benchmark lead on Terminal-Bench 2.1, ahead by 5.5 points.
- GPT-5.6 Sol has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Local decision data tags GPT-5.6 Sol for Coding, RAG, and Agents.
- Grok 4.5 holds a shared-benchmark lead on SWE-bench Pro, ahead by 0.1 points.
- Grok 4.5 has the lower cheapest tracked output price at $6/1M tokens.
- Grok 4.5 has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags Grok 4.5 for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
GPT-5.6 Sol
$11,500
Cheapest tracked route/tier: OpenAI API 0-272K input tokens
Grok 4.5
$3,100
Cheapest tracked route/tier: xAI Console <=200K prompt tokens
Estimated monthly gap: $8,400. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Grok 4.5 is $24/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- GPT-5.6 Sol is $24/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-07-09 | 2026-07-08 |
| Context window | 1.05m | 500k |
| Parameters | — | — |
| Architecture | Decoder Only | - |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Weights | Not released | Not released |
| Code | Unknown | Unknown |
| Commercial use | Commercial use: conditional | Commercial use: conditional |
| Knowledge cutoff | - | - |
Pricing and availability
| Pricing attribute | GPT-5.6 Sol | Grok 4.5 |
|---|---|---|
| Input price |
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| Output price |
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Capabilities
| Capability | GPT-5.6 Sol | Grok 4.5 |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | No | No |
| Code execution | Yes | Yes |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | GPT-5.6 Sol | Grok 4.5 |
|---|---|---|
| SWE-bench Pro | 64.6 | 64.7 |
| Terminal-Bench 2.1 | 88.8 | 83.3 |
| DeepSWE 1.1 | 72.7 | 53.0 |
Deep dive
Start with product type and access. GPT-5.6 Sol is OpenAI's GA frontier GPT-5.6 tier across ChatGPT, Codex, and the API, with Terra and Luna as lower-cost siblings that belong in tier guidance rather than this flagship comparison. Grok 4.5 is xAI's July 2026 flagship for coding, agentic work, and Grok Build, but xAI notes EU API-console availability was not live on launch day.
Pricing favors Grok 4.5 on the standard tier. Grok 4.5 lists $2/M input, $0.50/M cached input, and $6/M output for prompts up to 200K tokens, stepping to $4/$1/$12 above 200K. GPT-5.6 Sol lists $5/$30 for requests up to 272K input tokens and $10/$45 above that threshold, with batch and cache discounts on the OpenAI API pricing page.
The cleanest shared coding row in the seed is DeepSWE 1.1: GPT-5.6 Sol at 72.7% versus Grok 4.5 at 53%, both from launch materials but with different evaluators. xAI also reports Terminal Bench 2.1 at 83.3% and SWE Bench Pro at 64.7% for Grok 4.5, while GPT-5.6 Sol has OpenAI GA rows for OSWorld 2.0, BrowseComp, and MMMU Pro without a public Terminal Bench 2.1 row in the seed. Do not merge those rows without naming harnesses.
Context and modality split the pair when prompts are huge. GPT-5.6 Sol's 1.05M-token window is more than double Grok 4.5's tracked 500K context, which matters for repository-scale review and long retrieval packs. Both support vision, tool use, reasoning, and code execution in local model data, so the final choice should combine context fit, provider stack, and your own latency or cost tests.
Source discipline matters for stakeholder-facing claims. Use OpenAI launch and API docs for GPT-5.6 Sol numbers, and xAI launch plus Artificial Analysis or Vals where independently sourced Grok 4.5 rows exist. Treat xAI chart-only Terminal Bench and SWE Bench Pro values as directional until harness documentation or independent leaderboard confirmation arrives.
FAQ
Which model is stronger for coding-agent work?
The seed's cleanest head-to-head is DeepSWE 1.1, where OpenAI reports GPT-5.6 Sol at 72.7% and xAI reports Grok 4.5 at 53%. xAI also publishes higher Terminal Bench 2.1 and SWE Bench Pro chart values for Grok 4.5, but those are first-party chart rows with unspecified harnesses, so run your own coding-agent acceptance tests before production.
How do GPT-5.6 Sol and Grok 4.5 pricing compare?
Grok 4.5 is cheaper on the standard API tier at $2/M input and $6/M output for prompts up to 200K tokens. GPT-5.6 Sol lists $5/M input and $30/M output up to 272K input tokens, with a long-context surcharge above that threshold. Both support prompt caching; compare your real prompt length before assuming Grok stays cheaper.
Which benchmark claims are independently sourced?
GPT-5.6 Sol GA rows come from OpenAI launch and deployment-safety materials. Grok 4.5 has xAI first-party chart values for Terminal Bench 2.1 and SWE Bench Pro plus DeepSWE rows attributed to Datacurve/Artificial Analysis in the seed notes. Prefer independently sourced rows when making cross-vendor claims and label first-party chart values as directional.
Should I compare Grok 4.5 with GPT-5.6 Terra or Luna instead of Sol?
No for flagship intent. Terra and Luna are lower-cost GPT-5.6 tiers useful in family pricing guidance, but GPT-5.6 Sol is the correct OpenAI anchor for a current OpenAI-versus-xAI frontier comparison.
Is Grok 4.5 available everywhere on launch day?
No. xAI's launch materials note Grok 4.5 was not yet available in the EU through xAI products or the API console on launch day, with EU availability expected later in July 2026.
Continue comparing
Last reviewed: 2026-07-09. Data sourced from public model cards and provider documentation.