Model comparison
Claude Fable 5.1 vs Muse Spark 1.2
Anthropic against Meta, compared on context, price, and verified benchmark results.
Catalog record checked September 3, 2026Individual provider fields may changeEvidence confidence: Insufficient data — see receipts below
Anthropic
Claude Fable 5.1
Frontier
Meta
Muse Spark 1.2
Frontier
| Specification | Claude Fable 5.1 | Muse Spark 1.2 |
|---|---|---|
| Provider | Anthropic | Meta |
| Tier | Frontier | Frontier |
| Context window | 1M | 1M |
| Max output | 128K | Not verifiedUnverified |
| Input / 1M tokens | $10 | Not verifiedUnverified |
| Output / 1M tokens | $50 | Not verifiedUnverified |
| Weights | Closed | Closed |
| Parameters | Not disclosedUnverified | Meta frontier model |
| Reasoning levels | adaptive | low, medium, high |
| Modalities | text, image | text, image |
| API model id | claude-fable-5-1 | muse-spark-1.2 |
| Released | September 1, 2026 | August 5, 2026 |
| Artificial Analysis Intelligence Index (2026-08-14) | Winner: 66 | 57 |
| Humanity's Last Exam (2026-09-01) | 65 | Not verifiedUnverified |
| Terminal-Bench 2.1 (2026-09-05) | 91.4 | Not verifiedUnverified |
| DeepSWE 1.1 (2026-09-03) | 67.4 | Not verifiedUnverified |
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, max effort — current AA leader)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 (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. Comparability: directly comparable
- 2026-09-01: Anthropic announcement comparison table (vendor, with tools; 60.9 no tools)Frontier-knowledge ceiling: extremely hard multi-domain questions written to be near-impossible without deep expertise. Comparability: comparable with caveat — Subset/tool configurations (text-only vs with-tools) differ between vendors and materially change scores; must match configuration to compare.
- 2026-08-14: 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 5.1: 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. · Muse Spark 1.2: Closed-weights; served via Meta's Model API. Not open-weight.
Claude Fable 5.1
Claude Fable 5.1 is Anthropic's September 2026 flagship refresh, debuting at the top of LiveBench and the Artificial Analysis Intelligence Index.
Best for
- Frontier agents
- Hardest reasoning work
- Fable 5 workloads at the same price
Watch out
Early-life model: leaderboard position is from launch-week boards; recheck before committing spend.
Muse Spark 1.2
Muse Spark 1.2 is Meta's closed frontier model until the 1.3 refresh (2026-09-02) — still served and ranked in the LMArena text top 10 as of mid-2026.
Best for
- Frontier reasoning
- Meta ecosystem
- Agentic work
Watch out
Closed-weights (unlike Llama 4); Meta's post-Llama-4 frontier branding.
When the cheaper one wins
One of these rows is missing a verified output price, so this page will not name a cheaper winner. Run the model picker against the actual job instead of guessing.
Run the model pickerEvidence confidence: Insufficient data
How strong and complete the evidence behind this comparison is — not a prediction of which model is better. Hard limitations apply: missing pricing.
- Pricing incomplete — No verified token pricing for Muse Spark 1.2.
- 3/5 core specs verified on both sides — Not published for at least one side: max output, parameter count.
- 1 shared named benchmark with differing scores — Measured on: Artificial Analysis Intelligence Index.
- Verified within the last 90 days — Newest catalog check was 8 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: Artificial Analysis — Fable 5.1 Intelligence Index 66 #1 (accessed 2026-09-01)
- Muse Spark 1.2: Meta — Muse (accessed 2026-08-29)
- Muse Spark 1.2: Muse version tracking (accessed 2026-08-29)
Related comparisons
- Claude Fable 5.1 vs Claude Haiku 4.5
- Claude Fable 5.1 vs Claude Mythos 5.1
- Claude Fable 5.1 vs Claude Opus 5
- Claude Fable 5.1 vs Claude Sonnet 5
- Claude Fable 5.1 vs DeepSeek V4 Pro
- Claude Fable 5.1 vs Gemini 3.1 Pro
Diving deeper on one model? Claude Fable 5.1 · Muse Spark 1.2
Common questions
Claude Fable 5.1 vs Muse Spark 1.2
Answered from the verified figures on this page rather than general guidance.
Which has the larger context window, Claude Fable 5.1 or Muse Spark 1.2?
Both accept about 1M tokens of context, so document length will not decide between them.
Do Claude Fable 5.1 and Muse Spark 1.2 support the same reasoning levels?
Claude Fable 5.1 exposes adaptive, while Muse Spark 1.2 exposes low, medium, high.
Should I use Claude Fable 5.1 or Muse Spark 1.2?
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; Muse Spark 1.2 suits frontier reasoning.
Next step
Choosing between them
The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.
- Measured capability: Claude Fable 5.1 leads Artificial Analysis Intelligence Index 66 to 57 (measured 2026-08-14).
Choosing a harness rather than a model — Cursor, Copilot, Claude Code, Windsurf, or Lovable? Compare agentic harnesses · Latest releases.