Model comparison
Claude Fable 5.1 vs GPT-5.6 Sol
Anthropic against OpenAI, compared on context, price, and verified benchmark results.
Catalog record checked September 3, 2026Individual provider fields may changeEvidence confidence: High — see receipts below
Anthropic
Claude Fable 5.1
Frontier
OpenAI
GPT-5.6 Sol
Frontier
| Specification | Claude Fable 5.1 | GPT-5.6 Sol |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Tier | Frontier | Frontier |
| Context window | 1M | Winner: 1.05M |
| Max output | 128K | 128K |
| Input / 1M tokens | $10 | Winner: $4 |
| Output / 1M tokens | $50 | Winner: $20 |
| Weights | Closed | Closed |
| Parameters | Not disclosedUnverified | flagship reasoning + coding model |
| Reasoning levels | adaptive | none, low, medium, high, xhigh, max |
| Modalities | text, image | text, image |
| API model id | claude-fable-5-1 | gpt-5.6-sol |
| Released | September 1, 2026 | July 9, 2026 |
| Artificial Analysis Intelligence Index (2026-08-14) | 66 | Not verifiedUnverified |
| Artificial Analysis Intelligence Index [max] (2026-08-14) | Not verifiedUnverified | 61 |
| Humanity's Last Exam (2026-09-01) | 65 | Not verifiedUnverified |
| Terminal-Bench 2.1 (2026-09-05) | Winner: 91.4 | 88.8 |
| DeepSWE 1.1 (2026-09-03) | 67.4 | Not verifiedUnverified |
| GPQA Diamond (2026-07-09) | Not verifiedUnverified | 94.6 |
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).
- 2026-07-09: OpenAI — GPT-5.6 evals table (vendor)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.
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. · GPT-5.6 Sol: Launch list was $5/$30; cut to $4/$20 on 2026-08-21, promo held at least through 2026-11-21. Cached input $0.40/MTok; batch $2/$10. Knowledge cutoff Feb 16 2026.
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.
GPT-5.6 Sol
OpenAI's GPT-5.6 flagship for complex reasoning and coding with a 1.05M-token context — top-tier but no longer the agentic-coding leader on the tracked boards.
Best for
- Complex reasoning
- Agentic coding
- Hard knowledge work
Watch out
At $4/$20 per MTok it is the priciest GPT-5.6 tier; 'max' effort and 'ultra' multi-agent mode multiply token use.
When the cheaper one wins
GPT-5.6 Sol is cheaper on output at $20 per million tokens against $50 for Claude Fable 5.1 — about 2.5×. 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 pickerEvidence 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.
- 2 shared named benchmarks with differing scores — Measured on: Artificial Analysis Intelligence Index, Terminal-Bench 2.1.
- 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)
- GPT-5.6 Sol: OpenAI — GPT-5.6 (accessed 2026-08-29)
- GPT-5.6 Sol: OpenAI API pricing (gpt-5.6-sol $4/$20) (accessed 2026-08-29)
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Diving deeper on one model? Claude Fable 5.1 · GPT-5.6 Sol
Common questions
Claude Fable 5.1 vs GPT-5.6 Sol
Answered from the verified figures on this page rather than general guidance.
Is Claude Fable 5.1 or GPT-5.6 Sol cheaper for input?
GPT-5.6 Sol is cheaper at $4 per million input tokens, against $10 for Claude Fable 5.1 — roughly 2.5× 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. GPT-5.6 Sol has tiered pricing: Launch list was $5/$30; cut to $4/$20 on 2026-08-21, promo held at least through 2026-11-21. Cached input $0.40/MTok; batch $2/$10. Knowledge cutoff Feb 16 2026.
Is Claude Fable 5.1 or GPT-5.6 Sol cheaper for output?
GPT-5.6 Sol is cheaper at $20 per million output tokens, against $50 for Claude Fable 5.1 — roughly 2.5× 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. GPT-5.6 Sol has tiered pricing: Launch list was $5/$30; cut to $4/$20 on 2026-08-21, promo held at least through 2026-11-21. Cached input $0.40/MTok; batch $2/$10. Knowledge cutoff Feb 16 2026.
Which has the larger context window, Claude Fable 5.1 or GPT-5.6 Sol?
GPT-5.6 Sol accepts 1.05M tokens against 1M for Claude Fable 5.1. This only matters if you routinely send very long documents or large codebases.
Do Claude Fable 5.1 and GPT-5.6 Sol support the same reasoning levels?
Claude Fable 5.1 exposes adaptive, while GPT-5.6 Sol exposes none, low, medium, high, xhigh, max.
Should I use Claude Fable 5.1 or GPT-5.6 Sol?
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; GPT-5.6 Sol suits complex reasoning.
Next step
Choosing between them
The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.
- Input price: GPT-5.6 Sol costs $4 per 1M tokens versus $10 for Claude Fable 5.1 — a 2.5x difference at the headline tier.
- Context: GPT-5.6 Sol takes 1.05M against 1M for Claude Fable 5.1 — only decisive if your prompts approach the smaller window.
- Measured capability: Claude Fable 5.1 leads Artificial Analysis Intelligence Index 66 to 61 (measured 2026-08-14).
Choosing a harness rather than a model — Cursor, Copilot, Claude Code, Windsurf, or Lovable? Compare agentic harnesses · Latest releases.