Claude Opus 4.8 vs Grok 4.5: which should you choose in 2026?
Claude Opus 4.8 (by Anthropic) and Grok 4.5 (by xAI) are compared below. Here is how they stack up on benchmarks, price, and capabilities, and which one to pick in 2026.
No protocol-matched benchmark supports a controlled winner. Looking only at published point scores, Claude Opus 4.8 is higher on 1 benchmark (LiveBench), while Grok 4.5 is higher on 0 benchmarks.
The evaluation setups are not fully aligned, so these are not controlled head-to-head wins.
At least one model uses context-dependent token-pricing tiers, so the published base rates do not support an unconditional blended price comparison.
Claude Opus 4.8 has the larger context window (1,000,000 tokens vs 500,000 tokens).
Choose Claude Opus 4.8 if…
- • you work with longer documents, transcripts, or codebases
Choose Grok 4.5 if…
- • your own prompt tests favor its output; shared comparable evidence does not identify a unique advantage
The benchmark count includes only results measured with a matching benchmark version and protocol. Arena scores are shown separately. Missing, preliminary, and incompatible data is not treated as a controlled win. Published point-score comparisons are labeled separately when protocol details are incomplete. For text-output models, the verdict also compares token pricing and context windows.
Performance benchmarks
Every value links to its source. A dash means that no reviewed result is available for that exact model and protocol.
| Benchmark | Claude Opus 4.8 | Grok 4.5 |
|---|---|---|
A 657-task benchmark of multi-step work across simulated SaaS applications in six business domains. The Artificial Analysis protocol reports a guardrail-aware score and is distinct from both the public Zapier split and the unrelated dynamic AutoBench framework. Guardrail-aware score Protocols differ or are incompletely disclosed; not counted as a controlled win | 48.5% Artificial Analysis | 51.4% Artificial Analysis |
A benchmark of difficult, verifiable information-seeking questions designed to measure an agent's ability to locate hard-to-find facts through web browsing. Accuracy | — | — |
A verified computer-use benchmark in which multimodal agents operate desktop applications and are graded from the resulting environment state. Mean task reward | — | — |
A long-horizon software-engineering benchmark with 113 original tasks graded by hand-written tests. Pass@1 Protocols differ or are incompletely disclosed; not counted as a controlled win | 59.0%±2.0 DataCurve | 54.0%±2.0 DataCurve |
A human-validated subset of real GitHub issues used to measure whether a coding agent can produce repository patches that resolve the associated tests. Resolved | — | — |
Version 2.1 of the benchmark for completing realistic tasks in terminal environments. Harness, resource limits, and attempt count are part of the protocol. Mean task success Protocols differ or are incompletely disclosed; not counted as a controlled win | 78.9%±1.3 Terminal-Bench | 79.3%±1.5 Terminal-Bench |
A dynamic LLM evaluation framework in which models generate questions, answer them, and participate in reciprocal peer assessment. AutoBench is distinct from Zapier's AutomationBench. Weighted peer-assessment score | — | — |
The highest-quality subset of Graduate-Level Google-Proof Q&A, designed to test expert-level scientific reasoning in biology, physics, and chemistry. Accuracy Protocols differ or are incompletely disclosed; not counted as a controlled win | 92.0% Artificial Analysis | 93.1% Artificial Analysis |
A 2,500-question expert-level benchmark spanning dozens of academic fields. Tool-assisted and no-tools results are separate protocols and must not be merged. Accuracy Protocols differ or are incompletely disclosed; not counted as a controlled win | 48.7% Artificial Analysis | 42.7% Artificial Analysis |
A contamination-resistant benchmark refreshed on a fixed release cadence. Scores from different LiveBench releases must never be compared as the same protocol. Mean of category averages Protocols differ or are incompletely disclosed; not counted as a controlled win | 76.2% LiveBench | 75.8% LiveBench |
| Arena preference scores | ||
Human preference score | 1473 ±4 | 1471 ±5 |
Human preference score for code and web development | 1540 ±7 | 1556 ±8 |
Human preference score for search-grounded responses | 1204 ±6 | 1213 ±7 |
Benchmark sources
- Arena AI leaderboard
- AutomationBench-AA: Agentic SaaS Workflow Benchmark
- DeepSWE 1.1 Leaderboard
- terminal-bench@2.1 Leaderboard
- GPQA Diamond Benchmark Leaderboard
- Humanity's Last Exam Benchmark Leaderboard
- LiveBench 2026-06-25 Leaderboard
Reviewed evidence last updated 2026-08-09. Arena data last refreshed Sep 4, 2026.
