Grok 4.6 (SpaceXAI, August 12, 2026) and Claude Opus 5 (Anthropic, July 24, 2026) are the two releases that most clearly split the frontier into "intelligence" and "efficiency" camps. Opus 5 is the intelligence king — the new #1 on the Artificial Analysis Intelligence Index and the knowledge-work leader. Grok 4.6 is the efficiency king — near-identical headline scores at a fraction of the cost per task.
This guide compares the two across benchmarks, pricing, speed, latency, and context. Figures are drawn from xAI's launch materials, Anthropic's documentation, Artificial Analysis, and independent evaluations.
At a Glance
| Category | Grok 4.6 | Claude Opus 5 |
|---|---|---|
| Release date | August 12, 2026 | July 24, 2026 |
| Developer | SpaceXAI | Anthropic |
| Model class | Frontier (post-training refresh) | Opus-class flagship |
| Context window | 500,000 tokens | 1,000,000 tokens |
| Max output | — | 128,000 tokens |
| Knowledge cutoff | February 2026 | May 2026 |
| Input price | $2 / 1M | $5 / 1M |
| Output price | $6 / 1M | $25 / 1M |
| Cached input | $0.50 / 1M | $0.50 / 1M |
| Fast variant | 2× price | 2× price, ~2.5× speed |
| Reasoning | Low, medium, high, xhigh | Adaptive thinking (low→max) |
| Model ID | grok-4.6 | claude-opus-5 |
Benchmark Comparison
Opus 5 leads the composite index and the knowledge-work evaluations; Grok 4.6 counters on agentic coding economics and terminal work, where the two are statistically neck-and-neck.
| Evaluation | Grok 4.6 | Claude Opus 5 | Leader |
|---|---|---|---|
| AA Intelligence Index | 61 | 63 | Opus 5 |
| GDPVal-AA v2 (Elo) | 1753 | 1861 | Opus 5 |
| AA-Briefcase (Elo) | 1577 | 1720 | Opus 5 |
| CursorBench v3.2 | 70.8% (xhigh) | 70.0% (max) | Grok 4.6 |
| DeepSWE v1.1 | 65.9% | 68.8% | Opus 5 |
| Terminal-Bench v2.1 | 88.4% | 89.0% | ≈ Tie |
| τ³-Banking | 50.7% | — | Grok 4.6 |
| OSWorld 2.0 | — | 70.6% | Opus 5 |
Sources: Artificial Analysis (Aug 2026 listing), xAI launch table, Anthropic materials, MyClaw re-runs. Vendor/third-party reported; harnesses differ.
Coding Benchmarks Head-to-Head
On the three coding evaluations where both models have comparable published numbers, the gaps are small: Opus 5 leads DeepSWE by 2.9 points, Terminal-Bench v2.1 by 0.6, while Grok 4.6 actually edges CursorBench by 0.8 points. The interesting part is what it costs to get there — see below.
Knowledge-Work Elo
This is Opus 5's undisputed home turf. Its 1861 Elo on GDPVal-AA v2 is the highest score ever recorded on that benchmark (+114 over Fable 5), and its 1720 AA-Briefcase Elo leads Grok by 143 points. If your workload is professional documents, structured analysis, or judgment-heavy knowledge work, this gap is the single most important number in the comparison.
Capability Radar
Radar values are normalized (0–100) from the benchmark table for visual comparison only.
Pricing & Cost Per Task: Grok's Territory
Grok 4.6 is 60% cheaper on input and 76% cheaper on output. But the more meaningful metric is cost per completed task:
| Cost component | Grok 4.6 | Claude Opus 5 |
|---|---|---|
| Input (per 1M) | $2 | $5 |
| Output (per 1M) | $6 | $25 |
| Cost per AA Index task | $0.84 | $2.03 (max) |
| CursorBench cost per task | $2.81 (xhigh, 46 steps) | $8.23 (max, 78 steps) |
Consider a hypothetical agent task using 1M input + 250K output tokens:
At headline rates, that task costs roughly $3.50 on Grok 4.6 vs. $11.25 on Opus 5 — a 3.2× difference. The gap in practice is often larger still: Artificial Analysis measured Grok 4.6 completing AA-Briefcase tasks in ~53 turns and ~0.5B input tokens, versus Opus 5's ~103 turns and ~2.0B input tokens. Opus 5 thinks much longer — which drives its knowledge-work quality, but also its bills.
Speed & Latency
Grok 4.6 is faster on both axes at comparable reasoning effort:
| Metric (Artificial Analysis) | Grok 4.6 (high) | Opus 5 (max / low) |
|---|---|---|
| Output speed | 85.8 t/s | 54.1 t/s |
| Time to first token | 32.3 s | 58.2 s / 2.9 s |
At max effort, Opus 5 takes nearly a minute to start answering. At low effort, though, its TTFT collapses to ~2.9s — one of the widest effort-dependent latency spreads of any frontier model. Grok 4.6 is consistently fast-starting by comparison. For interactive work, Opus 5's adaptive thinking is a real double-edged sword.
Context Window: Opus Doubles Grok
Claude Opus 5 ships a 1,000,000-token context window (128K max output) — double Grok 4.6's 500K — plus a newer knowledge cutoff (May vs. February 2026). For large monorepos, long documents, and multi-hour agent sessions, Opus 5 holds twice the working context.
Verdict: Which Should You Choose?
For many teams, the optimal setup is Grok 4.6 as the default lane with Opus 5 escalated for the hardest, judgment-critical work — especially anything needing 500K+ context or top-tier professional document output. Both models are on the Pareto frontier; they just optimize different axes.