Grok 4.6 (SpaceXAI, August 12, 2026) and Claude Fable 5 (Anthropic, June 9, 2026) sit at opposite ends of the frontier-model spectrum. Grok 4.6 is the value play — frontier intelligence at $2/$6 per million tokens. Fable 5 is the premium specialist — Anthropic's first Mythos-class model, built for long-horizon autonomous work at $10/$50.
This guide compares the two across benchmarks, pricing, speed, latency, and context. Figures are drawn from xAI's launch table, Anthropic's documentation, Artificial Analysis, and independent reviews.
At a Glance
| Category | Grok 4.6 | Claude Fable 5 |
|---|---|---|
| Release date | August 12, 2026 | June 9, 2026 |
| Developer | SpaceXAI | Anthropic |
| Model class | Frontier (post-training refresh) | Mythos-class (above Opus) |
| Context window | 500,000 tokens | 1,000,000 tokens |
| Max output | — | 128,000 tokens |
| Input price | $2 / 1M | $10 / 1M |
| Output price | $6 / 1M | $50 / 1M |
| Prompt caching | $0.50 / 1M cached | 90% input discount |
| Reasoning | Low, medium, high, xhigh | Adaptive thinking (always on) |
| Model ID | grok-4.6 | claude-fable-5 |
Benchmark Comparison
Here is the head-to-head from xAI's official Grok 4.6 launch table (comparing each model's highest reasoning setting). Fable 5 leads the overall index and most coding-agent rows; Grok wins the professional knowledge-work evaluations.
| Evaluation | Grok 4.6 High | Fable 5 Max | Leader |
|---|---|---|---|
| AA Intelligence Index | 61 | 62 | Fable 5 |
| GDPVal-AA v2 | 1753 | 1741 | Grok 4.6 |
| CursorBench v3.2 | 69.9% | 70.5% | Fable 5 |
| DeepSWE v1.1 | 65.9% | 70.0% | Fable 5 |
| FrontierCode v1.1 (Ext) | 61.3% | 63.6% | Fable 5 |
| APEX-Agents | 57.5% | 59.2% | Fable 5 |
| Terminal-Bench v3.0 | 26.0% | 34.1% | Fable 5 |
| APEX-SWE | 56.4% | 58.8% | Fable 5 |
| AA-Briefcase | 1577 | 1574 | Grok 4.6 |
| Harvey LAB (Vals) | 15.8% | 11.3% | Grok 4.6 |
Source: xAI "Introducing Grok 4.6" (Aug 12, 2026). Vendor-reported; third-party scores are the best of self-reported or publicly available results.
Benchmark Head-to-Head
Fable 5's leads are consistent but modest on most coding rows (0.6–2.3 points), with a larger gap on Terminal-Bench (8.1 points) and DeepSWE (4.1 points). Grok's wins are concentrated in professional knowledge work — GDPVal-AA, AA-Briefcase, and a notably large Harvey LAB lead (15.8% vs 11.3%).
Capability Radar
Radar values are normalized (0–100) from the benchmark table for visual comparison only.
Pricing: The Deciding Factor
This is where the two models diverge most sharply. Fable 5 is 5× more expensive on input and 8.3× on output:
| Cost component | Grok 4.6 | Claude Fable 5 |
|---|---|---|
| Input (per 1M) | $2 | $10 |
| Output (per 1M) | $6 | $50 |
| Cached input | $0.50 | $1 (90% off $10) |
| Long-context band | 2× above 200K | Flat 1M price |
Consider a hypothetical agent task using 1M input + 250K output tokens:
At headline rates, that task costs roughly $3.50 on Grok 4.6 vs. $22.50 on Fable 5 — a 6.4× difference. Fable 5's premium is only rational if it succeeds where Grok needs several retries, or if its token efficiency (fewer turns, fewer tool calls) closes the gap. Anthropic reports Fable 5 finishes complex tasks in fewer turns, which can offset the sticker price on the right workloads.
Speed & Latency
Both models are "thinking" models with significant time-to-first-token. But Fable 5's always-on adaptive thinking makes it dramatically slower to start:
| Metric (Artificial Analysis) | Grok 4.6 (high) | Fable 5 (max effort) |
|---|---|---|
| Output speed | 85.8 t/s | ~63–68 t/s |
| Time to first token | 32.3 s | ~109–137 s |
Grok 4.6 is faster on both axes. It generates ~85.8 tokens/second versus Fable 5's ~63–68, and starts answering in ~32 seconds versus Fable 5's ~109–137 seconds at max effort. Fable 5's latency is dominated by "thinking" time, which scales with the effort setting — lower-effort requests start substantially faster, but thinking cannot be disabled entirely.
Context Window: Fable 5 Doubles Grok
Fable 5 ships a 1,000,000-token context window (with 128K max output) — double Grok 4.6's 500K. For very long documents, large monorepos, or multi-hour agent sessions, Fable 5 holds more working context in a single pass. Grok 4.6's 500K is still generous, but it's a clear spec disadvantage for the longest-horizon work.
Verdict: Which Should You Choose?
The smartest setup for many teams is a router: use Grok 4.6 as the default value lane for routine coding, research, and office-style workflows, and escalate the hardest long-horizon engineering tasks to Fable 5. Run the same 20–50 tasks through both with an identical harness, and measure completion rate, total tokens, and human review time — not just benchmark prestige.