Head-to-head
Grok 4.3 vs Claude Sonnet 5: which AI model wins in 2026?
Grok 4.3 ($2.50/1M out) and Claude Sonnet 5 ($15/1M out ($10 intro until 2026-08-31)) are two of the most-used AI models in 2026. Across 3 community votes, Claude Sonnet 5 leads with 57% approval.
Quick verdict
On Reasoning, pick Claude Sonnet 5: the arena rates it 4.5/5 against 4/5 for Grok 4.3. On budget, Grok 4.3 wins: it starts at $2.50/1M out versus $15/1M out ($10 intro until 2026-08-31) for Claude Sonnet 5.
Line-by-line comparison
Strengths and weaknesses
Grok 4.3
- Aggressive pricing: $1.25/$2.50 per 1M tokens, 58% cheaper input and 83% cheaper output than Grok 4, undercutting GPT-5.5 and Gemini 3.1 Pro
- Major agentic leap: +321 Elo on GDPval-AA versus Grok 4.20, with strong tool calling and instruction following
- Cached input at $0.20/1M (84% discount), a big saver for repeated agent loops
- Configurable reasoning effort (none/low/medium/high) in one model at one price, no routing between fast and deep variants
- Praised on HN for natural, concise tone and token-dense outputs that lower real-world costs
- Solid throughput around 130 output tokens/sec (Artificial Analysis)
- Coding reasoning judged 'not competitive with the big April releases' by HN developers; intelligence frontier barely moved since Grok 4
- Non-hallucination score dropped 8 points vs Grok 4.20 on AA-Omniscience; 4.20 remains xAI's safer pick for precision-critical domains
- High time to first token (~13s at high reasoning effort per Artificial Analysis), painful for interactive apps
- Context window shrank to 1M from Grok 4.20's 2M
- Recurring trust and safety complaints (harmful content reports, inconsistent behavior) and no MCP/connected-apps support in the consumer app
Claude Sonnet 5
- Large agentic gains over Sonnet 4.6: Terminal-Bench 2.1 80.4% vs 67.0%, OSWorld-Verified 81.2% vs 78.5%, SWE-bench Pro 63.2% vs 58.1%
- Matches Opus 4.8 on knowledge work (GDPval-AA v2: 1,618 vs 1,615) and nearly ties it on Humanity's Last Exam with tools (57.4% vs 57.9%) at 60% of Opus 4.8 pricing (40% during the intro window)
- 1M token context window and 128K max output; introductory pricing of $2/$10 per 1M tokens through Aug 31, 2026
- Persistent self-verifying agent behavior: hands-on reviews note it tests its own code and iterates on hard problems until solved, unlike Sonnet 4.6
- First Sonnet with xhigh effort level and high-resolution vision (2576px images); adaptive thinking enabled by default
- Higher code-review precision than Sonnet 4.6 (38-40% vs 29%), producing fewer false-positive findings
- New tokenizer inflates token counts roughly 30% for the same text (1.0-1.35x per Anthropic; ~1.4x English, ~1.28x Python measured by Simon Willison), raising effective cost despite the unchanged sticker price
- Verbose and token-hungry: ~$2.29 per task vs ~$1.20 for Sonnet 4.6 in independent tests (ranked 101st of 161 for cost efficiency); at high effort cost-per-task can exceed Opus 4.8
- Measurably slower than Sonnet 4.6 on small routine edits and prone to over-engineering simple tasks (CodeRabbit hands-on review)
- Sampling parameters (temperature, top_p, top_k) removed; non-default values return a 400 error, breaking existing pipelines
- Launch sentiment on HN/Reddit was mixed: the '5' label was seen as overpromising, and stricter cybersecurity safeguards can refuse benign security-adjacent work
Cast your verdict
One recommendation per tool per gladiator. It reshapes the crowd score everyone sees.
The arena’s verdict on Grok 4.3
Pick Grok 4.3 if you run agentic or high-volume pipelines where cost per call dominates: it delivers near-frontier reasoning and a big tool-calling jump over Grok 4.20 at a fraction of GPT-5.5 or Gemini 3.1 Pro pricing. Skip it if coding precision is your priority, as developers still rank Claude and the big April releases ahead. Also stay on Grok 4.20 if you need its 2M context or its better non-hallucination score for legal, medical, or compliance work. Latency-sensitive apps should test the ~13s time to first token before committing.
The arena’s verdict on Claude Sonnet 5
Choose Sonnet 5 if you run coding, terminal or computer-use agents and want near Opus 4.8 quality at Sonnet prices, especially during the $2/$10 intro window; it is a strict upgrade over Sonnet 4.6 at low and medium effort. Budget for the new tokenizer and its verbosity: real per-task costs run well above Sonnet 4.6, and at the highest effort levels Opus 4.8 can be the better deal per solved task. Avoid it for latency-sensitive small edits or pipelines that rely on temperature and top_p, which now error. Sonnet 4.6 remains the pragmatic pick for high-volume tiny-diff workloads.
What the crowd says
On Grok 4.3
No verdicts yet. Be the first to speak.
On Claude Sonnet 5
“Cheap per token, pricey per task. Independent tests had it near $2.29 a task vs $1.20 on 4.6, and at high effort it can out-cost Opus 4.8. It will not stop talking.”
“Terminal-Bench going 67 to 80 over Sonnet 4.6 matches what I see. My CI-fix agent went from constant babysitting to mostly hands-off overnight.”
“Matches Opus 4.8 on knowledge work at 60% of the price, and the intro $2/$10 window makes it silly value. My research agent runs on Sonnet 5 now, zero regrets.”
Keep comparing
Frequently asked questions
Is Grok 4.3 better than Claude Sonnet 5?
The crowd currently sides with Claude Sonnet 5: 57% recommend it, versus 50% for Grok 4.3 (3 votes). On Reasoning, Claude Sonnet 5 rates higher (4.5/5 vs 4/5). The right pick depends on your use case. The line-by-line comparison on this page breaks down pricing, key specs and arena ratings.
Which is cheaper, Grok 4.3 or Claude Sonnet 5?
Grok 4.3 is cheaper: it starts at $2.50/1M out, while Claude Sonnet 5 starts at $15/1M out ($10 intro until 2026-08-31).
How much do Grok 4.3 and Claude Sonnet 5 cost per 1M tokens?
Grok 4.3: $1.25/1M in per 1M input tokens, $2.50/1M out per 1M output tokens. Claude Sonnet 5: $3/1M in ($2 intro until 2026-08-31) per 1M input tokens, $15/1M out ($10 intro until 2026-08-31) per 1M output tokens.