Grok 4.5: xAI's New Opus-Class Coding Model — Now on Kunya

xAI just shipped its most capable model yet, and it's now live on Kunya AI as the default xAI chat model. Grok 4.5 is purpose-built for the work that actually matters to engineers — writing code, running autonomous agents, and solving complex reasoning problems at scale. Here's everything you need to know about what it is, how it performs, and why it replaces Grok 4.3 as the go-to xAI model on the platform.

Accessing Grok 4.5 directly through xAI means committing to one vendor. On Kunya AI, it's one model in a frontier stack — you get Grok 4.5 for deep coding and agentic tasks, Claude Sonnet 5 for nuanced writing, Gemini 2.5 Pro for research, and 100+ others, with no lock-in, no separate API keys, and no switching cost. The best model for each task, always within reach.

What Is Grok 4.5?

Grok 4.5 is xAI's latest flagship model — described by Elon Musk as "an Opus-class model, but faster, more token-efficient and lower cost." That framing is deliberate. Anthropic's Claude Opus 4 sits at the top of many engineering leaderboards. xAI is positioning Grok 4.5 as a direct competitor — one that delivers comparable intelligence without the cost overhead.

What makes this release notable is the training partnership. Grok 4.5 was co-trained with Cursor, the AI-native code editor trusted by hundreds of thousands of developers. That collaboration means the model isn't just good at generating code in isolation — it's been optimized for real-world software development workflows: navigating large codebases, interpreting context across files, and producing changes that actually integrate with existing systems.

The model targets three core use cases:

• Software engineering — writing, reviewing, debugging, and refactoring code

• Agentic tasks — multi-step autonomous workflows where the model must plan, execute, and recover from errors

• Knowledge work — deep research, technical documentation, and complex reasoning chains

If your work lives in terminals, editors, and codebases, Grok 4.5 was built with you in mind.

Grok 4.5 Benchmarks: What the Numbers Actually Say

xAI released a full set of benchmark results with the launch. Let's go through them without spin.

Where Grok 4.5 Leads

On the benchmarks that test real-world software engineering capability, Grok 4.5 puts up strong numbers:

• DeepSWE 1.0: 62.0%

• Terminal Bench 2.1: 83.3%

• SWE Bench Pro: 64.7%

• SWE Marathon pass@1: 29.0% — beating Claude Opus 4 at 4.8%

• Coding Baseline: 96.0%

The SWE Marathon result is particularly significant. At 29.0% pass@1, Grok 4.5 outperforms Opus 4.8 by a wide margin on this benchmark, which evaluates a model's ability to complete software engineering tasks from start to finish without hints or retries. That's a real signal — not a cherry-picked number.

The 2x greater token efficiency claim is also meaningful in practice. If you're running thousands of API calls a month or building agents that process large documents and codebases, cutting token consumption in half has a direct impact on your infrastructure costs.

Where Grok 4.5 Trails

Honesty matters here. On certain benchmarks, Grok 4.5 does not lead the field. Models like GPT-5.5 and Fable outperform Grok 4.5 in areas tied to general language understanding and creative reasoning. If your workflow leans heavily on those capabilities, those differences are worth knowing.

But for developers and engineering teams? The benchmarks that matter most — code completion accuracy, multi-step agentic task resolution, long-context reasoning — are exactly where Grok 4.5 is built to compete. The best AI models for coding are increasingly specialized, and Grok 4.5 reflects that direction.

What Changed From Grok 4.3

Grok 4.3 remains available on Kunya, but Grok 4.5 is now the default xAI model on the platform. Here's what's materially different:

Reasoning Upgrades

Grok 4.5 ships with configurable reasoning effort. You can set it to low, medium, or high depending on the complexity of your task. Low is fast and cheap — good for simple completions. High pulls out the full reasoning chain for complex debugging, architecture decisions, or multi-file code reviews. This is a practical control that engineering teams will actually use.

Context Window

The context window jumps to 1 million tokens. That's large enough to load entire codebases, full documentation sets, or extended conversation histories without truncation. For agentic workflows that need persistent memory across long sessions, this is a meaningful upgrade over Grok 4.3.

Pricing

Grok 4.5 is priced at $2 per million input tokens and $6 per million output tokens. For a model at this capability tier, that pricing is competitive — especially combined with the 2x token efficiency improvement. You're getting more output per dollar than most comparable Opus-class models.

