Grok 4.6 is now competing with Claude Fable 5-level models at a fraction of the price
SpaceXAI's new Grok 4.6 appears to have closed a surprising amount of the gap with the best frontier models, particularly on long-running agents and real-world knowledge work.
Artificial Analysis gives Grok 4.6 a score of 61 on its Intelligence Index.
For comparison:
- Claude Opus 5 Max: 63
- Claude Fable 5 Max with fallback: 62
- Grok 4.6: 61
- GPT-5.6 Sol Max: 61
That puts Grok effectively alongside GPT-5.6 Sol and only slightly behind Anthropic's current leaders on the aggregate benchmark.
But the more interesting results are on agentic work.
On AA-Briefcase, Artificial Analysis's private benchmark for long-horizon knowledge work, Grok 4.6 scored an Elo of 1577, which Artificial Analysis describes as Fable 5-tier performance.
It still sits behind the Claude Opus 5 family, but Grok's efficiency is notable.
Artificial Analysis says Grok 4.6 completed these long-running tasks in roughly:
- 53 turns
- Around 0.5 billion input tokens
Claude Opus 5 Max averaged roughly:
- 103 turns
- Around 2 billion input tokens
So Grok was reaching comparable high-end results using roughly half as many turns and around a quarter of the input tokens in this evaluation.
Other agent benchmarks were strong too:
- GDPval-AA v2: 1753 Elo
- τ³-Banking: 50.7%
- Terminal-Bench v2.1: 88.4%
Its GDPval-AA result sits behind only Claude Opus 5, while its confidence interval overlaps with Claude Fable 5 and Qwen3.8 Max.
And then there's the price.
Grok 4.6 costs:
- $2 / 1M input tokens
- $6 / 1M output tokens
- $0.50 / 1M cached input tokens
Artificial Analysis measured its average cost at roughly $0.84 per Intelligence Index task.
Compare that with:
- Claude Opus 5: $5 input / $25 output
- GPT-5.6 Sol: $5 input / $30 output
Artificial Analysis says Grok 4.6 is more than 60% cheaper at headline pricing than those frontier competitors while delivering similar aggregate intelligence to GPT-5.6 Sol.
That price gap becomes much more important with agents.
A chatbot might generate a few thousand tokens.
An autonomous coding or research agent can make dozens of tool calls, repeatedly read large codebases or documents, revise its work, and accumulate millions of tokens during a single task.
At that scale, being slightly cheaper isn't a minor advantage.
It can completely change the economics of running agents continuously.
There are already some interesting real-world examples.
David Heinemeier Hansson reported giving Grok 4.6 a plan originally created by Fable and said that, with only a couple of nudges, Grok was able to reproduce the result in 1 hour and 24 minutes using 8.6 million tokens.
That's obviously one anecdotal test rather than a benchmark, but it points toward the same thing the agent evaluations are showing: Grok's biggest improvement may not be answering individual prompts better—it may be its ability to stay useful across much longer workflows.
SpaceXAI says Grok 4.6 was specifically trained for long-running agents, coding, knowledge work, and more complex tasks.
It also keeps the 500K context window from Grok 4.5.
Grok 4.6 is available through Grok Build, Cursor, Grok Bot, and the SpaceXAI API, with SpaceXAI offering 2× usage in Cursor and Grok Build during the first week.
This is probably why the comparison with Fable is starting to become more interesting.
Anthropic still appears to have the overall lead at the very top, particularly with Opus 5.
But the gap between "best model" and "good enough to do the same job" may matter more economically than a one- or two-point benchmark difference.
If Grok can deliver something close to Fable-level agent performance while costing dramatically less, developers running thousands of long agent tasks may prefer the cheaper model even if Claude remains somewhat stronger.
That could be where the next phase of the model race gets interesting.
The competition isn't only:
Which model is smartest?
It's increasingly:
How much useful autonomous work can I get for every dollar?
And on that metric, Grok 4.6 suddenly looks much more competitive.
If Grok 4.6 is genuinely close to Fable 5 for long-running agent work at this price, would you switch from Claude—or is reliability still worth paying the Anthropic premium for?
Sources:
Wes Roth — Grok 4.6 is Fable now
SpaceXAI — Introducing Grok 4.6
Artificial Analysis — Grok 4.6 benchmarks and analysis
Posted Aug 14, 2026, 12:36 AM UTC