What is Grok 4.3?
Grok 4.3 is xAI’s proprietary model for cost-efficient reasoning, tool calling and large-context applications. It was released 2026. This guide separates documented specifications from vendor benchmark claims and gives teams a practical way to decide whether the model belongs in a real evaluation.
QUICK VERDICT: Grok 4.3 is a strong value baseline with a million-token window. New xAI evaluations should also include Grok 4.6 for higher capability.
Field | Verified value |
|---|---|
Provider | xAI |
Release date | 2026 |
Availability | Available |
License | Proprietary |
Context window | 1 million tokens |
Maximum output | No separate maximum published on the model card |
Modalities | Text and image input; text output |
API pricing | $1.25 input and $2.50 output per million tokens |
Access | xAI API, Amazon Bedrock and selected integrations |
Best fit | cost-efficient reasoning, tool calling and large-context applications |
Last verified | September 2, 2026 |
What changed with Grok 4.3
Grok 4.3 should not be evaluated as a name change. The important differences are the model’s reasoning controls, tool behavior, context policy, access route and economic profile. Those details determine whether a benchmark result transfers to production.
Area | What changed or matters |
|---|---|
Context | One-million-token window |
Reasoning | None, low, medium and high effort |
Price | $1.25 input and $2.50 output |
Reliability | xAI emphasizes instruction following and low hallucination |
The correct comparison baseline is Grok 4.1 family. Teams planning a new deployment should also include Grok 4.6 where access allows. Testing only the newest model or only the incumbent hides the migration cost, output-style changes and tool-use regressions that often matter more than a small benchmark gap.
Grok 4.3 capabilities
The clearest fit is cost-efficient reasoning, tool calling and large-context applications. That does not mean every task in those categories should use the model. A production system combines the base model with prompts, retrieval, tools, permissions, memory, retry logic and human review. The model card describes only one layer of that system.
Capability | Practical implication |
|---|---|
Long context | 1 million tokens. Test retrieval accuracy at realistic lengths rather than assuming every token receives equal attention. |
Output capacity | No separate maximum published on the model card. Long output is useful only when the verification process can keep up. |
Modalities | Text and image input; text output. Confirm format-specific accuracy with your own files. |
Agent use | Use explicit tool schemas, narrow permissions, approval gates and recoverable operations. |
Reasoning | Record the exact effort level because cost, latency and quality can change materially. |
For coding, evaluate repository navigation, test creation, regression rate, review burden and recovery after a failed tool call. For research, measure citation correctness, source coverage and whether the model distinguishes evidence from inference. For computer or browser use, record every unsafe click, wrong field, lost state and unapproved action.
Benchmarks and evidence
The evidence below comes from xAI or named launch partners. It is useful for identifying intended strengths, but it is not equivalent to an independent head-to-head test. Prompts, tools, reasoning budgets, sampling, infrastructure and scoring rules can differ.
Evidence | Reported result | How to interpret it |
|---|---|---|
Hallucination | xAI reports its lowest frontier-model rate | Vendor evaluation |
Tool use | Model card highlights strong tool calling | Product capability |
Cloud access | Available through Amazon Bedrock | Distribution fact |
Treat benchmark results as a shortlist signal. Before purchasing or migrating, reproduce representative work under one frozen protocol. Keep model snapshots, reasoning effort, tool access and token budgets constant. Report repeated-run pass rates and total cost per accepted result, not a single best attempt.
Pricing, access and deployment
xAI API, Amazon Bedrock and selected integrations. The current pricing reference is $1.25 input and $2.50 output per million tokens. Provider pricing changes frequently and can include cache rates, batch discounts, regional premiums, long-context multipliers, priority processing and tool-call fees. Recheck the official pricing page before budgeting.
Cost driver | What to measure |
|---|---|
Input tokens | Prompt, retrieved context, tool results and repeated history |
Output tokens | Visible answer plus any billable reasoning or generated artifacts |
Caching | Eligible repeated prefixes, cache-read price and expiration policy |
Tools | Search, computer use, code execution and third-party API fees |
Retries | Failed runs, verifier loops and human rework |
Success-adjusted cost | Total spend divided by deliverables that pass review |
A cheaper token price can lose to a more expensive model if it takes more steps, retries more often or produces work that needs heavy correction. Conversely, a frontier model can be wasteful when a smaller model already passes the task rubric. Route by measured task difficulty rather than brand prestige.
Grok 4.3 limitations
- Newer Grok models are available.
- Vendor hallucination claims need independent testing.
- Tool access raises action risk.
- No separate public output cap.
- Partner platforms can expose different features.
High-stakes medical, legal, financial, security and scientific work requires qualified review. Store the exact model identifier, prompt version, tools, source documents and approvals for each consequential run. Build a rollback path before granting write access to repositories, browsers, databases or cloud infrastructure.
Risk | Minimum control |
|---|---|
Hallucination | Require source checks or executable tests |
Prompt injection | Separate untrusted content from instructions and restrict tools |
Over-permission | Use least privilege and approval gates |
Silent model change | Pin snapshots where possible and run regression tests |
Data exposure | Review retention, regional processing and provider terms |
Runaway cost | Set token, time, tool-call and retry budgets |
How to evaluate Grok 4.3
Create 20 to 50 tasks from real work. Freeze the tasks and rubric before testing. Include easy tasks, normal tasks, edge cases and adversarial inputs. Give each model equivalent tools and enough budget to finish, but cap time and retries. Repeat non-deterministic runs so one lucky result does not decide the winner.
Test area | Record |
|---|---|
Task completion | Pass or fail plus rubric score |
Reliability | Repeated-run success and variance |
Quality | Factuality, instruction adherence and usefulness |
Tool use | Wrong calls, retries, recovery and permission errors |
Efficiency | Wall time, tokens, cache use, tool fees and human review |
Safety | Unsafe actions, injection response and sensitive-data handling |
Migration | Prompt changes, integration work and output-style regressions |
Compare Grok 4.3 with Grok 4.1 family and Grok 4.6. Choose the least expensive configuration that meets the acceptance threshold with an adequate safety margin. Re-run the suite after any model snapshot, system prompt, retrieval or tool change.
Frequently asked questions
Is Grok 4.3 available now?
Available. The documented access routes are xAI API, Amazon Bedrock and selected integrations. Availability can differ by region, plan and partner platform.
Is Grok 4.3 open source?
No. Grok 4.3 is proprietary. Access is controlled by xAI and supported distribution partners.
How much does Grok 4.3 cost?
$1.25 input and $2.50 output per million tokens. Budget with measured end-to-end workloads because token rates alone omit retries, tools, caching, long-context multipliers and review time.
What is Grok 4.3 best used for?
Its strongest documented fit is cost-efficient reasoning, tool calling and large-context applications. Start with a supervised pilot and keep human sign-off for consequential work.
Should I migrate from Grok 4.1 family?
Only after a side-by-side evaluation. Measure pass rate, total cost, latency, output style, tool reliability and the engineering work required to migrate. A newer model is not automatically the better operational choice.
Related model guides
Start with the broader Best AI Models directory.
Compare with the Grok 4.6 guide.
Official sources and update policy
Checked September 2, 2026. We update this guide when the provider changes the model specification, pricing, access, licensing or safety documentation. Vendor benchmarks are attributed and are not presented as independent testing. No vendor payment or affiliate relationship determined inclusion.