{"i":2,"comparison":{"slug":"claude-opus-5-5-vs-claude-fable-5-1","a":"claude-opus-5-5","b":"claude-fable-5-1","title":"Claude Opus 5.5 vs Claude Fable 5.1","seoTitle":"Claude Opus 5.5 vs Claude Fable 5.1: measured benchmarks","description":"Claude Opus 5.5 vs Claude Fable 5.1: 12 measured metrics from 3 studies (Pass rate on five validated tasks; more), with sample sizes and intervals.","verdict":"Claude Opus 5.5 and Claude Fable 5.1 share 12 measured metrics and 11 list-price calculations from 4 studies. No row separates them: every interval or run range overlaps, too few runs were recorded, no interval was recorded, or more is not better for that metric. The rows are 5 ties and 18 unclear; each row says why. Calculation rows are derived from list prices and recorded counts; they are not bills or runs. Some rows rest on small samples (n = 4 at the smallest).","rows":{"$k":["metric","aValue","bValue","unit","aDisplay","bDisplay","winner","basis","studySlug","n","chartId","aN","bN","aContext","bContext","rangeKind","spanKind","aRange","bRange","calculation"],"$r":[["Pass rate on five validated tasks",1,1,"rate","100% (15/15)","100% (15/15)","tie","The 95% intervals overlap (Claude Opus 5.5 80% to 100%; Claude Fable 5.1 80% to 100%), so this sample cannot separate them.","model-head-to-head",15,"h2h-pass-rate",15,15,"Claude Code · five short validated tasks","Claude Code · five short validated tasks","ci95","ci95",[0.7961,1],[0.7961,1],"\u0001"],["Total time per call",2.75,1.94,"seconds","2.75 s","1.94 s","unclear","The run ranges (fastest to slowest) overlap (Claude Opus 5.5 2.47 s to 8.91 s; Claude Fable 5.1 1.41 s to 9.83 s); the medians alone do not show a reliable difference. A range is not a confidence interval.","model-head-to-head",15,"h2h-total-latency",15,15,"Claude Code · five short validated tasks","Claude Code · five short validated tasks","range","minmax",[2.47,8.91],[1.41,9.83],"\u0001"],["Time to first useful output",1.92,1.2,"seconds","1.92 s","1.20 s","unclear","The run ranges (fastest to slowest) overlap (Claude Opus 5.5 1.56 s to 7.23 s; Claude Fable 5.1 0.95 s to 7.90 s); the medians alone do not show a reliable difference. A range is not a confidence interval.","model-head-to-head",15,"h2h-first-useful-latency",15,15,"Claude Code · five short validated tasks","Claude Code · five short validated tasks","range","minmax",[1.56,7.23],[0.95,7.9],"\u0001"],["Input tokens per call: what the CLI sends (Cache read)",1401,2760,"tokens","1,401","2,760","unclear","More or fewer tokens is not better or worse by itself; this row describes behaviour, not a winner.","model-head-to-head",15,"h2h-input-tokens",15,15,"Claude Code · five short validated tasks","Claude Code · five short validated tasks","\u0001","\u0001","\u0001","\u0001","\u0001"],["Input tokens per call: what the CLI sends (Other input)",680,473,"tokens","680","473","unclear","More or fewer tokens is not better or worse by itself; this row describes behaviour, not a winner.","model-head-to-head",15,"h2h-input-tokens",15,15,"Claude Code · five short validated tasks","Claude Code · five short validated tasks","\u0001","\u0001","\u0001","\u0001","\u0001"],["Output tokens per call (Output tokens)",64,64,"tokens","64","64","tie","Same value. More or fewer is not better by itself for this metric.","model-head-to-head",15,"h2h-output-tokens",15,15,"Claude Code · five short validated tasks","Claude Code · five short validated tasks","\u0001","\u0001","\u0001","\u0001","\u0001"],["List-price cost per call (calculation)",0.00688,0.00987,"usd","$0.0069","$0.0099","unclear","The run ranges (fastest to slowest) overlap (Claude Opus 5.5 $0.0059 to $0.022; Claude Fable 5.1 $0.0049 to $0.058); the medians alone do not show a reliable difference. A range is not a confidence interval.","model-head-to-head",15,"h2h-list-price-per-call",15,15,"Claude Code · five short validated tasks","Claude Code · five short validated tasks","range","minmax",[0.00592,0.02226],[0.0049,0.05843],true],["List-price cost per passing answer (calculation)",0.01009,0.02054,"usd","$0.010","$0.021","unclear","No interval or range was recorded for either side, so the gap ($0.010 vs $0.021, 2.0x) is not tested against run-to-run variation.","model-head-to-head",15,"h2h-cost-per-pass",15,15,"Claude Code · five short validated tasks","Claude Code · five short validated tasks","\u0001","\u0001","\u0001","\u0001",true],["Pass rate on eight hard tasks (Strict pass)",1,1,"rate","100% (24/24)","100% (24/24)","tie","The 95% intervals overlap (Claude Opus 5.5 86% to 100%; Claude Fable 5.1 86% to 100%), so this sample cannot separate them.","hard-model-head-to-head",24,"hard-h2h-pass-rate",24,24,"Claude Code · eight hard validated tasks","Claude Code · eight hard validated tasks","ci95","ci95",[0.862,1],[0.862,1],"\u0001"],["Pass rate on eight hard tasks (Lenient (format misses counted))",1,1,"rate","100% (24/24)","100% (24/24)","tie","The 95% intervals overlap (Claude Opus 5.5 86% to 100%; Claude Fable 5.1 86% to 100%), so this sample cannot separate them.","hard-model-head-to-head",24,"hard-h2h-pass-rate",24,24,"Claude Code · eight hard validated tasks","Claude Code · eight hard validated