Pricing, capabilities, and model facts
| Feature | Claude Opus 4.8 | Grok 4.5 |
|---|---|---|
| Context & model facts | ||
| Developer | Anthropic | xAI |
| API provider | Anthropic | SpaceXAI |
| Input context | 1,000,000 tokens | 500,000 tokens |
| Maximum output | 128,000 tokens | 450,000 tokens |
| Released | — | — |
| Added to Writingmate | May 27, 2026 | Jul 8, 2026 |
| License | Not available | Not available |
| Knowledge cutoff | — | — |
| Capabilities | ||
| Inputs | Text, Image, File | Text, Image, File |
| Outputs | Text | Text |
| Provider endpoint accepts tool parameters | Yes | Yes |
| Reasoning | Yes | Yes |
| Vision | Yes | Yes |
| Image Generation | No | No |
| Video Generation | No | No |
| API pricing | ||
| Base input (per 1M tokens) | $5.00 | $2.00 |
| Base output (per 1M tokens) | $25.00 | $6.00 |
| Higher-context pricing tiers | Base rate only |
|
| Price-comparison caveat | At least one model changes token rates above a prompt-token threshold. Base rates are shown, but an unconditional blended price ratio would not be like-for-like. | |
| API performance | ||
| p95 latency | Not measured | Not measured |
| Output throughput | Not measured | Not measured |
| Writingmate shows API performance only when both models have enough observations from the same measurement window, prompt profile, and provider. Third-party latency values are not copied into this table. | ||
Data sources
- Writingmate model catalog (pricing, limits, and availability)
Catalog data last updated Jul 8, 2026.
Why Pay for Multiple Subscriptions?
Comparing Claude Opus 4.8 from Anthropic with Grok 4.5 from xAI? Instead of managing separate API keys and subscriptions, get both with Writingmate.
| Plan | Price | Claude Opus 4.8 | Grok 4.5 | AI Images | AI Video |
|---|---|---|---|---|---|
Writingmate Pro Most popular | $20/mo | Ultimate required | Included | Nano Banana Pro, FLUX.2, DALL-E & more | Sora 2, VEO 3.1 |
Writingmate Ultimate Power users | $60/mo | Included | Included | Nano Banana Pro, FLUX.2, DALL-E & more | Sora 2, VEO 3.1 |
Claude Opus 4.8 vs Grok 4.5 FAQ
Which is better, Claude Opus 4.8 or Grok 4.5?
No protocol-matched benchmark supports a controlled winner. Looking only at published point scores, Claude Opus 4.8 is higher on 1 benchmark (LiveBench), while Grok 4.5 is higher on 0 benchmarks. The evaluation setups are not fully aligned, so these are not controlled head-to-head wins. At least one model uses context-dependent token-pricing tiers, so the published base rates do not support an unconditional blended price comparison. Claude Opus 4.8 has the larger context window (1,000,000 tokens vs 500,000 tokens).
Which model is cheaper to use through an API?
At least one model uses context-dependent token-pricing tiers, so the published base rates do not support an unconditional blended price comparison.
Which model supports more context?
Claude Opus 4.8 has the larger context window (1,000,000 tokens vs 500,000 tokens).
Can I switch between Claude Opus 4.8 and Grok 4.5?
Yes. Use the model selector on this page to open any current Writingmate model comparison. You can also run the same prompt with both models in Writingmate.
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