GPT-6.1 Terra vs Claude Sonnet 5.5: Benchmarks, Pricing, and Key Differences
Introduction
OpenAI's GPT-6.1 Terra and Anthropic's Claude Sonnet 5.5 are two advanced mid-tier AI models designed for everyday professional tasks, coding, and agentic workflows.
Both models aim to balance performance, speed, and affordability. However, they take different approaches. GPT-6.1 Terra focuses on cost efficiency and lower token consumption, while Claude Sonnet 5.5 delivers stronger performance on demanding coding and computer-use benchmarks.
This article compares their specifications, benchmark results, pricing, speed, and practical use cases to help you choose the right model.
What Is GPT-6.1 Terra?
GPT-6.1 Terra is OpenAI's mid-tier model, positioned between Luna and the more advanced Sol and Astra models.
It replaces GPT-5.6 Terra and offers a reported 50% reduction in pricing compared with its predecessor.
Key features:
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OpenAI reports a factual error rate of 4.3% at maximum effort on its internal difficult-prompt evaluation, compared with 22.3% for GPT-5.6 Terra.
GPT-6.1 Terra is available through ChatGPT, Codex, and the API using the model ID gpt-6.1-terra. It is also rolling out through supported third-party platforms.
What Is Claude Sonnet 5.5?
Claude Sonnet 5.5 is Anthropic's mid-tier model in the Claude 5.5 family. It is designed to deliver strong reasoning and coding performance at a lower cost than Claude Opus 5.5.
Anthropic highlights improvements in software development, debugging, terminal-based agent workflows, presentations, and spreadsheets.
Key features:
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Claude Sonnet 5.5 is available through Claude applications, Claude Code, and the Claude API. It is also supported on Amazon Bedrock, Google Cloud, and Microsoft Azure.
GPT-6.1 Terra vs Claude Sonnet 5.5: Specifications and Pricing
Feature | GPT-6.1 Terra | Claude Sonnet 5.5 |
Developer | OpenAI | Anthropic |
Release date | October 26, 2026 | September 28, 2026 |
Input price per 1M tokens | $1.00 | $2.00 |
Output price per 1M tokens | $5.00 | $10.00 |
Cached input per 1M tokens | $0.05 | $0.10 |
Context window | 1.05M tokens | 1M tokens |
Maximum output | 128K tokens | 128K tokens |
Reasoning levels | None, Low, Medium, High, XHigh, Max | Low, Medium, High, XHigh, Max |
Input support | Text and images | Text and images |
At standard token rates, GPT-6.1 Terra costs approximately half as much as Claude Sonnet 5.5. However, Terra's pricing increases for prompts exceeding 272K tokens, reducing its cost advantage on very long inputs.
Benchmark Comparison
Both companies report strong results across coding, computer use, and reasoning tasks. Independent evaluations also provide useful comparisons.
1. Vendor-Reported Benchmarks
OpenAI's launch comparison evaluates both models across different reasoning effort levels.
Benchmark | Effort | GPT-6.1 Terra | Claude Sonnet 5.5 |
OSWorld 2.1 | Medium | 66.7% | 65.9% |
OSWorld 2.1 | High | 68.7% | 73.3% |
OSWorld 2.1 | Max | 74.2% | 83.9% |
Terminal-Bench 4.0 | Medium | 35.8% | 28.8% |
Terminal-Bench 4.0 | High | 41.8% | 43.0% |
Terminal-Bench 4.0 | Max | 50.3% | 70.6% |
At medium effort, GPT-6.1 Terra matches or outperforms Sonnet 5.5 on these two benchmarks. However, Sonnet gains a significant advantage at higher reasoning levels, particularly on computer-use and terminal-based coding tasks.
2. Independent Benchmark Results
Artificial Analysis evaluates both models using a shared testing methodology.
