Model comparison

Claude Fable 5.1 vs Grok 4.7

Q: Is Claude Fable 5.1 or Grok 4.7 cheaper for input?

Grok 4.7 is cheaper at $2 per million input tokens, against $10 for Claude Fable 5.1 — roughly 5.0× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; Claude Fable 5.1 has tiered pricing: Priced with Fable 5 at $10/$50 per MTok; cache reads cut 75% to $0.25/MTok. Adaptive thinking always on (default effort high); knowledge cutoff Jun 2026. Sibling Mythos 5.1 launched the same day. Grok 4.7 has tiered pricing: $2/$6 per MTok (<200K prompt); $4/$12 for all tokens at ≥200K. Cached input $0.50/MTok ($1.00 at ≥200K). US regional endpoint 1.1x. No Batch API; the 2x-price 'Fast' variant is Cursor and Grok Build only. xAI lists no separate text-output cap. Knowledge cutoff May 2026.

Q: Is Claude Fable 5.1 or Grok 4.7 cheaper for output?

Grok 4.7 is cheaper at $6 per million output tokens, against $50 for Claude Fable 5.1 — roughly 8.3× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; Claude Fable 5.1 has tiered pricing: Priced with Fable 5 at $10/$50 per MTok; cache reads cut 75% to $0.25/MTok. Adaptive thinking always on (default effort high); knowledge cutoff Jun 2026. Sibling Mythos 5.1 launched the same day. Grok 4.7 has tiered pricing: $2/$6 per MTok (<200K prompt); $4/$12 for all tokens at ≥200K. Cached input $0.50/MTok ($1.00 at ≥200K). US regional endpoint 1.1x. No Batch API; the 2x-price 'Fast' variant is Cursor and Grok Build only. xAI lists no separate text-output cap. Knowledge cutoff May 2026.

Q: Which has the larger context window, Claude Fable 5.1 or Grok 4.7?

Claude Fable 5.1 accepts 1M tokens against 500K for Grok 4.7. This only matters if you routinely send very long documents or large codebases.

Q: Do Claude Fable 5.1 and Grok 4.7 support the same reasoning levels?

Claude Fable 5.1 exposes adaptive, while Grok 4.7 exposes low, medium, high, xhigh.

Q: Should I use Claude Fable 5.1 or Grok 4.7?

Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. Claude Fable 5.1 suits frontier agents; Grok 4.7 suits coding agents.

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

Catalog record checked September 26, 2026Individual provider fields may changeEvidence confidence: High — see receipts below

Anthropic

Claude Fable 5.1

Frontier

SpaceXAI

Grok 4.7

Frontier

AI model capability comparison
Specification	Claude Fable 5.1	Grok 4.7
Provider
Provider	Anthropic	SpaceXAI
Tier
Tier	Frontier	Frontier
Context window
Context window	Winner: 1M	500K
Max output
Max output	128K	Not verifiedUnverified
Input / 1M tokens
Input / 1M tokens	$10	Winner: $2
Output / 1M tokens
Output / 1M tokens	$50	Winner: $6
Weights
Weights	Closed	Closed
Parameters
Parameters	Not disclosedUnverified	new, larger base model with longer RL on multi-hour tasks
Reasoning levels
Reasoning levels	adaptive	low, medium, high, xhigh
Modalities
Modalities	text, image	text, image
API model id
API model id	claude-fable-5-1	grok-4.7
Released
Released	September 1, 2026	September 21, 2026
Artificial Analysis Intelligence Index [max] (2026-09-26)
Artificial Analysis Intelligence Index [max] (2026-09-26)	53.4	Not verifiedUnverified
Artificial Analysis Intelligence Index [xhigh] (2026-09-26)
Artificial Analysis Intelligence Index [xhigh] (2026-09-26)	Not verifiedUnverified	46.4
Humanity's Last Exam (2026-09-01)
Humanity's Last Exam (2026-09-01)	65	Not verifiedUnverified
Terminal-Bench 2.1 (2026-09-26)
Terminal-Bench 2.1 (2026-09-26)	91.4	Not verifiedUnverified
Terminal-Bench 4.0 [max] (2026-09-26)
Terminal-Bench 4.0 [max] (2026-09-26)	52	Not verifiedUnverified
Terminal-Bench 4.0 [xhigh] (2026-09-26)
Terminal-Bench 4.0 [xhigh] (2026-09-26)	Not verifiedUnverified	25.8
DeepSWE 1.1 (2026-09-03)
DeepSWE 1.1 (2026-09-03)	67.4	Not verifiedUnverified
DeepSWE 1.1 [high] (2026-09-21)
DeepSWE 1.1 [high] (2026-09-21)	Not verifiedUnverified	71

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

Where each score comes from, and how far it can be compared across models.

