Model Comparison
GPT-5.6 Terra vs Claude Haiku 5.5
Too close to call: the best configurations, GPT-5.6 Terra (ultra) and Claude Haiku 5.5 (max effort), are 65 Elo apart, and their 95% ranges overlap. Among 78 models, each ranked by its best configuration, GPT-5.6 Terra is #13 and Claude Haiku 5.5 is #16. Cost per script: $0.275 for GPT-5.6 Terra (ultra) and $0.103 for Claude Haiku 5.5 (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) when the hook and the voice matter, since it has the best Tone & Voice Match on this page and the board can't separate it from ultra, at $0.062 a script.
PickClaude Haiku 5.5
Claude Haiku 5.5 (xhigh)
Pick Claude Haiku 5.5 (xhigh) for routine scripts, since its range overlaps GPT-5.6 Terra (medium) and it costs $0.029 a script, about half as much.
Thinking does almost all the work for Claude Haiku 5.5 and much less for GPT-5.6 Terra. Haiku climbs 505 Elo from low to max effort, while Terra moves 76 from medium to ultra at more than four times the cost. Ranked by best setting, GPT-5.6 Terra is #13 of 78 models and Claude Haiku 5.5 the #16 model, and the board can't separate those settings: GPT-5.6 Terra (ultra) leads Claude Haiku 5.5 (max effort) by 65 Elo with overlapping 95% ranges. GPT-5.6 Terra (medium) overlaps both of them, costs $0.062 a script and takes 1.4 minutes, where Haiku at max effort costs $0.103 and takes over twelve. So I'd skip both top settings. Claude Haiku 5.5 (xhigh) is cheaper at $0.029, about half of Terra at medium, and its range overlaps medium's and sits clear below ultra's. Below xhigh, Haiku falls off fast: at medium, the one level name both use, Terra leads by 378 Elo with separate ranges. Terra writes the better hook at both settings, and GPT-5.6 Terra (medium) has the best Tone & Voice Match on the page. Terra at medium is the setting I'd run.
Disclosure: GPT-5.6 Terra and Claude Haiku 5.5 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 Haiku 5.5, 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 |
| Claude Haiku 5.5 (max effort) | 2009 | 1972 to 2044 | 80.8 | $0.103 | 12.6 min | #31 |
| GPT-5.6 Terra (medium) | 1998 | 1952 to 2041 | 80.7 | $0.062 | 1.4 min | #33 |
| Claude Haiku 5.5 (xhigh) | 1927 | 1883 to 1965 | 80.0 | $0.029 | 3.6 min | #41 |
| Claude Haiku 5.5 (high) | 1723 | 1679 to 1760 | 78.0 | $0.012 | 1.5 min | #53 |
| Claude Haiku 5.5 (medium) | 1620 | 1572 to 1670 | 76.7 | $0.0067 | 0.8 min | #62 |
| Claude Haiku 5.5 (low) | 1504 | 1461 to 1550 | 75.2 | $0.0045 | 0.5 min | #74 |
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) at Elo 2074 (range 2035 to 2113) and Claude Haiku 5.5 (max effort) at Elo 2009 (range 1972 to 2044) have overlapping 95% ranges, so the board cannot separate the two best configurations.
- 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 Haiku 5.5 (low) at Elo 1504 and $0.0045 per script by 494 Elo. Their 95% ranges do not overlap.
- Same Level Name, Side by Side. At medium, the one level name both models use, GPT-5.6 Terra has the higher Writing Elo: 1998 against 1620. Their 95% ranges do not overlap there. Level names come from each provider, so the same name does not promise the same reasoning budget.
- 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 Haiku 5.5's Best. The cheapest GPT-5.6 Terra configuration with a higher Writing Elo than Claude Haiku 5.5 (max effort), at Elo 2009 and $0.103 per script, is GPT-5.6 Terra (ultra), at Elo 2074 and $0.275 per script. Their 95% ranges overlap, so the board cannot separate them. It costs about 2.7 times as much per script.
- 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 Haiku 5.5 moves +505 Elo from low to max effort, at about 23 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 five of the nine metrics and Claude Haiku 5.5 (max effort) on four. Weighted by each metric's share of the Writing Score, Hook Strength does the most to put GPT-5.6 Terra (ultra) ahead, with a 3.3-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 Haiku 5.5 (max effort) | |
|---|---|---|
| Score spread across drafts (±) | 1.38 | 1.55 |
| Lowest script score | 79.8 Script 4 | 78.2 Script 10 |
| Highest script score | 83.0 Script 6 | 82.6 Script 4 |
| Range across scripts | 3.2 | 4.4 |
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 Haiku 5.5 (max effort), and the higher score is in bold.
| Script | GPT-5.6 Terra (ultra) | Claude Haiku 5.5 (max effort) | Gap |
|---|---|---|---|
| Script 1 opinion / warning explainer | 81.1 | 80.3 | +0.8 |
| Script 2 news-analysis / skeptical explainer | 82.1 | 80.7 | +1.4 |
| Script 3 personal roadmap / opinion | 82.5 | 80.8 | +1.7 |
| Script 4 short explainer | 79.8 | 82.6 | -2.8 |
| Script 5 news-analysis / opinion explainer | 82.2 | 81.7 | +0.5 |
| Script 6 founder announcement / personal origin story | 83.0 | 81.1 | +1.9 |
| Script 7 personal technical walkthrough / agentic workflow case study | 80.6 | 80.0 | +0.6 |
| Script 8 product release announcement / personal observation | 80.3 | 81.3 | -1.0 |
| Script 9 career guide / hiring analysis | 81.8 | 81.5 | +0.3 |
| Script 10 engineering process walkthrough / presentation adaptation | 80.6 | 78.2 | +2.4 |
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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