Grok Build 0.1: xAI's Agentic Coding Model Explained

xAI released Grok Build 0.1 on May 20, 2026, and it is a different animal from the Grok you argue with on X. This is the company's first model purpose-built for agentic coding: instead of answering programming questions, it is trained to act as an autonomous engineering agent — refactoring codebases, invoking tools, generating structured output, and looping until the task is done. It carries a 256,000-token context window, accepts text and images, and costs half of what Grok 4.5 does. This guide covers what the model actually is, what it costs, and when it beats its bigger sibling.

What Is Grok Build 0.1?

Grok Build 0.1 is xAI's fastest coding model, trained specifically for agentic software engineering workflows. Per xAI's announcement, it is optimized for interactive coding: the tight loop of reading a repository, proposing an edit, running a tool, reading the result, and going again. It natively supports tool invocation and reasoning chains — capabilities the conversational Grok models are not optimized for.

The "0.1" in the name is honest versioning: this is the first release in a new product line, shipped quietly during a month when xAI also rolled out a skills system and a connectors layer (GitHub, Linear, Notion, Vercel, and more). The model reached SuperGrok and X Premium+ subscribers through IDE integrations in late May, with API access following in public beta. On CoreAI, it slots in as a standard-tier model with reasoning support.

Grok Build 0.1 Specs and Pricing

Here is how it lines up against the other coding-focused models in its weight class, with live per-token pricing:

Two pricing details worth knowing. First, output is unusually cheap: $2.00 per million output tokens is a third of Grok 4.5's rate, and coding agents are output-heavy — they write a lot of diffs. Second, there is a long-context surcharge: above 200,000 prompt tokens, rates double to $2.00 input and $4.00 output. If your agent routinely stuffs the full window, budget for the higher tier or trim your context.

How Is Grok Build Different From Grok 4.5?

Grok 4.5 is xAI's frontier generalist — 500K context, strong across coding, knowledge work, and STEM, and the model we covered in depth in our Grok 4.5 guide. Build 0.1 is narrower and faster. Think of 4.5 as the senior engineer you consult on architecture, and Build as the tireless mid-level who ships forty small PRs a day without complaint.

In practice the split looks like this: Build wins on speed and cost for iterative agent loops — refactors, test writing, bug reproduction, tool-driven workflows where latency per step compounds. Grok 4.5 wins when the problem needs deep reasoning across domains: a performance bug that is actually a data-modeling problem, or code review that requires understanding the business context. Both accept images, so either can read a UI mockup or an error screenshot; Build is specifically trained to fold those into its coding workflow.

What Should You Actually Use Grok Build 0.1 For?

Our recommendation, having watched the agentic-coding category fill up fast this year: use Build 0.1 as a loop model, not a chat model. Its sweet spots:

Repository-scale refactors. The 256K window holds an entire mid-sized codebase in memory at once, so it can rename, restructure, and update call sites without losing track of file 47. Screenshot-driven fixes. Paste a broken UI or a stack-trace screenshot; the vision input means no transcribing errors by hand. Structured tool pipelines. It reliably emits structured output and tool calls, which makes it a good engine for CI bots and automated triage. Fast interactive sessions. Latency is the point — xAI bills it as their fastest coding model, and in an agent loop that runs 300 steps, per-step speed is the whole user experience.

Where we would skip it: long-form technical writing, architecture debate, and anything where general world knowledge dominates. That is Grok 4.5 or a frontier flagship's territory — and if you are curious where xAI's multi-agent experiments are heading next, our piece on the Grok 4.20 multi-agent beta maps the roadmap.

How Do You Try Grok Build Without an API Key?

xAI's own access paths assume you are a developer: API keys, IDE plugins, subscriber-gated integrations. The friction-free route is CoreAI, where the model is live alongside Grok 4.5 and 300+ other models on iOS, Android, and the web — one subscription, plans from $57/month, no per-token billing to monitor.

The test we would actually run: open Compare, give Build 0.1 and KAT-Coder-Pro V2.5 the same real bug from your tracker, and watch how each plans the fix. Then flip on thinking mode and try a harder one. Ten minutes of side-by-side output on your own code beats any benchmark chart, and the free AI Code Explainer is a handy scratchpad for dissecting whatever either model produces.

Frequently Asked Questions

What is Grok Build 0.1 best at?

Fast, iterative agentic coding: repository-scale refactors, tool-driven workflows, test generation, and screenshot-driven debugging. It is trained to run in continuous loops until a task completes, rather than to answer one-off questions, and xAI positions it as their fastest coding model.

How much does Grok Build 0.1 cost?

$1.00 per million input tokens and $2.00 per million output tokens, with cached input at $0.20 per million. Above 200,000 prompt tokens, rates double to $2.00/$4.00. On CoreAI it is included as a standard-tier model under one flat subscription.

Is Grok Build 0.1 better than Grok 4.5 for coding?

For fast agentic loops and cost-sensitive volume work, usually yes — it is cheaper, faster, and purpose-trained for tool use. For problems needing deep cross-domain reasoning or the largest context (Grok 4.5 offers 500K tokens), the generalist still wins. Many teams run both: Build as the workhorse, 4.5 as the escalation.

Does Build 0.1 accept image input?

Yes. It accepts text and image inputs, so it can read diagrams, UI mockups, and error screenshots as part of its workflow — genuinely useful when the bug report is a picture of a broken layout rather than a tidy stack trace.

Where can I use Grok Build 0.1 without writing code?

On CoreAI's model library, across iOS, Android, and the web. No API key or IDE setup required, and you can benchmark it against KAT-Coder, Kimi, Claude, and 300+ other models with your own prompts.