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A · closed · Claude Fable / Mythos

Claude Fable 5

Anthropic

B · closed · Claude Fable / Mythos

Claude Fable 5.1

Anthropic

2:15

overall capability wins (3 ties across 20 scored). Claude Fable 5.1 leads overall.

  • Reasoning0:5
  • Coding1:5
  • Arena1:0
  • Agents0:4
  • Tool use0:1
  • Composite indices0:2

Verdict

Claude Fable 5.1 leads coding (widest gap: +130.0 on WebDev Elo); Claude Fable 5 ranks higher on LMArena (+7 Elo).

  • Claude Fable 5.1 leads coding (widest gap: +130.0 on WebDev Elo)
  • Claude Fable 5 ranks higher on LMArena (+7 Elo)

Cost for 1M in + 250K out

Illustrative chat workload at primary-provider list prices.

Claude Fable 5
$22.50
Claude Fable 5.1
$22.50

Price per 1M tokens

Full comparison

Organization

Anthropic

Anthropic

Family

Claude Fable / Mythos

Claude Fable / Mythos

License

Proprietary

Proprietary

Open weights

No

No

Release

Jun 9, 2026

Sep 1, 2026

Knowledge cutoff

-

-

API / provider

Anthropic

Anthropic

Modalities

text, image → text

text, image → text

Specs

Context window

1M

1M

tie

Max output

128K

128K

tie

Parameters

—

—

—

Pricing

Input $/1M

$10

$10

tie

Output $/1M

$50

$50

tie

Blended $/1M (3∶1)

$20

$20

tie

Speed

tok/s

58

-

—

TTFT (s)

0.7

-

—

Reasoning

MMLU-Pro

—

—

—

GPQA Diamond

92.6

93.7

B +1.1 pts

Humanity's Last Exam

55.5

59.0

B +3.5 pts

AIME 2025

—

—

—

MATH-500

—

—

—

Humanity's Last Exam (with tools)

—

65.6

—

AA-Omniscience Accuracy

65.4

67.2

B +1.8 pts

AA-LCR v1.1

82.3

83.0

B +0.7 pts

CritPt

28.6

29.7

B +1.1 pts

MMMU-Pro

—

—

—

IFBench

63.5

—

—

Chartography

—

—

—

Chartography (With Tools)

—

—

—

Coding

SWE-bench Verified

—

—

—

SWE-bench Pro

80.0

—

—

SWE-bench Multilingual

—

—

—

LiveCodeBench

—

—

—

Terminal-Bench 2.1

84.6

91.4

B +6.8 pts

Aider Polyglot

—

—

—

Terminal-Bench 3

34.1

—

—

BigCodeBench

—

—

—

SciCode

61.0

63.0

B +2.0 pts

CursorBench

70.5

73.4

B +2.9 pts

SWE-Rebench

64.5

—

—

NL2Repo-Bench

—

—

—

DeepSWE

69.9

67.4

A +2.5 pts

WebDev Arena

1,628

1,758

B +130 Elo

Terminal-Bench 4.0

44.6

57.9

B +13.3 pts

CursorBench 4.0

—

51.8

—

FrontierCode v1.1 (Main)

—

—

—

Arena

LMArena Elo

1,506

1,499

A +7 Elo

Claude Fable 5

Context
1M / 128K out
Parameters
—
Price
$10 / $50
Speed
58 tok/s · 0.7s TTFT
Modalities
text, image → text
License
Proprietary

Mythos-class Anthropic model optimized for long-horizon coding and writing; premium pricing relative to Opus 5.

Claude Fable 5.1

Context
1M / 128K out
Parameters
—
Price
$10 / $50
Speed
—
Modalities
text, image → text
License
Proprietary

Anthropic's September 2026 successor to Fable 5 - same input/output pricing with cache reads cut to a quarter of the price, and gains concentrated in long-horizon agentic coding, knowledge work, research, and computer use.

Benchmark charts

Winner bars are emphasized. Per-benchmark deltas sit above each chart.

Reasoning & knowledge

GPQA: B +1.1HLE: B +3.5CritPt: B +1.1AA-LCR: B +0.7Omniscience Acc.: B +1.8

Math

FrontierMath T4: tie

Coding

TermBench: B +6.8TermBench 4: B +13.3SciCode: B +2.0CursorBench: B +2.9DeepSWE: A +2.5WebDev Elo: B +130

Tool use & function calling

τ³-Banking: B +9.1

Agents & computer use

AutoBench: B +14.0TB-Science: B +31.2OSWorld Partial: B +5.0OSWorld Strict: B +5.6

Arena

Arena Elo: A +7

Composite indices

AA Index: B +3.6AA Index v4.3: B +3.7

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