Model comparison

Claude Fable 5 vs GPT-6 Astra

Anthropic against OpenAI, compared on context, price, and verified benchmark results.

Catalog record checked September 5, 2026Individual provider fields may changeEvidence confidence: High — see receipts below

Anthropic

Claude Fable 5

Frontier

OpenAI

GPT-6 Astra

Frontier

AI model capability comparison
Specification	Claude Fable 5	GPT-6 Astra
Provider	Anthropic	OpenAI
Tier	Frontier	Frontier
Context window	1M	Winner: 1.05M
Max output	128K	128K
Input / 1M tokens	$10	$10
Output / 1M tokens	$50	$50
Weights	Closed	Closed
Parameters	Not disclosedUnverified	computer-use flagship
Reasoning levels	adaptive	low, medium, high, xhigh, max
Modalities	text, image	text, image
API model id	claude-fable-5	gpt-6-astra
Released	June 9, 2026	September 3, 2026
Artificial Analysis Intelligence Index (2026-08-14)	62	Not verifiedUnverified
Artificial Analysis Intelligence Index [max] (2026-09-03)	Not verifiedUnverified	61.2
DeepSWE 1.1 (2026-09-03)	Not verifiedUnverified	74.1
OSWorld 2.0 (offline) (2026-09-03)	Not verifiedUnverified	72.6
GPQA Diamond (2026-09-03)	Not verifiedUnverified	96
Humanity's Last Exam (2026-09-03)	Not verifiedUnverified	57.2
Terminal-Bench 2.1 (2026-09-05)	Not verifiedUnverified	89.9

Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Bold indicates the better figure where one is objectively better. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.

Benchmark receipts

2026-09-05: Artificial Analysis Terminal-Bench v2.1 (independent, Terminus 2 harness — conflicts with tbench.ai 87.4; harness difference preserved)Agentic terminal work: multi-step tasks executed in a sandboxed shell environment. Comparability: comparable with caveat — Scores across Terminal-Bench major versions (v1 vs v2) are NOT comparable; harness configuration (container, time limits) also shifts results.
2026-09-03: Terminal-Bench official leaderboard (independent, native harness, high effort; captured 2026-09-03 — the live board has since moved to Terminal-Bench 4.0)Agentic terminal work: multi-step tasks executed in a sandboxed shell environment. Comparability: comparable with caveat — Scores across Terminal-Bench major versions (v1 vs v2) are NOT comparable; harness configuration (container, time limits) also shifts results.
2026-09-03: OpenAI GPT-6 Astra launch chart (vendor, with tools; transcribed by Vellum)Agentic software engineering: pass@1 on real repo tasks with reported cost per completed task. Comparability: directly comparable
2026-09-03: Artificial AnalysisComposite index blending reasoning, knowledge, and coding evals into one 0–100 score. Comparability: directly comparable — AA occasionally rebaselines the index scale between snapshots — a score captured on one date is only comparable to same-snapshot scores (check measuredAt).

Pricing tiers: Claude Fable 5: Standard $10/$50 per MTok; cache reads 10% of base input. Sibling Claude Mythos 5 is invite-only cyber-defense. Access briefly suspended 2026-06-12, redeployed 2026-07-01. · GPT-6 Astra: Standard $10/$50 per MTok (≤272K context); >272K input billed $20/$75 (Fast mode output $100). Cached input $1/MTok; Fast mode is 2x price for ~2.5x speed. Knowledge cutoff Apr 30 2026. Rolling out over several days from 2026-09-03; Enterprise tenants get it disabled by default.

FrontierRecord checked September 3, 2026

Claude Fable 5

Claude Fable 5 is Anthropic's next-generation intelligence model for long-running agents, topped LiveBench until the 5.1 refresh.

Best for

Long-running agents
Frontier reasoning
Enterprise work

Watch out

Most expensive Anthropic tier at $10/$50; verify the cost is justified by the task.

FrontierRecord checked September 5, 2026

GPT-6 Astra

GPT-6 Astra is OpenAI's computer-use flagship — the first model it gates at the Preparedness Framework's 'Critical' cybersecurity threshold, trained on >100,000 GPUs at Stargate.

Best for

Computer-use agents
Agentic coding
Hard reasoning

Watch out

Gated at the 'Critical' cyber threshold and disabled by default for Enterprise; long-context work bills $20/$75 above 272K input tokens.

When the cheaper one wins

Both charge $50 per million output tokens at standard rates, so output price is not the split. Prefer the row whose “best for” line matches the job, then confirm the live vendor rate.

Run the model picker

Evidence confidence: High

How strong and complete the evidence behind this comparison is — not a prediction of which model is better.

Pricing verified on both sides — Input and output rates are verified for both models.
4/5 core specs verified on both sides — Not published for at least one side: parameter count.
1 shared named benchmark (scores match) — Measured on: Artificial Analysis Intelligence Index — scores are equivalent, so the benchmark does not separate the pair.
Verified within the last 90 days — Newest catalog check was 6 days ago.
Both models carry source citations — Each side has at least two catalog sources on record.

Source receipts

Each catalog figure was checked against the provider or an independent second source on the date shown.

Claude Fable 5: Anthropic — Claude Fable 5 (accessed 2026-08-29)
Claude Fable 5: Anthropic news — Claude Fable 5 (accessed 2026-08-29)
GPT-6 Astra: OpenAI — Introducing GPT-6 Astra (accessed 2026-09-03)
GPT-6 Astra: OpenAI API pricing (gpt-6-astra $10/$50) (accessed 2026-09-03)
GPT-6 Astra: CNBC — OpenAI launches GPT-6 Astra (accessed 2026-09-03)
GPT-6 Astra: OpenAI model docs — gpt-6-astra (128K max output, effort levels) (accessed 2026-09-05)

Related comparisons

Diving deeper on one model? Claude Fable 5 · GPT-6 Astra

Common questions

Claude Fable 5 vs GPT-6 Astra

Answered from the verified figures on this page rather than general guidance.

Is Claude Fable 5 or GPT-6 Astra cheaper for input?

Both cost $10 per million input tokens at standard rates, so input price is not a deciding factor between them.

Is Claude Fable 5 or GPT-6 Astra cheaper for output?

Both cost $50 per million output tokens at standard rates, so output price is not a deciding factor between them.

Which has the larger context window, Claude Fable 5 or GPT-6 Astra?

GPT-6 Astra accepts 1.05M tokens against 1M for Claude Fable 5. This only matters if you routinely send very long documents or large codebases.

Do Claude Fable 5 and GPT-6 Astra support the same reasoning levels?

Claude Fable 5 exposes adaptive, while GPT-6 Astra exposes low, medium, high, xhigh, max.

Should I use Claude Fable 5 or GPT-6 Astra?

Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. Claude Fable 5 suits long-running agents; GPT-6 Astra suits computer-use agents.

Next step

Choosing between them

The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.

Context: GPT-6 Astra takes 1.05M against 1M for Claude Fable 5 — only decisive if your prompts approach the smaller window.

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