Head-to-head comparison

Claude Fable 5.1 vs. GPT-6 Astra

Compare published benchmark results from matching versions and cohorts, API pricing, and technical specifications. Any documented test setup differences remain visible.

shared result series: 22
distinct benchmarks: 22
latest retrieval: 2026-09-29

First modelSecond model

Specifications

General specifications

Release date, availability, context window, architecture, and published parameter counts at a glance. Undisclosed details remain marked as unavailable.

Specifications for Claude Fable 5.1 and GPT-6 Astra
Attribute	Claude Fable 5.1	GPT-6 Astra
Provider	Anthropic	OpenAI
Released	Sep 1, 2026	Sep 3, 2026
Availability	Active	Limited access
Model type	Proprietary	Proprietary
Parameters	Not published	Not published
Architecture	Not published	Not published
Context window	1,000,000 tokens	1,050,000 tokens
Knowledge cutoff	June 2026	April 30, 2026
Technical sources	Model	Model, Context

Pricing

API pricing compared

The table compares official standard API rates per 1M tokens, including published cache pricing. Batch, fast, priority, regional surcharges, tool calls, and cloud platform pricing are excluded.

API pricing for Claude Fable 5.1 and GPT-6 Astra
Price type	Claude Fable 5.1	GPT-6 Astra
API input	$10	$10 ≤272K / $20 >272K
API output	$50	$50 ≤272K / $75 >272K
Cache read	$0.25	$1 ≤272K / $2 >272K
Cache write (5 min.)	$12.5	$12.5 ≤272K / $25 >272K
Cache write (1 hr.)	$20	Not listed
Price verified	09/22/2026 Source	09/22/2026 Source

Claude Fable 5.1GPT-6 Astra

API inputUSD per 1M tokens, base tier

Claude Fable 5.1$10

GPT-6 Astra$10

API outputUSD per 1M tokens, base tier

Claude Fable 5.1$50

GPT-6 Astra$50

Cache readUSD per 1M tokens, base tier

Claude Fable 5.1$0.25

GPT-6 Astra$1

Key to the marks:better valuebetter, but not conclusivetie

Pricing by provider

Direct developer pricing and provider endpoint tariffs routed through OpenRouter are listed separately. Prices are in USD per 1M tokens. Context-dependent direct tiers plus regional, Flex, Priority, and other OpenRouter tariffs remain individually identifiable.

Provider pricing for Claude Fable 5.1 and GPT-6 Astra
Model	Provider	Purchase route and tariff	Input per 1M tokens	Output per 1M tokens	Source
Claude Fable 5.1	Anthropic	Direct from developerStandard API	Lowest listed price: $10	Lowest listed price: $50	Source09/22/2026
	Amazon Bedrock	Via OpenRouteramazon-bedrock	Lowest listed price: $10	Lowest listed price: $50	Source10/15/2026
	Anthropic	Via OpenRouteranthropic	Lowest listed price: $10	Lowest listed price: $50	Source10/15/2026
	Azure	Via OpenRouterazure	Lowest listed price: $10	Lowest listed price: $50	Source10/15/2026
	Google	Via OpenRoutergoogle-vertex/global	Lowest listed price: $10	Lowest listed price: $50	Source10/15/2026
GPT-6 Astra	OpenAI	Direct from developerUp to 272,000 context tokens	$10	$50	Source09/22/2026
	OpenAI	Direct from developerAbove 272,000 context tokens	$20	$75	Source09/22/2026
	Amazon Bedrock	Via OpenRouteramazon-bedrock/us-west-2	$11	$55	Source10/15/2026
	Azure	Via OpenRouterazure/us	$11	$55	Source10/15/2026
	OpenAI	Via OpenRouteropenai	$10	$50	Source10/15/2026
	OpenAI	Via OpenRouteropenai/fast	$20	$100	Source10/15/2026
	OpenAI	Via OpenRouteropenai/flex	Lowest listed price: $5	Lowest listed price: $25	Source10/15/2026
	OpenAI	Via OpenRouteropenai/ultrafast	$60	$300	Source10/15/2026

Performance

Shared benchmarks

Only published results with the same benchmark version, task, metric, and comparison cohort are paired. Different reasoning levels, agents, harnesses, or output limits appear directly in the table.

Capability profile from matched benchmarks

Each axis averages directly matched benchmark families. A value of 100 means the stronger value within this pair, not a universal quality score.

