Grok 4.20 (Reasoning) vs Claude Opus 5.5
Benchmarks, API Token Pricing, Context Window & Speed Comparison
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Grok 4.20 (Reasoning) by xAI and Claude Opus 5.5 by Anthropic represent two of the frontier AI models analyzed in our comprehensive 2026 AI benchmark and LLM comparison. In this head-to-head evaluation, we examine API token pricing, context window specifications, inference speed (tokens per second), and empirical reasoning performance. From a pure economic perspective, Grok 4.20 (Reasoning) holds a notable pricing advantage for token ingestion. On output generation, Grok 4.20 (Reasoning) is more economical per million generated tokens. In data-heavy architectures requiring extensive repository or document analysis, both models provide an identical memory horizon with 1,000K tokens. In latency-sensitive production environments, Grok 4.20 (Reasoning) leads in tokens-per-second throughput, making it ideal for real-time conversational agents and high-concurrency workflows. Below is the complete empirical head-to-head breakdown across cost, speed, context, and capability matrices.
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Grok 4.20 (Reasoning)
Document AnalysisxAI's reasoning model engineered for heavy document analysis, complex logic deduction, and long-horizon agentic tool use.
$3.00 / 1M
$15.00 / 1M
1M tokens
68.2%
Claude Opus 5.5
Frontier Intelligence TitanAnthropic's most intelligent model for complex reasoning, research, and strategic analysis.
$4.00 / 1M
$20.00 / 1M
1M tokens
84.6%
Key Differences at a Glance
- Grok 4.20 (Reasoning) is 1.3x cheaper for API usage (input + output tokens combined).
- Grok 4.20 (Reasoning) is faster at 95 tok/s vs 78 tok/s.
- Claude Opus 5.5 leads on SWE-bench coding (84.6% vs 68.2%).
| Feature | Grok 4.20 (Reasoning) | Claude Opus 5.5 |
|---|---|---|
Intelligence Index Composite reasoning & knowledge score (0-100) | 68 | 94 |
Provider | xAI | Anthropic |
Input Price Cost per million input tokens | $3.00 / 1M | $4.00 / 1M |
Output Price Cost per million output tokens | $15.00 / 1M | $20.00 / 1M |
Blended Price Weighted 7:2:1 cache:input:output per 1M | $2.63 / 1M | $3.08 / 1M |
Context Window Maximum input + output tokens | 1M tokens~1,500 A4 pages of text | 1M tokens~1,500 A4 pages of text |
Max Output Tokens Per single request | 66K | 128K |
Throughput Speed Tokens generated per second | 95 tok/s | 78 tok/s |
SWE-bench Verified Real-world software engineering | 68.2% | 84.6% |
GPQA Diamond Graduate-level reasoning | 72.8% | 82.3% |
Cached Input Price Prompt caching discount per 1M tokens | $0.75 / 1M | $0.40 / 1M |
Who Wins Where?
At-a-glance decision frameworkEmpirical Head-to-Head Benchmark Scores
Official evaluation metrics verified by independent third-party research labs.
Industry benchmark evaluating real-world GitHub issue resolution and multi-file debugging.
Challenging questions created by domain experts to test complex PhD-level reasoning.
Hardened reasoning and academic knowledge benchmark with reduced lucky-guess probability.
Crowdsourced human preference evaluation based on blind, head-to-head model battles.
Extremely difficult, closed-ended questions spanning the frontier of human expert knowledge.
Autonomous multi-step tasks executed inside a real command-line terminal environment.
Research-grade coding problems drawn from real scientific and numerical workloads.
Contamination-free competitive programming problems collected continuously over time.
American Invitational Mathematics Examination — multi-step Olympiad-level reasoning.
Accuracy when reasoning over very large inputs that fill the model context window.
Tokens emitted per second during active generation streaming.
Latency & Response Time
Time to first token (TTFT) and estimated end-to-end response time for a typical 500-token response.
Real-Time Interactive Token Cost Simulator
Adjust sliders to calculate projected monthly cloud API spending with prompt caching discounts.
