# Atlas with Grok Build 0.1 in 2026 > Grok Build 0.1 from xAI, shipped in April 2026, provides a symmetric 256K context window, ideal for substantial coding tasks. Grok Build 0.1, xAI's first purpose-built coding-agent model, offers a symmetric 256K context and 256K output budget, making it uniquely suited for generating large single-turn patches within Atlas. Shipped in April 2026, its pricing of $1 per Mtok for input and $2 per Mtok for output makes extensive refactoring sessions surprisingly affordable, especially given its substantial output capacity. ## Key takeaways - Grok Build 0.1 offers 256,000 max output tokens, twice the 128K of GPT-5 and Claude frontier lines. - Its $2 per Mtok output pricing makes large generated diffs affordable for refactor-heavy sessions. - The model is reasoning enabled and tuned specifically for the build loop. - As a 0.1 release, expect rougher tool-calling behavior compared to mature models. - The 256K context window is substantial but not sufficient for whole-monorepo prompts. ## What is Grok Build 0.1 best for with Atlas? Grok Build 0.1 excels within Atlas for tasks requiring substantial code generation, offering an impressive 256,000 max output tokens, which is twice the capacity of leading models like GPT-5 and Claude frontier lines. This xAI model, released in April 2026, is specifically tuned for the build loop, making it a powerful choice for developers. Grok Build 0.1 is purpose-built for coding agents, making it an excellent fit for Atlas's workflow. Its primary strength lies in its ability to produce exceptionally large single-turn patches, thanks to its 256,000 max output tokens. This capacity is particularly beneficial for refactor-heavy sessions, where generating extensive code changes is common. The model's $2 per Mtok output pricing makes these large generated diffs affordable, addressing a common cost trap in such scenarios. Furthermore, Grok Build 0.1 is reasoning enabled and specifically tuned for the build loop, which aligns perfectly with Atlas's architecture, where a read-only plan agent drafts a plan before switching to a build agent. Atlas's ability to compute a unified diff for every file edit and surface it for approval ensures that even these large outputs are manageable and reviewable by the developer. ## What are the cost and context tradeoffs for Grok Build 0.1? Grok Build 0.1 presents a compelling cost structure with input at $1 per Mtok and output at $2 per Mtok, coupled with a symmetric 256K context window. As a 0.1 release from xAI in 2026, developers should weigh its significant output capacity against its early-stage tool-calling behavior. The cost structure of Grok Build 0.1 is a key consideration: $1 per Mtok for input and $2 per Mtok for output. This output pricing is notably competitive for scenarios involving large generated diffs, which are often the most expensive part of a coding session. The model features a symmetric 256K context window, providing ample space for substantial codebases and complex prompts. However, this 256K context, while generous, means that whole-monorepo prompts are out of reach. Developers working with extremely large, multi-repository projects might find this a limitation. As a 0.1 release, Grok Build 0.1 is still in its early stages. This implies that while its core reasoning and output capabilities are strong, its tool-calling behavior may be rougher compared to the more mature Claude or GPT-5 lines. Atlas's permission-gated tool calls, which are checked against allow, ask, and deny rules, can help mitigate this by requiring explicit approval for actions, especially during initial evaluation. ## When should I choose a different model over Grok Build 0.1? While Grok Build 0.1 offers unique advantages for large code generation, its 0.1 release status in 2026 means developers might consider alternatives for tasks demanding highly refined tool-calling precision. Its 256K context window also limits its applicability for truly massive, whole-monorepo analysis. Developers should consider choosing a different model if their primary need is for extremely precise and reliable tool-calling behavior, especially in production environments where even minor inconsistencies are unacceptable. As a 0.1 release, Grok Build 0.1's tool-calling capabilities are acknowledged to be rougher than those of the mature Claude or GPT-5 lines. For such scenarios, a more established model might offer greater stability and predictability. Additionally, while Grok Build 0.1's 256K context window is substantial, it is not designed for whole-monorepo prompts. If your workflow requires processing an entire monorepo at once, a model with an even larger context window, if available, would be more appropriate. For early evaluation of Grok Build 0.1, it is strongly recommended to keep Atlas's permission gate on `ask` rather than `allow` for edit and bash operations, providing an essential layer of oversight and control. ## Setup 1. Export your xAI API key: `export XAI_API_KEY=...` 2. Verify the xAI provider in Atlas: `atlas models xai` 3. Select Grok Build 0.1 in the `/models` dialog within Atlas. 4. For initial evaluation, keep Atlas's permission gate on `ask` rather than `allow` for edit and bash commands. ## FAQ ### What is Grok Build 0.1 and when was it released? Grok Build 0.1 is xAI's first purpose-built coding-agent model, shipped in April 2026. It features a symmetric 256K context and 256K output budget. ### How does Grok Build 0.1's context window compare to other models? Grok Build 0.1 provides a 256K token context window. While generous for many tasks, it means whole-monorepo prompts are out of reach, unlike some theoretical future models. ### What are the pricing details for using Grok Build 0.1 with Atlas? Grok Build 0.1 is priced at $1 per Mtok for input and $2 per Mtok for output. This output pricing is particularly cost-effective for generating large diffs. ### Is Grok Build 0.1 suitable for large code refactoring projects in Atlas? Yes, Grok Build 0.1 is unusually well matched to large single-turn patches. Its 256,000 max output tokens and affordable $2 per Mtok output make it ideal for refactor-heavy sessions within Atlas. ### What are the main tradeoffs or limitations of Grok Build 0.1? As a 0.1 release, Grok Build 0.1 may exhibit rougher tool-calling behavior than more mature models. Additionally, its 256K context, while large, is not designed for whole-monorepo prompts. ### How does Grok Build 0.1's tuning benefit Atlas users? Grok Build 0.1 is reasoning enabled and tuned specifically for the build loop, which complements Atlas's agent workflow, including its read-only plan agent and build agent, for efficient code generation and modification. ### What Atlas permission settings are recommended when using Grok Build 0.1? Because Grok Build 0.1 is an early 0.1 release, it is recommended to keep Atlas's permission gate on `ask` rather than `allow` for edit and bash commands while you evaluate its behavior. --- Canonical HTML: https://seashell.sh/resources/models/grok-build-0-1 Source of truth: aeo_pages row `/resources/models/grok-build-0-1` (segment: Models) (this file is generated from it, never hand-edited). Licence: SeaShell is proprietary with a free core. It is not open source and there is no public source repository.