Claude Fable 5.1

GPT-6 Astra

Coding: 93 / 96.1 (6 benchmark families)

Mathematics: 100 / 99 (1 benchmark family)

Finance: 100 / 88.7 (3 benchmark families)

Legal: 100 / 76.3 (2 benchmark families)

Agentic tasks: 83.7 / 100 (2 benchmark families)

Cybersecurity: 100 / 58.3 (1 benchmark family)

Health: 100 / 93.5 (2 benchmark families)

Education: 100 / 95.6 (1 benchmark family)

22 matched rows from 21 benchmark families were considered. The radar shows 8 of 10 comparable categories.

Claude Fable 5.1GPT-6 Astra

Code MigrationOverall. Higher is better. No documented setup difference

Claude Fable 5.154.607 %

GPT-6 Astra67.74 %

CyberBench v1.1Overall. Higher is better. No documented setup difference

Claude Fable 5.170.416 %

GPT-6 Astra41.072 %

EMBOverall. Higher is better. No documented setup difference

Claude Fable 5.176.67 %

GPT-6 Astra71.7 %

Finance Agent (v2)Overall. Higher is better. No documented setup difference

Claude Fable 5.158.877 %

GPT-6 Astra53.54 %

Harvey's Legal Agent BenchmarkOverall · Task fully resolved. Higher is better. No documented setup difference

Claude Fable 5.16.667 %

GPT-6 Astra5.417 %

IOIOverall. Higher is better. No documented setup difference

Claude Fable 5.190.778 %

GPT-6 Astra100 %

Legal Research BenchOverall · All-pass. Higher is better. No documented setup difference

Claude Fable 5.155.288 %

GPT-6 Astra39.423 %

MedCodeOverall. Higher is better. No documented setup difference

Claude Fable 5.153.509 %

GPT-6 Astra48.486 %

MedScribeOverall. Higher is better. No documented setup difference

Claude Fable 5.191.294 %

GPT-6 Astra87.908 %

MysteryMechanismOverall. Higher is better. No documented setup difference

Claude Fable 5.147.748 %

GPT-6 Astra53.153 %

ProgramBenchOverall. Higher is better. No documented setup difference

Claude Fable 5.17 %

GPT-6 Astra5.5 %

ProofBenchOverall. Higher is better. No documented setup difference

Claude Fable 5.1100 %

GPT-6 Astra99 %

Key to the marks:better valuebetter, but not conclusivetie

Benchmark scores for Claude Fable 5.1 and GPT-6 Astra
Benchmark and task	Claude Fable 5.1	GPT-6 Astra	Source
Code MigrationOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is better	54.607 %	Winner67.74 %	Vals AI Source details Data as of: 09/27/2026
CyberBench v1.1Overall Test details No documented difference in the test setupVersion: 1.1Metric: accuracyScoring: Higher is better	Winner70.416 %	41.072 %	Vals AI Source details Data as of: 09/27/2026
EMBOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is better	Winner76.67 %	71.7 %	Vals AI Source details Data as of: 09/27/2026
Finance Agent (v2)Overall Test details No documented difference in the test setupVersion: 2Metric: accuracyScoring: Higher is better	Winner58.877 %	53.54 %	Vals AI Source details Data as of: 09/27/2026
Harvey's Legal Agent BenchmarkOverall · Task fully resolved Test details No documented difference in the test setupVersion: 1Metric: task resolution rateScoring: Higher is better	Winner6.667 %	5.417 %	Vals AI Source details Data as of: 09/27/2026
IOIOverall Test details No documented difference in the test setupVersion: 2Metric: accuracyScoring: Higher is better	90.778 %	Winner100 %	Vals AI Source details Data as of: 09/27/2026
Legal Research BenchOverall · All-pass Test details No documented difference in the test setupVersion: 1Metric: all-pass rateScoring: Higher is better	Winner55.288 %	39.423 %	Vals AI Source details Data as of: 09/27/2026
MedCodeOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is better	Winner53.509 %	48.486 %	Vals AI Source details Data as of: 09/26/2026
MedScribeOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is better	Winner91.294 %	87.908 %	Vals AI Source details Data as of: 09/26/2026
MysteryMechanismOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is better	47.748 %	Winner53.153 %	Vals AI Source details Data as of: 09/27/2026
ProgramBenchOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is better	Winner7 %	5.5 %	Vals AI Source details Data as of: 09/27/2026
ProofBenchOverall Test details No documented difference in the test setupVersion: 1.1Metric: accuracyScoring: Higher is better	Winner100 %	99 %	Vals AI Source details Data as of: 09/28/2026
SAGEOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is better	Winner48.526 %	46.367 %	Vals AI Source details Data as of: 09/26/2026
SRE BenchOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is better	22.901 %	Winner56.87 %	Vals AI Source details Data as of: 09/27/2026
Tax Agent BenchOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is better	Winner77.642 %	63.335 %	Vals AI Source details Data as of: 09/27/2026
Terminal-Bench 2.1Overall Test details No documented difference in the test setupVersion: 2.1Metric: accuracyScoring: Higher is better	85.019 %	Winner87.266 %	Vals AI Source details Data as of: 09/27/2026
Terminal-Bench 4.0Overall Test details No documented difference in the test setupVersion: 4.0Metric: accuracyScoring: Higher is better	49.495 %	Winner57.071 %	Vals AI Source details Data as of: 09/27/2026
Terminal-Bench ScienceOverall Test details No documented difference in the test setupVersion: 0.1Metric: accuracyScoring: Higher is better	34.286 %	Winner65.714 %	Vals AI Source details Data as of: 09/27/2026
Time Horizon Index: KSPOverall Test details No documented difference in the test setupVersion: 1Metric: progressScoring: Higher is better	63.333 %	Winner90.5 %	Vals AI Source details Data as of: 09/14/2026
Vals IndexOverall Test details No documented difference in the test setupVersion: 2Metric: weighted index scoreScoring: Higher is better	Winner68.825 %	66.608 %	Vals AI Source details Data as of: 09/27/2026
Vibe Code Bench 1-100Overall Test details No documented difference in the test setupVersion: 1.0Metric: accuracyScoring: Higher is betterSettings: Harness: OpenHands	Winner28 %	27.644 %	Vals AI Source details Data as of: 09/22/2026
Vibe Code Bench v1.1Overall Test details No documented difference in the test setupVersion: 1.1Metric: accuracyScoring: Higher is betterSettings: Harness: OpenHands	Winner90.263 %	89.594 %	Vals AI Source details Data as of: 09/27/2026
Key to the marks:better valuebetter, but not conclusivetie