Grok 4.20 (Reasoning) · Strengths & Key Advantages
- Expansive 1M-token context window tailored for dense repository and legal document intake
- Robust multi-step chain-of-thought reasoning with persistent long-horizon tool execution
- Multimodal ingestion across technical diagrams, multi-page PDFs, and complex charts
- Direct real-time knowledge synthesis from xAI Colossus cluster
Considerations & Trade-offs
- Outperformed by Grok 4.7 and late-2026 frontier leaders on competitive coding benchmarks
- Higher output latency during extended chain-of-thought generation cycles
Claude Opus 5.5 · Strengths & Key Advantages
- Unmatched autonomous multi-step agentic coding and refactoring
- Flawless multi-document reasoning over 1M token context with no long-prompt surcharge
- Highest composite Intelligence Index score measured (94/100), leading SWE-bench Verified at 84.6%
- Precise tool execution with robust error-recovery loops
Considerations & Trade-offs
- Premium output pricing ($20.00/M) plus heavy reasoning-token usage (~68K output tokens per complex task) keeps long agentic runs expensive
- Long thinking times at maximum effort can push a single hard agentic task toward ~$3.85+
Token Use & Task Economics
Estimated cost and token consumption to complete one representative agentic task.
| Metric | Grok 4.20 (Reasoning) | Claude Opus 5.5 |
|---|---|---|
Cost per Task Estimated USD to finish one task | $1.45 | $3.85 |
Output Tokens / Task Tokens generated per task | 45K | 68K |
Reasoning Tokens / Task Thinking tokens burned per task | 28K | 42K |
Technical Specifications
Architecture, release timeline, capabilities, and modalities.
| Feature | Grok 4.20 (Reasoning) | Claude Opus 5.5 |
|---|---|---|
| Official API Model ID (SDK) | grok-4-20-reasoning-latest | claude-opus-5-5-20260901 |
| API Protocol | xAI REST API (OpenAI-Compatible) | Anthropic Messages API + AWS Bedrock + Vertex AI |
| Release Date | 2026-03 | 2026-09 |
| Knowledge Cutoff | November 2025 | June 2026 |
| Architecture | Colossus-Scale Reasoning Sparse MoE | Extended Autonomous Hybrid Reasoning Transformer |
| Parameters | Confidential | Confidential |
| Enterprise Rate Limits (RPM / TPM) | 5,000 – 15,000 RPM (Production Tier) · 4,000,000 – 10,000,000 TPM | 4,000 – 10,000 RPM (Tier 4 + Priority Tier) · 4,000,000 – 10,000,000 TPM |
| Long-Context Tier (>128K/200K) | Flat rate ($3/1M in) across full 1000K window | Standard rate up to 200K tokens; 2x input/output tier above 200K tokens |
| Prompt Cache Policy & TTL | Cached input at $0.75/1M tokens | $0.4/1M cached read (90% off); 5-min default & 1-hour extended TTL |
| Computer Use / GUI Agent | API / CLI Tool-Use & DOM Agent ready (no raw pixel desktop click loop) | Supported (Screen coordinate grounding, browser & desktop GUI action loops) |
| MCP & Parallel Tool Calling | Native MCP Client/Server ready · Parallel function calling · 100% Strict JSON Schema | Native MCP Client/Server ready · Parallel function calling · 100% Strict JSON Schema |
| Web Search Grounding & Sandbox | Real-time Web & X (Twitter) Search Grounding + Code Execution | Native Web Search Citations + Code Execution Tool + MCP Connectors |
| Official Fine-Tuning Support | API Prompt Engineering & RAG Distillation | Custom Model Tuning via Amazon Bedrock & Prompt Distillation |
| Multimodal Token Billing | Text BPE (~4 chars/token) · Vision (~258–765 tokens per image tile) | Text BPE (~4 chars/token) · Vision (~258–765 tokens per image tile) |
| Quantization & Min GPU VRAM | Cloud-Hosted Proprietary (FP8 / BF16 Tensor Core Cluster) · Zero Local VRAM Required (100% Serverless Cloud API) | Cloud-Hosted Proprietary (FP8 / BF16 Tensor Core Cluster) · Zero Local VRAM Required (100% Serverless Cloud API) |
| Safety & Frontier Classification | xAI Production Safety & Alignment Verified | Anthropic RSP ASL-2 / ASL-3 Constitutional Safety Evaluated |
| Enterprise Compliance (ZDR/HIPAA/SOC2) | SOC2 Type II · GDPR · Zero Data Retention (ZDR) & HIPAA BAA Available on Enterprise Tier | SOC2 Type II · GDPR · Zero Data Retention (ZDR) & HIPAA BAA Available on Enterprise Tier |
| Input Modalities | text, vision | text, vision |
| Output Modalities | text | text |
Grok 4.20 (Reasoning) vs Claude Opus 5.5: Quick Answers
Which is more intelligent, Grok 4.20 (Reasoning) or Claude Opus 5.5?
