Claude Sonnet 5 vs Grok Build 0.1
Claude Sonnet 5 and Grok Build 0.1 both target coding and agentic work, but they're built for different points on the cost/capability curve. Sonnet 5 is Anthropic's flagship Sonnet-class model with a 1M-token context window and selectable reasoning effort up to "max." Grok Build 0.1 is xAI's narrower, faster model tuned specifically for agentic software engineering, with a 256K context window and mandatory reasoning. The gap that matters most: price. Sonnet 5 costs roughly 2x more per input token and 5x more per output token.
Spec vs spec
| Spec | Claude Sonnet 5 | Grok Build 0.1 |
|---|---|---|
| Context window | 1M | 256K |
| Max output | 128K | — |
| Input modalities | text, image, file | text, image |
| Output modalities | text | text |
| Released | Jun 30, 2026 | May 20, 2026 |
| Reasoning | optional | always on |
Pricing
Per 1M tokens. Provider price plus the flat 3% fee — the sum is what you pay.
anthropic/claude-sonnet-5
Input · 1M tokens
$2.00 + 3%$2.06
Output · 1M tokens
$10.00 + 3%$10.30
Cache read · 1M tokens
$0.200 + 3%$0.206
Cache write · 1M tokens
$2.50 + 3%$2.58
FEE — FLAT, EVERY MODEL3%
x-ai/grok-build-0.1
Input · 1M tokens
$1.00 + 3%$1.03
Output · 1M tokens
$2.00 + 3%$2.06
Cache read · 1M tokens
$0.200 + 3%$0.206
FEE — FLAT, EVERY MODEL3%
One workload, priced on both
10M input + 2M output tokens at each model's price, flat 3% fee included.
anthropic/claude-sonnet-5
$41.20
$40.00 provider + 3%
x-ai/grok-build-0.1Cheaper
$14.42
$14.00 provider + 3%
Pricing math on a real workload
Take a workload of 10M input tokens and 2M output tokens — a realistic size for a day of heavy agentic coding sessions. On OpenKey (provider price + 3% flat fee), Claude Sonnet 5 runs $2.06/M input and $10.30/M output (provider: $2.00/$10.00), landing at **$40.00** total for that workload. Grok Build 0.1 runs $1.03/M input and $2.06/M output (provider: $1.00/$2.00), landing at **$14.00** total — a $26 difference on the same workload. That's the input_price_ratio of 2.0 on input tokens compounding with a much bigger completion-price gap. If you're running this workload at scale daily, the difference adds up fast; if you're running it occasionally, it's noise next to the quality difference.
Coding and agentic benchmarks
Claude Sonnet 5 has published artificial_analysis scores: an intelligence index of 53.4, a coding index of 71.5, and an agentic index of 46.7. Grok Build 0.1 has no published benchmark scores in this dataset, so any coding-quality comparison has to come from your own evals, not from a scoreboard. What we do know structurally: Grok Build 0.1's reasoning is mandatory (no way to turn it off), while Sonnet 5's reasoning is optional with five selectable effort levels (low, medium, high, xhigh, max) — giving you a lever to trade latency for depth that Grok Build 0.1 doesn't expose.
Context and modality differences
Sonnet 5 supports a 1,000,000-token context window versus Grok Build 0.1's 256,000 tokens — a context_ratio of 3.91x. That matters for tasks like reviewing an entire monorepo or feeding in long design docs in one shot. Modality is also different: Sonnet 5 accepts text, image, and file inputs; Grok Build 0.1 accepts text and image only, no direct file upload. Sonnet 5 also caps output at 128,000 completion tokens, a limit not specified for Grok Build 0.1 in this data. If your pipeline depends on large file ingestion or very long context, Sonnet 5 is the only one of the two that supports it here.
When to pick each
Pick Grok Build 0.1 for high-throughput coding agents where cost per call matters and your context needs stay under 256K tokens — it's cheaper on both input ($1.03 vs $2.06) and output ($2.06 vs $10.30) and was built specifically for agentic engineering loops. Pick Claude Sonnet 5 when you need the 1M context window, file-input support, or the ability to dial reasoning effort up to "max" for harder problems. Both models are available on OpenKey with a single API key, billed at provider list price plus a flat 3% fee — so switching between them for different stages of a pipeline doesn't mean managing two separate accounts.
Which model for which job
| Use case | Pick | Why |
|---|---|---|
| High-volume automated coding agents | Grok Build 0.1 | $14.00 vs $40.00 on a 10M-in/2M-out workload |
| Large codebase or multi-document review | Claude Sonnet 5 | 1M-token context vs 256K, a 3.91x difference |
| Tasks requiring file uploads | Claude Sonnet 5 | Supports text+image+file input; Grok Build 0.1 only supports text+image |
| Variable-depth reasoning (quick check vs deep analysis) | Claude Sonnet 5 | Five selectable reasoning effort levels (low to max) vs Grok's mandatory-only reasoning |
| Cost-sensitive output-heavy generation | Grok Build 0.1 | $2.06/M output tokens vs $10.30/M, a 5x difference |
Questions
- How much more expensive is Claude Sonnet 5 than Grok Build 0.1?
- On a 10M-input/2M-output workload, Claude Sonnet 5 costs $40.00 on OpenKey versus $14.00 for Grok Build 0.1 — roughly 2.9x more overall, driven by a 2.0x input price ratio and an even larger gap on output tokens ($10.30/M vs $2.06/M).
- Which model has the bigger context window?
- Claude Sonnet 5 supports 1,000,000 tokens of context versus Grok Build 0.1's 256,000 tokens — a context_ratio of 3.91x. That makes Sonnet 5 the better fit for ingesting large codebases or long documents in a single call.
- Does Grok Build 0.1 support file uploads?
- No. Grok Build 0.1's input modalities are text and image only. Claude Sonnet 5 adds file as a third input modality, so it's the one to use if your workflow needs direct file ingestion rather than pasted text.
- Can I turn off reasoning on either model?
- On Claude Sonnet 5, yes — reasoning is optional with five effort levels (low, medium, high, xhigh, max), defaulting to medium. On Grok Build 0.1, reasoning is mandatory, so you don't get a no-reasoning fast path the way you do with Sonnet 5.