Model Comparison
GPT-5.6 Terra vs Claude Sonnet 5
GPT-5.6 Terra (ultra) leads Claude Sonnet 5 (max effort) by 215 Elo, and their 95% ranges sit 131 Elo apart. Even GPT-5.6 Terra's lowest-rated configuration, GPT-5.6 Terra (medium), ranks above Claude Sonnet 5 (max effort). Among 78 models, each ranked by its best configuration, GPT-5.6 Terra is #13 and Claude Sonnet 5 is #23. Cost per script: $0.275 for GPT-5.6 Terra (ultra) and $0.696 for Claude Sonnet 5 (max effort).
Last updated , from board data generated at 01:13 UTC.
Picks and Verdict
PickGPT-5.6 Terra
GPT-5.6 Terra (medium)
Pick GPT-5.6 Terra (medium) for a quick draft at $0.062, since it sits 139 Elo above Claude Sonnet 5 (max effort), which costs more than eleven times as much.
PickClaude Sonnet 5
Claude Sonnet 5 (max effort)
Pick Claude Sonnet 5 (max effort) when hitting the exact length matters most, since its 96.6 on Length Adherence is the best of the four settings.
The cheapest setting on this page has a higher Elo than the most expensive one. GPT-5.6 Terra (medium) costs $0.062 a script and sits 139 Elo above Claude Sonnet 5 (max effort), a twelve-minute run at $0.696. Their 95% ranges don't overlap, which is strong evidence for that order, and Sonnet costs eleven times as much. Terra's top setting clears Sonnet by more. Ranked by best setting, GPT-5.6 Terra is the #13 model of 78 and Claude Sonnet 5 the #23 model, and GPT-5.6 Terra (ultra) is 215 Elo ahead of Sonnet's best. Ultra isn't worth it for me, though: 76 Elo above medium, with overlapping ranges, at more than four times the cost and almost six times the wait. It does bring more substance and better length. In fairness to Claude Sonnet 5, max effort holds the requested length best of the four settings and is slightly ahead on continuity. Its hook is six points behind either Terra setting. So I'd run Terra at medium and keep ultra for scripts where the facts are the point.
Disclosure: GPT-5.6 Terra and Claude Sonnet 5 each come from the same lab as one of the judges (GPT-6.1 Sol and Claude Opus 5.5). Neither is scored by its own lab alone (how the panel works). The judge analysis measures how much each judge favors its own lab.
How to Read the Writing Score, Writing Elo and 95% Ranges
Writing Score and Writing Elo. The Writing Score (0 to 100) is the weighted average of the nine metric scores: seven from the judges, Length Adherence from code and the Slop Score half from each. The Writing Elo is a rating from pairwise comparisons: on each script, each configuration's average across its drafts is compared with every other configuration's, and gaps within the draft-to-draft variation count as draws. Elo rewards winning often, so the two can put configurations in a different order.
Elo ranges. Each 95% range shows how far a configuration's Elo could move if the drafts had come out slightly differently. It comes from resampling every configuration's recorded draft scores on each reference script and ranking again. Comparing two separate ranges does not test the Elo gap between them: ranges far apart are strong evidence for the order, and overlapping ranges do not mean a tie. The reference scripts stay fixed, so the ranges say nothing about new scripts. The methodology page has the full description.
All Thinking Levels of Both Models
Every ranked configuration of GPT-5.6 Terra and Claude Sonnet 5, scored on the same 10 scripts by the same four judges.
- Each row is one configuration: the model at one thinking level. The dot is its Writing Elo, a rating from pairwise comparisons of the scores on each script, and the bar is its 95% range: how far that Elo could move if the drafts had come out slightly differently.
- When two bars overlap, the board cannot order those two configurations. Bars far apart are strong evidence for the order.
- The table under the chart lists the same configurations in the same order and adds the Writing Score (the 0 to 100 consensus of the judges and code), cost, time and configuration rank (the place among all configurations on the board).
Shaded rows are the configurations chosen for the metric comparison below.
| Configuration | Writing Elo | 95% Range | Writing Score | Cost / Script | Time / Script | Configuration Rank |
|---|---|---|---|---|---|---|
| GPT-5.6 Terra (ultra) | 2074 | 2035 to 2113 | 81.4 | $0.275 | 8.0 min | #25 |
| GPT-5.6 Terra (medium) | 1998 | 1952 to 2041 | 80.7 | $0.062 | 1.4 min | #33 |
| Claude Sonnet 5 (max effort) | 1859 | 1812 to 1904 | 79.2 | $0.696 | 12.0 min | #45 |
| Claude Sonnet 5 (high) | 1652 | 1602 to 1703 | 76.6 | $0.121 | 1.9 min | #58 |
Cost is one script at the API list price of the route used, uncached and without judging. Time is the average for one accepted script, retries included.
Computed Findings Across Thinking Levels
Each finding is computed from the configurations above. Where two 95% ranges overlap, the board cannot order those two configurations.
