Model vs model

Claude Fable 5 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
Sources · All public sources

Winner

Claude Fable 5

Anthropic

11benchmarks won

Coding

Versus · Everyday chatbot

Claude Fable 5 leads this compare set for everyday chatbot.

Claude Fable 511 of 11 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 case

Coding

A.X-K2 case

Chat / text
Reasoning / math / science

What changes the outcome

Claude Fable 5: 89 visible benchmark gaps still leave room for the result to move.
A.X-K2: 126 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

Decisive benchmarks

11 of 138 benchmarks


Intelligence Index AA · index Text · Chat / text	6299.6% exact aliasverified runtime Row details Raw value 62 Percentile 99.6% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 Fallback) Source row	35n/a exact aliasverified runtimeContext only Row details Raw value 35 Percentile n/a Last updated recent Eligibility benchmark_derived_model Identity provider alias (0.94) Source label A.X-K2 Source row	n/a
Coding Index AA · index Code · Coding	7697.9% exact aliasverified runtime Row details Raw value 76 Percentile 97.9% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 Fallback) Source row	39n/a exact aliasverified runtimeContext only Row details Raw value 39 Percentile n/a Last updated recent Eligibility benchmark_derived_model Identity provider alias (0.94) Source label A.X-K2 Source row	n/a
Agentic Index AA · index Code · Coding	5795.5% exact aliasverified runtime Row details Raw value 57 Percentile 95.5% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 Fallback) Source row	26n/a exact aliasverified runtimeContext only Row details Raw value 26 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	92.6%97.3% exact aliasverified runtime Row details Raw value 92.6% Percentile 97.3% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 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	55.5%100% exact aliasverified runtime Row details Raw value 55.5% Percentile 100% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 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	28.6%99.2% exact aliasverified runtime Row details Raw value 28.6% Percentile 99.2% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 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	60.2%100% exact aliasverified runtime Row details Raw value 60.2% Percentile 100% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 Fallback) Source row	38.5%n/a exact aliasverified runtimeContext only Row details Raw value 38.5% 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	65.4%100% exact aliasverified runtime Row details Raw value 65.4% Percentile 100% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 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	36.4%77.6% exact aliasverified runtime Row details Raw value 36.4% Percentile 77.6% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 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
GDPval-AA AA · rating Text · Professional reasoning	1,73897.6% exact aliasverified runtime Row details Raw value 1,738 Percentile 97.6% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 Fallback) Source row	1,109n/a exact aliasverified runtimeContext only Row details Raw value 1,109 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	76.7%95.8% exact aliasverified runtime Row details Raw value 76.7% Percentile 95.8% Last updated recent Eligibility headline eligible Identity provider alias (0.94) Source label Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 Fallback) Source row	66%n/a exact aliasverified runtimeContext only Row details Raw value 66% Percentile n/a Last updated recent Eligibility benchmark_derived_model Identity provider alias (0.94) Source label A.X-K2 Source row	n/a

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Intelligence Index

AA · index

Text · Chat / text

6299.6%

exact aliasverified runtime

Row details

Raw value: 62
Percentile: 99.6%
Last updated: recent
Eligibility: headline eligible
Identity: provider alias (0.94)
Source label: Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 Fallback)

Source row

35n/a

exact aliasverified runtimeContext only

Row details

Raw value: 35
Percentile: n/a
Last updated: recent
Eligibility: benchmark_derived_model
Identity: provider alias (0.94)
Source label: A.X-K2

Source row

n/a

Coding Index

AA · index

Code · Coding

7697.9%

exact aliasverified runtime

Row details

Raw value: 76
Percentile: 97.9%
Last updated: recent
Eligibility: headline eligible
Identity: provider alias (0.94)
Source label: Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 Fallback)

Source row

39n/a

exact aliasverified runtimeContext only

Row details

Raw value: 39
Percentile: n/a
Last updated: recent
Eligibility: benchmark_derived_model
Identity: provider alias (0.94)
Source label: A.X-K2

Source row

n/a

Agentic Index

AA · index

Code · Coding

5795.5%

exact aliasverified runtime

Row details

Raw value: 57
Percentile: 95.5%
Last updated: recent
Eligibility: headline eligible
Identity: provider alias (0.94)
Source label: Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 Fallback)

Source row

26n/a

exact aliasverified runtimeContext only

Row details

Raw value: 26
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

92.6%97.3%

exact aliasverified runtime

Row details

Raw value: 92.6%
Percentile: 97.3%
Last updated: recent
Eligibility: headline eligible
Identity: provider alias (0.94)
Source label: Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 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

55.5%100%

exact aliasverified runtime

Row details

Raw value: 55.5%
Percentile: 100%
Last updated: recent
Eligibility: headline eligible
Identity: provider alias (0.94)
Source label: Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 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

28.6%99.2%

exact aliasverified runtime

Row details

Raw value: 28.6%
Percentile: 99.2%
Last updated: recent
Eligibility: headline eligible
Identity: provider alias (0.94)
Source label: Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 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

60.2%100%

exact aliasverified runtime

Row details

Raw value: 60.2%
Percentile: 100%
Last updated: recent
Eligibility: headline eligible
Identity: provider alias (0.94)
Source label: Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 Fallback)

Source row

38.5%n/a

exact aliasverified runtimeContext only

Row details

Raw value: 38.5%
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

65.4%100%

exact aliasverified runtime

Row details

Raw value: 65.4%
Percentile: 100%
Last updated: recent
Eligibility: headline eligible
Identity: provider alias (0.94)
Source label: Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 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

36.4%77.6%

exact aliasverified runtime

Row details

Raw value: 36.4%
Percentile: 77.6%
Last updated: recent
Eligibility: headline eligible
Identity: provider alias (0.94)
Source label: Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 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

GDPval-AA

AA · rating

Text · Professional reasoning

1,73897.6%

exact aliasverified runtime

Row details

Raw value: 1,738
Percentile: 97.6%
Last updated: recent
Eligibility: headline eligible
Identity: provider alias (0.94)
Source label: Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 Fallback)

Source row

1,109n/a

exact aliasverified runtimeContext only

Row details

Raw value: 1,109
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

76.7%95.8%

exact aliasverified runtime

Row details

Raw value: 76.7%
Percentile: 95.8%
Last updated: recent
Eligibility: headline eligible
Identity: provider alias (0.94)
Source label: Claude Fable 5 (Adaptive Reasoning, Max Effort, Opus 4.8 Fallback)

Source row

66%n/a

exact aliasverified runtimeContext only

Row details

Raw value: 66%
Percentile: n/a
Last updated: recent
Eligibility: benchmark_derived_model
Identity: provider alias (0.94)
Source label: A.X-K2

Source row

n/a

Claude Fable 5 vs A.X-K2

Claude Fable 5

Claude Fable 5 leads this compare set for everyday chatbot.

A.X-K2

Claude Fable 5 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 vs A.X-K2

Claude Fable 5

Claude Fable 5 leads this compare set for everyday chatbot.

A.X-K2

Claude Fable 5 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