Grok 4.3 costs roughly 80% less than Claude Opus 4.8 at the API level and isn't dramatically worse on most tasks. Whether that gap matters depends on what you're doing. For reasoning-heavy work and complex software engineering, Opus 4.8 is still the better model. For general use cases where you're not pushing the model hard, Grok 4.3 makes a strong case for itself at a fraction of the price.

The specs

Grok 4.3 (xAI, released May 6, 2026) - Context window: 1 million tokens - API pricing: $1.25 input / $2.50 output per million tokens - Always-on reasoning (continuous, can't be disabled) - Native video input support - 207 tokens per second output speed - Consumer access: SuperGrok ($30/month)

Claude Opus 4.8 (Anthropic, released May 28, 2026) - Context window: 200K tokens - API pricing: $5.00 input / $25.00 output per million tokens - Top score on Artificial Analysis Intelligence Index: 61.4 - SWE-bench Verified: 88.6% - Consumer access: Claude Pro ($20/month)

The context window difference is significant if you work with very long documents. Grok's 1M token window vs Opus's 200K is a real operational difference for certain workflows.

Benchmark results

On the Artificial Analysis Intelligence Index, Opus 4.8 scores 61.4 — the current top of the leaderboard. Grok 4.3 scores 53, which puts it well above average for models in its price tier.

The gap is wider on specific tasks:

GDPval-AA (knowledge work and reasoning): Grok 4.3 showed more than 300 ELO improvement over its predecessor but still trails Opus 4.8 clearly. Opus's 66.7% pairwise win rate on reasoning tasks is a real edge.

Hallucination rate: Grok 4.3 achieved 78% on Artificial Analysis's Omniscience benchmark — the record for non-hallucination in its class. This is a genuine strength.

Coding: Opus 4.8's 88.6% on SWE-bench Verified is the current high-water mark for multi-file software engineering. Grok 4.3 is competitive but not close on this specific benchmark.

Speed: Grok 4.3 generates output at 207 tokens per second. Opus 4.8 is much slower. For applications where latency matters, Grok wins clearly.

Where Grok 4.3 wins

Grok has real advantages in four areas.

Price: at $1.25/$2.50 per million tokens, Grok is 58% cheaper on input and 90% cheaper on output than Opus 4.8. For high-volume API usage, this gap is large. Running 100 million tokens through Opus 4.8 costs $2,500 in output; through Grok 4.3 it costs $250.

Context window: the 1M token window means you can feed Grok 4.3 entire codebases, large datasets, or book-length documents that would require chunking with Opus 4.8's 200K limit.

Speed: 207 tokens per second is fast. Applications that need real-time response quality — voice interfaces, live coding suggestions — benefit from this.

Hallucination rate: Grok 4.3's 78% on the Omniscience benchmark is a strong result for tasks where factual accuracy matters more than deep reasoning.

Where Opus 4.8 wins

On complex multi-file software engineering, the 88.6% SWE-bench Verified score reflects a real capability difference. Developers consistently reach for Opus 4.8 when dealing with hard multi-file bugs, subtle architectural problems, and tasks that require understanding system-wide interdependencies.

The 300+ ELO gap on GDPval-AA also reflects genuine reasoning differences. For research, legal analysis, and knowledge-intensive work, Opus 4.8 is consistently the stronger model.

Instruction following is another gap. Opus 4.8 handles ambiguous prompts better and makes fewer incorrect assumptions on tasks with multiple constraints.

Which to use

The decision is mostly about use case and volume, not loyalty to either lab.

Use Grok 4.3 for general question-answering, content generation, tasks that benefit from a 1M context window, high-volume API workflows where cost matters, and applications needing fast response.

Use Claude Opus 4.8 for complex software engineering, deep reasoning over long documents, legal and financial analysis, and any task where you've found lighter models giving you wrong or incomplete answers.

A lot of teams land on using both: Grok 4.3 for routine tasks at scale, Opus 4.8 for the hard problems that require more reasoning depth.

On subscription pricing

For most people this debate happens at the consumer level, not the API level. Claude Pro ($20/month) gives you Opus 4.8 access. SuperGrok ($30/month) gives you Grok 4.3 access. The irony: the cheaper API model is more expensive as a consumer subscription.

If you want both — and there are good reasons to have both — you're looking at $50/month for two subscriptions. A credit-based approach covering both models from a single balance often works out cheaper if you're not maxing out either daily.