Grok

Grok 4 Fast Reasoning

xAIToken-based
Alias:grok-4-fast-reasoning
Create API Key

Compare grok-4-fast-reasoning API pricing, supported endpoints, capabilities and access options on Modelsell.

text
Starting price
Input / Output · 1M
Context
—
Maximum input window
Modalities
→

Pricing by Supplier

xAI
-40%
xAI 官方
Input$0.2$0.12/ 1M
Output$0.5$0.3/ 1M
Cache Read$0.05$0.03/ 1M

Capabilities / Supported modalities

StreamingSystem promptFunction callingToolsJSON modeStructured outputPrompt cachingReasoning
Input
Output

Provider & data privacy

Provider
xAIDocs
Tokenizer
Grok tokenizer (BPE)
License
Proprietary (commercial)Proprietary
Data retention48 daysNot used for upstream training by default

Performance

Benchmarks

Scores on standardized evaluations. Higher percentages are better — and rank percentile shows

Metrics sourced fromArtificial Analysis 2026-09-30·Grok 4 Fast Reasoning

This model is not included in the current benchmark snapshot.

Missing models or measurements are not zero scores.

Benchmark charts preserve the source model selection and reasoning settings. Missing models or measurements are not zero scores, and benchmark cost or speed is not this site’s service commitment.

About Grok 4 Fast Reasoning

从现象追到可以验证的解释

Grok 4 Fast Reasoning 适合处理需要拆解条件、比较假设和检查结果的文字任务。它可以分析数据变化、推导计算步骤、设计算法,也可以把较长材料中的不同线索放在一起判断。适合已经有明确问题,希望得到推导过程与验证方法的使用者。

例如运营报表中的转化率下降,可以把分组数据、统计口径和同期变动一起提供,让模型先检查分母是否一致,再区分流量结构变化与各组表现变化。模型可以提出解释和后续检查,但是否成立仍应由原始数据验证,不能仅凭相关变化确定原因。

让计算与代码参与检查

接入代码执行工具后,可以让它通过程序复核加总、比例和样本分组;接入检索工具后,可以补充问题需要的外部资料。工具需要应用实际提供,计算结果应来自执行输出。没有工具时,也可以要求给出公式或脚本,在自己的环境中运行后把结果反馈回来。

长材料怎样组织更有效?

保留必要背景,同时说明本轮只解决哪个问题。给数据表、文档和日志加上编号,要求结论对应具体材料;需要连续分析时,把已经确认的口径写入上下文,避免后续使用另一套定义。

对于开放问题,可以要求先列出可能解释,再给出能区分它们的检验。对于有标准答案的任务,则明确验收条件,并让模型检查反例和边界情况。这样得到的结果更方便验证,也更容易继续追问。

xAI 官方 API 已将此历史名称重定向至 Grok 4.3。

Use cases and prompting

可以用分组转化数据提问:

“下面是两周按渠道划分的访问量与订单量。请先计算整体和各渠道转化率,检查整体下降是否可能由渠道占比变化造成。列出公式、计算结果和还需要的数据,不要直接把同期活动认定为原因。数据:{表格}。”

先确认访问与订单的统计时间、去重方式及归因口径。若有代码执行工具,让模型运行计算并保留输出;否则在本地执行它给出的脚本。确认数值正确后,再让它设计下一轮验证,区分数据异常、流量变化和实际效果变化。

API access

API documentation

Code samples

RequestPOST/v1/chat/completions
Example request
Parameters
ParameterTypeDefault / rangeDescription
reasoning_effort
enum
=medium
Controls how much the model thinks before answering
max_completion_tokens
integer>= 1Maximum tokens including hidden reasoning tokens
stop
array—Up to 4 strings that stop generation
seed
integer—Deterministic sampling seed (best-effort)
stream
boolean
=false
Stream tokens via Server-Sent Events
response_format
object—Force JSON object or schema-conforming output
tools
array—Tool / function declarations the model may call
tool_choice
string
autononerequired
Tool-choice policy or specific tool name
user
string—End-user identifier for abuse monitoring

Replace <YOUR_API_KEY> with the API key from your token settings.

Authentication

All requests must include Authorization: Bearer <TOKEN> header. Anthropic-formatted endpoints accept the x-api-key header instead.

Generate tokens from the Tokens page; you can scope them to specific models, groups, IPs, and rate-limits.

Supported parameters

Generation parameters
ParameterTypeDefault / rangeDescription
reasoning_effort
enum
=medium
Controls how much the model thinks before answering
max_completion_tokens
integer>= 1Maximum tokens including hidden reasoning tokens
stop
array—Up to 4 strings that stop generation
seed
integer—Deterministic sampling seed (best-effort)
stream
boolean
=false
Stream tokens via Server-Sent Events
response_format
object—Force JSON object or schema-conforming output
tools
array—Tool / function declarations the model may call
tool_choice
string
autononerequired
Tool-choice policy or specific tool name
user
string—End-user identifier for abuse monitoring

Rate limits

SupplierRPMTPMRPD
xAIUnlimitedUnlimitedUnlimited

No restriction

Frequently asked questions about grok-4-fast-reasoning

What is grok-4-fast-reasoning?

Compare grok-4-fast-reasoning API pricing, supported endpoints, capabilities and access options on Modelsell.

How do I call grok-4-fast-reasoning?

Create an API key with access to grok-4-fast-reasoning, then use the exact model ID and a supported endpoint from the API access section. Request fields depend on the selected endpoint.

How is grok-4-fast-reasoning priced?

Pricing depends on the selected provider group and the model billing unit. The current input, output, request, or media prices are shown on this page before sign-up.

How should I evaluate grok-4-fast-reasoning for my project?

Start with the use cases and prompting guidance on this page, then evaluate the model with representative inputs from your project.