Model Comparison
Claude Fable 5.1 vs Claude Fable 5
Claude Fable 5.1 (max effort) leads Claude Fable 5 (max effort, Opus 4.8 fallback) by 314 Elo, and their 95% ranges sit 215 Elo apart. Even Claude Fable 5.1's lowest-rated configuration, Claude Fable 5.1 (high), ranks above Claude Fable 5 (max effort, Opus 4.8 fallback). Among 78 models, each ranked by its best configuration, Claude Fable 5.1 is #3 and Claude Fable 5 is #6. Cost per script: $3.56 for Claude Fable 5.1 (max effort) and $3.20 for Claude Fable 5 (max effort, Opus 4.8 fallback).
Last updated , from board data generated at 01:13 UTC.
Picks and Verdict
PickClaude Fable 5.1
Claude Fable 5.1 (high)
Pick Claude Fable 5.1 (high) as the direct replacement for Fable 5, since it ranks above the old max effort setting at $1.85 a script instead of $3.20.
PickClaude Fable 5
Claude Fable 5 (high)
Pick Claude Fable 5 (high) if a pipeline still depends on it, at $1.34 a script and 4.9 minutes, the cheapest and fastest setting on this page.
If you still run Claude Fable 5 at max effort, switching saves money and gets you a higher-rated script. Claude Fable 5.1 (high) costs $1.85 a script against $3.20 for Claude Fable 5 (max effort, Opus 4.8 fallback), and sits 113 Elo higher, with 95% ranges just apart. Claude Fable 5.1 (max effort) goes further, 314 Elo above the older model's best with no overlap: the #3 model of 78 against the #6 model. The two generations also respond differently to thinking. Fable 5.1 gains 201 Elo from high to max effort with separate ranges, so the extra spend buys a step the board can see. Fable 5 gains 83 Elo for about 2.4 times the price, and its two ranges overlap, so the board can't separate them. The older model keeps one small edge, YouTube structure, where its max setting leads Fable 5.1's by under a point. Its hooks trail by about four points, though, and its drafts swing more at both settings. I'd switch to Fable 5.1: high already outranks Fable 5's best for less, and max effort is there for the scripts I record.
Disclosure: both models come from the same lab as one of the four judges, Claude Opus 5.5. The other judges sit outside that lab, so 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 Claude Fable 5.1 and Claude Fable 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 |
|---|---|---|---|---|---|---|
| Claude Fable 5.1 (max effort) | 2553 | 2513 to 2587 | 84.5 | $3.56 | 12.3 min | #4 |
| Claude Fable 5.1 (high) | 2352 | 2302 to 2403 | 83.4 | $1.85 | 6.3 min | #9 |
| Claude Fable 5 (max effort, Opus 4.8 fallback) | 2239 | 2186 to 2298 | 82.9 | $3.20 | 12.5 min | #12 |
| Claude Fable 5 (high) | 2156 | 2102 to 2204 | 81.9 | $1.34 | 4.9 min | #22 |
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. Claude Fable 5.1 (max effort) leads Claude Fable 5 (max effort, Opus 4.8 fallback) by 314 Elo, and their 95% ranges do not overlap (2513 to 2587 against 2186 to 2298), which is strong evidence for that order.
- Every Claude Fable 5.1 Configuration Ranks Higher. Both Claude Fable 5.1 configurations rank above both Claude Fable 5 configurations: the lowest-rated, Claude Fable 5.1 (high) at Elo 2352, still beats Claude Fable 5 (max effort, Opus 4.8 fallback) at Elo 2239. Their 95% ranges do not overlap.
- Lowest Thinking Levels Head to Head. At their lowest thinking levels, Claude Fable 5.1 (high) at Elo 2352 and $1.85 per script leads Claude Fable 5 (high) at Elo 2156 and $1.34 per script by 196 Elo. Their 95% ranges do not overlap.
- Same Level Name, Side by Side. Claude Fable 5.1 has the higher Writing Elo at every level name both models use: high and max. The 95% ranges do not overlap at any of them. Level names come from each provider, so the same name does not promise the same reasoning budget.
- Cheapest Claude Fable 5.1 Configuration Above Claude Fable 5's Best. The cheapest Claude Fable 5.1 configuration with a higher Writing Elo than Claude Fable 5 (max effort, Opus 4.8 fallback), at Elo 2239 and $3.20 per script, is Claude Fable 5.1 (high), at Elo 2352 and $1.85 per script. It costs less than the configuration it beats.
- Lowest to Highest Thinking Level. Claude Fable 5.1 moves +201 Elo from high to max effort, at about 1.9 times the cost per script. Claude Fable 5 moves +83 Elo from high to max effort, at about 2.4 times the cost per script.
Writing Elo at Each Shared Level Name
| Level | Claude Fable 5.1 | Claude Fable 5 | Gap | 95% Ranges |
|---|---|---|---|---|
| high | 2352 | 2156 | +196 | Separate |
| max | 2553 | 2239 | +314 | Separate |
Gap is Claude Fable 5.1 minus Claude Fable 5 at the same level name, using each model's highest-rated configuration at that level.
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
Claude Fable 5.1 (max effort) scores higher on eight of the nine metrics and Claude Fable 5 (max effort, Opus 4.8 fallback) on one. Weighted by each metric's share of the Writing Score, Writing Craft & Clarity does the most to put Claude Fable 5.1 (max effort) 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
| Claude Fable 5.1 (max effort) | Claude Fable 5 (max effort, Opus 4.8 fallback) | |
|---|---|---|
| Score spread across drafts (±) | 1.13 | 1.96 |
| Lowest script score | 82.8 Script 10 | 81.2 Script 8 |
| Highest script score | 86.2 Script 9 | 86.4 Script 7 |
| Range across scripts | 3.4 | 5.2 |
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 Claude Fable 5.1 (max effort) minus Claude Fable 5 (max effort, Opus 4.8 fallback), and the higher score is in bold.
| Script | Claude Fable 5.1 (max effort) | Claude Fable 5 (max effort, Opus 4.8 fallback) | Gap |
|---|---|---|---|
| Script 1 opinion / warning explainer | 83.3 | 83.1 | +0.2 |
| Script 2 news-analysis / skeptical explainer | 83.8 | 83.7 | +0.1 |
| Script 3 personal roadmap / opinion | 84.0 | 81.6 | +2.4 |
| Script 4 short explainer | 85.2 | 81.6 | +3.6 |
| Script 5 news-analysis / opinion explainer | 84.9 | 82.5 | +2.4 |
| Script 6 founder announcement / personal origin story | 85.0 | 82.9 | +2.1 |
| Script 7 personal technical walkthrough / agentic workflow case study | 85.3 | 86.4 | -1.1 |
| Script 8 product release announcement / personal observation | 84.7 | 81.2 | +3.5 |
| Script 9 career guide / hiring analysis | 86.2 | 83.2 | +3.0 |
| Script 10 engineering process walkthrough / presentation adaptation | 82.8 | 82.8 | 0.0 |
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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