2026-09-26
Artificial Analysis Terminal-Bench 4.0 (independent AA run, part of Intelligence Index v4.3.2)
Agentic terminal work: long multi-step tasks executed in a sandboxed shell environment.
Comparable with caveatNOT comparable with Terminal-Bench 2.x or 3.0 — 4.0 uses a new, non-overlapping task set. Within 4.0, scores from different harnesses (tbench.ai agent entries vs Artificial Analysis runs) are not interchangeable.
2026-09-26
Artificial Analysis Terminal-Bench 2.1 (independent, Terminus 2, max effort)
Agentic terminal work: multi-step tasks executed in a sandboxed shell environment.
Comparable with caveatNot comparable with Terminal-Bench 3.0 or 4.0 (different task sets) or v1; harness configuration (container, time limits) also shifts results.
2026-09-26
Artificial Analysis
Composite index blending reasoning, knowledge, and coding evals into one 0–100 score.
Comparable with caveatOnly same-version scores are comparable. v4.3.2 was rebaselined (the top score fell from 66 on v4.1.1 to ~58), so v4.1.1 figures must not be compared with v4.3.2 figures — check measuredAt.
2026-09-21
xAI — Grok 4.7 announcement (vendor; not yet on Datacurve's board)
Agentic software engineering: pass@1 on real repo tasks with reported cost per completed task.
Directly comparable
2026-09-03
OpenAI GPT-6 Astra launch chart (independent cross-vendor; Fable 5.1 not on the official Datacurve leaderboard)
Agentic software engineering: pass@1 on real repo tasks with reported cost per completed task.
Directly comparable
2026-09-01
Anthropic Fable 5.1 announcement (vendor, with tools; 60.9 no tools) — Anthropic's later Opus 5.5 table lists 65.6; conflict preserved
Frontier-knowledge ceiling: extremely hard multi-domain questions written to be near-impossible without deep expertise.
Comparable with caveatSubset/tool configurations (text-only vs with-tools) differ between vendors and materially change scores; must match configuration to compare.

Pricing tiers

Claude Fable 5.1: Priced with Fable 5 at $10/$50 per MTok; cache reads cut 75% to $0.25/MTok. Adaptive thinking always on (default effort high); knowledge cutoff Jun 2026. Sibling Mythos 5.1 launched the same day.

Grok 4.7: $2/$6 per MTok (<200K prompt); $4/$12 for all tokens at ≥200K. Cached input $0.50/MTok ($1.00 at ≥200K). US regional endpoint 1.1x. No Batch API; the 2x-price 'Fast' variant is Cursor and Grok Build only. xAI lists no separate text-output cap. Knowledge cutoff May 2026.

FrontierRecord checked September 26, 2026

Claude Fable 5.1

Claude Fable 5.1 is Anthropic's model for the most demanding reasoning and long-horizon agentic work at $10/$50 — Anthropic now recommends Opus 5.5 as the default for most workloads.

Best for

Frontier agents
Hardest reasoning work
Fable 5 workloads at the same price

Watch out

Costs 2.5x Opus 5.5 per token and trails it on the Artificial Analysis Intelligence Index (53.4 vs 57.6, v4.3.2); reserve it for the hardest long-horizon work.

FrontierRecord checked September 26, 2026

Grok 4.7

Grok 4.7 is xAI's flagship since 2026-09-21 — a larger new base model with longer RL on multi-hour tasks, at Grok 4.6's $2/$6 price.

Best for

Coding agents
Cost-sensitive frontier work
Cursor and GitHub Copilot users

Watch out

Token rates double above a 200K-token prompt and there is no Batch API; the DeepSWE figure is vendor-reported.

When the cheaper one wins

Grok 4.7 is cheaper on output at $6 per million tokens against $50 for Claude Fable 5.1 — about 8.3×. Use the cheaper tier for classification, extraction, summarisation, and any task where the expensive model’s extra score does not change the accepted output. The expensive one only pays if your hardest task actually fails on the cheap tier. These are standard-tier API rates, excluding batch and cache discounts.

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.
3/5 core specs verified on both sides — Not published for at least one side: max output, parameter count.
3 shared named benchmarks with differing scores — Measured on: Artificial Analysis Intelligence Index, Terminal-Bench 4.0, DeepSWE 1.1.
Verified within the last 90 days — Newest catalog check was 2 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 5.1: Anthropic pricing — Fable 5.1/Mythos 5.1 $10/$50 (accessed 2026-09-03)
Claude Fable 5.1: Anthropic models overview — Fable 5.1 (1M context, 128K output) (accessed 2026-09-03)
Claude Fable 5.1: Anthropic — Claude Fable and Mythos 5.1 announcement (accessed 2026-09-26)
Claude Fable 5.1: Anthropic models overview — Opus 5.5 default; Fable 5.1 for demanding reasoning (accessed 2026-09-26)
Grok 4.7: xAI — Grok 4.7 (accessed 2026-09-26)
Grok 4.7: xAI docs — grok-4.7 model card (accessed 2026-09-26)
Grok 4.7: xAI pricing (grok-4.7 $2/$6, ≥200K $4/$12) (accessed 2026-09-26)
Grok 4.7: GitHub changelog — Grok 4.7 in Copilot (2026-09-21) (accessed 2026-09-26)

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Diving deeper on one model? Claude Fable 5.1 · Grok 4.7

Common questions