Surprise: Grok 4.3 joins Amazon Bedrock, but only in AWS GovCloud!

Hi everyone, it's Shii! Today I found some news about a new model joining Amazon Bedrock, so let me tell you about it right away!

AWS What's New aws.amazon.com

What was announced?

According to AWS's What's New page, xAI's "Grok 4.3" model is now available on Amazon Bedrock. The key point here, though, is that this is only for the AWS GovCloud (US-West) region. With this, xAI becomes one of the model providers available on Bedrock in AWS GovCloud (US-West).

This isn't a rollout across the general commercial AWS regions — it's specifically for GovCloud, which serves government agencies and regulated industries, so don't read it as a broader release.

Why it matters

AWS GovCloud is a special region used by US government agencies and customers in heavily regulated industries like defense and finance. Because of its strict security and compliance requirements, the latest AI models often arrive there later than they do in commercial regions.

Against that backdrop, having a cutting-edge model like Grok 4.3, which is said to excel at reasoning and agentic workloads, become available in GovCloud too is great news for engineers building generative AI applications in regulated industries and government agencies — it gives them one more option to choose from.

What changes

Grok 4.3 is described as a "reasoning-first" model, meaning it's designed around reasoning. According to the source, you can adjust its reasoning effort to match your use case, choosing from four levels.

• none (no reasoning)
• low
• medium
• high (heavy reasoning)

On top of that, it's highlighted for strong tool use and instruction-following, which suits it for building agents, as well as token efficiency that keeps high-volume inference cost-effective.

The source article mentions the following use cases it's well suited for.

• Customer support
• Web development
• Case law research
• Financial document Q&A

AWS also says it delivers consistent, high-quality results across a wide range of workloads, including conversational AI, search, chat, and multi-turn interactions.

Dive Deep

Grok 4.3 runs on "Mantle," a new inference engine on Bedrock. Mantle is designed with price-performance in mind, and it supports the following features.

• Tool calling
• Structured output
• Response streaming

The source article doesn't give specific pricing figures, but for region availability, it points to the Grok 4.3 region availability documentation for the latest list. To get started, the documented path is through the Grok 4.3 model detail page.

Keep in mind this article is specifically about the rollout in AWS GovCloud (US-West) — the source doesn't say anything about availability in other commercial regions, so if you're curious, check the region list page directly.

Wrap-up

Today I covered the news that xAI's Grok 4.3 is now available on Amazon Bedrock in AWS GovCloud (US-West). Here's a recap of the key points.

• Available only in AWS GovCloud (US-West)
• Reasoning effort adjustable across four levels: none / low / medium / high
• Strong tool use and instruction-following, well suited for building agents
• Runs on the new Mantle inference engine, with support for tool calling, structured output, and streaming
• Well suited for use cases like customer support, web development, case law research, and financial document Q&A

For engineers at government agencies and regulated industries using GovCloud, this is a nice update that adds one more model to choose from!