High-volume, cost-sensitive work
Choose Claude Sonnet 5.5
Claude Sonnet 5.5 costs 11% less on a typical mix of three input tokens for every output token ($4.00 against $4.50 per million tokens).
Claude Sonnet 5.5 vs GPT-5.6 Terra: price, context and capabilities
Choose Claude Sonnet 5.5 for high-volume, cost-sensitive work, writing and code generation, reused prompts and documents (RAG, agents), the hardest reasoning tasks, the latest release and the most recent knowledge; on the other points the two are level or the data is missing.
In short
- Claude Sonnet 5.5 is 11% cheaper than GPT-5.6 Terra at the headline price ($4.00 / 1M tokens vs $4.50 / 1M tokens).
- GPT-5.6 Terra reads more per request: 1.05M tokens against 1M.
- Claude Sonnet 5.5 is the newer model (September 2026, against Jul 9, 2026).
Which should you choose?
Each answer below comes straight from the published prices, specifications and independent benchmark results.
Writing and code generation
Choose Claude Sonnet 5.5
Claude Sonnet 5.5 charges $10.00 per million output tokens, against $12.00 for GPT-5.6 Terra. Output dominates the bill when answers are long.
Reused prompts and documents (RAG, agents)
Choose Claude Sonnet 5.5
Claude Sonnet 5.5 charges $0.10 per million cached input tokens, against $0.20 for GPT-5.6 Terra.
Hardest reasoning tasks
Choose Claude Sonnet 5.5
Claude Sonnet 5.5 scores 56 on the Artificial Analysis Intelligence Index, against 42.1 for GPT-5.6 Terra.
Reasoning over long documents
Either one
They are practically level on Long-context reasoning (AA-LCR) (82.7% and 83%).
Latest release
Choose Claude Sonnet 5.5
Claude Sonnet 5.5 is the newer release (September 2026, against Jul 9, 2026 for GPT-5.6 Terra).
Most recent knowledge
Choose Claude Sonnet 5.5
Claude Sonnet 5.5 was trained on data up to June 2026, against February 2026 for GPT-5.6 Terra.
Monthly cost at three volumes
| Volume | Claude Sonnet 5.5 | GPT-5.6 Terra | Difference |
|---|---|---|---|
| Prototype: 1M input, 250K output tokens | $4.50 | $5.00 | Claude Sonnet 5.5, $0.50 less |
| Production: 20M input, 5M output tokens | $90.00 | $100.00 | Claude Sonnet 5.5, $10.00 less |
| Scale: 500M input, 100M output tokens | $2,000 | $2,200 | Claude Sonnet 5.5, $200.00 less |
Standard rates, without caching or batch discounts. Volumes are per month.
Specifications side by side
| Claude Sonnet 5.5 | GPT-5.6 Terra | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Category | Language models | Language models |
| Status | Generally available | Generally available |
| Headline price | $4.00 / 1M tokens | $4.50 / 1M tokens |
| Input | $2.00 / 1M tokens | $2.00 / 1M tokens |
| Output | $10.00 / 1M tokens | $12.00 / 1M tokens |
| Cached input | $0.10 / 1M tokens | $0.20 / 1M tokens |
| Context window | 1M | 1.05M |
| Max output | 128k | 128k |
| Released | September 2026 | Jul 9, 2026 |
| Knowledge cutoff | June 2026 | February 2026 |
| Licence | Proprietary | Proprietary |
| Capabilities | Vision, Reasoning, Tool calling, Structured output, Prompt caching, Batch API | Vision, Reasoning, Tool calling, Structured output, Prompt caching, Batch API |
| API model id | claude-sonnet-5-5 | gpt-5.6-terra |
Benchmarks side by side
Leader in bold.
| Benchmark | Claude Sonnet 5.5 | GPT-5.6 Terra |
|---|---|---|
| Intelligence Index | 56 | 42.1 |
| SciCode | 61% | 55% |
| Humanity's Last Exam | 55% | 42.9% |
| Long-context reasoning (AA-LCR) | 82.7% | 83% |
| Terminal-Bench Hard | No data | 57.6% |
| GPQA Diamond | No data | 92.5% |
| IFBench (instruction following) | No data | 71.2% |
| τ²-Bench (agentic tool use) | No data | 86.3% |
| MMMU-Pro (visual reasoning) | No data | 80.7% |
Independent evaluations by Artificial Analysis, run the same way for every model, at the reasoning setting shown. Percentages unless marked as an index.
Frequently asked questions
Should I choose Claude Sonnet 5.5 or GPT-5.6 Terra?
Choose Claude Sonnet 5.5 for high-volume, cost-sensitive work, writing and code generation, reused prompts and documents (RAG, agents), the hardest reasoning tasks, the latest release and the most recent knowledge; on the other points the two are level or the data is missing.
Which is cheaper, Claude Sonnet 5.5 or GPT-5.6 Terra?
Claude Sonnet 5.5 is 11% cheaper than GPT-5.6 Terra at the headline price ($4.00 / 1M tokens vs $4.50 / 1M tokens).
Which has the larger context window, Claude Sonnet 5.5 or GPT-5.6 Terra?
GPT-5.6 Terra reads more per request: 1.05M tokens against 1M.
What is the difference between Claude Sonnet 5.5 and GPT-5.6 Terra?
Claude Sonnet 5.5 is made by Anthropic and GPT-5.6 Terra by OpenAI. Claude Sonnet 5.5 is 11% cheaper than GPT-5.6 Terra at the headline price ($4.00 / 1M tokens vs $4.50 / 1M tokens). GPT-5.6 Terra reads more per request: 1.05M tokens against 1M. Claude Sonnet 5.5 is the newer model (September 2026, against Jul 9, 2026).
How much do Claude Sonnet 5.5 and GPT-5.6 Terra cost per month?
At 20 million input and 5 million output tokens a month, Claude Sonnet 5.5 costs $90.00 and GPT-5.6 Terra costs $100.00, at standard rates.
Which is newer, Claude Sonnet 5.5 or GPT-5.6 Terra?
Claude Sonnet 5.5 was released on September 2026 and GPT-5.6 Terra on Jul 9, 2026.