Model vs model

Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) vs A.X-K2

A debate-ready pair page: current winner, strongest alternative, decisive benchmarks, and the warning that should travel with the claim.

Use case · Everyday chatbot
Winner · Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback)
Sources · All public sources

Winner

Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback)

Anthropic

8benchmarks won

Chat / text
Reasoning / math / science

Versus · Everyday chatbot

Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) leads this compare set for everyday chatbot.

Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback)8 of 8 wins

Verified and stable

0 shared benchmarks are still too close to call, so the win stays conditional. This compare uses all public sources, with provider-official evidence labeled separately.

Close calls: 0
Sources: All public

Full compare workspace Disagreement page

100%win share

Challenger

A.X-K2

Unknown

0benchmarks won

Chat / text
Reasoning / math / science

The cases in full

Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) case

Chat / text
Reasoning / math / science

A.X-K2 case

Chat / text
Reasoning / math / science

What changes the outcome

Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback): 118 visible benchmark gaps still leave room for the result to move.
A.X-K2: 124 visible benchmark gaps still leave room for the result to move.

Why this result is surprising

The visible shared evidence is more decisive than usual for this compare set.
Very few shared benchmarks are decisively separating these models.

Why this is not a clean win

0 shared benchmarks are still too close to call, so the win stays conditional. This compare uses all public sources, with provider-official evidence labeled separately.
A.X-K2 remains the strongest alternative once you change use case, mode, or missing-evidence assumptions.

Open full compare workspace Open evidence page Open disagreement page

Advanced framings and X composerNeutral, contrarian, open-model, and skeptical variants

Neutral analystLead with the recommendation, then attach the reason and warning.Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) leads this compare set for everyday chatbot.

ContrarianPush against the easy read and keep the strongest alternative live.Contrarian take: Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) leads this compare set for everyday chatbot.

Open-model angleBias the framing toward open weights and source transparency.Open-model angle: Model compare · Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) vs A.X-K2

Don't trust the headlineLead with the warning before you let the claim travel.Don't trust the headline: Model compare · Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) vs A.X-K2

Decisive benchmarks

8 of 132 benchmarks


Intelligence Index AA · index Text · Chat / text	5399.1% exact aliasverified runtime Row details Raw value 53 Percentile 99.1% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) Source row	23n/a exact aliasverified runtimeContext only Row details Raw value 23 Percentile n/a Last updated recent Eligibility benchmark_derived_model Identity provider alias (0.94) Source label A.X-K2 Source row	n/a
GPQA AA · % Text · Reasoning / math / science	93.4%96.3% exact aliasverified runtime Row details Raw value 93.4% Percentile 96.3% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) Source row	85.7%n/a exact aliasverified runtimeContext only Row details Raw value 85.7% Percentile n/a Last updated recent Eligibility benchmark_derived_model Identity provider alias (0.94) Source label A.X-K2 Source row	n/a
Humanity's Last Exam AA · % Text · Reasoning / math / science	58.7%99.6% exact aliasverified runtime Row details Raw value 58.7% Percentile 99.6% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) Source row	29.6%n/a exact aliasverified runtimeContext only Row details Raw value 29.6% Percentile n/a Last updated recent Eligibility benchmark_derived_model Identity provider alias (0.94) Source label A.X-K2 Source row	n/a
CritPt AA · % Text · Reasoning / math / science	31.1%98.5% exact aliasverified runtime Row details Raw value 31.1% Percentile 98.5% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) Source row	8.9%n/a exact aliasverified runtimeContext only Row details Raw value 8.9% Percentile n/a Last updated recent Eligibility benchmark_derived_model Identity provider alias (0.94) Source label A.X-K2 Source row	n/a
SciCode AA · % Code · Coding	60.9%97% exact aliasverified runtime Row details Raw value 60.9% Percentile 97% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) Source row	41%n/a exact aliasverified runtimeContext only Row details Raw value 41% Percentile n/a Last updated recent Eligibility benchmark_derived_model Identity provider alias (0.94) Source label A.X-K2 Source row	n/a
AA-Omniscience accuracy AA · % Text · Chat / text	66.2%99.8% exact aliasverified runtime Row details Raw value 66.2% Percentile 99.8% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) Source row	18.6%n/a exact aliasverified runtimeContext only Row details Raw value 18.6% Percentile n/a Last updated recent Eligibility benchmark_derived_model Identity provider alias (0.94) Source label A.X-K2 Source row	n/a
AA-Omniscience non-hallucination AA · % Text · Chat / text	29.5%61.4% exact aliasverified runtime Row details Raw value 29.5% Percentile 61.4% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) Source row	67%n/a exact aliasverified runtimeContext only Row details Raw value 67% Percentile n/a Last updated recent Eligibility benchmark_derived_model Identity provider alias (0.94) Source label A.X-K2 Source row	n/a
Long Context Reasoning AA · % Document · Long context	83%96% exact aliasverified runtime Row details Raw value 83% Percentile 96% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) Source row	70%n/a exact aliasverified runtimeContext only Row details Raw value 70% Percentile n/a Last updated recent Eligibility benchmark_derived_model Identity provider alias (0.94) Source label A.X-K2 Source row	n/a

1-8 of 8

Page 1 of 1Page size

Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) leads this compare set for everyday chatbot.

Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback)8 of 8 wins

Verified and stable

0 shared benchmarks are still too close to call, so the win stays conditional. This compare uses all public sources, with provider-official evidence labeled separately.

Close calls

Sources

All public

Intelligence Index

AA · index

Text · Chat / text

5399.1%

exact aliasverified runtime

Row details

Raw value: 53
Percentile: 99.1%
Last updated: recent
Eligibility: headline eligible
Identity: provider alias (0.94)
Source label: Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback)

Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) vs A.X-K2

Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback)

Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) leads this compare set for everyday chatbot.

A.X-K2

Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) case

A.X-K2 case

What changes the outcome

Why this result is surprising

Why this is not a clean win

Share the recommendation with the source data attached.

Open or copy the stable surfaces

Use the exact public framing

Pick the voice before you post

Compose a post that keeps the warning attached

Decisive benchmarks

Loading model comparison.

Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) vs A.X-K2

Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback)

Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) leads this compare set for everyday chatbot.

A.X-K2

Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) case

A.X-K2 case

What changes the outcome

Why this result is surprising

Why this is not a clean win

Share the recommendation with the source data attached.

Open or copy the stable surfaces

Use the exact public framing

Pick the voice before you post

Compose a post that keeps the warning attached

Decisive benchmarks