Our model tests

Our tests

SVG short test

One SVG prompt and fixed output settings. Captures are shown only with 0 reported reasoning tokens or documented lack of reasoning controls. Identical test conditions do not make the models' internal compute identical.

Shared test round: 4ae5d8eeb9a9

Claude Fable 5.1

Unavailable in this round

GPT-6 Astra

Unavailable in this round

Earlier tests

Pelican on a bicycle

A community classic for free-form SVG drawing.

Claude Fable 5.1

Reasoning (requested): high

Current attempt

Run date: Sep 7, 2026
API provider: openrouter
Requested API model: anthropic/claude-fable-5.1
API model reported in response: anthropic/claude-fable-5.1
Reasoning setting: high
Pinned endpoint: Anthropic | anthropic/claude-fable-5.1-20260831
Temperature: Provider default
Token limit including reasoning: 8,192 tokens
Test protocol: community-visual-tests-v1
Technical checks: Passed, not a quality rating
Response time: 27 s

Visually reviewed. This individual test does not establish overall model quality.

GPT-6 Astra

Reasoning (requested): high

Current attempt

Run date: Sep 7, 2026
API provider: openrouter
Requested API model: openai/gpt-6-astra
API model reported in response: openai/gpt-6-astra
Reasoning setting: high
Pinned endpoint: OpenAI | openai/gpt-6-astra-20260903
Temperature: Provider default
Token limit including reasoning: 8,192 tokens
Test protocol: community-visual-tests-v1
Technical checks: Passed, not a quality rating
Response time: 141.7 s

Visually reviewed. This individual test does not establish overall model quality.

Prompt and test conditions

Generate an SVG of a pelican riding a bicycle

Token limit including reasoning: 8,192 tokens

Task origin (Simon Willison)

How to read this comparison

Winning one benchmark is not an overall verdict

Your workload, budget, and required context length matter most. A coding benchmark says little about visual understanding or agent performance.

The standard price table uses direct developer rates. The provider comparison labels OpenRouter endpoints, regions, and special tariffs separately.

Every result links to its measurement source and retrieval date. Labels distinguish vendor reports, official benchmark leaderboards, and independent evaluations. Disputed or archived results are excluded.

More matchups

Compare Claude Fable 5.1 and GPT-6 Astra with other leading models using the same data and benchmark logic.

View the complete LLM comparison

Claude Fable 5.1 vs. GPT-6 Astra

Change model selection

General specifications

API pricing compared

Shared benchmarks

Capability profile from matched benchmarks

Our tests

SVG short test

Claude Fable 5.1

GPT-6 Astra

Pelican on a bicycle

Winning one benchmark is not an overall verdict

Related LLM comparisons