Benchmark | GPT-6.1 Terra | Claude Sonnet 5.5 |
Artificial Analysis Intelligence Index | 48 | 56 |
GDPval-AA (Knowledge Work, Elo) | 1476 | 1838 |
Terminal-Bench 4.0 | 56% | 64% |
Humanity's Last Exam | 46% | 55% |
SciCode | 55% | 61% |
AA-LCR (Long-Context Reasoning) | 83% | 83% |
Claude Sonnet 5.5 leads in most of these evaluations, particularly in professional knowledge work and coding. Both models achieve the same reported score on long-context reasoning.
Reasoning effort also influences performance. At low and medium effort, the Intelligence Index scores are equal. Sonnet 5.5 begins to pull ahead at higher effort levels.
Cost Per Task and Token Efficiency
GPT-6.1 Terra's biggest advantage is its lower cost per task.
According to Artificial Analysis, Claude Sonnet 5.5 uses approximately 197,000 tokens per task at maximum effort, compared with around 35,000 tokens for Terra.
This difference, combined with Terra's lower token prices, creates a significant cost advantage.
Cost Comparison Across Reasoning Levels
Effort | Terra Index Score | Terra Cost | Sonnet 5.5 Index Score | Sonnet Cost |
Low | 36 | $0.05 | 36 | $0.35 |
Medium | 41 | $0.10 | 41 | $0.48 |
High | 44 | $0.13 | 47 | $0.88 |
Max | 48 | $0.40 | 56 | $5.46 |
At medium effort, both models achieve the same reported index score, but Terra costs approximately one-fifth as much.
At maximum effort, Sonnet 5.5 achieves a higher score, although its cost per task is more than 13 times higher.
This makes Terra particularly attractive for high-volume applications where controlling operating expenses is important.
GPT-6.1 Terra vs Claude Sonnet 5.5: Speed
Speed depends on whether you measure token generation or the time required to complete an entire task.
Speed Metric | GPT-6.1 Terra | Claude Sonnet 5.5 |
Output speed | 91 tokens/second | 141 tokens/second |
Average task completion time | 384 seconds | 878 seconds |
Claude Sonnet 5.5 generates tokens faster, making it feel more responsive when producing long answers.
However, GPT-6.1 Terra completes the evaluated tasks faster because it uses significantly fewer tokens.
The distinction is important: Sonnet is faster at generating individual tokens, while Terra can be more efficient at completing entire agentic workflows.
Which Should You Choose?
The best model depends on your workload, performance requirements, and budget.
Choose GPT-6.1 Terra if:
Cost efficiency matters: You run high-volume workloads and want to reduce API expenses.
Your tasks are straightforward: You mainly handle emails, summaries, documents, and everyday knowledge work.
You prefer medium reasoning: Terra delivers competitive benchmark performance at a much lower cost.
You need visual reasoning: It supports image understanding, charts, and computer-use workflows.
You use OpenAI products: You already work with ChatGPT, Codex, or supported integrations.
Choose Claude Sonnet 5.5 if:
You handle complex coding tasks: It performs strongly on terminal-based coding and debugging benchmarks.
You need advanced computer use: It leads at higher effort levels on OSWorld 2.1.
You create professional deliverables: Its reported GDPval-AA performance makes it a strong option for business-oriented work.
You need higher reasoning performance: It offers stronger results on several demanding evaluations.
You use Anthropic products: You already work with Claude, Claude Code, or its cloud integrations.
Conclusion
GPT-6.1 Terra and Claude Sonnet 5.5 offer different advantages. Terra focuses on affordability, token efficiency, and faster task completion, while Sonnet 5.5 delivers stronger performance on demanding coding, computer-use, and professional knowledge-work benchmarks.
For businesses running large volumes of everyday AI tasks, Terra offers an attractive cost advantage. For complex engineering and higher-effort reasoning, Sonnet 5.5 may justify its higher price.
The right choice ultimately depends on the balance between performance, cost, and the complexity of your workload.
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