Claude Fable 5.1 vs Grok 4.3.
Verdict by category, tale of the tape, shared benchmarks only, and cost at three workloads — all from the tracked data.
Verdict by category
| Category | Claude Fable 5.1 | Grok 4.3 | Winner |
|---|---|---|---|
| League Score | 97.3 | 73.7 | Claude Fable 5.1 |
| Coding (SWE-bench %) | — | — | — |
| Reasoning (GPQA %) | 93.7 | 90.1 | Claude Fable 5.1 |
| Context (tokens) | 1000000 | 1000000 | Draw |
| Speed (tok/s) | — | 151.8 | — |
| Price (blended $/1M) | $20.00 | $1.56 | Grok 4.3 (cheaper) |
Tale of the tape
| Spec | Claude Fable 5.1 | Grok 4.3 |
|---|---|---|
| Maker | Anthropic | xAI (SpaceXAI) |
| Released | Sep 1, 2026 | Apr 30, 2026 |
| League Score | 97 | 74 |
| Context | 1,000,000 tokens | 1,000,000 tokens |
| Max output | 128,000 | — |
| $/1M input | $10.00 | $1.25 |
| $/1M output | $50.00 | $2.50 |
| Weights | Closed | Closed |
| Speed | — | 151.8 t/s |
Head-to-head benchmarks (shared only)
| Benchmark | Claude Fable 5.1 | Grok 4.3 |
|---|---|---|
| GPQA Diamond | 93.7 | 90.1 |
Cost at three workloads
| Workload | Claude Fable 5.1 | Grok 4.3 |
|---|---|---|
| Light — 1M in / 250K out | $22.50 | $1.88 |
| Standard — 10M in / 2.5M out | $225.00 | $18.75 |
| Long-context — 50M in / 5M out | $750.00 | $75.00 |
The pick
Pick Claude Fable 5.1 if you want the higher overall League Score.
Pick Grok 4.3 if you want the lower running cost.
All figures from the model database — sources and dates on each model page. Cost your own workload or compare a different pair.
Frequently asked questions
Which is better overall, Claude Fable 5.1 or Grok 4.3?
Claude Fable 5.1 leads on overall League Score, 97 to 74 — a gap of 24 points on a composite of sourced benchmarks. That is overall form, not every category: check the per-category verdicts before choosing.
Which is cheaper, Claude Fable 5.1 or Grok 4.3?
Grok 4.3 is cheaper: $1.56 vs $20.00 blended per 1M tokens (3:1 input/output mix) — about 12.8x less per token.
Which has the bigger context window, Claude Fable 5.1 or Grok 4.3?
Neither — both take 1M of context.
Which is better at reasoning, Claude Fable 5.1 or Grok 4.3?
Claude Fable 5.1 leads on GPQA Diamond, 93.7% vs 90.1% on graduate-level science questions.
Are Claude Fable 5.1 and Grok 4.3 open source?
Claude Fable 5.1 is closed weights — API access only; Grok 4.3 is closed weights — API access only.