Claude Opus 5.5 is more intelligent. It scores 94 compared with 68 on the composite Intelligence Index.
Which model is faster?
Grok 4.20 (Reasoning) is faster, generating 95 tokens per second compared with 78 tokens per second.
Which model is cheaper to run?
Grok 4.20 (Reasoning) is cheaper at $2.63 per 1M tokens blended, compared with $3.08 (7:2:1 cache:input:output ratio).
Which model has lower latency?
Grok 4.20 (Reasoning) has lower latency, with a time to first token of 0.98s compared with 1.40s.
Verdict
Verdict & Model Selection Recommendation: Choose Grok 4.20 (Reasoning) if your priority is Deep document analysis, multi-stage enterprise research, and extensive tool-driven workflows. Its performance in demanding tasks justifies its operational token cost. Choose Claude Opus 5.5 if your workflow prioritizes Large-scale software development agents, enterprise codebases, and mission-critical scientific synthesis. For large-scale batch processing or customer-facing conversational interfaces, its balance of speed and economics delivers superior ROI.
Frequently asked questions
How does Grok 4.20 (Reasoning) compare to Claude Opus 5.5 in API token pricing and cost per token?+
Grok 4.20 (Reasoning) costs $3.00 per 1M input tokens and $15.00 per 1M output tokens, whereas Claude Opus 5.5 costs $4.00 input and $20.00 output. Overall, Grok 4.20 (Reasoning) is the more cost-effective model for high-volume API pipelines. Both models support prompt caching discounts of up to 90% for repeated prompt prefixes.
Which model has a larger context window: Grok 4.20 (Reasoning) or Claude Opus 5.5?+
Both Grok 4.20 (Reasoning) and Claude Opus 5.5 offer an identical context window of 1,000K tokens (~750k words). Both architectures provide equal capacity for large document ingestion, multi-file codebases, and extended multi-turn conversation histories.
Which AI model is better for software engineering and coding: Grok 4.20 (Reasoning) or Claude Opus 5.5?+
Grok 4.20 (Reasoning) scores 68.2% on SWE-bench Verified while Claude Opus 5.5 scores 84.6%. For autonomous software engineering and multi-file debugging, Claude Opus 5.5 holds the verified benchmark lead.
What is the difference in reasoning capability and extended thinking between Grok 4.20 (Reasoning) and Claude Opus 5.5?+
Grok 4.20 (Reasoning) features native chain-of-thought extended thinking mode with configurable reasoning effort. In contrast, Claude Opus 5.5 provides chain-of-thought reasoning depth for complex math and science.
How does inference speed (tokens per second) compare between Grok 4.20 (Reasoning) and Claude Opus 5.5?+
Grok 4.20 (Reasoning) generates approximately 95 tokens per second, while Claude Opus 5.5 delivers 78 tokens per second. In latency-sensitive production environments, Grok 4.20 (Reasoning) provides faster time-to-first-token (TTFT) and higher streaming response velocity.
Can you implement a tiered LLM routing setup combining Grok 4.20 (Reasoning) and Claude Opus 5.5 to optimize costs?+
Yes! High-efficiency architectures route high-frequency routine classification and conversational tasks to Grok 4.20 (Reasoning) to save operational costs, and dynamically escalate complex architectural queries or reasoning tasks to Claude Opus 5.5. This tiered routing pattern cuts overall API bills by up to 70%.
Understand key metrics like context window, token pricing, reasoning mode, and SWE-bench scores in our comprehensive AI glossary.
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Benchmark scores, token prices, and rate limits evolve rapidly as AI labs release model updates. Always verify current specifications and pricing on the official provider documentation.
Sources: GetInfoUs Independent AI Benchmarks & Official API Specs