Model limit probe

xAI: Grok 4.1 Fast | context window limit

xAI: Grok 4.1 Fast context window limit decides whether a key can enter a production route. TestKey reads model ID x-ai/grok-4.1-fast, provider xAI, catalog context, real-key headers, 429 errors, and region signals together.

Model

x-ai/grok-4.1-fast

xAI: Grok 4.1 Fast

Provider

xAI

10 models in catalog

Limit dimension

context window limit

context-window

Visible signal

catalog visible

Context window: 2,000,000

Limit matrix summary

Model

x-ai/grok-4.1-fast

Limit dimension

context-window

Visible signal

catalog visible

Read-only check. Detection data burns after 5 minutes.

Why this limit matters

xAI: Grok 4.1 Fast context window limit decides whether a key can enter a production route. TestKey reads model ID x-ai/grok-4.1-fast, provider xAI, catalog context, real-key headers, 429 errors, and region signals together.

Model: x-ai/grok-4.1-fast
Provider: xAI
Limit dimension: context window limit

How to prove it

Read-only check. Detection data burns after 5 minutes.

Start with the visible signal: catalog visible, then read headers and error bodies with read-only requests.
context window limit must bind model ID x-ai/grok-4.1-fast; limits from another model at the same provider cannot be reused.
context window limit · catalog visible · 2,000,000

Operator action

xAI: Grok 4.1 Fast context window limit is not just a number. It should become route throttling, sale tags, headroom alerts, fallback model suggestions, and price protection.

Read-only check. Detection data burns after 5 minutes.
Visible signal: catalog visible
Context window: 2,000,000

Open key checker

Read-only check. Detection data burns after 5 minutes.