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Grok 4.5 vs GPT-5.6 Sol vs Claude Opus 4.8: Post-Launch Benchmarks (July 2026)

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The Frontier Just Got Cheaper

Grok 4.5 launched July 8, 2026 — SpaceXAI’s first flagship post-rebrand, priced at $2 input / $6 output per MTok. That’s 7.5x cheaper than Claude Opus 4.8 and 5x cheaper than GPT-5.6 Sol on output. And on SpaceXAI’s own benchmarks, Grok 4.5 outperforms Opus 4.8 on three headline coding evals.

Ranked #4 on the Artificial Analysis Intelligence Index at launch, Grok 4.5 is now the price-performance king of the frontier tier.

Head-to-Head Benchmarks

BenchmarkGrok 4.5GPT-5.6 Sol / Sol UltraClaude Opus 4.8Winner
DeepSWE 1.062.0%~59% / ~63%55.75%Grok 4.5
Terminal-Bench 2.183.3%88.8% / 91.9%78.9%Sol Ultra
SWE Marathon (pass@1)29.0%~27%26.0%Grok 4.5
SWE-bench Pro~63%~65% / ~70%~66%Sol Ultra
Humanity’s Last Exam~48%~53%~54%Opus 4.8
MMLU Pro~86%~88%~89%Opus 4.8
ARC-AGI-2~62%~65%~68%Opus 4.8

The pattern: Grok 4.5 wins on coding-throughput benchmarks where it was clearly optimized. Sol Ultra still leads on Terminal-Bench and SWE-bench Pro (the two most-cited agentic-coding evals). Opus 4.8 remains the deep-reasoning specialist.

Pricing Reality Check

ModelInput / MTokOutput / MTokBlended (30K in / 5K out)
Grok 4.5$2.00$6.00$0.09
Gemini 3.1 Pro$2.00$12.00$0.12
GPT-5.6 Sol$5.00$30.00$0.30
GPT-5.6 Sol Ultra$12.50$75.00$0.75
Claude Sonnet 5 (intro)$2.00$10.00$0.11
Claude Opus 4.8$15.00$75.00$0.83

Per 1000 tasks: Grok 4.5 = $90. Opus 4.8 = $830. That’s a 9.2x cost difference. If Grok 4.5 handles 80% of your coding traffic acceptably, the math is decisive.

Add SpaceXAI’s claim that Grok 4.5 uses 4.2x fewer tokens than Opus 4.8 for equivalent tasks, and the effective cost gap widens further.

Where Each Wins

Grok 4.5 wins for:

  • High-volume coding pipelines — $2/$6 pricing is transformative at scale
  • Cursor-native workflows — model was co-trained with Cursor data
  • SWE Marathon / DeepSWE tasks — leads both benchmarks in July 2026
  • 500K context — larger than most competitors at this price
  • Speed — ~80 tok/s serving throughput

GPT-5.6 Sol wins for:

  • Terminal-Bench 2.1 — 91.9% Sol Ultra remains the state of the art
  • Multi-agent orchestration — Ultra mode is native, no wrapper needed
  • Cybersecurity research — Sol is explicitly optimized here
  • ChatGPT / Codex ecosystem — deepest OpenAI tooling integration
  • Long-horizon terminal work — Sol Ultra is uniquely tuned for this

Claude Opus 4.8 wins for:

  • Humanity’s Last Exam — ~54%, still the frontier-knowledge leader
  • Nuanced writing and code review — reads code better than either rival
  • MMLU Pro — ~89%, top on dense-reasoning
  • Extended thinking — best multi-step self-critique
  • Long-form analysis — depth Grok 4.5 doesn’t match

Decision Framework

What's your priority?
│
├── Cheapest capable frontier model
│   → Grok 4.5 ($2/$6)
│
├── Best terminal / agentic coding
│   → GPT-5.6 Sol Ultra (91.9% Terminal-Bench)
│
├── Best deep writing + code review
│   → Claude Opus 4.8
│
├── Cursor IDE workflows
│   → Grok 4.5 (co-trained with Cursor)
│
├── High-volume production coding
│   → Grok 4.5 (cost wins)
│
└── Frontier science / research
    → Opus 4.8 or Sol

What Changed on July 8-9, 2026

  • July 8, 2026: SpaceXAI released Grok 4.5 on V9 foundation
  • July 9, 2026: GPT-5.6 Sol went public GA with Ultra mode
  • July 2026: Grok 4.5 co-trained with Cursor coding traces (SpaceX acquired Cursor for a reported $60B in June 2026)

The Bottom Line

Grok 4.5 didn’t dethrone GPT-5.6 Sol Ultra on Terminal-Bench — Sol Ultra’s 91.9% still stands. But on price-performance, Grok 4.5 is now the default recommendation for any team not locked into a specific ecosystem.

For most 2026 stacks the right shape is:

  • Grok 4.5 for volume coding at $2/$6
  • Sol Ultra reserved for the hardest 5% of agentic tasks
  • Opus 4.8 as the specialist for writing and deep analysis

Sources