Default Status on Kunya

Previously, Grok 4.3 was the default xAI model when you opened a new chat on Kunya. That's now changed. Grok 4.5 takes that slot. Grok 4.3 is still available if you prefer its speed and efficiency for simpler, general-purpose tasks — but for engineering work, the default is now the stronger model.

Who Should Use Grok 4.5?

💻 Grok 4.5 in Practice — A Real Coding Scenario

Here's the kind of task where Grok 4.5 earns its keep. You're mid-sprint, you have a broken async pipeline in a TypeScript monorepo, and you need it diagnosed and fixed without losing your train of thought.

Prompt

My Express API is returning 500 on all POST requests after I wrapped my DB calls in a transaction. The error is "Cannot acquire connection — timeout after 5000ms". I'm using Knex with PostgreSQL. What's wrong and how do I fix it?

Grok 4.5 Response

Classic connection pool exhaustion — you're opening a transaction but not releasing it on error paths. Make sure every transaction has a try/catch that calls trx.rollback(), and confirm your pool size in knexfile.js is sized correctly for concurrent requests. Here's the corrected pattern…

Grok 4.5's 1M token context window means you can paste your entire monorepo's relevant files and get precise, context-aware answers — not generic advice.

Not every model is the right tool for every job. Grok 4.5 has a clear target audience:

Built For

• Software developers working on real codebases — not toy examples, but production systems with dependencies, edge cases, and context spread across multiple files

• Engineering teams using AI to accelerate code review, refactoring, and technical documentation

• AI agent builders who need a model that can plan, execute multi-step tasks, and handle errors gracefully without constant human intervention

• Technical researchers who need to process large volumes of source material and synthesize precise, structured outputs

When to Use Grok 4.3 Instead

Grok 4.5 is not the right choice for every conversation. If you're running quick general-purpose queries — summarizing an article, drafting a casual email, answering a trivia question — Grok 4.3 is faster and more cost-efficient for those tasks. Match the model to the job. On Kunya, switching between models takes one click. You're never locked into the default.

For a broader look at how different models stack up across use cases, see our guide on how to choose the right AI model for your workflow.

How to Use Grok 4.5 on Kunya AI

Kunya AI gives you access to 100+ frontier models — including Grok 4.5 — under a single subscription. No xAI API key. No separate account. No configuration. You open a chat, and Grok 4.5 is already the default xAI model, ready to go.

But here's what actually matters: Grok 4.5 on Kunya AI isn't a siloed tool. It's one part of a frontier workflow. Run Grok 4.5 for the heavy coding task it excels at, then switch to Claude Opus for long-form reasoning, or GPT-5 for a different output style — all inside the same platform, same subscription, zero API juggling. That's top-of-market routing: you pick the best model for each task instead of being stuck with whatever one vendor decided to ship this quarter.

Here's how it works in practice:

• Grok 4.5 is available immediately for all Kunya AI subscribers — no extra steps

• Switch to GPT-5, Claude Opus 4, Gemini 2.5, or 100+ others from the same interface mid-workflow

• Use the reasoning effort toggle (low / medium / high) to control response depth and cost per task

• Access the full 1M token context window for large codebase or document analysis

• Compare outputs side-by-side across models without leaving the platform

The model that's best for your coding sprint isn't always the best for your next task. Kunya AI is built around that reality. As new frontier models drop — like Grok 4.5 — they appear on the platform automatically, no reconfiguration required on your end.

Learn more about how Kunya AI's multi-model access works and why teams are consolidating their entire AI stack in one place.

The Bottom Line on Grok 4.5

Grok 4.5 is the strongest coding and agentic AI model xAI has shipped. The benchmark numbers back it up, particularly on SWE Marathon where it significantly outpaces Opus 4.8. The 1M token context window, configurable reasoning effort, and competitive pricing make it a practical choice for engineering teams, not just a benchmark curiosity.

It's not the universal best model for every task, no single model is. But for software development, autonomous agents, and complex technical work, Grok 4.5 belongs in your toolkit. And on Kunya, it's already there, ready to use alongside every other frontier model available today.

Start your free trial and try Grok 4.5 on Kunya today →

Use Grok 4.5 on Kunya — No Extra Subscription Needed

Grok 4.5 is live on Kunya right now as the default xAI model. One subscription gets you Grok 4.5, Claude Sonnet 5, Gemini Pro, GPT-5, and 95+ other models — side by side, in the same chat window.