Grok 4.7 vs Claude Fable 5.1 Compared

Grok 4.7 and Claude Fable 5.1 are unusually direct competitors.

Anthropic describes Fable 5.1 as its model for demanding reasoning and long-horizon agentic work, with stronger capabilities in coding, multi-step research, documents, spreadsheets, and presentations.

xAI describes Grok 4.7 in very similar terms: coding, agentic tasks, longer-running work, self-verification, and professional knowledge work.

So instead of asking which model sounds more impressive, it is more useful to compare how they differ in context, coding, agent behavior, benchmarks, and cost.

For the full Grok specifications first, see our Grok 4.7 review.

Grok 4.7 vs Claude Fable 5.1 at a Glance

Claude Fable 5.1 has a 1M-token context window, 128K maximum output, adaptive thinking, and a June 2026 reliable knowledge cutoff. Grok 4.7 offers a 500K context window with selectable reasoning effort from Low through XHigh.

Coding Performance

Coding is central to both models.

xAI's Grok 4.7 release provides one of the clearest same-table comparisons between the two.

These numbers come from xAI's published evaluation setup. In that set, the models trade places depending on the task rather than one model leading everywhere.

There is another useful lesson here: benchmark implementations matter.

OpenAI's own evaluation of Fable 5.1 reports 55.8% on Terminal-Bench 4.0 and 67.4% on DeepSWE v1.1, slightly different from the values in xAI's table. That is why small cross-vendor benchmark differences should be interpreted carefully.

Long-Running Agent Work

Fable 5.1 is explicitly built for long-horizon agentic tasks.

Anthropic highlights stronger long-running coding, multi-step research, and professional artifact creation. Its adaptive thinking is always on, while the amount of effort can be controlled.

Grok 4.7 also targets long-running work, but xAI emphasizes slightly different improvements: longer reinforcement learning on difficult tasks, better self-verification, improved context management, and native understanding of the Grok Bot harness.

In practice, both should be tested on tasks that involve repeated tool calls, revisions, and verification—not just a single coding prompt.

Context Window

Fable 5.1 offers 1 million tokens of context.

Grok 4.7 offers 500,000 tokens.

The difference can matter for extremely large repositories, collections of research papers, long legal files, or agent sessions that accumulate a lot of tool output.

But doubling the context window does not automatically double performance.

Long-context quality also depends on whether a model retrieves the right information, notices dependencies, and maintains instructions across the workflow.

Pricing

This is where the models diverge sharply.

Grok 4.7 starts at:

$2 / 1M input tokens and $6 / 1M output tokens.

Claude Fable 5.1 costs:

$10 / 1M input tokens and $50 / 1M output tokens.

Fable's cache reads are much cheaper at $0.25 per million tokens, which Anthropic says can materially reduce costs in workloads that reuse large prompts or run highly agentic sessions.

So raw token price tells only part of the story.

If your workflow repeatedly reuses the same large context, caching behavior matters. If you process many independent requests, the base input and output rates may matter more.

Documents and Knowledge Work

Fable 5.1 has a strong focus on professional artifacts.

Anthropic specifically highlights work with documents, spreadsheets, slides, research, and coding.

Grok 4.7 also improved on document and presentation creation, while xAI reports gains on professional benchmarks covering office work, legal tasks, healthcare reasoning, and engineering.

For teams working with source-heavy material, a realistic test might include reading multiple documents, identifying conflicting evidence, drafting a report, revising it after feedback, and checking the final claims against the original files.

Which One Should You Test First?

Rather than reducing the choice to one benchmark, use the requirements of your workflow.

The practical difference can be larger or smaller than benchmark tables suggest.

If GPT-6 is also part of your evaluation, see Grok 4.7 vs GPT-6 Astra.

Final Thoughts

Grok 4.7 and Claude Fable 5.1 are aimed at many of the same high-value tasks, but they make different tradeoffs.

Fable 5.1 offers twice the context window and is explicitly designed around demanding long-horizon reasoning and agent work.

Grok 4.7 starts at a substantially lower token price and combines selectable reasoning levels with xAI's search, code execution, and agent ecosystem.

The right comparison is therefore not “Which benchmark number is bigger?”

It is whether the model completes your coding, research, or knowledge workflow accurately, consistently, and at a cost that makes sense.

If you want to test Grok directly, our how to use Grok 4.7 guide covers the main access options and settings.