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GPT-6.1 Terra vs Claude Sonnet 5.5
Claude Sonnet 5.5 scores higher than GPT-6.1 Terra on all 3 public leaderboards that rate both. On the ArtificialWatch Index, which takes the median of each model's percentile across the boards that score it, GPT-6.1 Terra is at 75 and Claude Sonnet 5.5 at 89.8 (out of 100).
Scores as published by each board; table composed October 28, 2026.
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Leaderboard by leaderboard
| Board | GPT-6.1 Terra | Claude Sonnet 5.5 | Higher |
|---|---|---|---|
| LMArena Elo (community votes) | 1,670.7 | 1,769.3 | Claude Sonnet 5.5 |
| Vals AI Vals Index accuracy % · weighted finance + coding tasks | 60.2 | 70.9 | Claude Sonnet 5.5 |
| Artificial Analysis intelligence index · measured runs only | 51 | 54.2 | Claude Sonnet 5.5 |
Raw scores are each board's own scale, so compare within a row, not across rows. Full table: the bench index.
GPT-6.1 Terra at a glance
- Developer
- OpenAI
- Status
- Live since October 26, 2026
- API price
- $1 input / $5 output per 1M tokens · OpenAI, gpt-6.1-terra
- Context window
- 1.05M tokens
Live — Oct 26 · $1 / $5 per MTok, cached input $0.05, cache writes $1.25 (OpenAI's model page) · 1.05M ctx / 128K out · knowledge cutoff Jun 1, 2026 · reasoning, text and image in · GPT-5.6 Terra lists at $2 / $12 on OpenRouter · first seen Oct 16-19 as the judge model in Microsoft's dotnet/efcore eval configs (PR #39217) · our sweep caught gpt-6.1-terra at 17:52 UTC and fired at 17:53 · OpenRouter added openai/gpt-6.1-terra (18:13 UTC) and openai/gpt-6.1-terra-pro (18:15) the same evening, both at $1 / $5 and 1.05M ctx · scored on LMArena, Vals and Artificial Analysis by Oct 28.
GPT-6.1 Terra is live in OpenAI's API at $1 / $5 per million tokens, under GPT-5.6 Terra's $2 / $12
2026-10-26 · OpenAI's GPT-6.1 Terra is live in its API. Our radar saw the gpt-6.1-terra id at 17:52 UTC on October 26 and fired the alert at 17:53, before OpenRouter listed it.
GPT-6.1 Terra turns up again, as a cheaper reviewer in a GitHub engineer's Copilot workflow
2026-10-25 · A second public repo now calls GPT-6.1 Terra, a model OpenAI has not announced. On October 24 at 03:48 UTC, Nate Finch, whose GitHub profile lists his company as GitHub, merged a pull request in his own public repo, natefinch/council4, that moves every review step from gpt-6.1-sol to gpt-6.1-terra at high effort.
Claude Sonnet 5.5 at a glance
- Developer
- Anthropic
- Status
- Live since September 28, 2026
- API price
- $2 input / $10 output per 1M tokens · Anthropic, claude-sonnet-5-5
- Context window
- 1M tokens
Live — Sep 28 · $2/$10 per MTok, the same as Sonnet 5 · cache reads $0.20 at launch, halved to $0.10 on Oct 7, writes $2.50 · in the API, the Claude apps, AWS, Google Cloud and Azure the same day · 1M ctx / 128K out · knowledge cutoff Jun 2026 · Artificial Analysis Intelligence Index 56 at max effort, #3 of 216 reasoning models (read Sep 28) · Anthropic's own table: Terminal-Bench 4.0 70.6% (Opus 5.5 66.4%), OSWorld 2.1 80.1% (Opus 5.5 81.8%) · our sweep caught claude-sonnet-5-5 at 17:54 UTC and fired at 17:55.
Claude Sonnet 5.5 ships at Sonnet 5's price, and the first independent number puts it #3 among reasoning models
2026-09-28 · Claude Sonnet 5.5 is live. Our sweep read the id claude-sonnet-5-5 at 17:54:45 UTC on September 28 and the alert went out at 17:55:45, 60 seconds later, to 314 inboxes and one phone. OpenRouter listed it nine minutes after that.
Claude Sonnet 5.5: named by Anthropic, reportedly in partner testing, priced 89% by Sep 30
2026-09-27 · Anthropic has named Claude Sonnet 5.5 but has not dated it. Everything past the name is reported, not confirmed - and the one number that moves every day says it is close.
GPT-6.1 Terra vs Claude Sonnet 5.5: quick answers
Which is better, GPT-6.1 Terra or Claude Sonnet 5.5?
It depends on what you measure. Claude Sonnet 5.5 scores higher than GPT-6.1 Terra on all 3 public leaderboards that rate both. Claude Sonnet 5.5's widest lead is on Vals AI. On the ArtificialWatch Index, which takes the median of each model's percentile across the boards that score it, GPT-6.1 Terra is at 75 and Claude Sonnet 5.5 at 89.8 (out of 100).
Which is newer, GPT-6.1 Terra or Claude Sonnet 5.5?
GPT-6.1 Terra. It went live on October 26, 2026, 28 days after Claude Sonnet 5.5 (September 28, 2026).
Which is cheaper, GPT-6.1 Terra or Claude Sonnet 5.5?
GPT-6.1 Terra is cheaper on both input and output. On each vendor's own API, GPT-6.1 Terra is $1 input / $5 output per million tokens and Claude Sonnet 5.5 is $2 input / $10 output per million tokens. GPT-6.1 Terra's rate rises for prompts over 272K tokens. Prices as published in the models.dev catalog, as of 2026-10-27.
Which has the bigger context window, GPT-6.1 Terra or Claude Sonnet 5.5?
GPT-6.1 Terra, at 1.05M tokens against Claude Sonnet 5.5's 1M, as each vendor lists it.
Who makes GPT-6.1 Terra and Claude Sonnet 5.5?
GPT-6.1 Terra is from OpenAI; Claude Sonnet 5.5 is from Anthropic.
Where do these numbers come from?
Each score is the leaderboard's own published figure, read by ArtificialWatch (table composed October 28, 2026). Boards measure different things, so raw scores are only comparable within a row.
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