Claude Opus 4.6 vs Grok 4.3

Pricing math on a real workload

For a 10M input / 2M output token job, Claude Opus 4.6 costs $100.00 on OpenKey and Grok 4.3 costs $17.50 — Opus 4.6 is roughly 5.7x more expensive for this exact mix. On raw input price, Opus 4.6 runs $5.15/M against Grok 4.3's $1.2875/M, a 4x ratio (both figures already include OpenKey's flat 3% fee: Anthropic's $5.00/M becomes $5.15/M, xAI's $1.25/M becomes $1.2875/M). Output pricing follows the same pattern: $25.75/M for Opus 4.6 vs $2.575/M for Grok 4.3. If your workload is output-heavy, that gap compounds fast. Cache pricing also favors Grok 4.3 at $0.20/M cache reads versus Opus 4.6's $0.50/M, though Opus 4.6 offers cache writes at $6.25/M and Grok 4.3 doesn't list a cache-write price at all.

Coding and agent benchmarks

This is where the two models separate. On Design Arena's codecategories benchmark, Opus 4.6 ranks 3rd (elo 1342, 63.9% win rate); Grok 4.3 ranks 31st (elo 1243, 49.6%). On fullstack agent tasks, Opus 4.6 ranks 4th (elo 1288, 68.6% win rate) versus Grok 4.3's rank 26 (elo 1072, 31.4%). Webapps: Opus 4.6 rank 4 (elo 1266, 60.9%) against Grok 4.3 rank 14 (elo 1194, 46.6%) — Grok's best relative showing, but still well behind. Artificial Analysis scores confirm the pattern for Grok 4.3 specifically: coding index 42.2, agentic index 24.1, intelligence index 37.6 — no equivalent AA scores are available for Opus 4.6 in this dataset, but the Design Arena gap alone is decisive for anything code-heavy.

Context and reasoning controls

Both models share a 1M-token context window (ratio 1.0 — no advantage either way). Opus 4.6 caps completions at 128,000 tokens; Grok 4.3 doesn't list a max completion figure in this data. Both support a reasoning parameter with adjustable effort: Opus 4.6 offers max/high/medium/low (default medium), Grok 4.3 offers high/medium/low/none (default low, but reasoning is enabled by default). If you need deep multi-step reasoning without manually cranking effort up, Opus 4.6's higher default effort level is the safer starting point. Grok 4.3 also supports logprobs and seed parameters that Opus 4.6 doesn't expose, useful if you need deterministic sampling or token-level probability inspection.

When to pick each

Opus 4.6 is the call for anything where output quality determines whether the code ships: full-stack apps, mobile apps, UI components, game dev — it's top-6 ranked across all of those. Grok 4.3 makes sense when you're running high-volume, lower-stakes generation (bulk content, simple agentic slides, prototyping) where a 5.7x cost difference matters more than a benchmark rank in the 20s or 30s. Both models are available on OpenKey through one API key, billed at provider list price plus a flat 3% fee, so switching between them for A/B testing costs nothing but the token spend.

Questions

Is Claude Opus 4.6 worth the extra cost over Grok 4.3?

For coding and agent work, yes — Opus 4.6 ranks rank 3 on codecategories versus Grok 4.3's rank 31, and the price difference on a 10M-in/2M-out job is $100.00 vs $17.50. If output quality drives revenue or ships to users, the ~5.7x cost gap is small next to the benchmark gap.

How much cheaper is Grok 4.3 per token?

Grok 4.3's OpenKey input price is $1.2875/M versus Opus 4.6's $5.15/M — a 4x ratio. Output pricing is $2.575/M versus $25.75/M. Both prices already include OpenKey's flat 3% fee on top of provider list price.

Do both models support the same context length?

Yes. Both Claude Opus 4.6 and Grok 4.3 list a 1,000,000-token context window — a context ratio of 1.0. The difference is in max output: Opus 4.6 caps completions at 128,000 tokens, while Grok 4.3 doesn't specify a max completion figure here.

Which model is better for agentic web app builds?

Claude Opus 4.6, by a wide margin on this data: rank 4 with a 60.9% win rate on webapps versus Grok 4.3's rank 14 and 46.6% win rate. Grok 4.3's webapps score is actually its strongest agent category, but it still trails Opus 4.6 significantly.