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GPT-6.1 Terra vs Claude Opus 5.5
Claude Opus 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 Opus 5.5 at 100 (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 Opus 5.5 | Higher |
|---|---|---|---|
| LMArena Elo (community votes) | 1,670.7 | 1,808.7 | Claude Opus 5.5 |
| Vals AI Vals Index accuracy % · weighted finance + coding tasks | 60.2 | 70.2 | Claude Opus 5.5 |
| Artificial Analysis intelligence index · measured runs only | 51 | 58.4 | Claude Opus 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 Opus 5.5 at a glance
- Developer
- Anthropic
- Status
- Live since September 22, 2026
- API price
- $4 input / $20 output per 1M tokens · Anthropic, claude-opus-5-5
- Context window
- 1M tokens
Live — Sep 22 · $4/$20 per MTok, down from Opus 5 at $5/$25 · 1M ctx / 128K out · adaptive thinking always on, default effort medium · cache reads 5% of base input · Anthropic now says start here for most workloads, and Opus 5 is legacy · fast mode (speed: 'fast', up to 2.5x the output tokens per second by Anthropic's figure) at $8 / $40 per MTok, double standard, left research preview Oct 15 with no waitlist, access request or beta header; on the Claude API and on Claude in Microsoft Foundry (Azure-hosted), not on Bedrock, Google Cloud, Claude Platform on AWS, the Batch API or Priority Tier; @ClaudeDevs says Google Cloud is coming soon (Anthropic's fast mode docs, read Oct 16).
Anthropic's token volume on OpenRouter is up 3.6x since Opus 5.5, by OpenRouter's own count
2026-10-25 · Anthropic's models now run about 3.6 times as many tokens a day on OpenRouter as they did before Claude Opus 5.5 launched, according to OpenRouter's own usage data.
Anthropic opens a research preview of Claude Duet, a proactive agent app built around Opus 5.5
2026-10-22 · Anthropic opened a research preview of Claude Duet on October 21, a new app in which Claude works as a proactive agent: it brings you what needs your attention, completes tasks you hand it, keeps working when you step away, and checks with you before it acts on your behalf.
GPT-6.1 Terra vs Claude Opus 5.5: quick answers
Which is better, GPT-6.1 Terra or Claude Opus 5.5?
It depends on what you measure. Claude Opus 5.5 scores higher than GPT-6.1 Terra on all 3 public leaderboards that rate both. Claude Opus 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 Opus 5.5 at 100 (out of 100).
Which is newer, GPT-6.1 Terra or Claude Opus 5.5?
GPT-6.1 Terra. It went live on October 26, 2026, 34 days after Claude Opus 5.5 (September 22, 2026).
Which is cheaper, GPT-6.1 Terra or Claude Opus 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 Opus 5.5 is $4 input / $20 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 Opus 5.5?
GPT-6.1 Terra, at 1.05M tokens against Claude Opus 5.5's 1M, as each vendor lists it.
Who makes GPT-6.1 Terra and Claude Opus 5.5?
GPT-6.1 Terra is from OpenAI; Claude Opus 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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Also: the bench index · API pricing · what a workload costs on each · the wire