tasks","ci95","ci95",[0.862,1],[0.862,1],"\u0001"],["Total time per call on hard tasks (separate batches)",9.18,16.13,"seconds","9.18 s","16.1 s","unclear","The run ranges (fastest to slowest) overlap (Claude Opus 5.5 4.24 s to 27.2 s; Claude Fable 5.1 4.46 s to 90.0 s); the medians alone do not show a reliable difference. A range is not a confidence interval.","hard-model-head-to-head",24,"hard-h2h-total-latency",24,24,"Claude Code · eight hard validated tasks","Claude Code · eight hard validated tasks","range","minmax",[4.24,27.21],[4.46,90],"\u0001"],["Time to first useful output on hard tasks",6.78,11.63,"seconds","6.78 s","11.6 s","unclear","The run ranges (fastest to slowest) overlap (Claude Opus 5.5 2.39 s to 21.8 s; Claude Fable 5.1 2.00 s to 85.3 s); the medians alone do not show a reliable difference. A range is not a confidence interval.","hard-model-head-to-head",24,"hard-h2h-first-useful-latency",24,24,"Claude Code · eight hard validated tasks","Claude Code · eight hard validated tasks","range","minmax",[2.39,21.77],[2,85.33],"\u0001"],["Output tokens per call on hard tasks (Output tokens)",945,1366,"tokens","945","1,366","unclear","More or fewer tokens is not better or worse by itself; this row describes behaviour, not a winner.","hard-model-head-to-head",24,"hard-h2h-output-tokens",24,24,"Claude Code · eight hard validated tasks","Claude Code · eight hard validated tasks","\u0001","\u0001","\u0001","\u0001","\u0001"],["List-price cost per strict pass on hard tasks (calculation)",0.02824,0.09331,"usd","$0.028","$0.093","unclear","No interval or range was recorded for either side, so the gap ($0.028 vs $0.093, 3.3x) is not tested against run-to-run variation.","hard-model-head-to-head",24,"hard-h2h-cost-per-pass",24,24,"Claude Code · eight hard validated tasks","Claude Code · eight hard validated tasks","\u0001","\u0001","\u0001","\u0001",true],["Reasoning share of output tokens per call on hard tasks (calculation)",54.79,64.24,"percent","54.8%","64.2%","unclear","More or fewer percent is not better or worse by itself; this row describes behaviour, not a winner.","thinking-token-bill",24,"thinking-bill-share",24,24,"Claude Code","Claude Code","range","minmax",[29.92,95.6],[23.44,97.19],true],["List-price cost per call: reasoning, remaining output and input (calculation) (Reasoning (output tokens))",0.012528,0.053696,"usd","$0.013","$0.054","unclear","More or fewer usd is not better or worse by itself; this row describes behaviour, not a winner.","thinking-token-bill",24,"thinking-bill-cost-per-call",24,24,"Claude Code","Claude Code","\u0001","\u0001","\u0001","\u0001",true],["List-price cost per call: reasoning, remaining output and input (calculation) (Remaining output (visible-answer estimate))",0.008003,0.018702,"usd","$0.0080","$0.019","unclear","More or fewer usd is not better or worse by itself; this row describes behaviour, not a winner.","thinking-token-bill",24,"thinking-bill-cost-per-call",24,24,"Claude Code","Claude Code","\u0001","\u0001","\u0001","\u0001",true],["List-price cost per call: reasoning, remaining output and input (calculation) (Input (prompt, cache priced))",0.00771,0.02091,"usd","$0.0077","$0.021","unclear","More or fewer usd is not better or worse by itself; this row describes behaviour, not a winner.","thinking-token-bill",24,"thinking-bill-cost-per-call",24,24,"Claude Code","Claude Code","\u0001","\u0001","\u0001","\u0001",true],["Reasoning share on short tasks vs hard tasks (calculation) (Eight hard tasks)",54.79,64.24,"percent","54.8%","64.2%","unclear","More or fewer percent is not better or worse by itself; this row describes behaviour, not a winner.","thinking-token-bill",24,"thinking-bill-short-vs-hard",24,24,"Claude Code","Claude Code","range","minmax",[29.92,95.6],[23.44,97.19],true],["Reasoning share on short tasks vs hard tasks (calculation) (Five short tasks)",0,0,"percent","0%","0%","tie","Same value. More or fewer is not better by itself for this metric.","thinking-token-bill",15,"thinking-bill-short-vs-hard",15,15,"Claude Code","Claude Code","range","minmax",[0,93.33],[0,74.01],true],["Time to first text: a 250-line answer, six models",1.97,4.43,"seconds","1.97 s","4.43 s","unclear","The run ranges (fastest to slowest) overlap (Claude Opus 5.5 1.70 s to 2.35 s; Claude Fable 5.1 2.27 s to 4.64 s); the medians alone do not show a reliable difference. A range is not a confidence interval.","llm-speed-anatomy",4,"speed-anatomy-first-text",4,4,"Claude Code","Claude Code","range","minmax",[1.7,2.35],[2.27,4.64],"\u0001"],["Output speed after the first text: visible tokens per second (calculation)",155.5,122.6,"tokens","156","123","unclear","More or fewer tokens is not better or worse by itself; this row describes behaviour, not a winner.","llm-speed-anatomy",4,"speed-anatomy-output-speed",4,4,"Claude Code","Claude Code","range","minmax",[154.6,156.4],[120.9,131.4],true],["Output speed in characters per second after the first text (calculation)",347,273,"count","347","273","unclear","More or fewer count is not better or worse by itself; this row describes behaviour, not a winner.","llm-speed-anatomy",4,"speed-anatomy-chars-per-second",4,4,"Claude Code","Claude Code","range","minmax",[345,349],[270,293],true]]}}}