Grok 4.3 vs Claude Fable 5.1
Compare Grok 4.3 and Claude Fable 5.1 side-by-side. See comparisons of price, response speed, accuracy, and file support to choose the best model for your task.
Overview
Grok 4.3 vs Claude Fable 5.1 Overview
Everything you need to know about these AI models, including capabilities, performance, pricing, and technical details.
xAI / Grok 4.3
proDescription
xAI's previous flagship, and still the Grok model with the largest context window. Grok 4.3 holds a million tokens, double what the newer generation offers. xAI positions it around a low hallucination rate, agentic tool calling, and instruction following. It reads text and images, searches the web and X, and lets you turn reasoning off entirely when speed matters more than depth.
Anthropic / Claude Fable 5.1
maxDescription
Anthropic's most capable generally available model, sitting above the Opus line. Fable 5.1 is built for long, unsupervised work: multi-day coding, agentic research, and tasks that run across dozens of tool calls. It reads text and images, maintains a very large context, and reasons before every answer at an adjustable depth. Its knowledge is the most recent of any Claude model. Anthropic positions Opus 5 as the starting point for most work, and Fable 5.1 for teams whose evaluations demand a higher ceiling.
About
About
Capabilities
Capabilities
Comparison
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xAI / Grok 4.3
proAgentic Coding and Tool Calling
xAI positions this model on agentic tool-calling and instruction-following, which is what coding agents actually run on. Function calling and structured outputs are both supported natively.
Reasoning You Can Switch Off
Effort runs at none, low, medium, or high. None means no reasoning at all, so you can drop it entirely for simple work and pay only for the answer rather than the thinking.
Large Context Window
Handles a one million tokens, twice the window of the newer Grok generation. Load an entire repository or a large document set in one pass. Requests above 200,000 tokens are billed at a higher rate.
Low Hallucination
xAI leads its own description with non-hallucination rate and instruction-following, which matter most for writing that has to be accurate and stay within the brief you gave it.
Web Search and X Search
xAI states that Grok knows nothing beyond its training data and provides server-side Web Search and X Search tools to bridge the gap. X Search reaches posts and threads no other model can read.
Text and Image Input
xAI lists modalities as text and image in, text out. Send screenshots, diagrams, or scanned pages alongside your prompt. Audio and video are not listed as accepted inputs.
Anthropic / Claude Fable 5.1
maxLong-Running Coding
Anthropic's strongest model for multi-day coding sessions and codebase research. Built to sustain complex software engineering across many steps and tool calls without a human checking in at each one.
Adaptive Thinking Always On
Reasoning is always on, with adjustable effort rather than an on-off switch. Steer depth up for the hardest problems or down for lighter work, without restructuring the prompt each time.
Room For Whole Projects
A very large context window, among the largest available. Load an entire codebase, a long research corpus, or a large document set and work across all of it in a single session.
Document-Heavy Analysis
Built for document-heavy analysis and multi-step automation alongside coding. Suited to work that reads across large, mixed source material and produces structured, reviewable output.
Long-Horizon Agent Work
Its defining strength. Retains context, uses tools, evaluates results, and works on a task through many steps. Built for agents who run for a long time with little supervision.
Text And Image Input
Reads text and images in the same prompt, so you can send screenshots, diagrams, or scanned pages alongside your question. Output is text only. Audio and video are not accepted.
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