- Best Configurations Head to Head. GPT-5.6 Terra (ultra) leads Claude Sonnet 5 (max effort) by 215 Elo, and their 95% ranges do not overlap (2035 to 2113 against 1812 to 1904), which is strong evidence for that order.
- Every GPT-5.6 Terra Configuration Ranks Higher. Both GPT-5.6 Terra configurations rank above both Claude Sonnet 5 configurations: the lowest-rated, GPT-5.6 Terra (medium) at Elo 1998, still beats Claude Sonnet 5 (max effort) at Elo 1859. Their 95% ranges do not overlap.
- Lowest Thinking Levels Head to Head. At their lowest thinking levels, GPT-5.6 Terra (medium) at Elo 1998 and $0.062 per script leads Claude Sonnet 5 (high) at Elo 1652 and $0.121 per script by 346 Elo. Their 95% ranges do not overlap.
- Cheapest Configuration Overlapping the Top One. GPT-5.6 Terra (medium), at $0.062 per script, is the cheapest configuration whose 95% range overlaps that of GPT-5.6 Terra (ultra), at $0.275 per script: 1952 to 2041 against 2035 to 2113, so the board cannot separate them. GPT-5.6 Terra (ultra) costs about 4.4 times as much per script.
- Cheapest GPT-5.6 Terra Configuration Above Claude Sonnet 5's Best. The cheapest GPT-5.6 Terra configuration with a higher Writing Elo than Claude Sonnet 5 (max effort), at Elo 1859 and $0.696 per script, is GPT-5.6 Terra (medium), at Elo 1998 and $0.062 per script. It costs less than the configuration it beats.
- Lowest to Highest Thinking Level. GPT-5.6 Terra moves +76 Elo from medium to ultra, at about 4.4 times the cost per script. Claude Sonnet 5 moves +207 Elo from high to max effort, at about 5.8 times the cost per script.
Two Chosen Configurations Compared
Pick one configuration of each model to compare their metric scores, consistency across drafts and per-script scores. Each menu starts on the model's best configuration.
Scores by Metric
GPT-5.6 Terra (ultra) scores higher on seven of the nine metrics and Claude Sonnet 5 (max effort) on two. Weighted by each metric's share of the Writing Score, Substance, Accuracy & Value does the most to put GPT-5.6 Terra (ultra) ahead, with a 6.5-point lead on that metric. The weight beside each metric is its share of the Writing Score.
Consistency Across Drafts
| GPT-5.6 Terra (ultra) | Claude Sonnet 5 (max effort) | |
|---|---|---|
| Score spread across drafts (±) | 1.38 | 2.39 |
| Lowest script score | 79.8 Script 4 | 75.7 Script 4 |
| Highest script score | 83.0 Script 6 | 81.5 Script 9 |
| Range across scripts | 3.2 | 5.8 |
Spread is how much the Writing Score moves between a configuration's drafts, and lower is steadier. Green marks the better number in each row.
Scores by Script
Writing Score on each reference script. Gap is GPT-5.6 Terra (ultra) minus Claude Sonnet 5 (max effort), and the higher score is in bold.
| Script | GPT-5.6 Terra (ultra) | Claude Sonnet 5 (max effort) | Gap |
|---|---|---|---|
| Script 1 opinion / warning explainer | 81.1 | 77.4 | +3.7 |
| Script 2 news-analysis / skeptical explainer | 82.1 | 78.9 | +3.2 |
| Script 3 personal roadmap / opinion | 82.5 | 78.1 | +4.4 |
| Script 4 short explainer | 79.8 | 75.7 | +4.1 |
| Script 5 news-analysis / opinion explainer | 82.2 | 80.9 | +1.3 |
| Script 6 founder announcement / personal origin story | 83.0 | 81.1 | +1.9 |
| Script 7 personal technical walkthrough / agentic workflow case study | 80.6 | 81.2 | -0.6 |
| Script 8 product release announcement / personal observation | 80.3 | 79.3 | +1.0 |
| Script 9 career guide / hiring analysis | 81.8 | 81.5 | +0.3 |
| Script 10 engineering process walkthrough / presentation adaptation | 80.6 | 78.0 | +2.6 |
Scorecards and Thinking Pages
Each configuration name in the table above opens its own scorecard.
Compare With Another Model
Pick a second model. A pair with its own written match-up opens that page, and any other pair opens in the comparison tool.
Nearby Match-Ups by Best Writing Elo
Every configuration wrote five drafts for each of the same 10 briefs, from the same prompt. Generation was closed-book, with the prompt as the only source and no web search or other tools. Each judge scores every draft once: Claude Opus 5.5 at medium effort through the Claude Code subscription, GPT-6.1 Sol at medium reasoning through the Codex CLI, GLM 5.3 Flash through OpenRouter, and Jev 1.13, a typed judge from TypeSafe that answers each metric as a multiple-choice question. The channel's finished script is their reference for the voice, and it gets no score on the board itself.
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