Grok 4 Fast Reasoning
Grok 4 Fast Reasoning is a legacy integration reference; evaluate Grok 4.3 before starting new work.
Use it for
- Teams maintaining an existing integration
- Workloads that can use a 2m context window
- Buyers comparing 1 tracked provider route
Do not use it for
- New production launches
- Strict JSON or tool-calling flows
- Family
- Grok 4
- Released
- 2025-09-01
- Context
- 2m
- Architecture
- Decoder Only
- Specialization
- general
- Openness
- Proprietary
- License
- ProprietaryCommercial use: conditional
- Weights
- Not released
- Code
- Unknown
- Training
- Pretrained
Cheapest of 2 routes · Microsoft Foundry
This model is deprecated. xAI recommends switching to Grok 4.3.
About
Grok 4 Fast Reasoning is a September 2025 xAI model retiring on 2026-05-15; use Grok 4.3 for current API work.
Top use-case fit
Long context
Included by capability and metadata signals in the decision map.
Vision
Included by capability and metadata signals in the decision map.
Provider price ladder
Compare all 2Compare API pricing across 1 providers for input and output tokens, batch, and cached reads when available.
| Provider | Input / 1M | Output / 1M | Route |
|---|---|---|---|
| Microsoft Foundry | - | - | ServerlessProvisionedPartial |
Available via routers & gateways(6)
LiteLLM
GatewayOpen-source Python SDK and proxy server that unifies 100+ LLM APIs behind a single OpenAI-compatible interface, with load balancing, cost tracking, and configurable failover.
OpenRouter
HybridUnified hybrid gateway to 400+ models from 60+ providers via a single OpenAI-compatible API, with optional auto-routing that selects the best model per prompt.
Portkey
GatewayProduction AI gateway routing to 1,600+ LLMs with failover, load balancing, semantic caching, and guardrails; Apache 2.0 core is fully self-hostable with the complete feature set.
Azure AI Foundry Model Router
RouterMicrosoft Azure AI Foundry's native model router that uses a trained ML model to route each prompt in real time to the optimal Azure-hosted model, with Balanced/Cost/Quality mode selection and automatic failover.
Helicone
GatewayObservability-first AI gateway with routing, caching, rate limiting, and request tracing; Apache 2.0 open-source core with a managed hosted tier for logging and analytics.
Kong AI Gateway
GatewayMulti-LLM AI gateway built on Kong Gateway 3.x, adding semantic routing, load balancing, guardrails, and MCP traffic analytics as plugins over Kong's existing API management platform.
Capabilities
Benchmark peer barsfor Long context
No task-mapped benchmark peers are available for this model yet.
Migration checks
No linked migration route is available for this model yet.
Compare Grok 4 Fast Reasoning with other models
Comparison and alternatives
Browse all comparisons →Cheapest of 2 routes · Microsoft Foundry